Thermal Analysis of a D0 H-Disk Wedge

Each H-Disk ring assembly is comprised of 24 wedge assemblies. Figures 1-1 and 1-2 show the wedge mechanical layout. Each wedge consists of sets of two single-sided silicon detectors (referred to as inner and outer detectors, corresponding to their radial positioning) as provided by Moscow State University. Since these detectors are single sided, two mated inner/outer sets are arranged back-to-back such that they effectively become a double-sided detector with a 15{sup o} angle between the strips on either side. Six SVX II chips are mounted near the outboard edge of each outer detector since this location provides access to bond pads spanning the entire detector surface. Since the detector and chip bond pads are on significantly different pitches (approximately 80 vs. 48 microns), a pitch adapter is used to transition this jump, thus simplifying wirebonding. With the accompanying electronics required to support detector operation placed adjacent to the chips, the mountirig ring, which also acts as a means of cooling for the wedge, is by necessity located some distance from the chips, which are the primary heat source. The purpose of this report is to document the results of a thermal performance study of a wedge assembly. The methods, assumptions, and results for this investigation are discussed

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

DECam integration tests on telescope simulator

The Dark Energy Survey (DES) is a next generation optical survey aimed at measuring the expansion history of the universe using four probes: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the survey, the DES Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera which will be mounted at the Blanco 4-meter telescope at the Cerro Tololo Inter- American Observatory. DES will survey 5000 square degrees of the southern galactic cap in 5 filters (g, r, i, z, Y). DECam will be comprised of 74 250 micron thick fully depleted CCDs: 62 2k x 4k CCDs for imaging and 12 2k x 2k CCDs for guiding and focus. Construction of DECam is nearing completion. In order to verify that the camera meets technical specifications for DES and to reduce the time required to commission the instrument, we have constructed a full sized telescope simulator and performed full system testing and integration prior to shipping. To complete this comprehensive test phase we have simulated a DES observing run in which we have collected 4 nights worth of data. We report on the results of these unique tests performed for the DECam and its impact on the experiments progress.Comment: Proceedings of the 2nd International Conference on Technology and Instrumentation in Particle Physics (TIPP 2011). To appear in Physics Procedia. 8 pages, 3 figure

Phylogenetic comparative analysis of electric communication signals in ghost knifefishes (Gymnotiformes: Apteronotidae)

Electrocommunication signals in electric fish are diverse, easily recorded and have well-characterized neural control. Two signal features, the frequency and waveform of the electric organ discharge (EOD), vary widely across species. Modulations of the EOD (i.e. chirps and gradual frequency rises) also function as active communication signals during social interactions, but they have been studied in relatively few species. We compared the electrocommunication signals of 13 species in the largest gymnotiform family, Apteronotidae. Playback stimuli were used to elicit chirps and rises. We analyzed EOD frequency and waveform and the production and structure of chirps and rises. Species diversity in these signals was characterized with discriminant function analyses, and correlations between signal parameters were tested with phylogenetic comparative methods. Signals varied markedly across species and even between congeners and populations of the same species. Chirps and EODs were particularly evolutionarily labile, whereas rises differed little across species. Although all chirp parameters contributed to species differences in these signals, chirp amplitude modulation, frequency modulation (FM) and duration were particularly diverse. Within this diversity, however, interspecific correlations between chirp parameters suggest that mechanistic trade-offs may shape some aspects of signal evolution. In particular, a consistent trade-off between FM and EOD amplitude during chirps is likely to have influenced the evolution of chirp structure. These patterns suggest that functional or mechanistic linkages between signal parameters (e.g. the inability of electromotor neurons increase their firing rates without a loss of synchrony or amplitude of action potentials) constrain the evolution of signal structure

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