Sand Cryostat -Instruction Manual

Introduction

The Sand Cryostat was developed as a simple and inexpensive system of temperature regulation for use specifically with the Four-Point Probe systems created by Colorado Superconductor, Inc. for controlled measurement of superconductivity versus temperature. Because of its simplicity, however, the Sand Cryostat is easily adaptable to most any application requiring a controlled temperature environment.

This instruction manual gives step-by-step procedures for the use of the Sand Cryostat with the CSI Four-Point Probe to determine the Critical Temperatures of the YBa2Cu3O7 and Bi2Sr2Ca2Cu3O10 superconductors. As noted above, these procedures can be adapted with minimal changes to suit many other temperature dependent experiments.

Instruction

  1. Assemble the equipment, connecting the Four-Point Probe, as shown in Figure 2, to the DMM's
  2. Place the probe into the cryostat chamber such that it is just above the bottom.
  3. Pour the sand into the cryostat chamber until it completely covers the probe.
  4. SLOWLY pour liquid nitrogen into the Sand Cryostat until it is at a visibly higher level then the sand. (allow a few minutes for the sand to reach a state of thermo equilibrium with the liquid nitrogen)
  5. Apply a current (<500 mA) across the black current probes (I14). The thermocouple should read 77K, and V23 should be zero.
  6. Watch the thermocouple readout. In a few minutes, most of the liquid nitrogen will have evaporated, and the temperature will begin to rise. This rise in temperature is slow enough to allow one to take a V23 measurement for each Kelvin increase in temperature.

The sand included with this kit has been washed to remove all fine dust that could damage the superconductor devices. It is a thermally stable material, and is readily accessible, making it an excellent medium for use in temperature control experiments like the Critical Temperature experiment described in this manual. The sand's physical properties also make it ideal for many other applications. Its potential as a medium of temperature control is limited only by your imagination.

Here are a few ideas and points to consider

  • The rate at which the sand changes temperature is approximately proportional to the surface area of the sand divided by the volume; in other words, by minimizing the surface area of the sand, you also minimize the rate of temperature change.
  • The sand can be heated to temperatures higher than room temperature by means of a microwave oven, but a conventional or lab oven would be more effective for heating to a specific temperature. The plastic design of the container, however will not stand temperatures above 100 Celsius. Caution should always be used when handing hot items.

Information Courtesy of CSI Superconductors