Cryogenic FTMS

FTMS has traditionally been constructed on large, horizontal, room temperature bore magnets, but if it is possible to construct the FTMS in the 4.2K cold bore of a superconducting magnet, several important advantages will be achieved.

First, the vacuum system will cryopump itself so the base pressure will be in the <1012 mbar range and the pumping speed will be in the 105 l/sec range. Second, the cold vacuum system walls can be placed in thermal contact with the input resistors of a preamplifier. This will reduce thermal Johnson noise by a factor of 8.4 relative to room temperature operation which increases sensitivity and dynamic range by the same amount. Third, the vacuum system can be constructed in a 1″-2″ diameter bore which allows the use of NMR-style magnets for FTMS. Thus, the high field NMR magnets up to 23.3T can be used for FTMS without any change to the fundamental coil design.

The original design of a cryoFTMS system was discussed in the reference below.

O’Connor, P. B. Considerations for the Design of a Fourier Transform Mass Spectrometer in the 4.2K Cold Bore of a Superconducting Magnet Rapid Commun Mass Spectrom 2002, 16, 1160-1167. Link

To Download some recent pictures of the cryogenic FTMS vacuum chamber, click here.

After overcoming substantial electrical and mechanical engineering obstacles, the 14 T cryogenic MALDI-FTMS instrument has finally achieved first signal. The press release can be found here. The reference below describes this research in detail.

Lin, C.; Mathur, R.; Aizikov, K.; O’Connor, P. B. First Signal on the Cryogenic Fourier-Transform Ion Cyclotron Resonance Mass Spectrometer J. Am. Soc. Mass Spectrom. 2007, 18, 2090-2093. Link

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