20130225 Shift

• After tuning and startup our shift will begin. Ends Tuesday 9am.

• Assume 8 hours

1.5hrs

• load optics (new ones?)
• background minimisation
• vary corrector for background and log during - try several correctors (4)
• vary qm14ff position for background and log during

0.5hrs

• dispersion measurement
• multi-otr measurement if working - coupling correction...

1hr

• lw otr measurement of beam size at lwip
• lw otr 10 samples for different binnings plus background
• align for collisions

5hrs

• optimise
• correlations x3
• look at optimal number of points for a scan / different nonlinear scan options
• long range quad scan

0.5hrs

• repeat quad scan with otr

21:00 Shift start

• PLIC shows similar loss in extraction line as last week. Background level
• Expected as QF21X still at 84A

• Set file set13feb25_2112.dat
• Load our optics from set file set13feb22_0718.dat
• Background around 8000 but charge around 0.9 this week so overall better.
• Had to flatten orbit a bit, but wasn't too hard.

• Measuring dispersion - null values - also our scripts won't log
• magnet mover system had died - several of the ccnets - restart now

OTR Measurements

• OTR focus scan
• OTR logs of various binnings
• OTR Quad scan

Laser-wire Collisions

• Seed laser refused to lock - tuned, locking now
• Aligning for collisions 11:45
• Chamber Horizontal aligned at 461

• Tuned orbit a bit and checked by varying QM14FF its bba - good!
• Alignment again
• H: 420, V:320

Many, many attempts at alignment. Timing was very good, horizontal also and vertical good too. The manipulator cut off the laser within 20um as seen by the APD signal. We tried adding more cable to phase line and retiming at different RF bucket and phase, but still nothing. Just as all was lost, we set it on an uber long vertical scan. When we reached the control room, signal! It was found around V:550. This in conjunction with the fact that we found the best horizontal position around 300um from where we aligned last week suggests the screen is quite misaligned with the laser focus. In this case, the laser is intercepted several hundred microns before the top of the notch were the electron beam is cut off and also the horizontal alignment to the electron beam is off.

Collisions found 03:00

Vertical Alignment	Horizontal Alignment
Vertical Collisions	Horizontal Collisions

So, vertically, the beam was found at 370, but collisions were actually found at 550. This probably because the screen notch is misaligned to the laser focus. Horizontally, the beam was found at 420, but the peak of collisions were at 200. If the screen is misaligned in both axes (along the laser axis and the electron beam axis), this would correspond to intercepting the edge of the notch at the wrong place. With this information though, collisions should be found more readily even with this alignment.

Laser-wire Scans

• Nonlinear vertical number 1:
  

• Nonlinear vertical number 2 - just as good!:
  

• Let's find the centre:
  

• Horizontal Scan:
  

• 60 point nonlinear vertical:
  

• LW Quad Scan :
• Vertical - 5 samples, 20um range, 10 steps;
• Horizontal - 20 samples, 3mm range, 30 steps;
• NL Vertical - 20 samples, 50 steps;

QM14FF Current	Quick Vertical	Horizontal	Nonlinear Vertical
81
84
86
89
92
95
98

07:00 - 'Interesting' Beam

DR Charge dropped off rapidly. Tried to tune linac phases, but with no success. Arakai-san helped. Charge was stored for about 100ms in the DR then decayed. Extraction orbit was stable in the horizontal, but crazy in the vertical. Evenutally seemed to settle, but we were very close to breaking the radiation interlock. 98.7% in the end. Reduced charge to around 0.2 x 10^10 to avoid breaking interlock. Miraculously still had collsions.

• Scan now demonstrates signal to background of 2:1!! much better than before, in fact the inverse. Two scans at the same place seem to indicate we have a 100nm beam... Whilst wishful, this is doubtful and it is likely a fitting problem due to the specific data. The horizontal size may have changed also - the beam conditions are quite different. However, it seems to make sense to stick to lower charge and to adjust the signal attenuation to scale to the ADC.

• 08:00 Signal attenuation now 0dB!! Was 9dB before.

Very small! Better repeat to investigate and verify.

• 3rd after recovery:
  

• 3rd after recover fitting with just m2 = 1 (errorbars wrong from old software):
  

• 20130226_0808_lws_xy_fit_plot.pdf: Horizontal to try and find out why too small

• 4th after recover - fewer points:
  

• 5th after recovery - even fewer points: