Abstract
Liquid-free cryogenic devices are acquiring importance in basic science
and engineering. But they can also lead to improvements in teaching low
temperature and solid-state physics to graduate students and specialists. Most
of the devices are relatively expensive, but small-sized equipment is slowly
becoming available. Here, we have designed several simple experiments
which can be performed using a small Stirling refrigerator. We discuss the
measurement of the critical current and temperature of a bulk YBa2Cu3O7−δ
(YBCO) sample, the observation of the levitation of a magnet over a YBCO
disc when cooled below the critical temperature and the observation of a phase
transition using ac calorimetry. The equipment can be easily handled by students
and also used to teach the principles of liquid-free cooling.
(Some figures may appear in colour only in the online journal)