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Entry time:	Mon Mar 31 07:02:38 2025
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<p>On 21/02/2018 we reattempted the beam tuning. We expected this to be easier now the rogue mylar is removed from the beamline.</p> <p>At 8:30 we started the roughing pumps. At 8:37 the turbos were switched on. By 8:55 the preassures read: Up = 1.6e-5, and Down = 4.3e-5 mBar.</p> <p>The preamp box was mounted on top of the chamber ready, the box lid was still left off.</p> <p>The S2 was biased to -130.3V, leak current = 1.03 uA.</p> <p>On FAIR DAQ with no beam: Trigger Rate ~ 8000/s, Event Mult = 5.0</p> <p>The 10mm blank frame was in the beam axis. We began beam tuning. By 11:30 we had beam on the downstream faraday cup FC-E1 = 40pA, so now we can pass beam through the chamber - good!</p> <p>We moved the target ladder to 95.010mm, swapping from the blank 10mm frame to the blank 3mm frame to assist in beam tuning. Now FC-E1 ~ 8pA.</p> <p>We decided to move back to the 10mm frame to optimise tuning. The target ladder was moved back to position 80.024mm for this purpose.</p> <p>We moved the slits located upstream from the bending magnet (close to FC-4) to 1.5X1.5mm.</p> <p>We moved the GSI slits located before the quadrupole to optimise current on FC-0, the upstream faraday cup. We find the following slit positions:</p> <p>Up = 0mm, Right = 1.5mm, Down = 5.5mm, Left = 5.5mm.</p> <p>We also performed further tuning by adjusting the quadrupoles located at the immediate end of the tandem accelerator - note the beam tuning is very sensitive here.</p> <p>After beam tuning we had the following currents:</p> <p>For 10mm blank frame in beam axis: FC0 = 42pA, FCE1 = 30pA, transmission ~ 71%</p> <p>For 3mm blank frame in beam axis: FC0 = 41pA, FCE1 = 13pA, transmission ~ 32%</p> <p>We decided this was acceptable for testing</p> <p> </p> <p>At 13:30 we switched off the S2 and vented the chamber.</p> <p>After venting we did the following:</p> <ul> <li>Removed 12um mylar from the front of the S2</li> <li>Visually inspected the ribbon cable connections on the S2 connector and the vacuum feedthrough connector. I saw no loose connection and left the cable alone.</li> <li>Set the Si diode angle to 62 degrees relative to the beam axis (28 degrees relative to the normal of the beam axis) - in future we need a fixed angle mount to ensure this angle is reproducible</li> <li>Mounted targets on the ladder at the following positions:</li> </ul> <table border="1" cellpadding="1" cellspacing="1" style="width:500px"> <tbody> <tr> <td><strong>Position</strong></td> <td><strong>Target</strong></td> </tr> <tr> <td>1</td> <td>Blank 3mm</td> </tr> <tr> <td>2</td> <td>Blank 10mm</td> </tr> <tr> <td>3</td> <td>CH2 I</td> </tr> <tr> <td>4</td> <td>CH2 II</td> </tr> <tr> <td>5</td> <td>CH2 III</td> </tr> <tr> <td>6</td> <td>CH2 VI</td> </tr> <tr> <td>7</td> <td> <p>natC I</p> </td> </tr> </tbody> </table> <p>The target ladder was set to position 3, looking from above I confirmed it was in the center of the beam axis.</p> <p>The alpha source was removed as someone pointed out the ladder may be moved in such a way that beam hits the source. However later on (morning of 22/02/2018) I was informed this is being over cautious and we can leave the source at the far position 7 of the ladder during beam.</p> <p>The ladder, downstream, and upstream lids were remounted on the chamber. The S2 (no mylar) was still on the downstream lid. The diode was still on the central lid.</p> <p>The roughing pumps were switched on. However the following mistake was made: when both Ecodry 1 and Ecodry 2 were switched on, the automatic gate valve for Ecodry 1 was still open. This meant the chamber was evacuated at a fast rate, likely > 10mBar/s. When I noticed this after a few seconds of pumping the pressures read 10^-1mBar at the chamber upstream and downstream positions.</p> <p>Speaking to David I learned Ecodry 1 may be switched on ready as long as the<strong> gate valve "T1600 Backing" is closed</strong></p> <p>Learning point: Ensure the <strong>automatic gate valve "T1600 Backing" is closed before</strong> pumping. This way we can control the roughing speed using the manual gate valve on Ecodry 2.</p> <p>I wanted to inspect if anything was damaged in the chamber by this fast pump speed. The pumps were stopped and the chamber vented.</p> <p>Upon visual inspection the S2 and 0.9um mylar in front of the diode were undamaged.</p> <p>Target CH2 I on the ladder was loose at one side, the target ladder was removed and CH2 I at position 3 was replaced with CH2 VII.</p> <p>Now the target ladder is in the following configuration: See attached IMG_2738.jpg</p> <table border="1" cellpadding="1" cellspacing="1" style="width:500px"> <tbody> <tr> <td>Position</td> <td>Target</td> </tr> <tr> <td>1</td> <td>Blank 3mm</td> </tr> <tr> <td>2</td> <td>Blank 10mm</td> </tr> <tr> <td>3</td> <td>CH2 VII</td> </tr> <tr> <td>4</td> <td>CH2 II</td> </tr> <tr> <td>5</td> <td>CH2 III</td> </tr> <tr> <td>6</td> <td>CH2 V</td> </tr> <tr> <td>7</td> <td>natC I</td> </tr> </tbody> </table> <p>At 16:45 the roughing pumps were switched on, this time with the "T1600 Backing" gate valve closed. The manual valve was cracked open.</p> <p>By 17:01 the pressures read Up = 4.2e-1 mBar, Down = 4.1e-1 mBar.</p> <p>At 17:08 the turbos were switched on.</p> <p>At 18:07 the pressures read Up = 1.2e-5mBar, Down = 3.2e-5mBar.</p> <p>We are ready to connect the preamp box for the S2, and also connect the preamp for the pin diode.</p> Encoding: HTML ELCode plain Suppress Email notification

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