TL;DR:
We are not yet able to bake the chamber at 150 deg C due to some current limit, most likely caused power supply switching off. Also, smoke was observed at some insulation points, mainly in the small arm sections, This is likely because the insulation does not fit well and the velcro came into direct contact with heat tape. Some Velcro (made from Nylon/ Polyester) has lower melting temperature point (in 90-120 deg C range)
Full version:
20 June 23:
- Turn off heater (short term testing) Close valves to RGA line and main volume. Pressure (Torr) readout:
- Gauge 1 (main volume): 3.43E-6
- Gauge 2 (RGA line): 2.61E-6
- Gauge 2 (pump line): 3.8E-4
- Turn off turbo pump, let vacuum line vent
- Connect high temperature control unit to main power, power up, set setpoints:
- Temperature setpoint: 150 deg C
- High temperature setpoint (to switch off) : 175 deg C
- Hysteresis: 10 dec C
- change setpoint of PID control unit to 150 dec C, with high alarm set at 165 deg C
- Connect power output of high temperature control units to PID temperature control units, ensuring both are off
- Turn off scroll pump
- Replace Pirani gauge in front of turbo pump with blanks (see image)
- Pump the vacuum line back down
- Open up valves and wait until pressure of full system drop back down to 1E-6
- Install the high temperature controller thermocouples onto the chamber (see images):
- One thermocouple is installed on the other side of the cross before the turbo pump
- One thermocouple is installed on the main volume next to the PID controller RTD
- Attempt to remove electronic box and magnetic shield of full range gauges:
- Electronic box is easily removed with an Allen key
- Magnetic shield cannot be removed since the gap between the vacuum flange and the gauge bolt is too short for a spanner to go in. This is mainly due to the bolt washers are in the way (see images)
- To remove the magnetic shield, the main volume has to be vented and the gauges need to be readjusted.
- Attempt to power heaters (but only heat to 80 deg C):
- Leaving the gauges intact, the high temperature controller + PID controller are turned on to test heating the chamber
- At this point, both of the high temperature controllers are connected to the same power strip (Vacuum chamber end of the table)
- After heating up to 65-70 deg C range, the powers turned off on both controllers + the lights on one end of the table
- Upon inspection, the power strip has turned itself off, I don't know what the model of the power strip but we should check its current limit
- For a quick test, I connect one of the two heater controlling system to the power board on the work desk while leaving the other running off the same power strip: The heaters appeared to be function ok and able to reach 80 deg C, at which point I turned it off and left for the day
21 June 23:
The goals of today was to remove the electronic boxes and magnetic shields on full range gauges to enable high temperature bakeout
- Upon returning to the lab, the gauges readout of vacuum pressures were:
- Gauge 1 (main volume): 3.31E-7
- Gauge 2 (RGA line): 3.40E-7
- Venting the both main volume and RGA line
- Remove the two full range gauges from their flanges
- Electronic boxes and magnetic shields were removed according to the gauge manuals (see images)
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- Mount the gauges (with only its probing volume) back onto their respective flanges, ensuring that the flange washers do not block access to the magnetic shield screws
- Only remount magnetic shield + electronic box for one gauge (gauge 2: RGA line) for monitoring chamber pressure
- Turn on scroll pump and let the chamber pump down
- Rearrange heater controller connections while waiting for pumping down:
- Controllers for bottom + pump & RGA line heaters remain the same: connected to power strip on vacuum end of the table
- Controllers for lid + upper chamber main volume: connected to power strip on clean&bake end of the table
- Once the pressure readout by gauge 2 reached 3 Torr, the turbo pump was turned on and left to run for 45 minutes
- Upon returning to the lab, pressure on gauge 2 read 5E-6 Torr and was still decreasing
- Disconnect the ethernet cable to gauge 2, remove its electronic box and magnetic shield
- Turn on heater controller units and let them drive the heaters to get up 150 deg C
- At 95 degree range, I could see smoke at some locations, mainly the RGA and pump lines where the insulation do not fit properly and the velcros are likely to be overheated
- Upon reaching 90 degree range (measured by sensors), the powers turned off on both sides of table (including heaters, lights and scroll pump)
- Turn off both heaters controllers and unplug them from power strip. Attempt to switch the power strip back on but nothing happened
- It is now not the power strips problem and must be further down the line from outside the tent, most likely the power supply that these strips connected to: What is the power supply model + current limit?
- The heater controllers left unplugged, I temporarily plugged scroll pump to the desk power strip so it can still run
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