Aggregator
COMMENT ON Gun2 photocathode Heat and Activation - August 2026
Performed QE scans with unmasked activation:
Beam QE Scan: https://logbooks.jlab.org/entry/4544449
Low-voltage scan: https://logbooks.jlab.org/entry/4544366
COMMENT ON Gun HV Cable Operations: removal, inspection, re-greasing, and re-seating
COMPLETED Gun HV cable inspection, re-greasing & re-seating
ATLis Comments Daily Digest
COMMENT ON MPS system maintenance and repairs during physics run
FE Onset measurements for 2L22
Cavity 1: Starting GLOS = 2.16, starting GDCL = 7.0. Quench limited to 14.7 MV/m.
Cavity 2: Starting GLOS = 1.22, starting GDCL = 9.9. Reached admin limit before any quenching.
Cavity 3: Starting GLOS = 2.45, starting GDCL = 9.9. Quench limited to 18.0 MV/m.
Cavity 4: Starting GLOS = 0.82, starting GDCL = 9.9. Quench limited to 21.4 MV/m.
Cavity 5: Starting GLOS = 1.18, starting GDCL = 9.9. Quench limited to 19.8 MV/m.
Cavity 6: Starting GLOS = 3.21, starting GDCL = 9.9. Reached admin limit before any quenching.
Cavity 7: Starting GLOS = 2.23, starting GDCL = 9.9.
COMMENT ON Post SAM FE onset measurements C75 and C100 cryomodules
Operator SIGN IN
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.










