Cryogenic Supply Research Articles

Cryopump design for the ITER heating neutral beam injector

Forschungszentrum Karlsruhe (FZK) is developing cryopumps for ITER heating neutral beam injectors (NBIs). The system is characterized by high gas flows coming from different sources against which the cryopumps must maintain a pressure between 10−2 and 10−3 Pa in the beam line (BL) vessel. The design of 2001 had proposed a cylindrical vessel with a cylindrical cryopump inside with a maximized pumping area to cover the vacuum requirements. In this design the only access to all BL components was through the beam source vessel, making it necessary to dismantle the beam source for all maintenance issues on the BL. During the ongoing design investigations on the heating NBI, it was decided in 2006 to use a rectangular vessel for the BL with a top access to improve the maintenance. This necessitated a full redesign of the cryopumps. In the new geometry of the BL vessel the size of the cryopump is limited to a flat rectangular geometry of 8 m length, 2.75 m height and 0.5 m depth. To cover the vacuum requirements two cryopumps of this size must be included for each injector. Gas profile calculations using the detailed BL geometry have been used to detect the needed gas capture probability of the pumping surface to guarantee the beam pulse operation. In this paper we give an outline of the working scope done to come up with a cryopump design covering the needs of the ITER NBI. The design of the novel cryopump and the heat load calculations for the different operation scenarios will be discussed. It is shown that the cryopump for the ITER heating NBI covers all vacuum requirements and it is fully adapted to the ITER cryogenic supply.

The oxycoal process with cryogenic oxygen supply

Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO2 emissions are among the highest when burning coal for power generation. Therefore, the capture of CO2 from power plants may contribute significantly in reducing global CO2 emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO2 concentrations. After further conditioning, the highly concentrated CO2 is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO2-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.

Commissioning of the Prototype Test Facility for Rapidly-Cycling Superconducting Magnets for FAIR

For testing rapidly-cycled superconducting magnets in the framework of the FAIR project (Facility for Antiprotons and Ion Research) a test facility was set up at GSI to test model and prototype superconducting magnets for different machines (SIS100, SIS300, Super-FRS). We are able to perform the following magnet tests: quench training, magnetic measurements, measurements of AC losses (calorimetric and V-I methods), temperature distributions in the magnet, and long-term stability tests. The forced-flow and bath-cooled scheme can be applied for the superconducting magnets. The facility consists of the following components: a refrigerator (400 W at 4 K); a distribution box for different cooling schemes (supercritical and two-phase flow); 2 feed-boxes providing electrical and cryogenic supply for the magnets; an all-purpose horizontal magnet cryostat which can be used for all kinds of different magnets (max. 3 m length and 0.8 m diameter); a power converter (11 kA) including the quench protection system; a quench detection system adapted from the LHC-series test facilities. The results of the AC loss measurements and the quench training for the first tested superconducting magnet are presented.

Diagnosis of cryogenic pump-motor systems using vibration and current signature analysis

In general, to send out natural gas via a pipeline network across the nation in LNG terminal, high-pressure cryogenic pump supply highly compressed LNG to high-pressure vaporization facilities. The Number of cryogenic pumps determined the send-out amount in LNG receiving terminal. So it is main equipment at LNG production process and should be maintained on best conditions. In this paper, to find out the cause of high vibration at cryogenic pumps-motor system in LNG terminal, vibration spectrum analysis and motor current signature analysis have been performed together. Through the analysis, motor rotor bar problems are estimated by the vibration analysis and confirmed by the current analysis. So, it is demonstrated through the case study in this paper, how performing vibration analysis and current signature analysis together can reliable diagnosis rotor bar problems in pump-motor system.

Assembly Concept and Technology of the ATLAS Barrel Toroid

The ATLAS detector for the LHC collider at CERN requires a large superconducting Barrel Toroid (BT) with overall dimensions of 25 m length, 22 m diameter which is installed in the ATLAS cavern 100 m underground. The Barrel Toroid provides the magnetic field for the muon detector. The toroid is assembled from 8 flat race track coils of dimensions 25 m times 5 m. Following the on-surface acceptance test of the 8 BT coils, they are successively inserted in the underground cavern and assembled as a full toroid by using 16 supporting rings of struts that link the 8 coils to form a rigid and stable structure. The total mass of the toroid is 850 t. Particular issues are that the axis of the toroid has to be horizontal and the final shape of the toroid cylindrical with a tolerance of +/-10 mm with respect to an overall system diameter of 22 m. The desired shape of the toroid can only be controlled by installing the 8 coils in calculated positions in space (forming an elliptic shaped structure), and by linking them using bolted struts linking the coils. The final release of the structure is done under its self weight hydraulically. This required very large tooling essentially to support all the 8 coils in space in a nearly stress free condition until the toroid supporting rings have been closed. The theoretical positions are found by performing detailed 3-D Finite Element Calculations that predict the shape of the toroid under its operational load. The assembly of this huge toroid is unique and no experience basis exists. This paper presents the concept and technology required for the assembly of the toroid as well as the cryogenic supply lines, highlights the FEA mechanical calculations performed to predict the shape, summarizes the tooling required and reviews the experience gained during the installation

Echogenic needle for transvaginal ultrasound directed reduction of uterine fibroids and an associated method

The invention is a transvaginal ultrasound probe having an attached echogenic needle that is useful in the treatment of uterine fibroids. The echogenic needle has an echogenic surface near its tip that allows the physician to visualize its location using ultrasound imaging. In one embodiment, the needle has an active electrode at its distal end. The active electrode supplies radio frequency energy to a fibroids causing necrosis of the targeted fibroid or by destroying the fibroid's vascular supply. The radio frequency needle preferably has a safety device that shuts-off energy if the needle punctures the uterine wall. In a second embodiment, the needle has a cryogen supply tube and cryogen supply. This embodiment destroys fibroid tissue by freezing it or its vascular supply when the tissue comes in contact with the needle's frozen distal end. The invention further includes the method of using the ultrasound probe with the attached needle.

Some aspects of the layout and optimization for the cryogenic supply of superconducting linacs

The primary power consumption of large linear accelerators can be significantly lowered by means of superconducting RF technologies. Nevertheless, superconducting RF cavities dissipate energy at low temperatures, and large cryogenic plants have to be operated for the cryogenic supply. In particular, cryogenic plants for future superconducting Energy Recovery Linacs (ERLs) will require primary power in the order of some mega watts. Because of the fundamental laws of thermodynamics, the efficiencies of the cryogenic plants decrease with decreasing operation temperature. At the same time, the dynamic heat losses of high- Q 0 superconducting cavities decrease strongly with temperature. In order to minimize the primary power consumption at stable operating conditions of the cavities, the cryogenic operating conditions, and in particular the operation temperature, have to be optimized. With the focus on helium II cooling, some aspects of cryogenic efficiencies at low temperatures and the consequences for the layout of cryogenic systems are discussed. As an example, options for the cryogenic layout of the European XFEL-Linac including some ERL upgrade options are presented.

Two-phase flow characteristics of liquid oxygen flow in low pressure liquid rocket engine

In most cryogenic liquid rocket engines, liquid oxygen manifold and injector are not thermally insulated from room temperature environment for the purpose of reducing system complexity and weight. This feature of cryogenic liquid supply system results in the situation that liquid oxygen flow is vaporized especially in the vicinity of the manifold and the injector wall. The transient two-phase flow tendency is severe for low combustion pressure rocket engine without using turbo-pump. This paper focuses on the two-phase flow phenomena of liquid oxygen in low combustion pressure rocket engine. The KSR-III (Korea Sounding Rocket) engine test data is thoroughly analyzed to estimate the vapor fraction of liquid oxygen flow near the engine manifold and the injector. During the cold flow and the combustion tests of the KSR-III Engine, the static and dynamic pressures are measured at the engine inlet, the liquid oxygen manifold and the combustion chamber. The manifold outer wall and the inner wall temperatures are also measured. In this paper, we present the experimental investigation on the vapor generation, the vapor mass fraction, and the boiling characteristics of the liquid oxygen flow in the engine manifold and injector.

The superconducting solenoid for the KEDR detector

Performance of the superconducting coil for the KEDR detector is presented. The coil with a diameter of 3 m and 3 m length has been designed for magnetic field up to 1.8 T. The coil has 568 turns of NbTi/Cu cable fixed by soldering (PbSn alloy is used) on the inner wall of the stainless-steel cooling bath. The specific features of this system are the protection of the solenoid by distributed resistance and the power supply being a fluxpump type. The radiation thickness of the solenoid and the E/M ratio are 0.95 X/sub 0/ and 7.8 kJ/kg, respectively. The cryogenic supply system of the KEDR detector has a helium refrigerator with cooling power of 600 W at the temperature of 4.5 K. The main superconducting solenoid and cryogenic system were successfully tested up to 0.7 T and ready for physic experiments with KEDR detector at e/sup +/ e/sup -/ -collider VEPP-4M.

Circuit analysis and control of the power supply system for the testing of ITER TF model coil

The TOSKA test facility of the Forschungszentrum Karlsruhe, which was especially built for testing large superconducting coils, has been upgraded for the test of the ITER Toroidal Field Model Coil (TFMC) in the framework of the ITER-EDA R&D programme. The upgrade includes the extension of the cryogenic supply system, a new 20 kA power supply for the background field generated by the existing LCT Coil as well as two 80 kA current leads and a 80 kA dump circuit for the TFMC. At this stage the power supply systems, including their dump circuits, can be tested only up to 10 kA with a 25 tons Cu coil. Therefore, suitable calculation tools have been developed for circuit analysis, control optimisation and simulation of possible scenarios at full current.

New improvements on the Kansas State University cryogenic electron beam ion source, a user facility for low energy, highly charged ions

The Kansas State University cryogenic electron beam ion source supplies low energy ion beams to users of the Department of Energy user facility for highly charged ions. The ions escape the source with an initial energy between 1.6 and 5 kV per charge and are analyzed in a 90° dipole magnet located on the high voltage platform. When leaving the platform the ions can be accelerated by up to 160 kV per charge or can be decelerated to about 20% of their initial energy, covering 2.5 orders of magnitude. We are in the process of adding another order of magnitude to the range of available ion energies as a newly installed lens allows for deceleration down to a very few percent of the initial energy. In addition we present the current microbunching and chopping system which has been substantially improved over the past 2 yr.

The test facility for the ITER TF model coil

The TF model coil (TFMC) is one of the seven large R&D projects for the ITER EDA. The TFMC will include most of the technical features and manufacturing approaches foreseen for the full size TF coils and it will be tested in a most relevant manner. This testing will take place 1998/99 in the TOSKA facility of FZK, which is upgraded for that purpose in several steps, each one accompanied by own test purposes, qualifying the facility thereby too. The test arrangement will consist of the TFMC in parallel to the existing EURATOM LCT coil. The availability of this LCT coil with full performance has been reconfirmed by operating it in 1996, even with extended performance at 1.8 K. The major parts of the TOSKA facility are a vacuum vessel with nitrogen shield and a useable volume of 4.30 m diameter and 6.6 m height, a cryogenic supply system with a 2 kW and a 500 W helium refrigerator and cold pumps to circulate helium, two electric power supplies for 30 kA and 50 kA, respectively (they can also be operated in parallel to 80 kA), a further power supply for 20 kA, fast dump circuits with power breakers, the required busbar and current leads and a well suited control and data acquisition system. The status of TOSKA is reviewed, giving details of the components and the qualification tests so far, as the poloidal coil experiment POLO and the LCT coil tests at 1.8 K. A further qualification test will be 1997; the tests of the W 7-X stellarator prototype coil in an arrangement similar to the ITER TF model coil testing.

The superconducting magnet for the BABAR detector of the PEP-II B Factory at SLAC

An aluminium stabilized, thin superconducting solenoid is required for the central field of 1.5 T for the BABAR detector. The winding is supported by an aluminium alloy outer cylinder, which provides hoop strength to the coil. The coil has dimensions of 3 m in diameter and 3.7 m in length. The current density is graded to meet the field uniformity requirements of /spl plusmn/2%. A hexagonal flux return, comprised of a barrel and two end doors provides the external flux path for the field. Additional material is required in the end caps to shield the flux from the beam line magnets. To accommodate the muon detectors, the barrel and end caps are segmented into 20 plates of different thickness. Special attention is given to the support of the coil and cryostat to account for seismic loading. The coil is indirectly cooled to 4.5 K using the liquid helium thermo-siphon technique and cooling channels welded to the support cylinder. Automatic cooldown and cryogen supply to the coil and its 40 K radiation shield is done by a helium liquefier/refrigerator via coaxial, return gas screened, flexible transfer lines.

Superconducting fast cycling magnets of the Nuclotron

The new superconducting heavy ion synchrotron-Nuclotron was put into operation at the Laboratory of High Energies. The maximum design energy is 6 GeV/u. There are 160 pulsed SC magnets with a "cold" iron yoke and a hollow superconductor winding in the ring. A magnetic field of 2 T is provided under a supply current of 6 kA. The magnets were tested under a cycle dB/dt=4 T/s, B=2 T, and a ramp rate f=1.0 Hz. A two-phase helium flow was chosen as a coolant. The Nuclotron "cold" mass is about 80 tons. The cryogenic supply system capacity is 4.8 kW at 4.5 K. The total running time of the Nuclotron reached 1100 hours after the last run in March 1994.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulations of cryogen expulsion from a space depot under zero gravity

With an increasing number of missions in space, cryogenic fluid supply systems become necessary as mission duration is extended. Most of the system operations involve multiple-phase phenomena. Accurate simulation of the operations is needed to predict the physics and efficiency of these systems. One operation of interest is the expulsion of liquid cryogens from a partially filled depot; the challenge concerns finding ways to expel the liquid while preventing vapour from entering the transfer line. The problem involves tracking the motion of a floating, mobile and expanding vapour ullage as fluid is expelled from a tank. The simulation of the interface movement of the vapour ullage in a volume of confined liquid under zero gravity is carried out by solving the Navier-Stokes equations in the transformed boundary-fitted curvilinear co-ordinate system using a finite difference approach. An alternating expulsion and pressurization scheme is presented for the operation based on mass and momentum conservation.

Cryogenic fluid management investigations using the CONE flight experiment

The Cryogenic Orbital Nitrogen Experiment (CONE) is a liquid nitrogen cryogenic storage and supply system demonstration placed in orbit by the National Space Transportation System (NSTS) Orbiter and operated as an in-bay payload whose objective is to demonstrate needed critical components and technologies. A conceptual approach has been developed by Martin Marietta under contract with the NASA Lewis Research Center and an overview of the CONE program is described which include a definition of the background and scope of the technology objectives being investigated, a description of the payload design and operation, major features and rationale for the experiments being conducted and the justification for CONE relating to potential near-term benefits and risk mitigation for future systems.

Investigation of the transient processes in channels with a two-phase cryogenic agent and underheating at the inlet

A characteristic of modern cryostatic systems for power-generating objects is the complex operating mode with prolonged heat evolution pulses (lasting for more than 1 sec)~ uniformly distributed along the channels, with a thermal flux density of 10-50 W/m 2 [i]. At such heat loads the temperature of the cryogenic agent can rise above the permissible value, based on the condition of maintaining the temperature of the channel walls (the current-carrying element) within a relatively narrow interval; variations in the flow rate can also occur at the channel outlets which can disturb the normal operation of the cryogenic supply system. It must be pointed out that prolonged pulsed heat liberations in the operation of cryogenergetic installations can occur regularly, i.e., that they can repeat themselves at regular time intervals.

A two-phase full-wave superconducting rectifier

A two-phase full-wave superconducting rectifier has been developed as a small cryogenic power supply of superconducting magnets for magnetically levitation trains. Those magnets will be operated in the persistent current mode. However, small ohmic loss caused at resistive joints, and AC loss induced by the vibration of the train cannot be avoided. Therefore, the low-power cryogenic power supply will be required to compensate for the reduction in magnet current. The superconducting rectifiers consists of two identical full-wave rectifiers connected in series. The main components of each rectifier are a toroidal superconducting setup transformer and two thermally controlled switches. The test results using a 47.5-mH-load magnet at 0.2 Hz and 0.5 Hz operations are described. To estimate the characteristics of the superconducting rectifier, the authors have developed a simulation code. From the experiments and the simulations, the transfer efficiency is determined. >

Development of an Advanced Hybrid Control System for a Cryogenic Spectrometer

NASA's Upper Atmosphere Research Satellite (UARS), to be launched in 1988, will study trace elements in the upper atmosphere. To make measurements, the UARS carries onboard a cryogenically-cooled infrared spectrometer called the Cryogenic Limb Array Etalon Spectrometer (CLAES), which operates at temperatures from 130 K to 13 K. CLAES combines a mUlti-position tilt-scanned Fabry-Perot etalon and filters to provide a high spectral resolution which permits identification of the desired chemical species from spectral radiance measurements. CLAES system requirements include angular positioning of individual etalons within the CLAES optical system, rapid rotation of the etalon holder to the next etalon to be used in measurement sequence, and mi nimi zati on of the thermal energy di ssi pated by the actuator. Since the etalons must operate below 20 K for 18 to 24 months on a limited cryogen supply, all thermal inputs must be minimized, and reliable long-life operation of electromechanical devices is required. A precision, hybrid position control system, capable of both rapid slewing between etalons and precise positioning of an individual etalon during measurement sequences, has been designed and tested at the Lockheed Palo Alto Research Laboratory. The system util izes a unique actuator concept which combines the features of a brushless dc torque motor and a stepper motor. Because the actuator can be used in a direct-drive mode, it eliminates the problems associated with gearboxes and reduces the number of required bearings.

Design and construction of a 20W/1000A cryogenic power supply

In order to meet the requirements for accurate and low power supplies for superconducting applications, a 20W/1kA cryogenic power supply was designed and constructed. It is a full-wave superconducting rectifier, and is taken as a starting point for further developments. The superconducting part consists of an air core transformer and thermally controlled superconducting switches. To operate the system Holec constructed an electronic control unit. The rectifier was tested by using a small 17.5mH coil and an 0.5T NMR magnet. The small coil was loaded to 750A; the current was limited by quenches in the load coil. The average power of the rectifier was measured at several currents . Experiments show that the efficiency is higher than 97%. From the experiments it was concluded that in general the performance of the rectifier is according the design specifications.