Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets

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Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
1998
Major/Subject
Mcode
Degree programme
Language
en
Pages
3418-3425
Series
Review of Scientific Instruments, Volume 69, Issue 9
Abstract
In high resolution continuous-wave nuclear magnetic resonance(NMR) work well-reproducible, linear sweeps of current are needed. We have developed a microcontroller based programmable current supply, tested with superconducting magnets with inductance of 10 mH and 10 H. We achieved a resolution and noise of 4 ppm. The supply has an internal sweep with programmable ramping rate and a possibility for remote operation from a computer with either GPIB or RS232 interface. It is based on an 18-bit D/A converter. The maximum output current is ±10 A, the sweep rate can be set between 1 μA/s–140 mA/s, and the maximum output voltage is ±2.5 V. In work at ultralow temperatures, especially in superconducting quantum interference device NMR, all rf interference to the experiment should be avoided. One of the sources of this kind of unwanted input is the digital switching noise of fast logic devices. We discuss this problem in the context of our design.
Description
Keywords
superconductors, NMR, superconducting magnets
Other note
Citation
Koivuniemi, Jaakko & Luusalo, Reeta & Hakonen, Pertti J. 1998. Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets. Review of Scientific Instruments. Volume 69, Issue 9. 3418-3425. ISSN 0034-6748 (printed). DOI: 10.1063/1.1149109