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Forensic optically stimulated luminescence Technical findings of CRTI-02-0045RD Carey L. Larsson

Defence R&D Canada – Ottawa

Technical Report DRDC Ottawa TR 2010-098

July 2010

Forensic optically stimulated luminescence

Technical findings of CRTI-02-0045RD

Carey L. Larsson DRDC Ottawa

Defence R&D Canada – Ottawa

Technical Report DRDC Ottawa TR 2010-098 July 2010

Principal Author

Original signed by Carey L. Larsson

Carey L. Larsson

Defence Scientist / CARDS

Approved by

Original signed by Julie Tremblay-Lutter

Julie Tremblay-Lutter

SH / CARDS

Approved for release by

Original signed by Brian Eatock

Brian Eatock

Chair / DRP

This work was funded in part by the CBRNE Research and Technology Initiative (CRTI) under project CRTI-02-0045RD.

© Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2010

© Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2010

DRDC Ottawa TR 2010-098 i

Abstract …….

The CBRN Research and Technology Initiative funded project CRTI-02-0045RD to produce a prototype portable optically stimulated luminescence reader. That is, the project aimed to design, construct, and test a portable detector for measuring the stored radiation-induced signature in common building materials using the principle of optically stimulated luminescence. As such, a detailed characterization of many common building materials was also required. This prototype detector was successfully constructed and was field tested both at DRDC Ottawa and during CRTI Exercise MARITIME RESPONSE in Slemon Park, Prince Edward Island. The detector has always performed well, demonstrating a capability that heretofore has not existed in a portable device. The system has demonstrated the ability to detect past radiation exposures to materials including cement, concrete, drywall and ceramic tile, to name a few. The project team is currently pursuing the patenting and commercialization of this technology, and has received interest from outside the intended end-use community.

Résumé ….....

L’Initiative de recherche et de technologie CBRN (IRTC) a financé le projet IRTC-02-0045RD dans le but de produire un prototype de détecteur portable à luminescence stimulée optiquement. Il s’agissait de concevoir, de construire et de mettre à l’essai un détecteur portable destiné à mesurer la signature radioactive entreposée dans des matériaux de construction couramment utilisés, en utilisant le principe de la luminescence stimulée optiquement (LSO). À cette fin, une caractérisation détaillée de nombreux matériaux de constructions communs s’imposait. La construction du prototype a été menée à bon terme et l’appareil a été essayé en situation à RDDC Ottawa et durant l’exercice de l’IRTC appelé Exercice MARITIME RESPONSE, tenu à Slemon Park, à l’île-du-Prince-Édouard. Le détecteur a fonctionné correctement en tout temps, et il a donné une performance jusque-là inexistante pour un appareil portable. Le système a démontré la capacité de détecter la présence de matériaux ayant déjà été exposée à la radiation, entre autres du ciment, du béton, des plaques de plâtre et des carreaux de céramique. L’équipe du projet s’attache à faire breveter et commercialiser cette technologie. Des manifestations d’intérêt ont été reçues par les communautés d’utilisateurs finals visées.

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DRDC Ottawa TR 2010-098 iii

Executive summary

Forensic optically stimulated luminescence: Technical findings of CRTI-02-0045RD

Carey L. Larsson; DRDC Ottawa TR 2010-098; Defence R&D Canada – Ottawa; July 2010.

Introduction or background: Project CRTI-02-0045RD “Forensic Optically Stimulated Luminescence” aimed to produce a portable detector that uses optically stimulated luminescence to assist law enforcement personnel in positively identifying previous locations of illicit radioactive material. The project was approved in April 2003, work began in September 2003, and project completion was set for March 2006 with a fully functional and tested field prototype. The project was extended to September 2006, mainly to permit more work on sample characterization and further refinement of the field prototype.

Results: The project achieved or exceeded all of its objectives within the scheduled time and budget. The field prototype has been demonstrated during field trials at DRDC Ottawa and elsewhere. During trials at DRDC Ottawa, the detector demonstrated the ability to detect a 30-second radiation exposure from a 10 mCi Strontium-90 beta source directly on a concrete floor, a feat which has never before been achieved.

Significance: This project has demonstrated the ability to detect past radiation storage locations for forensic purposes, a heretofore non-existent capability in radiation detection. This capability also has application in a number of areas related to radiological defence and counter-terrorism, including nuclear weapons safeguards verification and retrospective dosimetry.

Future plans: Members of the project team have submitted a Letter of Invention as a first step in achieving a provisional patent of the portable OSL reader. Meetings have been held with representatives from the International Atomic Energy Agency (IAEA) to explore the applicability of the device for arms control inspectors, resulting in great interest. A Technology Acceleration proposal has been submitted to CRTI for the purpose of furthering the technology towards commercialization.

iv DRDC Ottawa TR 2010-098

Sommaire .....


Carey L. Larsson; DRDC Ottawa TR 2010-098; R & D pour la défense Canada – Ottawa; Juillet 2010.

Introduction ou contexte: Le projet IRTC-02-0045RD, « Utilisation à des fins judiciaires de la luminescence stimulée optiquement » avait pour but de produire un détecteur portable dont le fonctionnement repose sur le principe de la luminescence stimulée optiquement (LSO), pour aider le personnel responsable de l’application de la loi à identifier avec certitude d’anciens sites d’entreposage de matières radioactives illicites. Le projet avait été approuvé en avril 2003 et les travaux ont commencé en septembre 2003. Initialement fixée pour mars 2006, où devait être fourni un prototype éprouvé, entièrement fonctionnel et utilisable sur le terrain, la date d’achèvement du projet a été prolongée jusqu’en septembre 2006, surtout pour la poursuite des travaux sur la caractérisation des échantillons et pour apporter d’autres perfectionnements au prototype utilisable sur le terrain.

Résultats: Tous les objectifs du projet ont été atteints ou dépassés. Le calendrier d’exécution et le budget ont été respectés. Des essais de rendement du prototype utilisable sur le terrain ont été menés en situation à RDDC Ottawa et ailleurs : l’appareil a pu détecter une exposition de 30 secondes d’une source de bêta (Strontium-90) de 10 mCi directement sur un plancher en béton, une performance jamais réalisée auparavant.

Importance: Ce projet a démontré la capacité de détecter, à des fins judiciaires, les sites ayant déjà servi au stockage de matières radioactives, capacité jusque-là inexistante. Cette capacité trouve également des applications dans des secteurs reliés à la défense radiologique, à la lutte contre le terrorisme, y compris la vérification des garanties contre la prolifération nucléaire et la dosimétrie rétrospective.

Perspectives: Des membres de l’équipe du projet ont soumis un Rapport d’invention, la première étape en vue d’obtenir un brevet provisoire pour le détecteur portable LSO. Des rencontres ont eu lieu avec des représentants de l’Agence internationale de l’énergie atomique (AIEA) pour explorer l’application de l’appareil au travail des enquêteurs en contrôle des armements, ce qui a suscité un grand intérêt à l’Agence. Une proposition d’accélération du progrès technique a été soumise à l’IRTC pour rapprocher la technologie vers la commercialisation.

DRDC Ottawa TR 2010-098 v

Table of contents

Abstract …….. ................................................................................................................................. iRésumé …..... ................................................................................................................................... iExecutive summary ....................................................................................................................... iiiSommaire ....................................................................................................................................... ivTable of contents ............................................................................................................................ vList of figures ............................................................................................................................... viiList of tables ................................................................................................................................ viiiAcknowledgements ....................................................................................................................... ix1 Introduction............................................................................................................................... 1

1.1 Radiological Terrorism and Radiation Detection .......................................................... 11.2 Optically Stimulated Luminescence.............................................................................. 11.3 Previous Work in OSL .................................................................................................. 2

2 Project Description ................................................................................................................... 43 Scientific Results ...................................................................................................................... 5

3.1 Instrumentation Development ....................................................................................... 53.1.1 Laboratory Prototype ...................................................................................... 53.1.2 Commercial OSL Reader ................................................................................ 73.1.3 Portable Field Prototype.................................................................................. 8

3.2 Sample Characterization.............................................................................................. 103.2.1 Measurements with the Laboratory Prototype .............................................. 103.2.2 Measurements with the Risø Laboratory Reader .......................................... 153.2.3 Measurements with the Portable Field Prototype ......................................... 17

3.3 Field Trials .................................................................................................................. 194 Conclusions and Future Direction .......................................................................................... 21References ..... ............................................................................................................................... 23Annex A ..Portable FOSL Prototype User Manual....................................................................... 25

A.1 Connect RS232 Cable.................................................................................................. 25A.2 Turn on FOSL device .................................................................................................. 25A.3 Turn On data acquisition program............................................................................... 25A.4 Setting up PMT............................................................................................................ 25A.5 Setting up Run Time.................................................................................................... 25A.6 Setting up LED Intensity ............................................................................................. 26A.7 Operation Control Buttons .......................................................................................... 26A.8 FOSL Date Graphical Display..................................................................................... 27A.9 Save and Retrieve Current Setting............................................................................... 27A.10 Retrieve Data File........................................................................................................ 27

vi DRDC Ottawa TR 2010-098

A.11 Exit Application........................................................................................................... 27List of symbols/abbreviations/acronyms/initialisms .................................................................... 29Distribution list ............................................................................................................................. 30

DRDC Ottawa TR 2010-098 vii

List of figures

Figure 1: Schematic representation of TL and OSL processes........................................................ 2

Figure 2: Laboratory prototype OSL reader. ................................................................................... 5

Figure 3: The OSL spectrographic detection system setup. ............................................................ 6

Figure 4: The OSL photon counting detection system setup........................................................... 7

Figure 5: Risø fully automated TL/OSL reader used in the laboratory. .......................................... 7

Figure 6: Mechanical structure of the portable FOSL field instrument........................................... 8

Figure 7: Cut-away view of the portable FOSL field instrument. ................................................... 8

Figure 8: Display of the data acquisition interface.......................................................................... 9

Figure 9: Portable OSL reader and laptop for on-site analysis...................................................... 10

Figure 10: Comparison of OSL emissions from salt using red and green stimulating light.......... 12

Figure 11: Sample to sample variation for four samples of table salt given a 100 mGy dose. ..... 13

Figure 12: Repeated OSL spectrum of irradiated table salt........................................................... 14

Figure 13: OSL reader sample holder showing a cell phone resistor on the left, and a salt sample on the right. ..................................................................................................... 15

Figure 14: OSL signal sample-to-sample variability for unirradiated (left) and irradiated (1.4 Gy, right) samples. ...................................................................................................... 16

Figure 15: OSL signal variability for 10 samples given a 1.4 Gy dose to brick (left), ceramic tile (middle), and sand (right)...................................................................................... 16

Figure 16: OSL signal sensitivity for salt (left) and clay pot (right). ............................................ 17

Figure 17: Direct measurement of OSL signal from drywall (left), cement patio stone (middle), and ceramic tile (right). ............................................................................... 18

Figure 18: Direct measurement of OSL signal from concrete wall (left) and concrete floor (right)........................................................................................................................... 18

Figure 19: Field trial of portable FOSL prototype during Exercise MARITIME RESPONSE. ... 19

Figure 20: Direct measurement of OSL signal with the portable FOSL prototype from drywall during Exercise MARITIME RESPONSE. ................................................................ 20

viii DRDC Ottawa TR 2010-098

List of tables

Table 1: Initial material characterization with the laboratory OSL prototype............................... 11

Table 2: Minimum detectable doses for various OSL emitting materials. .................................... 17

DRDC Ottawa TR 2010-098 ix

Acknowledgements

The author would like to acknowledge Staff Sergeant Carl McDiarmid of the Royal Canadian Mounted Police and Mr. Tim Patraboy of Public Safety Canada for their contributions to this project. Without their guidance on relevant forensic scenarios and prospective uses of this technique, this project would have suffered. The author would also like to acknowledge the scientists at Bubble Technology Industries for their significant efforts on this project. Finally, this project could not have been possible without funding from the Chemical, Biological, Radiological, and Nuclear (CBRN) Research and Technology Initiative (CRTI).

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DRDC Ottawa TR 2010-098 1

1 Introduction

1.1 Radiological Terrorism and Radiation Detection

Radiological terrorism is increasingly becoming an item of concern to Canada and its allies. This type of terrorism might include the use of an improvised or acquired nuclear device, an attack on a nuclear facility to cause the release of radioactive material, or the use of a radiological dispersal device (RDD) or a radiological exposure device (RED). As such, much attention has recently been focused on the illicit acquisition of radioactive or nuclear material by terrorist organizations. The ability to detect and attribute this material before its use would therefore be desirable to the policing community. However, effectively all available radiation detection equipment requires close proximity to the physical location of the source in order to measure the emitted radiation. Thus the simple act of periodically moving a source will confound existing detection techniques.

Field detection of past radiation exposure in the absence of any radioactive material at the time of measurement is not an unattainable goal. Currently available passive radiation detectors or dosimeters collect exposure information over time and are periodically sent to a laboratory for read-out to assess past exposures. However, the materials used in these detectors are specially designed for increased sensitivity, low fading, and high repeatability; furthermore, the laboratory equipment used to read out the dose information are typically cumbersome bench-top devices.

Many natural materials are known to store radiation exposure information, including quartz, sand, feldspar, porcelain, alumina, sodium chloride, and tooth enamel. These materials have been studied for retrospective dosimetry following the nuclear weapon attacks on Hiroshima and Nagasaki, as well as after the Chernobyl reactor release. Such materials have also been analysed for geological and archaeological dating. With this in mind, DRDC Ottawa performed some in-house research and development and proposed applying the technique, known as Optically Stimulated Luminescence (OSL), to the field of forensics. In 2003, DRDC Ottawa applied to the Chemical Biological Radiological and Nuclear (CBRN) Research and Technology Initiative (CRTI) for funding to develop a portable detector capable of measuring radiation exposure in such ubiquitous materials in the field. This proposal was approved as CRTI project CRTI-02-0045RD [1].

1.2 Optically Stimulated Luminescence

Many ubiquitous materials have electron-trapping levels that become populated when exposed to ionizing radiation. Electrons can remain trapped following the removal of the source and may subsequently be de-trapped via optical pumping, releasing luminescence. The intensity of the released luminescence is proportional to the radiation dose originally imparted in that material. Detection of this emitted light may be used to confirm the previous location of a radioactive source. This radiation-induced charge storage and subsequent release with light is the basis of optically stimulated luminescence (OSL).

The underlying physics of optically stimulated luminescence is depicted in Figure 1. When an insulator or semiconductor material is irradiated, valence electrons are ionized, creating electron-hole pairs [2]. Naturally occurring defects in the material can trap the free electrons and holes,

2 DRDC Ottawa TR 2010-098

which may remain stored in the traps for a time that depends on the localized energy depth of the trap. When the irradiated material is subsequently illuminated, the trapped electrons absorb energy, causing a transition from a trap into the de-localized conduction band. Relaxation of the freed electron can result in recombination with localized holes resulting in photon emission and luminescence. The intensity of the emitted luminescence is proportional to the radiation dose absorbed by the material.

Figure 1: Schematic representation of TL and OSL processes.

1.3 Previous Work in OSL

OSL has several conventional applications including geological and archaeological dating, retrospective dosimetry and personnel dosimetry. In personnel dosimetry, a radiation dose is imparted from some occupational exposure [3]. OSL is used in much the same manner as in thermo-luminescence (TL) dosimetry to quantify the exposure, with the exception that light is used to release the trapped charge instead of heat. These techniques use synthetic dosimeters that are worn by radiation workers for a set period of time and are subsequently read-out at a laboratory to assess the extent of exposure.

In geological and archaeological dating, a radiation dose is imparted to the material by natural background radiation over the lifetime of said material [4]. With knowledge of the natural background dose rate and the total dose as measured by OSL, the age of the material can be determined, where the age is the time since the material was last exposed to light.

L L L

T T TE

Light

Lightor

heat

(i) Ionization (ii) Storage (iii) Emission

A C A

CONDUCTION BAND


In the case of retrospective dosimetry, a radiation dose is imparted to the material by some radiation accident, such as the nuclear weapon attacks on Hiroshima and Nagasaki, or after the Chernobyl reactor release [5]. In this type of situation, prompt assessment of the dose levels received by radiation workers and by the general population is important, despite the fact that conventional dosimeters were not in place at the time of the radiation exposure. In these situations, the OSL signal from building materials such as concrete or mortar is measured with the goal of determining population doses.

The application of OSL to forensics is a new idea. While the use of common materials to assess the dose imparted to a material via OSL has been identified as a challenge, it is important to realize that the goal of this project is not to quantify an exact dose, but simply to qualify that a material has been in the presence of radiation. This differentiation significantly reduces sample-to-sample variation and calibration issues, thus making the goal much more manageable. Furthermore, this simplified approach is within reason, since a radioactive source of sufficient strength to cause worry would certainly impart a dose to the countertop is rested on (for instance) well above the natural background dose of a similar material not in contact with the source. With that said, many of the doses measured for retrospective dosimetry also use OSL signals from similar common materials and a detailed dose assessment is possible in laboratory conditions. Thus some combination of signal from a portable reader in the field with a laboratory assessment of a sample should provide sufficient forensic value to an investigation.


2 Project Description

The project was managed by DRDC Ottawa, with Bubble Technology Industries (BTI) as the prime contractor. This means that DRDC Ottawa was responsible for preparing all project management documentation, such as the project charter. It also means that DRDC Ottawa was responsible for satisfying CRTI project reporting requirements and for managing the CRTI funds supplied to the project. BTI was responsible for doing most of the research and development of this technology. DRDC Ottawa and BTI were jointly responsible for testing the various laboratory and field prototype detectors, making use of DRDC Ottawa’s inventory of radiation sources and laser laboratory. The Royal Canadian Mounted Police (RCMP) and Public Safety Canada (PSC) were also partners on the project. Both were responsible for coordinating and performing system testing and ensuring relevance of the project to forensic needs.

The goal of the project was to produce a fully functional and field-tested prototype OSL reader. The project plan was relatively simple, broken down into three phases. The first phase set out to perform a thorough examination of the relevant literature (i.e. OSL used for other purposes) to give preliminary guidance on materials and optimization techniques. Using these results, a list of materials amenable to OSL was established and an optimum laser/detection system was investigated.

The second phase of the project was focused on the design, construction and testing of a laboratory prototype OSL system. BTI and DRDC Ottawa worked on the physical principles of detector operation and RCMP and PSC ensured that the field operation needs were considered. Testing then served to optimize technical and operational parameters.

The third and final phase of the project, as originally proposed, was concentrated on the construction and testing of the portable field prototype forensic OSL reader. RCMP and PSC input their design requirements, and testing of the device by DRDC Ottawa and BTI at DRDC Ottawa ensued. This was to be followed up with a final series of “tweaking” procedures necessary to optimize the performance of the field instrument.


3 Scientific Results

3.1 Instrumentation Development

3.1.1 Laboratory Prototype

A laboratory prototype OSL reader was designed and tested before developing the portable field detector. The lab prototype could be fitted with either a spectrograph and CCD camera combination or with a photomultiplier tube (PMT) for readout of the OSL signal. A cross-sectional cut of the laboratory prototype OSL reader is shown in Figure 2. Laser light is directed through an opening in the top of the reader, through a small hole in the mirror, passed through a condenser lens and focused on the sample location. Both a Verdi V-5 diode-pumped 532-nm green laser and a Model 900 Mira tuneable (710 to 1000 nm) red/infrared laser (Coherent, Santa Clara, CA) have been used for sample stimulation with power settings variable from 0.01 – 5.0 Watts for the green laser and from 0.01 – 1.0 Watts for the red laser. Upon stimulation, the luminescence emitted from the sample passes through the condenser lens, is reflected off the mirror, passes through focusing lenses and light filters and exits the reader for detection by either the spectrograph and camera or by the PMT. The reader is made of black anodized aluminium and the sample holder is a stainless steel rod fitted with removable black Delrin sample trays.

Figure 2: Laboratory prototype OSL reader.


As mentioned, two different detection systems may be used with this reader. The spectrograph/camera combination is shown in Figure 3. A SpectraPro-150 imaging dual grating monochromator/spectrograph (Acton Research Corporation, Acton, MA) is fitted to the reader at the filter-holder end. Luminescence emitted from the sample enters the spectrograph, the light is separated by wavelength and is then viewed by a 4 Quik E intensified CCD camera (Stanford Computer Optics, Inc., Palo Alto, CA). This setup allows for spectral information about the emission to be obtained at the expense of a fairly low sensitivity. The camera is linked to a desktop PC via a frame grabber. During a measurement, 60 video fields are captured and retained by the PC per second, and the brightness or intensity of the light in each field is calculated and displayed for each video field. By plotting the intensity versus wavelength, a qualitative assessment of whether a dose was imparted to the material can be made.

Figure 3: The OSL spectrographic detection system setup.

The photon-counting system is shown in Figure 4. A two-inch photomultiplier tube is fitted to the reader at the filter-holder end. Luminescence emitted from the sample is recorded by the PMT and read by a digital oscilloscope. This setup provides greater sensitivity than the spectrograph/camera configuration, but the dynamic range is limited by the counting electronics and PMT response. The PMT was initially operated in pulse-mode, however, problems with dead-time losses and PMT saturation were observed for strongly luminescent samples. Switching PMT operation to current-mode has removed the dead-time effects, but PMT saturation can still pose a problem if the OSL signal is very large. Care must be taken to ensure that the gain settings are initially set low and slowly increased if necessary to avoid over-exposing the PMT.


Figure 4: The OSL photon counting detection system setup.

3.1.2 Commercial OSL Reader

A commercially-available fully automated TL/OSL reader, shown in Figure 5, was purchased from Risø National Laboratory in Roskilde, Denmark [6]. This reader has a 48-sample holder with blue and infrared light-emitting diodes (LEDs) for sample stimulation and an on-board 40 mCi strontium-90 beta source for sample irradiation. The accompanying software allows the user to devise a sample analysis sequence, view the resulting data and perform data analysis and interpretation. This reader was used in the laboratory for sample characterization and results comparison with the prototype laboratory and field OSL readers.

Figure 5: Risø fully automated TL/OSL reader used in the laboratory.


3.1.3 Portable Field Prototype

In some circumstances, analysis of suspect materials on location may be preferable to taking samples for laboratory analysis, particularly when many areas within a building need to be investigated. As such, a portable OSL reader has been designed with sufficient sensitivity for use in the field [7]. The mechanical structure of the portable FOSL field instrument is shown in Figure 6 and a cut-away view is shown in Figure 7.

Figure 6: Mechanical structure of the portable FOSL field instrument.

Figure 7: Cut-away view of the portable FOSL field instrument.

The FOSL optical system selected and constructed consists of a large area of several LED (470 nm) clusters for generating the stimulating light. The L470-02V super bright LED (by EPITEX) is used to build LED clusters. A 2”-diameter PMT is used for detecting OSL emission from the sample. Two U-340 filters are used in front of PMT (electron tube 9266KSB18) to pass luminescence in the region of 300-400 nm but reject light of other wavelengths. The stimulating LED light, passing through two GG420 filters, is focused on the sample by a lens of 38mm focal length. The GG420 filters remove the short wavelength of light emanating from the LEDs, which


can interfere with the detection of OSL but transmit the blue and green light efficiently. In order to maximize the collection of OSL signal, a parabolic reflector (PR) was employed in the optical system. Simulation, with the optical design code ZEMAX, shows an increase by a factor of three in luminescence signal when a PR is located around the sample.

Two lithium-cell batteries, which must be removed to facilitate recharging, provide power for the device while in the field. A power adapter using 110VAC is provided for laboratory operation. The PMT high voltage, power for the LED cluster, signal processing, and counting electronics are all controlled by the micro-controller. This controller also monitors the battery level and displays it for user reference. The signal from PMT is amplified and converted to logic pulses with a lower level discriminator, and then input to the counter.

The data acquisition window using a PC or laptop is displayed in Figure 8. Serial communication protocol is employed between the PC and the device. The user controls the OSL measurement through a user interface on the PC. These controls include:

the start/stop of the data acquisition system;

data saving and retrieval;

PMT high voltage (useful when the OSL intensity is very bright);

the number of LED clusters engaged in the measurement;

the scalar channel duration (minimum channel width is 5 ms); and

the total measuring time.

In addition, there is also provision for data overlay and printing of figures.

Figure 8: Display of the data acquisition interface.


The final device is shown in Figure 9. Analysis can be performed either by placing a small sample of the material into the sample chamber, or by replacing the base of the reader with a “direct-read base” and performing direct measurements of suspected areas. The latter method requires that the OSL reader be placed in direct contact with a flat surface of the material in question to prevent light leakage during analysis. This method provides a means of covert analysis, since a sample of the material does not need to be removed. Analysis using the direct-read approach will also be more effective in low-light areas than in areas of high light, since ambient room light depletes the signal over time. The portable FOSL prototype user manual can be found in Annex A.

Figure 9: Portable OSL reader and laptop for on-site analysis.

3.2 Sample Characterization

3.2.1 Measurements with the Laboratory Prototype

Initial survey measurements with the laboratory prototype investigated the OSL properties of a variety of common materials assumed to be relevant to a forensic investigation. Control materials included a variety of TLD materials, including Al2O3:C, LiF:Ti, LiF:Cu Mg P, CaF2:Mn,Li2B4O7:Mn. Sample materials varied from common building materials, such as brick, concrete, granite, paint, cedar, shingles, and drywall, to other household items such as salt, detergent, sugar, and sand. This project has thus far focused on the characterization of the detector and signals from these sample materials. Emission of luminescence has been observed in the blue and red wavelength regions. The most common wavelength for emission, however, is in the blue. Table 1 lists the array of materials that have been investigated for OSL emission. Note that while measurements of some materials listed in Table 1, such as drywall and ceramic tile, did not reveal OSL in this initial assessment, an OSL signal was ultimately detected from these samples with the FOSL reader, described later in this report, due to the significantly higher detection and stimulation efficiency provided by that instrument.


Table 1: Initial material characterization with the laboratory OSL prototype.

MaterialGreen LASER, blue emission

Green LASER, red emission

Red LASER, blue emission

Al2O3:C (TLD500) Yes Yes - LiF:Cu Mg P (TLD700H) Yes - - CaF2:Mn (TLD400) Yes - - LiF:Ti (TLD600) Yes - - CaF2:Tm (TLD300) Yes - - LiF:Mg(TLD100H) Yes - - 6LiF:Mg Cu P (TLD GR206A) Yes - - Li2B4O7:Mn (TLD800) No - - Table salt Yes Yes Yes De-icing salt Yes Yes - Concrete foundation Yes No No Cement mix Yes Yes Yes Feldspar Yes Yes Yes Scapolite Yes - Yes Sand Yes Yes Yes Brick Yes No - White gardening stone Yes No No Dish detergent Yes Yes Yes Patio stone No Yes - Gravel No Yes No Granite No No - Lime (CaCO3) No No - Drywall No Yes No Roofing shingle No No - Hand soap No - - Sugar No No No Paint No No - Ceiling tile No No - Wood (cedar) No No - Linoleum No No - Low-density plastic No No - High-density plastic No No - Ceramic pot No No - Ceramic floor tile No Yes - Cardboard No - - Baking powder No - No Corn starch No - No Baking soda No - No Flour No - - Acetaminophen No - No Pink ornamental rock No No - Fingernails No No No Hair No No -


Although less than half of the materials investigated yielded a detectable OSL signal, many of those that did emit OSL are relevant to a forensic investigation. For instance, materials such as brick, concrete, cement, and sand are likely to be present in a building in which a terrorist may be harbouring an illicit source. The OSL-emitting materials identified therefore provide a positive starting point for this project.

There were three different kinds of red luminescence emitted from the assortment of materials investigated. The most common emission was a large red fluorescence that nearly every material exhibited. This fluorescence was very bright (visible to the naked eye) and did not decay away during stimulation. The second type of red emission occurred when materials containing alumina (Al2O3) were stimulated with the laser. These materials were found to emit in a narrow band at 690 nm, which is the wavelength associated with a ruby laser. While unexpected, this phenomenon can be explained by the fact that ruby is composed of mainly alumina doped with chromium, and thus we are simply seeing the laser emission typically seen from ruby stimulation. The third type of red emission was seen only from a select number of materials. This emission does decay; however, it is not a dose-dependent emission, as unirradiated and irradiated materials exhibit equivalent amounts of signal. These materials will also often exhibit blackbody luminescence indicated by a grow-in of signal due to heating of the sample by the laser. Since none of these emissions are dose-dependent, the red emissions will be filtered away in order to improve sensitivity to the blue emissions.

Several materials emit OSL when stimulated with red laser light, as shown in Table 1. However, the intensity of the signal for these materials was significantly less than that from green laser stimulation, shown in Figure 10. It is widely known in the geological OSL field that red light will stimulate OSL emissions from feldspar (the most abundant constituent of rocks on earth) but not from quartz (the second most abundant) [8]. The main advantage of using red laser stimulation will be for materials that contain both quartz and feldspar, such as sand, allowing for stimulation of the feldspar only. This prevents OSL emissions from multiple materials, making the analysis of the signal less complicated.

Figure 10: Comparison of OSL emissions from salt using red and green stimulating light.


The sensitivity of the laboratory OSL prototype was found to be dependent on the sample material being investigated. Doses as low as 1 mGy are observable for Al2O3:C and table salt, while detectable signals are seen in sand, cement mix and feldspar given a dose of 1 Gy. Sample-to-sample variability remains an issue to be sorted out. For instance, in samples of salt and cement mix the detected signal can vary from nothing to very large for samples given equal doses and using equal laser power. It is likely that the laser is stimulating grains of varying opacity or of different materials, or that it is simply hitting only partial grains from measurement to measurement, resulting in differing signals. This effect would be difficult to eliminate entirely; however, repeated measurements would provide a means to determine if a dose-dependent signal were indeed present.

In performing measurements with the laboratory prototype using the PMT setup, variability of both background signal and peak shape was observed for a given material. In repeated measurements of a material given equal doses of gamma radiation, the background signal varied by as much as a factor of five. Even unirradiated materials exhibited background variations. While the amount of background light was reduced somewhat by blocking a light leak around the filter holder, about 2% of the incident laser light was reflected towards the detector by the surfaces of the condenser lens. Attempts to circumvent this lens were made, resulting in reduced signal intensity and thus it was determined to instead add another BG12 filter and a #51311 blue-pass filter to reduce background levels to a negligible amount. The sample-to-sample variability, however, has not been explained at this time. This effect is exhibited in Figure 11.

Figure 11: Sample to sample variation for four samples of table salt given a 100 mGy dose.

There was also a significant variation in the peak shape for repeated measurements of the same material given the same dose. It was observed that when a low intensity laser power is used for stimulation, the OSL emission is a small-amplitude, long-tail signal. Conversely, when a high intensity laser power is used, a large-amplitude, short-tail signal is seen. While it is expected that the OSL yield should be independent of laser power, a possible explanation is that these


observations are related to thermal heating of the sample by the higher laser power, thereby altering the peak shape of the OSL emission. This problem leads to poor repeatability and limits the sensitivity of dose determination. Optimization of the laser power settings is required for different materials. Switching to a lower-power stimulation light source, such as an LED, was also considered for the field prototype.

OSL emission, when stimulated by a constant light source, decays with time, reflecting the depletion of trapped electrons in the sample. As such, repeated OSL measurements of the sample sometimes yields a significant, though smaller, signal, as shown in Figure 12. The trace marked “2nd laser stimulation” was acquired several seconds after completion of the first stimulation. The trace marked “3rd laser stimulation” also followed the second by several seconds. The presence of residual OSL light after thorough bleaching in the first OSL stimulation is due to the effect of shallow traps in salt. Some electrons excited out of the deep traps in the first stimulation fall into these shallow traps from the conduction band during the bleaching process and are subsequently excited by thermal energy to the conduction band and transition back to the original deep electron trap when the OSL stimulation stops. These electrons are then available to contribute OSL in a subsequent stimulation. Even the third stimulation shows a small residual OSL signal.

Figure 12: Repeated OSL spectrum of irradiated table salt.

These initial measurements performed with the laboratory prototype highlighted some general OSL characteristics of natural samples, including:

Many candidate samples can be reduced to a granular form that provides a large surface area for OSL stimulation and emission.

Many candidate samples are also opaque and are self-occluding. They are unsuitable for OSL stimulation/emission;

Many candidate samples are available in copious quantities.


These observations lead to the definition of several design requirements for the portable field prototype. This prototype should accommodate large quantities of granular samples by uniformly illuminating a thin layer of this sample and efficiently collecting its OSL emission. The stimulating light source should be bright and uniformly illuminate the distributed sample in a narrow colour band that does not interfere with the detection of the OSL light but yet provides adequate OSL stimulation. Although laser light occurs in a narrow wavelength window that does not interfere with OSL emission, it is generally unsuitable for OSL stimulation because it cannot uniformly illuminate large distributed samples. This suggests the use of arrays of blue/green LEDs as an OSL stimulant. These design requirements were incorporated into the portable field prototype, described above.

3.2.2 Measurements with the Risø Laboratory Reader

During the design and construction of the portable field prototype, the radiation-dependent OSL emissions from several relevant materials were re-assessed with the Risø laboratory reader. Sample characterization focused on repeatability of measurements, minimum detectable doses, and the degree of signal fading over time. Sample holders for the Risø laboratory reader (stainless steel disk) placed in the sample holder of the portable OSL reader (black anodized aluminum) are shown in Figure 13 with a typical cell phone component sample and a salt sample that was analyzed. The samples of the majority of other materials analyzed were in powdered form, and in similar quantity to that of the salt sample.

Figure 13: OSL reader sample holder showing a cell phone resistor on the left, and a salt sample on the right.

Assessment of sample-to-sample variability was performed with the Risø laboratory OSL reader. Twenty unirradiated samples of similar weight and appearance were loaded into the reader. The OSL signal of ten of these samples was read using blue LED stimulation, while the remaining ten were irradiated using the on-board beta source to a dose of 1.4 Gy before reading the OSL signal. Figure 14 displays the weight-normalized data spread for each material at one time point (t = 0s), with the thick bars representing one standard deviation of the ten measurements and the thin line showing the range of high to low readings. The unirradiated samples typically show a larger standard deviation since the signals are quite low. However, for the irradiated samples, this figure shows that measurements of the signal from brick, ceramic tile, clay pot, detergent, drywall, and


salt all have good repeatability, as is evident from the small standard deviation in OSL signal for those materials. Figure 15 shows the signal variability for brick (left), ceramic tile (middle), and sand (right).

Figure 14: OSL signal sample-to-sample variability for unirradiated (left) and irradiated (1.4 Gy, right) samples.

Figure 15: OSL signal variability for 10 samples given a 1.4 Gy dose to brick (left), ceramic tile (middle), and sand (right).

Minimum detectable doses were qualitatively assessed for all OSL-emitting materials. Samples were placed in light-tight containers and given doses ranging from 1 mGy to 1.5 Gy using a 50 Ci cobalt-60 irradiator. The samples were then weighed into sample holders in a darkroom and loaded into the Risø laboratory OSL reader. Three repetitions of each material at every dose point were analyzed, and the results are shown in Table 2 below. Both salt and detergent are extremely sensitive to radiation, with 1 mGy doses easily detectable with the OSL technique. The other materials were not as sensitive. It should be noted, however, that with the exception of the cell


phone components many of the other materials have the potential to be in very close proximity to a radioactive source, and thus doses of more than 1 Gy would not take long to achieve, especially for activities of concern for radiological terrorism. Figure 16 shows the sensitivity curves for salt (left) and clay pot (right).

Table 2: Minimum detectable doses for various OSL emitting materials.

Material Minimum detectable gamma dose (mGy) Brick 750 Cell phone part 750 – 1000 Ceramic tile 100 – 500 Clay pot 500 Concrete 50 – 100 Detergent 1 – 5 Drywall 1500 Salt 1 Sand 500 – 750

Figure 16: OSL signal sensitivity for salt (left) and clay pot (right).

3.2.3 Measurements with the Portable Field Prototype

The portable OSL reader was assessed in trials at DRDC Ottawa using the direct read mode. In laboratory trials, the OSL signal was measured on the unirradiated surface of a piece of drywall, a cement patio stone, and a ceramic tile. A 10 mCi strontium-90 source was placed in direct contact with each surface for five minutes. The portable OSL reader was then placed in the general vicinity of where the source had been and the OSL signal was measured. Results for these three surfaces are shown in Figure 17. It is obvious that a radiation-induced OSL signature was measured from each material with sensitivities corresponding to those in Table 2.


During the same trials at DRDC Ottawa, shorter exposure times were also measured with the portable OSL prototype in the direct read mode. The OSL signal was measured on the unirradiated surface of a concrete floor and a concrete wall. A 10 mCi strontium-90 source was placed in direct contact with each surface for 1 minute. The portable OSL reader was then placed in the general vicinity of where the source had been and the OSL signal was measured. Due to the large signal measured from the concrete floor, the above procedure was repeated in a different location with an exposure time of 30 seconds. Results for these two surfaces are shown in Figure 18.

Figure 17: Direct measurement of OSL signal from drywall (left), cement patio stone (middle), and ceramic tile (right).

Figure 18: Direct measurement of OSL signal from concrete wall (left) and concrete floor (right).


3.3 Field Trials

Field trials of the portable OSL reader were performed during Exercise MARITIME RESPONSE (Figure 19). The setup and exercise scenario is described here. A small room with concrete floors and walls was used to simulate the basement of a house. Exercise designers irradiated a square of drywall to an unknown dose and placed it in the corner of the room. The response team was then told the scenario, which involved police having received intelligence of an individual suspected of planning a dirty bomb attack on a major city. Investigation of the individual’s apartment with radiation detection equipment turned up nothing and scientists were asked whether any they could determine if any had ever been stored there.

The response team, consisting of personnel from DRDC Ottawa and Director General Nuclear Safety (DGNS), used the OSL reader to analyze concrete and drywall surfaces in different locations throughout the room. A small signal was detected from drywall, as shown in Figure 20. No significant signal was detected from the concrete walls or floor. It should be noted that the small detected signal from the drywall sample was not initially recognized as a positive signal, since the peak was not very large. It was only when the measurements were plotted against the background measurement that the positive result was recognized.

Figure 19: Field trial of portable FOSL prototype during Exercise MARITIME RESPONSE.


Figure 20: Direct measurement of OSL signal with the portable FOSL prototype from drywall during Exercise MARITIME RESPONSE.


4 Conclusions and Future Direction

The project has produced a prototype detector that has demonstrated the ability to detect past storage locations of radiological materials in the field with a portable detector. The sensitivity of the portable FOSL device is very high, and at least comparable to a leading commercial OSL reader. This is a remarkable accomplishment, given that almost all conventional radiation detectors require real time proximity to the source in order to detect its presence, and it represents a novel capability within the forensics community. This device also has applications in other areas, including arms control verification and public dosimetry estimation for emergency response.

While the portable FOSL detector has been a great success, there are a number of items that could certainly be improved if this detector were to be re-built, or if other similar portable OSL detectors were to be built in the future. Follow-up work must yet be done to define the various protocols that are needed in order for different groups to use the technology effectively. This work needs much input from the ultimate end-users, who are the only ones that know how they might utilize this novel technology. Some items identified as requiring improvement are outlined here.

During field trials, it was identified that the detector needed to be made more robust and its usability needed improvement. For example, the current prototype requires the user to use one hex key to remove ten screws in order to replace the battery, and two other hex keys to change between the two bases (i.e. the sample base and the direct read base). Simplification of these tasks by removing the need for tools is a major requirement. Furthermore, supplying adequate packaging of the entire system for easy transportation, for example using a customized Pelican Case, is a must.

Performing a direct measurement of a vertical surface with the current detector design is very awkward due to the weight of the detector and the requirement that no light enter the detector during the reading (to prevent overexposure of the PMT). As such, improvement of the design to allow for easier use on both horizontal and vertical surfaces, including, for example, adapters for the analysis of curved surfaces and for the analysis of small samples, would be helpful. Keeping the detector weight below some reasonable level would also help to alleviate this problem.

Improvements to the software associated with the detector could potentially improve detector functionality for different applications. Software that provides for easy operation by non-scientific or technical users via simple, easy to remember, and logical interfaces would make the instrument practical for use by a variety of end users with varying levels of expertise. Software that allows for luminescence characterization of unknown materials with the use of an external radiation source (i.e. having an optional x-ray tube available as an add-on to the detector system) would improve the quality of data obtained in field operations. This feature would reduce the requirement of having an associated OSL laboratory for more detailed measurements. Furthermore, adding the ability for wireless communication between the system control unit (i.e. a laptop) and the detector would improve device usability.

The portable FOSL device is relevant to different applications, including forensics, arms control verification, and public dosimetry estimation for emergency response. As such, development of a


single detector that meets the requirements for all applications would be worthwhile. For this to be achieved successfully, accompanying documentation would need to be thorough and clear, and include technical specifications of the system, operating manuals, and maintenance and troubleshooting manuals. A training program would also need to be established.

Many of these items could be addressed in a follow-on CRTI Technology Acceleration project. Such a project should focus on detector and software improvements, documentation development, and further sample characterisation to ensure that materials relevant to the expanded end-use communities are included.


References .....

[1] Cousins, T. (2003). Project Charter CRTI-02-0045RD Forensic Optically Stimulated Luminescence. Defence R&D Canada.

[2] Bøtter-Jensen, L., McKeever, S.W.S, Wintle, A.G. (2003). Optically Stimulated Luminescence Dosimetry. Elsevier, New York.

[3] Akselrod, M. S., McKeever, S. W. S. (1999). A Radiation Dosimetry Method using Pulsed Optically Stimulated Luminescence. Radiation Protection Dosimetry 81, 167-176.

[4] Aitken, M. J. (1998). An Introduction to Optical Dating. Oxford University Press, Oxford.

[5] Bøtter-Jensen, L. (1996). Retrospective Radiation Dosimetry using Optically Stimulated Luminescence on Natural Materials and Ceramics for Assessing Population Doses in Nuclear Accident Areas. In: Walderhaug, T., Gudlaugsson, E. P. (Eds.), The proceedings of the Nordic Society for Radiation Protection Seminar, 26-29 Aug 1996, Reykjavik, Iceland. (Nordic Radiation Protection Society, Reykjavik, 1997) pp. 273 – 278.

[6] Bøtter-Jensen, L. (2000). Development of Optically Stimulated Luminescence Techniques using Natural Minerals and Ceramics, and their Application to Retrospective Dosimetry. Ph. D. Thesis, Copenhagen University.

[7] Bubble Technology Industries Inc. (2006). Forensic Optically-Stimulated Luminescence Final Report. (BTI-06/03-30). Bubble Technology Industries Inc.

[8] Aitken, M.J. (1990). Optical dating of sediments: Initial results from Oxford. Archaeometry 32 (19-31).


Annex A Portable FOSL Prototype User Manual

A.1 Connect RS232 Cable

Connect the RS-232 cable between the FOSL device control panel and the laptop or PC.

A.2 Turn on FOSL device

Turn on the FOSL device by pushing the power switch button to the right, the power LED should be on when the power is on. If the lithium battery cells fall below a certain voltage level, the PC will no longer communicate with the FOSL board and a message will be displayed indicating the battery voltage is low. Recharge the batteries must be taken.

If A/C power is to be used, user must connect the power input of the device to the output of the power adapter. The PC will recognize if a 24 VDC power supply is connected and display this information on the PC software interface.

A.3 Turn On data acquisition program

Turn on the laptop, click the FOSL short cut on the display window, the data acquisition software should be opened and appeared as the figure below. The user must set up running parameters for a meaningful run, as listed in step A.4 to A.6.

If you open the data acquisition program before the FOSL device is on, an error message will be displayed at the lower left corner: “Hardware initialization FAILED!”

A.4 Setting up PMT

Under Light Intensity Settings, Set up an appropriate voltage of PMT by dragging the PMT HV (%) button to the ideal position, marked by the number in the small window at the right end. This number is percentage of present voltage on PMT to 1800 volts. For example, the idea value for the PMT is 56, i.e., the voltage presented on PMT is 1008 volts (56% of 1800 V). The allowed voltage is from 0 to 1080 volts, less than the maximum 1100 volts in PMT specifications. Once the PMT is set, it will stay for continue runs.

A.5 Setting up Run Time

The Run Time Settings are located in the upper left corner of the Forensic OSL (V1.0) software interface. The Run Time Settings include both the Run Duration (in seconds) and the Bin Width (in milliseconds). The Elapsed Run Time is displayed throughout a run.

The Duration parameter ranges between a minimum of 0.1 seconds and a maximum of 10,000 Seconds. Furthermore, the Duration may be set in steps of 0.1 Seconds. It is important to note that


when modifying the Duration parameter, enter must be hit after typing in the new value; otherwise the value change will not take effect on the Forensic OSL hardware.

The minimum Bin Width parameter is 5 milliseconds. The Bin Width is automatically re-scaled to an appropriate value when the Run Time Duration parameter is modified. It is important to note that when modifying the Bin Width parameter, enter must be hit after typing in the new value; otherwise the value change will not take effect on the Forensic OSL hardware.

The Elapsed Run Time is displayed in Seconds on the Forensic OSL (V1.0) software interface. The Elapsed Run Time is displayed in increments of 0.1 Seconds.

The Bin Width and the Duration time cannot be modified while in the middle of the run. Once the run time is set, it will stay for continue runs.

A.6 Setting up LED Intensity

When powering up the FOSL board, all LED clusters are disabled.

Set up the stimulating light intensity by setting up LED Intensity located in the upper right corner of the FOSL software interface under Light Intensity Settings. The LED Intensity parameter may be set to a value between 0 and 6. A LED Intensity value of 0 signifies all LED Clusters are turned off and a value of 6 signifies that all LED Clusters are turned on (Maximum LED power). Once the LED is set, it will stay for continue runs.

A.7 Operation Control Buttons

The FOSL System operation control buttons are located in the bottom left corner of the FOSL software interface. The Interface Control Buttons include: Start, Stop, Save and Clear.

The Start Control Button begins an FOSL System Data Run. When selecting (by clicking) the Start Control Button, a description dialog box will appear and the user may either type in a description, notes, or just hitting enter to continue the FOSL Data Run. The FOSL System then initializes the hardware and a Data Run begins, the PMT and LED displaying LED at the front panel should be on.

The Stop Control Button may be used to stop an FOSL Run before the preset run time finishing. Upon selecting Stop (by clicking) the user is prompted with a Clear data dialog box. Selecting yes clears the data and no leaves the data displayed.

The Save Control Button allows the user to save an FOSL data in two separate files of binary and ASCII format, respectively. Upon selecting Save (by clicking), the user may save the file as automatically assigned file name using current date and the run number, or modify it by typing in a new name.

The Clear Control Button allows the user to clear the displayed data without saving at the end of an FOSL Run.


A.8 FOSL Date Graphical Display

The FOSL data Graphical Display plots Scaler Counts per Bin Width over the Duration of the Run. The Time axis is scaled according to the current Duration parameter. The Scaler Counts per Bin Width axis is Auto-Scaled according to the counts the remote PC receives from the FOSL device.

The Scaler Total is displayed along with the current Battery Level in the bottom right corner of the Forensic OSL (V1.0) software interface. The Scaler Total represents the total counts by the scaler during the FOSL run. The current Battery Level of the lithium Battery Cells is displayed. The FOSL System also displays whether the device uses A/C power or Battery on the display window.

A.9 Save and Retrieve Current Setting

In the File menu of the program, the Save Default Settings button allows the user to save the current hardware/software settings for later/subsequent use by using Use Default Settings button.

A.10 Retrieve Data File

The open and Open Multiple commands in the File menu, located at the upper left corner, allow the user to retrieve previous one or multiple FOSL Data files that have been saved using the Save Control Button, respectively, and display the measured curve or curves on the screen.

A.11 Exit Application

When the operation is finished, the FOSL data acquisition program can be closed by clicking on the Exit menu item in the File pull-down menu, or alternatively the Exit button at the upper right corner of the application menu.

Turn off the power, the power indicating LED should be off.


List of symbols/abbreviations/acronyms/initialisms

The following is a list of the symbols, abbreviations, and acronyms used in this document.

A/C Alternating Current BTI Bubble Technology Industries CBRN Chemical, Biological, Radiological and Nuclear CCD Charge-Coupled Device CRTI CBRN Research & Technology Initiative DGNS Director General Nuclear Safety DRDC Defence R&D Canada FOSL Forensic Optically Stimulated Luminescence FY Fiscal Year HV High Voltage IAEA International Atomic Energy Agency IRTC Initiative de recherché et de technologie CBRN LED Light-Emitting Diode LSO Luminescence stimulée optiquement OSL Optically Stimulated Luminescence PC Personal Computer PMT Photomultiplier Tube PR Parabolic Reflector PRC Project Review Committee PSC Public Safety Canada RCMP Royal Canadian Mounted Police RDD Radiological Dispersal Device RED Radiological Exposure Device RFP Request For Proposal TL Thermo-luminescence TLD Thermo-luminescence Dosimetry VAC Volts Alternating Current VDC Volts Direct Current

DOCUMENT CONTROL DATA (Security classification of title, body of abstract and indexing annotation must be entered when the overall document is classified)

1. ORIGINATOR (The name and address of the organization preparing the document. Organizations for whom the document was prepared, e.g. Centre sponsoring acontractor's report, or tasking agency, are entered in section 8.)

Defence R&D Canada – Ottawa3701 Carling AvenueOttawa, Ontario K1A 0Z4

2. SECURITY CLASSIFICATION(Overall security classification of the documentincluding special warning terms if applicable.)

UNCLASSIFIED

3. TITLE (The complete document title as indicated on the title page. Its classification should be indicated by the appropriate abbreviation (S, C or U)in parentheses after the title.)


4. AUTHORS (last name, followed by initials – ranks, titles, etc. not to be used)

Larsson, C.L.

5. DATE OF PUBLICATION(Month and year of publication of document.)

July 2010

6a. NO. OF PAGES (Total containing information, including Annexes, Appendices, etc.)

44

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8

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Technical Report

8. SPONSORING ACTIVITY (The name of the department project office or laboratory sponsoring the research and development – include address.)

Defence R&D Canada – Ottawa3701 Carling AvenueOttawa, Ontario K1A 0Z4

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CRTI-02-0045RD

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10a. ORIGINATOR'S DOCUMENT NUMBER (The official document number by which the document is identified by the originating activity. This number must be unique to this document.)

DRDC Ottawa TR 2010-098

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(NON-CONTROLLED GOODS)DMC AREVIEW: GCEC December 2012

13. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual.)

The CBRN Research and Technology Initiative funded project CRTI-02-0045RD to produce a prototype portable optically stimulated luminescence reader. That is, the project aimed to design, construct, and test a portable detector for measuring the stored radiation-induced signature in common building materials using the principle of optically stimulated luminescence. As such, a detailed characterization of many common building materials was also required. This prototype detector was successfully constructed and was field tested both at DRDC Ottawa and during CRTI Exercise MARITIME RESPONSE in Slemon Park, Prince Edward Island. The detector has always performed well, demonstrating a capability that heretofore has not existed in a portable device. The system has demonstrated the ability to detect past radiation exposures to materials including cement, concrete, drywall and ceramic tile, to name a few. The project team is currently pursuing the patenting and commercialization of this technology, and has received interest from outside the intended end-use community.

L’Initiative de recherche et de technologie CBRN (IRTC) a financé le projet IRTC-02-0045RD dans le but de produire un prototype de détecteur portable à luminescence stimulée optiquement.Il s’agissait de concevoir, de construire et de mettre à l’essai un détecteur portable destiné à mesurer la signature radioactive entreposée dans des matériaux de construction couramment utilisés, en utilisant le principe de la luminescence stimulée optiquement (LSO). À cette fin, unecaractérisation détaillée de nombreux matériaux de constructions communs s’imposait. La construction du prototype a été menée à bon terme et l’appareil a été essayé en situation à RDDC Ottawa et durant l’exercice de l’IRTC appelé Exercice MARITIME RESPONSE, tenu à Slemon Park, à l’île-du-Prince-Édouard. Le détecteur a fonctionné correctement en tout temps, et il a donné une performance jusque-là inexistante pour un appareil portable. Le système a démontré la capacité de détecter la présence de matériaux ayant déjà été exposée à la radiation, entre autres du ciment, du béton, des plaques de plâtre et des carreaux de céramique. L’équipe du projet s’attache à faire breveter et commercialiser cette technologie. Des manifestations d’intérêt ont été reçues par les communautés d’utilisateurs finals visées.

14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g. Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.)

Optically stimulated luminescence; radiological terrorism; forensics

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