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Dear Folks,<br>
<br>
It is entirely possible that the Beam Current Monitors are badly
calibrated at currents of 0.3 nA. See emails below.<br>
<br>
- Larry<br>
<br>
-------- Original Message --------
<table cellspacing="0" cellpadding="0" border="0" class="moz-email-headers-table">
<tbody>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject: </th>
<td>Fwd: Re: Fwd: bcms</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Thu, 15 Dec 2011 17:02:38 -0500</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>Stepan Stepanyan <a href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>Weinstein, Lawrence B. <a href="mailto:lweinste@odu.edu"><lweinste@odu.edu></a></td>
</tr>
</tbody>
</table>
<br>
<br>
Dear Larry,<br>
<br>
Here is the response from Arne. When we measure 0.3 nA, TPE had
higher currens.<br>
<br>
Regards, Stepan <br>
<br>
-------- Original Message --------
<table cellspacing="0" cellpadding="0" border="0" class="moz-email-headers-table">
<tbody>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject: </th>
<td>Re: Fwd: bcms</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Thu, 15 Dec 2011 16:45:18 -0500</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>Arne Freyberger <a href="mailto:freyberg@jlab.org"><freyberg@jlab.org></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>Stepan Stepanyan <a href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a></td>
</tr>
</tbody>
</table>
<br>
<br>
I suggest that a beam test be performed. 0.3nA is below the
specifications. The fact that they work at all for these low
currents was kind of a surprise. But by optimizing the lock-in
amplifiers for such low currents they might be useful for current
measurements. They will have to be cross calibrated against the
FCUP. Not sure what range the calibration for FCUP covers, so that
too might have to be adjusted.<br>
<br>
Arne<br>
<br>
On 12/15/2011 04:02 PM, Stepan Stepanyan wrote:
<blockquote type="cite" cite="mid:4EEA6066.2060303@jlab.org">
Hi Arne,<br>
<br>
Do you have any idea how well BPMs measure these low currents.<br>
<br>
Thanks, Stepan<br>
<br>
-------- Original Message --------
<table cellspacing="0" cellpadding="0" border="0" class="moz-email-headers-table">
<tbody>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Subject:
</th>
<td>bcms</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Date: </th>
<td>Thu, 15 Dec 2011 14:46:42 -0500</td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">From: </th>
<td>Larry Weinstein <a href="mailto:lweinste@odu.edu"><lweinste@odu.edu></a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">Reply-To:
</th>
<td><a href="mailto:weinstein@odu.edu">weinstein@odu.edu</a></td>
</tr>
<tr>
<th valign="BASELINE" nowrap="nowrap" align="RIGHT">To: </th>
<td>stepan Stepanyan <a href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a></td>
</tr>
</tbody>
</table>
<br>
<br>
<pre>Dear Stepan,
How precise are the beam current monitors for currents of 0.3 nA? How
well do they determine the integrated current? 1%, 10%, 50%?
--
Sincerely,
Larry
-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
<a href="mailto:weinstein@odu.edu">weinstein@odu.edu</a>
<a href="http://www.lions.odu.edu/%7Elweinste/">http://www.lions.odu.edu/~lweinste/</a>
</pre>
</blockquote>
<br>
<pre cols="72" class="moz-signature">--
Arne Freyberger
Director of Accelerator Operations
Jefferson Lab Office: (757) 269-6268
12000 Jefferson Avenue Cell: (757) 876-6289
Newport News, VA 23606 Email: <a href="mailto:freyberg@jlab.org">freyberg@jlab.org</a>
</pre>
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