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Shift 20120517


Shift plan

  • Take OTR of beam size at LWIP under currently running optics.
  • Take access to diffuse the light in front of the photodiode behind last turning mirror before lens to stop it saturating at high energy (LN).
  • Load up optics and possibly standardise magnets (AA, LC).
  • Beam on, tune for background < 7000 counts with 10dB attenuation
  • OTR scans for beam size. Large range quad scan.
  • Laser wire timing.
  • Collision search.
  • Quad scans, telescope scans, laser energy/signal scans, skew scans, large beam size scans.
  • If it looks possible, switch back to previous optics at end of shift and see if we can get a lw signal.


Previous shift set file 12may1801412.dat Shift starts. OTR image σy = 12um, σx = 80um (90 degree polariser), σy = 21um, σx = 96 um (0 degree polariser).


Access to check mover systems as manipulator and OTR stage reporting hitting hardware limits. Manipulator encoder cable unplugged and OTR limit switch loosely connected to computer. Everything working after being reconnected. Low energy laser beam focus position referenced to OTR screen - between 9410 and 9390. Diffusing tissue placed over photodiode to bring it out of saturation at high laser energy.


Beam on. OTR images found. Previous set file set12apr25_1801.dat from last data taking loaded. OTR polariser scan. Without polariser or quad optimisation σy = 2.77 +/- 0.17.

Polariser scan min at 14.8 degrees, σy = 2.44um.

Image rotation scan at -87.756b (2nd file in this quad scan): min σy = 1.79um at 4.35 degrees.

QM14FF quad scan min at -88.26A, σy = 1.43um (scan range -101.75A to -71.75A).


Detector on 1250V, background ~ 14000 with 10dB attenuation. LN tuning, major difference in background with QM12FF, background down to 6000.

0 06:45

Ti6ming scan - peak found ~ 4V, set file 12may18_0734.dat. Alignment scans with ws detector. CH set to 500, CV set to 860. No collisions - check timing. Laser interlock tripped, timing check again. No collisions, recheck spatial alignment. CV 920, CH 240. No collisions.


Collisions at phase = 4V, CV: 860, CH: 240. Small signal (7000 counts on 5500)- steering to try and increase signal. Reduce attenuation from 10 to 5dB to use dynamic range of detector.

First nonlinear vertical scan gives centre CV: 854.4, rms = 14.99um (cf 35um from data taken last month).-800


Horizontal scan: n = 3, 100 steps

854 -800 - 1300
854 -1100 - 1400


Extraction line dispersion measurement at 11:56. Save set file before correcting - set12may18_1156.dat. Dispersion correction routine implemented (change QF1X, QF6X). New set file - set12may18_1200.dat

Vertical scans:

NL scan centre 853 290

LW signal lost after dispersion correction. Checked timing, regained signal changing timing by 1 bucket, lw detector saturated. Attenuation increased to 7dB, dispersion measured again (12:21), timing changed back. Phase scan to find timing peak at 3.6V.

New vertical scan:

NL scan centre 853 290

rms = 12.4um (using the rms fit as a proxy until integral fit reliable)


QK4X scan: 2.610A

  • QK4X 2.610 lwScan> 20120518_1221_lws rms = 12.4um
  • QK4X 5.610 lwScan> 20120518_1240_lws rms = 12.6um
  • QK4X 8.610 lwScan> 20120518_1251_lws rms = 14.9um
  • QK4X -0.390 lwScan> 20120518_1303_lws rms = 14.1um
  • QK4X -3.390 lwScan> 20120518_1315_lws rms = 14.7um

Attenuation changed to 9dB as charge increased and detector saturated.

  • QK4X -6.390 lwScan> 20120518_1337_lws rms = 20.6um
  • QK4X 11.610 lwScan> 20120518_1353_lws rms = 12.13um

LN integral analysis of 1221_lws data (data now i) charge normalised, ii) background subtracted, iii) laser energy normalised) σy = 1.24 +/- 0.34um. With couple of outlying points removed σy = 1.38um (cf 1.42um from OTR measurements).

QK4X set to 3.090A, min. of parabola fitted to rms data excluding 11.610 data.


Phase scan to check timing. Still centred at 3.6V.

Quad scan:

  • QM14FF -88.26 lwScan> 20120518_1430_lws rms = 13.02um
  • QM14FF -90.26 lwScan> 20120518_1442_lws rms = 18.87um
  • QM14FF -92.26 lwScan> 20120518_1455_lws rms = 17.78um
  • QM14FF -94.26 lwScan> 20120518_1517_lws no collisions

Last scan no collisions, checked timing, changed by one bucket, found collisions again. Phase scan to check timing. Centre 3.49V

  • QM14FF -94.26 lwScan> 20120518_1539_lws no collisions - not sure why?
  • QM14FF -86.26 lwScan> 20120518_1544_lws rms = 20.2um
  • QM14FF -84.26 lwScan> 20120518_1557_lws rms = 14.6um
  • QM14FF -82.26 lwScan> 20120518_1611_lws rms = 13.7um
  • QM14FF -80.26 lwScan> 20120518_1625_lws rms = 14.2um
  • QM14FF -78.26 lwScan> 20120518_1639_lws rms = 11.97um
  • QM14FF -92.26 lwScan> 20120518_1654_lws rms = 14.9um (again to recentre nonlinear scan)
  • QM14FF -94.26 lwScan> 20120518_1_lws earthquake scan


Large earthquake, beam off. set file 12may18_1723.dat

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Topic revision: r6 - 23 May 2012 - LauraCorner

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