On Monday Oct 5th a decision was made to uncover and remove the T2 Protect Monitor due to faulty readings. The monitor had been behaving strangely since the September shutdown, and had been getting worse over time.
- Blocks were removed over T2 starting Monday afternoon. It is necessary to remove the narrow 12' block and two 6' blocks west of the T2 plug block in order to fit the flask frame in for protect monitor removal
- The monitor was moved to the hot cell by 7pm on Monday. Pierre was operating the crane and there were no issues with the move. (monitor measured 15mSv/hr at 0.5m)
Oct 6:
- Monitor inspected: a thin piece of foil was found jammed into the entrance side of the monitor (see photos) & a heat or burn mark was seen on the exit side above and to the south of the plate gap. It is suspected that this material traveled down the beamline at high speed when there was a vacuum burst during the September shutdown. In light of this information it was decided to remove the T2 target and T1 target as well (see following e-logs)
- Monitor elevation measured: 1835.8mm (april 2015 measurement was 1836.1 --> ok)
- Old monitor cassette removed, new one installed. Elevation checked: 1832.2mm - did not match, removed, decontaminated, and returned to Probes for adjustment
- Adjusted monitor installed, elevation checked: 1835.8mm --> ok
- Electrical check done by Probes group at hot cell: found left plate shorted to ground
- Cassette removed, decontaminated, and repaired by Probes Group
- Cassette reinstalled, and electrical check repeated --> ok
Oct 7:
- Monitor elevation re-checked: 1836.2mm --> ok
- T2 protect returned to beamline, bolts installed, cables connected
Oct 8:
- Vacuum pumped on T2 volume after T2-MK2 target returned (see next e-log): Only reached 2 Torr and a leak was heard coming from T2 protect flange.
- T2 protect was unbolted and lifted ~1in for cleaning of the flange base and o-ring
- The T2 volume then pumped down normally
- A helium leak check of all flanges on the T2 monolith was done by Vacuum Group --> no leaks found |