Stand-off Nuclear Radiation Detection

Transcription

1 Stand-off Nuclear Radiation Detection Peter E. Vanier Detector Development and Testing Div. Nonproliferation and National Security Dept. Brookhaven National Laboratory Brookhaven Science Associates U.S. Department of Energy Presented at the 18 th Annual NDIA Special Operations / Low Intensity Conflict Symposium and Exhibition Hyatt Crystal City February 26 28, 2007

2 BROOKHAVEN NATIONAL LABORATORY SITE

3

4 Camp Upton Established in 1947 on Long Island, Upton, New York, Brookhaven is a multi-program national laboratory operated by Brookhaven Science Associates for the U.S. Department of Energy (DOE). Six Nobel Prizes have been awarded for discoveries made at the Lab. Brookhaven has a staff of approximately 3,000 scientists, engineers, technicians and support staff and over 4,000 guest researchers annually. Brookhaven National Laboratory's role for the DOE is to produce excellent science and advanced technology with the cooperation, support, and appropriate involvement of our scientific and local communities. Collision of gold nuclei at RHIC

5 Lab work with Industry: Radiation Portal Monitor Testing and Evaluation

6 Lab work with Industry: Cadmium Zinc Telluride material evaluation CZT planar detector Translation stage 10-µm pinhole Synchrotron Radiation 10x10-μm 2 beam

7 Correlations between x-ray map & IR image This x-ray map shows the degraded regions precisely correspond to Te precipitates on the right This IR image shows Te precipitates, which could be identified by shape with IR microscope 100% correlations were found for all CZT samples tested in this work.

8 Lab Work with Industry Compressed Xenon Spectrometers Operate at room temperature Sufficient resolution to identify isotopes Scalable to large volumes - increased sensitivity Identify special nuclear materials Allow passage of medical isotopes Allow naturally occurring radioactive materials Reduce false positive rate kev planar design kev kev 414 kev kev CTC coaxial design ENERGY (kev) Pu-239 spectrum using xenon

9 High-speed, radiation-tolerant sampling/digitizing board Counts Co spectrum 57 Co FWHM 3.8% at 122keV CZT 3x3x7 mm 3 Peaking Time τ P 1.2µs Channel Low-power ASICs CZT pixel reset charge preamplifier high-order shaper shaper baseline stabilizer amplitude and timing extractor back-end processing & data concentration Preamplifier/shaper Preamplifier/shaper ASIC ASIC block block diagram diagram to external ADC 240-channel 240-channel multichip multichip module module for for Si Si drift drift detector detector readout readout Gamma Imaging Microelectronics Group AREAS OF EXPERTISE CMOS monolithic circuits charge-sensitive sensor interface analog signal processing low noise, low power techniques VLSI custom design + layout Handheld Handheld imaging imaging probe probe for for gamma gamma radiation radiation National Security light shield light shield MOSFET circuitry 2-5 μm nwell photodiode p - epitaxial layer p + substrate Positron Positron emission emission tomograph tomograph for for imaging imaging the the awake awake animal animal brain brain Radiation Radiation sensitive sensitive pixel pixel readout readout Gamma Gamma spectrometer spectrometer for for detection detection of of nuclear nuclear materials materials

10 Technology investment by BNL that can be helpful in solving SOLIC challenges Assume that terrorists will use any means to get attention, including radioactive materials Develop of new radiation detectors Gamma spectrometers Neutron imagers Improve interdiction of radioactive materials traffic Force protection from Radiation Dispersal Devices Force protection from Improvised Nuclear Devices

11 Interrogation of containers and trucks Container n,γ n,γ Gamma spectrometer or neutron imager Target Accelerator

12 Directional Detection and Imaging Pinhole camera Poor sensitivity FISSION SOURCE neutron MODERATOR PINHOLE He-3 WIRE CHAMBER

13 Thermal Neutron Imager 4. Cadmium-lined coded aperture camera

14 Reconstructing the image from the shadowgram (-1) MASK ARRAY G(k,l) SHADOW DATA N(i,j) N(i,j) r r i =1 j =1 G(i,j) (+1) R(k,l) = N(i, j)g(k + i,l + j)

15 Reconstructing the image from the shadowgram (-1) N(i,j) r r i =1 j =1 G(i,j) (+1) R(k,l) = N(i, j)g(k + i,l + j) Actually, use Fast Fourier Transforms

16 Lab test of imaging capability R = 300 cm, f = 30 cm 20 cm Neutron image Three 10-cm cubes of polyethylene, with two Cf-252 sources embedded (courtesy of A. Caffrey, INL)

17 Neutron image 20 cm R = 300 cm, f = 30 cm

18 Tests in the lab Photograph Neutron Image BPE Shielding Wooden wedge Neutron source behind paraffin cylinder

19 Tests in the field Thermal neutron image Spent nuclear fuel storage casks at Idaho National Lab

20 SOURCE IN TRUNK OF CAR THERMAL NEUTRON IMAGE 8 7 BACKGROUND NUMBER OF PIXELS SOURCE PIXEL INTENSITY PIXEL INTENSITY HISTOGRAM

21 Count rate as a function of distance COUNT RATE (cps) corridor car theory DISTANCE (m)

22 Simple attenuation model for neutron point source in air Direct Thermal Fast Total scattered 1000 Neutron flux 100 Scattered Fast neutron mfp ~ 100 m Direct thermal neutron mfp ~ 20 m 0.1 r (m)

23 Detectors can be scaled up to increase count rates 100 cm x 100 cm 20 cm x 140 cm

24 Active interrogation A pulsed electron accelerator produces high-energy x-rays (10-MeV) to generate photonuclear reactions Nuclear materials will undergo photofission and generate prompt and delayed neutrons The delayed neutrons continue to be emitted after each prompt neutron emission D.R. Norman, J.L. Jones, K.J. Haskell, P. Vanier and L. Forman, IEEE NSS-MIC Conference Record, October 23-29, 2005

25 Active Interrogation with Imaging Container Neutron imager n X-ray continuum 10 MeV electron accelerator D.R. Norman, J.L. Jones, K.J. Haskell, P. Vanier and L. Forman, IEEE NSS-MIC Conference Record, October, 2005

26 Image analysis PIXEL INTENSITY HISTOGRAMS Depleted uranium in polyethylene ms image window 69k neutrons, mean = 72, σ = σ Relative Neutron Intensity 12 Tungsten in polyethylene ms Image window 17k neutrons, mean = 122, σ = 41 Image Relative Neutron Intensity Use time gate to distinguish prompt neutrons from delayed fission Counts Neutron Response for Image 3 DU PND DU Bare He-3 W PND W Bare He-3 Imaging Window Time (ms)

27 8-element fast neutron double-scatter spectrometer

28 Experimental data, Fast neutron source centered Plane spacing = 50 cm, Range = 100 cm

29 Large area fast-neutron double-scatter directional detector Area 40 cm x 100 cm Modular design is expandable

30 CONCLUSIONS Directional detection helps find a neutron source in a uniform background There are few naturally occurring neutrons Ongoing issues Detector size Efficiency Angular resolution Uniformity Gamma rejection Spectroscopy

31 Acknowledgement The BNL Detector Development and Testing Division is grateful for continuing support from DOE NA-22, DHS and DTRA