J. Theilacker

An Investigation into Flow Regimes for Two-Phase Helium Flow·

The Tevatron accelerator at Fermilab incorporates long two-phase helium passages. During magnet design, the generalized flow map of Baker was used to predict homogeneous flow. Longer than expected magnet time constants led to this investigation. The importance of predicting the flow regime has been amplified with the advent of non-horizontal accelerator designs.

Design and testing of the New Muon Lab cryogenic system at Fermilab

Fermi National Accelerator Laboratory is constructing a superconducting 1.3 GHz cryomodule test facility located at the New Muon Lab building. The facility will be used for testing and validating cryomodule designs as well as support systems. For the initial phase of the project, a single Type III plus 1.3 GHz cryomodule will be cooled and tested using a single Tevatron style standalone refrigerator. Subsequent phases involve testing as many as two full RF units consisting of up to six 1.3 GHz cryomodules with the addition of a new cryogenic plant. The cryogenic infrastructure consists of the refrigerator system, cryogenic distribution system as well as an ambient temperature pumping system to achieve 2 K operations with supporting purification systems. A discussion of the available capacity for the various phases versus the proposed heat loads is included as well as commissioning results and testing schedule. This paper describes the plans, status and challenges of this initial phase of the New Muon Lab cryogenic system.

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.

Upgrade of the Tevatron cryogenic system

Fermilabs superconducting Tevatron accelerator has reached its tenth year of operation. This year, three significant upgrades to the cryogenic system will become operational; a second central helium liquefier, a Tevatron satellite refrigerator lower temperature upgrade, and a satellite refrigerator controls system upgrade.

A Miniature Wet Turboexpander

A miniature turboexpander capable of operating with the exhaust conditions down to sub critical temperatures and pressures has been developed. The expander shaft is supported in pressurized gas bearings and has a 4.76 mm turbine rotor at the cold end and a 12.7 mm brake compressor at the warm end. The expander has a design speed of 384,000 rpm and a design cooling capacity of 444 watts. A prototype machine has been built and tested in one of the satellite refrigerators at Fermi National Accelerator Laboratory. The gas bearings have demonstrated robust operation under severe system transients, including operation with the turbine exhaust in the two-phase flow regime. This paper describes the machine and the results of the testing.

SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE

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 the SRF R&D needs. The projects first stage 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 Meson Detector Building (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.

Tevatron cold compressor operating experience

Abstract This year saw the completion of three accelerator improvement projects pertaining to the Tevatron cryogenic system. The projects result in the ability to operate the Tevatron at lower temperature, and thus higher energy, through the use of cold compressors. In January of 1994, the Tevatron operated at an energy of 975 GeV for the first time. Although this is a modest increase in energy, the discovery potential for the Top quark is considerably improved. This paper describes the operational experiences during the commissioning of the cold compressors in the Tevatron satellite refrigeration system.

ILC cryogenic systems reference design

A Global Design Effort (GDE) began in 2005 to study a TeV scale electron-positron linear accelerator based on superconducting radio-frequency (RF) technology, called the International Linear Collider (ILC). In early 2007, the design effort culminated in a reference design for the ILC, closely based on the earlier TESLA design. The ILC will consist of two 250 GeV linacs, which provide positron-electron collisions for high energy physics research. The particle beams will be accelerated to their final energy in superconducting niobium RF cavities operating at 2 kelvin. At a length of about 12 km each, the main linacs will be the largest cryogenic systems in the ILC. Positron and electron sources, damping rings, and beam delivery systems will also have a large number and variety of other superconducting RF cavities and magnets, which require cooling at liquid helium temperatures. Ten large cryogenic plants with 2 kelvin refrigeration are envisioned to cool the main linacs and the electron and positron sources. Three smaller cryogenic plants will cool the damping rings and beam delivery system components predominately at 4.5 K. This paper describes the cryogenic systems concepts for the ILC.

Surge recovery techniques for the Tevatron cold compressors

The Fermilab Tevatron cryogenic system utilizes high‐speed centrifugal cold compressors, made by Ishikawajima‐Harima Heavy Industries Co. Ltd. (IHI), for high‐energy operations. The compressor is designed to pump 60 g/s of 3.6 K saturated helium vapor at a pressure ratio of 2.8, with an off‐design range of 40 to 70 g/s and operating speeds between 40 and 95 krpm. Since initial commissioning in 1993, Tevatron transient conditions such as quench recovery have led to multiple‐location machine trips as a result of the cold compressors entering the surge regime. Historically, compressors operating at lower inlet pressures and higher speeds have been especially susceptible to these machine trips and it was not uncommon to have multiple compressor trips during large multiple‐house quenches. In order to cope with these events and limit accelerator down time, surge recovery techniques have been implemented in an attempt to prevent the compressors from tripping once the machine entered this surge regime. This paper...

Cryogenic system for the Cryomodule Test Facility at Fermilab

This paper provides an overview of the current progress and near-future plans for the cryogenic system at the new Cryomodule Test Facility (CMTF) at Fermilab, which includes the helium compressors, refrigerators, warm vacuum compressors, gas and liquid storage, and a distribution system. CMTF will house the Project X Injector Experiment (PXIE), which is the front end of the proposed Project X. PXIE includes one 162.5 MHz half wave resonator (HWR) cryomodule and one 325 MHz single spoke resonator (SSR) cryomodule. Both cryomodules contain superconducting radio-frequency (SRF) cavities and superconducting magnets operated at 2.0 K. CMTF will also support the Advanced Superconducting Test Accelerator (ASTA), which is located in the adjacent New Muon Lab (NML) building. A cryomodule test stand (CMTS1) located at CMTF will be used to test 1.3 GHz cryomodules before they are installed in the ASTA cryomodule string. A liquid helium pump and transfer line will be used to provide supplemental liquid helium to ASTA.