English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

This chapter describes newly developed helium circulation system (HCS) for the magnetoencephalography (MEG) that re-liquefies all the evaporating helium gas using GM (Gifford-Macmahon) cryocoolers operating at 4.2 K. It consumes far less power than conventional systems which cannot be applied for MEGs because of their high noises. Warm helium gas at about 40 K collected high above the surface of the liquid helium in the dewar is used to keep the dewar cold, and cold helium gas just above the liquid helium surface is collected and re-liquefied while still cold. A special transfer tube with multi pipes has been developed to make the system operate efficiently. The system can produce up to 35.5 l/D of liquid helium from the evaporated helium. A MEG (PR2440 440 CH system, Yokokawa Electric Co. Ltd., Tokyo) with the HCS was used to measure human brain responses for several years without any noise problems. An improved HCS is now operating at Nagoya University, Japan. The noise level is below 10 fT/Hz1/2 for 2-40 Hz, below 30 fT/Hz1/2 at 1 Hz, and 200 fT/Hz1/2 at 60 Hz, which is the power supply frequency. The maintenance cost of the MEG has become less than one-tenth of the previous cost.

Helium Circulation System (HCS) for the MEG