Liquid Xenon Scintillation Research Articles

Correlated fluctuations between luminescence and ionization in liquid xenon

The ionization of liquefied noble gases by radiation is known to be accompanied by fluctuations much larger than predicted by Poisson statistics. We have studied the fluctuations of both scintillation and ionization in liquid xenon and have measured, for the first time, a strong anti-correlation between the two at a microscopic level, with coefficient -0.80 < {rho}{sub ep} < -0.60. This provides direct experimental evidence that electron-ion recombination is partially responsible for the anomalously large fluctuations and at the same time allows substantial improvement of calorimetric energy resolution.

Development of a liquid xenon scintillation detector for a new experiment to search for μ→eγ decays

A novel gamma-ray detector based on a liquid xenon scintillator is under development for a new experiment to search for the lepton flavor violating process μ+→e+γ at the Paul Scherrer Institute (PSI). The experiment is designed to have a sensitivity down to 10−14 branching ratio. We constructed a prototype detector with an active volume of 69l to demonstrate the performance of the proposed detector for high-energy gamma rays of around 50MeV. After a test of the cryogenic system for the prototype detector, we have begun studies with the prototype using a gamma-beam up to 40MeV from the laser Compton backscattering facility at the TERAS electron storage ring of the National Institute of Advanced Industrial Science and Technology (AIST).

The liquid xenon set-up of the DAMA experiment

The main features of the low background DAMA pure liquid xenon scintillator set-up running deep underground in the Gran Sasso National Laboratory of the INFN are described.

Detection of scintillation light of liquid xenon with a LAAPD

First observation of liquid xenon scintillation due to α-particles and γ-rays with a large area avalanche photodiode immersed in the liquid is reported. An energy resolution of 10% (FWHM) and a coincidence time resolution of <1 ns (FWHM) were measured with 5.5 MeV α-particles and 511 keV γ-rays, respectively. The quantum efficiency of the photodiode for xenon scintillation light ( λ=178 nm) is estimated to be ∼100%.

Measurements of scintillation efficiency and pulse shape for low energy recoils in liquid xenon

Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is 0.22 +/- 0.01 in the recoil energy range 40 keV - 70 keV. Under the assumption of a single dominant decay component to the scintillation pulse-shape the log-normal mean parameter T0 of the maximum likelihood estimator of the decay time constant for 6 keV < Eee < 30 keV nuclear recoil events is equal to 21.0 ns +/- 0.5 ns. It is observed that for electron recoils T0 rises slowly with energy, having a value ~ 30 ns at Eee ~ 15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse-shape.

Light response of a pure liquid Xenon scintillator irradiated with 2.5 MeV neutrons

In this paper the results obtained by exposing a pure liquid Xenon scintillator to 2.5 MeV neutrons are presented. In particular, the ratio of the measured amount of light from a recoil nucleus to the amount of light from an electron of the same kinetic energy has been investigated. Results substantially in agreement with previous determinations are obtained. A figure of r = 0.46 ± 0.10 is cumulatively obtained.

Time and Energy Responses of Liquid-Xenon Scintillation Chamber for 20Ne Ion Beam at 135A MeV

The time and energy responses of a liquid-xenon (LXe) scintillation chamber to heavy-ion beams were studied using 20Ne ions at an energy of 135A MeV. The scintillation light in LXe was observed by two photomultipliers (PMTs). The intrinsic time resolution by one PMT was confirmed to be approximately 30 ps in sigma up to a beam intensity of 1.3 ×105 counts per second (cps). The energy output was observed to be also constant for the increase in the beam intensity. The energy resolution was 1.2–1.4% in sigma. The possibilities of LXe as a detector medium for an energy spectrometer and a timing detector for heavy-ion beams were described.

Search for the nucleon and di-nucleon decay into invisible channels

Data collected deep underground at the Gran Sasso National Laboratory of INFN by using the ≃ 6.5 kg DAMA liquid Xenon scintillator have been analysed to search for nucleon and di-nucleon decays into invisible channels (decay to ν i ν i or to ν i ν iν i or to 5ν i , etc., with i=e,μ,τ) or disappearance. The considered statistics has been 2257.7 kg ×day. The new obtained limits are: τ p=1.9×10 24 yr, τ nn=1.2×10 25 yr and τ pp=5.5×10 23 yr at 90% C.L. The latter values are the same or better than those previously established by the Fréjus Collaboration; in particular, the limits for the NN decay into ν τ ν τ are set for the first time.

Study of large area avalanche photodiode for detecting liquid xenon scintillation

A large area avalanche photodiode (LAAPD) has been investigated as a possible photosensor for detecting liquid xenon scintillation. The LAAPD proved to be operational at the temperature of liquid xenon (down to -105/spl deg/C) with the dark current significantly reduced with respect to that at room temperature (less than 1 pA versus 30 nA at 20/spl deg/C). The bias voltage needed to achieve a certain gain is found to decrease linearly with decreasing temperature at a rate of 2.3 V//spl deg/C.

New limits on particle dark matter search with a liquid Xenon target-scintillator

New results on WIMP- 129Xe elastic scattering are presented. The target-detector is a pure liquid Xenon scintillator filled with Kr-free Xenon enriched in 129Xe at 99.5%. Preliminary measurements with neutrons to estimate the quenching factor and to study a statistical pulse shape discrimination between electromagnetic background and recoils are also discussed.

A New Liquid Xenon Scintillation Detector to Detect and Study Low Energy Signals from WIMPs

A New Liquid Xenon Scintillation Detector to Detect and Study Low Energy Signals from WIMPs

Low temperature performance of photomultiplier tubes illuminated in pulsed mode by visible and vacuum ultraviolet light

Detecting the ultraviolet scintillation light of the liquefied rare gases, in particular liquid xenon, requires the use of photomultiplier tubes (PMTs) in a temperature range where their operation is not ensured by manufacturers. Simultaneously, monitoring of the PMTs should be done in the visible for technical reasons. Bialkali photocathodes, that present high quantum efficiency and low dark noise, exhibit a very strong increase of electrical resistivity upon cooling that, apart from other reasons, can lead to operation failure at low temperature. Photomultiplier tubes with bialkali photocathodes and quartz windows (two EMI 9750Q and one Philips XP 2020Q) and another with S11-type photocathode and glass window (FEU 85A) were tested down to −160 °C with a pulsed light source, both in the visible region and at the xenon scintillation wavelength in the vacuum ultraviolet. For the visible range, the results obtained with bialkali photomultipliers display a sharp drop of response at about −100 °C, depending on the count rate, regardless of the wavelength, and a shift of the spectral sensitivity curve towards shorter wavelengths. Concerning the vacuum ultraviolet region, a significant increase of the response was observed between room temperature and that of the efficiency drop. For some photomultiplier tubes, the response as a function of temperature was observed to depend on their past history, probably due to mechanical effects arising in the multiplier system upon cooling. It is concluded that photomultipliers with bialkali photocathode can, in principle, be used for the detection of liquid xenon scintillation, although they have to be carefully monitored while in operation.

Direct detection of WIMP dark matter—techniques above 100K

Searches for rare nuclear recoil events, from interactions with hypothetical weakly interacting dark matter particles, require novel methods of distinguishing nuclear recoils from the much larger gamma and beta background. This review covers detectors which operate at temperatures above 100K. New limits have now been set by pulse shape analysis in NaI targets at 300K, and much improved discrimination may be possible at 100–160K. Achievement of sensitivity to neutralino event rates would be possible using combined scintillation and ionisation processes in liquid xenon (160K). Studies of future directional detectors are also in progress, based on either range effects in solids or tracks in low pressure gases. A comparison is made of potential sensitivities of these techniques, together with a discussion of neutron background reduction.

Charge conservation and electron lifetime: Limits from a liquid xenon scintillator

New limits on the mean lifetime of the electron for decay into non-ionizing particles have been achieved by using a low activity liquid xenon scintillator at the Gran Sasso National Laboratory.

Limits on WIMP- 129Xe inelastic scattering

Limits on WIMP- 129Xe nucleus inelastic scattering have been achieved by using a low activity liquid xenon scintillator at the Gran Sasso National Laboratory. Signigicant improvements have been reached.

Search for WIMPs with enriched xenon at Gran Sasso

A low-activity liquid-xenon scintillator is running at the Gran Sasso National Laboratory of INFN using liquid Kr-free xenon enriched at 99.5% in129Xe. The result of adark matter direct search—looking also for the annual modulation effect—is presented. Preliminary exclusion plots both for coherent and spin-dependent coupled WIMPs are evaluated.

Reply to ‘Comments on “Liquid xenon ionization and scintillation studies for a totally active-vector electromagnetic calorimeter”’

The recent publication of Miyajima et al. [Nucl. Instr. and Meth. A 352 (1995) 548] strongly criticized a paper [Nucl. Instr. and Meth. A 323 (1992) 583] which we published several years ago on measurements of W and W s, the energy needed to create an electron or photon by ionization or scintillation, respectively, in liquid Xenon (LXe). Their criticism is based on a false reading of the contents of our paper and consequently is basically incorrect.

Liquid xenon scintillation: photon yield and Fano factor measurements

This paper presents a new measurement of the photon yield and the first measurement of the Fano factor in liquid xenon with a photomultiplier as photodetector. The observed photoelectron yield is 3.2/MeV which, after correction for detector solid angle and efficiency, corresponds to 78 600 photons/MeV. The Fano factor observed, F s = 0.033 ± 0.045, agrees with the value measured in the gaseous state by other authors.

Detection of energy deposition down to the keV region using liquid xenon scintillation

A possible method for WIMPs detection using liquid xenon scintillation is discussed [1]. Background from cosmic and radioactive gamma rays at energies down to the keV region can be easily rejected by requiring the presence of proportional scintillation. The results from a basic test are presented and a prototype detector design is proposed.

A new liquid xenon scintillation detector for positron emission tomography

A new position-sensitive detector of annihilation photons filled with liquid xenon is proposed for positron emission topography. Simultaneous detection of both liquid xenon scintillation and ionization current produces a time resolution of <1 ns and a position ressolution in the tangential direction of the tomograph ring is ∼1mm and in the radial direction is ∼5mm. The advantages of tomograph with new detectors are discussed. New algorithms of Compton scattering can be used.