Glasses for detection of penetrating radiation via the Cherenkov

Glasses for detection of penetrating radiation via the Cherenkov Effect

Jason Hayward The University of Tennessee Zane Bellb, Lynn Boatnerb, Mitchell Laubacha, Clint Hobbsa, Birsen Ayaz-Maierhafera, Rose Johnsona, Cole Lillarda, Jay Jellisonb, Joanne Rameyb, Jim Kolopusb

a. University of Tennessee-Knoxville (UTK) b. Oak Ridge National Lab (ORNL)

Basic Research Technical Review July 2012

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Glasses for Detection of Penetrating Radiation via the Cherenkov Effect

PI: Jason P. Hayward, Univ. of Tennessee Award Number: HDTRA1-09-1-0052

Objective: Enable the fabrication of low cost sensors with faster time response, high efficiency and excellent discrimination against background (selectivity/specificity) so that detectability at standoff is increased

Approach: Investigate properties of non-scintillating glasses suitable for detection of ionizing radiation (MeV γs) via the Cherenkov effect. Determine what glasses can be made to optimize gamma sensitivity, make samples of said glass, measure their optical properties, and measure their radiation response. Personnel Support: Cumulative support includes 1 faculty member, 3 post-docs, 5 grad students, 5 undergrads supported by the project; Several collaborators funded at Oak Ridge National Laboratory (ORNL) and now also at Idaho Accelerator Center (IAC)

Relevance: Investigative approach is tailored and specialized to support photofission and muonic x-ray detection since detectors are capable of sensing prompt gammas and measuring their multiplicity.

Results this year: •  Fabricated selected Cherenkov glass samples

in larger volumes for LINAC measurements •  Linear accelerator measurements

demonstrate that detectors function during & after pulse, even in-beam and out of shielding

•  Response to neutron activation measured for several glass samples, database updated

Funding: Year 1: FY10-$347k, Year 2: FY11-$348, Year 3: FY12-$350k; Options: Year 4: FY13-$231k, Year 5: FY14-$234k

PI contact Information: Jason Hayward, [email protected], Phone (865.574.5699)

UNCLASSIFIED

UNCLASSIFIED

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Program objective

•  Investigate properties of non-scintillating glasses suitable for detection of ionizing radiation (MeV γ) via the Cherenkov effect. 1)  Determine what glasses can be made to optimize gamma

sensitivity, 2)  Make samples of said glass, 3)  Measure their optical properties, and 4)  Measure their radiation response.

Basic Research Technical Review, July 2012

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Program objective •  This basic research will support counter-proliferation work by

developing knowledge to enable the fabrication of low cost sensors with faster time response, high efficiency and excellent discrimination against background (selectivity/specificity) so that detectability at standoff is increased

•  It is NOT an objective of the work to develop a detector •  Rather the objective is to perform the research necessary to

establish the materials properties and fabrication techniques of materials suitable for the production of Cherenkov light, but with an investigative approach that is tailored and specialized to support photofission (~7 prompt γs/fission, unexplored!) and muonic x-ray detection

•  Fast, efficient detectors required for measurements of nuclear data relevant to nuclear security (prompt γ, multiplicity)

•  Cherenkov detectors are also of interest for high energy physics (e.g., CERN), potentially for cargo screening


Production of Cherenkov light

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⇒ Light emitted while charged particle moves faster than c/n


Cherenkov basics

•  Responsible for blue glow seen in pool reactors and spent fuel pools

•  Below 35 MeV, only emitted by electrons and positrons (n=1.5)

•  Gammas can cause Cherenkov light via production of photo- and Compton electrons, e- and e+ in pair production

•  Light emitted ~ ps (a typical slowing down time of electrons)

•  Cherenkov detectors are not bright: 75 – 200 photons/MeV

•  Spectroscopic information is limited

6 From Sowerby Basic Research Technical Review, July 2012

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Technical approach •  Uniqueness

•  Our approach is distinct from high energy physics studies in that lower energy regimes are explored for radiation sensing, made possible by the use of glass instead of, for example, voluminous gas Cherenkov sensors used in high energy physics.

•  This approach is markedly different from typical low energy nuclear sensing that relies on semiconductors or scintillators.

•  Scope •  The parameter space available for the synthesis and development of

new glass detectors is very large, further broadened by choice of moderate and high Z materials to disperse in the glass.

•  Potential promise •  Use in active environment: Deadtime-less,

very high event rate, time-of-flight •  Faster, more efficient (sensitive) than

plastic scintillator; also low cost •  Engineered for some selectivity (like

plastic); specificity needs study Basic Research Technical Review, July 2012

Project schedule

We have set out to map a large materials parameter space, involving a continuous feedback loop of investigation, materials selection, sample fabrication, and sample characterization.

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All experimental


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Results summary •  113 glass samples fabricated

•  22 families of glass formers investigated; focus on larger samples last year

•  Optical and physical characterization •  Most samples optically transparent, not hygroscopic, durable for handling

and mounting to photosensor

•  Radiation characterization •  Focus on MeV gammas and slow neutron activation (give highlights) •  First measurement set completed at Idaho Accelerator Center

•  Results being documented in Microsoft Access database •  Journal papers (2) and other publications •  Education and training

•  Cumulative: 5 grads, 5 undergrads, 3 postdocs


Glass systems investigated to date •  Calcium sodium phosphate* glass (6) •  Zinc borate glass (9) •  Lead phosphate glass (19) •  Lithium bismosilicate glass (4, colored) •  Lithium lead phosphate glass (3) •  Bismuth borate glass (7, colored) •  Germanate glass (3) •  Lead vanadate glass (2, opaque) •  Sodium barium phosphate glass (1) •  Magnesium cesium phosphate glass (1) •  Barium cesium phosphate glass (1) •  Calcium cesium phosphate glass (1) •  Lithium silicate glass (2) •  Calcium magnesium phosphate glass (1) •  Calcium phosphate (1) •  Barium Germanate oxide (1) * a.k.a. “cladding glass”

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* a.k.a. optical fiber “cladding

glass” per patent 5,812,729


Glass systems investigated to date •  Lithium borate glass (15, hydroscopic & cloudy) •  Zinc metaborate glass (1) •  Sodium silicate glass (1) •  Zinc phosphate glass (1, colored) •  Germanophosphate glass (1) •  Germanate oxide glass (2) •  Sodium borate glass (1, hygroscopic) •  Potassium borate glass (1, hygroscopic) •  Cesium borate glass (1, cracked) •  Calcium lithium phosphate glass (2, colored) •  Calcium strontium phosphate glass (2) •  Lithium gadolinium borate (2, cracked) •  Hafnium tetrafluoride* glass (1 simulated) •  Standards: PMMA/UVT, water in UVT

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* Data provided by Le Verre Fluore, Dr. Marcel Poulain (Univ. Rennes)


Measured properties from fabricated glass samples

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Np ∝1ρ

µ∝ρ

Higher densities achieved by loading lead, bismuth,

germanates, Hf


Large samples fabricated

•  Chose glasses with special focus on those with absorption edges below 270 nm

•  Magnesium Cesium Phosphate sample (51 mm x 51 mm, 3.15 g/cm3)

•  Calcium sodium phosphate (“cladding”) glass with Lu2O3

(65 mm x 25 mm, 2.82 g/cm3)

13 Basic Research Technical Review, July 2012

Experimental setups at IAC •  6-25 MeV beam energies, 120 Hz, ~1

nC/pulse, FWHM~10-50 ns •  Stations at side or back angles •  Plastic scintillator or Cherenkov beam

monitors in-beam •  Observing detectors in or out of Pb

shielding, collect over a few 100 ns during and after pulse

•  Targets: empty, Pb (1 kg), DU (578 g)

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Experimental setups •  Observing detectors: Plastic scintillators, 2 large

glass Cherenkov detectors, Cherenkov reference (quartz, UVT, lucite, water), reference scintillators (NaI, LSO, LaBr3,BaF2)

•  After delays set appropriately, all data digitized at 2 Ga/s using Acqiris DC282 system; use gun trigger for start

•  Same PMTs also tested with no radiation sensing material; operating voltages kept constant, photoelectron responses for each characterized in lab with pulsed laser source


Cherenkov detectors function in and after the photon beam

•  Induction beam monitor in blue (averaged) senses electron bunch before converted to brem.

•  Individual waveforms from Cherenkov detector in beam follow pulse

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6 MeV 13 MeV


Ch. detector ready to look for prompt photons on tail of accelerator pulse

•  Mean pulse shape in green •  25 MeV, DU target

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Ch. Detector (UVT) LSO


Prompt coincident gamma pulses observed

•  16 MeV endpoint •  Cherenkov glass detectors in coincidence with

each other; individual gamma bursts observed 18

Mg Cs Phosphate Cladding glass w/ Lu2O3

•  16 MeV endpoint beam •  Waveforms from in-beam Cherenkov detector shown

(fused silica) •  Presence of dense targets creates additional detected

prompt photons (background or “source”) 19

Differences in response (in-beam) observed for different targets

No target Lead DU

•  16 MeV endpoint beam, target varies •  Waveforms out of beam Cherenkov detectors shown;

green=MgCsPhosphate, red=Cladding glass 20

Differences in response (out of beam) observed for different targets, apply coincidence

Lead DU

Differences in response (out of beam) observed for different targets

•  Frequency vs. integrated charge in pC shown for 16 MeV beam energy

•  Results shown for 2 different Cherenkov glasses (large samples) that are out of beam


Cherenkov detectors show observed differences with beam energy, even out of shielding

•  Integrated charge, no target present; monotonic ñ observed •  Compared with 1” LSO reference detector in shielding •  Important note: Time-of-flight may distinguish photons from

source vs. photons from target (no shielding required) 22

No lead shielding

In shielding

Cherenkov detectors show observed differences with beam energy, now DU target present

•  Integrated charge, DU target present •  Compared with 1” LSO reference detector in shielding

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No lead shielding

In shielding


Summary of first results from LINAC measurements

²  Cherenkov detectors function during and immediately after photon pulse ²  Gate on time window ~ 1000 ns, including pulse, so that only prompt

products are observed (window ~100 ns means high rep rate possible) ²  Cherenkov detectors appear to function the same way either in or out of

shielding (over time window ~100s of ns) ²  Cherenkov detectors show a monotonic increase in response (integrated

charge) with an increase in photon beam energy (6-25 MeV) ²  PMTs also respond to beam radiation in a similar manner to Cherenkov

detectors; further analysis of data and active, prompt backgrounds is needed ²  For future analysis and study

²  Process charge data in terms of numbers of photoelectrons, normalized to both charge in pulses and solid angle

²  Setup system completely out of shielding ²  Use fast pulsed 44 MeV LINAC, setup for fast timing resolution ²  Cover larger solid angle with careful geometry so solid angle is known ²  Use statistical analysis to look at differences between targets (in beam,

falling edge)

Selectivity/specificity – consider background response

•  Detectability involves sensitivity & specificity •  Passive environment

•  Gamma background (<2 MeV) •  Fast* or slow n activation (100 m-2s-1 at sea level)

•  Cosmic ray muons* (~167 m-2s-1 at sea level) •  Photon production based upon thickness in cm

•  Use of timing coincidence or muon veto* •  Active environment*

•  High energy x-ray scatter (photofission) •  With IAC LINACs, we can look up to 44 MeV e-

•  Fast n activation: (n,2n), (n,p) •  Response to muon or proton accelerators •  Note: Only response within time gate matters

* Not in original work scope, as time allows

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From Gordon et

al Basic Research Technical Review, July 2012

Measurements: slow neutron activation

•  Measurements used to understand response of glass Cherenkov detectors to slow neutron activation


B. Ayaz-Maierhafer, J.P. Hayward, Z.W. Bell, L.A. Boatner, R.E. Johnson, “Measurements of thermal neutron response in Cherenkov glassed designed for MeV photon detection,” submitted to IEEE Transactions on Nuclear Science, June 2012.

Physical and nuclear properties of five selected glasses


Selected Neutron Activation Products and Their Main Beta and Gamma Energies


Measurements for Glass A (Sodium Barium Phosphate)

0 500 1000 1500 2000 2500 3000100

101

102

103

Time (min)

Cou

nts

Step 1Step 2Step 3

0 5 10 15 20 25 30 35

101

102

103

Decay time, t (hrs)

Cou

nts

y2754 keV=49*exp(�0.050*t)T1/2 =13.86 hrs

y1369 keV=100*exp(�0.044*t)T1/2 =15.75 hrs

Background

Activated sample B. Ayaz-Maierhafer, J.P. Hayward, Z.W. Bell, L.A. Boatner, R.E. Johnson, “Measurements of thermal neutron response in Cherenkov glassed designed for MeV photon detection,” submitted to IEEE Transactions on Nuclear Science, June 2012.

0 100 200 300 400 500 600 700100

101

102

103

Time (min)

Cou

nts

Step 1Step 2Step 3

0 500 1000 1500 2000 2500 3000 3500100

101

102

103

104B2−InLead Bkg spectrum

Energy (keV)

Coun

ts

0 500 1000 1500 2000 2500 3000 3500100

101

102

103

104B2−InLead phosphate spectrum after− 1−hrs

−−−>

116 In

= 417

keV

−−−>

116 In

= 819

keV

−−−>

116 In

= 109

7 keV

−−−>

116 In

= 129

4 keV

−−−>

116 In

= 150

8 keV

−−−>

116 In

= 175

3 keV

−−−>

116 In

= 211

2 keV

0 2 4 6 8 10 12

101

102

103

104

Decay time, t (hrs)

Cou

nts

y1508keV=5130*(�0.74*t)T1/2= 56 min

y1753keV=580*exp(�0.75*t)T1/2= 55 min

418 keV

819 keV

1294 keV

1508 keV

1753 keV

2112 keV

Activated sample

Measurements for Glass B (Indium Lead Phosphate)

Background

B. Ayaz-Maierhafer, J.P. Hayward, Z.W. Bell, L.A. Boatner, R.E. Johnson, “Measurements of thermal neutron response in Cherenkov glassed designed for MeV photon detection,” submitted to IEEE Transactions on Nuclear Science, June 2012. Basic Research Technical Review, July 2012

Time dependent radiation measurement for glasses that are less response to n flux

Glass C

0 200 400 600 800 1000100

101

102

103

Time (min)

Cou

nts

Step 1Step 2

0 500 1000 1500100

101

102

103

Time (min)

Cou

nts

BkgActivated�glass�over�PMT

0 500 1000 1500100

101

102

103

Time (min)

Cou

nts

BkgActivated−glass−over−PMT

Glass D

Glass E

B. Ayaz-Maierhafer, J.P. Hayward, Z.W. Bell, L.A. Boatner, R.E. Johnson, “Measurements of thermal neutron response in Cherenkov glassed designed for MeV photon detection,” submitted to IEEE Transactions on Nuclear Science, June 2012.

Neutron activation summary

²  Indium Lead Phosphate glass (B) was the most responsive to thermal neutron ²  Sodium Barium Phosphate glass (A) showed some thermal neutron response

from energetic betas and gammas produced by activation ²  The Lithium Lead Phosphate glass (C) was the least responsive glass out of

those reported here ²  In summary, the Lithium Lead Phosphate glass (C) is the best candidate to use

for discrimination against neutron activation among this sample set ²  This research suggests that glass constituents with low thermal neutron

capture (n,γ) probabilities, containing isotopes with low abundances, perhaps producing long half-life activation products with low gamma and beta energies, are good candidates to use when attempting to minimize the response to thermal neutrons

²  Among these glasses, E is the most dense (4.587 g/cm3, comparable to that of the CsI scintillator) and thus should have the best detection efficiency for counting MeV photons


Measured response to isotopic gamma sources

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Calcium sodium phosphate cladding glass with In2O3 (“F”)

Zinc borate glass with Lu2O3 (“G”)

J.P. Hayward, Z.W. Bell, L.A. Boatner, C.L. Hobbs, R.E. Johnson, J.O. Ramey, G.E. Jellsion, Jr., “Characterizing the response of Cherenkov glass detectors with isotopic gamma-ray sources,” Journal of Radioanalytical and Nuclear Chemistry, accepted in June 2012, available online.

Simulated response to isotopic gamma sources

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Glass F Glass G

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227Ac-13C Neutron/Gamma Source

•  Source of 6 MeV gammas from 13C(α,n)16O •  Modeled neutron and gamma production with

SOURCES4C •  Modeled γ measurement with MCNP5 •  Measured γ production with HPGe •  227Ac provides

•  5 daughters with energetic α particles •  Gammas mostly below 1 MeV (useful for energy

calibration) •  21.8 year half-life

Paper NP1M-216 at the 2011 IEEE Nuclear Science Symposium, Valencia, Spain


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Decay Chain

227Ac→227Th→223Ra →219Rn →215Po →211Pb →211Bi →207Tl →207Pb ↘223Fr ↗ ↘211Po ↗

Ea(MeV)= 4.9 5.7-6 5.7 6.4-6.8 7.4 6.3,6.6 7.4

•  Modeled 10 Ac compounds

•  Evaluated mass of source as function of Ac dilution to make 2x104 γ/s

•  1.8 – 2.0 mg Ac (1.3 – 1.4 Ci)



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•  Fabrication •  227Ac oxide dissolved in HCl •  Added MeOH; transferred 10 mCi to 10 mg 13C;

rinsed with MeOH and dried •  15 mg 13C cap added •  Expected 2000 6 MeV γ/s Paper NP1M-216 at the 2011

IEEE Nuclear Science Symposium, Valencia, Spain


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•  Measured production 940±88 γ/s •  Factor of 2 caused by packing density of 13C •  Evidence of expected neutron production

Ac, n capture, natural γ

6129 keV γ + escapes

Fe captures


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•  SOURCES4C code is sufficiently accurate for source design

•  Density of 13C compact of paramount importance •  219Rn (4 s half-life) diffusion into the source head

space is unimportant •  Neutron production can be as high as 49 n/106 α •  6 MeV gamma yield can be as high as 5 γ/106 α



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Accomplishments: publications

•  Two papers from this effort accepted for publication •  J.P. Hayward, Z.W. Bell, L.A. Boatner, C.L. Hobbs, R.E. Johnson, J.O. Ramey, G.E. Jellsion,

Jr., “Characterizing the response of Cherenkov glass detectors with isotopic gamma-ray sources,” Journal of Radioanalytical and Nuclear Chemistry, accepted in June 2012.

•  J.P. Hayward, Z.W. Bell, L.A. Boatner, C.L. Hobbs, R.E. Johnson, J.O. Ramey, G.E. Jellison, Jr., “Simulated Response of Cherenkov Glass Detectors to MeV Photons,” Journal of Radioanalytical and Nuclear Chemistry, accepted in June 2012.

•  One more submitted (under review) and an additional one nearly ready •  B. Ayaz-Maierhafer, J.P. Hayward, Z.W. Bell, L.A. Boatner, R.E. Johnson, “Measurements of

thermal neutron response in Cherenkov glassed designed for MeV photon detection,” submitted to IEEE Transactions on Nuclear Science, June 2012.

•  3 conference presentations made •  2 at IEEE NSS, 2011, Knoxville, TN (Hayward, Bell)

•  6 MeV simulations, 227Ac-13C 6 MeV gamma source •  1 at SORMA, 2012, San Francisco, CA (Slow neutron measurements, Ayaz-Maierhafer)

•  Related work: DTRA project on fab. of neutron-sensitive Cherenkov glass prototype system is underway (ORNL is prime), 3 related patents obtained (patents 7,601,965; 7,629,588; 7,952,075 issued on 10/13/09; 12/8/09; 5/31/11)


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Accomplishments: Education and training of personnel

•  Graduate students: Mitchell Laubach (NE), Clint Hobbs (NE, M.S. in Summer 2011), John Sparger (NE), Sam Donnald (NE, M.S. in Summer 2012), Cole Lillard (NE)

•  Undergrads: Shelby Brackett (Tenn Tech), Rose Johnson (NE/Chem), Brady Miller (NE)

•  Post-doc: Birsen Ayaz-Maierhafer (NE) •  2 other post-docs and 3 other undergrads have been involved


Education integration

•  Advanced Topics and Laboratory Techniques in Radiation Detection and Measurement, Fall 2011 (NE 697); 10 PhD-level graduate students

•  Advanced topic lectures relevant to radiation instrumentation, nuclear security and safeguards application; 7 subject matter experts from ORNL lecture in nuclear safeguards area

•  Student-led lab development and lectures •  Labs developed included Medical Accelerator Measurements of Photon

Production from U, Pb, and Low Z Targets; Material and Detector Influences on Timing Uncertainty for Coincidence Setups with Scintillation Detectors; Cf-252 Characterization Through Higher-Order Time Correlation Statistics; and Digital data acquisition and pulse processing for coincidence measurements

•  Lectures include accelerator treatment heads, fast triggering techniques,

•  Several new nuclear security classes added to our graduate curriculum, and UT Institute for Nuclear Security began…


PI Awards •  Recipient of UCOR Faculty Fellowship in Nuclear Engineering

•  Continuous award to support excellence at UT-Knoxville from new College of Engineering endowment given by URS/CH2M Hill Oak Ridge LLC

•  http://oakridgetoday.com/2012/07/05/ucor-donates-250000-ut-engineering-fellowship •  http://www.engr.utk.edu/news/atcoe/atcoe_07_06_12.html

•  Recipient of American Society of Engineering Education (ASEE) New Faculty Research Award •  2nd place awarded from Southeastern Section for record of excellence in

research and teaching


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Conclusions •  113 glass samples have been fabricated from 22 families of glass formers, most optically clear •  A few large samples (>200 g) fabricated •  Cherenkov detectors are, in fact, not blind to prompt flash, even in-beam and out of shielding, and energy-dependent response observed •  Our investigation suggests that glass Cherenkov detectors may be promising in looking at prompt gammas in active interrogation scenarios

•  Ultra-fast and high efficiency compared to “fast” plastic scintillator, also low cost in large volume •  Need to establish that prompt gamma signatures, although expected to be plentiful, are able to be distinguished from prompt active background

•  Knowledge of measured neutron response can guide selection of Cherenkov glass for a particular application; other sources of passive and active photon background were studied as well •  Two peer-reviewed publications accepted and online, a few more expected by next year •  Significant student and postdoc involvement, collaboration with ORNL and now IAC


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Future Direction •  We will investigate the prompt timing characteristics of the Cherenkov effect (and higher γ energies) by exposing glass samples to the interrogation pulse of the fast pulse LINAC at the Idaho Accelerator Center (Year 4) •  Start to determine how prompt gamma (and gamma multiplicity) signal may be observed, how statistical analysis may be of benefit in this effort


References

•  Sowerby, B.D., “Cerenkov Detectors for Low Energy Gamma Rays,” NIM, 97, 1971, pp. 145-149. •  G. F. Knoll, Radiation, Detection, and Measurement, 3rd ed., Hoboken, NJ: Wiley, 2000, p. 711. •  Z.W. Bell, L.A. Boatner, “Neutron detection via the Cherenkov effect,” IEEE Trans. Nuc. Sci. 57 (2010) 3800. •  Patent 7,601,965, issued 10/13/09, infrared neutron detector based on the Cherenkov effect. •  Patent 7,629,588, issued 12/8/09. •  Patent 5,812,729, issued 9/22/98, very high numerical aperture light transmitting device.


Thanks for your attention! -- Questions??


Appendix


Simulation: MeV photons

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•  Response simulated for actual and m2 sizes (standoff)

•  Increased thickness improves efficiency while reducing light collection and timing performance

•  Layered approach retains all advantages

•  Considering high efficiency for MeV γs, selectivity based upon photoelectron production (unexpected), timing

•  Photoelectron production follows energy deposited

J.P. Hayward, Z.W. Bell, L.A. Boatner, et al., “Simulated response of Cherenkov glass detectors to MeV photons,” submitted to IEEE Trans. Nuc. Sci., June 2011.


Digital Silicon Photomultipliers •  Parametric Study for assessment of dSiPM for

•  Fast Inorganic Scintillators (e.g. LSO) •  Organic Scintillators (plastic scint.) •  Cherenkov Glasses

•  Parameterized configurations for optimum timing performance •  Single photon measurements on analog SiPMs below

Documents

Glasses for detection of penetrating radiation via the Cherenkov