Liquid Helium Cryogenic System Research Articles

Thermal performance analysis and cryogenic experimental measurements of the 166.6 MHz cavity cryomodule for the High Energy Photon Source

The 166.6 MHz radio frequency (RF) system with five superconducting HOM damped cavities is adopted to accelerate the 200 mA electron beam in the storage ring of the High Energy Photon Source (HEPS). The 166.6 MHz cavity cryomodules have been designed, constructed and horizontal tested at IHEP since the beginning of 2019. The thermal performances of the cryomodule are analyzed by numerical simulations which take into account the main contributors to the static heat loads at various temperature levels. The experiment investigations including the cool down, operating with RF power and static heat load measurements of the cryomodule are performed in the liquid helium cryogenic system. The calculated static heat loads have been compared with the experimental measurements, and the results show that deviations between the calculated heat loads and available experimental measurements at 4.2 K temperature level are within a small range, which indicates that thermal simulations are accurate. The detailed operating parameters in the cryogenic environment are reported.

Design and test of a liquid helium cryostat with automatic level control for cooling a superconductive single-flux-quantum circuit chip

A small-scale liquid helium cryogenic system has been designed for cooling the superconductive single-flux-quantum circuits. With a special double inner cylinders structure and a PID control system, automaticcontrolof the liquid helium level could be achieved. The cooling capacity recovered structure was added to the cold shield of the system in order to reduce the heat leakage of the system. Besides, A special composite magnetic shielding structure was designed to ensure the circuits working in an extremely low magnetic environment. Experiments were conducted to test the thermal performance and the magnetic shielding efficiency of the liquid helium cryogenic system. The results show that the storage time of the liquid helium is about 2 days with about 110 coaxial cables and the magnetic flux density at the chip location is below 5 nT at the temperature of 4.2 K.

Design and test of a liquid helium cryogenic system for the cooling of a superconductive single-flux-quantum circuit chip

A small-scale mobile liquid helium cryogenic system has been designed for the cooling of a superconductive single-flux-quantum circuit. The system includes a unique double inner cylinder, a “zigzag” cold energy recovery structure for the coaxial line and a special magnetic shielding structure. Experiments were conducted to test the thermal performance and the magnetic shielding efficiency of the liquid helium cryogenic system. The results show that the storage time of the liquid helium is about 5 h with a heat load of 2 W and the magnetic flux density at the chip location is about 5 nT at the temperature of 4.2 K.

Thermal study of a cryogen-less MgB2 cavity

Recent efforts towards production of high-quality magnesium diboride (MgB2) coatings have raised the possibility of producing usable accelerating cavities. Work continues to reliably produce films of sufficient quality over the large, complex surface area of an accelerating cavity, but this technology would open many interesting technical opportunities. One of these is to replace the traditionally required liquid helium cryogenic systems with a dry system based on cryocoolers. This is made possible by the much higher Tc of MgB2, allowing operation closer to 30K where cryocooler efficiency becomes competitive with alternative systems. This removes the need for pressure vessels in the cryomodule as well as internal distribution systems, greatly simplifying cryomodule design and fabrication. The lack of uniform cooling over the cavity surface, however, complicates behavior by coupling RF losses, heat leak, and cooling design in a way not seen in traditional SRF cavities. In this paper, these complexities are explored, including realistic cryocooler performance, temperature dependant RF losses, and standard thermal management challenges.

Status and Overview of Superconducting Radioactive Isotope Beam Separator BigRIPS at RIKEN

Superconducting triplet quadrupoles (STQs) with large apertures and high field-gradients are employed for the in-flight radioactive-isotope (RI) beam separator BigRIPS at RIKEN. It consists of fourteen STQs and six room-temperature dipoles. The use of the STQs makes it possible to achieve important features of the BigRIPS separator: large acceptances and a large magnetic rigidity, allowing efficient production of RI beams. The BigRIPS separator is presently under construction and assembly as a major installation in the RIKEN RI-beam factory project, and the commissioning is scheduled in early 2007. In this paper we present the status and overview of the BigRIPS separator, emphasizing the STQs and their liquid-helium cryogenic systems.

Temperature control of a liquid helium propulsion system

Two spacecraft, gravity probe B (GP-B) and the satellite test of the equivalence principle (STEP), incorporating onboard liquid helium cryogenic systems are scheduled to fly around the turn of the century. Effective propulsion systems can be implemented for these spacecraft by directing the helium gas which boils off from the cryogenic systems in specific directions through a set of thrusters. Due to extensive development and testing work, the ultra low flow rate helium thrusters for such a propulsion system are now considered proven technology. This article is concerned with implementing these thrusters into an effective overall propulsion system. A thermodynamic model relating the temperature, pressure, and flow rate of the propulsion system is derived. Based on this model a controller is developed which regulates the liquid helium supply temperature and pressure by varying the net heliqm mass flow rate through the thrusters. We show how the net mass flow rate can be controlled independently from the desired output thrust. The manifold pressure upstream of the thrusters is shown to remain remarkably stable even with fairly large flow rate variations. Using the GP-B spacecraft as an example we conclude that it is feasible to build a liquid helium based propulsion system with a very stable supply temperature and pressure.

The continuous electron beam accelerator facility

On February 13, 1987, construction started on the Continuous Electron Beam Accelerator Facility - a 4 GeV, 200μA, continuous beam, electron accelerator facility designed for nuclear physics research. The machine has a racetrack configuration with two antiparallel, 500 MeV, superconducting linae segments connected by beam lines to allow four passes of recirculation. The accelerating structure consists of 1500 MHz, five-cell niobium cavities developed at Cornell University. A liquid helium cryogenic system cools the cavities to an operating temperature of 2 K. Beam extraction after any three of the four passes allows simultaneous delivery of up to three beams of independently variable currents and different, but correlated, energies to the three experimental areas. Beam breakup thresholds exceed the design current by nearly two orders of magnitude. Project completion and the start of physics operations are scheduled fo. 1993. The total estimated cost is $255 million.

Design of a vertical wiggler with superconducting coils

A vertical wiggler has been designed, which will be installed in the 2.5 GeV electron storage ring under construction at KEK-PF. The wiggler magnet with superconducting coils produces magnetic fields of 6 T and wiggles electron beams in a vertical plane. Synchrotronn radiation generated by the wiggler has a critical wavelength of 0.5 Å and has an electric field-vector in the vertical direction, which is very important for precise experiments in various fields of the material sciences. The wiggler consists of three pairs of superconducting coils, an iron magnetic shield, a beam pipe and a liquid helium cryogenic system and is contained in a vacuum vessel which can move up and down together with the wiggler. During the injection time, the vessel is pushed up, so that electron beams with a large spatial spread go through the lower part of the beam pipe, where the aperture of the beam pipe is large enough. After the beam size becomes small due to radiation damping, the vessel is pushed down so that the electron beams go through the narrow gap of the wiggler magnet. Using the iron magnetic shield with iron pole pieces, the ratio between the magnetic field in the gap and the maximum field on the superconductor coils is reduced to 1.1.

Masers for Radar Systems Applications

This paper is intended to provide the systems engineer with a practical introduction to the use of solid-state maser amplifiers in radars. Various environmental problems involved in the successful application of masers are discussed. An elementary survey of reflection-cavity and traveling-wave masers, together with some experimental results are presented. Another section treats the problem of saturation in masers and discusses some of the methods available for protecting masers from the TR leak-through pulses in radar. Progress made in the development of open-and closed-cycle liquid helium cryogenic systems suitable for masers is described. The authors' personal evaluations of the state of the art of ruby masers and closed-cycle helium refrigerators are given in appendixes.