Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is (99.95 ± 0.05) %, while the intrinsic spatial resolutions are (4.80 ± 0.25) μm and (7.99 ± 0.21) μm along the 100 μm and 150 μm pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.Peer reviewe

P-Type Silicon Strip Sensors for the new CMS Tracker at HL-L-HC

Abstract: The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type

Age-dependent calibration factors for in-vivo monitoring of 131I in thyroid using Monte Carlo simulations

International audienceFollowing a nuclear incident, 131I monitoring is usually carried out by performing in vivo measurements of the retained activity in the thyroid. The measurement equipment needs to be calibrated in order to convert thyroid count rates into retained activity. This calibration relies on measurements or Monte Carlo computations using appropriate anthropomorphic model of the thyroid gland contaminated with a known activity of the radionuclide of interest. Several factors influence the calibration procedure, such as the geometry, the individual anatomical characteristics, and the presence of 131I in other organs and tissues of the body. In particular, given their age-dependent anatomical changes, appropriate values of detector efficiencies for children are necessary to reduce results uncertainties when children are involved. In this study, Monte Carlo simulations for several detectors and phantoms of different ages have been performed to investigate the variation of the detection efficiency with distance, age and thyroid volume. It was found that the counting efficiency varies linearly with the thyroid volume and inversely with the squared detector-phantom distance. Age-dependent correction factors to be applied to the adult calibration factor have been derived and can be used when calibration factors for children are not available. © 2019 Elsevier Lt

European intercomparison on the measurement of l-131 in thyroid of adults and children

International audienceIn case of a nuclear reactor accident affecting a large population the internal contamination of the workers and the public can be assessed through in vivo measurements. Since iodine-131 is one of the most important releases and since it is of health concern, thyroid monitoring of this radionuclide is of special interest. Intercomparisons of thyroid in vivo measurements usually focus on the adult case. Here we report about a European intercomparison exercise for spectroscopic devices. Three sets of thyroid phantoms of unknown activity were circulated, representing the following ages 5 years-old, 10 years-old and the adult. Nineteen institutions from twelve countries in Europe took part in an intercomparison exercise. Twenty-nine measurement devices have been tested. In the adult case, 5 results were outside the acceptance criteria and 10 in the 10-years old case. In the 5 years-old case, the result was not reported for one measurement device and 11 results were outside the acceptance criteria. Devices that have been tested during this intercomparison now dispose of calibration coefficients for the three age groups. © 201

European intercomparison on the measurement of l-131 in thyroid of adults and children

International audienceIn case of a nuclear reactor accident affecting a large population the internal contamination of the workers and the public can be assessed through in vivo measurements. Since iodine-131 is one of the most important releases and since it is of health concern, thyroid monitoring of this radionuclide is of special interest. Intercomparisons of thyroid in vivo measurements usually focus on the adult case. Here we report about a European intercomparison exercise for spectroscopic devices. Three sets of thyroid phantoms of unknown activity were circulated, representing the following ages 5 years-old, 10 years-old and the adult. Nineteen institutions from twelve countries in Europe took part in an intercomparison exercise. Twenty-nine measurement devices have been tested. In the adult case, 5 results were outside the acceptance criteria and 10 in the 10-years old case. In the 5 years-old case, the result was not reported for one measurement device and 11 results were outside the acceptance criteria. Devices that have been tested during this intercomparison now dispose of calibration coefficients for the three age groups. © 201

Alignment of the CMS silicon strip tracker during stand-alone commissioning

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15C to -15C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) microns in the outer (inner) part of the barrel.Comment: 41 pages, 63 postscript figures, submitted to JINS