Hello Spinlanders,
How do you deal with the temperature extremes of magic-angle spinning experiments?
On our Bruker 800 MHz system with 1.3 mm standard bore MAS probe, we cool the VT gas with a BCU-Xtreme. At a set point of 238 K and the max VT gas flow of 2000 l/hr, we reach an actual sample temperature of ~292 K. We apply dry flush gas to the shim coils, which keeps them at least 5 degrees above freezing.
We want to go colder in sample temperature to ~275K, which brings me to my two questions:
1. Is there a cooling option besides using a liquid nitrogen exchanger or evaporator? My thinking is that refills could be problematic for longer-term experiments. Is there a way to cool the bearing or drive gas using a second BCU-X or chiller?
1. How do you protect the magnet flanges? By going colder, I expect the shims will drop below 273 K, although Bruker's VT guide (Z33073) suggests this is OK. My bigger concern is the magnet flanges. Is there any risk of freezing them? Is there a way of monitoring their temperature during the experiment?
Thanks very much,
Sameer
--
Sameer Al-Abdul-Wahid, Ph.D.
Manager, Nuclear Magnetic Resonance Centre
University of Guelph
50 Stone Road East, Guelph, ON N1G 2W1
Tel: 519-824-4120 x58914<tel:519-824-4120%20x58914>
Web: http://nmr.uoguelph.ca/
Received on Tue Mar 07 2017 - 12:02:16 MST