Mathew Brevard (Superconducting Systems/ IMRIS, USA)
LinkedIn: @Mathew Brevard, Bluesky: @superconductingsys.bsky.social
Abstract: Helium has a high cost, massive supply volatility, can be stressful to manage and carries a HUGE carbon footprint. High Field NMR requires superconductivity, but cryogen-free (CF)high field magnets have been in production for 3 decades and are considerably smaller and more efficient. We applied the latest CF technology to a full NMR system to establish the viability of this approach.
NMR was performed on a shielded, superconducting and persistent 89mm clear bore (rampable 0.5 to 9.4T) CF magnet and put it up to a rigorous set of NMR experiments to test performance and stability.
Testing with a Bruker AV3 and RS2D Console connected to a 20 Channel Bruker BOSS1 Shim and a 2H/1H/X BB 5mmx 16mm L Bruker probe. We ran spectra on a slew of standardized samples including: 0.1% Ethylbenzene, 1% Chloroform, Cyclosporin, Gramacidin, Quinidine, Heptanone and Cholesterol.
The system shimmed to superior levels with 0.1% Ethylbenzne producing full triplet and quadruplet splitting and an SNR of 495. Linewidth tests on 1% CHCL3 tests without spinning gave line widths of 0.26Hz @ 50%, 4 Hz @ 0.55% and 7Hz @ 0.11%. Spectra and 2D experiments for complex molecules have comparable performance to traditional NMR systems.
Results show that NMR in a fully cryogen-free magnet is fully viable. CF for routine high field NMR could substantially reduce the NMR communities reliance on non-renewable helium, reduce carbon emissions and also offer considerable space and energy savings over helium recapture systems.
Helium independence for High-Field MRI
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