108 research outputs found
Performance and Fundamental Processes at Low Energy in a Two-Phase Liquid Xenon Dark Matter Detector
We extend the study of the performance of a prototype two-phase liquid xenon
WIMP dark matter detector to recoil energies below 20 keV. We demonstrate a new
method for obtaining the best estimate of the energies of events using a
calibrated sum of charge and light signals and introduce the corresponding
discrimination parameter, giving its mean value at 4 kV/cm for electron and
nuclear recoils up to 300 and 100 keV, respectively. We show that fluctuations
in recombination limit discrimination for most energies, and reveal an
improvement in discrimination below 20 keV due to a surprising increase in
ionization yield for low energy electron recoils. This improvement is crucial
for a high-sensitivity dark matter search.Comment: 4 pages, 6 figures, submitted to DM06 conference proceedings in Nucl
Phys
Detection of Scintillation Light of Liquid Xenon with a LAAPD
First observation of liquid xenon scintillation due to alpha-particles and
gamma-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 less then 1 ns (FWHM) were measured with 5.5 MeV alpha-particles and 511 keV
gamma-rays, respectively. The quantum efficiency of the photodiode for xenon
scintillation light (wavelength 178 nm) is estimated to be ~100%.Comment: 11 pages, 9 figures, to be published in Nuclear Instruments and
Method
Measurement of single electron emission in two-phase xenon
We present the first measurements of the electroluminescence response to the
emission of single electrons in a two-phase noble gas detector. Single
ionization electrons generated in liquid xenon are detected in a thin gas layer
during the 31-day background run of the ZEPLIN-II experiment, a two-phase xenon
detector for WIMP dark matter searches. Both the pressure dependence and
magnitude of the single-electron response are in agreement with previous
measurements of electroluminescence yield in xenon. We discuss different
photoionization processes as possible cause for the sample of single electrons
studied in this work. This observation may have implications for the design and
operation of future large-scale two-phase systems.Comment: 11 pages, 6 figure
Scintillation efficiency of liquid xenon for nuclear recoils with the energy down to 5 keV
The scintillation efficiency of liquid xenon for nuclear recoils has been
measured to be nearly constant in the recoil energy range from 140 keV down to
5 keV. The average ratio of the efficiency for recoils to that for gamma-rays
is found to be 0.19+-0.02.Comment: 13 pages, 5 figure
The scintillation and ionization yield of liquid xenon for nuclear recoils
XENON10 is an experiment designed to directly detect particle dark matter. It
is a dual phase (liquid/gas) xenon time-projection chamber with 3D position
imaging. Particle interactions generate a primary scintillation signal (S1) and
ionization signal (S2), which are both functions of the deposited recoil energy
and the incident particle type. We present a new precision measurement of the
relative scintillation yield \leff and the absolute ionization yield Q_y, for
nuclear recoils in xenon. A dark matter particle is expected to deposit energy
by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for
establishing the energy threshold of the experiment; this in turn determines
the sensitivity to particle dark matter. Our \leff measurement is in agreement
with recent theoretical predictions above 15 keV nuclear recoil energy, and the
energy threshold of the measurement is 4 keV. A knowledge of the ionization
yield \Qy is necessary to establish the trigger threshold of the experiment.
The ionization yield \Qy is measured in two ways, both in agreement with
previous measurements and with a factor of 10 lower energy threshold.Comment: 8 pages, 9 figures. To be published in Nucl. Instrum. Methods
Babinet's principle in the Fresnel regime studied using ultrasound
The diffraction of ultrasound by a circular disk and an aperture of the same
size have been investigated as a demonstration of Babinet's principle in the
Fresnel regime. The amplitude and the phase of diffracted ultrasonic waves have
been measured, and a graphical treatment of the results is performed by simply
drawing vectors (phasors) in the complex plane. The results verify Babinet's
principle. It is also found that the incident wave is indeed 90 deg behind the
phase of the wave passing through on the central axis of a circular aperture.
This paradox has previously been regarded as a defect of Fresnel's theory. The
apparatus used is intended as a table-top instrument for the student laboratory
in general science and engineering classes.Comment: Am. J. Phys. in internal rev. process, 19 pages with 7 figs., v2:
change in presentatio
A Study of the Scintillation Induced by Alpha Particles and Gamma Rays in Liquid Xenon in an Electric Field
Scintillation produced in liquid xenon by alpha particles and gamma rays has
been studied as a function of applied electric field. For back scattered gamma
rays with energy of about 200 keV, the number of scintillation photons was
found to decrease by 64+/-2% with increasing field strength. Consequently, the
pulse shape discrimination power between alpha particles and gamma rays is
found to reduce with increasing field, but remaining non-zero at higher fields.Comment: 15 pages, 12 figures, accepted by Nuclear Instruments and Methods in
Physics Research
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