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Description: Brookhaven National Laboratory continues its multi-year program to improve the operational efficiency, reliability, and stability of the cryogenic system which also resulted in improved beam availability of the Relativistic Heavy Ion Collider (RHIC). This paper summarizes the work and changes made after each phase over the past four years to the present, as well as proposed future improvements. Power usage dropped from an initial 9.4 MW to the present 5.1 MW and is expected to drop below 5 MW after the completion of the remaining proposed improvements. The work proceeded in phases by balancing the Collider's schedule of operation, time required for the modifications and budget constraints. The main changes include process control, compressor oil removal and management, elimination of the use of cold compressors and two liquid helium storage tanks, insulation of the third liquid helium storage tank, compressor bypass flow reduction and the addition of a load turbine (Joule-Thompson expander) with associated heat exchangers at the cold end of the plant. Also, liquid helium pumps used for forced circulation of the sub-cooled helium through the magnet loops were eliminated by an accelerator supply flow reconfiguration. Planned future upgrades include the resizing of expanders 5 and 6 to increase their efficiencies.
Date: July 16, 2007
Partner: UNT Libraries Government Documents Department

Commissioning and operation of the CEBAF end station refrigeration system

Description: The CEBAF End Station Helium Refrigerator (ESR) System provides refrigeration at 80 K, 20 K and 4.5 K to three End Station experimental halls. The facility consists of a two stage helium screw compressor system, 4.5 K refrigerator, cryogen distribution valve box, and transfer lines to the individual experimental halls. The 4.5 K cold box and compressors were originally part of the ESCAR 1,500 W, 4 K refrigeration system at Lawrence Berkeley Laboratory which was first commissioned fin 1977. The compressors, 4.5 K cold box, and control system design were modified to adapt the plant for the requirements of the CEBAF experimental halls. Additional subsystems of cryogen distribution, transfer lines, warm gas management, and computer control interface were added. This paper describes the major plant subsystems, modifications, operational experiences and performance.
Date: August 1, 1996
Creator: Arenius, D.; Bevins, B.; Chronis, W.C.; Ganni, V.; Kashy, D.; Keesee, M. et al.
Partner: UNT Libraries Government Documents Department

Helium Sensitivity in Oxygen Deficiency Measurement Equipment

Description: Most accelerators in operation today use liquid helium based superconducting technology in some capacity. Many of these facilities also use fixed and portable oxygen monitors to detect an oxygen deficient atmosphere were the helium to be accidentally released. When released, helium can expand 800 times its liquid volume. Recent helium spill tests at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) uncovered a fundamental flaw in certain types of oxygen deficiency monitoring equipment. The ensuing investigation found that the problem is endemic to a class of electrochemical oxygen sensors used throughout both the research and industrial communities. This paper describes the results of the Jefferson Lab investigation and steps taken to date to both solve the problem and inform the safety community at large.
Date: June 1, 2001
Creator: Mahoney, Kelly; Hutton, Andrew; Robertson, H.; Arenius, D. & Curry, D.
Partner: UNT Libraries Government Documents Department

Procurement and commissioning of the CHL refrigerator at CEBAF

Description: The CEBAF Central Helium Liquefier (CHL) provides 2K refrigeration to the 338 superconducting niobium cavities in two 400 MeV linacs and one 45 MeV injector. The CHL consists of three first stage and three second stage compressors, a 4.5K cold box, a 2K cold box, liquid and gaseous helium storage, liquid nitrogen storage, and transfer lines. Figure 1 presents a block diagram of the CHL refrigerator. The system was designed to provide 4.8 kW of primary refrigeration at 2K, 12 kW of shield refrigeration at 45K for the linac cryomodules, and 10 g/s of liquid flow for the end stations. In April 1994, stable 2K operation of the previously uncommissioned cold compressors was achieved. The cold compressors are a cold vacuum pump with an inlet temperature of circa 3.0K. These compressors operate on magnetic bearing,s and therefore eliminate the possibility of contamination due to any air leaks into the system. Operational data and commissioning experience as they relate to the warm gaseous helium compressors, turbines, instrumentation and control, and the cold compressors are presented.
Date: August 1, 1996
Creator: Chronis, W.C.; Arenius, D.M.; Bevins, B.S.; Ganni, V.; Kashy, D.H.; Keesee, M.M. et al.
Partner: UNT Libraries Government Documents Department

Design of the FRIB Cryomodule

Description: An advanced, modular bottom-supported cryomodule design is described which is highly optimized for mass-production and efficient precision-assembly. The FRIB driver linac uses 4 types of superconducting resonators and 2 solenoid lengths which in turn require 7 individual cryomodule configurations. To meet alignment tolerances a precision-machined bolted cryomodule rail system is described. A novel, kinematic mounting system of the cold mass is introduced which allows for thermal contractions while preserving alignment. A first prototype will incorporate a wire position monitor for alignment verification. The cold alignment structure is supported by composite posts which also function as thermal isolators. The cryogenic system provides separate 2 K and 4.5 K liquid helium lines to cavities and solenoids. Details of the JT valves, heat exchanger, cool-down circuit and junction to cryogenic line will be provided. Transient cool-down was simulated for stresses and buckling failure. A 1100-O Aluminum shield is used as a thermal radiation shield. The paper also describes cryomodule interfaces with the linac tunnel, the RF input cables, and the cryogenic distribution system.
Date: July 1, 2012
Creator: Johnson, M J; Binkowski, J; Bricker, S; Casagrande, F; Fox, A D; Lang, B R et al.
Partner: UNT Libraries Government Documents Department