Surge Recovery Techniques for the Tevatron Cold Compressors

Abstract

The Fermilab Tevatron cryogenic system utilizes high-speed centrifugal cold compressors, made by Ishikawajima-Harima Heavy Industries Co. Ltd. (IHI), for highenergy operations [1]. 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 discusses the different methods of surge recovery that have been employed. Data from tests performed at the Cryogenic Test Facility at Fermilab as well as actual Tevatron operational data were utilized. In order to aid in the determination of the surge region, a full mapping study was undertaken to characterize the entire pressure field of the cold compressor. These techniques were then implemented and tested at several locations in the Tevatron with some success.

Performance of cold compressors in a cooling system of an R&D superconducting coil cooled with subcooled helium

“…It is very important that these two cold compressors are operated stably and safely. If the cold compressors enter the surge region and then trips occur, there is every possibility of damaging equipments and reducing machine time for plasma experiments of LHD [7]. In the present study, the performance of cold compressors was investigated in the cooling system of the R&D coil for stable and safe operations, especially a surge limit of cold compressors.…”

Operation and Control of Helium Subcooling System of LHD Helical Coils During Change of Rotational Speed of Cold Compressors

“…The bath temperature is controlled by a heater in the bath, a bypass valve and a series of two centrifugal cold compressors with gas foil bearing. It is important to understand the characteristics of the cold compressors in the subcooling system for the purpose of the safe operation of the subcooling system during the change of the rotational speed of the cold compressors because the cold compressors should be operated within the appropriate operation area in order to prevent the cold compressors from the surge and the choke [7]- [9]. In the present study, the characteristics of the subcooling system with the cold compressors, especially the influence of the opening degree of the bypass valve, were investigated.…”