The squid picovoltmeter operating in magnetic fields up to 3.2 T

✍ Scribed by L. Smrčka; P. Středa; P. Svoboda

• Publisher: Elsevier Science
• Year: 1978
• Tongue: English
• Weight: 435 KB
• Volume: 18
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(78)90050-4

✦ Synopsis

A method which enables the Squid dc voltmeter to be operated with a sample exposed to a significant external magnetic field is presented. A special superconducting shield with a finite time constant has been used to suppress time-dependent components of the field. With the shield, the Squid voltmeter has been able to work in magnetic fields up to 0.7 T in the flux-locked loop mode. The total voltage noise per unit bandwidth Vrm s (referred to input) does not exceed the value of I x 10 -12 V Hz -1/2. To extend the range of performance to higher magnetic fields, simple Iow pass filters have been built into the input circuit to increase its time constant. With the signal coil of the Squid shunted by a resistor R e = 3 x 10 -6 ~, the Squid voltmeter could be operated in fields up to 3.2 T with Vrms~ 1.