Cold Mass Support System Research Articles

A Retrospective on how Cryostats have changed with Cryostat Use and the Cooling Methods used to keep Superconducting Magnets Cold

Prior to the invention of the vacuum flask by James Dewar in 1895, cryogenic temperatures below 100 K could not be sustained very long. The Development of the modern cryostat was an extension of the basic Dewar vacuum flask. The design of the cryostat, its insulation, and the cold mass support system is a function of the cryostat’s intended use. The type of refrigeration available also influenced the development insulation systems, support systems, transfer lines and electrical leads that are part of the cryostat. In recent years the availability and the cost of helium has been a significant factor in cryostat design and the methods used to cool and cool-down cryostats. This paper explores the historical development of today’s cryostats and how that can be tied to the source of cryogenic cooling. This paper is focused on earth bound cryostats. Some of the same principles can be applied cryostats used in space.

Composite support system for 1.5 T whole-body MRI cryostat

Support system is one of the most critical components of any MRI cryostat in providing the structural integrity during operation and the transportation. We have designed and analyzed the behavior of the composite support structures designed for a 1.5 T MRI cryostat. Various design criteria including the mechanical strength of the composite support system, mechanical resonance frequency of the cryostat, the heat inleak to 4.2 K etc. need to be considered during designing of the composite support system. The dimensional constraints as well as requirements for structural stability and heat conduction to 4.2 K has been established after identification and consideration of problems associated with superconducting magnet support system in MRI. The design incorporates s-glass support straps with intermediate thermal intercepts at 60 K and has been designed to suspend ∼ 5 tons of cold mass. This paper briefly discusses the static and dynamic stress simulation of cryogenic support link of the MRI cryostat using ANSYS. Based on the material choice, the heat leaks down the cold mass support system to 4.2 K and to 60 K are calculated as 250mW and 4.6 W respectively. The spring constant of the support system is 2.79 × 108 Nm-1.

Cold Mass Support System for the MSU Superconducting Cyclotron Gas-Stopper Magnet

The cyclotron gas-stopper magnet at Michigan State University consists of two superconducting coils, each in its own cryostat. The two cryostats are mounted in the two warm iron poles of a sector cyclotron magnet used to control the orbit of heavy ions as the particle energy is being removed by circulating the ions through helium gas. Because the two poles of the magnet must be separated to install the gas chamber and beam extraction system, the magnet coils cannot be connected together. As a result, the magnet cold mass support system must carry the forces pushing the magnet into the iron pole as well as any decentering forces that occur from coil placement errors. The cold mass support system for each magnet coil consists of six compression supports that support magnet forces in the axial direction. In addition, there are three radial supports to center the coil axis coaxial with the axis of the iron poles. This paper presents an analysis of the superconducting magnet cold mass support system, which must be designed to have a spring constant that is higher than the magnet force constant at the full design current for the magnet.

Design and Analysis of a Self-Centered Cold Mass Support for the MICE Coupling Magnet

The Muon Ionization Cooling Experiment (MICE) consists of eighteen superconducting solenoid coils in seven modules, which are magnetically hooked together since there is no iron to shield the coils and the return flux. The RF coupling coil (RFCC) module consists of a superconducting coupling solenoid mounted around four conventional conducting 201.25 MHz closed RF cavities. The coupling coil will produce up to a 2.2 T magnetic field on the centerline to keep the beam within the RF cavities. The peak magnetic force on the coupling magnet from other magnets in MICE is up to 500 kN in longitudinal direction, which will be transferred to the base of the RF coupling coil (RFCC) module through a cold mass support system. A self-centered double-band cold mass support system with intermediate thermal interruption is applied to the coupling magnet, and the design is introduced in detail in this paper. The thermal and structural analysis on the cold mass support assembly has been carried out using ANSYS. The present design of the cold mass support can satisfy with the stringent requirements for the magnet center and axis azimuthal angle at 4.2 K and fully charged.

The Helium Cooling System and Cold Mass Support System for the MICE Coupling Solenoid

The MICE cooling channel consists of alternating three absorber focus coil module (AFC) and two RF coupling coil module (RFCC) where the process of muon cooling and reacceleration occurs. The RFCC module comprises a superconducting coupling solenoid mounted around four conventional conducting 201.25 MHz closed RF cavities and producing up to 2.2 T magnetic field on the centerline. The coupling coil magnetic field is to produce a low muon beam beta function in order to keep the beam within the RF cavities. The magnet is to be built using commercial niobium titanium MRI conductors and cooled by pulse tube coolers that produce 1.5 W of cooling capacity at 4.2 K each. A self-centering support system is applied for the coupling magnet cold mass support, which is designed to carry a longitudinal force up to 500 kN. This report will describe the updated design for the MICE coupling magnet. The cold mass support system and helium cooling system are discussed in detail.

The Cold Mass Support System and the Helium Cooling System for the MICE Focusing Solenoid

The heart of the absorber focus coil (AFC) module for the muon ionization cooling experiment (MICE) is the two-coil superconducting solenoid that surrounds the muon absorber. The superconducting magnet focuses the muons that are cooled using ionization cooling, in order to improve the efficiency of cooling. The coils of the magnet may either be run in the solenoid mode (both coils operate at the same polarity) or the gradient (the coils operate at opposite polarity). The AFC magnet cold mass support system is designed to carry a longitudinal force up to 700 kN. The AFC module will be cooled using three pulse tube coolers that produce 1.5 W of cooling at 4.2 K. One of the coolers will be used to cool the liquid (hydrogen or helium) absorber used for ionization cooling. The other two coolers will cool the superconducting solenoid. This report will describe the MICE AFC magnet. The cold mass supports will be discussed. The reasons for using a pulsed tube cooler to cool this superconducting magnet will also be discussed.

Design concept for the GEM detector magnet

The magnet has two symmetric and independent halves, each containing a cold mass assembly operating nominally at 4.5 K, a set of vapor cooled leads, a cold mass support system, a liquid nitrogen shield system, and a vacuum vessel. Also included in each half is a forward field shaper which provides a component of magnetic induction normal to the path of low angle muons in the forward region, thereby improving their resolution. The unique features of this magnet are the conductor design itself and the large coil diameter, which demands an on-site winding and assembly operation. The use of a natural convection thermosiphon loop for thermal radiation cooling eliminates plumbing complications. Locating the aluminium sheath outside the conduit for quench protection permits optimizing the copper-to-superconductor ratio inside the conduit for stability alone. The conceptual design for the magnet, including the design for the detector dependent magnetics, the superconducting coils and coil structure (cold mass), the coil winding process, the vacuum vessel and liquid nitrogen shields, the cold mass supports, and the magnet assembly procedure, are described. >

A prototype 0.5 tesla whole body imaging magnet system

A prototype superconducting 0.5-T/1-m bore whole-body magnetic resonance imaging (MRI) system recently completed by GA Technologies Inc. for Ishikawajima-Harima Heavy Industries (IHI) is described. The magnet system makes use of the following key features: a precision-wound, profiled, 250-A coil, which exhibits high inherent field uniformity ( approximately 100 p.p.m./50 cm DSV); superconducting shim coils, which allow uniformity without passive bore shims; a novel cold mass support system for omnidirectional 5-g support with low heat leak; two concentric heat shields, cooled by an integral Gifford-McMahon two-stage refrigerator, yielding a net helium boiloff at 0.1 L/h with no liquid-nitrogen system; mechanically retractable, thermally decoupling current leads; and low-current-drift persistent-mode operation (0.085 p.p.m./h), with an internal protection circuit.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>