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Dear Walter,<br>
<br>
thank you for going into this. The fogging problem has been an issue here
as well. If we have not been confronted with this problem for some time
it's mainly due to the fact that we have been sticking to 20 degrees most
of the time.<br>
<br>
Our serviceman had always stressed his own attempts to have Beckman
resolve this issue; I think his suggestion was to introduce a cooling
trap. However, I feel that your solution should be somewhat easier to
handle.<br>
<br>
I would be definitely interested in implementing this improvement; as the
others, I would also be eager to learn what costs would be connected with
this.<br>
<br>
Regards,<br>
Kristian<br>
<br>
At 12:18 11.03.2005 -0500, you wrote:<br>
<blockquote type=cite cite>Dear RASMB-ers<br>
<br>
<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.<br>
<br>
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.<br>
<br>
About a month ago, with the help of the Beckman Serviceman and folks from
the Axiden Division of Alcatel Vacuum Technology<font size=1>
{<a href="http://www.adixen-usa.com/" eudora="autourl">http://www.adixen-usa.com/</a></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 size=1> see:
{<a href="http://www.adixen.com/all/dyn/products/products.php?id_prod=20&lg=us" eudora="autourl">http://www.adixen.com/all/dyn/products/products.php?id_prod=20&lg=us</a></font>}<br>
<br>
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).<br>
<br>
We use it routinely now for all runs and couldn't be happier with
it.<br>
<br>
Several labs have expressed an interest in installing one on their
machines.<br>
<br>
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.<br>
<br>
I would like to take a survey of those who might be interested, so that
we can convey that expression of interest to Beckman.<br>
<br>
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.<br>
<br>
It has opened new vistas for our research.<br>
<br>
Thanks<br>
Walter<br>
<br>
<pre>--
</pre><font face="Courier New, Courier"></font><font color="#0B0963">########################################################################</font><br>
<font color="#0B0963">Walter F. Stafford III, Ph.D.</font><br>
<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>
<a href="mailto:stafford@bbri.org" eudora="autourl">mailto:stafford@bbri.org</a><br>
<a href="http://www.bbri.org/faculty/stafford/Stafford.html" eudora="autourl">http://www.bbri.org/faculty/stafford/Stafford.html</a></font><br>
<font color="#0B0963">#################################################################</font></blockquote><br>
<br>
<br>
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