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Trace impurity analyzer

Description: The desirability for long-term reliability of large scale helium refrigerator systems used on superconducting accelerator magnets has necessitated detection of impurities to levels of a few ppM. An analyzer that measures trace impurity levels of condensable contaminants in concentrations of less than a ppM in 15 atm of He is described. The instrument makes use of the desorption temperature at an indicated pressure of the various impurities to determine the type of contaminant. The pressure rise at that temperature yields a measure of the contaminant level of the impurity. A LN/sub 2/ cryogenic charcoal trap is also employed to measure air impurities (nitrogen and oxygen) to obtain the full range of contaminant possibilities. The results of this detector which will be in use on the research and development helium refrigerator of the ISABELLE First-Cell is described.
Date: January 1, 1979
Creator: Schneider, W.J. & Edwards, D. Jr.
Partner: UNT Libraries Government Documents Department

Heat-load measurement of prototype cryogenic magnets and leads for the ISABELLE project

Description: A major feature in the cryogenic system development program for ISABELLE is the measurement of the heat loads of prototypical hardware. In particular, superconducting magnet assemblies, magnet power leads and magnet power lead vessels have been measured. In each of these cases it has been possible to build equipment which has a heat load equal to or less than the allowance for it in the heat load budget.
Date: January 1, 1981
Creator: Werner, A.P.; Brown, D.P. & Schneider, W.J.
Partner: UNT Libraries Government Documents Department

Cryogenic distribution system for the first cell

Description: The ISABELLE refrigeration system utilizes compressed liquid helium to supply refrigeration to nearly 1100 superconducting bending and focusing magnets. These magnets steer the proton orbits of the accelerator and are arranged into two interlocking rings. The cryogenic distribution system that is used to transmit the helium cooling from the central refrigerator to the superconducting magnets makes up a substantial portion (34%) of the total heat load that the refrigerator must be capable of supplying. This piping system has been designed to minimize the heat input into the refrigeration system. The design and test results of the distribution system in use on the ISABELLE prototype, the first cell are described.
Date: January 1, 1980
Creator: Brown, D P & Schneider, W J
Partner: UNT Libraries Government Documents Department

Vertical-channel free convection with a power-law fluid

Description: A finite-difference solution is presented of the velocity and temperature fields for the flow of an Ostwald-de-Waele (power law) fluid between two vertical isothermal parallel plates under the influence of free convection. Two quantities are of particular interest: the total heat transferred from the plates and the average velocity between the plates. Although these quantities can be presented in a dimensionless manner as related to the generalized Grashof and Prandtl numbers, there is an important difference compared to the similar problem involving Newtonian fluids. In the present case, the generalized Prandtl number is not a fluid property but contains a geometric factor and thus the geometry of the system must be specified before the Prandtl number is fixed. The results and the manner in which they can be used are illustrated by a numerical example.
Date: January 1, 1982
Creator: Irvine, T.F. Jr.; Wu, K.C. & Schneider, W.J.
Partner: UNT Libraries Government Documents Department

MAGCOOL: the production cooling facility for ISABELLE magnets

Description: The ISABELLE proton accelerator uses over one thousand superconducting magnets to guide the particle beams in two circular rings, 3.8 km in circumference. Prior to their installation in the tunnel all magnets must be tested and measured at their 3.8 K operating temperature. This paper describes the refrigeration system, called MAGCOOL, to accomplish this task.
Date: January 1, 1981
Creator: Bamberger, J.A.; Afrashteh, M.; Brown, D.P.; Schneider, W.J.; Sondericker, J.H. & Wu, K.C.
Partner: UNT Libraries Government Documents Department

Helium Refrigeration System for BNL Colliding-Beam Accelerator

Description: A Helium Refrigeration System which will supply the cooling required for the Colliding Beam Accelerator at Brookhaven National Laboratory is under construction. Testing of the compressor system is scheduled for late 1983 and will be followed by refrigerator acceptance tests in 1984. The refrigerator has a design capacity of 24.8 kW at a temperature level near 4% while simultaneously producing 55 kW for heat shield loads at 55K. When completed, the helium refrigerator will be the world's largest. Twenty-five oil-injected screw compressors with an installed total of 23,250 horsepower will supply the gas required. One of the unique features of the cycle is the application of three centrifugal compressors used at liquid helium temperature to produce the low temperatures (2.5K) and high flow rates (4154 g/s) required for this service.
Date: January 1, 1983
Creator: Brown, D.P.; Farah, Y.; Gibbs, R.J.; Schlafke, A.P.; Schneider, W.J.; Sondericker, J.H. et al.
Partner: UNT Libraries Government Documents Department

An R.F. Input Coupler System for the CEBAF Energy Upgrade Cryomodule

Description: Long term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. Thus an upgraded cryomodule to more than double the present voltage is under development. A new waveguide coupler system has been designed and prototypes are currently being developed. This coupler, unlike the original, has a nominal Q{_}ext of 2.1 x 10{sup 7}, reduced sensitivity of Q{_}ext to mechanical deformation, reduced field asymmetry within the beam envelope, freedom from window arcing with a single window at 300 K, and is capable of transmitting 6kW CW both traveling wave and in full reflection.
Date: March 1, 1999
Creator: Delayen, J.R.; Doolittle, L.R.; Hiatt, T.; Hogan, J.; Mammosser, J.; Phillips, L. et al.
Partner: UNT Libraries Government Documents Department

Design of the SNS Cavity Support Structure

Description: The Spallation Neutron Source facility utilizes a superconducting linac to provide a l-GeV H- beam with an average power of 2MW. A critical part of the accelerator structure is the superconducting radio frequency (SRF) niobium cavities which are housed in a titanium liquid helium pressure vessel. These vessels maintain the operating temperature of 2.1 Kelvin while facilitating the mechanical support, tuning and alignment of the SRF cavities. The design, fabrication and operation of the superconducting support structure will be presented with an emphasis on the design criteria as they pertain to the operation of the cavity. These criteria will be discussed with respect to the titanium liquid helium pressure vessels,higher order mode couplers, fundamental power coupler, field probe and tuning requirements.
Date: June 1, 2001
Creator: Hogan, J.; Ciovati, G.; Machie, D.; Pitts, J.; Preble, J.; Schneider, W.J. et al.
Partner: UNT Libraries Government Documents Department

Design of 24. 8-kW, 3. 8 K cryogenic system for ISABELLE

Description: ISABELLE will consist of two proton accelerator/storage rings in a common tunnel. There will be 1084 superconducting magnets installed in the 3.8 km circumference tunnel. The protons will be accelerated to an energy of 400 GeV in each ring and stored for 24 hours. The two beams are counter-rotating and intersect at six places around the ring. The particles which emerge from proton interactions at these intersecting points are studied using various types of detectors.
Date: January 1, 1981
Creator: Brown, D.P.; Afrashteh, M.; Bamberger, J.A.; Fresco, A.; Schlafke, A.P.; Schneider, W.J. et al.
Partner: UNT Libraries Government Documents Department

First cell magnet system tests

Description: The ISABELLE refrigeration system utilizes compressed liquid helium to supply refrigeration to nearly 1100 superconducting bending and focusing magnets. These magnets steer the proton orbits of the accelerator and are arranged into two interlocking rings. The total heat load that the refrigerator must provide is made up of the heat load of the magnets, magnet leads and vessels and the interconnecting piping to the refrigerator. The design and test results of the magnet system during various operating conditions in use on the ISABELLE prototype, the First Cell, are described.
Date: January 1, 1981
Creator: Schneider, W.J.; Brown, D.P.; Briggs, J.J.; Foerster, C.L.; Halama, H.J.; Schlafke, A.P. et al.
Partner: UNT Libraries Government Documents Department

Jefferson Lab CEBAF energy upgrade plans

Description: This paper presents interim conceptual plans for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility to extend Jefferson Lab's world leadership in nuclear physics research. The CEBAF accelerator was designed in the mid-1980's to provide beams of electrons at an energy of 4 GeV (billion electron volts) for use as probes of the atom's nucleus in CEBAF's three experiment halls. As of early 1999, the accelerator exceeds its design energy by routinely operating above 5.5 GeV. When upgraded, it will provide 11 GeV electron beams for studies in existing experimental halls and 12 GeV electrons to generate photon beams for related but qualitatively different nuclear studies in a new Hall D.
Date: August 1, 1999
Creator: Rode, C. H.; Benesch, J.; Chao, Y.; Delayen, J. R.; Karn, J.; Mammosser, J. et al.
Partner: UNT Libraries Government Documents Department

Testing Procedures and Results of the Prototype Fundamental Power Coupler for the Spallation Neutron Source

Description: High-power RF testing with peak power in excess of 500 kW has been performed on prototype Fundamental Power Couplers (FPC) for the Spallation Neutron Source superconducting (SNS) cavities. The testing followed the development of procedures for cleaning, assembling and preparing the FPC for installation in the test stand. The qualification of the couplers has occurred for the time being only in a limited set of conditions (travelling wave, 20 pps) as the available RF system and control instrumentation are under improvement.
Date: June 1, 2001
Creator: Stirbet, M.; Campisi, I.E.; Daly, E.F.; Davis, G.K.; Drury, M.; Kneisel, P. et al.
Partner: UNT Libraries Government Documents Department

Advances in DC photocathode electron guns

Description: At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughout. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, the authors will review recent results and discuss implications for future photocathode guns.
Date: July 1, 1998
Creator: Dunham, Bruce M.; Heartmann, P.; Kazimi, Reza; Liu, Hongxiu; Poelker, B. M.; Price, J. S. 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

A load-locked gun for the Jefferson Lab polarized injector

Description: Construction is underway at Jefferson Lab on a load-locked polarized electron source. The design incorporates all of the essential features of the existing non load-locked gun and improves on the designs of existing load-locked guns operating at other labs. When complete, the authors expect the new load-locked gun to enhance the versatility of the JLAB polarized injector.
Date: April 1, 1999
Creator: Schneider, W. J.; Adderley, P.; Clark, J.; Day, A.; Dunham, B.; Hansknecht, J. et al.
Partner: UNT Libraries Government Documents Department