Liquefied Noble Gas (LNG) detectors for detection of nuclear materials

Abstract

Liquefied-noble-gas (LNG) detectors offer, in principle, very good energy resolution for both neutrons and gamma rays, fast response time (hence high-count-rate capabilities), excellent discrimination between neutrons and gamma rays, and scalability to large volumes. They do, however, need cryogenics. LNG detectors in sizes of interest for fissionable material detection in cargo are reaching a certain level of maturity because of the ongoing extensive R&D effort in highenergy physics regarding their use in the search for dark matter and neutrinoless double beta decay. The unique properties of LNG detectors, especially those using Liquid Argon (LAr) and Liquid Xenon (LXe), call for a study to determine their suitability for Non-Intrusive Inspection (NII) for Special Nuclear Materials (SNM) and possibly for other threats in cargo.

Pulse-shape discrimination and energy resolution of a liquid-argon scintillator with xenon doping

“…Hence, doping of xenon appears to reduce fluctuation in detected photons. A previous study with this detector also observed resolution improvement to 3% from 5% σ at 662 keV when doping pure argon with about 2000 ppm xenon [7].…”

“…Previous studies have shown that the addition to argon of a few parts per million of xenon results in improved PSD [1], better energy resolution [7], and faster decay time [20]. As show in Table I, pure argon produces a wavelength of 128 nm, with decay times of 7 ns and 1.6 µs.…”

“…While the direct light yield is not expected to improve, previous studies have observed factor-of-two increases in detected light (signal yield), attributed to higher efficiency of the wavelength shifter at the longer wavelengths of xenon emission [20,24]. This improved signal yield results in better energy resolution due to better statistics [1,7,20]. As the xenon doping shifts much of the slow-light component to earlier times, the waveforms for different particles become more similar [1].…”

“…The ions can recombine with electrons to form excited atoms, in turn producing excimers and then scintillation light. [4], [6], AND [7] The excimers can exist in two states, known as singlet and triplet. It is thought that the ratio of atomic excitations to ionizations is much greater for nuclear recoils than for electron recoils [8,9].…”

Reflectance dependence of polytetrafluoroethylene on thickness for xenon scintillation light

“…Liquid xenon (LXe) detectors have found many applications based on their capability to provide both calorimetry and imaging of particle interactions. Particularly fruitful applications include dark matter [1,2,3,4] and lepton flavor violating [5] searches, neutrinoless double beta decay detectors [6], gamma-ray physics experiments [7], medical imaging [8], and neutron detection for Homeland Security [9].…”