Technology Sector Security. Sub Sector Detection. Segment - Radiological and Nuclear Weapons. Author Kshitij Aditeya Singh

Transcription

1 Technlgy Sectr Security Sub Sectr Detectin Segment - Radilgical and Nuclear Weapns Authr Kshitij Aditeya Singh Organisatin Institute f Nantechnlgy May, 2009

2 Table f Cntents Table f Cntents Title Definitin f Technlgy Segment Shrt Descriptin State f Research and Develpment Additinal demand fr research Applicatins and Perspectives Current Situatin within EU References and Literature

3 1. Title Detectin f Radilgical and nuclear weapns Keywrds: alpha particles, beta rays, gamma rays, high energy phtns, high energy electrns, radiatin mnitring, plastic scintillatrs, pure crystal scintillatrs, slid state devices, nuclear resnance flurescence, nanphsphr, nancmpsite 2. Definitin f Technlgy Segment Nuclear weapns and radilgical dispersal devices illegitimately smuggled acrss the Eurpean brders present a significant threat t civilian ppulatin. Radilgical dispersal devices (als knw as dirty bmbs ) are capable f dispersing highly radiactive particles ver large densely ppulated areas. Alpha particles (equivalent f a helium nucleus), beta rays (high energy electrns) and gamma rays (high energy phtns) are detected by devices t warn f the presence f a nuclear weapn r radilgical dispersive device [1]. 3. Shrt Descriptin Internatinal smuggling f weapns grade nuclear material presents a significant security challenge. Between 1993 and 2004, the Internatinal Atmic Energy Agency has reprted 18 incidents that related t smuggling f weapns grade nuclear materials. The prliferatin f nuclear weapns can take place thrugh the brders at prts, airprts, rad passengers and thrugh the pstal system. A tactical r imprvised nuclear weapn wuld be small enugh t be transprted in mdular cntainers. It was reprted that 25 kilgrams f highly enriched uranium r 4 kilgrams f plutnium-239 wuld be adequate fr a nuclear explsive device. A significant challenge is presented by dirty bmbs, which wuld present a significant challenge t health f civilians. Americum-241, califrnium-252, cesium 137, cbalt-60, iridium 192, and strntium-90 are radiactive species that culd pssibly be used fr a dirty bmb. The radiactive istpes califrnium-252 and americium 241, are used in the il industry and smke detectrs respectively, therefre are easy t btain fr a dirty bmb [2]. Weapn grade plutnium and highly enriched uranium can als be used fr radilgical dispersal devices. Radilgical dispersal devices can thus cntain a variety f radiactive species that emit gamma rays, neutrns and/r bremsstrahlung radiatin. Radiatin mnitring is largely dne by detecting gamma rays emitted by radiactive materials. The gamma rays cver a spectrum f energies. Gamma rays passing thrugh matter depsit a part f their energy resulting in electrns that can be detected. One methd f detectin f phtns in a detectr is a prcess called scintillatin. Plastic scintillatrs, pure crystal scintillatrs, and slid state devices are used fr detecting gamma radiatin. The drawback f plastic scintillatrs is the lw energy absrptin due t the lw density f the material. As a result the instruments using such detectrs cannt identify the radiactive material accurately. Pure crystal scintillatrs and slid state devices are relatively better at absrbing all the energy f gamma rays due t their higher density and atmic number. Radiactive istpes such as strntium-90 emit beta rays, which when shielded prduce bremsstrahlung radiatin which can be detected by the same methds as gamma rays. Weapn grade plutnium and highly enriched uranium are relatively less radiactive with respect t gamma ray emissin in cmparisn t ther istpes, therefre making them mre difficult t detect. Neutrns are als emitted by weapn grade plutnium, ften making detectin easier due t the lw natural backgrund frm csmic radiatin. The neutrn detectrs functin by detectin f prtns released frm nuclei struck by neutrns, f fissin daughters r by measuring gamma rays, electrns and ther charged particles. Uranium istpes emit alpha particles and gamma rays, and nt as many neutrns [2]

4 A number f strategic tls are used in the detectin f radiatin such as radiatin prtal mnitring equipment, persnal radiatin detectrs, hand held detectrs and x-rays systems fr imaging f shielding. Radiatin detectin systems can be passive r active. Passive systems fr detectin f radiatin include radiatin prtal mnitring equipment, mbile systems, hand held, backpack and belt mnitring systems, all f which have been deplyed. Mbile x-ray and fixed systems have been used fr penetratin f carg cntainers fr suspected carg. Plutnium and a few ther radiactive materials emit neutrn and tus neutrns are f particular interest in detectin applicatins at brder crssing [3]. Radiatin prtal mnitring equipment has been deplyed fr brder crssing and prt applicatin in detectin f illicit nuclear material. Detectrs f gamma rays based n plyvinyltluene (PVT) and thallium dped crystalline sdium idide have been demnstrated and deplyed. Fr passive screening f gamma rays, the energy range f interest fr detectin was between 20 kev t 3 MeV [4]. A cmparisn f radiatin prtal mnitring equipment fr brder security was dne using gamma ray and neutrn detectrs. A cmparisn f plyvinyltluene and thallium dped crystalline sdium idide fr vehicle based radiatin prtal mnitring has als been evaluated in the literature. The spectral capability f NaI(Tl) is superir t PVT fr istpic identificatin, thugh the cst f NaI(Tl) has been reprted t be much higher than PVT. A range f envirnmental and peratinal factrs determine the suitability f a detectr in different perating scenaris. Each detectr type ffers sme advantages fr varius perating cnditins f prtal mnitring systems [5]. Energy based alarm algrithms with enhanced sensitivity ver grss cunting have been implemented fr radiatin prtal mnitring equipment. The energy infrmatin btained frm plastic scintillatrs can be used t distinguish between naturally ccurring radiactive material and special nuclear material. The energy based algrithm was cnsidered t be a much desired imprvement in detectin ver grss cunt algrithms. One f the main limitatins f radiactin prtal mnitring systems is the presence f naturally ccurring radiactive istpes that can present a significant peratinal challenge [3,6]. Nuclear weapns detectin in transprtatin carg has been demnstrated with a range f techniques, including bth passive and active detectin. The pht-fissin f neutrn emissin induced by gamma rays frms the basis f ne active detectin apprach. The technique and its effectiveness has been demnstrated fr radiactive material in simulated shipping cntainers and air-carg [7]. Detectin f nuclear weapns in carg has been demnstrated using a pulsed beam f neutrns, that prduce fissin events and detectin f their fissinable material is dne frm the beta delayed neutrn emissin r beta delayed high-energy gamma radiatin. This is anther f the several active interrgatin detectin methds, and has been demnstrated fr simulated shipping carg [8]. Nuclear Resnance flurescence, anther ptential active interrgatin technique, has been demnstrated in the detectin f istpes f uranium in a labratry. The basis f the methd is a unique signal that is relevant t each nuclei. The technique cmbined with effective algrithms has been demnstrated in the labratry as a pssible methd that may be applicable t detectin f material in sea cntainers, truck cntainers, trucks and ther vehicles [9]. Mnitring f radiactive xenn in air has been used t detect nuclear weapns explsins as part f the wrldwide netwrk f the Cmprehensive Test Ban Treaty verificatin effrt. A prttype single phswich detectr has been used t detect beta particles and gamma rays frm radixenn istpes [10].High reslutin inductively cupled plasma mass spectrmetry and acceleratr mass spectrmetry have been demnstrated in detecting ultra lw level f uranium istpes in marine envirnments. The uranium istpe signature prvides valuable infrmatin n rigin f uranium. The methd has useful applicatins in mnitring radiactivity in depleted uranium envirnments and undeclared nuclear activity r mvement f nuclear material [11]

5 Detectin f radiistpes using a distributed sensr netwrk, as ppsed t central fixed systems, has been prpsed and develped. These distributed sensr netwrk, cupled with a mnitring prtal has been demnstrated. The sensr array cnsisted f sdium idide scintillatrs that were cnnected t a platfrm fr prcessing f gamma cunts. The perfrmance f the array was reprted t be higher than that f a single detectr, thugh that is a cntrversial claim. The advantage f this prf f cncept is that it may be inexpensive, further research is aimed at increasing sensitivity and develping an integrated platfrm fr chemical and bilgical weapns [1]. The use f varius detectrs fr radiactive species has been mentined earlier. A system fr simultaneus detectin f radiatin species such as x-rays, gamma rays, neutrns and minimum inising particles has been bserved in the literature. The sensitivity f the scintillatrs in the research was achieved using nan-sized particles, dpants and extruded plastic material. Three different type f detectrs have been described, which identify specie f radiatin. Nan-sized particles f lithium have been used in neutrn detectrs. The wavelength shifting fibre absrbs scintillatr light at a wavelength and re-emitting it at a higher wavelength t better match the phtdetectr used [12]. The use f nanscale materials fr detectin f radiatin is expected t vercme single crystal based detectrs limitatins such as size and cling requirements t very lw temperatures. Nanphsphr has been mentined as a candidate material fr scintillatrs and detectrs. Cerium dped lanthanum halides (less than 10nm in diameter) have als been mentined as suitable candidates fr scintillatrs nancmpsites. Due t their brightness and shrt decay lifetime they are very effective in gamma ray detectin. Scaling up f the synthesis f cerium lanthanum fluride t kilgram quantities remains a further research challenge that remains t be addressed [13]. Enhanced ptical prperties f nancmpsites made f existing scintillatr materials have been reprted in the literature. The nancmpsites ffer enhanced light utput, decreased csts and scalability have been demnstrated at the prf f principle stage. Cerium dped lanthanum fluride has been synthesized, nanparticles having a size f nm, have shwn a three times increase in light intensity as cmpared t bulk material used fr scintillatin. Further research in the area was identified as synthesis f nanphsphrs as scintillatrs and their fabricatin as nancmpsites. Measurement f abslute light yield and linearity f the nancmpsite were mentined as challenges fr characterizatin [14]. Slid state semicnductr detectrs ffer advantages ver gas filled detectrs and scintillatr detectrs due t excellent energy reslutin and higher efficiency. High purity germanium detectrs are the gld standard fr gamma ray detectin but require crygenic temperatures. A number f semicnductrs have been suggested fr applicatin such as cadmium zinc telluride (CZT), cadmium telluride, gallium arsenide, indium phsphide, mercury idide and thallium brmide. CZT ffer advantages due t its wide band gap, high resistivity and cmmercial availability. The higher resistivity is a desirable characteristic as it decreases nise level thus imprving the reslutin f detectin. A synthesis prcess fr prducing nanwire arrays f CZT has been mentined in the literature fr detecting gamma ray radiatin. In the prcess CZT was electrdepsited n a titanium dixide nantubular template. Stacks f CZTs with very high resistivity were fabricated and cnnected. It was experimentally demnstrated that the flw in the current increased when expsed t a radiatin surce. The ptential f nanwires being used as a radiatin detectr at rm temperature was at a much lwer bias applied in relatin t bulk material detectrs. Very high sensitivity t radiatin was experimentally demnstrated [15]. Other recent methds have been mentined in the literature such as the Neutrn Imaging Camera fr detectin f weapn grade plutnium at brders. The camera is based n three dimensinal image tracker develped initially fr applicatins in gamma ray astrphysics. The wrking principle is based n measuring the energy and psitin in three dimensins f the charged particles mving thrugh the camera medium. The applicatin was successful - 5 -

6 demnstrated t identify radiatin at stand-ff distances and in the presence f ther backgrund emissins [16]. An Electrnic Neutrn Dsimeter has been mentined in the literature fr detecting radiatin. It uses scintillatrs n a pair f phtmultiplier tube minimizing the pwer cnsumptin and increasing peratinal times. The dsimeter has been prttyped with results exceeding electrnic neutrn dsimeter standards [17]. Micrcantilevers were reprted t detect an alpha particle as it impinges n an electrically insulated metallic surface by underging a deflectin f a few nanmetres. The particle is detected by a shift in the resnance frequency due t electrstatic frces. A single alpha particle can be detected using this methd, hwever ther cnventinal methds have been shwn t have higher sensitivity as cmpared t these detectrs [18]. One f the main challenges f detecting these threat radiactive materials is the shielding using lead and ther dense materials fr gamma rays, and hydrgenus materials fr neutrns. An additinal challenge is interference frm medical istpes and ther slightly radiactive, but relatively inncuus materials such as smke detectrs, fertilizers, televisin sets, abrasives and glazed ceramics. The apprach f using X-ray scanners has been used in the United States, fr any shielding that may be used t hide radilgical weapns. Other methds such as active interrgatins using gamma ray and neutrns have als been reprted. As mentined abve, these induce fissin in uranium and plutnium, resulting in gamma rays and neutrns that are detected [2]. 4. State f Research and Develpment The sectins give an verview f the technlgy develpment in relatin t a specific technlgy. Fundamental Research is defined fr this purpse as research with n particular gals f cmmercialisatin. Applied Research is defined as research cnducted in academia and industry directed twards a specific purpse and applicatin. Prttype has been defined as Applied Research r Fundamental Research that has fund a ptential market applicatin. Technlgies that are in the field trial state are defined as thse that are in the prcess f cmmercialisatin, and are being tested. Deplyed nantechnlgies are thse that have fund an early stage market. Mass Market has been defined as thse technlgies that have been adpted by large ppulatin and are attractive high grwth markets. The technlgies have been mentined are thse mentined in the literature review fr nuclear and radilgical weapns detectin. The scale f readiness mentined ranges frm fundamental research t mass market. The range f activity indicates varius methds and materials being used at different stages f readiness. The table RNW.1 belw gives an verview f enabling technlgies fr detectin f radilgical disperse device and nuclear weapns in relatin t their develpment status. Table RNW.1 - Technlgy and its Develpment Status fr radilgical disperse devices and nuclear weapns detectin Radiatin prtal mnitring Fundament al Research Applied Research Prttype Field Trials / Pilt plant ( Precmmercialisatin ) Deplyed (Cmmerciali sed) Mass Market Sensr Array - 6 -

7 Spectrme tric methd Nuclear Resnanc e flurescen ce Nanmater i-al based Detectrs 5. Additinal demand fr research Specific research needs were mentined in the literature relating t different detectin aspects are as fllws: Materials research needs fr CBRNE sensrs has been identified as develping sensrs with the ability t detect and warn. Sensr capabilities t allw functinality at stand ff distances in rder t prtect persnnel in cnflict situatins. Enhanced understanding f the energetic behaviur f weapns and its packaging mdes has been suggested. Enhanced and prtable imaging techniques have been identified as a research need fr civilian areas with high shipping cntainer traffic. Integratin f imaging and detectin techniques with mass transprtatin has als been mentined [19]. 6. Applicatins and Perspectives In the expert engagement prcess fr the technlgy segment, the fllwing perspectives were bserved: Funding research and develpment fr detectin f CBRNE and Narctics was cnsidered very imprtant fr sciety and ecnmy f Eurpe. The mst imprtant drivers fr research and develpment f detectin f CBRNE and Narctics were cnsidered technlgical and scial impact. The technlgical drivers relate t cst, perfrmance, efficiency and absence f slutins. Other secndary drivers were indicated as peratinal advantage in cnflict situatins, safety, prductivity gains and reginal security plicy. The main drivers fr R&D f radilgical and nuclear detectin were mentined t be mbility f detectin unit, cst f sensrs, devices and instruments, and accuracy f detectin. Other secndary drivers were time fr detectin, integratin f detectin platfrm, and life time f peratin The main barriers t research and develpment f detectin f CBRNE and Narctics were mentined as availability f finance t early stage cmpanies and inadequate technlgy transfer frm Universities. Secndary barriers indicated were intellectual prperty cnflicts, lack f tax incentives and lack f supprtive gvernment plicy. Qualitative respnses indicated t meet the challenges f availability f finance, EU needs t cnsider dual cmmercial use f security technlgy as the market was relatively smaller than US. While trends in US are twards gvernment driven technlgy - 7 -

8 that is validated, EU grants are inadequate fr prving technlgy. It was suggested that gvernment validatin f systems was necessary as labratry systems nt scaled fr field use. The main barriers t R&D f radilgical and nuclear detectin were indicated as lack f equipment and testing facility, and limited supprting plicies. Other secndary barriers were indicated as lack f reprducible results, failure in integrating devices and rbustness f field trials. Qualitative respnses suggested the different apprach twards funding research in radilgical and nuclear weapns frm different agencies. Shrt term 2-3 year view was detrimental t research effrts. The desirable characteristic f a radilgical nuclear detectr was mentined inexpensive, excellent energy reslutin, thermally stable, physically rbust, and usable fr a lng perating life. The applicatin trends were mentined as: Radilgical and nuclear detectrs are physically large. Physical miniaturisatin is nt pssible therefre imprved material perfrmance is being investigated. Increased energy analysis fr radiatin detectin has led t higher csts. The directin f research is twards extracting mre infrmatin frm less expensive technlgical slutin. Respnse time was entirely applicatin dependent. While in brder situatin 2-3 secnds respnse time is ideal, lnger at trading prts, it shuld be within millisecnds in crwded lcatins. Operatinal factrs imprtant in radilgical- nuclear detectin are time, distance and shielding. Time f detectin is fr secnds, and distance is based n packages and physical sizes f vehicles. Shielding is cnsidered t be the main factr fr planning against different scenaris. Results frm technique such as Nuclear Resnance flurescence were cnsidered pr fr labratry cnditin. In real situatins with shielding they may nt prduce predictable results like thse frm active induced fissin by neutrns r gamma rays. One f the main applicatin prblems was cnsidered t be absence f an acceleratr which can address the lack f tunable, variable energy, cntinuus surce f gamma rays with the right energy. The present surces are pulsed thus resulting signal t nise rati are nt feasible fr applicatin f technique. CeF 3 material was mentined t have been develped as prf f principle. The limitatin fr CeF3 was reiterated t result frm the lw light utput. It was mentined that scale up t 500 gram/batch synthesis f CeF 3 had been achieved. There are limitatins in understanding f the prductin prcess. All detectr materials shw limitatins and advantages ver each ther

9 Applicatin areas where nanmaterials can add value wuld be nanparticle inclusin in plastic fr plastic scintillatrs. Nan-additives culd play a rle in gamma radiatin detectrs Nantechnlgy culd enhance light detectin system fr pht tube detectin and gas detectrs. The sensing methds fr radiatin and nuclear weapns detectin that are presently deplyed are radiatin prtal mnitring and spectrscpy. Methds fr radilgical and nuclear detectin that are expected t be deplyed after at least 5 years f develpment are sensr arrays fr radiatin detectin and nanmaterials based detectrs. The factrs determining uptake f radiatin detectin technlgy are physical size, price, rbustness, reslutin. Respnse time, cunt rate (sme scintillatrs are slwer than thers), and relatinship t material prperties. The mderately attractive future grwth markets fr explsives detectin were expected t be radiatin prtal mnitring, sensr arrays fr radiatin and spectrscpy methds. Investment in technlgy and evaluatin f prduct markets is imprtant fr radiatin detectin. One cmpany hlding sle mnply in a market thrugh patents is cunterprductive fr develpment in security. Basic research fr radiatin detectin was perceived t be better in Eurpe than Nrth America, mainly cncentrated in Universities. Natinal labratries in US were fcused n technlgy develpment and transfer fr radiatin detectin. Eurpe was cnsidered particularly weak fr technlgy transfer. The theme f integrated platfrm fr detectin f chemical, bilgical, explsive, radilgical and nuclear threats was cnducted at Dusseldrf in March The fllwing utcme and recmmendatins resulted frm the discussin: Technlgy was nt sufficiently advanced t achieve single platfrm detectin. An integrated mdular system that fcuses n Chemical, Bilgical and Explsive as ne unit and Radilgical-Nuclear detectin as a separate mdule is a better apprach. One f the main weaknesses fr CBRNE detectin was cnsidered t be systems integratin. It was suggested that a statement f requirements t be prduced taking nantechnlgy int cnsideratin. Accuracy and reliability f measurement was cnsidered t be mst imprtant characteristic. Reprducibility f measurements and perating life f sensr were cnsidered t be pr fr mdular systems f detectin. The cst f false psitives are very high, therefre peratinal definitin shuld be develped n a case by case basis fr a mdular system. The need fr greater fundamental research in understanding the sensing mechanism was emphasised

10 It was recmmended that cmmunicatin between materials and sensing cmmunity be imprved in rder t create mutual awareness f technical breakthrughs. The first area f applicatin is expected t be transprtatin hub fr such a mdular system. Technlgy penetratin and applicatin driven by state regulatin fr CBRNE detectin. 7. Current Situatin within EU The fllwing Preparatry Actin fr Security Research Funded prjects were funded by the Eurpean Cmmissin and are relevant t radiatin and nuclear detectin: Eurpean Security: High level study n threats respnses and relevant technlgies (ESSTRT). The supprt actin prject has prvided a cmprehensive verview f necessary respnses t security challenges. These include technlgies fr detecting nuclear weapns and radilgical disperse devices at airprts and travel hubs. The prject als investigated technlgies that culd develp smart cntainers, and brder security against weapns [20]. CBRNE related testing and certificatin facilities - a netwrking strategy t strengthen cperatin and knwledge exchange within Eurpe (CREATIF) was initiated early in The prject aims t create a netwrk f prduct testing facilities fr CBRNE detectin [21]. The fllwing framewrk 7 prjects funded under the security theme by the Eurpean Cmmissin have relevance t the radilgical-nuclear detectin. Cperatin acrss Eurpe fr Cd(Zn)Te based security instruments (COCAE) prject initiated in 2008 is fcused n spectrscpic measurements fr detecting radiactivity using Cd(Zn)Te crystals [22]. Integrated mbile security kit (IMSK) was initiated in The bjective f the prject is t cmbine technlgy slutins frm Detectin f CBRNE, area surveillance, and check pint cntrl fr additinal sensitive security lcatins. The sensr data is expected t be integrated with cmmunicatin and data mdule t a cmmand centre [23]. 8. References and Literature [1] S. M. Brennan, A.M. Mielke, D. C. Trney, A. B. Maccabe, Radiatin Detectin with Distributed Sensr Netwrks, Cmputer, vl. 37, pp , Aug

11 [2] R.T. Kuzes, Detecting Illicit Nuclear Material, American Scientist, vl. 93, pp , 2005 [3] R. Kuzes, J. Ely, R. Hansen, J. Schweppe, E. Sicilian, D. Strmswld, Hmeland Security Instrumentatin Fr Radiatin Detectin At Brders, in Frth American Nuclear Sciety Internatinal Tpical Meeting n Nuclear Plant Instrumentatin, Cntrls and Human-Machine Interface Clumbus, Ohi, September, 2004 [4] S. S. Nafee, and M. I. Abbas, A theretical apprach t calibrate radiatin prtal mnitr (RPM) systems, Applied Radiatin and Istpes, vl. 66, pp , Octber [5] E.R. Sicilian, J.H. Ely, R.T. Kuzes, B.D. Milbrath, J.E. Schweppe, and D.C. Strmswld, Cmparisn f PVT and NaI(Tl) scintillatrs fr vehicle prtal mnitr applicatins, Nuclear Instruments and Methds in Physics Research A 550 (2005) [6] B.D. Geelhd, J.H. Ely, R.R. Hansen, R.T. Kuzes, J.E. Schweppe, R.A. Warner, Overview f Prtal Mnitring at Brder Crssings, Nuclear Science Sympsium Cnference Recrd, IEEE Vlume 1, Oct Page(s): , [7] B. J. Micklich, and D. L. Smith, Nuclear materials detectin using high-energy gamma-rays, Nuclear Instruments and Methds in Physics Research B, vl. 241, pp , [8] D.R. Slaughter, M.R. Accatin, A. Bernstein, P. Biltft, J.A. Church, M.A. Descalle, J.M. Hall, D.R. Manatt, G.J. Mauger, T.L. Mre, E.B. Nrman, D.C. Petersen, J.A. Pruet, and S.G. Prussin, The nuclear car wash: A system t detect nuclear weapns in cmmercial carg shipments, Nuclear Instruments and Methds in Physics Research A, vl. 579, pp , [9] W. Bertzzi, S. E. Krbly, R. J. Ledux, and W. Park, Nuclear resnance flurescence and effective Z determinatin applied t detectin and imaging f special nuclear material, explsives, txic substances and cntraband, Nuclear Instruments and Methds in Physics Research B, vl. 261, pp , [10] W. Hennig, H. Tan, A. Fallu-Labruyere, W. K. Warburtn, J. I. McIntyre, A. Gleyzer, A phswich well detectr fr radixenn mnitring, Nuclear Instruments and Methds in Physics Research A, vl. 579, pp , [11] S.H. Lee, P.P. Pvinec, E. Wyse, and M.A.C. Htchkis, Ultra-lw-level determinatin f 236U in IAEA marine reference materials by ICPMS and AMS, Applied Radiatin and Istpes vl. 66, pp , [12] A.D. Brss, K.L. Melltt, and A. Pla-Dalmau, Systems and Methds fr detecting nuclear radiatin in the presence f backgrunds US Patent 6,909, 098 B2, 21 June [13] Ls Alams Natinal Labratry, Develpment f nancmpsite scintillatrs, Spring 2007, [14] E. A. McKigney, R. E. D. Sest, L. G. Jacbshn, P. A. Santi, R. E. Muenchausen, K. C. Ott, T. M. McCleskey, B. L. Bennett, J. F. Smith, D. W. Cke, Nancmpsite scintillatrs fr radiatin detectin and nuclear spectrscpy, Nuclear Instruments and Methds in Physics Research A, vl. 579, pp , [15] M.Misra, K.S. Raja, and T. Gandhi, Cadmium Zinc Telluride nanwire sensrs fr detectin f lw energy gamma-ray radiatin, in Prceedings f SPIE 6959, 2008, p

12 [16] S.D. Hunter, G.A. de Nlf, L.M. Barbier, J.T. Link, S. Sn, S.R. Flyd, N. Guardala, M. Skpec, and B. Stark, Neutrn Imaging Camera, in Prceedings f SPIE 6954, 2008, p [17] H.Ing, T. Cusins, H. R. Andrews, R.Marchrafi, A. Vevdskiy, V.Kvaltchuck, E.T.H. Cliffrd, M. Rbbins, C.Larssn, R. Hugrn, J. Brwn, A new Electrnic Dsimeter (END) fr reliable persnal dsimetry, in Prceedings f SPIE 6954, 2008, p [18] A. C. Stephan, T. Gaulden, A. D. Brwn, M. Smith, L. F. Miller, and T. Thundat, Micrcantilever charged-particle flux detectr, Review f Scientific Instruments, vl. 73, pp , [19] T. G. Maréchaux, Better Materials Can Reduce the Threat frm Terrrism, JOM, vl. 53, pp 12 13, December [20] Directrate General fr Enterprise and Industry Eurpean Cmmissin, ESSTRT Eurpean Security: High level study n threat respnses and relevant technlgies, 15th April 2009, [21] Crdis, CBRNE related testing and certificatin facilities - a netwrking strategy t strengthen cperatin and knwledge exchange within Eurpe, 16th April 2009, &pid=28&q=FD8A9BBC079BD5FCECD584ADBD3CE6A7&type=adv [22] Crdis, Cperatin acrss Eurpe fr Cd(Zn)Te based security instruments, Accessed n 16th April 2009, &pid=3&q=FD8A9BBC079BD5FCECD584ADBD3CE6A7&type=adv [23] Crdis, Lcalisatin f threat substances in urban sciety, 16th f April 2009, &pid=35&q=FD8A9BBC079BD5FCECD584ADBD3CE6A7&type=adv