A cryopump for obtaining ultra-high vacuum

✍ Scribed by N.N. Baeva; N.P. Danilova; A.I. Shal'nikov

• Publisher: Elsevier Science
• Year: 1968
• Tongue: English
• Weight: 210 KB
• Volume: 8
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/s0011-2275(68)80054-2

✦ Synopsis

always at room temperature by an external circuit in wliich dry air is circulated at variable pressure (see Figure 1). The design of the NMR probe permits the rapid change of samples as well as their rotation around an axis perpendicular to the constant magnetic field and parallel to the radio frequency field. Also, the probe can be used for measurements in zero magnetic field; in such cases the cables between the measuring coil and the oscillator can be shortened to a few centimetres.

Testing and operational experience

The temperatures obtained by the system in testing and actual operation extend from -195 to +250°C. The heater with plastic foam insulation allows setting of any temperature from -195 to +60°C; that with perlite insulation from +20 to +250°C. The lowest measured sample temperature exceeded the temperature of liquid nitrogen by about 0-5-2°C. Switching off the electronic control, i.e. for zero heating current, the stability of the sample temperature was found to be ± l°C/h. With the electronic control on, the stability increases to ±0-rC/h, as shown in Figure 4.

If the temperature is varied during operation, the new steady state can be reached within less than 5 min.