Helium Container Research Articles

A Novel Design for Improving the Control on the Stainless-Steel Vessel Welding Process for Superconducting Magnets

Stainless steel vessels see widespread use in superconducting magnets for particle accelerator applications. Their function varies in different magnet designs: they always provide the necessary liquid helium containment, but in some cases are also used to provide azimuthal prestress and can also be welded to the magnet end plate to provide additional longitudinal stiffness. A magnet designed with the bladder and key technology does not rely on the structural role of the vessel. They are structurally supported using azimuthally prestressed aluminum shells, and the longitudinal constraint by rods. In this case, the magnet designer would generally like to minimize the interaction between the magnet and the stainless-steel vessel and to minimize the coil stress variation due to the vessel. The stress state in the vessel and in the coil is a function of the circumferential interference, defined as the vessel azimuthal length minus the magnet circumference. The vessel and the magnet azimuthal length machining tolerances are relatively large resulting in significant stress variations in the superconducting coils. In this paper we introduce an interference-control shim, which can significantly limit the stress variation of the coils for a given variation of the interference. The effectiveness of the interference-control shim is evaluated numerically on the MQXF, the low- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> quadrupole for the High Luminosity LHC.

Multipole magnets for the HIAF fragment separator using the Canted-Cosine-Theta (CCT) geometry

The fragment separator of the HIAF (High Intensity Heavy Ion Accelerator Facility) project called HFRS requires quadrupoles with high gradients (11.4 T/m) and large bores (320 mm in diameter). The iron dominated magnets with superconducting coils have been widely used in the similar facilities such as A1900, BigRIPS, Super!FRS and RISP with the advantages of low request for coils installation precision, simple fabrication and low cost, but they have large cold mass and helium containment, which result in long time cooling down and high pressure rise during a quench. In addition, due to iron saturation, it is hard to guarantee on the field quality in the operated field range. A new coil dominated design based on the Canted!Cosine!Theta geometry is presented for HFRS, which is expected to overcome these problems. The design superimposes several layers of oppositely wound helical windings to generate high quality quadrupole. Sextupole, octupole and steering dipole can also be easily integrated to reduce the length of cryostat. This paper reports the detailed design of HFRS multiplets based on the CCT concept and the construction of a subscale prototype.

Development of a Zero Rate Evaporation Cryogenic System for 200 MeV Proton Cyclotron

Based on the collaboration of ASIPP (Hefei, China)–JINR (Dubna, Russia) for proton therapy, a 200-MeV compact superconducting proton cyclotron project (SC-200 project) has been launched at ASIPP. The superconducting coil of the main magnet system for cyclotron is cooled by liquid helium. A zero rate evaporation cryogenic system has been designed and tested for the main superconducting magnet system. Three GM-cry coolers (40 W at 50 K, 1.5 W at 4.2 K) were worked as the cold source to cooling the thermal shield, a pair of high-temperature superconducting current leads (HTSCL) and liquid helium container. The test results show that the thermal shield and HTSCL can be cooler lower than 77 K, the heat load of the cryogenic system is less than 2.8 W. The detail design of the cryogenic system and test process will be described in the paper.

Design of a 150-mm Coil Support Structure With Accelerator Integration Features for LARP &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\hbox{Nb}_{3}\hbox{Sn}$&lt;/tex&gt;&lt;/formula&gt; Quadrupole Magnets

The design of a structure for the 150-mm coil aperture Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn quadrupole magnet is presented to demonstrate principles for use in the upgrade for LHC at CERN. The design builds on existing technology developed in LARP and further optimizes the features required for operation in the accelerator. The structure and the assembly methods include features for maintaining mechanical alignment of the coils to achieve the required field quality. The structure also incorporates a helium containment vessel and provisions for cooling with 1.9 K helium. The paper will include critical design elements and supporting structural analysis.

Mechanical Design, Assembly and Testing of a Support Structure for LARP ${\rm Nb}_{3}{\rm Sn}$ Quadrupole Magnets for LHC

A support structure for the 120 mm Nb3Sn quadrupole magnet is presently under development for use in the upgrade for LHC at CERN. The design aims to build on existing technology developed in LARP with the LQ and HQ mag- nets and to further optimize the features required for operation in the accelerator. The structure and the proposed assembly methods include features for maintaining mechanical alignment of the coils to achieve the required field quality. It also includes a helium containment vessel and provisions for cooling with 1.9 K helium. The development effort includes the assembly of a 15 cm model to verify required coil load is achieved. Status of the R&D effort and an update on the magnet design, including its incorporation into the design of a complete one meter long cold mass is presented.

Precise Magnetization Measurements by Parallel Self-Compensated Induction Coils in a Vertical Single-Turn Coil up to 103 T

We have developed a magnetization measurement technique for use in a vertically aligned single-turn coil. Compensation ratios of an order as high as 10 -4 were achieved by self-compensation in parallel twin-pickup coils without using the electronic compensation circuit mixing of the signal from an auxiliary coil. High performance cryogenics was employed with a liquid Helium container that was also manufactured to fit the system. The high-magnetic-field magnetization measurements were applied to a manganite Bi 0.5 Ca 0.5 MnO 3 at room temperature, and also to a geometrically frustrated spinel oxide, CdCr 2 O 4 at very low temperatures. Not only the transition field, but also the absolute value of the magnetization was shown to be evaluated within a 3% degree of accuracy in magnetic fields of up to 103 T by means of a 14-mm inner-diameter single-turn coil.

Energy deposition by electrons in superfluid helium and design of a detector for solar neutrinos

We report recent progress in the development of HERON, a detector of low-energy solar neutrinos that will use as a target material 10 tons of liquid helium. The HERON detector is intended to detect p–p neutrinos from the sun in real time with a an energy threshold of approximately 50 keV. The recoil energy of electrons resulting from the elastic scattering of neutrinos is measured with calorimetric wafers above the free surface of the liquid at 40 mK. Both the EUV scintillation and the helium atoms produced by quantum evaporation, which result from phonos and rotons hitting the free surface, are detected by the wafers. Background rejection is achieved statistically by a determination of event location with respect to the walls of the helium containment. The wafers will be used to form a coded aperture array. If the wafers have an energy threshold such that they can detect single 16 eV photons, a neutrino event having a recoil electron with an energy greater than 50 keV could be located to within 10 cm or better anywhere in the 10 tons of helium.

Experimental analysis of thermalisation and emissivity of radiation screens for cryostat design

The article describes a method of characterising thermalisation and reflectivity of radiation screens in vertical vapour shielded cryostats after analysing the evaporation rate and key temperatures in steady state and some transient states. Variants on the thermalisation of the radiation screen to the helium container neck have been tested and effective hemispherical emissivities deduced for three different configurations of vapour shielded vertical cryostats. The experimental evolution of screen temperatures and the evaporation rate in steady conditions has been compared with computer calculations. Results obtained from each configuration and the options chosen for a 1 MJ SMES cryostat are presented.

5267445 Cryomagnet system with a low-loss helium cryostat of minimized disturbances

A cryomagnet system, in particular for use with nuclear magnetic resonance (NMR) experiments or ion cyclotron resonance (ICR) experiments, with a low-loss helium cryostat (1) comprising a helium container (2) and one or a plurality of tubes for the feed or exit of helium into or out of the helium container (2), respectively, the tubes being sealed to the atmosphere outside the helium container (2) by at least one non-return low-pressure valve (4), wherein at least one exhaust pipeline (3) is provided with a device for dissipating the energy of the expanding helium. Such a device may consist of a chamber which is deviated from the exhaust pipeline (3) and has a wall material of very high extensibility, e.g. a folding balloon. Yet the device may also consist of a flow baffle which is provided in the exhaust pipeline (3), for example a porous disc (6). The device withdraws kinetic energy from thermo-acoustic oscillations of the helium gas column in the conduit system of the cryostat and thus dampens the detrimental oscillations which entrain increased losses of helium and disturbance of the magnetic field at the locus of the sample (FIG. 3a).

SMES conductor selection: an engineering perspective

The authors discuss the engineering considerations driving the selection of a conductor concept for large-scale SMES (superconducting magnetic energy storage). There are five areas that require special attention: current diffusion effects, stability margin, AC losses, cooldown stress sustained by the conductor, and helium containment. From a magnet design perspective, there is a strong premium in SMES on utilizing conductors with as high a current as possible. It is difficult to scale up a particular monolithic design to achieve higher current. Overall magnet design issues are also more difficult to tackle with monolithic conductors. It is concluded that cable-in-conduit conductors are more attractive for large-scale SMES. >

Key design selections for the 20.4 MWh SMES/ETM

The 20.4-MWh superconducting magnetic energy storage engineering test model (SMES/ETM) will be the world's largest superconducting magnet by nearly two orders of magnitude in stored energy. Its size, Lorentz loads, and power delivery requirements dictate a number of fundamental design requirements. In addition, the SMES/ETM must fully accomplish its primary mission of demonstrating large-scale SMES technology, while at the same time minimizing technical, schedule, and cost risks. A discussion is presented of nine key design decisions that are fundamental to meeting these challenging goals. These are a conductor current of 200 kA, helium containment within the conductor, an operating temperature of 1.8 K, a CICC conductor with a hollow core, a conductor premanufactured in half-turn lengths, a circular and continuous coil pac structure, fiberglass-reinforced plastic pultrusion for the coil pack structure material, a coil pack operating position that is precompressed radially inward, and a liner for vacuum enclosure.

Shielding liquid helium from the influx of external heat in a nuclear radiation field

Specimens at the temperature of liquid helium are irradiated in a reactor by providing a cryochannel with cyrogenic machines [i, 2] one of which produces liquid helium, which is poured into the cryochannel, while the other produces gaseous helium at 10-20 deg K, which cools the cryochannel screens. In certain cases, it is more convenient and advantageous to use a relatively simple cryochannel with liquid helium which is brought in, all the more so as it becomes possible to reduce considerably the influx of external heat to liquid helium by using its vapor produced by additional vaporization of liquid helium from the unavoidable heat release in the liquid helium container in a nuclear radiation field.

GROWTH OF SUPERCONDUCTING THICK FILMS OF YBaCuO BY SPRAY PYROLYSIS TECHNIQUE AND STUDY OF QUANTUM INTERFERENCE EFFECTS

Superconducting thick films of YBaCuO are made by spray pyrolysis technique on single crystal SrTiO 3 and MgO substrates. The thickness of the film is about 10 µm. The best film shows T c (R = 0) of the order of 86 K. No marked degradation in superconducting transition temperature is observed when the films are thermally cycled between room temperature and 4.2 K inside a closed liquid helium container. Temperature dependence of the critical current of microbridges fabricated on this film indicates the presence of SNS type weak links. dc SQUID configuration has been made in this film by scribing two bridges in parallel. V - Φ curves show periodic behavior superposed with additional structures.

Structural characteristics of proposed ITER TF coil conductor

An analysis has been conducted of the effect of transverse loading on a cable-in-conduit conductor which has been proposed for the toroidal field coils of the International Thermonuclear Experiment Reactor. The primary components of this conductor are a loose cable of superconducting wires, a thin-wall tube for helium containment, and a U-shaped structural channel. A method is given where the geometry of this conductor can be optimized for a given set of operating conditions. It is shown, using finite-element modeling, that the structural channel is effective in supporting loads due to transverse forces and internal pressure. In addition, it is shown that the superconducting cable is effectively shielded from external transverse loads that might otherwise degrade its current-carrying capacity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A 3 T superconducting magnet for the amy detector

A 3 T high field superconducting magnet was constructed for the AMY detector at the TRISTAN electron-positron storage ring. Cooldown and excitation tests of the magnet were carried out with the detector in its final configuration. The coil is made with a fully stabilized superconductor wound into an eight layer cylinder with a 2.39 m inner diameter, a 2.58 m outer diameter and 1.54 m in length. An outer jacket of thick stainless steel was shrunk-fit around the coil to provide strength to contain the magnetic forces and to serve as a liquid helium container for the pool boiling cooling system for the coil. A computer controlled refrigeration system with a capacity of 300 W at 4.4. K (100 l/h) was prepared to cool down the 17 t of cold mass of the magnet. It took about five days to cool down from room temperature and achieve a superconducting state, and an additional two days to completely fill the coil with liquid helium and to prepare for the excitation of the magnet. The thermal stresses on the coil support rods were evenly balanced during the cooldown, and the mechanical stresses on the support rods at full excitation (a current of 5000 A) were well below the allowed maximum. In order to verify the safe operation of the magnet system, we carried out fast discharge tests with a time constant of 21 s, which was optimized to protect the magnet from quench. The pressure rise in the helium vessel during the discharge from 5000 A was an easily manageable 1.38 × 10 5 Pa. During the fast discharge of the 5000 A excitation, the coil showed no signs of developing any normal regions. At the maximum rated current of 5000 A, the central magnetic field and the inductance were measured to be 3.0367 and 3.2 H, respectively, corresponding to a stored energy of 40 MJ, in good agreement with magnetic field calculations. During these tests and in the succeeding long term operation, the magnet showed excellent stability and reliability.

Utilization of Liquid Nitrogen in Recent Years

It is well known that the liquid nitrogen is being used as the refrigerant for cryogenic physics and chemistry, precooling of helium gas to liquefy, heat shield in liquid helium container, cold trap in high vacuum system, precooling of superconducting magnet, experiment of cryogenic power transmission, and low temperature adsorption to purify the gases. Moreover, in space development, liquid nitrogen is used to cool the fuel tanks of the rocket and for all kinds of low temperature environmental testing. But it can be seen that they are special usage in limited research field.On the other hand, the large scale production of oxygen by the recent remarkable demand in iron and steel making industry has brought the lowering of the gas cost. This trend is promoting extensive utilization of liquid nitrogen not only in special research field but also in ordinary industrial field.This paper describes many useful methods of liquid nitrogen use in industry such as food, construction, rubber, metals fabrication, crushing, biology and medicine.In the future, it is supposed that a large amount of liquid nitrogen will be consumed for disposing of waste materials in a point of view to prevent environmental pollution and to reclaim them.

Low Temperature Setup for Electron Irradiation and Subsequent Photoconductivity Studies of Semiconductors

A cryostat is described for irradiations with electrons at liquid helium temperatures and subsequent photoconductivity and infrared absorption studies in the range from 20 to 400 K. Heat is removed from the sample by conduction through a copper tail touching the bottom of the liquid helium container. A mechanical ``switch'' enables the thermal separation of the sample assembly from the helium bath during the annealing studies. A rotatable outer-tail piece permits irradiation with electrons through aluminum windows avoiding damage to the optical NaCl windows. The beam dosimetry and monitoring equipment are described in detail.

Some Characteristics of Cryopump

Some characteristics of a newly developed cryopump were studied, which makes a step of our serial investigations of the application of cryogenics to high-vacuum ; as a pumping method of the ultra-high vacuum thin film evaporator.The cryogenerator is composed of six heat exchangers, an expansion engine (reciprocating type), and two Joule-Thomson valves, as shown in Fig. 1. Cold generated by this apparatus was measured as 10 watts at 4.2°K. The generator can also be used as a helium liquefier adapting a helium container shown in Fig. 5.The cryopanel of which diameter is 200mm, colded by the cryogenerator, can be refrigerated down to 812°K, within two hours after starting, and the ultimate pressure was measured as 9.8×10-9 torr by B-A gauge, and 1.13×10-8 torr by RH gauge.The relation between pressure and cryopanel temperature is shown in Fig. 10, and composition of the residual gas was analized as shown in Fig. 11. By this analysis, the ultimate pressure seemed to be decided principally by the hydrogen, in ultra-high vacuum region.The pumping speed was measured as 3.0 l/sec cm2 for nitrogen gas in pressure range of10-710-4 torr, shown in Fig. 12. The pumping speed did not be affected by the deposited solid nitrogen film even its thickness assumed 1.7mm.

Low Evaporation Rate Storage Vessel for Liquid Helium

Expressions are derived for the heat flux q0 and temperature gradient dT/dh in a Pyrex cylinder (a) in vacuo and (b) in the atmosphere of cold vapor issuing from a liquid helium container. In the temperature range 20&amp;lt;T&amp;lt;300 we find for case (a) that q0 α T1.8 and dT/dh α T−0.8, while in case (b) q0 α̇ T and dT/dh is nearly constant. Design details and operating procedures are given for a 12-liter liquid helium storage vessel intended to complement our Collins helium liquefier. It can be filled in one day's operation of the liquefier, and ten days later is still half full.

Evaporation Rate of Liquid Helium. I

In connection with a study of the emissivity of metals at low temperatures, a quantitative analysis has been made of the factors involved in the design of storage containers for liquid helium. Experiments confirm the analysis, which has resulted in an exceedingly simple liquid-nitrogen-protected liquid helium container having a helium evaporation rate of 1 percent per day. The hemispherical emissivity of mechanically polished copper at 4.23°K was determined for blackbody radiation. For radiation corresponding to that emitted by a blackbody at 77.1°K and 297.1°K, the measured emissivities are 6.9×10−3 and 1.29×10−2, respectively. These data are discussed in relation to the recent theoretical work of Reuter and Sondheimer. The heat of vaporization of helium at 4.228°K was determined to be 4.93 cal g−1, in substantial agreement with the data of Dana and Kamerlingh Onnes. Kistemaker's thermodynamic considerations questioning the accuracy of these data are evaluated in terms of the new determination.