Claude Leroy

The OPAL silicon strip microvertex detector with two coordinate readout

The OPAL experiment at the CERN LEP collider recently upgraded its silicon strip microvertex detector from one coordinate readout (φ only) to two coordinate readout (φ and z). This allows three dimensional vertex reconstruction and should improve lifetime measurements as well as b quark jet identification. This paper describes the new microvertex detector system with emphasis on the novel techniques and new components used to obtain the second coordinate information. These include the use of back-to-back single-sided detectors with orthogonally oriented readout strips, a gold printed circuit on a thin glass substrate to route the z strip signals to the electronics at the end of the detector, and the use of MX7 readout chips. Results on the performance of the new detector are presented.

Principles of radiation interaction in matter and detection

Electromagnetic Interaction of Radiation in Matter Nuclear Interactions in Matter Radiation Environments and Damage in Silicon Semiconductors Scintillating Media and Scintillator Detectors Solid State Detectors Displacement Damage and Particle Interactions in Silicon Devices Gas Filled Chambers Principles of Particle Energy Determination Superheated Droplet (Bubble) Detectors and CDM Search Medical Physics Applications.

Particle interaction and displacement damage in silicon devices operated in radiation environments

Silicon is used in radiation detectors and electronic devices. Nowadays, these devices achieving submicron technology are parts of integrated circuits of large to very large scale integration (VLSI). Silicon and silicon-based devices are commonly operated in many fields including particle physics experiments, nuclear medicine and space. Some of these fields present adverse radiation environments that may affect the operation of the devices. The particle energy deposition mechanisms by ionization and non-ionization processes are reviewed as well as the radiation-induced damage and its effect on device parameters evolution, depending on particle type, energy and fluence. The temporary or permanent damage inflicted by a single particle (single event effect) to electronic devices or integrated circuits is treated separately from the total ionizing dose (TID) effect for which the accumulated fluence causes degradation and from the displacement damage induced by the non-ionizing energy-loss (NIEL) deposition. Understanding of radiation effects on silicon devices has an impact on their design and allows the prediction of a specific device behaviour when exposed to a radiation field of interest.

The Physics Programme Of The MoEDAL Experiment At The LHC

The MoEDAL experiment at Point 8 of the LHC ring is the seventh and newest LHC experiment. It is dedicated to the search for highly-ionizing particle avatars of physics beyond the Standard Model, extending significantly the discovery horizon of the LHC. A MoEDAL discovery would have revolutionary implications for our fundamental understanding of the Microcosm. MoEDAL is an unconventional and largely passive LHC detector comprised of the largest array of Nuclear Track Detector stacks ever deployed at an accelerator, surrounding the intersection region at Point 8 on the LHC ring. Another novel feature is the use of paramagnetic trapping volumes to capture both electrically and magnetically charged highly-ionizing particles predicted in new physics scenarios. It includes an array of TimePix pixel devices for monitoring highly-ionizing particle backgrounds. The main passive elements of the MoEDAL detector do not require a trigger system, electronic readout, or online computerized data acquisition. The aim of this paper is to give an overview of the MoEDAL physics reach, which is largely complementary to the programs of the large multipurpose LHC detectors ATLAS and CMS.

Study of characteristics of silicon detectors irradiated with 24 GeV/c protons between −20°C and +20°C

High resistivity ion-implanted silicon pad detectors have been irradiated at +20°C, +10°C, 0°C and −20°C with 24 GeV/c protons at a flux of ∼ 5 × 109cm−2s−1, up to fluences of ∼ 1.1 × 1014cm−2, and maintained at these temperatures during several months after the end of irradiation. The change of the diode reverse current, full depletion voltage and collection efficiency of the charge, deposited by relativistic electrons, are presented as a function of the proton fluence and of annealing time. It is found that operating the detectors below +10°C limits the diode reverse current and the bias voltage necessary to achieve full depletion. Moreover, at these temperatures, the charge collection efficiency for an integration time of 20 ns (typical of LHC operation) is better than 90% for 300 μm detectors irradiated to a fluence of 1014 cm−2 and biased at 160 V.

Discrimination of nuclear recoils from alpha particles with superheated liquids

The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron-induced recoils.

A neutron irradiation facility featuring cryogenic temperatures and dedicated to Large Hadron Collider detector design

Abstract The SARA facility at Grenoble provides the possibility to carry out neutron irradiation studies at both cryogenic and room temperatures, and permits at the same time to measure on-line the deterioration of the electronic performance of the tested circuits. The cryogenic vessel consists of a 101 liquid argon cryostat placed behind the neutron source. A TOF technique was used to measure the neutron energy spectrum produced by the collision of a 20 MeV deuteron beam on a thick Be target. Alanine and thermoluminescent dosimeters were used to determine the neutron and photon doses. The results show that the neutron and the gamma dose components are about 78% and 22%, respectively. The angular distribution of the dose was also measured.

Physics of cascading shower generation and propagation in matter: principles of high-energy, ultrahigh-energy and compensating calorimetry

Calorimetry plays a crucial role in modern experimental physics. Calorimeters are essential tools to extract physics in accelerator and non-accelerator experiments. The physics phenomena at the base of cascading processes in matter and the basic principles of calorimeters operation are reviewed at the light of data obtained from running experiments or from sets of dedicated measurements and the constraints from physics requirements. From this understanding comes the possibility of building powerful calorimetric systems with the optimal performances required by future experiments at high-energy and ultrahigh-energy regimes.

Thermoluminescence analysis of - and -irradiated chemical vapour deposited diamond films

The thermoluminescent (TL) response of a set of synthetic diamond films obtained by chemical vapour deposition was investigated using gamma and beta radioactive sources over the dose range from 60 mGy to 3.5 Gy. A TL response linear with dose was generally observed. A numerical curve-fitting procedure was applied to deconvolute the complex-structured TL glow curves, which were found to be composed at most by five peaks in the temperature range between C to C. A short preheat treatment after irradiation allowed us to obtain a very stable smooth-shaped glow curve composed of a unique peak close to C. This isolated structure followed first-order kinetics over the whole dose range. The activation energy of the main peak, eV, was determined considering all samples and all irradiation doses using both the peak shape method and the fitting procedure. The corresponding frequency factor was estimated to be within the range -. The TL sensitivity of the diamond films calculated considering the isolated high-temperature peak compares favourably with that measured with a set of LiF TLD100 and TLD700 standard dosimeters.

New insights into particle detection with superheated liquids

We report new results obtained from calibrations of superheated liquid droplet detectors used in dark matter searches with different radiation sources (n, α, γ). In particular, detectors were spiked with α-emitters located inside and outside the droplets. It is shown that the responses have different temperature thresholds, depending on whether α-particles or recoil nuclei create the signals. The measured temperature threshold for recoiling 210Pb nuclei from 214Po α-decays was found to be in agreement with test beam measurements using mono-energetic neutrons. A comparison of the threshold data with theoretical predictions shows deviations, especially at high temperatures. It is shown that signals produced simultaneously by recoil nuclei and α-particles have more acoustic energy than signals produced by one or the other separately. A model is presented that describes how the observed intensities of particle-induced acoustic signals can be related to the dynamics of bubble growth in superheated liquids. A growth scenario that is limited by the inertia of the surrounding liquid shows a trend that is supported by the data. An improved understanding of the bubble dynamics is an important first step in obtaining better discrimination between particle types interacting in detectors of this kind.