2,668 research outputs found
Commissioning and Calibration of the ALICE TPC
ALICE (A Large Ion Collider Experiment) is the dedicated heavy ion experiment
at the Large Hadron Collider at CERN. The main tracking device of ALICE is a
large volume TPC.
The milestones of the TPC commissioning as well as the current status of the
detector calibration are presented. The obtained resolutions in transverse
momentum, position as well as in specific energy loss (dE/dx) are presented and
results from noise and electron drift velocity measurements are addressed.Comment: 4 pages, 4 figures- To appear in the conference proceedings for Quark
Matter 2009, March 30 - April 4, Knoxville, Tennesse
Measurements of ion mobility in argon and neon based gas mixtures
As gaseous detectors are operated at high rates of primary ionisation, ions
created in the detector have a considerable impact on the performance of the
detector. The upgraded ALICE Time Projection Chamber (TPC) will operate during
LHC Run with a substantial space charge density of positive ions in the
drift volume. In order to properly simulate such space charges, knowledge of
the ion mobility is necessary.
To this end, a small gaseous detector was constructed and the ion mobility of
various gas mixtures was measured. To validate the corresponding signal
analysis, simulations were performed.
Results are shown for several argon and neon based mixtures with different
fractions. A decrease of was measured for increasing water
content.Comment: 3 pages, 2 figure
Drift velocity and gain in argon- and xenon-based mixtures
We present measurements of drift velocities and gains in gas mixtures based
on Ar and Xe, with CO2, CH4, and N2 as quenchers, and compare them with
calculations. In particular, we show the dependence of Ar- and Xe-CO2 drift
velocities and gains on the amount of nitrogen contamination in the gas, which
in real experiments may build up through leaks. A quantification of the Penning
mechanism which contributes to the Townsend coefficients of a given gas mixture
is proposed.Comment: 11 pages, 7 figures, accepted for publication in Nucl.Instrum.Meth.
A. Data files available at http://www-alice.gsi.de/tr
A comprehensive study of rate capability in Multi-Wire Proportional Chambers
Systematic measurements on the rate capability of thin MWPCs operated in
Xenon, Argon and Neon mixtures using CO2 as UV-quencher are presented. A good
agreement between data and existing models has been found, allowing us to
present the rate capability of MWPCs in a comprehensive way and ultimately
connect it with the mobilities of the drifting ions.Comment: 29 pages, 18 figure
Gut Microbial Antigenic Mimicry in Autoimmunity
The gut microbiota plays a major role in the developmental biology and homeostasis of cells belonging to the adaptive and innate arms of the immune system. Alterations in its composition, which are known to be regulated by both genetic and environmental factors, can either promote or suppress the pathogenic processes underlying the development of various autoimmune diseases, including inflammatory bowel disease, multiple sclerosis, systemic lupus erythematosus, type 1 diabetes and rheumatoid arthritis, to just name a few. Cross-recognition of gut microbial antigens by autoreactive T cells as well as gut microbe-driven alterations in the activation and homeostasis of effector and regulatory T cells have been implicated in this process. Here, we summarize our current understanding of the positive and negative associations between alterations in the composition of the gut microbiota and the development of various autoimmune disorders, with a special emphasis on antigenic mimicry
Measurement of spark probability of GEM detector for CBM muon chamber (MUCH)
The stability of triple GEM detector setups in an environment of high
energetic showers is studied. To this end the spark probability in a shower
environment is compared to the spark probability in a pion beam.Comment: 5 pages, 10 figure
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