Presentation Information
[WB5-04-INV]Construction of Cable and Coil Testing System Using Liquid Helium for Electrical and Thermal Characterization of SCSC cables
*Yusuke Sogabe1, Kazuki Yasutake1, Naoyuki Amemiya1 (1. Kyoto University (Japan))
Keywords:
HTS cable,Liquid Helium,V-I Characteristics,Thermal characteristics
Spiral Copper-plated Striated Coated-conductor (SCSC) cables have a structure in which multiple layers of copper-plated multifilament coated conductors are wound around a cylindrical core. They feature low ac losses, high robustness, high mechanical flexibility, and high current capacity, and are expected to be used in applications such as rotating machines, accelerator magnets, and fusion magnets. To discuss the feasibility of these applications, it is important to evaluate the electrical characteristics (critical current and V-I characteristics) and thermal characteristics (quench and thermal runaway characteristics) of SCSC cables and coils wound with SCSC cables at temperatures lower than liquid nitrogen temperature. To date, the electrical and thermal characteristics at liquid nitrogen temperatures have been experimentally evaluated, but evaluations at lower temperatures have not yet been conducted.
To enable these measurements, we constructed a testing system that uses liquid helium targeting HTS cables and coils. In this testing system, liquid helium immersion cooling or conduction cooling by using liquid helium in gaseous helium environment can be used as the cooling method for the sample to be measured. During conduction cooling by liquid helium, the positive and negative current terminals of the sample are connected by a copper bar extending into the liquid helium accumulated in the lower part of the dewar. Since the current terminals are bypassed by the copper bar, current is diverted to the copper bar when the sample carrying the current. Therefore, the voltage across the copper bar is constantly measured and the current flowing through the copper bar is monitored during the measurements. In the conduction cooling conditions, the temperature is controlled using heaters and thermometers attached to the current terminals. The busbars were designed assuming a maximum current of 1 kA for dc and an amplitude of 2 kA for ac. Considering the temperature gradient inside the dewar, the busbars were graded so that the current density is low at the top and high at the bottom. In addition, the arrangement of the busbars and the sample positions were adjusted in anticipation of future experiments in which a magnetic field will be applied by an external magnet. This testing system aims to first demonstrate the high current capacity of SCSC cables in practical temperature ranges by conducting V-I characteristics measurements on the cables. Next, it aims to confirm that good current transport characteristics are obtained even when the SCSC cables are wound into small coils by conducting V-I characteristics measurements on the coils. We will present detailed results of the V-I characteristics measurements conducted on SCSC cables.
This work was supported in part by Japan-U.S. Science and Technology Cooperation Program in High Energy Physics, and in part by JST-ALCA-Next Program Grant Number JPMJAN24G1, Japan.
To enable these measurements, we constructed a testing system that uses liquid helium targeting HTS cables and coils. In this testing system, liquid helium immersion cooling or conduction cooling by using liquid helium in gaseous helium environment can be used as the cooling method for the sample to be measured. During conduction cooling by liquid helium, the positive and negative current terminals of the sample are connected by a copper bar extending into the liquid helium accumulated in the lower part of the dewar. Since the current terminals are bypassed by the copper bar, current is diverted to the copper bar when the sample carrying the current. Therefore, the voltage across the copper bar is constantly measured and the current flowing through the copper bar is monitored during the measurements. In the conduction cooling conditions, the temperature is controlled using heaters and thermometers attached to the current terminals. The busbars were designed assuming a maximum current of 1 kA for dc and an amplitude of 2 kA for ac. Considering the temperature gradient inside the dewar, the busbars were graded so that the current density is low at the top and high at the bottom. In addition, the arrangement of the busbars and the sample positions were adjusted in anticipation of future experiments in which a magnetic field will be applied by an external magnet. This testing system aims to first demonstrate the high current capacity of SCSC cables in practical temperature ranges by conducting V-I characteristics measurements on the cables. Next, it aims to confirm that good current transport characteristics are obtained even when the SCSC cables are wound into small coils by conducting V-I characteristics measurements on the coils. We will present detailed results of the V-I characteristics measurements conducted on SCSC cables.
This work was supported in part by Japan-U.S. Science and Technology Cooperation Program in High Energy Physics, and in part by JST-ALCA-Next Program Grant Number JPMJAN24G1, Japan.