Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1508329 | Cryogenics | 2009 | 7 Pages |
Abstract
We report the performance of a helium circulation system (HCS) for a magnetoencephalography (MEG) that re-liquefies all the evaporating helium gas using two 1.5Â W GM cryocoolers operating at 4.2Â K. The MEG with the HCS was used to measure human brain responses for over one and a half years without any noise problems. The noise level is below 10 fT/Hz1/2 for 2-40Â Hz, below 30 fT/Hz1/2 at 1Â Hz, and 200 fT/Hz1/2 at 50Â Hz, which is the power supply frequency. As the amount of liquid helium used decreases less than one percent, the maintenance cost of the MEG becomes less than one-tenth of the previous cost.
Keywords
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Physical Sciences and Engineering
Materials Science
Electronic, Optical and Magnetic Materials
Authors
Tsunehiro Takeda, Masayoshi Okamoto, Kazuhiro Atsuda, Keishi Katagiri,