Proton Excitation of Continuous Emission in the Noble Gases*

Stewart, T. E.; Hurst, G. S.; Bortner, T.E.; Parks, James E.; Martin, F. W.; Weidner, H.

doi:10.1364/josa.60.001290

Cited by 57 publications

(5 citation statements)

References 12 publications

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“…These unstable, excited diatomic molecules radiatively dissociate with emissions in the FUV. Figure 1 reproduces the emission spectra of Ar 2 * , Kr 2 * , and Xe 2 * from the work of [10]. The emission from He 2 * and Ne 2 * is below the absorption edge of the MgF 2 window and cannot be detected by our system.…”

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confidence: 70%

“…In our experimental system, the 3 He(n,tp) reaction in the presence of these gases yields a signal of up to 1000 times greater than that which occurs in the presence of 4 He or Ne. It is well known [4,10,[13][14][15] that energetic particles traversing a noble gas will form excimers. These unstable, excited diatomic molecules radiatively dissociate with emissions in the FUV.…”

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confidence: 99%

“…Figure 1.Emission spectra of the excimers of Ar, Kr, and Xe produced by the passage of 4 MeV protons through the rare gases at a pressure of 53 kPa. Redrawn from[10]. Figure2.…”

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confidence: 99%

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Far-ultraviolet signatures of the H3e(n,tp) reaction in noble gas mixtures

Hughes

Coplan

Thompson

et al. 2010

Applied Physics Letters

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Previous work showed that the 3 He(n,tp) reaction in a cell of 3 He at atmospheric pressure generated tens of far-ultraviolet photons per reacted neutron. Here we report amplification of that signal by factors of 1000 and more when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble-gas excimer emissions, and that the nuclear reaction energy is converted to far-ultraviolet radiation with efficiencies of up to 30%. The results have been placed on an absolute scale through calibrations at the NIST SURF III synchrotron. They suggest possibilities for highefficiency neutron detectors as an alternative to existing proportional counters.The 3 He(n,tp) process, in which a neutron reacts with a helion to produce a proton and a triton with excess energy of 764 keV, is one of the best-characterized neutron reactions [1]. This reaction is the trigger mechanism for the 3 He proportional counter, which is presently one of the most widely-used neutron detectors [2]. Here we discuss using the same trigger reaction to initiate far-ultraviolet (FUV) optical emissions, rather than electrical discharges. We have found cases in which about one-third of the nuclear reaction energy is converted to FUV emissions by noble-gas excimer molecules. Such high conversion efficiencies have been encountered previously in electric discharges [3][4][5][6] , irradiation of noble gases by beams of electrons [7-9] and proton [10] bombardment of noble gases. Here they are reported for the first time in the context of a nuclear reaction and put on a quantitative basis needed to evaluate their applicability in a new FUV-based neutron detector.Following previous work [11], we started with a gas cell containing pure 3 He and 3 He/ 4 He mixtures, exposed to neutrons with a deBroglie wavelength of 0.384 ± 0.004 nm, produced at the NIST Center for Neutron Research. At this wavelength, the cross section for the reaction 3 He(n,tp) reaction is (1.135 ± 0.012) x 10 -20 cm 2 . We measured FUV emissions in the cell with a filter-detector package that was calibrated at the NIST SURF III Synchrotron Ultraviolet Radiation Facility. This package is discussed below, as are the procedures for absolute measurements of the neutron flux and modeling of the optical detection system. The combination of measurement and modeling enables us to determine the number of FUV photons produced per neutron reaction.In the work with pure 3 He and 3 He/ 4 He mixtures the source of the optical signal was determined to be Lyman α radiation from the 2p states of the 1 H and 3 H formed as neutralization and excitation products of the 3 He(n,tp) process [11,12]. We found that, at a 3 He pressure of 100 kPa, tens of FUV photons are produced for every reacted neutron. This number is already encouraging as concerns the prospects for an absolute neutron detector based on FUV emissions vs. the electrical discharges that drive proportional counters, as discussed previously [11]. When mixtures of Ar, Kr or Xe are added to the 3 He...

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Far-ultraviolet signatures of the H3e(n,tp) reaction in noble gas mixtures

Hughes

Coplan

Thompson

et al. 2010

Applied Physics Letters

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“…This mechanism of photon emission, referred to as excimer scintillation, provides a unique method for detecting neutrons. Ar, Kr, and Xe produce excimers with wavelengths between 105 nm and 190 nm 1,2 , as shown in the emission spectra in Figure 1. A combination of featureslarge light output, fast decay, transparency to excimer radiation, unique decay structure, and immunity to radiation damagemake noble gases particularly suitable as radiation detection media 3 .…”

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confidence: 96%

“…The use of NGE scintillation in particle detection began in the 1950s and extended into the 1980s with measurements of energy resolution and gamma sensitivity 3,[9][10][11][12][13] . The mechanisms of excimer formation and decay have been investigated both experimentally 2,14,15 and theoretically [16][17][18] . Recently, liquid noble gas detectors have played a significant role in efforts to detect the neutrino mass and magnetic moment, and dark matter candidates, such as weakly interacting massive particles 19 .…”

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Noble gas excimer scintillation following neutron capture in boron thin films

McComb

Coplan

Al-Sheikhly

et al. 2014

Journal of Applied Physics

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Far-ultraviolet scintillation signals have been measured in heavy noble gases (argon, krypton, xenon) following boron-neutron capture (10B(n,α)7Li) in 10B thin films. The observed scintillation yields are comparable to the yields from some liquid and solid neutron scintillators. At noble gas pressures of 107 kPa, the number of photons produced per neutron absorbed following irradiation of a 1200 nm thick 10B film was 14 000 for xenon, 11 000 for krypton, and 6000 for argon. The absolute scintillation yields from the experimental configuration were calculated using data from (1) experimental irradiations, (2) thin-film characterizations, (3) photomultiplier tube calibrations, and (4) photon collection modeling. Both the boron films and the photomultiplier tube were characterized at the National Institute of Standards and Technology. Monte Carlo modeling of the reaction cell provided estimates of the photon collection efficiency and the transport behavior of 10B(n,α)7Li reaction products escaping the thin films. Scintillation yields increased with gas pressure due to increased ionization and excitation densities of the gases from the 10B(n,α)7Li reaction products, increased frequency of three-body, excimer-forming collisions, and reduced photon emission volumes (i.e., larger solid angle) at higher pressures. Yields decreased for thicker 10B thin films due to higher average energy loss of the 10B(n,α)7Li reaction products escaping the films. The relative standard uncertainties in the measurements were determined to lie between 14% and 16%. The observed scintillation signal demonstrates that noble gas excimer scintillation is promising for use in practical neutron detectors.

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Chemistry in mixtures of Kr with Ar and He illuminated with Kr resonance radiation

Young¹

1982

Int J of Chemical Kinetics

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The formation and destruction of excited rare-gas dimers have been studied using resonance optical excitation of high-pressure gas mixtures containing Kr. From an analysis of the resulting emission, 19 reaction rate coefficients have been inferred. It is concluded that atom-atom interchange processes play a major role in rare-gas eximer formation, and that stepwise relaxation down the eximer vibrational ladder is less important than multistep relaxation due to atom-atom exchange in the excited eximer.Of the 29 reactions listed in Table I and the 23 reactions listed in Table I1 which could occur in mixtures of Kr with Ar or He, reactions (l), (3) + (4), and (18) have been measured by Turner [32] (as 1.3 X and 7.6 X in s-l, cm3/s, and cm6/s, as appropriate), while Hughes' has measured ky, kq, and k17 (5.3 X lo6, 5.5 X This paper describes spectroscopic measurements on mixtures of Kr and other gases when this mixture is excited by the 123.6-nm resonance line of Kr from an optically thick source. These measurements are interpreted to give the reaction rates of reactions (relative to the reaction rates of reactions Hughes [31] has measured k7 to be 5.3 X lo6 sl, k3 + kq = 5.5 X lo-?' , and h17 = 1.75 X 108. 4 X 1.8 X lo8).

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Proton Excitation of Continuous Emission in the Noble Gases*

Cited by 57 publications

References 12 publications

Far-ultraviolet signatures of the H3e(n,tp) reaction in noble gas mixtures

Far-ultraviolet signatures of the H3e(n,tp) reaction in noble gas mixtures

Noble gas excimer scintillation following neutron capture in boron thin films

Chemistry in mixtures of Kr with Ar and He illuminated with Kr resonance radiation

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