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--></style><title>Elevated temperature operation with a
turbomoledcular pump</title></head><body>
<div>Dear RASMB-ers</div>
<div><br></div>
<div><x-tab> </x-tab>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.</div>
<div><br></div>
<div>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.</div>
<div><br></div>
<div>About a month ago, with the help of the Beckman Serviceman and
folks from the Axiden Division of Alcatel Vacuum Technology<font
face="Lucida Grande" size="-4" color="#000000">
{http://www.adixen-usa.com/</font>}, 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. <font face="Lucida Grande" size="-4" color="#000000"> see:
{http://www.adixen.com/all/dyn/products/products.php?id_prod=20&l<span
></span>g=us</font>}</div>
<div><br></div>
<div>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).</div>
<div><br></div>
<div>We use it routinely now for all runs and couldn't be happier with
it.</div>
<div><br></div>
<div>Several labs have expressed an interest in installing one on
their machines.</div>
<div><br></div>
<div>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.</div>
<div><br></div>
<div>I would like to take a survey of those who might be interested,
so that we can convey that expression of interest to Beckman.</div>
<div><br></div>
<div>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.</div>
<div><br></div>
<div>It has opened new vistas for our research.</div>
<div><br></div>
<div>Thanks</div>
<div>Walter</div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div><font
color="#0B0963"
>####################################################################<span
></span>####</font><br>
<font color="#0B0963"></font></div>
<div><font color="#0B0963">Walter F. Stafford III, Ph.D.</font></div>
<div><font color="#0B0963">Analytical Ultracentrifugation Research
Laboratory<br>
Senior Scientist<br>
Boston Biomedical Research Institute<br>
64 Grove Street<br>
Watertown, MA 02472-2829<br>
<br>
main:(617) 926-8040<br>
tel: (617) 658-7808<br>
fax: (617) 972-1753<br>
<br>
mailto:stafford@bbri.org<br>
</font></div>
<div><font
color="#0B0963">http://www.bbri.org/faculty/stafford/Stafford.html</font
></div>
<div><font
color="#0B0963"
>#################################################################</font
></div>
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