Studio della risposta di dosimetri a stato solido da utilizzare per la misura dei campi di radiazione nell'esperimento CMS a LHC

In the CMS experiment at the Large Hadron Collider (LHC) intense radiation fields are expected during p-p collisions. To guarantee the correct functioning of CMS for many years, an on-line dosimetric system will be required to check the energy deposed (via ionizing and non-ionizing energy losses) in the detectors during collisions. In the present work, two types of solid-state dosimeters, p+/n/n+ diodes for fluence measurement and RadFETs for absorbed dose measurement, were tested in neutrons, protons, and positive pions beams. The analysis include the study of the response of the devices compared with the field intensities expected in CMS, as well as the study of different instabilities that could affect the measure of the absorbed dose for RadFETs dosimeters only

Radiation Monitoring in Mixed Environments at CERN: from the IRRAD6 Facility to the LHC Experiments

RadFET and p-i-n diode semiconductor dosimeters from different manufacturers will be used for radiation monitoring at the Experiments of the CERN LHC accelerator. In this work these sensors were exposed over three months in the CERN-IRRAD6 facility that provides mixed high-energy particles at low rates. The aim was to validate the operation of such sensors in a radiation field where the conditions are close to the ones expected inside full working LHC particle detectors. The results of this long-term irradiation campaign are presented, discussed and compared with measurements by other dosimetric means as well as Monte Carlo simulations. Finally, the integration of several dosimetric devices in one sensor carrier is also presented

THE TOTEM DETECTOR CONTROL SYSTEM

Abstract The detectors of the TOTEM experiment at the LHC (Roman Pots silicon detectors, CSC & GEM) require the monitoring and control of the usual equipment used in HEP: HV/LV power supplies, VME crates and environmental sensors readout using ELMBs or through the DCU technology. Moreover, while most of the LHC experiments exploit fixed detectors, the TOTEM DCS -Big Brother-includes the control of movable parts (the Roman Pots) to keep the sensors at a specified distance from the beams. The TOTEM DCS differs from those of other LHC experiments in many ways. Engineering and project management follow a structured approach inspired by the ESA ECSS collaborative space standards. Project phasing and planning is done with GDPM on a weekly basis. The collection of functional and technical requirements uses an extension of the ALICE strategy. The Configuration Management is organized using SubVersioN. Also a set of scripts is developed to transform formal requirement representations into SW configuration (PVSS)

The First 1 1/2 Years of TOTEM Roman Pot Operation at LHC

Since the LHC running season 2010, the TOTEM Roman Pots (RPs) are fully operational and serve for collecting elastic and diffractive proton-proton scattering data. Like for other moveable devices approaching the high intensity LHC beams, a reliable and precise control of the RP position is critical to machine protection. After a review of the RP movement control and position interlock system, the crucial task of alignment will be discussed.Comment: 3 pages, 6 figures; 2nd International Particle Accelerator Conference (IPAC 2011), San Sebastian, Spain; contribution MOPO01

Experimental determination of proton hardness factors at several irradiation facilities

The effort to characterise detector sensors and components for the High Luminosity upgrade of the CERN Large Hadron Collider requires collaboration between irradiation facilities around the world. By convention, the radiation damage following irradiation with particle beams is reported as the 1 MeV neutron equivalent fluence, obtained using the corresponding hardness factor. Measurements of proton hardness factors at three different kinetic energies are presented, by characterisation of commercially available diodes before and after irradiation, using irradiations at the University of Birmingham, the Karlsruhe Institute of Technology, and CERN. Possible future improvements to these measurements are also discussed

Modification of amorphous and microcrystalline silicon film properties after irradiation with MeV and GeV protons

It is well known that the degree of crystallinity has a prominent influence on the stability of Silicon under proton irradiation. Amorphous silicon films are much more stable than mono- or polycrystalline silicon substrates or microcrystalline silicon thin films. In particular it has been shown, that in a micromorph tandem solar cell irradiated with protons in the lower MeV energy range only the microcrystalline diode showed a pronounced decrease in photocurrent after irradiation1. The proton irradiation induced damage in thick crystalline silicon samples has a maximum at beam energies between 1MeV and 4MeV and decreases for further increasing proton energies. However, irradiating an amorphous silicon/crystalline silicon heterojunction solar cell with a relatively dose of 24GeV, we observed a very strong drop in conversion efficiency with only minor recovery after sample annealing. In literature it has been reported 2, that the degradation of amorphous silicon is negligible for proton energies above 100MeV. In order to clarify to which extent also the thin film top layer of the hetero solar cell is affected by the proton irradiation, we exposed a variety of thin film silicon samples either to a 1.7MeV beam with a dose of 5.1012 protons/cm2 or to a 24GeV beam with a dose of 5 .1013 protons/cm2. The investigated intrinsic, p-type and n-type amorphous and microcrystalline silicon films have been deposited by conventional plasma deposition under variation of the silane / hydrogen gas phase ratio. Raman measurements have been done in order to determine the order of crystallinity obtained under various deposition conditions. We observed even at 24GeV a clear modification in the electrical characteristics of the films. Temperature dependent measurements of the dark current revealed in particular for all doped samples a significant increase of the activation energy, that might be explained by a decrease of the dopant efficiency, while for intrinsic a-Si:H layers the increasing activation energy is due to deep defect creation

Diamond Detectors for the TOTEM Timing Upgrade

This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with about 50 ps time precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2 and will tag the central diffractive events up to an interaction pileup of about 1. A dedicated fast and low noise electronics for the signal amplification has been developed. The digitization of the diamond signal is performed by sampling the waveform. After introducing the physics studies that will most profit from the addition of these new detectors, we discuss in detail the optimization and the performance of the first TOF detector installed in the LHC in November 2015.Comment: 26 pages, 18 figures, 2 tables, submitted for publication to JINS

Double diffractive cross-section measurement in the forward region at LHC

The first double diffractive cross-section measurement in the very forward region has been carried out by the TOTEM experiment at the LHC with center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of double diffractive pp events was extracted. From these events, we measured the cross-section sigma_DD =(116 +- 25) mub for events where both diffractive systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio