Utilization of large heat capacity substances for improving the stability of superconducting magnets

184

151

A review of non-traditional approaches and emerging trends in superconducting magnets for MRI is presented. Novel technologies and concepts have arisen in response to new clinical imaging needs, changes in market cost structure, and the realities of newly developing markets. Among key trends are an increasing emphasis on patient comfort and the need for 'greener' magnets with reduced helium usage. The paper starts with a brief overview of the well-optimized conventional MR magnet technology that presently firmly occupies the dominant position in the imaging market up to 9.4 T. Non-traditional magnet geometries, with an emphasis on openness, are reviewed. The prospects of MgB 2 and high-temperature superconductors for MRI applications are discussed. In many cases the introduction of novel technologies into a cost-conscious commercial market will be stimulated by growing needs for advanced customized procedures, and specialty scanners such as orthopedic or head imagers can lead the way due to the intrinsic advantages in their design. A review of ultrahigh-field MR is presented, including the largest 11.7 T Iseult magnet. Advanced cryogenics approaches with an emphasis on low-volume helium systems, including hermetically sealed self-contained cryostats requiring no user intervention, as well as future non-traditional non-helium cryogenics, are presented.

Section: Toward Future Mri: Low Helium Volume Cryogenicsmentioning

confidence: 99%

Novel technologies and configurations of superconducting magnets for MRI

Lvovsky

Stautner

Zhang

2013

184

151

“…During the last decade, we have obtained some encouraging results [1] regarding improvement of the thermal stability of low-temperature superconducting magnets by introducing into the winding small amounts of large heat capacity substances (LHCS)-some rare-earth compounds with anomalously high heat capacity at liquid helium (LHe) temperatures (CeCu 6 , HoCu 2 , PrB 6 , Gd 2 O 3 , Gd 2 O 2 S). We started in 2003 using the external doping technique (the introduction of LHCS powders into the inter-turn space of the winding mixed with epoxy resin).…”

Section: Introductionmentioning

confidence: 99%

Cu/Nb-Ti MRI wires with improved stability by incorporating filaments of large heat capacity substance PrB₆

Кейлин¹,

Ковалев²,

Kruglov³

et al. 2015

In this paper we report our recent research on thermal stabilization of low-temperature superconducting magnets by means of large heat capacity substances (LHCS). Two samples (lengths ∼100 m) of NbTi composite wires with additional internal filaments made from intermetallic compound PrB6 (5.9–7.3 vol.%) were produced and tested. The design of the wires was similar to that of the conventional MRI sc wires, except for their smaller diameter (0.835 mm instead of 1.345 mm). Our final goal was the investigation of the possibility to minimize (or even eliminate completely) the necessity of MRI magnets training before their commissioning. The comparative stability measurements showed a twofold increase of the minimum quench energies (MQEs) of the doped wires against short heat disturbances. The magnetic field corresponding to the first flux jump increased by 50%. In MQE tests, the PrB6 heat capacity was fully utilized over the course of a 1 ms heat pulse. In the thermomagnetic stability measurements, the efficiency of LHCS doping was about 75% due to the fast evolution of the flux jumps.

“…The heat capacity of such substances (at 4-10 K) can be up to 2-3 orders of magnitude higher than that for materials usually used in SM. The R&D on different methods of LHCS SM doping started at the Kurchatov Institute in 2003 [1]. Later the Bochvar Institute for Non-organic Materials joined this R&D activity.…”

Section: Introductionmentioning

confidence: 99%

Stability of superconducting coils made of NbTi wires internally doped with large heat capacity Gd₂O₃powder

Кейлин

Iljin

Наумов

et al. 2012

During the past decade we have been carrying out R&D aimed at increasing the stability of low temperature superconducting magnets. The main idea is to enhance the superconductor temperature margin by means of introduction into the winding of several volume per cent of specific substances with enormously large heat capacities (LHCS) at liquid helium temperatures. Two doping techniques have been developed at the Kurchatov and Bochvar institutes: the 'external' one-introduction of a dopant into the epoxy compound-and the 'internal' one-the introduction of doping filaments directly into NbTi and Nb 3 Sn wires. Up to now, our experiments with LHCS internal doping have been carried out on short samples only. In this paper we report the first experimental and numerical investigation of the stability of small-scale internally doped coils made of NbTi wires of a new type, with Gd 2 O 3 ceramic filaments. The coil wound from doped wire and an identical control coil without any doping were subjected to electromagnetic pulses with 1.4-7.4 ms duration. Minimum quench energies for the doped coil turned out to be about 80% larger than those for the undoped one. The gain is especially pronounced in the range of large transport currents (∼0.9I c ). Comparative effectiveness analyses of the two (external and internal) LHCS doping techniques are also presented.