Ion-beam excitation of liquid argon

Abstract

The scintillation light of liquid argon has been recorded wavelength and time resolved with very good statistics in a wavelength interval ranging from 118 nm through 970 nm. Three different ion beams, protons, sulfur ions and gold ions, were used to excite liquid argon. Only minor differences were observed in the wavelengthspectra obtained with the different incident particles. Light emission in the wavelength range of the third excimer continuum was found to be strongly suppressed in the liquid phase. In time-resolved measurements, the time structure of the scintillation light can be directly attributed to wavelength in our studies, as no wavelength shifter has been used. These measurements confirm that the singlet-to-triplet intensity ratio in the second excimer continuum range is a useful parameter for particle discrimination, which can also be employed in wavelength-integrated measurements as long as the sensitivity of the detector system does not rise steeply for wavelengths longer than 190 nm. Using our values for the singlet-to-triplet ratio down to low energies deposited a discrimination threshold between incident protons and sulfur ions as low as ∼2.5 keV seems possible, which represents the principle limit for the discrimination of these two species in liquid argon.

The liquid-argon scintillation pulseshape in DEAP-3600

“…This work corroborates the model from [19], which attributes the intermediate component to a feature intrinsic to LAr, and confirms the existing evidence for delayed TPB emission. Both are measured for the first time here in a large LAr-based particle detector.…”

“…Some authors attributed this component to late emission of the wavelength shifter 1,1,4,4tetraphenyl-1,3-butadiene (TPB) [20], making it an instrumental effect. However, the intermediate component was also observed in [19], where the pulseshape was measured without the use of a wavelengh-shifter. This supports the hypothesis that the intermediate component is a feature intrinsic to LAr scintillation physics.…”

“…The LAr pulseshape is well-known to have a doubleexponential time structure originating from a short-lived singlet and a long-lived triplet state [13][14][15]. In addition, an intermediate component, which affects the pulseshape between approximately 30 ns to 100 ns, is commonly observed [12,[16][17][18][19]. Some authors attributed this component to late emission of the wavelength shifter 1,1,4,4tetraphenyl-1,3-butadiene (TPB) [20], making it an instrumental effect.…”

Intense vacuum ultraviolet and infrared scintillation of liquid Ar-Xe mixtures

“…In summary, it has been found that the efficient energy transfer from argon to xenon which is well known from the gas phase is also present in the liquid phase. This had already been observed in the context of recording emission spectra from nominally pure liquid argon [13,18,23] and Fig. 7.…”

Intense infrared scintillation of liquid Ar-Xe mixtures

“…The emission was found in the context of a series of experiments on the emission and absorption features of liquid noble gases [1,3,4,5]. This study was motivated by the fact that liquid rare gases are presently often used in large quantities as the detector material in rare event physics, e.g., the search for the neutrinoless double-beta decay (GERDA Phase II uses a liquid argon veto [6], EXO uses liquid xenon [7]) and the direct dark matter search (Liquid argon: WArP [8], ArDM [9,10], DarkSide [11]; Liq-arXiv:1511.07722v1 [physics.ins-det] 24 Nov 2015 uid xenon: XENON100 [12], LUX [13]).…”