Aggregator
LERF Operator Shift Log, 2026-08-24 DAY
Start of shift: Controlled access at LERF.
Autolog restore
BSList #121089: R30-4 gun optics at 140 kV
Running laser-stage grid-scan code: 11000...14000 in x, 16500...19500 in y, 16x16 grid.
The active area is larger than this, but past this rectangle, the gun field deflects the beam too strongly for the second BPM to work.
Figure 1: positions and angles.
Figure 2: extrapolated rays and focal length vs laser-spot position. The stage coordinate is in mm based on the calibration done earlier, though whether this agrees 100% with the size of the exposed photocathode surface in stage units is unclear.
APPROVED Cooling tower mechanical pm's
APPROVED Cooling tower pump mechanical pm's
JAM: LERF RF Authorization Updated
ABIL tag #9993 on LCLS2 CM tuner 2 limit switch has been removed
COMMENT ON Post SAM FE onset measurements C75 and C100 cryomodules
Moved DecaRads from 2L05, 2L23 & 2L24 to 2L22, 2L25 & 2L26.
Control and readbacks are via normal paths for C100 DecaRads, 2M, 2P & 2Q.
All 10 chs. on all 3 systems read normal background counts after installation and are ready for FE testing.
Note that the readbacks for the bias on 2L23 & 2L24 (2N & 2O) are not valid, since the hardware has since been moved out of those 2 zones.
The system on 2L03 (via SRF DecaRad screen sl05a, DRADS05ASRF...) remains in place, just in case 2L03 becomes functional, except for ch.3 (WG 3&4) which was poached to get 2L22 ch.4 working.
"Starting FE Onset measurement in 2L22"
"Injector back to beam; South Linac to Power Permit"
BSList #121089: x/y stage response
Using the spiricon camera, I recorded the laser-spot position as a function of x/y coordinate for calibration of the gun optics data.
x,y,spot_x,spot_y
13400,18900,4.790,3.381
12900,18900,3.998,3.396
12400,18900,3.209,3.376
12400,18400,3.177,2.578
12400,17900,3.190,1.795
The last two columns are the centroid position in mm as reported by BeamGage.
Assuming the distance to the camera is correct, the calibration is 1.6 mm per 1000 units in both axes.
After the measurement, I put the laser beam stopper back to where I had found it, protecting the camera.
LERF Vault now ODH0
Laser maintenance mode enabled
Operator SIGN IN
Gun HV Turned Off
"LERF in restricted"
Gun HV Rampdown Initiated
BSList #120356: Restore and Beam QE scan after full-area activation
Restored allsave #27614 (setup from before MOLLER beam study).
x/y stage position as found: 13400 / 18900
Orbit as found with C laser: Figure 1
Unable to steer out the difference with the x/y stage only, so either reactivation or reinsertion must have changed the centroid trajectory. But this is more than good enough as a reference for a QE scan.
Trying 10500...14500 in x, 16000...20000 in y.










