Dear Dr. Grames,<br><br>It is a great news that you reached electron beam to the end of vacuum line.<br>It seems that all things for the PEPPo experiments go well.<br><br>I read your elogbook but I could not understand several things yet:<br>
<br>1. Is there any beam loss between Region 0 and Region 3 (10 nA <-> 2 nA)?<br><br>2. It seems that the beam momentum close to 6.9 MeV/c from spectrometer current (153 A).<br> how about its momentum from other measured point (ex, 5 MeV dipole)?<br>
<br>3. you mentioned that you did not use any QM in region 1 and solenoids in Regions 2 and 3.<br> what was happened when you turned them on?<br> how about beam size and shape on viewers at Region 3? <br> Is there no beam spreading due to un-compensated dispersion at Region 3?<br>
<br>4. In your log, you mentioned "I do however notice on the final viewer that the beam moves horizontally about 10% of beam spot size, beating against video."<br> Do you mean that the position jitter on the final viewer?<br>
During the measurement, were beam positions at Region 0 and 1 stable?<br> How about current jitter of power supplies for 5 MeV dipole and spectrometer?<br><br>We may discuss more during our next weekly meeting.<br>
<br>Sincerely yours,<br><br>Yujong Kim<br><br>
<br><div class="gmail_quote">On Mon, Feb 13, 2012 at 3:10 PM, <<a href="mailto:elogadm@jlab.org">elogadm@jlab.org</a>> wrote:<br><blockquote class="gmail_quote">
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<div><div><table><tbody><tr><td><a href="http://opsweb.acc.jlab.org/CSUEApps/elog/entry/1664890">1664890</a></td><td colspan="2">PEPPo: Beam to (nearly) end of vacuum line !!!</td>
</tr><tr><td width="200px;">13-Feb-2012 17:00</td><td width="350px;">J_Grames</td><td><a href="http://opsweb.acc.jlab.org/CSUEApps/elog/elog.php?logbook=ELOG">ELOG</a> | <a href="http://opsweb.acc.jlab.org/CSUEApps/elog/elog.php?logbook=POLOG">POLOG</a> | <a href="http://opsweb.acc.jlab.org/CSUEApps/elog/elog.php?logbook=PEPPOLOG">PEPPOLOG</a></td>
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<div><pre>I setup beam to PEPPo Region 1 using magnet settings from Jan 10; beam to 5D00 beam line viewer and 5D01 target viewer OK. </pre></div></div></div></div></div></div></div></div></blockquote><blockquote class="gmail_quote">
<div><div><div><div><div><div><div><div><pre>I then began checking Region 2 (spectrometer) and found the viewer Phil/I fixed 5D03 is again not making up the IN limit, so video also not making up - darn. I decided to use the viewer at exit of spectrometer 5D03A and scan spectrometer magnet current corresponding to span (140-160A) near our beam energy. In about 4 minutes a nice little beam spot appeared and a setting of 153A puts the beam dead center on viewer (see fig. 1).
The steering coil trims for Region 3 were supposed to be installed today, but won't go in until tomorrow AM. However, a beam at center of spectrometer exit viewer some ~6" beyond magnet means the beam should be exiting fairly parallel to entrance beam. So, I checked that the PEPPo FCUP was connected to it's picoammeter in ISB and then transported beam to final vacuum cross.
Voila - first beam to end of vacuum line too at a current of about 2nA. I verified this against FC1 (see fig. 2), where downward going brown trace is PEPPo FCUP beam and upward going black trace is same beam on FC1, where both are displayed with same 10nA FS range. Note, the vacuum (blue) is stable throughout and so is PS current (green), that is, beam stability was good on viewer.
Okay, since beam gets to PEPPo FC OK, I put in the final viewer and beam spot is very nice (see Fig. 3), although unfortunately the light doesn't appear to be working or bright enough. I do however notice on the final viewer that the beam moves horizontally about 10% of beam spot size, beating against video.
Interestingly, note that neither of the two quads, the capture solenoid or the transport solenoid are powered. Fig. 4 shows the 5 MeV dipole, steering coils and spectrometer setpoint used today. All magnets turned to their best off value.
This work also successfully was HCO w/ beam of picoammeter which appears to be working.
Beyond the punchlist below the next step would be transporting the ~few nA's through the vacuum window to the Compton polarimeter.
There are obviously things to fix:
1) Video 5D01 works, but is too dim
2) Viewer/video 5D03 does not insert, don't know if video works
3) Need Region 2 & Region 3 trims installed
4) Video 5D04 too dim
5) MPC5D02 magnet PS doesn't like going above 230A/11.5V, however it's at 300A/30V PS
</pre></div><div><br><b>Fig. 1 [02/13/2012 16:19:57]</b><br><img src="cid:a0d877d03883e691511d3d0efa6f440b"><br><b>Fig. 2 [02/13/2012 16:35:10]</b><br><img src="cid:3126b527bc111838254dceabff3b1780"><br><b>Fig. 3 [02/13/2012 16:43:50]</b><br>
<img src="cid:447bc15f2c4f7e4ee9af8fe211d3d834"><br><b>Fig. 4 [02/13/2012 16:51:17]</b><br><img src="cid:c4bd4c946c044b27695fb746c8ebe813"></div></div></div></div></div></div></div></div>
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