Today we started vacuum chamber assembly work

• 10:16 am: Particle count measurement of clean room
• 10:34 am: Particle counting finished: meets ISO 5 standard
  1. Zone 3 :
     • 0.3 u: 3159
     • 0.5 u: 789
     • 1.0 u: 83
  2. Zone 4 :
     • 0.3 u: 498
     • 0.5 u: 41
     • 1.0 u: 0
• 10:45 am: Assemble vacuum feedthrough
• 11:08 am: Finish assembling feedthrough
• 11:14 am: Assemble inverted magnetron pirani gauge
• 11:29 am: Finish assembling magnetron gauge
• 11:31 am: Assemble calibrated Ar Leak
• 11:47 am: Finish assembling Ar leak
• 11:49 am: Assemble up to up-to-air valve
• 11:59 am: Finish assembling up-to-air valve
• 12:00 pm: Break for Lunch
• 1:00 pm: Came back from lunch
• 1:20 pm: Assemble 45 degree elbow [RGA Line]
• 1:35 pm: Finish assembling 45 degree elbow
• 1:35 pm: Assemble Reducing nipple [Pump Line]
• 1:49 pm: Finish assembling Reducing nipple

• 1:53 pm: Attempt to install gate valve [Pump line] but bolts could not fit to the gap between 2.5" reducing nipple (0.95" length, shortest 5/16 bolt is 1.5" in total length).
  Thickness of of CF flange on reducing nipple is 0.75" inch. Ideally, we want to have 0.2" engagement to the gate valve, thus0.95" + 0.25" head thickness = 1.2" > 0.95" gap.
  We thus most likely will need a replacement for the reducing nipple. We decided we would hold up on installing the rest of the pump line until we have got components to fix this problem

• 2:05 pm: Assemble gate valve [RGA line]
• 2:15 pm: Finish assembling gate valve [RGA line]
• 2:18 pm: Assemble 4-way cross [RGA line]
• 2:30 pm: Finish assembling 4- way cross [RGA line]
• 2:37 pm: Assemble manual bellow sealed angle valve [RGA line]
• 2:43 pm: Finish assembling sealed angle valve [RGA line]
• 2:45 pm: Assemble inverted magnetron pirani gauge [RGA line]
• 2:55 pm: Finish assembling magnetron pirani gauge [RGA line]
• 2:56 pm: Assemble vacuum hose, thin wall [RGA line]
• 3:04 pm: Finish assembling vacuum hose, thin wall [RGA line]
• 3:45 pm: Packing up for the the day
• 4:00 pm: End-of-date particle count measurement
  1. Zone 3
     • 0.3 u: 1080
     • 0.5 u: 124
     • 1.0 u: 83
  2. Zone 4
     • 0.3 u: 540
     • 0.5 u: 83
     • 1.0 u: 83

[Luke, Luis, Cinthia, Michal, Tyler]

On the 26th Cinthia, Michal, and I took off the insolation on the vacuum chamber and re-routed it to include the new RGA volume. 

The next day Luis and I finished up the last of the flanges to be attached. We attached the Pirani gauge with a conical reducing nipple to the 2.75" port on the vacuum chamber. We then preformed the Helium leak testing, both flanges were quite low the 2.75" flange had a leak of 1.68e-10 torr and the 1.33" flange of 5.5e-12 torr. The leak on the 1.33" flange was so low it was difficult to know how much of it was real and how much was just noise.

TL;DR:

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)
• 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:
  1. Controllers for bottom + pump & RGA line heaters remain the same: connected to power strip on vacuum end of the table
  2. 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

The electrical overload problem encountered in ELOG 130 has been resolved. The two heater controllers, which draw up to 14.1 A each, overloaded the UPS and tripped one of its circuit breakers, shutting off power to both power strips mounted above the optical table.

I reset the circuit breaker and rerouted the two heater power cables instead to two separate 20 A outlets in the overhead cable tray outside the cleanroom (both on the LP3B 6 circuit). The two high-limit temperature controllers are now permanently positioned, as shown in the photos. For now, the PID controllers have been left sitting at the table level. I am ordering extension cords that will enable us to move those up to the overhead shelf, as well. I ran the heaters in their new configuration for several minutes without issue. Thus we should be able to now proceed with baking the chamber.

For future clarity, I added labels to power strips around the lab indicating which ones are powered by the UPS. To avoid overloading the UPS, only sensitive electronics or devices that could be damaged by a sudden loss of power should be connected to these.

[Aiden, Cao]

1. Helium leak test

• 2:00 pm: Uninstall regulator from nitrogen gas tank and move to helium gas tank. Place helium onto cart and move to the rear door of the clean tent. With the tank remaining outside, feed hose through the flexible wall to use in clean tent - See attached image
• 2:25 pm: Start Helium leak test: At each CF connection, He gas is sprayed while its level is monitored with the RGA in leak detection mode. A constant flow of helium is maintained until the level of helium detected by the RGA plateaus out.
  • All connections show low helium leak detected (< 3e-11 Amp)
  • The connections with highest leak detected are from reducing cross to flex hose and cross to RGA. They are on 2 - 3e-11 Amps. All other connections are less than 8e-12 Amps. We verified tightness of these two connection but they cannot be tighten any further

2. Argon calibrated leak test

• We opened the Ar calibrated leak. Upon opening the valve to allow Ar to flow through, we can see a surge in pressure measured by the gauges from 6.7e-7 mbar to 1.2e-6 mbar. This is then drop down and stabilised around 8.9e-7 after 5 minutes.
• Upon the the equilibrium is reached, we ran RGA scan twice in Analog mode with the following settings:
  • Points Per AMU: 10
  • Start Mass : 1
  • End Mass : 100
  • Focus Voltage: 90 V
  • Channel Electron Multiplier (CEM) : On
  • CEM Voltage: 1060 V
  • Unit: Amps (ion current)
  The settings is saved as rga100amu_scan.rga RGA application file in C:/Users/controls/Documents/Vacuum/VacuumChamber/RGA. The data file is saved in Data folder as ArLeak_230512.txt. This file contains the current values for corresponding AMUs. Using this dataset, we can obtain our chamber outgassing rate.
• Using RGA_scan_process.py , which is adapted from Mike Zucker's Matlab code E2000071, and the Ar calibrated leak posted in elog 95 we can compute the outgassing rate to be 150.5E-10 Torr l/s . Our outgassing rate is 37.5 times higher than the required (4.00E-10 Torr L/s per E080177)
• See image attached for the spectrum and the hydrocarbon (HC) tracer masses used to evaluate outgassing
• All codes and data are stored in Vacuum git repo . I'll qrite up an instruction to use the code and post it on our wiki page.

After finishing with Ar cal leak test, we close Ar valve, disconnect and turn off RGA. The He tank is moved back to the wall mount. The chamber is ready for baking installation

Continued tightening bolts on the turbo pump and 6"-8" reducer to reduce the leak. The final leak test values for the turbo pump flange was 3.0 e-9 and the other 6"-8" reducer flange was 4.0 e-9.

We will continue to let it pump down as the screws could not be tightened anymore. Looks like new gaskets will be needed to reduce the leaking on these flanges.

We will be configuring the RGA line to remove the spherical cube from the system. Currently our plan for the new design is to connect a 4.5" to 2.75" Reducing Cross to the gate valve on the vacuum system. It will be orientated vertically with the turbo pump on top coming off the end will be a 90 deg elbow. On the bottom there will be a 4.5" to 2.75" Zero length reducer attached to that will be a Tee on one side the pressure sensor and the other the RGA. Connected to the elbow will be the calibrated leak. 

The only parts not readily available are the ZLR and the 2.75" gaskets

Summary : We resolved problems with heaters tripping power and were able to proceed with chamber baking

1. Circuit connection adjustment

After yesterday elog 137, today we resolved most of these issues. After Jon contacted Facilities, the LP3B 6 circuit was reset and the cleanroom filter & light panels resumed to work as normal.

Regarding the connection of the heaters. we made the following adjustments:

• High-temperature controller powering lid + upper volume heater: connect to LP3B 8 circuit (clean room sides, 2 outlets)
• High-temperature controller powering bottom + lower volume heater : connect to LP3B 4 circuit (workstation side, 2 outlets)

2. Replacement of vacuum nipple insulation

We had also received new insulation pieces from Worbo today to replace the existing insulation with the new ones (see images). These cover the 2 4" tubes (for 6" flanges ) and the 4 1.5" tubes (for 2.75" flanges). The new insulations fit perfectly on these tubes. I also placed all insulation taken off from the last elog back onto the chamber ( these are insulations for the pumps and RGA lines).

3. Baking

• Starting set point: 40 deg C
• Step increase: 10 deg C up to 80 deg C, 5 deg C from 80 deg to 120 deg C
• At each step, the temperature readouts show approx. 2.1 deg C overshooting, wait to settle back to approx 1.5 deg C overshoot before increase the set point again

The temperature of the chamber reached as stable 120 deg C without any power issues at 3:45 pm. I waited another 15 minutes to verify its stability and the official baking duration started at 4:00 pm Jun 29 2023. Since we are baking at 120 deg C instead of the standard 150 deg C for Aluminium, the duration for the bake will be over three days until Monday morning, upon which we will slowly ramp down the the temperature.

By 5:30 pm Friday, the pressure had reached 8.6e-8 torr and was continuing to fall. So it seems we are OK to proceed with permanentizing this configuration (cable routing, heater tape reinstallation).

1. Turn off the RGA filament and disconnect it.

2. Record the pressure and then close the angle valve and gate valve on the RGA line to isolate it from the system.

3. Turn off the backing and turbo pump and let the turbo pump spin to a stop by slowly leaking the chamber. The slower the safer.

4.Slowly open the vents on the chamber and the turbo pump. Making sure not to raise the pressure too fast.

5. Once done venting the chamber, open the lid by removing the bolts and prying the lid open with a long flat head screw driver.

6. Removed previous parts and placed them into clean bags. Place new parts inside of the chamber and group them together close to the center.

7. Place the lid back onto the chamber and tighten the bolts in a circular pattern until tightened all the way with the wrench.

8. Make sure all vents are closed and turn the backing pump back on.

9. The turbo pump can be turned back on when the pressure reaches e-1 torr.

10. Wait until the chamber reaches a pressure of e-6 torr before opening the angle and gate valve on the RGA line. After the RGA line is open and the pressure is still below e-6 torr, the RGA filament can be turned on and a leak test of the lid should be performed.

11. After the leak test shows no leaks, proceed with starting the low temp bake.

Cao and Aiden put the RGA back on to the chamber and measured the outgassing rate after the chamber has cooled down from its first bake. The figure attached shows the RGA measurements with the Argon leak open.

Also put the Full Range Gauge #2 [RGA line] back onto the system to measure the pressure and got a reading of 2.78 E-7 Torr. We believe it is actually lower as the chamber temp is still at 28 degC rather than the 24 it was previously measured at. The gauge also may have needed more time to equilibrate.

Pressure Measured Before Removing Gauge 2.31 E-7 Torr.

Went in and turned on the heating tape in increments of 30 degC until 120 degC was reached. I will let it equilibrate over night and then asses whether or not the chamber can be raised to 150 degC without having the flange to the turbo pump reach over 120 degC as it is not recommended for that flange to be any hotter.

If it can safely be raised to 150 degC, then only 2 days of baking is necessary. If 120 degC is the bake temperature, a week will be needed.

Took another set of RGA data after the second bake has cooled down to 27 degC.

Just by visual comparison to the other graphs, the HC levels of the chamber has gone down further. I will soon overlay the data for an easier comparison.

I also reinstalled the full range gauge above the RGA line. It is still adjusting itself downwards so I will have to check again to get an accurate measurement of the pressure.

Took some more data to look at the HC count. Initial data was from leaving the Argon leak closed and then left it open for 15 minutes and then took data for the open scenario. Attached are the graphs for these where attachment 1 is the closed scenario and attachment 2 is the open scenario.

From these graphs it looks like the signal-noise ratio of our calibration line is poor with the ratio between these two being 1.3. This means that the calibrated leak is barely being detected over the background. This should improve with more baking and pumping. I have also now attached overlayed graphs comparing the chamber when the leak is closed versus when it is open. As well as one comparing the chamber right after the bake versus the most recent data both with the leak open.

Dr. Richardson and I took off the insulation on the lid again to add more insulation in-between the heater tape folds in addition to what was added on top of the tape after discovering discoloration. Also cleaned the lid with IPA wipes.

Also took more RGA data, one with the leak closed and one with the leak open. The graphs below this show that the SNR is improving with the ratio now looking to be around 3. The chamber is still too dirty to be commissioned and we will need to be baked again soon.

Plugged the temperature sensor back in after getting another extension cord. Removed the electronics box for the RGA as well as the full range gauge above the RGA line.

Came in to take RGA data and found the turbo pump drawing .38 Amps. This was much higher than what it was on Friday. I investigated and found that the breaker had flipped controlling the power strip that the scroll pump was on. The scroll pump was thus not running. I flipped the breaker back and turned the scroll pump back on. I do not know if this will be a reoccurring problem as this has happened before, or if this was due to the storm. Either way the scroll pump is running and the turbo pump is now only drawing .18 Amps at 31 C.

Below are the graphs for the RGA scan that I took before starting bake 4. I have not overlaid them yet so the first one is for Argon leak closed and the second is the Argon leak open. It seems that the chamber had gotten dirtier since the leak and there is still a lot of water left in the chamber. I assume the water will go away after the low temp bake but the HC count may not go down without a longer baker. I also measured the pressure before starting the bake and it was 4.16 e-7 and 3.31 e-7 torr for t he main body volume and RGA volume respectively.

When starting the bake I noticed that the temperature sensor placed on the cross in the RGA volume was reading 40 C hotter that what the PID controller was reading for the lid. I had to remove some of the heater tape from the cross as it was way too hot compared to the lid. After removing the second strip across the cross it is still much hotter than most parts due to it being such a small part compared to the large lid. I hope that after a little bit of equilibration time that the difference between these numbers will go down. Both PID controllers were set to 120 C. The RGA cross was reading 130 C and the Turbo pump cross was reading 76 C.

Took some RGA data when we came into the room. The pressure of the chamber was 8.63e-8 Torr before turning on the RGA filament. We saw the usual spike in pressure when the filament was initially turned on. Took some data and saw that the chamber was definitely dirtier since the vacuum upgrade. See figures below.

Put the heater tape back onto the section that was removed. We may need to rearrange the heater tape again as there was not much heater tape to go around the upgraded section. We also tried to get some of the extra insulation around this section and we able to get some on around the 6-8 inch reducer.

We then took off the electronics for the gauges and the RGA, added the new extension cords to the PID controllers, and then started bake 6 which will go to 120 degC and stay that way until most likely Monday. The pressure before starting the bake was 8.28e-8 Torr.

Took some RGA data of the chamber after it has been cooling down. I do not believe that this data accurately shows the HC levels in the chamber as the pressure is still above where it was at before the bake and was still falling. I believe more time is needed to let the pressure fall and for the RGA filament to remain on to return to a point where the data can be trusted.

I measured the temperature of the flanges where some of the electronics will go and I found that the RGA flange was at 55C and the two full range gauges were at 65C. I also stopped bake 9 to cool down for measurement.