482 research outputs found
The COMPASS Experiment and the measurement of the gluon polarisation
COMPASS, a new fixed target experiment at CERN, aimed at the study of nucleon
spin structure and hadron spectroscopy, has started to collect physics data in
Autumn 2001. This paper describes the COMPASS apparatus and the measurement of
the gluon polarisation . The apparatus consists in a solid state
polarised target and a two stage spectro-meter with high resolution tracking,
particle identification and calorimetry, capable of standing high event rates.
COMPASS measures the longitudinal spin asymmetry of open charm production in
polarised deep inelastic muon nucleon scattering: this asymmetry is directly
related to since at COMPASS energies open charm is essentially
produced by photon gluon fusion only. A second channel, used to access with higher statistics, is the production of correlated high hadron
pairs.Comment: 6 pages, 3 figures in eps and 1 in jpg, talk given at XXXI
International Symposium on Multiparticle Dynamics, Sept 1-7, 2001, Datong
China. see http://ismd31.ccnu.edu.cn
CLAM, a continuous line alignment and monitoring method for RICH mirrors
A method is proposed for the angular alignment of RICH mirrors and for its monitoring, in particular for the COMPASS RICH-1 mirror system. Observing (by means of four cameras) apparent discontinuities in the images of continuous linear objects reflected by the mirrors surface, a relative misalignment of adjacent mirrors can be deduced and then corrected. The method can attain a sensitivity of at least 0.1 mrad, and can also be applied on-line to keep under control the stability of the mirrors during data taking
RHIP, a Radio-controlled High-Voltage Insulated Picoammeter and its usage in studying ion backflow in MPGD-based photon detectors
A picoammeter system has been developed and engineering. It consists in a
current-voltage converter, based on an operational amplifier with very low
input current, a high precision ADC, a radio controlled data acquisition unit
and the computer-based control, visualization and storage. The precision is of
the order of a tenth of picoampers and it can measure currents between
electrodes at potentials up to 8 kV. The system is battery powered and a number
of strategies have been implemented to limit the power consumption. The system
is designed for multichannel applications, up to 256 parallel channels. The
overall implementation is cost-effective to make the availability of
multichannel setups easily affordable. The design, implementation and
performance of the picoammeter system are described in detail as well as a an
application: the measurement of ion backflow in MPGD-based photon detectors.Comment: 5th International Conference on Micro-Pattern Gas Detectors
(MPGD2017), presentation by Silvia Dalla Torr
Remote alignment of large mirror array for RICH detectors
Image focusing in large RICH detectors is obtained by composite systems of mirror elements. Monitoring and adjusting the alignment of the mirror elements during data taking are important handles to improve the detector resolution. Mirror adjustment via piezoelectric actuators can combine unprecedented accuracy and match some fundamental requirements: the detector material budget can be kept low and the high purity of the gas radiator can be preserved, a prerequisite when UV photons are detected. A system based on this principle, well suited for COMPASS RICH-1 mirrors, is proposed
Development of large area resistive electrodes for ATLAS NSW Micromegas
Micromegas with resistive anodes will be used for the NSW upgrades of the ATLAS experiment at LHC. Resistive electrodes are used in MPGD devices to prevent sparks in high-rate operation. Large-area resistive electrodes for Micromegas have been developed using two different technologies: screen printing and carbon sputtering. The maximum resistive foil size is 45 Ă— 220 cm with a printed pattern of 425-ÎĽm pitch strips. These technologies are also suitable for mass production. Prototypes of a production model series have been successfully produced. In this paper, we report the development, the production status, and the test results of resistive Micromegas
Study of MicroPattern Gaseous detectors with novel nanodiamond based photocathodes for single photon detection in EIC RICH
Identification of high momentum hadrons at the future EIC is crucial, gaseous
RICH detectors are therefore viable option. Compact collider setups impose to
construct RICHes with small radiator length, hence significantly limiting the
number of detected photons. More photons can be detected in the far UV region,
using a windowless RICH approach. QE of CsI degrades under strong irradiation
and air contamination. Nanodiamond based photocathodes (PCs) are being
developed as an alternative to CsI. Recent development of layers of
hydrogenated nanodiamond powders as an alternative photosensitive material and
their performance, when coupled to the THick Gaseous Electron Multipliers
(THGEM)-based detectors, are the objects of an ongoing R\&D. We report about
the initial phase of our studies.Comment: 3 pages, 5 figures, RICH2018 conference proceedin
Characterization of the water diffusion in GEM foil material
Systematic studies on the GEM foil material are performed to measure the moisture diffusion rate and saturation level.These studies are important because the presence of this compound inside the detector’s foil can possibly change its mechanical and electrical properties,and in such a way,the detector performance can be affected.To understand this phenomenon,a model is developed with COMSOL Multiphysicsv.4.3 which described the adsorption and diffusion within the geometry of GEM foil,the concentration profiles and the time required to saturate the foil.The COMSOL model is verified by experimental observations on a GEM foil sample.This note will describe the model and its experimental verification results
THGEM operation in Ne and Ne/CH4
The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH4
mixtures, features high multiplication factors at relatively low operation
potentials, in both single- and double-THGEM configurations. We present some
systematic data measured with UV-photons and soft x-rays, in various Ne
mixtures. It includes gain dependence on hole diameter and gas purity,
photoelectron extraction efficiency from CsI photocathodes into the gas,
long-term gain stability and pulse rise-time. Position resolution of a 100x100
mm^2 X-rays imaging detector is presented. Possible applications are discussed.Comment: Submitted to JINST, 25 pages, 33 figure
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