A dedicated front-end electronics has been developed for the trigger chambers of the ALICE muon spectrometer under construction at the future LHC at CERN. This trigger detector is based on RPCs ...(Resistive Plate Chambers) working in streamer mode. The number of electronics channels (about 21000) and the fact that RPC signals have specific characteristics have led to the design of an 8 channel front-end ASIC using a new discrimination technique. The principle of the ASIC is described and the radiation hardness is discussed. Special emphasis is put on production characteristics of about 4000 ASICs.
Ageing tests on the low-resistivity RPC for the ALICE dimuon arm Arnaldi, R.; Baldit, A.; Barret, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2003, Letnik:
508, Številka:
1-2
Journal Article
Resistive Plate Chambers operated in streamer mode have been chosen as trigger detectors for the forward dimuon spectrometer of the ALICE experiment. During tests performed at CERN PS, small size ...prototypes with low-resistivity bakelite electrodes and with a strongly quenched gas mixture have shown the required rate capability, tracking and timing properties. Present efforts are devoted to the study of the detector performance after long irradiation periods. In this paper, a summary of the results of aging tests performed at the Gamma Irradiation Facility at CERN will be presented. Detectors show quite stable performance up to about 50mC/cm2, as the requirements for 10years operation program at LHC including a safety factor of 2. Afterwards, we observed an increase of the dark current not associated with an increase of the counting rate. We also report results of chemical analysis carried out by different CERN teams on exhaust gases and electrode surfaces of the detectors after aging.
The Zero Degree Calorimeters (ZDCs) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC. Since all the spectator nucleons have the same ...energy, the calorimeter reponse is proportional to their umber providing a direct information on the centrality of the collision. Two sets of ZDCs are located at opposite sides with respect to the interaction point (I), 116 m away from it Each set consists of a neutron (ZN) calorimeter, placed between the two beam pipes, an a proton (ZP) calorimeter, posioned externally to the outgoing beam pipe. The ZDCs spaghetti calorimeters, which detect the Cherenkov light produced by the shower particle in silica optical fibers embedded in a dense absorber. In summer 2007 the ZN and ZP calorimeters have been placed on a movable platform and then installed in the LHC tunnel. The results of the commissioning studies and in particular the solutions adopted to control the stability of the PMTs response will be shown: light injection with a larser diode and cosmic rays. The foreseen calibration with e.m. dissociation event in Pb-Pb collisions will also be disussed. Finally the it meaurements carried out during the commissining in the LHC tunnel will be presentend.
To assess the value of micronuclei in the characterization of precancerous lesions of the oral cavity with reference to their likelihood of progressing to malignant lesions.
The frequency of ...micronuclei was determined in exfoliated cells from normal oral mucosa, a preneoplastic condition (leukoplakia) and precancerous lesions with and without dysplasia, squamous cell carcinomas and sites of previous carcinomas that had been removed.
Average micronucleus frequencies were increased in precancerous lesions as compared to normal mucosa and further increased in carcinomas, suggesting that micronuclei are a biomarker of neoplastic progression in this type of cancer. With all samples, micronucleus frequencies were systematically higher when cells were collected by vigorous than by light scraping, suggesting a decreasing gradient from basal to superficial layers of mucosa. The micronucleus frequency did not vary with the sex or age of patients, while it did vary with the anatomic site of the lesions.
Although the gradual increase in micronucleus counts from normal mucosa to precancerous lesions to carcinomas suggests a link of this biomarker with neoplastic progression, the large overlapping of data prevents its use as a predictor of progression of precancerous lesions to malignancy in individual patients.
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