219 research outputs found
Extracting constraints from direct detection searches of supersymmetric dark matter in the light of null results from the LHC in the squark sector
The comparison of the results of direct detection of Dark Matter, obtained
with various target nuclei, requires model-dependent, or even arbitrary,
assumptions. Indeed, to draw conclusions either the spin-dependent (SD) or the
spin-independent (SI) interaction has to be neglected. In the light of the null
results from supersymmetry searches at the LHC, the squark sector is pushed to
high masses. We show that for a squark sector at the TeV scale, the framework
used to extract contraints from direct detection searches can be redefined as
the number of free parameters is reduced. Moreover, the correlation observed
between SI and SD proton cross sections constitutes a key issue for the
development of the next generation of Dark Matter detectors.Comment: Figure 3 has been updated. Conclusions unchange
Direct comparison of high voltage breakdown measurements in liquid argon and liquid xenon
As noble liquid time projection chambers grow in size their high voltage requirements increase, and detailed, reproducible studies of dielectric breakdown and the onset of electroluminescence are needed to inform their design. The Xenon Breakdown Apparatus (XeBrA) is a 5-liter cryogenic chamber built to characterize the DC high voltage breakdown behavior of liquid xenon and liquid argon. Electrodes with areas up to 33 cm2 were tested while varying the cathode-anode separation from 1 to 6 mm with a voltage difference up to 75 kV. A power-law relationship between breakdown field and electrode area was observed. The breakdown behavior of liquid argon and liquid xenon within the same experimental apparatus was comparable
In situ measurement of the electron drift velocity for upcoming directional Dark Matter detectors
Three-dimensional track reconstruction is a key issue for directional Dark
Matter detection and it requires a precise knowledge of the electron drift
velocity. Magboltz simulations are known to give a good evaluation of this
parameter. However, large TPC operated underground on long time scale may be
characterized by an effective electron drift velocity that may differ from the
value evaluated by simulation. In situ measurement of this key parameter is
hence needed as it is a way to avoid bias in the 3D track reconstruction. We
present a dedicated method for the measurement of the electron drift velocity
with the MIMAC detector. It is tested on two gas mixtures: CF4 and CF4 + CHF3.
The latter has been chosen for the MIMAC detector as we expect that adding CHF3
to pure CF4 will lower the electron drift velocity. This is a key point for
directional Dark Matter as the track sampling along the drift field will be
improved while keeping almost the same Fluorine content of the gas mixture. We
show that the drift velocity at 50 mbar is reduced by a factor of about 5 when
adding 30% of CHF3.Comment: 19 pages, 14 figures. Minor corrections, matches published version in
JINS
Measurement of the electron drift velocity for directional dark matter detectors
Three-dimensional track reconstruction is a key issue for directional Dark
Matter detection. It requires a precise knowledge of the electron drift
velocity. Magboltz simulations are known to give a good evaluation of this
parameter. However, large TPC operated underground on long time scale may be
characterized by an effective electron drift velocity that may differ from the
value evaluated by simulation. In situ measurement of this key parameter is
hence a way to avoid bias in the 3D track reconstruction. We present a
dedicated method for the measurement of the electron drift velocity with the
MIMAC detector. It is tested on two gas mixtures : and . We also show that adding allows us to lower the
electron drift velocity while keeping almost the same Fluorine content of the
gas mixture.Comment: Proceedings of the 4th international conference on Directional
Detection of Dark Matter (CYGNUS 2013), 10-12 June 2013, Toyama, Japa
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Analysis of 83mKr prompt scintillation signals in the PIXeY detector
Prompt scintillation signals from 83mKr calibration sources are a useful metric to calibrate the spatial variation of light collection efficiency and electric field magnitude of a two phase liquid-gas xenon time projection chamber. Because 83mKr decays in two steps, there are two prompt scintillation pulses for each calibration event, denoted S1a and S1b. We study the ratio of S1b to S1a signal sizes in the Particle Identification in Xenon at Yale (PIXeY) experiment and its dependence on the time separation between the two signals (Δ t), notably its increase at low Δ t. In PIXeY data, the Δ t dependence of S1b/S1a is observed to exhibit two exponential components: one with a time constant of 0.05 ± 0.02 μ s, which can be attributed to processing effects and pulse overlap and one with a time constant of 10.2 ± 2.2 μs that increases in amplitude with electric drift field, the origin of which is not yet understood
MIMAC: MIcro-tpc MAtrix of Chambers for dark matter directional detection
Directional detection of non-baryonic Dark Matter is a promising search
strategy for discriminating WIMP events from neutrons, the ultimate background
for dark matter direct detection. This strategy requires both a precise
measurement of the energy down to a few keV and 3D reconstruction of tracks
down to a few mm. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has
developed in the last years an original prototype detector based on the direct
coupling of large pixelized micromegas with a special developed fast
self-triggered electronics showing the feasibility of a new generation of
directional detectors. The first bi-chamber prototype has been installed at
Modane, underground laboratory in June 2012. The first undergournd background
events, the gain stability and calibration are shown. The first spectrum of
nuclear recoils showing 3D tracks coming from the radon progeny is presented.Comment: Proceedings of the 4th International Conference on Directional Dark
Matter Detection CYGNUS2013, held in Toyoma (Japan), June 201
Observation of activity prior to dielectric breakdown in liquid xenon with the XeBrA experiment
Maintaining the electric fields necessary for the current generation of noble
liquid time projection chambers (TPCs), with drift lengths exceeding one meter,
requires a large negative voltage applied to their cathode. Delivering such
high voltage is associated with an elevated risk of electrostatic discharge and
electroluminescence, which would be detrimental to the performance of the TPC.
The Xenon Breakdown Apparatus (XeBrA) is a five-liter high-voltage test chamber
built to investigate the factors contributing to high voltage breakdown in
noble liquids. Area scaling and surface finish were observed to be the dominant
factors affecting breakdown. In addition, small electrical activity was
frequently observed during high voltage ramps prior to electrostatic discharge.
The position of breakdowns was reconstructed with a system of high-speed
cameras and good agreement with electric field simulations was found. Based on
the results presented in this work, we recommend that the next generation of
TPCs should not withstand fields larger than 20 kV/cm on the electrode
surfaces.Comment: 29 pages, 13 figures; typo in the author list correcte
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