A Cyclotron Magnet Case Study: Would Replacing the LTS Coils With HTS Coils Make Sense?

Abstract

The cyclotron gas-stopper magnet (CGSM) at Michigan State University (MSU) was used as model for a study for whether HTS conductor is feasible for use in cyclotrons. The outside diameter of the CGSM split warm iron magnet yoke is 4 m, with a pole radius of 1.1 m. The desired field shape is obtained by shaping the iron pole profile. Each superconducting coil is in a separate cryostat. The two coils are connected in series through the warm electrical connection. Each coil is wound and potted within an 80 mm × 80 mm cross section and mounted within a 304 stainless steel helium vessel that is designed to carry magnetic forces to the magnet cold mass supports without excessive deflection. The iron is split, so that the cyclotron chamber and RF extraction system can be mounted between the two poles. This magnet has been successfully cooled down and tested at MSU to its 180-A operating current. One can ask the following question, "If one built a cyclotron magnet the size of the MSU cyclotron gas-stopper magnet, would replacing the existing LTS coils with HTS coils using a standard second generation HTS tape make technical sense or economic sense?" The report will explore the technical and economic issues of replacing an existing LTS coil with an HTS coil of the same size and shape, using 2G YBCO tape conductor commercially available in 2015 in place of the Nb-Ti used in the magnet.

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

“…The notion of much cheaper refrigeration and cryostats was, in part, an illusion because the heat leaks into the cryostats were higher than expected. The savings in the refrigeration cost was less than the additional cost of the HTS superconductor [50].…”

“…There is a general consensus that cryogenic temperatures are below 125 K, but his author defines the dawn of low temperature cryogenics (< 90 K) as the time when the most abundant air gasses were liquefied and collected. Nitrogen, oxygen and carbon monoxide were first liquefied by Wroblewski and Olszeski, cascade cooling using ethylene and isenthalpic expansion from 50 Pa through what we call today a J-T valve in 1883 [1]. The insulation of the container could not have been little more than cork.…”

A review of commercial high temperature superconducting materials for large magnets: from wires and tapes to cables and conductors

“…For example the price of Bi2233 followed an exponential but it has not a general validity, because the maximum stresses at operation are not considered (this is very important for example in high field solenoids). Unfortunately the most accurate and trustful method to evaluate the price difference between LTS and HTS for a certain device is likely to carry out the whole design process twice, once for the LTS option and once for the HTS option, of course trying to exploit the material at its maximum potential, and considering the costs of the auxiliary components (see for example [72]). The market for technical superconductors The outstanding performance of coated conductors does not necessarily guarantee its commercial success.…”

Can High Current Density HTS Magnets be Quench Protected Using Methods Used to Protect High Current Density LTS Magnets?

“…Conventional wisdom says that one must do the following in order to safely quench an HTS magnet [10], [11]: 1) One must have more low resistivity normal metal in conductor to reduce J and extend the safe decay time; 2) one must detect the quench quickly and put a resistance across the coil to reduce current rapidly; and 3) one must sub-divide the coil to reduce the voltages to ground and between layers. Adding normal metal to an HTS conductor is problematic and the added metal makes the quench harder to detect.…”