D0 H-Disk Cooling Channel Fluid/Thermal Design

Each H-disk ring assembly is comprised of 24 wedge assemblies that are mounted to a ring that provides both structural support and cooling to the detector wedges. Figure 1-1 shows the general layout of a disk assembly. In order for the H-disks to operate on the same cooling system as the rest of the silicon detectors, the pressure drop must be compatible with that of the overall system design. That is, the pressure drop for which the system is to operate, which will include cooling channels for bulkheads, Fdisks, and H-disks, should yield unthrottled flowrates in each cooling device that result in acceptable fluid temperature rises due to their respective heat loads. Too low a pressure drop in any channel would either rob flow from other portions of the detector or require that a higher total flow rate be supplied by the cooling system. Too high a pressure drop would yield an unacceptably large fluid temperature rise across the H-disk ring. In order to keep the detector temperatures low, thus reducing the effect of radiation damage to the silicon, the channel design should also minimize the difference between the bulk fluid temperature and the temperature of the mounting surfaces to which the wedges are attached. This is a significant portion of the overall temperature difference between the coolant fluid and the hottest portion of the silicon. This report compares calculated pressure drops to test results measured on ring mock-ups for two different channel designs. The cross-section of the two different channels discussed here are shown in Figure 1-2. Channel A is a simple rectangle with a 1 x 16 mm cross section, while Channel B has a serpentine cross section but maintains a width of 1 mm. Channel A represents an early design concept while Channel B represents the culmination of the design evolution. The serpentine Channel B design has a larger cross-sectional area than Channel A (29 vs. 16 square mm), so it is expected to have a lower {Delta}P. Its larger surface area, while maintaining the same gap height, provides improved heat transfer performance. Both of these channels assume that the ring inlet and outlet are 180{sup o} apart with the flow evenly split between ring halves. Channel configurations that had a single 360{sup o} channel were also considered. However, in order to keep {Delta}Ps low, larger channels were required to accommodate the higher flows through the channel, and larger gap heights lead to larger fluid-to-wall temperature differences. Therefore, this option was not developed further

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

Commissioning and initial performance of the Dark Energy Camera liquid nitrogen cooling system

The Dark Energy Camera and its cooling system has been shipped to Cerro Tololo Inter-American Observatory in Chile for installation onto the Blanco 4m telescope. Along with the camera, the cooling system has been installed in the Coudé room at the Blanco Telescope. Final installation of the cooling system and operations on the telescope is planned for the middle of 2012. Initial commissioning experiences and cooling system performance is described

Performance and Operation of the CMS Electromagnetic Calorimeter

The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented

Conceptual Design of the Modular Detector and Readout System for the CMB-S4 survey experiment

We present the conceptual design of the modular detector and readout system for the Cosmic Microwave Background Stage 4 (CMB-S4) ground-based survey experiment. CMB-S4 will map the cosmic microwave background (CMB) and the millimeter-wave sky to unprecedented sensitivity, using 500,000 superconducting detectors observing from Chile and Antarctica to map over 60 percent of the sky. The fundamental building block of the detector and readout system is a detector module package operated at 100 mK, which is connected to a readout and amplification chain that carries signals out to room temperature. It uses arrays of feedhorn-coupled orthomode transducers (OMT) that collect optical power from the sky onto dc-voltage-biased transition-edge sensor (TES) bolometers. The resulting current signal in the TESs is then amplified by a two-stage cryogenic Superconducting Quantum Interference Device (SQUID) system with a time-division multiplexer to reduce wire count, and matching room-temperature electronics to condition and transmit signals to the data acquisition system. Sensitivity and systematics requirements are being developed for the detector and readout system over a wide range of observing bands (20 to 300 GHz) and optical powers to accomplish CMB-S4's science goals. While the design incorporates the successes of previous generations of CMB instruments, CMB-S4 requires an order of magnitude more detectors than any prior experiment. This requires fabrication of complex superconducting circuits on over 10 square meters of silicon, as well as significant amounts of precision wiring, assembly and cryogenic testing.Comment: 25 pages, 15 figures, presented at and published in the proceedings of SPIE Astronomical Telescopes and Instrumentation 202

Trapping in irradiated p-on-n silicon sensors at fluences anticipated at the HL-LHC outer tracker

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 $\mu$m thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to $3 \cdot 10^{15}$ neq/cm$^2$. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations

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