Design of the cooling systems for the multiplicity and vertex detector
This report presents the final mechanical designs of the cooling systems for the Multiplicity and Vertex Detector (MVD). In particular, the design procedure and layouts are discussed for two different air cooling systems for the multichip modules and MVD enclosure, and a liquid cooling system for the low dropout voltage regulators. First of all, experimental prototype cooling system test results used to drive the final mechanical designs are summarized and discussed. Next, the cooling system
... e cooling system requirements and design calculation for the various subsystem components are presented along with detailed lists of supply vendors, components, and costs. Finally, safety measures incorporated in the final mechanical design and operation procedures for each of the subsystems are detailed. MVD Overview and Electronics Cooling Strategies The PHENIX experiment at the Relativistic Heavy Ion Coliider (RHIC) at Brookhaven National Laboratory is being constructed to investigate a phase of matter termed the quark-gluon plasma. The plasma will be produced through the collision of two heavy ions. The multiplicity and vertex detector (MVD) located in the center of PHENIX will characterize the event, determine the collision point, and act as a central trigger. This report serves to present the detailed designs of the MVD's electronics cooling systems. Consequently, only relevant information of the most genera1 and cooling system related components will be presented here. For a more thorough discussion, the reader is directed to the web site http://p2hp2.lanl.gov/phenix/mvd. 1 "clam-shell" fashion to allow far installation around the ion-collision beam pipe. Each clam-shell-like half of the MVD is identical in construction and operation. The central portion of an MVD half section contains twelve C-shaped Rohacell foam cages that house silicon strip detectors used to detect charged particles emitted during heavy ion collisions. Each silicon detector is connected with a Kapton cable to a multichip module (MCM) that contains the necessary electronics for reading, discriminating, and transmitting the detector signals. The MCMs are contained in a rectangular Rohacell plenum located beneath the C-cages. Besides housing the MCMs, the horizontal plenum also serves as a channel fix cooling air. Located at either end of an MVD half section are aluminum end plates that house, in part, feedthroughs for the electronics, adapters for coolant lines, and MVD mounting connectors. Located within each end plate are a total of twelve silicon pad detectors rind twelve corresponding MCMs to perform additional charged particle detection. Also located within each end plate is a motherboard that contains the electronics necessary to supply power and transmit information to all of the MCMs. Mounted on each motherboard are thirty-five low dropout voltage regulators (LDOs) that control the voltage to various MCM analog and digital components. The electronics in the MCMs and LDOs generate a relatively large amount of heat that must be removed from the MVD to provide reliable operating temperatures. In addition, the temperature within the MVD enclosure must be controlled properly to maximize and maintain the signal-to-noise ratios of the silicon strip detectors. In addition, because Rohacldl is a1 hygroscopic material, the humidity level within the enclosure must be control led to ensure proper positioning and alignment of the Rohacell Silicon Strip Detector \ Silicon Pad Detector End Plates Figure 1. Schematic diagram of the MVD showing the full set of silicon detector cage assemblies, horizontal MCM plenum, support structure, and end plates including motherboards, pad detectors, and radial MCM plenums. 3 C-cages and silicon detectors. Consequently, three different environmental control systems have been proposed and analyzed both experimentally and numerically [ 1, 2, 3, 41. Forced convection (sir systems were selected for cooling the MCMs (primary air cooling system) and controlling the enclosure environment (secondary air cooling system), but a forced convection liquid system was chosen for the LDO cooling strategy. The general layout of these three cooling systems is shown in Figure 2 . This report presents the detailed designs of the three environmental control systems as they currently stand. Each system is outlined in detail, including the desired operating characteristics i B identified by earlier conceptual and prototype testing, general system layout and performance descriptions, a list of components, vendors, and costs, and finally, a summary of the incorporated safety features. the PHENIX outriggers, and reasonable costs.