Recent results on GaAs detectors - 137

The present understanding of the charge collection in GaAs detectors with respect to the materials used and its processing are discussed. The radiation induced degradation of the charge collection efficiency and the leakage current of the detectors are summarised. The status of strip and pixel detectors for the ATLAS experiment are reported along with the latest results from GaAs X-ray detectors for non-high energy physics applications.Comment: 7 pages. 4 postscript figures + 1 postscript preprint logo + 1 LaTeX file + 1 style file. Also available at http://ppewww.ph.gla.ac.uk/preprints/97/05

Commissioning and Field Tests of a Van-Mounted System for the Detection of Radioactive Sources and Special Nuclear Material

MODES-SNM project aimed at developing a mobile/portable modular detection system for radioactive sources and Special Nuclear Material (SNM). Its main goal was to deliver a tested prototype capable of passively detecting weak or shielded radioactive sources with accuracy higher than that of currently available systems. By the end of the project all the objectives have been successfully achieved. Results from the laboratory commissioning and the field tests are presented in this publication

Neutron induced radiation damage of KETEK SiPMs

Silicon photomultipliers (SiPMs), thanks to their excellent performance, are becoming the photodetectors of choice for many applications. One major limitation, in particular for their use at high-luminosity colliders, is the radiation damage by hadrons. In this work, SiPMs with 4384 pixels of 15 × 15 μm 2 size produced by KETEK have been irradiated by reactor neutrons to six fluences up to Φ eq = 10 12 cm -2 (1 MeV equivalent neutrons). Pulse-height, IV, and CV measurements with and without illumination by a LED for temperatures between -30 and 30° C have been performed. In this paper results from the IV, and CV measurements are shown. The fluence and the temperature dependence of the current and of the SiPM electrical parameters like pixel capacitance, quenching resistance and breakdown voltage allows to better understand the origin of the dark current and find ways to reduce the radiation-induced dark-count-rate

Aryl Hydrocarbon Receptor Is Critical for Homeostasis of Invariant gamma delta T Cells in the Murine Epidermis

An immunoregulatory role of aryl hydrocarbon receptor (AhR) has been shown in conventional alpha beta and gamma delta T cells, but its function in skin gamma delta T cells (dendritic epidermal T cells [DETC]) is unknown. In this study, we demonstrate that DETC express AhR in wildtype mice, and are specifically absent in the epidermis of AhR-deficient mice (AhR-KO). We show that DETC precursors are generated in the thymus and home to the skin. Proliferation of DETC in the skin was impaired in AhR-KO mice, resulting in a >90% loss compared with wild type. Surprisingly, DETC were not replaced by alpha beta T cells or conventional gamma delta T cells, suggesting a limited time frame for seeding this niche. We found that DETC from AhR-KO mice failed to express the receptor tyrosine kinase c-Kit, a known growth factor for gamma delta T cells in the gut. Moreover, we found that c-kit is a direct target of AhR, and propose that AhR-dependent c-Kit expression is potentially involved in DETC homeostasis. DETC are a major source of GM-CSF in the skin. Recently, we had shown that impaired Langerhans cell maturation in AhR-KO is related to low GM-CSF levels. Our findings suggest that the DETCs are necessary for LC maturation, and provide insights into a novel role for AhR in the maintenance of skin-specific gamma delta T cells, and its consequences for the skin immune network. The Journal of Immunology, 2011, 187: 3104-3110

AC-coupled n-in-p pixel detectors on MCz silicon with atomic layer deposition (ALD) grown thin film

We report initial characterization of our novel sensor process solutions with AC-coupled n+/p−/p+ pixel detectors made on 150 mm diameter p-type Magnetic Czochralski silicon (MCz-Si) wafers. The pixels were segmented in a 52 × 80 dual column array and designed to be AC capacitive coupled. The resistive coupling between pixels, allowing quality assurance probing prior the flip chip bonding, was realized with thin film metal-nitride resistors fabricated by sputtering deposition. This approach allows us to omit punch-through resistor structures, which reduces the overall process complexity. Moreover, our previous studies have emphasized that applying ALD Aluminum Oxide (Al2O3) field insulator and passivation layer results in negative net oxide charge and thus additional p-spray or p-stop surface current termination structures are not necessary. Our focused application is a radiation-hard ALD AC-coupled pixel detector to be used in future particle physics experiments, such as the High-Luminosity Large Hadron Collider (HL-LHC), as well as photon counting applications. The pixel detectors were tested at Helsinki Institute of Physics (HIP) Detector laboratory and Ruđer Bošković Institute (RBI). We show measurement data of pixel detectors and other test structures. For the TiN resistors surrounding pixels, the resistance values were measured to be about 15kΩ. Data of electrical properties, full depletion voltage and leakage current are shown as well. Our Transient Current Technique (TCT) measurements indicated clear pixel segmentation with excellent homogeneity. For further study, AC-coupled sensors were hybridized to PSI46dig read out chips (ROC) by flip-chip interconnection technique and tested with a radioactive source.Peer reviewe