EPA/600/R-17/370 | September 2017
www.epa.gov/homeland-security-research
United States
Environmental Protectior
Agency
&EPA
Plastic Scintillation Fibers for
Radiological Contamination Surveys
Office of Research and Development
Homeland Security Research Program
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EPA/600/R-17/370
September 2017
Plastic Scintillation Fibers for
Radiological Contamination Surveys
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Disclaimer
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development's National Homeland Security Research Center, funded and managed this
evaluation. The document was prepared by Lawrence Livermore National Laboratory under
Interagency Agreement (DW-89-92426601). This document was reviewed in accordance with
EPA policy prior to publication. Note that approval for publication does not signify that the
contents necessarily reflect the views of the Agency. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use of a specific product.
Questions concerning this document or its application should be addressed to:
Dr. Sang Don Lee
U.S. Environmental Protection Agency
109 T.W. Alexander Drive
Mail Code: E343-06
Research Triangle Park, NC 27709
Lee.Sangdon@epa.gov
919-541-4531
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Executive Summary
Plastic scintillation fiber (PSF) was developed and initially tested over five decades ago and has
since been used to detect neutrons, x-rays and gamma-rays, track charged particles, and
characterize particle beams in areas ranging from cancer treatment to wide area monitoring.
PSF offers an alternative to traditional gamma-surveying techniques to survey contaminated
surfaces. The advantageous features of PSF include long length, flexibility, the ability to
conform to different shapes, water-/weather-proof application, and relatively inexpensive to
manufacture. When combined with other pre-existing technologies, PSF can be a useful addition
to the survey and remediation toolbox in responding to wide-area radiological contamination.
Specifically, pairing PSF with vehicles to survey, stabilize and mark radioactive surfaces for
subsequent decontamination would be of great benefit to responders. Surveying high-rise
buildings to identify surfaces needing decontamination and to subsequently monitor
decontamination progress would greatly improve the restoration of such buildings. Potential
applications also include deploying arrays of PSF bundles to monitor and survey reservoirs and
subsurface radioactive plumes. Collaboration with Japanese researchers at Japan Atomic Energy
Agency is recommended to leverage PSF technology development and diverse contaminated
surfaces resulting from the deposition of radioactive material from the Fukushima Dai-ichi
Nuclear Power Plant disaster in 2011.
In this study, a prototype radiation detection system has been built employing plastic scintillation
fiber optics. The system incorporates commercial off-the-shelf technology to display a waterfall
plot showing dose rate along the 10-meter long fiber bundle. The main components are the
scintillating fiber, two photomultiplier tubes (PMTs) to detect the scintillation light, a digital
oscilloscope to digitize the PMT signals, a Raspberry Pi computer to perform calculations, and
an Android tablet to display the data and provide a user interface. The parts for the system cost
under $5,000.
The position resolution of the system is 47 centimeters (cm) full-width at half maximum
(FWHM), which allows the determination of point source locations to within a few cm during a
several second integration time. The fiber is sensitive to gamma rays above approximately 150
kiloelectron volts (keV) and to beta-emitting isotopes with end point energies greater than 500
keV. This range covers a large portion of radioisotopes of possible interest for decontamination.
If the bundle were on a boom in front of a vehicle, a speed of 2 miles per hour would allow
surveys with a sensitivity of 10 microrem per hour above typical backgrounds, allowing large
areas to be surveyed quickly. The system has also been tested with the fiber submerged in water,
and performance was maintained, which is potentially of interest for water infrastructure
protection.
IV
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Acronyms
|iCi
microcurie
jiR
microrem
BNC
Bayonet Neill-Concelman
BNCT
Boron neutron capture therapy
CERN
European Organization for Nuclear Research
cm
centimeter(s)
cm3
cubic centimeter(s)
DHS
Department of Homeland Security
DOD
U.S. Department of Defense
DOE
U.S. Department of Energy
EPA
U.S. Environmental Protection Agency
FWHM
Full-width, half-maximum
g
gram(s)
GAO
Government Accountability Office
GIS
Geographic Information System
GPS
Global Positioning System
GSPS
Giga-samples per second
h
hour(s)
HV
High voltage
IND
Improvised nuclear device
JAEA
Japan Atomic Energy Agency
keV
kiloelectron volt(s)
LLNL
Lawrence Livermore National Laboratory
m
meter(s)
m2
square meter(s)
MCA
Multichannel analyzer
MeV
Megaelectron volt(s)
mm
millimeter(s)
mph
mile(s) per hour
inR
millirem
nm
nanometer(s)
ns
nanosecond(s)
N/A
not applicable
NPP
Nuclear power plant
PA
Preamplifier
PMMA
Poly(methyl methacrylate)
PMT
Photomultiplier tube
PSF
Plastic scintillation fiber
PSI
Paul Scherrer Institut
RDD
Radiological dispersal device
SD
Signal divider
SMA
SubMiniature version A
SUV
Sports utility vehicle
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USB Universal Serial Bus
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Table of Contents
Disclaimer iii
Executive Summary iv
Acronyms v
Table of Contents vii
Figures viii
Tables viii
1. Introduction 1
2. Plastic Scintillation Fiber 2
2.1 Plastic Scintillation Fiber Development, Theory and Recent Applications 2
2.2 Radiological Response Survey Technology Applications 7
2.2.1 Application in Transportation and Agriculture Sectors 7
2.2.2 Building Survey and Decontamination Progress Applications 8
2.2.3 Water and Subsurface Applications 9
3. PSF Prototype 11
3.1 PSF Detector Components 12
3.2 PSF Detector Testing and Characterization 17
3.2.1 Attenuation Length 17
3.2.2 Position Resolution 17
3.2.3 Dose Rate Accuracy 20
3.2.4 Minimum Detectable Dose Rate 23
3.2.5 Transportation and Water Infrastructure Applications 24
3.3 Quality Assurance and Quality Control 25
4. Conclusions and Recommendations 26
5. References 28
Appendix A: Prototype PSF Operating Guide 30
A.l Components and System Description 30
A.2 Operation 31
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Figures
Figure 1. Example Mobile Survey Road Vehicles 1
Figure 2. Simplified Schematic of a Position-Dependent PSF Gamma Survey Meter 4
Figure 3. JAEA Application of PSF in Post-Fukushima Surveys (reproduced from JAEA4) 7
Figure 4. An Example Window-Cleaning Platform 9
Figure 5. Schematic Diagram of Five PSF Bundles to Monitor a Subsurface Radioactive Plume
10
Figure 6. Bundle of Seven BCF-12 Scintillation Fibers Glowing from UV Light 13
Figure 7. Image of Hamamatsu 10721 PMT and Subsequent Connection to Seven-Fiber Bundle
13
Figure 8. Image of PSIDRS4 Evaluation Board 14
Figure 9. Image of Raspberry Pi 3 Board 14
Figure 10. Samsung Galaxy Tab S2 Tablet 15
Figure 11. Schematic Diagram of the Prototype PSF Detector Components 15
Figure 12. 7-Fiber Bundle PSF Detector System with Data Acquisition and Tablet Operation .. 16
Figure 13. Fluke model 45 IB Ion Chamber Survey Meter 16
Figure 14. Example Plot Showing Two Sources, Cs-137 and Co-60, Located 50 cm Apart 20
Tables
Table 1. Key Properties of Select PSF Formulations 3
Table 2. Position Resolution Test Matrix for a 10-m Seven-Fiber Bundle 18
Table 3. Position Resolution Test Matrix with Replicates in Parentheses for a 15-m Single Fiber
19
Table 4. Two-Source Resolution Test Matrix with Replicates in Parentheses for a 10-m Seven-
Fiber Bundle 20
Table 5. Dose Rate Accuracy Test Matrix for a 10-m Seven-Fiber Bundle. Dose rates are in
microrem (|ir) per h 22
Table 6. Minimum Detectable Dose Rate Test Matrix with Replicates in Parentheses for 10-m
Seven-Fiber Bundle. Dose rates are in |ir/h 24
Table 7. Minimum Detectable Dose Rate Test Matrix with Replicates in Parentheses for a
Submerged Portion of 10-m Seven-Fiber Bundle in Water 25
Vlll
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1. Introduction
After the detonation of a radiological dispersal device (RDD), improvised nuclear device (IND)
or accidental radiological release from a nuclear facility such as a nuclear power plant (NPP),
radioactive contamination may be di spersed over a wide area. Surveying and characterization of
the radionuclides of interest, their activity and the geographical/topological distribution is vital
for understanding the stabilization and decontamination that may be necessary. Monitoring is
also needed during decontamination to evaluate progress and after decontamination decisions.
Land surveys can be either aerial or ground-based, each approach having pros and cons. Aerial
mapping of the contamination can cover large areas quickly and is not dependent on road/terrain.
However, aerial surveys do not have the same precision in area that ground-based surveys can
provide. Conversely, performance of ground-based surveys can be slow, and ground-based
surveys are limited by access to a given terrain (e.g., road or rail). Land surveys can also be
performed using backpack-style meters. Several U.S. government agencies such as Department
of Energy (DOE), Department of Defense (DOD), Department of Homeland Security (DHS) and
Environmental Protection Agency (EPA) have survey capabilities, including ground-based
detection in cars, trucks and vans, and aerial vehicles such as planes and helicopters. Figure 1
shows examples of ground-based survey vehicles.
Figure 1. Example Mobile Survey Road Vehicles
Note: EPA radiation scanner van (left); Japan Atomic Energy Agency (JAEA) monitoring vehicle (right)
Several stand-off radiation search detectors evaluated by DHS (2013) include the FlexSpec
Mobile (Bubble Technology, Inc., Ontario, Canada; left/right directionality, $260k integrated
with Chevy Tahoe), iFind Compton Camera 442 (FLIR Radiation, Inc., Oak Ridge, TN, USA;
two-plane measurement, truck-/trailer-mounted, $6Q0k to $1.2M), Mobile Radiation Verification
System (Innovative American Technology, Inc., Coconut Creek, FL, LISA; vehicle-mounted or
stand-alone 360-degree horizontal field of view, $175k without vehicle). However, these
technologies specifically do not address mapping contamination on roads or freeway surfaces.
Other portable systems such as Innovative American Technology, Inc.'s Rapid Deployment
Radiation Verification System ($75k), SPIR-Ident Mobile Monitoring System (Mirion
Technologies, Inc., Horseheads, NY, USA; $285k), Gardian Predator Portable Radiation
Detection Kit (Nucsafe, Inc., Oak Ridge, TN, USA; cost unknown), Detective-200 (ORTEC,
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Atlanta, GA, USA; $95k) and Matrix Mobile ARIS (Thermo Fisher Scientific Inc., Durham, NC,
USA; cost unknown) can be deployed on vehicles. However, these portable units require a large
stand-off distance and are typically used for measuring field of view, not performing down-
looking surface measurements. Down-looking measurements would result in a small coverage
area and would require many parallel passes to cover a road or freeway. A vehicle-based
gamma-survey equipment using plastic scintillation fibers (PSFs) with close proximity to road
and freeway surfaces might serve as a rapid survey tool. In this study, a prototype radiation
detection system has been built, employing plastic scintillating fiber optics. The system
incorporates commercial off-the-shelf technology to display a waterfall plot showing dose rate
along the fiber bundle. The main components are the scintillating fiber bundle, two
photomultiplier tubes (PMTs) to detect the scintillation light, a digital oscilloscope to digitize the
PMT signals, a Raspberry Pi computer to perform calculations, and an Android tablet to display
the data and provide a user interface. The parts for the system cost under $5,000.
2. Plastic Scintillation Fiber
2.1 Plastic Scintillation Fiber Development, Theory and Recent Applications
Plastic Scintillation Fibers were developed and initially tested over five decades ago (e.g.,
Reynolds and Condon, 1957; Jopson, Wright and Mark, 1960; and Chupp and Forrest, 1966)
largely to detect neutrons, track charged particles and characterize particle beams.
The theory of PSF is well described in Ruchti (1996), stating that the source term depends on the
nature of the energy deposition, the scintillation material, the material geometry, and the path
length in the material traversed by ionizing radiation. Ruchti cites Berlman (1971) in describing
organic PSF and the process of excitation and transmission. Specifically, the base material
(typically more than 98%) is a polymeric material such as polystyrene or polyvinyltoluene that
absorbs the energy of impinging ionizing radiation, resulting in excitation of the base molecule.
Since relaxation times for such polymers are slow (and, therefore, they are not good light
emitters), organic fluorescent dyes can be added to the base material, and the energy can be
quickly transferred from the polymer to the dye via non-radiative dipole-dipole transfer
occurring on timescales less than 1 nanosecond (ns). The dye fluoresces rapidly on the
nanosecond timescale, and a fraction of the visible light emitted is transmitted along the fiber
itself through total internal reflection to each end of the fiber. Application of cladding with a
different refractive index can prevent light loss outside the angle of total internal reflection.
Further development occurred in the 1980s and 1990s (e.g., Burmeister et al. (1984); Takasaki et
al. (1987); Imai et al. (1991); Oka et al. (1998); and Ishikawa et al. (2002)) to address issues as
diverse as radiotherapy cancer treatment, calorimetry, and wide area radiation monitoring.
PSFs have several key advantageous features, including (Oka et al. (1998); Park and Kim (2004);
Sanada et al. (2015)):
Long length -20 meters (m) (urban area application)
Flexible (durable)
Conform to surface shape (provide improved geometry)
High water resistance (underwater or all-weather applications)
Can be bundled to improve detection
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Serve as both scintillator and light transmitter
No electric power to the sensor portion is needed (less susceptible in harsh environments)
Relatively inexpensive to manufacture
Not influenced by magnetic fields (although PMTs are).
Two current manufacturers of plastic scintillation fiber are Saint Gobain Crystals (multinational
company with Corporate headquarters located in Hiram, Ohio, USA) and Kuraray (Kuraray
group corporate, Tokyo, Japan).
Saint Gobain Crystals1 produces several different fibers (BCF-10, BCF-12 and BCF-20), each of
which varies slightly in emission peak, decay time and attenuation length. The properties of
each formulation are given in Table 1. Additionally, Saint Gobain Crystals PSF materials have
operating temperatures between -20 °C and +50 °C.
Kuraray2 produces three formulations of PSF, namely, SCSF-78 (long attenuation length and
high light yield), SCSF-81 (long attenuation length) and SCSF-3HF 1500 (improved radiation
hardness). Kuraray PSF products are deployed in a range of large international nuclear physics
and particle tracking experiments at the European Organization for Nuclear Research (CERN).
Additional properties of the Kuraray PSF are given in Table 1.
Fibers are also available with fluorinated polymer multilayer cladding with a lower refractive
index to improve light yield by up to 50-60% over conventional single-clad fibers.
Table 1. Key Properties of Select PSF Formulations
Manufacturer
Formulationa'b
Emission
Color
Peak
Wavelength
nm
Decay
Time
ns
Attenuation
Length
m
Application and
Characteristics
Cost
$c
Saint Gobain
Crystals
BCF-10
Blue
432
2.7
2.2
General purpose
102
BCF-12
Blue
435
3.2
2.7
Improved transition
for long lengths
105
BCF-60
Green
530
7
3.5
Radiation hardness
104
Kuraray
SCSF-78
Blue
450
2.8
>4.0
Improved transition
for long lengths,
high light yield
N/A
SCSF-81
Blue
437
2.4
>3.5
Improved transition
for long lengths
N/A
SCSF-3HF
Green
530
7
>4.5
Radiation hardness
N/A
"Common core properties: material = polystyrene, refractive index = 1.6, density = 1.05 grams (g) per cubic
centimeter (cm3).
bCommon cladding properties: material = poly(methyl methacrylate) (PMMA), refractive index = 1.49, density =
1.19 g/cm3.
c Comparable cost for 20 m length, 1 millimeter (mm) round diameter, single clad, non-structure oriented, spool-
supplied fiber. N/A = price not available,
mn = nanometer
1 http://www.crvstals.saint-gobain.com/Scintillating Fiber.aspx (last accessed September 2017)
2 http://kuraravpsf.ip (last accessed September 2017)
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Imai et al. (1991) detail the equations describing the interpretation of photon position from
scintillation pulses observed at either end of a PSF survey system similar to the system shown in
Figure 2.
PMTj
PA
Y photon [L
u.
c/}
PL,
x=0
x=l
pmt2
PA
R
SD
>
MCA
Figure 2. Simplified Schematic of a Position-Dependent PSF Gamma Survey Meter
Legend: PMT = photomultiplier tube. PA = preamplifier. SD = signal divider. MCA = multichannel analyzer.
= fc]/0exp(forPMTi (1)
S2 = k2I0exp (- for PMT2 (2)
where Si and & are the highest of the scintillation pulses received at PMTi and PMT2,
respectively, I0 is the initial number of scintillation photons passing through the PSF core, ki and
k2 are the quantum efficiency of the PMTs, x is the scintillating position, / is the total length of
the PSF and d is the attenuation length (1/e) of the PSF.
The output signal R from the divider is equal to the ratio of pulse heights at each PMT:
R =
where
and
C =
x =
t = c'e*p(-y)
;rexp©
- ¦ In - = - ¦ InR + C
2 c 2
(3)
(4)
(5)
where
C =-(l + d- In )
2 V kj
(6)
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The use of a logarithmic amplifier provides a linear relationship between scintillating position x
and output signal R.
The attenuation length is defined as the distance along the PSF (from the point of initial
excitation) when the intensity of the signal has dropped to 1/e (36.8% of the original signal).
Single fibers may not be sensitive enough to detect gamma rays, so bundling many fibers
together can increase sensitivity (Park and Kim 2004). Takasaki et al. (1987) published a paper
on the development and use of PSF in collaboration with Kuraray using a 2.8-m bundle of five
fibers, each 1 mm in diameter to measure electrons from a 106Ru source.
Imai et al. (1991) examined the properties of a 1.75 m long, 1 mm in diameter BCF-10 PSF with
poly(methyl methacrylate) (PMMA) cladding to study the measurement of gamma rays, x-rays,
fast neutrons and alpha particles. Alpha particles were not able to penetrate the cladding, but the
results also showed the potential for spatially flexible and continuous position-sensitive detectors
for neutrons, gamma rays and x-rays. Oka et al. (1998) evaluated 20-m long, 1 mm in diameter
polystyrene core PSF with PMMA cladding for wide-area monitoring applications. The design
included 20 m of silica fiber on each end of the PSF and found that silica fiber resulted in a
decrease in the position resolution of approximately 1.5 dB/m. Resolution was measured as full-
width at half maximum (FWHM) of the peak. Additional studies were performed with a 2-m
length PSF to achieve a target sensitivity of 1 count per second per meter, and a bundle of ten
fibers was produced, resulting in a precision of 20 centimeters (cm) or better.
Park and Kim (2004) investigated the bundles of three, seven, thirteen, eighteen and twenty-five
strands of BCF-12 PSF (1 m length, 1 mm in diameter) with 137Cs. The authors also investigated
the effect of casing materials around the bundle (both material and thickness). More fibers
resulted in increased detection efficiency. Additionally, detection efficiency was highest with
aluminum, followed by PVC plastic, while the lowest efficiency was observed with stainless
steel, and it was determined that an 0.8 mm aluminum casing had a much higher efficiency than
a 1.2 mm aluminum casing. The authors summarize that a few strands of fibers in aluminum
tubes are sensitive enough to be employed in microcurie (|iCi) level environments.
Nohtomi et al. (2008) utilized a bundle of ten BCF-10 PSF elements 15 m in length and 1 mm
diameter. The position resolution was estimated to be approximately 60 cm near the center of
the fiber and 75 cm near the edges, again at FWHM. Good linearity was maintained between the
source position and the peak channel. Nohtomi et al. point out that the use of long PSF detectors
is practically limited by the significant reduction of pulse height during the propagation of the
light signals inside the scintillation fiber, which is accompanied by the notable degradation of
position resolution as well as counting losses.
Chichester et al. (2012) evaluated three different Saint Gobain Crystals fibers (BCF-10, BCF-12
and BCF-20), each of which varies slightly in emission peak, decay time, and attenuation length.
The results showed that low-level gamma radiation fields could be detected continuously over
long distances. The response was exceptionally linear over a range of lengths, including over 15
m, and the spatial resolution was typically between 50 to 60 cm, depending on fiber type and
source position along the fiber. BCF-10 was found to be the most efficient of the three fibers
and also provided the best spatial resolution for lengths less than 15 m, while BCF-20 performed
better at lengths greater than 15 m.
In 2012, Hitachi-GE Nuclear Energy developed a plastic scintillation fiber that operates
continuously for four hours with a rechargeable battery that can measure air dose rate as far as 20
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m in a few seconds.3 The work was published in 2014 (Gamo et al.), providing examples of
using 1, 7 and 12 PSF bundles to measure contamination along a roadway gutter, and potential
applications on a building wall, a tree, a pond and attached to a vehicle to survey roads. The
technology is paired with GE's SOPHIDA and D-phod Viewer software with mesh sizes of 10 m
and 1 m, respectively.
Recent work by Sanada and colleagues at JAEA has investigated the application of PSF to
various contaminated areas resulting from the Fukushima Dai-ichi NPP incident. A 19-fiber, 12-
meter long PSF array was placed across a field, straddling the boundary between contaminated
and decontaminated land. The results showed a clear delineation between the two areas (Todani,
2011). At the same time, measurements of radiation dose rates were performed in Minamisoma
City and Date City, Japan, using PSF and identifying where high doses were collocated with
cracks in asphalt pavement (JAEA, 2011). Similarly, a 20-m long bundle of 10 polystyrene 1
mm in diameter PSFs with PMMA cladding was manually moved along outdoor surfaces at
schools at a rate of 0.1 m/s (equivalent to 0.2 miles per hour), allowing the 2-dimensional
mapping of 137Cs before and after decontamination (Torii and Sanada, 2013). In the same paper,
the technique was also applied to the front of a construction vehicle (e.g., IHI CL45 compact
track loader) and allowed the mapping of a 2,000-square meter (m2) area within one hour.
Assuming a road lane width of 3 m, the corresponding speed of the motorized application was
0.4 miles per hour. Additional studies were documented using PSF to measure the
contamination at the bottom of a pond in the Fukushima Prefecture using a 20 m submerged PSF
bundle (JAEA, 2014a). An extended length (50 m) PSF was used to monitor leakage from
contaminated water tanks at the Fukushima Dai-ichi NPP (JAEA, 2014b; JAEA, 2015)
Sanada et al. (2015) utilized nineteen bundled 1 mm diameter, 20 m length Kuraray SCSF-3HF
PSFs to measure 137Cs sediments below water in irrigation ponds that had collected falling rain
in the Fukushima prefecture. The results compared well with sediment cores withdrawn after
measurement with PSF. Subsequent measurements taken after decontamination were integrated
with Geographic Information System (GIS) maps to demonstrate monitoring of decontamination
efficacy. Example JAEA applications are shown in Figure 3.4 JAEA's PSF system is a "p-
Scanner" which is equipped with a PSF detector built by JREC Co. Ltd. (Eniwa City, Hokkaido,
Japan) and the data processing software.
Collaboration with Japan and leveraging PSF development in contaminated environments can
better prepare the U.S. radiological response capability in urban and rural areas. Potential
applications have been identified, together with scientific and technical gaps that need to be
addressed before development and deployment in the U.S.
3 http://enformable.com/2012/Q5/ge-developing-fiber-optic-gamma-radiation-dose-rate-detection-and-measurement-
system/ last accessed September 2017)
4 Research and development of radiation measurements following nuclear power mechanism, Japan Atomic Energy
Agency Fukushima Research and Development Department, Fukushima Environmental Safety Center, November
20, 2015 (Japanese), provided by JAEA/Sanada.
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Data Processing
Data
Processing .
Signal and power cable
Figure 3. JAEA Application of PSF in Post-Fukushima Surveys (reproduced from JAEA4)
(A) PSF equipment supplied by JREC Co. Ltd.; (B) Application of PSF to survey pond sediments; (C)
Application of PSF to survey forest soil; (D) Application of PSF to measure outdoor urban surfaces, e.g.,
school playground.
2.2 Radiological Response Survey Technology Applications
2.2.1 Application in Transportation and Agriculture Sectors
As demonstrated in Japan using a compact loader (Torii and Sanada, 2013), PSF can be attached
to vehicles to provide two-dimensional survey capability. The concept may be extended to
include application on vehicles traveling at a higher rate of speed, for example, on a truck, van or
sports utility vehicle (SUV) fitted with signal processing equipment to provide real-time ground
surveys of roads and freeways, a capability additional to those already maintained by DOE,
DHS, EPA5, and JAEA6.
According to the US Department of Transportation Federal Highway Administration7, the
recommended US freeway lane width is typically 3.6 m, and a local roadway is typically 2.7 to
"s http://www.epa.gov/radiation/radiological-emergencv-response-expertise-and-eciuipment#tab-2 (last accessed
September 2017)
6 Sasakino Analytical Laboratory, JAEA Fukusliima Environmental Safety Center
7 http://safetv.fhwa.dot.gOv/geometric/pubs/mitigationstrategies/chapter3/3 lanewidthcfm (last accessed September
2017)
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3.6 m. Therefore, for a five-lane freeway, the freeway width on either side of the median is 18 m
(not including shoulder). It is therefore possible to survey the entire width of a freeway in a
single pass with a 20-meter PSF perpendicular boom. In this case, the rate of surveying would
be dependent on the response of the PSF with respect to vehicle speed. Alternatively, PSF
perpendicular booms could be deployed that are between 2.7 and 3.6 m wide to survey single
freeway lanes and local roads. Freeway on- and off-ramps are typically 3.6 to 9.2 m per lane,
while arterial roads are between 3.3 and 3.6 m per lane. The outside paved shoulder width on
freeways should be at least 3.0 m, while inside shoulder width should be between 1.2 and 3.0 m,
depending on the number of lanes and truck traffic. Shoulders for mountainous terrain may be
smaller. Similarly, the approach could be used to survey airport runways, taxiways,
loading/servicing/maintenance areas. In Japan, the technology could be evaluated and
demonstrated on local contaminated roads and potentially the Joban Expressway.
For agricultural land, PSF may be combined with farm equipment such as a tractor.
Alternatively, when combined with a combine harvester, areas of contamination may be removed
immediately. The technology may also be applied to a work train typically used for track
maintenance. Such an application may permit surveying of track and ballast to assist in
decontamination planning and waste minimization.
Proposed evaluations and demonstrations
The speed of surveying should be optimized to balance detection sensitivity with surface area
and time constraints. This study will likely include a variation in PSF length and bundle size.
Several vehicles should be evaluated, including: (a) the JAEA Sasakino Analytical Laboratory
SUV, (b) a larger vehicle capable of accommodating a longer PSF for freeway or runway
application, and (c) a rail work car. Additionally, the application of a stabilization agent, fixative
or marker should also be demonstrated to aid in the decontamination planning and preparation.
Such an application may require deployment on a service vehicle such as a tanker/spray/spreader
truck or street-sweeping vehicle. Additionally, the speed of the vehicle should be investigated to
determine the fastest speed that can still achieve detection at the appropriate level. One possible
solution to increase speed and improve detection is applying fibers parallel to the vehicle motion,
providing detection along the entire length (or beyond if towed). This application would require
multiple bundles to cover the area beneath the vehicle. For example, if it is assumed that a single
PSF at a distance of 10 cm from the surface has a viewing angle of 90° (with some collimation to
prevent background from sky-shine and surroundings), a 20 cm viewing region is produced
under the entire length of the fiber. A vehicle equipped with five bundles of 2 m PSF fibers
spaced approximately 20 cm apart may cover aim wide vehicle and may survey 2 m2 at any
given time, resulting in quicker surface scanning capabilities (potentially 2 to 10 miles per hour
[mph]) compared to a single bundle placed perpendicular to the vehicle motion (such as those
demonstrated by JAEA at 0.2 mph). However, axial positioning of PSF compared to the vehicle
motion would result in a minimum resolution of 20 cm for survey positioning. A combination of
transverse and axial fibers in a grid may provide both improvements in survey speed while
maintaining the sensitivity demonstrated by Sanada et al. Rapid detection will improve the early
phase response using containment or decontamination technologies.
2.2.2 Building Survey and Decontamination Progress Applications
Surveying contamination on the outside of a high-rise building may be challenging in built-up
urban areas and major cities. Additionally, monitoring the progress of high-rise building
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decontamination without interference from ground-shine, sky-shine and background from other
buildings is also problematic. One solution is to attach a PSF bundle to a window-cleaning
platform (e.g., Figure 4)8 and move the platform across the surface of each wall. This process
would permit "mapping" of the entire building and would provi de insight into decontamination
methods (related to the level of contamination and the surface type and geometry). Provided a
rigid casing or support is provided for the PSF, the length of the PSF could extend beyond the
platform.
Figure 4. An Example Window-Cleaning Platform
Proposed Evaluation and Demonstration:
Surveying the outer walls using PSF was proposed by Gamo et al. (2014) using a hand-held long
wand to survey the first two floors of a building. However, this is not practical for larger, taller
buildings. PSF should be evaluated and demonstrated using a window-cleaning platform to
survey high-rise buildings and to determine the need for collimation to aid in the determination
of building decontamination options and also demonstrate building decontamination progress
monitoring.
2.2.3 Water and Subsurface Applications
The properties of PSF permit application in submerged or wet environments. As already
demonstrated by JAEA (2014a; 2014b; 2015), PSF can be used to survey the bottom of ponds
and the perimeters of storage vessels. Typical sediments often bind 137Cs contamination quickly,
creating an equilibrium between the solid and liquid phase components of a pond. Monitoring
reservoir outflow pipes can be achieved using traditional detection equipment or by taking
aliquots and measuring off-line. PSF may be deployed upstream of such pipes to ensure
8 https://en.wikipedia.org/wiki/Window cleaner#/media/File:Platform window cleaner.jpg (last accessed October,
2017)
9
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reservoir security and water quality before waters enter the flow control and downstream release
systems.
It may also be possible to bury strings of PSFs to measure infiltrating groundwater and to map
and monitor plumes of contamination. Grids of PSF bundles (for example, as large as 50 m as
demonstrated by JAEA) may be deployed to detect and characterize radiological vector
movement in a 3-D environment, as depicted in Figure 5. Aluminum or PVC plastic may be
used as a casing without significant attenuation of detection (based on Park and Kim, 2004).
Figure 5. Schematic Diagram of Five PSF Bundles to Monitor a Subsurface Radioactive
Plume
Legend: Red = plume. Blue = groundwater flow direction. Yellow = vertical PSF bundles. White = signal divider.
In each application, collimation is important. Measuring the radioactivity associated with
sediment requires screening out radioactivity from the water above the sediment. Similarly,
measurement of contamination on a road via deployment of PSFs on a vehicle requires removal
of background signals from contamination on the vehicle itself, sky-shine or emanation from
nearby contaminated surfaces. On vehicles, this removal of signal may be achieved using a
semi-circular shield on the top half of the fiber, permitting scintillation in the fiber from only the
radiation shining upwards from the ground. Such a shield would likely be rigid and would
preclude some of the benefits of PSF (flexible and conforming to shapes). A similar situation
applies for applications in monitoring decontamination progress with PSF.
10
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Proposed Evaluations and Demonstrations:
The demonstration of PSF to survey sediments in ponds has already been accomplished by JAEA
(2014a). Sediments containing clay typically sequester 137Cs and incorporate the contamination
into the mica sheets within the clay structure. Therefore, surveying of sediments is an extremely
useful technique to understand the 137Cs sequestration process from water to sediment, any
potential resuspension of sediment due to currents or maritime traffic, and the sediment as a
potential source for dissolution of 137Cs upon changing aquatic conditions. The technology
should be demonstrated on a larger scale, e.g., a reservoir. The study should assess both active
(sweeping the sediment) and passive (autonomous, in-situ, real-time) monitoring. The latter
deployment may require an array of PSF bundles upstream from the outflow area.
Water tower security and quality represents another potential application that requires evaluation
and demonstration. Since PSF has already been demonstrated on a tank of contaminated water
(JAEA, 2015), an evaluation and demonstration of application on a community water tower
would require testing of sensitivity to determine low levels of contamination.
Plume monitoring (as discussed above) may be achieved when using an array of PSF bundles
buried beneath the surface, downstream from the groundwater flow. Arrays may be positioned
vertically (as shown in Figure 5) or horizontally, although the former may be more feasible to
deploy. Two example demonstrations include monitoring of runoff and subsurface flow at the
base of a contaminated mountain (in collaboration with JAEA and National Institute for
Environmental Studies (Japan), and the monitoring of contaminated groundwater from the
Fukushima Dai-ichi NPP in collaboration with Tokyo Electric Power Company.
Drinking water and wastewater are other areas of application for the PSF. Online monitoring of
radiation in drinking water is difficult due to the moderating effect of water. The PSF could be
put into the flow of tap water or wastewater and baseline (or background) radioactivity levels
established. Short-lived radionuclides could then be spiked into the flow, which would help
establish the minimum detection level of the PSF. Evaluating the effectiveness or progress of
decontamination in drinking water pipes after a contamination event is another application. A
water pipe could be contaminated with a short-lived radionuclide and decontamination
undertaken. The PSF could be moved down the pipe between fire hydrants before and after
decontamination to determine the effectiveness of the decontamination technique. In summary,
the application of PSF to further assist in the survey and monitoring of contaminated surfaces,
materials and water requires additional evaluation and demonstration. Such work should be
performed in collaboration with experts in Japan, applying technologies to 137Cs- contaminated
areas resulting from the Fukushima Dai-ichi NPP release.
3. PSF Prototype
The PSF may be able to provide multiple benefits during a wide area response. The magnitude
of impacted surfaces (both variety and area) may present a significant challenge and technical
gap. In National Planning Scenarios, an example RDD may contaminate 36 city blocks
(typically a fraction of a square mile), while an example IND may contaminate 3,000 square
miles (Government Accountability Office [GAO], 2013). Technologies that can be moved
across contaminated surfaces may prove to be useful tools in identifying contamination. Pre-
planning for monitoring and subsequent remediation can greatly reduce the time to respond, and
subsequently can minimize further contamination and reduce cleanup costs, allowing responders
li
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to minimize the impact to both public health and the environment. Roads and critical
infrastructure will be of primary focus for recovery efforts in the short term (road, rail, air),
providing ingress and egress routes, power, water, communications, health, security and
emergency services. As addressed in Section 2, the PSF can be applied under varied situations
that may be difficult for the existing detectors or monitors.
The objectives for the testing and development of PSF arrays are:
Develop a portable detector with ease of use and applications in both roads and water
infrastructure protection and recovery
Improve hardware from the JAEA demonstration of PSF technology
Use commercial off-the-shelf where practicable
Provide interchangeable bundle lengths (e.g., 2 m and 10 m)
Determine feasibility and characteristics of vehicle application to measure ground
contamination.
3.1 PSF Detector Components
A PSF detector contains a specified length of plastic scintillation fiber with a known attenuation
length, PMTs, a digital oscilloscope, a data communication board, and a computer controller
capable of displaying and recording results. For development and testing of Lawrence
Livermore National Laboratory's (LLNL) PSF detector, the following components were used:
(a) Saint Gobain Crystals BCF-12 scintillation fiber, 2-mm diameter (single and double cladding
to be used separately). BCF-12 has improved transmission for longer lengths, results in a
blue emission color with a 435-nm emission peak, 3.2 ns decay time, an attenuation length of
2.7 m and approximately 8,000 photons per megaelectron volt (MeV). The trapping
efficiency is at least 3.4% for single clad fibers and at least 5.6% for double clad fibers.9 The
2-mm diameter BCF-12 fiber was bundled in groups of 7 (Figure 6) to create a 6-mm
diameter bundle. The 2017 cost was $9.20 per m for double-clad fiber when ordering 100 m
or more.
An outer sleeve is required to prevent background ambient light reaching the fibers, to
maintain bundle integrity, to allow waterproofing, and to increase durability. Initial attempts
at encasing the fiber bundle had used black vinyl tubing, but the thickness of the black vinyl
tubing reduced the beta radiation sensitivity. Subsequently, fiber bundles were wrapped with
3MFP-301 heat-shrink tubing (polyolefin, 0.38-inch internal diameter before shrinking, 2:1
shrink ratio), allowing for a reduction in sleeve thickness by approx. 80% over vinyl tubing
and resulting in greatly increased sensitivity of the fiber bundle to beta radiation. The heat-
shrink tubing became somewhat stiff when shrunk, so the ends of the bundle (approximately
8 inches) were heat-shrunk to grip the fibers and maintain a fixed position in the connectors,
while leaving the rest of the bundle length unshrunk to maintain flexibility. A major
9 https://www.crystals.saint-gobain.com/sites/imdf.crystals.com/files/documents/sgc-organics-plastic-
scintillators !).pdf (last accessed January 20181
12
-------
consideration in the selection of the heat shrink tubing was finding a material with a
shrinking temperature below the melting point of the plastic fibers.
Figure 6. Bundle of Seven BCF-12 Scintillation Fibers Glowing from UV Light
(b) Two Hamamatsu 10721P-210 PMT modules with an 8-mm diameter face and built-in high
voltage (HV) power supply (Figure 7, left panel)10, with a 2017 cost of $980 each. Also
shown in Figure 7 (right panel) are the parts required to connect the PMT to the fiber bundle
(BNC [Bayonet Neill-Concelman] Jack: Amphenol 31-203-RFX, BNC Plug: Amphenol 31-
2-RFX) and the completed connection between PMT and fiber bundle. The BNC connectors
were modified by drilling out the center to accommodate the fiber bundle.
Figure 7. Image of Hamamatsu 10721 PMT and Subsequent Connection to Seven-Fiber
Bundle
(c) A Paul Scherrer Institut (PSI) DRS4 evaluation board four-channel digital oscilloscope using
Universal Serial Bus (USB) power and communication (Figure 8)11 with a 2017 cost of
$1,245.
10 http://www.hamamatsu.eom/us/en/product/alpha/C/3044/H10721-20/index.html (last accessed October 2017)
11 https://www.psi.ch/drs/evaluation-board (last accessed October 2017)
13
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DRSi Evaluation Board V5
I CK2. CH3 Ci
#
Trigger Clock
OUT IN OUT
<=00^
USB 2.0
Figure 8. Image of PSI DRS4 Evaluation Board
(d) A Raspberry Pi 3 single-board computer with USB and WiFi connectivity (Figure 9).12 The
current typical cost is approximately $50, depending on accessories purchased. Custom
software was written to interface with the DRS4 and with an Android tablet. Most computers
that run Linux could be used as well.
fttspfrirrj M 3 Ifedtl 8 Vi.2 j
(?) ft«ipfcerr; ti ZOIS
ih 5 3-S5» "
| an < :T3=»",
Figure 9. Image of Raspberry Pi 3 Board
(e) An Android tablet to interface with the detector system. The tablet used is a Samsung
Galaxy Tab S2 (Figure 10)13, which in 2017 cost approximately $250. Custom software was
12
https:/Av\v\v. raspberry pi. o ra/products/raspbciTv-pi-3-model-b/ (last accessed October 2017)
13
http://www.samsiuig.com/global/galaxv/galaxv-tab-s2/ (last accessed January 2018)
14
-------
written to interface with the Raspberry Pi and display the dose rate along the fiber. Other
Android tablets would likely work as well, as long as they run versions 4.4 to 6 of Android.
Android 7 might work, but the app has not been tested with it. Note that some tablets have
strong internal magnets designed for use with accessories such as keyboards, and these
magnets can interfere with PMT operation.
Figure 10. Samsung Galaxy Tab S2 Tablet
A schematic image of the complete system is shown in Figure 11, showing connections between
each component, and Figure 12 shows the prototype PSF detector system with data acquisition
and tablet operation.
- Incident^ -
Photorf^^
" ^ 10 "
PSF Bundle
PMT PMT
-------
PMT1
PMT2
DRS4 1
USB
Battery
Pack
Raspberry Pi
Samsung Galaxy Tab S2
Figure 12. 7-Fiber Bundle PSF Detector System with Data Acquisition and Tablet
Operation
The PSF prototype system tests were conducted by comparing the dose rate measurements using
a Fluke model 45IB Ion Chamber Survey Meter (Figure 13)14 certified to provide readings
within 10% when measuring between 20 kiloelectron volts (keV) and 2 MeV x-rays and gammas
and between 0.5 millirem (mr) per hour (h) and 50 r/h. It is recalibrated annually.
*1
Figure 13. Fluke model 451B Ion Chamber Survey Meter
14 https://www.grainger.com/search?searchBar=tme&searchOuerv=451B+ion
16
-------
3.2 PSF Detector Testing and Characterization
Radioisotope sources were used to determine the position resolution, dose rate accuracy and
minimum detectable dose rate. Tests were performed with the fiber in air and also submersed in
water to evaluate the performance of the ability of the detector to detect contamination on roads
relevant to transportation infrastructure, and underwater relevant to water infrastructure
protection and early detection. Characterization was performed using available beta and gamma
radioisotope sources. In the location where the PSFs were tested, LLNL possesses the following
beta sources:
Cs-137 (514 keV beta end-point)
Sr90/Y-90 (546 keV and 2.3 MeV beta end-points)
In the same location, LLNL possesses the following gamma sources:
Am-241 (60 keV)
Ba-133 (predominately 356 keV)
Co-57 (120 keV)
Cs-137 (662 keV)
Co-60 (1,173 and 1,332 keV)
3.2.1 Attenuation Length
The attenuation length as provided by Saint Gobain for BCF-12 is 2.7 m. LLNL verified the
attenuation length of a 7-fiber bundled PSF detector by determining the maximum intensity of
photons from Cs-137 at 1 m intervals from the PMT and fitting the data points to the equation I =
Ioe"x where a is the attenuation length and Io is the maximum intensity at position 0, right next
to the PMT. The attenuation length was determined to be 2.65 ±0.1 m, consistent with the value
from Saint Gobain.
3.2.2 Position Resolution
To evaluate the position resolution, the seven-fiber bundle was laid out. Collimated sources
listed above were placed at several different locations along the length of the fiber. Gamma
sources were collimated with lead bricks, and beta sources were collimated using plastic discs
with a 3-mm hole in the center. In both cases, the aperture was much smaller than the position
resolution of the system. The width of the position peak was used to determine the position
resolution.
An experimental test matrix for determining position resolution is shown in Table 2, which was
completed to determine position resolution along a fiber or fiber bundle. Position is listed as
percent of the length of the bundle from one end. The test matrix was completed with peak
position in percent of length and physical distance from the end, measured in centimeters and
repeated in triplicate. The seven-fiber bundle used for this measurement was 10 m.
The Am-241 source, which emits 60 keV gamma rays, had too low an energy to be detected
using the 10-m fiber bundle. In addition, the Co-57 source, which emits 122 keV gamma rays,
has a very low detection efficiency and was barely visible above background, producing poor
17
-------
results due to a combination of the low light yield of plastic scintillators combined with high
losses over the 10-m fiber. Both Am-241 and Co-57 were visible to 3 m and 1 m fiber bundles.
To fill the energy gap between Co-57 at 122 keV and Cs-137 at 662 keV, measurements were
conducted with Ba-133, which emits gamma rays predominantly at 356 keV. Measurements in
Table 2 were all for 1000 counts total along the fiber. The results show excellent position
determination for energies above 350 keV. The position FWHM is 47 cm and is consistent
across the length of the fiber. With 100 counts from a point source, the position is localized to
within 3 cm.
Table 2. Position Resolution Test Matrix for a 10-m Seven-Fiber Bundle
Nominal Distance along fiber
10%
20%
30%
40%
50%
Actual Distance along fiber (cm)
100
200
300
400
500
Cs-137 Beta
Rep 1
104.8
197.2
299.3
397.1
495.6
Rep 2
104.5
199.3
296.6
396.1
495.2
Rep 3
103.1
199.7
297.1
397.4
495.3
AVERAGE
104.13
198.73
297.67
396.87
495.37
STDEV
0.91
1.34
1.44
0.68
0.21
Sr-90/Y-90 Beta
Rep 1
100.6
201.3
298.4
396.2
494.1
Rep 2
101.0
202.1
297.8
398.2
494.4
Rep 3
101.0
198.6
300.2
396.1
494.0
AVERAGE
100.87
200.67
298.80
396.83
494.17
STDEV
0.23
1.83
1.25
1.18
0.21
Am-241 Gamma
No measurable results
Co-57 Gamma
Rep 1
97.7
197.6
254.0
408.6
444.2
Rep 2
99.0
199.7
326.0
401.5
480.0
Rep 3
106.7
204.4
307.8
393.7
478.8
AVERAGE
101.13
200.57
295.93
401.27
467.67
STDEV
4.86
3.48
37.44
7.45
20.33
Cs-137 Gamma
Rep 1
99.7
198.7
298.1
395.1
493.2
Rep 2
101.0
199.1
295.8
394.6
492.8
Rep 3
100.2
198.5
297.2
394.2
494.1
AVERAGE
100.30
198.77
297.03
394.63
493.37
STDEV
0.66
0.31
1.16
0.45
0.67
Co-60 Gamma
Rep 1
99.9
198.6
295.8
393.1
493.1
Rep 2
100.5
198.6
297.8
395.6
494.3
Rep 3
100.9
199.2
296.4
393.2
494.3
AVERAGE
100.43
198.80
296.67
393.97
493.90
STDEV
0.50
0.35
1.03
1.42
0.69
Ba-133 Gamma
Rep 1
101
200.7
297.4
394
490.6
Rep 2
104.4
199.4
298.8
395.7
492.1
Rep 3
103.2
201.2
295.9
396
490.3
AVERAGE
102.87
200.43
297.37
395.23
491.00
STDEV
1.72
0.93
1.45
1.08
0.96
18
-------
Measurements were also made with an individual fiber 15 m in length for one beta and one
gamma source (Table 3). The test matrix was completed with peak position in percent of length
and physical distance from the end, measured in centimeters and repeated in triplicate. The
measurements were all made for 1000 total counts in the fiber. The position FWHM is 55 cm for
the 15-m bundle.
Table 3. Position Resolution Test Matrix with Replicates in Parentheses for a 15-m Single
Fiber
Source / Radiation
Nominal Distance
along fiber
10%
20%
30%
40%
50%
Actual Distance
along fiber (cm)
150
300
450
600
750
Sr-90/Y-90 Beta
Rep 1
166.6
304.2
454.6
601.5
753
Rep 2
164.7
304.6
456.5
602.3
753.5
Rep 3
164.3
306.2
455.9
603.9
755.5
AVERAGE
165.2
305.0
455.7
602.6
754.0
STDEV
1.2
1.1
1.0
1.2
1.3
Cs-137 Gamma
Rep 1
159.2
303.7
451.9
601.7
754.6
Rep 2
161.5
303.9
453.8
601.2
753.9
Rep 3
161.0
302.6
451.5
603.7
755.4
AVERAGE
160.6
303.4
452.4
602.2
754.6
STDEV
1.2
0.7
1.2
1.3
0.8
Additionally, two collimated sources were placed close together along the fiber to determine
whether they can be resolved as two peaks at nominal distances along the fiber (Table 4). The
distance between the two sources was successively reduced in 5 cm increments until the peaks
were no longer resolved. The experiments were repeated in triplicate, with the shortest distance
between the two sources reported in centimeters for each experiment. Since the Am-241 source
is not detectable with the 10-m fiber, the measurement with Cs-137 and Am-241 has no results.
The criteria for peaks to be resolved was a dip between the two peaks of approximately 25% of
the maximum of the smaller of the two peaks. An example is shown in Figure 14. This
criterion is similar to the Rayleigh criteria used to define the distance needed for two point
sources to be resolved optically. Since the position resolution is dominated by the timing of the
system, which does not change with the various measurements, it is not surprising that all results
are the same.
19
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Table 4. Two-Source Resolution Test Matrix with Replicates in Parentheses for a 10-m
Seven-Fiber Bundle
Source / Radiation
Nominal Distance along fiber
10%
20%
30%
40%
50%
Actual Distance along fiber
(cm)
100
200
300
400
500
Cs-137 + Sr-90/Y-90
Rep 1
50
50
50
50
50
Rep 2
50
50
50
50
50
Rep 3
50
50
50
50
50
AVERAGE
50
50
50
50
50
STDEV
0
0
0
0
0
Cs-137 + Co-60
Rep 1
50
50
50
50
50
Rep 2
50
50
50
50
50
Rep 3
50
50
50
50
50
AVERAGE
50
50
50
50
50
STDEV
0
0
0
0
0
Cs-137+ Am-241
NO
RESULTS
-
1
t
nnl ¦ IfrrVl
A
0 2 4 6 8 10
Distance (meters)
Figure 14. Example Plot Showing Two Sources, Cs-137 and Co-60, Located 50 cm Apart.
3.2.3 Dose Rate Accuracy
To test the dose rate accuracy of the PSF detector, the dose rate from radioisotope sources was
first measured using a handheld dose rate meter. The source was then measured at several
20
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different locations along the seven-fiber bundle using the PSF detector and different distances
from the seven-fiber bundle to ensure that the PSF dose rate reading is consistent with the
handheld dose rate meter. An experimental test matrix for determining dose rate accuracy is
shown in Table 5, which details the conditions at which dose rate accuracy was measured.
These measurements were all taken with the detector in air. The percent values refer to the
position along the fiber or fiber bundle where the measurement was taken. Low, Medium, and
High refer to three different dose rates that were measured. The actual values were different for
the different gamma and beta measurements. Low dose rates were determined to be near the low
end of detection for the system. High dose rates were determined to be either near the highest
dose rate the system can measure or as high as could be obtained with available sources.
Medium was designated to be a dose rate between High and Low. The High, Medium and Low
values were determined after the characteristics of the system were known. The test matrix was
completed by comparing the dose rate measured on the hand-held survey meter and the dose rate
measured using the seven-fiber bundle PSF detector.
The bundle was calibrated using a Cs-137 gamma source because its energy is near the middle of
the energy spectrum. Different calibration coefficients are used for different positions along the
fiber since varying amounts of light loss occur due to fiber attenuation. The fiber was curved
around the point sources used to try to expose them to a consistent radiation field which
improves measurement accuracy. The results indicate that the system is insensitive to gamma
rays below approximately 150 keV since 59.5 keV gammas from Am-241 were not detected at
all, and 122 keV gammas from Co-57 produced dose rates significantly lower than what was
actually present. Similarly, low dose rate results were measured for the Cs-137 beta particles,
which have a relatively low-end point energy of 514 keV. The system clearly responds to them
as seen below. The response is not due solely to gammas because the dose rate drops
significantly when a thin piece of plastic is inserted between the Cs-137 beta source and the
fiber.
The beta dose rate will read too low for at least two reasons. First, the betas slow down or stop
in the heat shrink tube that surrounds the fibers, which reduces the energy deposited in the fibers
and hence their dose. Second, the betas also slow down or stop in the fibers closest to the source,
which makes the active volume smaller than the total volume. Since dose and dose rate are
based on mass, the measured dose rate will be less than the actual dose rate.
21
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Table 5. Dose Rate Accuracy Test Matrix for a 10-m Seven-Fiber Bundle. Dose rates are in
microrem (jir) per h
Nominal
Distance
10%
30%
50%
10%
30%
50%
10%
30%
50%
along fiber
Actual
Distance
Along Fiber
100
300
500
100
300
500
100
300
500
(cm)
Nominal
Dose Rate
Low
Low
Low
Medium
Medium
Medium
High
High
High
Cs-137 Beta
130
130
130
430
430
430
1800
1800
1800
Rep 1
31
33
28
44
59
59
112
196
167
Rep 2
35
25
32
50
53
60
97
186
181
Rep 3
30
34
40
54
63
62
110
188
192
AVERAGE
32.00
30.67
33.33
49.33
58.33
60.33
106.33
190.00
180.00
STDEV
2.65
4.93
6.11
5.03
5.03
1.53
8.14
5.29
12.53
Sr-90/Y-90
Beta
120
120
120
470
470
470
1650
1650
1650
Rep 1
50
70
122
330
283
531
852
783
1164
Rep 2
52
88
104
327
275
441
834
830
1049
Rep 3
49
65
90
341
279
420
738
832
965
AVERAGE
50.33
74.33
105.33
332.67
279.00
464.00
808.00
815.00
1059.33
STDEV
1.53
12.10
16.04
7.37
4.00
58.97
61.29
27.73
99.90
Am-241
NO
Gamma
RESULTS
Co-57
Gamma
60
60
60
120
120
120
220
220
220
Rep 1
17
24
33
19
22
24
30
48
40
Rep 2
18
35
31
21
23
34
41
44
44
Rep 3
16
21
30
19
24
38
32
46
40
AVERAGE
17.00
26.67
31.33
19.67
23.00
32.00
34.33
46.00
41.33
STDEV
1.00
7.37
1.53
1.15
1.00
7.21
5.86
2.00
2.31
Cs-137
Gamma
50
50
50
220
220
220
530
530
530
Rep 1
43
47
63
225
217
221
408
396
496
Rep 2
44
44
61
218
223
205
444
402
528
Rep 3
49
47
59
230
198
202
437
407
547
AVERAGE
45.33
46.00
61.00
224.33
212.67
209.33
429.67
401.67
523.67
STDEV
3.21
1.73
2.00
6.03
13.05
10.21
19.09
5.51
25.77
Co-60
Gamma
60
60
60
130
130
130
880
880
880
Rep 1
58
61
72
224
168
157
676
841
797
Rep 2
53
57
62
232
175
183
673
903
679
Rep 3
52
56
63
244
176
178
630
730
805
AVERAGE
54.33
58.00
65.67
233.33
173.00
172.67
659.67
824.67
760.33
STDEV
3.21
2.65
5.51
10.07
4.36
13.80
25.74
87.65
70.55
Ba-133
Gamma
50
50
50
100
100
100
270
270
270
Rep 1
23
26
25
41
42
40
111
144
142
Rep 2
25
27
26
46
46
33
133
150
139
Rep 3
23
23
24
42
50
41
117
128
131
AVERAGE
23.67
25.33
25.00
43.00
46.00
38.00
120.33
140.67
137.33
STDEV
1.15
2.08
1.00
2.65
4.00
4.36
11.37
11.37
5.69
22
-------
No Source
(blank
control)
15
15
15
Rep 1
Rep 2
Rep 3
AVERAGE
STDEV
14
15
18
15.67
2.08
15
17
13
15.00
2.00
13
10
16
13.00
3.00
3.2.4 Minimum Detectable Dose Rate
To evaluate the minimum dose rate that can be measured by the PSF detector, the distance
between the source and the seven-fiber bundle was increased until no statistically significant
signal was observed. Longer integration times can yield lower minimum detectable dose rates.
All measurements for determining minimum detectable dose rates were made for 10 seconds.
Several locations along the bundle were measured. The minimum detectable dose rate did not
vary much by location along the fiber.
The matrix shown in Table 6 identifies the positions and isotopes that were used to measure the
minimum detectable dose rate. The position is listed as percent of the length of the bundle being
tested. Note that minimum detection limits change based on the radioactive background during
the measurement. Background can change based on location (concrete buildings typically have a
higher background from K-40) as well as radon concentration (which varies based on weather
and other conditions). The test matrix was completed by comparing the dose rate measured on
the hand-held survey meter and the seven-fiber bundle until one or both signals fall to
background levels.
23
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Table 6. Minimum Detectable Dose Rate Test Matrix with Replicates in Parentheses for 10-
m Seven-Fiber Bundle. Dose rates are in jir/h
Nominal Distance along fiber
10%
30%
50%
Actual Distance along fiber (cm)
100
300
500
Cs-137 Beta Dose Rate from Fluke
370
370
370
Rep 1
41
43
35
Rep 2
37
35
35
Rep 3
39
36
40
AVERAGE
39.00
38.00
36.67
STDEV
2.00
4.36
2.89
Am-241 Gamma
NO
RESULTS
Co-57 Gamma Dose Rate from Fluke
30
30
30
Rep 1
37
19
25
Rep 2
26
33
23
Rep 3
25
28
27
AVERAGE
29.33
26.67
25.00
STDEV
6.66
7.09
2.00
Cs-137 Gamma Dose Rate from Fluke
25
25
25
Rep 1
31
47
52
Rep 2
27
38
61
Rep 3
42
35
41
AVERAGE
33.33
40.00
51.33
STDEV
7.77
6.24
10.02
Co-60 Gamma Dose Rate from Fluke
25
25
25
Rep 1
34
49
33
Rep 2
56
45
38
Rep 3
44
37
29
AVERAGE
44.67
43.67
33.33
STDEV
11.02
6.11
4.51
3.2.5 Transportation and Water Infrastructure Applications
The results garnered from experiments described in Sections 3.3 to 3.5 were used to determine
the operating parameters for demonstration of the LLNL-developed prototype PSF detector to
measure contamination and dose rates on surfaces (such as roads or soil).
Additional experiments were performed to determine the speed at which a bundled fiber detector
can be moved over a surface to scan for contamination while maintaining a detectable signal.
In conjunction with measurements taken with the fiber placed under water, an assessment was
made of the detection properties of the bundled fiber detector to measure dose through water.
Specifically, a portion of the 10-m seven-fiber bundle was placed under water and gamma
sources were placed in air, next to the water container.
To evaluate the minimum dose rate that can be measured by the PSF detector while it is
submerged, the distance between the source and the seven-fiber bundle was increased until no
statistically significant signal was observed. Longer integration times can yield lower minimum
detectable dose rates. Results in Table 7 are for 10 second counts. For Co-57, longer integration
times were tried, but there was still no signal with water between the source and the fiber.
24
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The matrix shown in Table 7 identifies the isotopes that were used to measure the minimum
detectable dose rate. Note that minimum detection limits change based on the radioactive
background during the measurement. Background can change based on location (concrete
buildings typically have a higher background from K-40) as well as radon concentration (which
varies based on weather and other conditions). The test matrix was completed by measuring the
dose rate using the seven-fiber bundle until the signal falls to background levels.
A measurement was made using a Sr-90 source. As expected, even 1 cm of water blocks
essentially all betas.
Table 7. Minimum Detectable Dose Rate Test Matrix with Replicates in Parentheses for a
Submerged Portion of 10-m Seven-Fiber Bundle in Water
Min. Det.
Dose Rate
Am-241 Gamma
NO
RESULTS
Co-57 Gamma
NO
RESULTS
Cs-137 Gamma Dose Rate by Fluke
80
Rep 1
70
Rep 2
52
Rep 3
37
AVERAGE
53
STDEV
16.5
Co-60 Gamma Dose rate by Fluke
60
Rep 1
27
Rep 2
41
Rep 3
49
AVERAGE
39
STDEV
11.1
By assessing the characteristics of the seven-fiber bundle in air and measuring the dose rates
while the fiber is submerged in water, an assessment can be made regarding the efficiency of the
detector in water and the feasibility for water infrastructure applications.
3.3 Quality Assurance and Quality Control
The dose rate meter was checked before each use to verify there are no errors, that the battery
was not low, and that the meter had been calibrated within 1 year. The meter was certified to
measure dose rate within 10% when measuring a value that is between 10% and 100% of the
full-scale range being used. Full scale ranges available, in mr/h, are 5, 50, 500, 5000, and 50000.
The meter was recalibrated annually by the LLNL Environmental Safety and Health Functional
25
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Area. The calibration is only certified for x-ray and gamma radiation between 20 keV and 2
MeV. The meter also responds to beta radiation, but is not certified to 10% error.
4. Conclusions and Recommendations
This study evaluated the potential use of PSF detection system during a wide area radiological
incident response. A prototype PSF system was developed and characterized. The cost of a
prototype PSF system is relatively inexpensive (less than $5k) compared to other mobile survey
methods described in Section 1. Comparative sodium iodide equipment costs range from $5k to
$40k each, but such a system does not offer the positioning sensitivity that PSF provides. The
operating guide for the prototype PSF is in Appendix A.
The 10-m fiber bundle can be a very useful tool for decontamination or monitoring missions.
Using a bundle of seven 2 mm diameter fibers, the system is sensitive to typical background dose
rates for gamma rays using a 1 second integration time. Point sources can be located within 5
cm along the fiber length by measuring the difference in arrival time of light from interactions.
The system can detect a 10 |iCi Co-60 source or a 40 |iCi Cs-137 source at 1 m in a few seconds.
If used on a vehicle with the fiber mounted on a boom within 20 cm of the ground, the system
could detect these sources while traveling at 2 mph. By using a thin cladding material such as
heat shrink tubing, the system can be sensitive to beta decays as well, which is beneficial for
monitoring for contamination.
The 15-m fiber that was tested demonstrated that the attenuation along the fiber is too great to
allow good performance. In the future, a lower attenuation fiber could be used to increase the
fiber length, if desired. A lower attenuation fiber would also improve the performance of a 10-m
bundle by improving its low energy performance. Note that the quantum efficiency of PMTs
drops quickly at longer wavelengths, so moving to a green-emitting fiber with lower attenuation
will likely result in poorer overall performance. With the current 10-m fiber bundle, many of the
detected events had only a single photon detected at one of the PMTs, especially for lower
energy sources, making PMT selection critical as well.
The oscilloscope used in this system, the DRS4 demonstration board, has several limitations.
The two most significant limitations are a count rate limit of approximately 500 counts per
second, and a limited ability to define what constitutes a coincidence. The count rate limit is not
a problem in relatively low dose rate environments, up to several mr/h. Higher dose rate
environments could be accommodated by accounting for dead time. The limitations on the
trigger will make it difficult to use on fibers longer than approximately 15 m.
Future development of the system could focus on several areas. First, using Kurary fibers with a
4-m attenuation length would improve the performance of 10 m fibers and would allow longer
fibers to be used, probably to approximately 20 m. We were not able to obtain Kurary fibers for
testing in this project. Other methods to increase the fiber length include having multiple
sections back to back (this requires PMTs along the length of the fiber, which could be
cumbersome), or having multiple shorter segments of scintillating fiber connected to non-
scintillating plastic or silica fiber. Non-scintillating fibers can have attenuation lengths orders of
magnitude longer than scintillating fibers, so very long fibers would be possible. The ultimate
26
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length would be limited by count rates; to determine the location of an event, it must be unlikely
that pulses not from that event (such as dark counts from the PMT or a second event) occur at the
same time, causing a random coincidence.
If a large number of these systems are required, then a manufacturing prototype could be
developed in coordination with a company to segue into larger scale production.
Another area for future studies would be algorithm development. The system is clearly sensitive
to low levels of radioactivity, but the performance could be improved by developing algorithms
to statistically determine if a location along the fiber is above background. This development
would also make the system considerably easier to use for an operator. While these types of
algorithms exist in general, they would need to be applied to this specific application. The
unique characteristics of the system could be used to advantage as well. For example, sections of
the fiber not near contamination could be used to determine background in real time, thus
improving minimum detection levels.
The system should also be integrated with a global positioning system (GPS) to determine the
geolocations of the fiber end points, allowing the dose rates along the fiber to be encoded with
latitude and longitude coordinates. This GPS could be integrated into a GIS system to make
maps or into a more advanced (or existing) system to provide situational awareness.
Finally, since the basic hardware design has been shown to be effective, the actual use cases
could be expanded. Mounting the fiber on a boom in front of a vehicle to monitor a road or field
is an obvious use. Monitoring fixed locations such as water infrastructure is another possibility.
One could imagine a swarm of tethered balloons (or unmanned aerial vehicles) with fibers
dangling below to monitor a radioactive plume moving through the atmosphere. Many other
possibilities exist.
27
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5. References
Berlman, I.B. (1971) Handbook of Fluorescence Spectra of Aromatic Molecules. New York:
Academic.
Burmeister, H., Sonderegger, P., Gago, J.M., Maio, A., Pimenta, M., Perrin, D. and Thevenin,
J.C. (1984) Electromagnetic Calorimetry using Scintillating Plastic Fibres, Nuclear Instruments
and Methods in Physics Research, 225:530-533.
Chichester, D.L., Watson, S.M. and Johnson, J.T. (2012) Comparison ofBCF-10, BCF-12 and
BCF-20 Scintillating Fibers for use in a 1-Dimensional Linear Sensor, IEEE Nuclear Science
Symposium 2012. Also available as an Idaho National Laboratory Report, INL/CON-12-25807,
October 2012.
Chupp, E.L. and Forrest, D.J. (1966) A Directional Neutron Detector for Space Research Use,
IEEE Transactions on Nuclear Science, 13(l):468-477.
DHS (2013) Standoff Radiation Detectors: Market Survey Report, Department of Homeland
Security (DHS) Report, August 2013, National Urban Security Technology Laboratory.
Gamo, H., Kondo, M., Hashimoto, T., Tayama, R. and Tsukiyama, T. (2014) Development of a
PSF-Detector for Contaminated Areas, Progress in Nuclear Science and Technology, 4:695-698.
GAO (2013) Nuclear Terrorism Response Plans: Major Cities Could Benefit from Federal
Guidance on Responding to Nuclear and Radiological Attacks, Report GAO-13-73 6, US
Government Accountability Office, Washington, DC. (September 2013).
Imai, S-L, Soramoto, S., Mochiki, K-I. and Iguchi, T. (1991) New Radiation Detector of Plastic
Scintillation Fiber, Review of Scientific Instruments, 1991, 62(4): 1093-1097.
Ishikawa, M., Unesaki, N., Kobayashi, T., Sakurai, Y., Tanaka, K, Endo, S., Hoshi, M. (2002)
Real-Time Estimation of Neutron Flux During BNC T treatment using Plastic Scintillation
Detector with Optical Fiber, 10th International Congress on Neutron Capture Therapy, Essen,
Germany, September 2002, published in Research and Development in Neutron Capture
Therapy, pp443-447.
JAEA (2011) Fukushima Support Headquarters News, No. 3, Japan Atomic Energy Agency
(JAEA) October 14th, 2011 (Japanese).
JAEA (2014a) TOPICS Fukushima, Japan Atomic Energy Agency (JAEA) Aug 8th 2014, No. 50,
available at: http://fukushima.iaea.go.ip/english/topics/pdf/topics-fukushima050e.pdf (accessed
October 2017).
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JAEA (2014b) TOPICS Fukushima, Japan Atomic Energy Agency (JAEA) Oct 10th 2014, No.
53, available at: http://fukushima.iaea.go.ip/english/topics/pdf/topics-fukushima053e.pdf
(accessed October 2017).
JAEA (2015) TOPICS Fukushima, Japan Atomic Energy Agency (JAEA) Feb 20th 2015, No. 61,
available at: http://fukushima.iaea.go.ip/english/topics/pdf/topics-fukushima061e.pdf (accessed
October 2017).
Jopson, R.C., Wright, R.E and Mark, H. (1960) Thin Fiber Scintillation Counter for Determining
Particle Beam Distributions in Accelerators, Lawrence Livermore National Laboratory Report
UCRL-5818, Livermore CA.
Nohtomi, A., Sugiura, N., Itoh, T. and Torii, T. (2008) On-line Evaluation of Spatial Dose-
Distribution by using a 15m-long Plastic Scintillation-Fiber Detector, IEEE Nuclear Science
Symposium Conference Record, N02-193, 965.
Oka, T., Fukiwara, H., Takashima, K., Isami, T. and Tsutaka, Y. (1998) Development of Fiber
Optic Radiation Monitor using Plastic Scintillation Fibers, Journal of Nuclear Science and
Technology, 35(12):857-864.
Park, J.W. and Kim, G.H. (2004) Detection of Gamma Rays using Plastic Scintillating Fibers,
Journal of Nuclear Science and Technology, Suppl. 4, 373-376.
Reynolds, G.T. and Condon, P.E. (1957) Filament Scintillation Counter, Review of Scientific
Instruments, 28:1098-1099.
Ruchti, R.C. (1996) The Use of Scintillating Fibers for Charged-Particle Tracking, Annual
Reviews of Nuclear and Particle Science, 46:281-319.
Sanada, Y., Urabe, Y., Orita, T., Takamura, Y. and Torii, T. (2015) In-situ Measurement of
Radiation Distribution in Bottom Sediments of Irrigation Ponds using Plastic Scintillation Fiber,
Proceedings of the 23rd International Conference on Nuclear Engineering, Chiba, Japan, May 17-
21, 2015.
Takasaki, F., Saito, H., Shimizu, T., Kondo, S. and Shinji. O. (1987) Development of Plastic
Scintillation Fiber, Nuclear Instruments and Methods in Physics Research, A262: 224-228.
Todani, K. (2011) JAEA Activities Towards Environmental Restoration of Fukushima, Japan
Atomic Energy Agency (JAEA) Report, Headquarters of Fukushima Partnership Operations,
October 16th, 2011, available at: http://vvvvvv.iaea.go.ip/fukushima/pdf/decon e 09.pdf
(Japanese) (accessed October 2017).
Torii, T. and Sanada, Y. (2013) Measurement Technology of Pollution Distribution Taken in a
Plane, Isotope News, No. 714, October 2013 (Japanese).
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Appendix A: Prototype PSF Operating Guide
A.1 Components and System Description
The major components of the system are the fiber, PMTs, a DRS4 digital oscilloscope,
Raspberry Pi single board computer, and Samsung Galaxy Tab S2 tablet. Everything is powered
from a USB battery pack that supplies 5 volts to the Raspberry Pi.
Saint Gobain BCF-12 plastic scintillating fibers were used. The fast decay time (3.2 ns) allows
for accurate location determination by measuring the difference in time of arrival of the light
from an event at the two PMTs. The attenuation length of 2.7 m allows the use of fibers up to
approximately 10 m in length while still maintaining good sensitivity. The double-clad version
of the fiber is used to increase the light trapping efficiency. A bundle of seven 2-mm diameter
fibers is used to increase the sensitivity to gamma rays. The bundle is enclosed in heat shrink
tubing to prevent light from getting to the fibers. The tubing is thin enough to allow beta
particles to be detected by the system.
Hamamatsu 10721P-210 PMT modules are used. The modules require only 5 volts to operate,
obtained from a USB port on the Pi. The high voltage for the PMTs is provided by the PMT
modules and set using potentiometers inside the PMT mounting boxes. The voltages have been
set, and it is not recommended to change them. For users experienced with electronics, the PMT
supplies 1.2 volts on the blue line as a reference, and the potentiometers are used to supply a
voltage between 0 and 1.1 volts to the PMT on the white line, which sets the HV. Do not set the
voltage to greater than 1.1 volts. Do not operate the PMTs while exposed to light as permanent
damage will result. These modules were selected due to their high quantum efficiency and very
low dark count rate, both of which are important due to the small signals generated at the ends of
a long fiber.
The DRS4 demonstration board is a four-channel oscilloscope capable of sampling at 5 Giga-
samples per second (GSPSs), although this system uses it at 4 GSPSs. The high sampling rate is
critical to accurately determine the location of an interaction. The software to run the
oscilloscope is available at the DRS4 website: https://vvvvvv.psi.ch/drs/softvvare-dovvnload (last
accessed October 2017). The data acquisition is based on version 5.0.6. The make file has been
modified to remove the requirement for wxWdigets, which is not used on the current system.
One limitation of the DRS4 demo board is a maximum count rate of approximately 500 counts
per second. This rate can be exceeded with sources greater than approximately 100 |iCi, and the
dose rate response would then become non-linear. This limitation could be compensated for in
future versions, or a different hardware solution could be used.
The Raspberry Pi 3 is a very common single board computer. The operating system is run from
a microSD card. The usual operating system is Raspian, a variant of Linux based on Debian
Linux. The Raspberry Pi 3 has on board WiFi, which is utilized here to communicate with a
tablet (the Pi acts as an access point). It also has four USB ports and an HDMI port for a
monitor. With a keyboard, mouse, and monitor connected to it, the Pi acts like any other
computer.
30
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Power is from a USB battery pack. This battery pack requires a push of a button before
providing power. Any USB battery pack should work. The current pack provides approximately
eight hours of operation. Note that the battery pack cannot charge and provide power at the same
time.
The tablet is a Samsung Galaxy Tab S2 running Android. Other Android tablets should work as
well. Android versions between 4.4 and 6 are required for the EPAFiber tablet app. It might
work with version 7 of Android but has not been tested.
A.2 Operation
NOTE: The PMTs can be damaged permanently if power is supplied while the PMT is exposed
to ambient light. Ensure fibers are connected to both PMTs before supplying their 5 volt lines.
Direct exposure to sunlight, even while the PMT is not powered, can cause degradation in
performance. Additionally, PMTs are sensitive to magnetic fields, so magnets should be kept
away.
To turn the system on, first make sure all the necessary connections are made:
Connect the desired fiber bundle to both PMTs. For the 3-m and 10-m bundles which
have wires attached, the side with the short wires goes to PMT2, which is the PMT
located away from the rest of the system.
Connect the 5-volt power to both PMTs, which are provided via cables with BNC
connectors. The 5 volts is supplied by a USB to BNC adapter from the Raspberry Pi.
The signals from the PMTs are transmitted over coax using SubMiniature version A
(SMA) connectors. If using the 10-m fiber bundle, use the long (10 m) delay line to
connect PMT1 (the PMT closest to the oscilloscope) to channel 1 on the oscilloscope.
The delay line is required to allow the oscilloscope to detect coincidences over the entire
length of the fiber. For other fibers, use the short (18 inch) SMA cable to connect PMT1
to the DRS4.
Connect the DRS4 oscilloscope to the Raspberry Pi with a USB cable.
If desired, the Raspberry Pi can be connected to a keyboard, mouse, and monitor. This
connection is useful if collecting data from the system.
Connect the USB battery pack or wall power supply to the Raspberry Pi. If using the
supplied USB battery pack, you must press the button on the battery pack before it
supplies power.
The Raspberry Pi is configured to automatically start the data collection software on boot up,
which occurs when the Pi gets power. If the DRS4 is not connected to the Pi when the Pi is
turned on, the data collection software will quit. Turn on the tablet, which should automatically
connect to the WiFi of the Raspberry Pi. On the main page is an app called EPAFiber. Click on
the app. Go to the settings tab and select the cable you are using, then click on waterfall to go
back. Click on the Start button in the lower left corner and counts should start appearing.
The system occasionally freezes or doesn't start up properly. The simplest solution is to shut
down the Pi, remove power from the Pi for five seconds, and restart the system. More detailed
troubleshooting is below.
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Saving data from the system is more involved and requires the system be connected to a
keyboard, mouse, and monitor. Begin by ensuring the system is connected as above. The
Raspberry Pi runs a flavor of Linux, with a graphical user interface which is similar to other
operating systems. The actual commands will be entered via a command line in a terminal
window. The steps are listed next, with details following:
The system automatically starts a server process (called server) and data acquisition
process (called drsexam) at startup. Kill these processes for manual data collection.
o In a command line on the Pi, type ps -ef |grep drs exam
o Find the process number of drs exam (typically about 485)
o Type sudo kill 485 (or whatever the process number actually is)
Move to the directory Desktop/epastandalone.
o In a command line, type cd Desktop/epa standalone
Copy the setting file for the length fiber you are using to the file named DRS_settings.txt.
Use the command sudo ./drs exam to acquire data.
Data are saved in files named rawdata.csv and doserate.csv. If they are not renamed, they
will be overwritten.
A terminal window can be opened by clicking on the icon near the top right of the screen. The
files we care about are located in the folder /pi/users/pi/Desktop/drs.
Once data are collected in the files rawdata.csv and doserate.csv, they can be renamed using the
graphical user interface (or command line if you prefer). Then they can be copied to a USB flash
drive for analysis on another computer.
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vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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