Hi All,
I would like to thank everyone who provided their two cents to my question, in particular, John Decatur, Mark Swanson, Andew Lewis, Dean Olson, Sarah Cady, Vadappuram Chacko, Jerry Hirshinger, Atilano Carrillo, Jerry Dallas, Jiadi Xu, Boris Itin, Tony Montina, Glenn Facey, Karen Ann Smith, Daniel Rentsch and Paul Cope.
The general consensus is leaning more towards getting a SB magnet/probes to reduce hassles and problems. There seems to be mixed reviews about the performance and maintenance of using a WB magnet for liquids experiments and I have summarized the responses below:
- Magnet:
- WB magnets are more expensive than SB.
- WB magnets have more superconducting wire to keep cold, therefore more cryogens are used
- Current technology has made SB solids probes high performers which may have manufacturers dialing back their WB magnet production and reserved more for DNP systems.
- Could put a DNP system with the WB magnet in the future
- With SB magnet, can have a liquids autosampler since the upper shim stack is not being changed on a regular basis.
- Probes:
- WB solids probes provide more space for electronics for broad band channels, larger stators (> 4mm) and can handle wider temperature ranges.
- SB solids probes now a days can handle the high powers required for solids experiments. However, have a narrower tuning range/fixed frequency, stator for 4 mm rotors or less, lower power limits
- WB liquids probes do exist, but are older generations.
- WB shims with SB probe:
- Current Bruker magnets: WB 28 shim gradients, SB 36 shim gradients
- WB shims do not provide the high homogeneity needed for hi-res probes such as BBO SmartProbe
- Topshim does not work well, if not at all, for SB liquid probe using collars in the WB shim stack, must manually shim
- Shimming on a WB system is a bit more sluggish due to the larger shim coils and large currents.
- Shims are stable
- SB shim insert into WB shims:
- Narrow bore shim stacks can be inserted into WB shim stacks. When doing so, need to wait overnight for residual currents to stabilize.
- Some people are unable to get good shims with this setup where as some can get great shims. Seems like hit or miss.
- Probe switching
- Collars can fit onto SB probes to be positioned in WB shims.
- Getting the right position with the collars might be difficult for some. Some users would have to reshim as if it were a new probe.
- Upper bore insert must be changed to accommodate shuttling of samples
- Performance:
- The resolution and sensitivity seems to vary depending on how well the shims can be. There seems to be a split down the middle on overall performance of using SB liquids probes in WB magnets.
- Some say it's better to get a SB shim stack that fits into the WB shims, but the many have also had great experiences with just the WB shims.
- Cryprobe users:
- We will not looking into getting a cryoprobe or prodigy probe for this system, but there are a few facilities that share split time between solids and cryoprobes.
- The main hassle with this type of setup is the time required for warmup the cryprobe before removal and the preparation for reinserting when done with solids. The cool down and reshimming of the cryoprobe could take up to a day.
Thanks again,
Joel
From: Joel Tang [mailto:joel.tang_at_jhu.edu]
Sent: Thursday, January 07, 2016 1:52 PM
To: ammrl_at_ammrl.org
Subject: AMMRL: liquids NMR performance with WB magnets
Dear AMMRLers,
We are looking into adding to our fleet of instruments a Bruker system that can do both liquids and solids experiments and I am thinking about whether we should get a standard or wide bore magnet. The wide bore solids probes have better capabilities/configurations than their narrow bore equivalents which makes them more appealing to get. Since we plan on having liquids capabilities as well, and I am not aware of any WB liquids probes, I am curious about the performance of standard liquids probes in wide bore magnets. I know that using special collars with the narrow bore probes will help center and position the coil, but I am wondering if anyone has had issues related to shimming, resolution, sensitivity etc. or any other things that should be of concern. Also, is there a significant difference with cryogen boil off and hold time of WB magnets compared to standard bore magnets. I would greatly appreciate it if anyone can share their knowledge and experiences with such a setup.
Regards,
Joel
------------------------------------------
Joel A. Tang, Ph.D
Core Facility Manager - NMR,
Department of Chemistry
Johns Hopkins University
tel: 410-516-7456
nmr.chm.jhu.edu
Received on Mon Jan 11 2016 - 07:06:51 MST