Pattern recognition and PID for COMPASS RICH-1 Abbon, P.; Alexeev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2008, Letnik:
595, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A package for pattern recognition and PID by COMPASS RICH-1 has been developed and used for the analysis of COMPASS data collected in the years 2002–2004, and 2006–2007 with the upgraded RICH-1 ...photon detectors. It has allowed the full characterization of the detector in the starting version and in the upgraded one as well as the PID for physics results. We report about the package structure and algorithms, and the detector characterization and PID results.
The fast photon detection system of COMPASS RICH-1 Abbon, P.; Alekseev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2007, Letnik:
581, Številka:
1
Journal Article
Recenzirano
A fast photon detection system has been built for the upgrade of COMPASS RICH-1, the large size gaseous RICH detector in use at the COMPASS Experiment at the CERN SPS since 2001. The photon detectors ...of the central region have been replaced by a new system based on multi-anode photomultipliers coupled to individual fused silica lens telescopes and a fast readout electronics system, while in the outer region the existing MWPCs with CsI photocathodes have been equipped with a new readout system, based on the APV chip. RICH-1 has been successfully operated in its upgraded version during the 2006 run. We report on the upgrade design and construction, and on the preliminary characterization of the upgraded RICH-1 performances: at saturation about 60 photons per ring have routinely been obtained and the background level has drastically been reduced thanks to the good time resolution of the new system, leading to a 2
σ
π
–K separation above 55
GeV/
c.
Design and status of COMPASS FAST-RICH Abbon, P.; Alekseev, M.; Angerer, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2006, Letnik:
567, Številka:
1
Journal Article
Recenzirano
In the context of the upgrade of COMPASS RICH-1, we are developing a fast photodetection system for RICH counters, based on UV extended Multi-Anode PhotoMultiplier Tubes (MAPMT) and a custom, low ...dead-time electronic readout system. Photons are concentrated on the MAPMT photocathode by an optical system that preserves the position information. The ratio between the collection and the photosensitive surfaces is
∼
7.5
in our design, larger than in previous applications. A new front-end electronics, based on a modified version of the MAD4 discriminator chip, is being realized to digitize the MAPMT signals. We report about the design of the photodetection system and of the associated electronic readout system, and on the preliminary test beam results.
Ion back flow reduction in a THGEM based detector Alexeev, M.; Dasgupta, S. S.; Denisov, O. ...
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC),
2012-Oct.
Conference Proceeding
Cherenkov imaging counters requiring large photosensitive areas, the capability to stand high rates and to operate in magnetic field environments could benefit from the use of micropattern gas ...detectors based on THick Gaseous Electron Multiplier (THGEM) coupled to a solid state CsI photo-cathode. Nevertheless, the ions produced in the charge multiplication processes, which end up in the CsI photocathode Ion Back Flow (IBF) compromise the detector performance: fast ageing of the CsI photocathode, as well as electron extraction resulting in spurious signals and eventual discharges can occur. To avoid and limit these undesired events, several configurations of THGEM based detectors were considered. Some changing the whole detector geometry by changing the relative position of individual THGEMs to take advantage of the microscopic diffusion properties of electrons and ions. One other configuration changing directly the geometry of the THGEM itself to better create an ion trap, the THCOBRA, is also studied. In this work, experimental and simulation studies of these configurations is performed, particularly concerning IBF and gain. Finite element method calculations and Monte-Carlo simulations are performed for a better understanding of the results.
Changes in the radiation-induced transparency of scintillating and wavelength-shifting fibers were studied by means of on-line-induced absorption coefficient measurement during and after gamma ...irradiation. It was found that the main contribution to radiation damage was caused by reactions between luminescent molecules. The time dependence of the radiation-induced absorption coefficient was analyzed in the broad spectral range (420–735nm) and compared with kinetic models of the processes of absorption center build-up and recovery. The latter has been recently published for these fibers and a lower dose rate in the range of 0.002–0.01Gys−1. Good agreement was reached between the low-dose and the presented high-dose measurements (dose rate 4.2Gys−1). The parameters calculated in this kinetic model are applicable to prediction of the fiber behavior in particle physics experiments.
The analysing power of the reaction \({\rm n} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{-}\) for neutron energies between threshold and 570 MeV has been determined using a transversely polarised ...neutron beam at PSI. The reaction has been studied in a kinematically complete measurement using a time-of-flight spectrometer with large acceptance. Analysing powers have been determined as a function of the c.m. pion angle in different regions of the proton-proton invariant mass. They are compared to other data from the reactions \({\rm n} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{-}\) and \({{\rm p} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{0}}\). The np elastic scattering analysing power was determined as a by-product of the measurements.
COMPASS is a fixed target experiment at CERN SPS aimed to study hadron structure and spectroscopy. Hadron identification in the momentum range between \(3\) and \(55 GeV/c\) is provided by a large ...gaseous Ring Imaging Cherenkov Counter, RICH-1. To cope with the challenges imposed by the new physics program of COMPASS, RICH-1 has been upgraded by replacing four MWPC-based photon detectors with newly developed MPGD-based photon detectors. The architecture of the novel detectors is a hybrid combination of two layers of THGEMs and a Micromegas. The top of the first THGEM is coated with CsI acting as a reflective photo-cathode. The anode is segmented in pads capacitively coupled to the APV-25 based readout. The new hybrid detectors have been commissioned during the 2016 COMPASS data taking and stably operated during the 2017 run. In this paper design, construction, operation and performance aspects of the novel photon detectors for COMPASS RICH-1 are discussed.
The reaction np arrow right pp pi super(-) has been studied in a kinematically complete measurement with a large acceptance time-of-flight spectrometer for incident neutron energies between threshold ...and 570 MeV. The proton-proton invariant mass distributions show a strong enhancement due to the pp( super(1)S sub(0)) final state interaction. A large anisotropy was found in the pion angular distributions in contrast to the reaction pp arrow right pp pi super(0). At small energies, a large forward/backward asymmetry has been observed. From the measured integrated cross section sigma (np arrow right pp pi super(-)), the isoscalar cross section sigma sub(01) has been extracted. Its energy dependence indicates that mainly partial waves with Sp final states contribute.
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