[RASMB] Elevated temperature operation with a turbomoledcular pump.

[Dror Noy]

Dear Walter and RASMBers,
Our department's XL-A suffers from a similar fogging problem as  
diffusion pump oil condenses on the lamp and reduces its UV intensity  
dramatically.
I wasn't aware of the temperature dependence of  this problem so I'm  
going to test that too. Anyway, we are working at higher temperatures  
and would be very interested in solving this problem. However, we have  
to consider the cost of such upgrade.
Dror

On 11/03/2005, at 19:18, Walter Stafford wrote:

> Dear RASMB-ers
>
>         I have been testing a turbomolecular pump as a replacement for  
> the standard diffusion pump on the XL-I. I am writing to report the  
> results of that experiment.
>
> On my machine, with the standard diffusion pump installed, I have not  
> been able to run above about 23 degrees without having serious fogging  
> of the interference condensing lens after about 15 minutes, making it  
> impossible to take data.
>
> About a month ago, with the help of the Beckman Serviceman and folks  
> from the Axiden Division of Alcatel Vacuum Technology  
> {http://www.adixen-usa.com/}, we installed an ATP80 TMP in place of  
> the diffusion pump. Other than a flange that had to be machined to  
> mate the TMP to the diffusion pump flange, it was a direct  
> replacement. The original rough pump was used to back up the TMP.   
> see:  
> {http://www.adixen.com/all/dyn/products/products.php?id_prod=20&lg=us}
>
> So far the results have been quite remarkable. After the first test of  
> running for 4 days at 40 degrees, the optics were clean. The chamber  
> was actually cleaner after the run than before. The TMP seemed to have  
> removed all the residual oil that we were unable to remove after  
> replacing the diffusion pump. It pumps down to 3-5 micons in less than  
> 5 minutes and ultimately to about 1-2 microns. The fringe patterns  
> seem to be more stable (not sure exactly why, but I was informed that  
> the regular diffusion pump heater normally cycles on and off; the  
> flexing associated with that may explain it).
>
> We use it routinely now for all runs and couldn't be happier with it.
>
> Several labs have expressed an interest in installing one on their  
> machines.
>
> However, Beckman will not support the pump or provide one as standard  
> equipment unless there is sufficient interest. A proper, Murphy-proof  
> installation would require a firmware change and field service support  
> to allow it to be included under the service contract and warranty.
>
> I would like to take a survey of those who might be interested, so  
> that we can convey that expression of interest to Beckman.
>
> If you have an interest and think that running at higher than 20  
> degrees or higher precision might be useful to you, please respond to  
> this email by replying to the RASMB. I'll collect the responses and  
> comments and forward them to the folks at Beckman.
>
> It has opened new vistas for our research.
>
> Thanks
> Walter
> --  
>
> ####################################################################### 
> #
>
> Walter F. Stafford III, Ph.D.
> Analytical Ultracentrifugation Research Laboratory
>  Senior Scientist
>  Boston Biomedical Research Institute
>  64 Grove Street
>  Watertown, MA  02472-2829
>
>  main:(617) 926-8040
>  tel: (617) 658-7808
>  fax: (617) 972-1753
>
>  mailto:stafford at bbri.org
>
> http://www.bbri.org/faculty/stafford/Stafford.html
> #################################################################
>
=========================
Dror Noy, Ph.D.
Structural Biology Dept.
Weizmann Institute of Science
Rehovot 76100
Israel

e-mail: dror.noy at weizmann.ac.il
Tel: (972)-8-934 2525
Fax: (972)-8-934 4154