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Attenuation measurements of vacuum ultraviolet light in liquid argon revisited  [PDF]
A. Neumeier,T. Dandl,A. Himpsl,M. Hofmann,L. Oberauer,W. Potzel,S. Sch?nert,A. Ulrich
Physics , 2015, DOI: 10.1016/j.nima.2015.07.051
Abstract: The attenuation of vacuum ultraviolet light in liquid argon in the context of its application in large liquid noble gas detectors has been studied. Compared to a previous publication several technical issues concerning transmission measurements in general are addressed and several systematic effects were quantitatively measured. Wavelength-resolved transmission measurements have been performed from the vacuum ultraviolet to the near-infrared region. On the current level of sensitivity with a length of the optical path of 11.6 cm, no xenon-related absorption effects could be observed, and pure liquid argon is fully transparent down to the short wavelength cut-off of the experimental setup at 118 nm. A lower limit for the attenuation length of pure liquid argon for its own scintillation light has been estimated to be 1.10 m based on a very conservative approach.
Attenuation of vacuum ultraviolet light in liquid argon  [PDF]
A. Neumeier,M. Hofmann,L. Oberauer,W. Potzel,S. Sch?nert,T. Dandl,T. Heindl,A. Ulrich,J. Wieser
Physics , 2015, DOI: 10.1140/epjc/s10052-012-2190-z
Abstract: The transmission of liquid argon has been measured, wavelength resolved, for a wavelength interval from 118 to 250 nm. The wavelength dependent attenuation length is presented for pure argon. It is shown that no universal wavelength independent attenuation length can be assigned to liquid argon for its own fluorescence light due to the interplay between the wavelength dependent emission and absorption. A decreasing transmission is observed below 130 nm in both chemically cleaned and distilled liquid argon and assigned to absorption by the analogue of the first argon excimer continuum. For not perfectly cleaned argon a strong influence of impurities on the transmission is observed. Two strong absorption bands at 126.5 and 141.0 nm with approximately 2 and 4 nm width, respectively, are assigned to traces of xenon in argon. A broad absorption region below 180 nm is found for unpurified argon and tentatively attributed to the presence of water in the argon sample.
Phase separation in mixed argon-xenon clusters  [PDF]
O. G. Danylchenko,Yu. S. Doronin,S. I. Kovalenko,V. N. Samovarov
Physics , 2006,
Abstract: In this paper, electron diffraction and optical methods are used together for the first time to study the problem of phase equilibrium in binary clusters of heavy rare gases. For the argon-xenon system, a new effect of its decay into pure components with a sharp interface between the xenon core and the argon shell is observed.
Exciton-impurity luminescence from noncrystalline xenon-argon clusters  [PDF]
O. G. Danylchenko,Yu. S. Doronin,S. I. Kovalenko,M. Yu. Libin,V. N. Samovarov,V. L. Vakula
Physics , 2009,
Abstract: For the first time in binary mixtures of solid rare gases exciton-impurity luminescence is observed from a xenon-argon system containing argon as impurity. An exciton-impurity emission band is registered for binary clusters with the structure of multilayer icosahedron. The optical transition occurs from an energy level lying very close to the lowest level of volume excitons in bulk xenon samples. The results demonstrate the possibility of probing excitonic levels in noncrystalline condensed media.
Measurement of the refractive index and attenuation length of liquid xenon for its scintillation light  [PDF]
V. N. Solovov,V. Chepel,M. I. Lopes,A. Hitachi,R. Ferreira Marques,A. J. P. L. Policarpo
Physics , 2003, DOI: 10.1016/j.nima.2003.08.117
Abstract: The attenuation length and refractive index of liquid xenon for intrinsic scintillation light (178nm) have been measured in a single experiment. The value obtained for attenuation length is 364 +- 18 mm. The refractive index is found to be 1.69 +- 0.02. Both values were measured at a temperature of 170 +- 1 K.
Wiedemann-Franz ratio in plasmas in the mixtures of xenon, argon and cesium  [PDF]
Novakovi? Nade?da V.,Stojilkovi? S.M.,Gaji? Dragan ?.
Facta Universitatis Series : Physics, Chemistry and Technology , 2004, DOI: 10.2298/fupct0401001n
Abstract: In the present paper, the xenon plasmas containing argon and cesium as additive and pertaining to the above mentioned type (high-pressure low-temperature, LIE) are studied, and a theoretical evaluation of their basic transport parameters is presented. The numerical calculations were based on the assumption that the system is kept under constant pressure and temperature and that it attained local thermo dynamical equilibrium. Some results of a theoretical study which embraced numerical evaluations of the plasma composition, electron collision frequency, electrical and thermal conductivities and Wiedemann-Franz ratio, all regarded as functions of pressure and temperature, are given for high-pressure (from 0,1 MPa to 1,5 MPa) and low-temperature (from 2 000 K to 20 000 K). A previously derived modified expression for the Debye radius, offering the possibility to treat the plasmas considered as weakly non-ideal in the whole temperature range of interest, is used in the evaluations, in combination with the Saha equations for the relevant ionization stages of xenon, argon and cesium. .
Index of refraction, Rayleigh scattering length, and Sellmeier coefficients in solid and liquid argon and xenon  [PDF]
Emily Grace,James A. Nikkel
Physics , 2015,
Abstract: Like all the noble elements, argon and xenon are scintillators, \emph{i.e.} they produce light when exposed to radiation. Large liquid argon detectors have become widely used in low background experiments, including dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation wavelength has not been measured and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value and find agreement within the uncertainties. This method results in a Rayleigh scattering length for liquid argon at the triple point of 55 $\pm$ 5 cm, a Rayleigh scattering length of 40 $\pm$ 4 cm for solid argon at the triple point, and a Rayleigh scattering length of 14 $\pm$ 1 cm for solid xenon at the triple point.
The Ultraviolet Attenuation Law in Backlit Spiral Galaxies  [PDF]
William C. Keel,Anna M. Manning,Benne W. Holwerda,Chris J. Lintott,Kevin Schawinski
Physics , 2014, DOI: 10.1088/0004-6256/147/2/44
Abstract: (Abridged) The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use GALEX, XMM Optical Monitor, and HST data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with candidates provided by Galaxy Zoo participants. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law close to the Calzetti et al. (1994) form; the UV slope for the overall sample is substantially shallower than found by Wild et al. (2011), a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. This "grey" law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. The extrapolation needed to compare attenution between backlit galaxies at moderate redshifts, and local systems from SDSS data, is mild enough to allow use of galaxy overlaps to trace the cosmic history of dust. For NGC 2207, the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the ultraviolet, which opens the possibility that widespread diffuse dust dominates over dust in star-forming regions deep into the ultraviolet. Comparison with published radiative-transfer models indicates that the role of dust clumping dominates over differences in grain populations, at this spatial resolution.
Pulse-shape discrimination and energy resolution of a liquid-argon scintillator with xenon doping  [PDF]
Christopher G. Wahl,Ethan P. Bernard,W. Hugh Lippincott,James A. Nikkel,Yunchang Shin,Daniel N. McKinsey
Physics , 2014, DOI: 10.1088/1748-0221/9/06/P06013
Abstract: Liquid-argon scintillation detectors are used in fundamental physics experiments and are being considered for security applications. Previous studies have suggested that the addition of small amounts of xenon dopant improves performance in light or signal yield, energy resolution, and particle discrimination. In this study, we investigate the detector response for xenon dopant concentrations from 9 +/- 5 ppm to 1100 +/- 500 ppm xenon (by weight) in 6 steps. The 3.14-liter detector uses tetraphenyl butadiene (TPB) wavelength shifter with dual photomultiplier tubes and is operated in single-phase mode. Gamma-ray-interaction signal yield of 4.0 +/- 0.1 photoelectrons/keV improved to 5.0 +/- 0.1 photoelectrons/keV with dopant. Energy resolution at 662 keV improved from (4.4 +/- 0.2)% ({\sigma}) to (3.5 +/- 0.2)% ({\sigma}) with dopant. Pulse-shape discrimination performance degraded greatly at the first addition of dopant, slightly improved with additional additions, then rapidly improved near the end of our dopant range, with performance becoming slightly better than pure argon at the highest tested dopant concentration. Some evidence of reduced neutron scintillation efficiency with increasing dopant concentration was observed. Finally, the waveform shape outside the TPB region is discussed, suggesting that the contribution to the waveform from xenon-produced light is primarily in the last portion of the slow component.
Intense Vacuum-Ultraviolet and Infrared Scintillation of Liquid Ar-Xe Mixtures  [PDF]
A. Neumeier,T. Dandl,T. Heindl,A. Himpsl,L. Oberauer,W. Potzel,S. Roth,S. Sch?nert,J. Wieser,A. Ulrich
Physics , 2015, DOI: 10.1209/0295-5075/109/12001
Abstract: Vacuum ultraviolet light emission from xenon-doped liquid argon is described in the context of liquid noble gas particle detectors. Xenon concentrations in liquid argon from 0.1 ppm to 1000 ppm were studied. The energy transfer from the second excimer continuum of argon ($\sim$127 nm) to the second excimer continuum of xenon ($\sim$174 nm) is observed by recording optical emission spectra. The transfer almost saturates at a xenon concentration of $\sim$10 ppm for which, in addition, an intense emission in the infrared at a peak wavelength of 1.17 $\mu$m with (13000$\pm$4000) photons per MeV deposited by electrons had been found. The corresponding value for the VUV emission at a peak wavelength of 174 nm (second excimer continuum of xenon) is determined to be (20000$\pm$6000) photons per MeV electron energy deposited. Under these excitation conditions pure liquid argon emits (22000$\pm$3000) photons per MeV electron energy deposited at a peak wavelength of 127nm. An electron-beam induced emission spectrum for the 10 ppm Ar-Xe liquid mixture ranging from 115 nm to 3.5 $\mu$m is presented. VUV emission spectra from xenon-doped liquid argon with exponentially varied xenon concentrations from 0.1 ppm to 1000 ppm are also shown. Time structure measurements of the light emissions at well-defined wavelength positions in the vacuum ultraviolet as well as in the near-infrared are presented.
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