1,214 research outputs found
Detection of the primary scintillation light from dense Ar, Kr and Xe with novel photosensitive gaseous detectors
The detection of primary scintillation light in combination with the charge
or secondary scintillation signals is an efficient technique to determine the
events t=0 as well as particle / photon separation in large mass TPC detectors
filled with noble gases and/or condensed noble gases. The aim of this work is
to demonstrate that costly photo-multipliers could be replaced by cheap novel
photosensitive gaseous detectors: wire counters, GEMs or glass capillary tubes
coupled with CsI photocathodes. We have performed systematic measurements with
Ar, Kr and Xe gas at pressures in the range of 1-50 atm as well as some
preliminary measurements with liquid Xe and liquid Ar. With the gaseous
detectors we succeeded in detecting scintillation light produced by 22 keV
X-rays with an efficiency of close to 100%. We also detected the scintillation
light produced by bs (5 keV deposit energy) with an efficiency close to 25%.
Successful detection of scintillation from 22 keV gammas open new experimental
possibilities not only for nTOF and ICARUS experiments, but also in others,
like WIMPs search through nuclear recoil emission
The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures
We have demonstrated that hole-type gaseous detectors, GEMs and capillary
plates, can operate up to 77 K. For example, a single capillary plate can
operate at gains of above 10E3 in the entire temperature interval between 300
until 77 K. The same capillary plate combined with CsI photocathodes could
operate perfectly well at gains (depending on gas mixtures) of 100-1000.
Obtained results may open new fields of applications for capillary plates as
detectors of UV light and charge particles at cryogenic temperatures: noble
liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic
PETs.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, 200
Measurement of Atmospheric Neutrino Oscillations with a High-Density Detector
We propose an experiment to test the hypothesis that the reported anomaly on
atmospheric neutrino fluxes is due to nu_mu nu_x oscillations. It will rely
both on a disappearance technique, exploiting the method of the dependence of
the event rate on L/E, which was recently shown to be effective for detection
of neutrino oscillation and measurement of the oscillation parameters, and on
an appearance technique, looking for an excess of muon-less events at high
energy produced by upward-going tau neutrinos. The detector will consist of
iron planes interleaved by limited streamer tubes. The total mass will be about
30 kt. The possibility of recuperating most of the instrumentation from
existing detectors allows to avoid R&D phases and to reduce construction time.
In four years of data taking, this experiment will be sensitive to oscillations
nu_mu nu_x with Delta m^2 > 10^-4 eV^2 and a mixing near to maximal, and
answer the question whether nu_x is a sterile or a tau neutrino
Observation of inertial energy cascade in interplanetary space plasma
We show in this article direct evidence for the presence of an inertial
energy cascade, the most characteristic signature of hydromagnetic turbulence
(MHD), in the solar wind as observed by the Ulysses spacecraft. After a brief
rederivation of the equivalent of Yaglom's law for MHD turbulence, we show that
a linear relation is indeed observed for the scaling of mixed third order
structure functions involving Els\"asser variables. This experimental result,
confirming the prescription stemming from a theorem for MHD turbulence, firmly
establishes the turbulent character of low-frequency velocity and magnetic
field fluctuations in the solar wind plasma
The development of gaseous detectors with solid photocathodes for low temperature
There are several applications and fundamental research areas which require
the detection of VUV light at cryogenic temperatures. For these applications we
have developed and successfully tested special designs of gaseous detectors
with solid photocathodes able to operate at low temperatures: sealed gaseous
detectors with MgF2 windows and windowless detectors. We have experimentally
demonstrated, that both primary and secondary (due to the avalanche
multiplication inside liquids) scintillation lights could be recorded by
photosensitive gaseous detectors. The results of this work may allow one to
significantly improve the operation of some noble liquid gas TPCs.Comment: Presented at the X Vienna Conference on Instumentation, Vienna,
February 200
Anti-Insulin Receptor Autoantibodies Are Not Required for Type 2 Diabetes Pathogenesis in NZL/Lt Mice, a New Zealand Obese (NZO)-Derived Mouse Strain
The New Zealand obese (NZO) mouse strain shares with
the related New Zealand black (NZB) strain a number of
immunophenotypic traits. Among these is a high proportion
of B-1 B lymphocytes, a subset associated with autoantibody
production. Approximately 50% of NZO/HlLt
males develop a chronic insulin-resistant type 2 diabetes
syndrome associated with 2 unusual features: the presence
of B lymphocyteâenriched peri-insular infiltrates and
the development of anti-insulin receptor autoantibodies
(AIRAs). To establish the potential pathogenic contributions
ofBlymphocytes and AIRAs in this model, a disrupted immunoglobulin heavy chain gene (Igh-6) congenic on the
NZB/BlJ background was backcrossed 4 generations into
the NZO/HlLt background and was then intercrossed to
produce mice that initially segregated for wild-type versus
the mutant Igh-6 allele and thus permitted comparison
of syndrome development. A new flow cytometric assay
(AIRA binding to transfected Chinese hamster ovary
cells stably expressing mouse insulin receptor) showed IgM
and IgG subclass AIRAs in serum from Igh-6 intact males,
but not in Igh6null male serum. However, the absence of
B lymphocytes and antibodies distinguishing mutant from
wild-type males failed to significantly affect diabetes-free
survival. The Igh6nullmales gained weight less rapidly than
wild-type males, probably accounting for a retardation, but
not prevention, of hyperglycemia. Thus, AIRA and the Blymphocyte
component of the peri-insulitis in chronic diabetics
were not essential either to development of insulin
resistance or to eventual pancreatic beta cell failure and
loss. A new substrain, designated NZL, was generated by
inbreeding Igh-6 wild-type segregants. Currently at the F10
generation, NZL mice exhibit the same juvenile-onset obesity
as NZO/HlLt males, but develop type 2 diabetes at a
higher frequency (> 80%). Also, unlike NZO/HlLt mice that
are difficult to breed, the NZL/Lt strain breeds well and thus
offers clear advantages to obesity/diabetes researchers
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