Barry Norris

Design and commissioning of Fermilab's vertical test stand for ILC SRF cavities

As part of its ILC program, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2 K, using a cryoplant that can supply LHe in excess of 20 g/sec and provide bath pumping capacity of 125 W at 2 K. The below-grade cryostat consists of a vacuum vessel and LHe vessel, equipped with magnetic shielding to reduce the ambient magnetic field to ≪10mG. Internal fixed and external movable radiation shielding ensures that exposure to personnel is minimzed. The facility features an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors.

New Cryogenic Controls for the Tevatron Low Temperature Upgrade

Fermilab’s Tevatron accelerator is undergoing a major cryogenic system upgrade. This upgrade project is necessary to lower coil temperature of the accelerator’s magnets by approximately 1K. The new system configuration utilizes a new valve box containing a 130 liter subcooling dewar and a Cold Compressor at each of the 24 satellite refrigerators. Each Cold Compressor pumps on a dewar to maintain the two-phase pressure at 50.7 kPa (0.5 atm) producing 3.56K helium in the dewar and magnet strings.

Status report on the tevatron lower temperature upgrade

Abstract A cryogenic upgrade has been completed for Fermilabs Tevatron acceleratorto lower the magnet temperature and increase the particle energy of the machine. Each satellite refrigerator uses a cold vapor compressor to pump on a subcooling dewar capable of lowering the magnet systems two-phase temperature to 3.56K. Larger wet expanders, subatmospheric modifications, and a new distributed control system were included in the design. A second Central Helium Liquefier with a 5400 liter/hour rated capacity was also brought on-line. Installation of the new lower temperature equipment and operating experiences during the Winter/Spring 1994 physics run including power tests are discussed.

First scientific application of the membrane cryostat technology

We report on the design, fabrication, performance and commissioning of the first membrane cryostat to be used for scientific application. The Long Baseline Neutrino Experiment (LBNE) has designed and fabricated a membrane cryostat prototype in collaboration with IHI Corporation (IHI). Original goals of the prototype are: to demonstrate the membrane cryostat technology in terms of thermal performance, feasibility for liquid argon, and leak tightness; to demonstrate that we can remove all the impurities from the vessel and achieve the purity requirements in a membrane cryostat without evacuation and using only a controlled gaseous argon purge; to demonstrate that we can achieve and maintain the purity requirements of the liquid argon during filling, purification, and maintenance mode using mole sieve and copper filters from the Liquid Argon Purity Demonstrator (LAPD) R&D project. The purity requirements of a large liquid argon detector such as LBNE are contaminants below 200 parts per trillion oxygen equiva...

The Liquid Hydrogen System for the MuCool Test Area

A new MuCool test area (MTA) is under construction at Fermi National Accelerator Laboratory. This facility will house a cryo-system composed of a liquid hydrogen absorber enclosed in a 5 Tesla magnet. The total volume of liquid hydrogen in the system is 25 liters. Helium gas at 14 K is provided by an in-house refrigerator and will sub-cool the hydrogen system to 17 K. Liquid hydrogen temperature in the absorber is chosen to satisfy the requirement of a density change smaller than +/- 2.5 %. To accommodate this goal and to remove the heat deposited by a beam, a pump will circulate liquid hydrogen at a rate of 450 g/s. The cooling loop was optimized with respect to the heat transport in liquid hydrogen and the pressure drop across the pump. Specific instrumentation will permit an intrinsically safe monitoring and control of the cryo-system. Safety issues are the main driver of the cryo-design.This paper describes the implementation of the liquid hydrogen system at MTA and the preliminary results of a finite element analysis used to size the LH2 absorber force-flow.

Cryogenic controls for Fermilab's SRF cavities and test facility

A new superconducting radio frequency (SRF) cavities test facility is now operational at Fermilabs Meson Detector Building (MDB). The Cryogenic Test Facility (CTF), located in a separate building 500 m away, supplies the facility with cryogens. The design incorporates ambient temperature pumping for superfluid helium production, as well as three 0.6 kW at 4.5 K refrigerators, five screw compressors, a helium purifier, helium and nitrogen inventory, cryogenic distribution system, and a variety of test cryostats.To control and monitor the vastly distributed cryogenic system, a flexible scheme has been developed. Both commercial and experimental physics tools are used. APACS+™, a process automation control system from Siemens-Moore, is at the heart of the design. APACS+™ allows engineers to configure an ever evolving test facility while maintaining control over the plant and distribution system. APACS+™ nodes at CTF and MDB are coupled by a fiber optic network. DirectLogic205 PLCs by KOYO® are used as the f...

Initial Performance of Upgraded Tevatron Cryogenic Systems

Fermilab began operating a re-designed satellite refrigerator systems in November 1993. Upgrades were installed to operate the Tevatron at a magnet temperature of 3.5 K, approximately 1K lower than the original design. Refrigerator upgrades included new valve boxes, larger reciprocating expanders, the installation of cold vapor compressors, new sub-atmospheric instrumentation and an entirely new distributed controls system. Cryogenic system reliability data for Colliding Physics Run 1B is presented emphasizing a failure analysis for each aspect of the upgrade. Comparison to data for Colliding Physics Run 1A (previous to upgrade) is presented to show the impact of a major system overhaul. New operational problems and their solutions are presented in detail.

The LBNE 35 Ton Prototype Cryostat

The 35 Ton Prototype Cryostat was built to demonstrate that a commercial membrane-cryostat technology could achieve the performance necessary for the operation of a large multi-kiloton liquid argon detector for the Long-Baseline Neutrino Experiment (LBNE). A concluded Phase 1 run has confirmed both the thermal stability and leak tightness of this technology that is necessary to achieve extremely pure liquid argon. Measured electron drift times in excess of 2.5 ms infer impurity concentrations in the liquid argon of less than 140 ppt (O2 equivalent). These purity levels were attained and held for sustained periods. Details of the cryostat operation, measurements, and analysis of the Phase 1 run are given. A future Phase 2 run, that will include a reduced-scale LBNE-style Time Projection Chamber with integral photon detectors is briefly described.

Cryogenics for the MuCool Test Area (MTA)

MuCool Test Area (MTA) is a complex of buildings at Fermi National Accelerator Laboratory, which are dedicated to operate components of a cooling cell to be used for Muon Collider and Neutrino Factory R&D. The long-term goal of this facility is to test ionization cooling principles by operating a 25-liter liquid hydrogen (LH{sub 2}) absorber embedded in a 5 Tesla superconducting solenoid magnet. The MTA solenoid magnet will be used with RF cavities exposed to a high intensity beam. Cryogens used at the MTA include LHe, LN{sub 2} and LH{sub 2}. The latter dictates stringent system design for hazardous locations. The cryogenic plant is a modified Tevatron refrigerator based on the Claude cycle. The implementation of an in-house refrigerator system and two 300 kilowatt screw compressors is under development. The helium refrigeration capacity is 500 W at 14 K. In addition the MTA solenoid magnet will be batch-filled with LHe every 2 days using the same cryo-plant. This paper reviews cryogenic systems used to support the Muon Collider and Neutrino Factory R&D programs and emphasizes the feasibility of handling cryogenic equipment at MTA in a safe manner.

Tevatron Quench Pressure Measurement

The upcoming lower temperature/higher energy upgrade to the Fermilab Tevatron accelerator has raised questions concerning peak pressures during magnet system quenches. An experiment was performed to measure the pressure versus time at various quench energies in several devices in the Tevatron. A smaller study also looked at the temperature and mass flow rate versus time.