Liquid Helium Transfer Line Research Articles

Experiment of Low Heat Loss Liquid Helium Transfer line for NSRRC Cryogenic System

X-ray photon sources are used in research. During the past decade, the technology of the X-ray photon source has grown rapidly. To fulfil demands for an X-ray photon source in Taiwan, the Taiwan Photon Source (TPS), an electron accelerator with the energy of 3 GeV has been constructed with high brilliance and flux. To let the Superconducting radio frequency (SRF) system and cryogenic undulators in TPS to be under stable operation, the cryogenic system is therefore very important. Refrigerant of the TPS cryogenic system is liquid helium, to maintain LHe in its state, temperature has to be maintained below 4.5 K; however to evaporate 1 gram of liquid helium, only 20 Joule is needed. Therefore, the Multi-Channel Line (MCL) has been developed to prevent liquid helium vaporizing. Several mechanical parts have been designed to reduce heat loss and strengthen structure stability. In this paper, assembly of the transfer line and experimental results are discussed.

Characteristic research of pellet injection system in KSTAR

20 Hz pellet injection system was installed for improving a fueling system of KSTAR (Korea Superconducting Tokamak Advanced Research) in 2016. Several things of hardware such as a liquid helium transfer line, an extruder nozzle and an extension part of pellet guide tube are changed for 2017 campaign. For plasma experiments, the pellet injection system uses the smallest pellet (1.5 mm of length, 2 mm of diameter). The pellet velocity can be variable from 150 m/s to over 200 m/s by controlling of propellant gas pressure. The clear increase of plasma density observed during KSTAR experiments is also presented in this paper.

Operating parameters of liquid helium transfer lines used with continuous flow cryostats at low sample temperatures

Continuous flow cryostats are used to cool samples to a variable temperature level by evaporating a cryogen, e.g. liquid helium (LHe). For this purpose LHe is usually stored outside the cryostat in a mobile dewar and supplied through a transfer line. In general, the complete setup has to be characterised by the lowest possible consumption of LHe. Additionally, a minimum sample temperature can be favourable from an experimental point of view. The achievement of both requirements is determined by the respective cryostat design as well as by the transfer line. In the presented work operating data, e.g. the LHe consumption during cooldown and steady state, the minimum sample temperature, and the outlet quality are analysed to characterise the performance of a reference transfer line. In addition, an experimental transfer line with built-in pressure sensors has been commissioned to examine the pressure drop along the transfer line, too. During the tests LHe impurities occurred which restricted a steady operation.

Modeling and simulation of the CLS cryogenic system

This paper presents results pertaining to the numerical modeling of the cryogenic system at the Canadian Light Source. The cryogenic system consists of a cryostat that houses a Radio Frequency (RF) cavity used for boosting the energy of an electron beam. For consistent operation of the RF cavity, it must be kept immersed in liquid helium at a constant level with the pressure in the gas space maintained to an accuracy of ±1mbar. An improvement to the cryostat model suggested in [3] using control volumes is described. The model and numerical method developed for the liquid helium supply and gaseous helium return lines are validated using two different cases, viz., the liquid helium flow rate from the liquid helium transfer line and the gaseous helium flow rate from the cryostat for various heater power input settings. The numerical method described here is significantly more accurate, efficient, and flexible than that used in [1] based on an iterative bisection method.

A dynamic model of a liquid helium transfer line at the Canadian Light Source

This paper describes the creation and validation of a computer model of a liquid helium transfer line located at the Canadian Light Source (CLS) in Saskatoon, Canada. This line transfers liquid helium to a cryostat, which contains a superconducting radio frequency (RF) cavity, and requires precise pressure and level modulation to ensure proper RF control. A detailed mathematical model of the transfer line is created based on mass, momentum, and energy continuity along with pressure–volume–temperature relations. The model is discretized and solved, and model results are compared with experimental data taken from the actual cryostat at the CLS to validate of the simulation. The validated model is found to reasonably predict flow rates through the transfer line at the CLS from a process perspective.

LHC: The world's largest vacuum systems being operated at CERN

With the successful circulation of beams in the Large Hadron Collider (LHC), its vacuum system becomes the world's largest vacuum system under operation. This system is composed of 54 km of ultra high vacuum (UHV) for the two circulating beams and about 50 km of insulation vacuum around the cryogenic magnets and the liquid helium transfer lines (QRL). The LHC complex is completed by 7 km of high vacuum transfer lines for the injection of beams from the SPS and their dumping. Over the 54 km of UHV beam vacuum, 48 km are at cryogenic temperature (1.9 K), the remaining 6 km are at ambient temperature and use extensively non-evaporable getter (NEG) coatings, a technology that was born and industrialised at CERN. The cryogenic insulation vacuum systems, less demanding technically, impress by their size and volume: 50 km and 15,000 m 3. Once cooled at 1.9 K, the cryopumping allows pressure in the 10 −4 Pa range to be attained.

LHC World Largest Vacuum Systems Being Commissioned at CERN

The CERN Large Hadron Collider (LHC) with its 26.7 km of circumference and three different vacuum systems for the beams and insulation vacuum for magnets and liquid helium transfer lines, will have the world's largest vacuum system operating over a wide range of pressures and employing an impressive array of vacuum technologies. This system is composed by 54 km of UHV vacuum for the circulating beams and 50 km of insulation vacuum. Over the 54 km of UHV beam vacuum, 48 km of this are at cryogenic temperature (1.9 K). The remaining 6 km of beam vacuum containing the insertions for “cleaning” the proton beams, radiofrequency cavities for accelerating the protons as well as beam-monitoring equipment is at ambient temperature and uses non-evaporable getter (NEG) coatings. The noble gases and methane is pumped out by 780 ion pumps. Pressure readings are provided by 170 Bayard-Alpert gauges and 1084 gauges (Pirani and cold cathode Penning). The cryogenic insulation vacuums while technically less demanding, impress by their size (50 km) and volume (15000 m3). Once roughed using mechanical pumps, the vacuum relies on the cryopumping which allows reaching pressure in the 10-4 Pa range.

Superconducting cyclotron and its vacuum system

A large superconducting cyclotron is under construction at this Centre and will be used to accelerate heavy ion beams to energy up to 80 MeV/A for light heavy ions and about 10 MeV/A for medium mass heavy ions. The vacuum system for this accelerator has several different aspects. The main acceleration chamber will be evacuated to a level of about 10−7 torr using both turbo molecular pumps and specially designed cryopanels. The surfaces exposed to this ‘vacuum’ are mostly made of OFE copper. The cryogenic transfer lines, to cool the cryopanels, are of several meters in length and they pass through RF resonators extending below the magnet. The cryostat that will house the superconducting coils has an annular vacuum chamber, which is evacuated to a level of approximately 10−5 torr using a turbo molecular pump. Cryopumping action starts once the coils are cooled to low temperatures. A differential pumping is provided below the RF liner that encloses the pole tip of the main magnet. The space that is pumped in this case contains epoxy-potted trim coils wound around the pole tips. Crucial interlocks are provided between the differential vacuum and the acceleration chamber vacuum to avoid distortion of the RF liner, which is made of thin copper sheets. The other important vacuum system provides thermal insulation for the liquid helium transfer lines. In this paper a brief description of the superconducting cyclotron will be given. Details of various vacuum aspects of the accelerator and the logistics of their operation will be presented. Introduction of some of the improved equipment now available and improved techniques are also discussed.

Test results on systems developed for the SST-1 tokamak

The steady state superconducting tokamak (SST-1) is a large aspect ratio tokamak, configured to run double null diverted plasmas with significant elongation (κ) and triangularity (δ). Superconducting (SC) magnets are deployed for both the toroidal and poloidal field coils in SST-1. A NbTi based cable-in-conduit conductor (CICC) has been fabricated by M/S Hitachi Cables Ltd., Japan under specification and supervision of the Institute for Plasma Research (IPR). The suitability of this CICC for the SST-1 magnets has been validated through test carried out on a model coil wound from this CICC. Toroidal and poloidal SC magnets have been fabricated and factory acceptance tests have been performed. SC magnets require liquid helium (LHe) cooled current leads, electrical isolators at LHe temperature, superconducting bus bars and LHe transfer lines. Full scale prototypes of these have been developed and tested successfully. SC magnets will be cooled to 4.5 K by forced flow of supercritical helium through the CICC. A 1 kW grade liquefier/refrigerator has been installed and is in final stages of commissioning at IPR. SST-1 deploys a fully welded ultra high vacuum vessel, made up of 16 vessel sectors (VSs) having ports and 16 rings with -shaped cross-section. To establish the fabrication methodology for this, a fullscale prototype of the vessel with two VSs and three rings has been fabricated and tested successfully. Based on this the fabrication of the VSs and rings is in final stage of fabrication. Liquid nitrogen cooled radiation shield are deployed between the vacuum vessel and SC magnets as well as SC magnets and cryostat, to minimize the radiation losses at the SC magnets. SST-1 will have three different high power radio frequency systems to additionally heat and non-inductively drive plasma current to sustain the plasma in steady state for a duration of up to 1000 s. Ion cyclotron resonance frequency (ICRF) and electron cyclotron resonance frequency (ECRF) systems will primarily be used for heating the plasma while lower hybrid waves will be used for non inductive lower hybrid current drive (LHCD). A neutral beam injection with peak power of 0.8 MW with variable beam energy in range of 10–80 keV will be used as additional auxiliary heating system. A number of prototypes for various critical components have confirmed the fabrication methodology. The fabrication of most of the subsystems is nearing completion and many components have already been accepted on site. Erection and installation of the base of the mechanical structure has already been initiated in the SST hall. This paper reports on the results of the tests on various prototypes and actual components to be used on SST-1 for various subsystems.

A facility to test short superconducting accelerator magnets at Fermilab

The superconducting magnet R&D facility at Fermilab (Lab 2) has successfully tested superconducting dipole, quadrupole, and correction coil magnets less than 2 m in length for the Superconducting Super Collider (SSC) project and the Tevatron D0/B0 Low- beta Insertion. The authors describe the Lab 2 facility and the several upgrades which were developed to accomplish these successful test programs. Several improvements have been made to the facility that have greatly enhanced its magnet testing capabilities. Among the upgrades have been a new rotating coil and data acquisition system for measuring magnetic fields, a controlled flow liquid helium transfer line using an electronically actuated cryo valve, and stand-alone systems for measuring AC loss and training low current Tevatron correction coil packages. Tests are performed in vertical dewars of boiling liquid helium. >

Details of the Cryogenic System for the Cornell Superconducting R.f. Beam Tests

During the course of the most recent and past Superconducting R.F. beam tests in CESR, various techniques and concepts were developed in the implementation of the cryogenic system1,2,3,4. Some of these items will be described and will include, the long liquid helium transfer line, the liquid phase separation, the liquid nitrogen cooling system, feeding the wavequide heat exchangers, the JT valve, the temperature regulation and pumping system, the overall control and monitoring system, large and many indium seals, and mechanical details of the cryostat vessel.