Design of an Insert to Characterize Superconducting Materials at 4.2 K Using a Cryocooler System
Temperature Superconductors (HTS) are potential candidates in magnet design for high
energy physics and fusion reactors due to their high electrical performance in high
magnetic fields. It is necessary to characterize HTS conductors at 4.2 K so that their
properties are well known for use in magnet applications. This work focused on the
design, analysis and testing of an ... read moreexperimental probe able to measure the critical
current of high temperature superconductors at low temperatures (down to 4.2 K). The
test probe was designed for use in a two stage Gifford-McMahon Helium gas cryocooler.
The probe provides the necessary flexibility so that different measurements can be
performed for the electromechanical characterizations of superconductors: critical
current, Residual Resistivity Ratio (RRR) and mechanical loading effects. Preliminary
cool down experiments showed that the cryocooler was incapable of reaching the desired
temperature of 4.2 K with the experimental probe mounted inside. An analytical study of
the system was undertaken to identify the potential causes of those results. Heat
conduction was found to have the major effect on the temperature of the structure. A
finite element analysis was conducted in parallel with experiments to further
investigate the heat conduction effect and to identify the thermal limitation of the
system. Copper and G10 rods were tested to evaluate the thermal response of materials
with different thermal conductivity. Experiments were also conducted on the test probe
with a few structural modifications (reduction of the number of support rods and the
addition of radiation shields). The results showed that even though using materials with
low thermal conductivity helps achieve lower temperatures, heat conduction along the
structure prevents the system from reaching temperatures as low as 4.2
Thesis (M.S.)--Tufts University, 2016.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Luisa Chiesa.
Committee: Jeffrey Guasto, and Makoto Takayasu.
Keyword: Mechanical engineering.read less