Visual inspection of lead glass modules
From GlueXWiki
Possible issues with lead glass module
- Broken lead glass, see Fig. 1 (module taken from the FCAL prototype)
- some problems can be seen by looking on the lead glass block from the side opposite to the PMT
- lead glass module has to be disassembled; the glass block has to be replaced.
- Issues with wrapping:
- small damages (holes) in the Aluminized mylar, see Fig. 2. This can be fixed by using Al sticky tape, thickness < 20 um
- Aluminum layer in the wrapping foil peels off or adheres to the glass block (penetrates into the block):
- Fig. 3 and Fig. 4: Aluminum layer peeled off resulting in some transparent holes in wrapping.
- recommend to disassemble and re-wrap the lead glass block
- Issues with Silicon cookies
- Inspect optical coupling of the glass block and the PMT by looking inside the crystal from the side opposite to the PMT
- Possible damages of PMTs during deinstallation (see Fig. 5)
- Glass blocks with discoloration signs (due to radiation)
- some glass blocks may have a brown tint (see Fig. 6 and Fig. 7). Can be checked without removing steel flange.
- recommend to replace this module
- Estimated time to refurbish FCAL module - 40 min