Abstract
We have developed a liquid helium recondensing system for MEG used in a laboratory environment. The system has a separable supplying structure using a liquid helium container in order to avoid the noise increase and to simplify the installation. We conducted an unloaded test of the system using a calorimeter which has a vacuum vessel, radiation shield, liquid helium vessel, temperature sensor, heater and pressure sensor. The meter can measure a stand-alone liquid helium recondensation rate by stabilizing the liquid helium in the vessel at saturation temperature using the heater. We found that the stand-alone recondensation rate was 9.7 L/day. We also conducted a performance test loaded with a 100 L liquid helium container, and found that the recondensation rate was 7.9 L/day. To evaluate the system in operation with MEG, we measured a noise in MEG and auditory evoked magnetic fields (AEF). The results showed that a noise increase in MEG was not observed and AEF was not influenced by the operating noise of the system. From these evaluation results, we found that the recondensing system with a separable liquid helium supplying structure was useful for MEG operation.
