Gamma-ray rejection, or detection, with gadolinium as a converter

Kandlakunta, Praneeth; Cao, Lei

doi:10.1093/rpd/ncs031

Cited by 11 publications

(10 citation statements)

References 6 publications

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“…These phenomena, however, boost the c-ray detection efficiency when Gd is combined with GaN or other semiconducting materials. 98,99 A rare-earth-doped GaN thin film might lead to significant improvements in device performance in sensor applications; GaN is potentially neutron sensitive when doped with Gd. 100,101 Melton et al 102 found that the carrier concentration in Gd-doped GaN increases as a result of the Gd doping.…”

Section: Neutron Detectionmentioning

confidence: 99%

Review of using gallium nitride for ionizing radiation detection

Wang

Mulligan

Brillson

et al. 2015

Applied Physics Reviews

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With the largest band gap energy of all commercial semiconductors, GaN has found wide application in the making of optoelectronic devices. It has also been used for photodetection such as solar blind imaging as well as ultraviolet and even X-ray detection. Unsurprisingly, the appreciable advantages of GaN over Si, amorphous silicon (a-Si:H), SiC, amorphous SiC (a-SiC), and GaAs, particularly for its radiation hardness, have drawn prompt attention from the physics, astronomy, and nuclear science and engineering communities alike, where semiconductors have traditionally been used for nuclear particle detection. Several investigations have established the usefulness of GaN for alpha detection, suggesting that when properly doped or coated with neutron sensitive materials, GaN could be turned into a neutron detection device. Work in this area is still early in its development, but GaN-based devices have already been shown to detect alpha particles, ultraviolet light, X-rays, electrons, and neutrons. Furthermore, the nuclear reaction presented by 14N(n,p)14C and various other threshold reactions indicates that GaN is intrinsically sensitive to neutrons. This review summarizes the state-of-the-art development of GaN detectors for detecting directly and indirectly ionizing radiation. Particular emphasis is given to GaN's radiation hardness under high-radiation fields.

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Section: Neutron Detectionmentioning

confidence: 99%

Review of using gallium nitride for ionizing radiation detection

Wang

Mulligan

Brillson

et al. 2015

Applied Physics Reviews

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“…6 A). All further experiments were therefore carried out using a 10 μm Gd layer, which was close to the 12 μm predicted previously for high efficiency [ 16 ].…”

Section: Resultsmentioning

confidence: 78%

“…This situation is exacerbated when compared with low natural neutron background fluence. There are two sources contributing to γ-ray background: external γ-rays accompanying 252 Cf and internal prompt γ-rays [ 16 ] (Eqs 1 and 2 ) due to Gd's ( Z = 64) high probability of interaction that produces moderate energy electrons by Compton, photoelectric and electron–positron pair processes [ 17 ]. These factors make it easy to record false positives while detecting SNMs, since an electron from γ-interaction is not easily distinguished from ICEs.…”

Section: Resultsmentioning

confidence: 99%

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

Pfeifer

Achyuthan

Allen

et al. 2017

Journal of Radiation Research

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Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and Kα,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.

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“…Gd [67]. This explains the extra bump around relatively high energies in the simulated neutron spectrum with updated Geant4.…”

Section: Modeling Gadolinium Neutron Capture Gamma Emissionmentioning

confidence: 75%

“…The simulated individual gamma emission spectrum from Geant4.9.4.p04 (photon evaporation model) is shown in red, and the individual gamma spectrum from Geant4.9.5.p01 (G4NDL) is shown in blue. The measured individual gamma spectrum from 155 Gd and 157 Gd together [66] is shown in black solid line, and the spectrum measured from natural Gd [67] is shown in black dashed line. G4NDL agrees with the measured spectra much better than photon evaporation model at high energy.…”

Section: Modeling Gadolinium Neutron Capture Gamma Emissionmentioning

confidence: 99%

High-Energy Neutron Backgrounds for Underground Dark Matter Experiments

Chen¹

2016

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A B S T R A C TDirect dark matter detection experiments usually have excellent capability to distinguish nuclear recoils, expected interactions with Weakly Interacting Massive Particle (WIMP) dark matter, and electronic recoils, so that they can efficiently reject background events such as gamma-rays and charged particles. However, both WIMPs and neutrons can induce nuclear recoils. Neutrons are then the most crucial background for direct dark matter detection. It is important to understand and account for all sources of neutron backgrounds when claiming a discovery of dark matter detection or reporting limits on the WIMP-nucleon cross section. One type of neutron background that is not well understood is the cosmogenic neutrons from muons interacting with the underground cavern rock and materials surrounding a dark matter detector.The Neutron Multiplicity Meter (NMM) is a water Cherenkov detector capable of measuring the cosmogenic neutron flux at the Soudan Underground Laboratory, which has an overburden of 2090 meters water equivalent. The NMM consists of two 2.2-tonne gadolinium-doped water tanks situated atop a 20-tonne lead target. It detects a high-energy (>∼ 50 MeV) neutron via moderation and capture of the multiple secondary neutrons released when the former interacts in the lead target. The multiplicity of secondary neutrons for the high-energy neutron provides a benchmark for comparison to the current Monte Carlo predictions. Combining with the Monte Carlo simulation, the muon-induced high-energy neutron flux above 50 MeV is measured to be (1.3 ± 0.2) × 10 −9 cm −2 s −1 , in reasonable agreement with the model prediction. The measured multiplicity spectrum agrees well with that of Monte Carlo simulation for multiplicity below 10, but shows an excess of approximately a factor of three over Monte Carlo prediction for multiplicities ∼ 10 − 20.In an effort to reduce neutron backgrounds for the dark matter experiment SuperCDMS SNO-LAB, an active neutron veto was developed. It is estimated that the current design of the neutron veto with a 40 cm thick layer of boron-doped liquid scintillator can achieve a > 90% efficiency for tagging the single-scatter neutrons. In addition, a one-quarter scale prototype detector for neutron veto has been built and tested. H I G H -E N E R G Y N E U T R O N B A C K G R O U N D S F O R U N D E R G R O U N D D A R K M A T T E R E X P E R I M E N T S Y U C H E N B . S . , B E I J I N G I N S T I T U T E O F T E C H N O L O G Y , B E I J I N G , C H I N A ( 2 0 0 6 ) M . S . , B E I J I N G N O R M A L U N I V E R S I T Y , B E I J I N G , C H I N A ( 2 0 0 9 ) D I S S E R T A T I O N S U B M I T T E D I N P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F D O C T O R O F P H I L O S O P H Y I N P H Y S I C S S Y R A C U S E U N I V E R S I T Y D E C E M B E Dark MatterThere is compelling evidence for the existence of dark matter from astronomical and cosmological observations. In this chater, I will briefly present modern cos...

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Gamma-ray rejection, or detection, with gadolinium as a converter

Cited by 11 publications

References 6 publications

Review of using gallium nitride for ionizing radiation detection

Review of using gallium nitride for ionizing radiation detection

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

High-Energy Neutron Backgrounds for Underground Dark Matter Experiments

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