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Experimental and Theoretical Studies of Nucleation in Supercooled Liquid Silicon. Final Program Report

Description: The original objectives of the present program consisted of two specific nucleation-related research activities; (1) to provide a set of experimental data that will enable the quantitative examination of classical nucleation theory, and (2) to describe the phenomenon of nucleation by developing general expressions of nucleation that include both the thermal and athermal components and that correctly consider and incorporate the transient effects that arise from the nonstationary cluster distribution profile.
Date: April 29, 2004
Creator: Im, J.
Partner: UNT Libraries Government Documents Department

Helium Pot System for Maintaining Sample Temperature after Cryocooler Deactivation

Description: A system for maintaining a sample at a constant temperature below 10K after deactivating the cooling source is demonstrated. In this system, the cooling source is a GM cryocooler that is joined with the sample through an adaptor that consists of a helium pot and a resistive medium. Upon deactivating the cryocooler, the power applied to a heater located on the sample side of the resistive medium is decreased gradually to maintain an appropriate temperature rise across the resistive medium as the helium pot warms. The temperature is held constant in this manner without the use of solid or liquid cryogens and without mechanically disconnecting the sample from the cooler. Shutting off the cryocooler significantly reduces sample motion that results from vibration and expansion/contraction of the cold head housing. The reduction in motion permits certain processes that are very sensitive to sample position stability, but are not performed throughout the duration that the sample is at low-temperature. An apparatus was constructed to demonstrate this technique using a 4K GM cryocooler. Experimental and theoretical predictions indicate that when the helium pot is pressurized to the working pressure of the cryocooler's helium supply, a sample with continuous heat dissipation of several-hundred milliwatts can be maintained at 7K for several minutes when using an extension that increases the cold head length by less than 50%.
Date: January 26, 2005
Creator: Haid, B J
Partner: UNT Libraries Government Documents Department

How the Performance of a Superconducting Magnet is affected by theConnection between a small cooler and the Magnet

Description: As low temperature cryocoolers become more frequently used to cool superconducting magnets, it becomes increasingly apparent that the connection between the cooler and the magnet has an effect on the design and performance of the magnet. In general, the use of small coolers can be considered in two different temperature ranges; (1) from 3.8 to 4.8 K for magnet fabricated with LTS conductor and (2) from 18 to 35 K for magnets fabricated using HTS conductor. In general, both temperature ranges call for the use of a two-stage cooler. The best method for connecting a cooler to the magnet depends on a number of factors. The factors include: (1) whether the cooler must be used to cool down the magnet from room temperature, (2) whether the magnet must have one or more reservoirs of liquid cryogen to keep the magnet cold during a loss of cooling, and (3) constraints on the distance from the cooler cold heads and the magnet and its shield. Two methods for connecting low temperature coolers to superconducting magnets have been studied. The first method uses a cold strap to connect the cold heads directly to the loads. This method is commonly used for cryogen-free magnets. The second method uses a thermal siphon and liquid cryogens to make the connection between the load being cooled and the cold head. The two methods of transferring heat from the magnet to the cooler low temperature cold head are compared for the two temperature ranges given above.
Date: September 8, 2005
Creator: Green, Michael A.
Partner: UNT Libraries Government Documents Department


Description: A prototype liquid xenon {gamma}-camera has been constructed and preliminary results obtained. The sensitive volume is 7 c x 7 cm in area and 1.5 cm thick. Orthogonal coordinates for each interacting {gamma}-ray are provided by 24 anode wires 5 {micro} in diameter spaced 2.8 mm apart and 24 cathode strips.
Date: December 1, 1972
Creator: Zaklad, Haim; Derenzo, Stephen E.; Muller, Richard A. & Smits,Robert G.
Partner: UNT Libraries Government Documents Department

Operations aspects of the Fermilab Central Helium Liquefier Facility

Description: The Fermilab Central Helium Liquefier (CHL) facility consists of helium and nitrogen reliquefier plants operated 24 hours-a-day to supply LHe at 4.6{degrees}K and LN{sub 2} for the Fermilab Tevatron superconducting proton-antiproton collider ring and to recover warm return gases. Operating aspects of CHL, including different equipment and systems reliability, availability, maintenance experience, safety concerns, and economics aspects are discussed.
Date: March 1, 1995
Creator: Geynisman, M.G. & Makara, J.N.
Partner: UNT Libraries Government Documents Department

A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline

Description: A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.
Date: July 24, 2000
Creator: Rotela, E.; Yang, B.; Sharma, s. & Barcikowski, A.
Partner: UNT Libraries Government Documents Department

Activation of the liquid helium contamination during its passage in the Collider ring

Description: Radioactivation of possible contamination of the liquid helium trapped in the arcs of the Collider ring of the Superconducting Super Collider and transported by the liquid helium is estimated. This estimation is used to calculate the dose rate on the filter of the refrigerator plant located at the top of the shaft.
Date: January 1, 1994
Creator: Lopez, G.
Partner: UNT Libraries Government Documents Department

Electrical conductivity of fluid oxygen at high pressures

Description: Electrical conductivities of fluid oxygen were measured between 30 and 80 GPa at a few 1000 K. These conditions were achieved with a reverberating shock wave technique. The measured conductivities were several orders of magnitude lower than measured previously on the single shock Hugoniot because of lower temperatures achieved under shock reverberation. Extrapolation of these data suggests that the minimum metallic conductivity of a metal will be reached near 100 GPa.
Date: August 20, 1999
Creator: Bastea, M; Mitchell, A C & Nellis, W J
Partner: UNT Libraries Government Documents Department

Low Temperature and High Pressure Evaluation of Insulated Pressure Vessels for Cryogenic Hydrogen Storage

Description: Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen (LH{sub 2}) or ambient-temperature compressed hydrogen (CH{sub 2}). Insulated pressure vessels offer the advantages of liquid hydrogen tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for hydrogen liquefaction and reduced evaporative losses). The work described here is directed at verifying that commercially available pressure vessels can be safely used to store liquid hydrogen. The use of commercially available pressure vessels significantly reduces the cost and complexity of the insulated pressure vessel development effort. This paper describes a series of tests that have been done with aluminum-lined, fiber-wrapped vessels to evaluate the damage caused by low temperature operation. All analysis and experiments to date indicate that no significant damage has resulted. Required future tests are described that will prove that no technical barriers exist to the safe use of aluminum-fiber vessels at cryogenic temperatures.
Date: June 25, 2000
Creator: Aceves, S.; Martinez-Frias, J. & Garcia-Villazana, O.
Partner: UNT Libraries Government Documents Department

Progress on the MICE Liquid Absorber Cooling and CryogenicDistribution System

Description: This report describes the progress made on the design of the cryogenic cooling system for the liquid absorber for the international Muon Ionization Cooling Experiment (MICE). The absorber consists of a 20.7-liter vessel that contains liquid hydrogen (1.48 kg at 20.3 K) or liquid helium (2.59 kg at 4.2 K). The liquid cryogen vessel is located within the warm bore of the focusing magnet for the MICE. The purpose of the magnet is to provide a low beam beta region within the absorber. For safety reasons, the vacuum vessel for the hydrogen absorber is separated from the vacuum vessel for the superconducting magnet and the vacuum that surrounds the RF cavities or the detector. The absorber thin windows separate the liquid in the absorber from the absorber vacuum. The absorber vacuum vessel also has thin windows that separate the absorber vacuum space from adjacent vacuum spaces. Because the muon beam in MICE is of low intensity, there is no beam heating in the absorber. The absorber can use a single 4 K cooler to cool either liquid helium or liquid hydrogen within the absorber.
Date: May 13, 2005
Creator: Green, M.A.; Baynham, E.; Bradshaw, T.; Drumm, P.; Ivanyushenkov,Y.; Ishimoto, S. et al.
Partner: UNT Libraries Government Documents Department

The Cooling of a Liquid Absorber using a Small Cooler

Description: This report discusses the use of small cryogenic coolers for cooling the Muon Ionization Cooling Experiment (MICE) liquid cryogen absorbers. Since the absorber must be able contain liquid helium as well liquid hydrogen, the characteristics of the available 4.2 K coolers are used here. The issues associated with connecting two-stage coolers to liquid absorbers are discussed. The projected heat flows into an absorber and the cool-down of the absorbers using the cooler are presented. The warm-up of the absorber is discussed. Special hydrogen safety issues that may result from the use of a cooler on the absorbers are also discussed.
Date: August 24, 2005
Creator: Baynham, D.E.; Bradshaw, T.W.; Green, M.A.; Ishimoto, S. & Liggins, N.
Partner: UNT Libraries Government Documents Department

Does One Know the Properties of a MICE Solid or Liquid Absorber toBetter than 0.3 Percent?

Description: This report discusses the report discusses whether the MICE absorbers can be characterized to {+-}0.3 percent, so that one predict absorber ionization cooling within the absorber. This report shows that most solid absorbers can be characterized to much better than {+-}0.3 percent. The two issues that dominate the characterization of the liquid cryogen absorbers are the dimensions of the liquid in the vessel and the density of the cryogenic liquid. The thickness of the window also plays a role. This report will show that a liquid hydrogen absorber can be characterized to better than {+-}0.3 percent, but a liquid helium absorber cannot be characterized to better and {+-}1 percent.
Date: February 20, 2006
Creator: Green, Michael A. & Yang, Stephanie Q.
Partner: UNT Libraries Government Documents Department


Description: We present detailed measurements of the electron avalanche process in liquid Xenon. The measurements were made by using liquid-Xe-filled proportional chambers with anode diameters of 2.9, 3.5, and 5.0 {approx} to detect 279-keV y rays and measure the photopeak pulse height as a function of applied voltage. The use of uniform pulses of electrons enabled us to discriminate against secondary Townsend processes. We present a table of the first Townsend coefficient a as a function of electric field E; a typical value is {alpha} = (4.5 {+-} 0.3) x 10{sup 4} cm{sup -1} at E = 2 x 10{sup 6} V/cm. The electron avalanche occurs in liquid Xe at electric fields 26 times smaller than would be predicted using measurements made in gaseous Xe and E/{rho} density scaling.
Date: March 1, 1973
Creator: Derenzo, Stephen E.; Mast, Terry S.; Zaklad, Halm & Muller,Richard A.
Partner: UNT Libraries Government Documents Department


Description: A measurement of the spatial resolution of a liquid-argon filled chamber was performed with minimum ionizing particles. Two multi-strip chambers with 20-{micro}m strip spacing operating in the ionization mode were used in the experiment. They perform in accordance with a simple model based on electron diffusion. An estimate of the amount of electron diffusion in liquid argon is given and the time jitter distribution has a FWHM of 200 ns. Under best conditions, the spatial resolution is better than 20 {micro}m rms with an efficiency of nearly 100%.
Date: July 1, 1974
Creator: Derenzo, S.E.; Kirschbaum, A.R.; Eberhard, P.H.; Ross, R.R. & Sclmitz,F.T.
Partner: UNT Libraries Government Documents Department

The integration of liquid cryogen cooling and cryocoolers withsuperconducting electronic systems

Description: The need for cryogenic cooling has been a critical issuethat has kept superconducting electronic devices from reaching the marketplace. Even though the performance of many of the superconductingcircuits is superior to silicon electronics, the requirement forcryogenic cooling has put the superconducting devices at a seriousdisadvantage. This report discusses the process of refrigeratingsuperconducting devices with cryogenic liquids and small cryocoolers.Three types of cryocoolers are compared for vibration, efficiency, andreliability. The connection of a cryocooler to the load is discussed. Acomparison of using flexible copper straps to carry the heat load andusing heat pipe is shown. The type of instrumentation needed formonitoring and controlling the cooling is discussed.
Date: July 9, 2003
Creator: Green, Michael A.
Partner: UNT Libraries Government Documents Department

The CEBAF Cavity Cryostat

Description: The modular design of the linac cryostat system based on a cavity-pair is presented.Description of the cryogenic module consisting of four cavity-pairs is included.The methods of making a cavity-pair hermetic during cryostat assembly, introducing the waveguides, supporting the helium vessels and introducing instrumentation are presented.Also included are the methods of tuning the cavities, aligning them to exterior references and connecting cryogenic fluid circuits to adjacent modules and transfer lines.
Date: June 1, 1986
Creator: Biallas, George
Partner: UNT Libraries Government Documents Department

Superconducting radio-frequency modules test faciilty operating experience

Description: Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.
Date: July 1, 2007
Creator: Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A. et al.
Partner: UNT Libraries Government Documents Department


Description: One of the concerns in using compact superconducting magnets in the final focus region of the ILC is the influence of the cryogen flow on the vibration characteristics. As a first step towards characterizing such motion at nanometer levels, a project was undertaken at BNL to measure the vibrations in a spare RHIC quadrupole under cryogenic conditions. Given the constraints of cryogenic operation, and limited space available, it was decided to use a dual head laser Doppler vibrometer for this work. The performance of the laser vibrometer was tested in a series of room temperature tests and compared with results from Mark L4 geophones. The laser system was then used to measure the vibration of the cold mass of the quadrupole with respect to the outside warm enclosure. These measurements were carried out both with and without the flow of cold helium through the magnet. The results indicate only a minor increase in motion in the horizontal direction (where the cold mass is relatively free to move).
Date: October 17, 2005
Creator: JAIN, A.; AYDIN, S.; HE, P.; ANERELLA, M.; GANETIS, G.; HARRISON, M. et al.
Partner: UNT Libraries Government Documents Department

The CEBAF Superconducting Accelerator Cryomodule

Description: The design and fabrication of the cavity enclosure and calculation to support the 2*K operating temperature, and techniques for minimizing operating heat loads and cryostat loads are discussed. The integrating of the Cryogen fluid distribution system into the cavity cryostat will be presented.Integration of the cavity designing into cavity fabrication and maintenance program, with emphasis on system reliability and flexibility, is included.
Date: September 1, 1986
Creator: Rode, Claus & Biallas, George
Partner: UNT Libraries Government Documents Department