A5029396846- Radiation Detection and Scintillator Technologies
- Nuclear Physics and Applications
- Nuclear physics research studies
- Atomic and Subatomic Physics Research
- Advanced Semiconductor Detectors and Materials
- Luminescence Properties of Advanced Materials
- Nuclear reactor physics and engineering
- Medical Imaging Techniques and Applications
- Advanced Frequency and Time Standards
- Nuclear Materials and Properties
- Cold Atom Physics and Bose-Einstein Condensates
- Particle physics theoretical and experimental studies
- Radioactivity and Radon Measurements
- Quantum Chromodynamics and Particle Interactions
- Radiopharmaceutical Chemistry and Applications
- Radioactive contamination and transfer
- Radioactive Decay and Measurement Techniques
- Perovskite Materials and Applications
- Atomic and Molecular Physics
- Particle accelerators and beam dynamics
- Digital Radiography and Breast Imaging
- Neutrino Physics Research
- Quantum, superfluid, helium dynamics
- CCD and CMOS Imaging Sensors
- Radioactive element chemistry and processing
Lawrence Livermore National Laboratory
2014-2023
University of California, Berkeley
2009-2013
Transparent plastic scintillators based on polyvinyltoluene (PVT) have been fabricated with high loading of bismuth carboxylates for gamma spectroscopy, and lithium neutron detection. When activated a combination standard fluors, 2,5-diphenyloxazole (PPO) tetraphenylbutadiene (TPB), light yields 15 wt% tripivalate 5000 Ph/MeV are measured. A PVT formulation including 30 pivalate PPO offers both pulse shape discrimination, capture peak at ~400 keVee. In another configuration, bismuth-loaded...
The neutron-induced fission cross section of $^{238}\mathrm{Pu}$ was determined using the surrogate ratio method. $(n,f)$ over an equivalent neutron energy range 5--20 MeV deduced from inelastic $\ensuremath{\alpha}$-induced reactions on $^{239}\mathrm{Pu}$, with $^{235}\mathrm{U}$($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ and $^{236}\mathrm{U}$($\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ used as references. These reference reflect...
We report on the development of two new mechanically rugged, high light yield transparent ceramic scintillators: (1) Ce-doped Gd-garnet for gamma spectroscopy, and (2) Eu-doped Gd-Lu-bixbyite radiography. GYGAG(Ce) garnet ceramics offer ρ = 5.8g/cm<sup>3</sup>, Z<sub>eff</sub> 48, principal decay <100 ns, 50,000 Ph/MeV. Gdgarnet scintillators best energy resolution any oxide scintillator, as good R(662 keV) 3% (Si-PD readout) small sizes typically < 5% cubic inch sizes. For...
Thallium bromide (TlBr) is a compound semiconductor with band gap of 2.68 eV making it ideal for room temperature radiation detection. The high atomic numbers, 81 and 35, the density 7.56 g/cm3 give excellent gamma-ray stopping power. TlBr cubic material that melts congruently at relatively low (~ 480 C). These properties make easy to grow good quality crystals yield. As result improvements in purification mobility-lifetime product electrons, µτe, now on order 10-2 cm2/V, which similar CZT....
GYGAG(Ce) transparent ceramic garnet scintillators were irradiated with electrons from 0.5 to 2 MeV fluences <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{16}\,\,\text{e}^{-}$ </tex-math></inline-formula> /cm <sup xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> notation="LaTeX">$10^{19}\,\,\text{e}^{-}$ , corresponding doses 0.3 310 Gigarad. Absorption spectra measured before and after...
Breakthrough energy resolution, R(662keV) < 4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce). Transparent ceramic GYGAG(Ce), a peak emission wavelength of 550 nm that is better matched to Silicon photodetectors than standard PMTs. We are therefore developing spectrometer based on pixelated GYGAG(Ce) photodiode array can provide R(662 keV) = 3.6%. In comparison, large 1-2 in<sup>3</sup> size ceramics we obtain 4.6% PMT...
The detection of illicit nuclear materials is a major tool in preventing and deterring terrorism. task extremely difficult because physical limitations radiation detectors, shielding by intervening cargo materials, the presence background noise. We aim at enhancing capabilities detectors with algorithmic methods specifically tailored for data. This paper describes novel graph-theory-based methodology this task. research considers first time utilization supervised normalized cut (SNC) data...
We have used superconducting high-resolution radiation detectors to measure the energy level of metastable $^{235m}\mathrm{U}$ as 76.737 \ifmmode\pm\else\textpm\fi{} 0.018 eV. The isomer is created from \ensuremath{\alpha} decay $^{239}\mathrm{Pu}$ and embedded directly into detector. When subsequently decays, fully contained within detector independent mode or chemical state uranium. calibrated using an comb a pulsed UV laser. A comparable measurement $^{229m}\mathrm{Th}$ nucleus would...
This paper is the fifth in a series of articles on basic physics light yield nonproportionality scintillators. Here, we compare and contrast as registered by gamma rays high-energy electrons. As has been noted past, these two types data have different curve shapes (for plots against electron or energy). Herein, show how experimental can be calculated from response accounting for distribution high energy electrons created photon via photoelectric interaction. Similarly, measure model...
The surrogate ratio method (SRM) was employed in the first experimental determination of $^{231}\mathrm{Th}$$(n,f)$ cross section, relative to $^{235}\mathrm{U}$$(n,f)$ over an equivalent neutron energy range $360$ keV $10$ MeV. $^{230}\mathrm{Th}$$(n,f)$ section also deduced using SRM, $^{234}\mathrm{U}$$(n,f)$ $220$ $25$ desired compound nuclei were populated ($^{3}\mathrm{He}$,$^{3}\mathrm{He}$$'$) and ($^{3}\mathrm{He}$$,\ensuremath{\alpha}$) reactions on targets $^{232}\mathrm{Th}$...
This paper is the third in a series of articles on basic physics nonproportionality scintillators. Here, we focus temperature dependence six scintillators, NaI(Tl), CsI(Tl), CsI(Na), CeBr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , LaBr (Ce), and undoped SrI xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> report their curves at -40 <sup xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, 0 C + 40 C. We fit data to modified...
Background: Neutron-induced fission cross-section data are needed in various fields of applied and basic nuclear science. However, cross sections short-lived nuclei difficult to measure directly due experimental constraints.Purpose: The first determination the neutron-induced section ${}^{239}$Np at nonthermal energies was performed. This minor actinide is waiting point ${}^{240}$Pu production a reactor.Method: surrogate ratio method employed indirectly deduce ${}^{239}\text{Np}(n,f)$...
Measurements of states excited by nuclear resonance fluorescence in $^{237}\mathrm{Np}$ were performed using a bremsstrahlung beam. Fifteen new observed the region 1.7 to 2.5 MeV. They can be used detect or assay nondestructively for applications security and safeguards. The are populated with similar strength as those found previously $^{235}\mathrm{U}$ $^{239}\mathrm{Pu}$ but spread out more energy.
Development of the Europium-doped Strontium Iodide scintillator, SrI2(Eu2+), has progressed significantly in recent years. SrI2(Eu2+) excellent material properties for gamma ray spectroscopy: high light yield (<80,000 ph/MeV), proportionality, and effective atomic number (Z = 49) photoelectric cross-section. High quality 1.5" 2" diameter boules are now available due to rapid advances SrI2(Eu) crystal growth. In these large crystals, optical self-absorption by Eu<sup>2+</sup> degrades...
Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI<sub>2</sub>(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI<sub>2</sub>(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution <3% at 662 keV with 1.5" x crystals is routinely achieved, by employing either small taper the top or digital readout technique. These methods overcome light-trapping, in which...
New transparent ceramic scintillators offer advantages for applications in gamma spectroscopy and X-ray imaging. For spectroscopy, excellent light yield, material uniformity, yield proportionality, mechanical environmental ruggedness can be achieved polycrystalline oxide garnets. We have fabricated 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Ce-doped Gd garnet ceramics. GYGAG(Ce) ceramics ρ = 5.8g/cm , Z <sub...
Plastic scintillators incorporating 8 weight percent elemental Bismuth offer enhanced sensitivity and distinct photopeak spectra in the <1000 keV range typically used radiation portal monitors. The Bismuth-loaded plastic is based on polyvinyl toluene with standard singlet fluors. It produces ~6,000 photons/MeV a maximum emission at 430 nm ~10 ns decay. Energy resolution of 49% 59.5 16% 662 are obtained for 14 in<sup>3</sup> scintillator plate. Count rates compared to same size reveal...
Thallium bromide (TlBr) crystals subjected to hydrochloric acid (HCl) chemical treatments have been shown advantageously affect device performance and longevity in TlBr‐based room temperature radiation detectors, yet the exact mechanisms of improvements remain poorly understood. Here, we investigate influence several HCl on device‐grade TlBr describe changes composition electronic structure surface. Composition analysis depth profiles obtained from secondary ion mass spectrometry (SIMS)...
We are working on scale up of several new plastic scintillator compositions. One composition uses Iridium complex fluors to obtain 3x higher light yields and high α/β ratios, for improved particle (alpha, neutron, fission product) detection imaging. Other compositions include loading Bismuth gamma spectroscopy with Lithium neutron detection. Plastics containing 21 wt% elemental an Ir fluor provide strong photopeaks R(662 keV) ~9%. When activated standard organic fluors, 10 in <sup...