5,715 research outputs found
GADZOOKS! Antineutrino Spectroscopy with Large Water Cerenkov Detectors
We propose modifying large water \v{C}erenkov detectors by the addition of
0.2% gadolinium trichloride, which is highly soluble, newly inexpensive, and
transparent in solution. Since Gd has an enormous cross section for radiative
neutron capture, with MeV, this would make neutrons visible
for the first time in such detectors, allowing antineutrino tagging by the
coincidence detection reaction (similarly for
). Taking Super-Kamiokande as a working example, dramatic
consequences for reactor neutrino measurements, first observation of the
diffuse supernova neutrino background, Galactic supernova detection, and other
topics are discussed.Comment: 4 pages, 1 figure, submitted to Phys. Rev. Lett. Correspondence to
[email protected], [email protected]
Enhanced Transmission Through Disordered Potential Barrier
Effect of weak disorder on tunneling through a potential barrier is studied
analytically. A diagrammatic approach based on the specific behavior of
subbarrier wave functions is developed. The problem is shown to be equivalent
to that of tunneling through rectangular barriers with Gaussian distributed
heights. The distribution function for the transmission coefficient is
derived, and statistical moments \left are calculated. The
surprising result is that in average disorder increases both tunneling
conductance and resistance.Comment: 10 pages, REVTeX 3.0, 2 figures available upon reques
Crossover from hydrodynamic to acoustic drag on quartz tuning forks in normal and superfluid 4He
We present measurements of the drag forces on quartz tuning forks oscillating at low velocities in normal and superfluid 4He. We have investigated the dissipative drag over a wide range of frequencies, from 6.5 to 600 kHz, by using arrays of forks with varying prong lengths and by exciting the forks in their fundamental and first overtone modes. At low frequencies the behavior is dominated by laminar hydrodynamic drag, governed by the fluid viscosity. At higher frequencies acoustic drag is dominant and is described well by a three-dimensional model of sound emission
Nanoelectronic thermometers optimised for sub-10 millikelvin operation
We report the cooling of electrons in nanoelectronic Coulomb blockade
thermometers below 4 mK. Above 7 mK the devices are in good thermal contact
with the environment, well isolated from electrical noise, and not susceptible
to self-heating. This is attributed to an optimised design that incorporates
cooling fins with a high electron-phonon coupling and on-chip electronic
filters, combined with a low-noise electronic measurement setup. Below 7 mK the
electron temperature is seen to diverge from the ambient temperature. By
immersing a Coulomb Blockade Thermometer in the 3He/4He refrigerant of a
dilution refrigerator, we measure a lowest electron temperature of 3.7 mK.Comment: 11 pages, 4 figures. (Fixed fitted saturation T_e on p9
Radiation Testing of Electronics for the CMS Endcap Muon System
The electronics used in the data readout and triggering system for the
Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC)
particle accelerator at CERN are exposed to high radiation levels. This
radiation can cause permanent damage to the electronic circuitry, as well as
temporary effects such as data corruption induced by Single Event Upsets. Once
the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will
have five times higher instantaneous luminosity than LHC, allowing for
detection of rare physics processes, new particles and interactions. Tests have
been performed to determine the effects of radiation on the electronic
components to be used for the Endcap Muon electronics project currently being
designed for installation in the CMS experiment in 2013. During these tests the
digital components on the test boards were operating with active data readout
while being irradiated with 55 MeV protons. In reactor tests, components were
exposed to 30 years equivalent levels of neutron radiation expected at the
HL-LHC. The highest total ionizing dose (TID) for the muon system is expected
at the inner-most portion of the CMS detector, with 8900 rad over ten years.
Our results show that Commercial Off-The-Shelf (COTS) components selected for
the new electronics will operate reliably in the CMS radiation environment
Turbulent drag on a low-frequency vibrating grid in superfluid He-4 at very low temperatures
We present measurements of the dissipative turbulent drag on a vibrating grid in superfluid He-4 over a wide range of (low) frequencies. At high velocities, the dissipative drag is independent of frequency and is approximately the same as that measured in normal liquid He-4. We present measurements on a similar grid in superfluid He-3-B at low temperatures which shows an almost identical turbulent drag coefficient at low frequencies. However, the turbulent drag in He-3-B is substantially higher at higher frequencies. We also present measurements of the inertial drag coefficient for grid turbulence in He-4. The inertial drag coefficient is significantly reduced by turbulence in both superfluid and normal liquid He-4
Physiological Neuroprotective Mechanisms in Natural Genetic Systems: Therapeutic Clues for Hypoxia-Induced Brain Injuries
Clinical Neuroprotection Against Tissue Hypoxia During Brain Injuries; The Challenges and the Targets
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