Greetings All,
As usual, responses from this community flowed in fast and furious. Many thanks to all who responded (in no particular order): Dave Horita, Phil Dennison, Greg Heffron, Brian Cherry, Tara Sprules, David VanderVelde, Andrew Lewis, Martha Morton, Bob Berno, Jerry Hirschinger, Clemens Anklin, John Snyder, and Torbjörn Astlind.
First, a few general notes and observations. First, assuming we get funding, we haven't decided on Bruker vs. Agilent yet. Due to where we need to locate things, we're almost certainly looking at a water cooled unit.
The helium compressor, certainly the water cooled ones, isn't the noisiest part of a cryoprobe installation. In general the Cryoplatform or CCC (depending on which vendor) makes more noise. Noise is also transferred along/through the helium lines that run to and from the compressor. Newer helium compressors are quieter than older models, and from responses I received it seems that both vendors are using the same He compressors in their newest systems.
It was also noted several times that Bruker's system is overall quieter than Agilent's. It seems this comes down mostly to choices made to insulate/soundproof various parts of the system or not. In the case of Bruker's cryoprobe system, the interior walls of the Cryoplatform are covered in egg-crate style foam and the helium lines are wrapped in foam insulation. Several responders strongly suggested that if we get an Agilent system simply getting foam pipe insulation from the hardware store and wrapping the He lines makes a significant difference.
Before I list the "true" answers, I also want to note that Clemens mentioned that Bruker's N2 cooled Prodigy probe system makes no noise and costs less both up front and in terms of maintenance and still provides a good improvement in performance vs. room temperature probes. This probably isn't an option for us – if we get a grant we'll be going all out – but if quiet is more important than absolute sensitivity it's a great option.
So, what are the options? Nobody seems to use any sort of pre-manufactured system. If possible, a liquid cooled compressor is quieter than air cooled. All the DIY options will work better if you line them on the equipment side with some sort of soundproofing material. There are several options in use:
1) Cheapest and somewhat effective, simply putting a good sized piece of sound-deadening insulation on the wall directly behind the compressor will cut down on reflected noise. This also works behind a console placed near a wall to dampen how much fan sound you hear in the lab.
2) Some sites have constructed a partial wall in front of or around their compressors. It doesn't have to be full ceiling height. This is very easy and you can just walk around or push it out of the way to gain access. Since it's not tight to the unit, it preserves air flow.
3) Build a box. The main things here are that it needs some ventilation (not much for liquid cooled units) and holes for all the lines – water, helium, and electric. The two designs mentioned are a box that simply sets over the unit and lifts off and a 3 part box with 2 "L" shaped sides that connect together and a lid. The latter is probably easier to deal with long term. Using relatively heavy plywood or MDF should work fine. Any holes for ventilation should be baffled. A fan to improve airflow is optional.
Cheers,
Andrew
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C. Andrew Fowler, Ph.D. | University of Iowa
Associate Director | B291 CBRB, 500 Newton Rd.
CCOM NMR Facility | Iowa City, IA 52242
319-384-2937 (office) | 319-335-7273 (fax)
andrew-fowler_at_uiowa.edu
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Received on Wed Jan 29 2014 - 06:38:40 MST