An Ultra-low Vibration Helium Reliquefier for Dual-Helmet Magnetoencephalography (MEG)

27th International Cryogenics Engineering Conference and International Cryogenic Materials Conference 2018

Wang, C.^1 ; Olesh, A.^1 ; Lee, Y.H.^2

Cryomech Inc., 113 Falso Drive, Syracuse

NY

13211, United States^1

KRISS, Daejeon

305-600, Korea, Republic of^2

关键词: Magnetic interference;    Magnetically shielded room;    Maintenance free;    Noise cancellation;    Prototype tests;    Pulse tube cryocoolers;    Signal quality;    Vibration reduction measures;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/502/1/012137/pdf
DOI  :  10.1088/1757-899X/502/1/012137

来源: IOP

【 摘 要 】

An ultra-low vibration helium reliquefier has been developed that can be integrated into an innovative magnetoencephalography (MEG) system with dual helmets for adult and pediatric use. The compact reliquefier establishes a closed-cycle helium loop for the MEG dewar allowing for uninterrupted, maintenance-free operation. The reliquefier, employing a Cryomech 4 K pulse tube cryocooler (model PT420), provides a liquefaction rate of 21 L/day from room temperature helium gas. Several vibration reduction measures have been applied to the system. The reliquefier incorporates a ∼1.5 m long, horizontal, flexible liquid return line allowing it to be mounted outside of the magnetically shielded room (MSR). This arrangement greatly reduces vibrational, acoustic, and magnetic interference. In the prototype tests, this setup reached noise levels of ∼18 fT/ÖHz without the use of noise cancellation software. The spontaneous brain activity signal showed nearly identical signal quality with the reliquefier turned on and off.