Ch. Petridou

The thermoluminescence behaviour of LiF(TLD-100) for doses up to 10 MRad

Abstract The behaviour of the thermoluminescence of LiF (TLD-100) was studied, for doses up to 10M Rad. At these doses, peaks appear, grow and disappear. The total TL between 60°C and 600°C was found to increase for doses up to 105 Rad and to decrease by up to a factor of 2 for higher doses. Changes in the shape of the peaks were observed as well as a shift of their maxima on the temperature scale. In particular, a peak at about 480°C was investigated. The results are discussed and possible explanations of the phenomena are offered.

A Multi-Core FPGA-Based 2D-Clustering Implementation for Real-Time Image Processing

A multi-core FPGA-based 2D-clustering implementation for real-time image processing is presented in this paper. The clustering algorithm is using a moving window technique to reduce the time and data required for the cluster identification process. The implementation is fully generic, with an adjustable detection window size. A fundamental characteristic of the implementation is that multiple clustering cores can be instantiated. Each core can work on a different identification window that processes data of independent “images” in parallel, thus, increasing performance by exploiting more FPGA resources. The algorithm and implementation are developed for the Fast TracKer processor for the trigger upgrade of the ATLAS experiment but their generic design makes them easily adjustable to other demanding image processing applications that require real-time pixel clustering.

Non-radiation induced thermoluminescence in pre-irradiated LiF (TLD-100) w

Abstract The appearance of non-radiation induced TL was observed in LiF (TLD-100) which had been irridiated with a 5 MRad γ-dose and heated to 400 °C after irradiation. The non-radiation induced TL was also observed at subsequent heatings. Its behaviour with time and its magnitude at subsequent heatings were investigated. The properties of the peaks observed were examined and a theoretical model is proposed, which is based on deep traps, for the explanation of the effect.

Extensive performance studies for the ATLAS BIS-MDT precision muon chambers with cosmic rays

ATLAS (A Toroidal LHC ApparatuS) is a general-purpose experiment, which will start its operation at the Large Hadron Collider (LHC) at CERN in 2007. The ATLAS detector is designed to explore numerous physics processes by measuring, recording, and investigating the products emerging from proton-proton collisions at energies up to 14 TeV. High-precision muon momentum measurement (dp/p-10% at p/sub T/=1 TeV/c) over large areas using Monitored Drift Tube (MDT) chambers is crucial for the ATLAS experiment. More than 1,200 MDT chambers, assembled from approximately 370,000 drift tubes operated at 3 bar pressure, will be used to provide for the total detector coverage of 5,500 m/sup 2/. Three Greek universities have taken the responsibility to construct 30,000 drift tubes of /spl sim/1.7 in length, to test them and finally assemble them into 120 BIS (Barrel Inner Small) chambers. The design of the muon drift tubes aims at high efficiency (>95%) and a spatial resolution of <80 /spl mu/m (single tube resolution). This paper describes the cosmic ray setup, which has been instrumented in order to verify. that the BIS chamber Module-0 fulfils its design requirements. The analysis of its data shows that the chamber meets these requirements; it has low noise levels, uniform drift properties, good spatial resolution and high particle detection efficiency.

Aging studies for the ATLAS monitor drift tubes using alpha particles

A systematic study of the behavior of the ATLAS monitored drift tubes (MDTs) under controlled irradiation by alpha particles has been performed. The aim of the study was two fold: to quantify the response of the tubes to alpha particles and consequence to heavily ionizing particles and to measure aging effects under the nominal operating conditions. A setup of a well controlled radium (/sup 226/Ra) source was used in order to enrich the tube gas (Ar, CO/sub 2/) with the alpha emitter /sup 222/Rn and irradiate the tubes internally. The ionization produced by an alpha particle with mean energy of 6.4 MeV has been measured. The energy deposition of the alpha and beta rays of the source inside the tube was computed by simulating the MDT geometry and the accumulated charge to the tube wire at operating conditions was calculated. The results of aging effects up to an accumulated charge of 41.5 mC are given by using the alpha-irradiation setup.

A highly parallel FPGA implementation of a 2D-clustering algorithm for the ATLAS Fast TracKer (FTK) processor

The highly parallel 2D-clustering FPGA implementation used for the input system of the Fast TracKer (FTK) processor for the ATLAS experiment of the Large Hadron Collider (LHC) at CERN is presented. The LHC after the 2013-2014 shutdown periods is planned to have increased luminosity, which will make it more difficult to have efficient online selection of rare events due to the increase of the overlapping collisions. FTK is a highly-parallelized hardware system that improves the online selection by executing real time track finding using the information from the silicon inner detector. The FTK system requires fast and robust clustering of the hits retrieved from the silicon detector on FPGA devices. We show the development of the original input boards and the implemented clustering algorithm. For the complicated 2D-clustering, a moving window technique is used to minimize the use of FPGA resources. The combination of custom developed boards and implementation of the clustering algorithm provides sufficient processing power to meet the specifications for the silicon inner detector of ATLAS up to the maximum LHC luminosity planned until 2022. The developed algorithm is easily adjustable to other image processing applications that require real-time 2D-clustering.

The performance of the ATLAS innermost MDT muon precision tracker in cosmic rays and in positron and muon beams

The ATLAS muon spectrometer has been designed to measure final state muons from proton-proton interactions at the LHC with good momentum resolution (from 3% up to 10% for muons of momentum of 1 TeV). Monitored drift tube (MDT) chambers are used for precision tracking covering the area |eta| > 2.7. The MDTs are built from aluminum tubes filled with Ar/CO2 at a pressure of 3 bar, operated at 3080 V (gas gain 2 times 104). Each tube measures charged particle tracks with an average spatial resolution better than 80 mum and with high efficiency (>95%). Extensive studies of the performance of the barrel inner small chambers have been accomplished both with cosmic rays and positron and muon test beams. A complete study, of the effect of fluctuations in the chamber operating conditions (HV, pressure, gas composition, and analogue pulse height threshold) on the resolution and efficiency of individual tubes, with cosmic muons, is presented in this work. The track reconstruction quality for muon and positron beams in a dedicated setup at the H8 ATLAS test beam at CERN, of various beam incident angles, are also reported.

Study of the performance of the ATLAS monitored drift tube chambers under the influence of heavily ionizing /spl alpha/-particles

The MDT chambers of the ATLAS Muon Spectrometer will operate in a heavy LHC background environment mainly from photons and neutrons. The ionization produced by neutron recoils is much higher than the one from photons or muons and can be simulated by the use of alpha particles. A systematic study of the behavior of the ATLAS Monitored Drift Tubes (MDTs) under controlled irradiation has been performed. The presence of alpha particles results in the reduction of the gas gain due to space charge effects. The gas gain reduction has been studied in a single tube set up using a well controlled radium (/sup 226/Ra) source in order to enrich the tube gas (Ar/CO/sub 2/) with the alpha emitter /sup 220/Rn and irradiate the tubes internally. The results are confronted with Garfield simulations.