Magnet heating

[lsanches@oksurg.com]

While stuck on a vessel on the west coast as a result of the longshoreman' s strike our brand new magnet warmed down or up. Apparently the magnet has to be taken through what were being told is a cool down process. Can you explain what this is and how the integrity of the magnet may be affected?

[aelster]

(02-02-2015 02:30 AM)lsanches@oksurg.com Wrote:  While stuck on a vessel on the west coast as a result of the longshoreman' s strike our brand new magnet warmed down or up. Apparently the magnet has to be taken through what were being told is a cool down process. Can you explain what this is and how the integrity of the magnet may be affected?

MR magnets are often “cold shipped” from the factory -- meaning they are pre-cooled by being pre-filled with liquid helium. There is no current in the coils so there is no magnetic field, but the coils are cold enough to be superconducting. Having helium on board stabilizes the system and saves appreciable time during installation. If a long shipping time is anticipated (such as transatlantic by boat) a battery powered helium circulation pump may also attached that can keep the system cooled for 10-14 days.

If sitting for a longer period of time or without a pump, some of this helium probably boiled off as the magnet increased back toward ambient temperatures. Thus they had to re-cool your magnet when it finally made it to your site, making for a slightly longer installation process and the need for more liquid helium than would have been otherwise. The integrity of your magnet should not have been compromised by this event. -- ADE

[lassad]

I HAVE A MRI SIGNA HDXT INSTALLE OF THEN 2010, A QUENCH HAPPENS I WOULD LIKE TO KNOW WHICH LEVEL OF heluim produces a quench, in fact it went from 56.4 to 22.4 heluum in 25 days then a quench occurs