Temperature stabilized adiabatic demagnetization for space applications

✍ Scribed by P. Kittel

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 397 KB
• Volume: 20
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(80)90097-1

✦ Synopsis

This note describes a possible solution to the training problems that have been observed in many superconducting coils. In particular the proposed technique should apply to bath-cooled coils that are not designed to recover thermally from a small normal region. As a result these coils quench, but they are protected by an external protection circuit, which allows them to quench safely.

The quenches in these coils are probably initiated by energy releases associated with conductor motion or with breaks in the bond between conductors or between a conductor and another material, such as a glass fibre. The training of these coils, in which the quenches occur at higher and higher currents is presumably a process of stressing the coil and breaking stronger and stronger bonds, with the coil quenching after some of the breaks. This process is lengthy and expensive as many quenches may occur before the coil attains the desired current. After the coil has been trained it may be warmed to room temperature and recooled to liquid helium temperature without needing to be retrained; or at most a considerably reduced training cycle is necessary.

The time and refrigeration capacity required for recooling the coil after it has quenched are the major expense items associated with the training process. A method is needed for testing/training coils in which the various internal effects that cause a quench, occur while the quench itself, and thus the expensive after-effects, are avoided.