ligo-ex ligo-ds
  Richardson Lab Experimental Log, Page 1 of 10  Not logged in ELOG logo
 List |  Find |  Login |  Help 
 Full | Summary | Threaded | Collapse | Expand  Show only new entries    468 Entries 
Goto page 1, 2, 3 ... 8, 9, 10   Next  
Entry  Tue Apr 4 09:53:37 2023, Peter, Update, VLC Update, Laser intensity/polarization drift measurements initial_Intens_measure_set_up.jpg
The set up for the next round of beam characterization measurements has begun. The beam is initially passing through a half waveplate, is split at a polarizing beam splitter, and then stirring mirrors are used to properly aim the beam into photodiodes (not yet installed). This is the current configuration of the set up.
Entry  Thu Apr 6 10:20:43 2023, Peter, Update, VLC Update, Laser intensity/polarization drift measurements Optical_Setup_4-6-23.jpg
More optical components were added to the optical set up for laser intensity / polarization drift measurements. Both lenses and both PDs were added to the configuration, as seen in the image below. The beam is already well aligned into the center of both of PDs, and focused nicely by the lens. Both PD's take BNC connecting cables, and the Red Pitaya takes SMA connecting cables. Since we are currently without a BNC to SMA cable, and we do not want to cut, strip, and crimp what we have, then measurement process cannot proceed until we get the cables.
Entry  Fri Apr 28 11:21:01 2023, Peter, Update, VLC Update, Laser intensity/polarization drift measurements IMG-0183.jpg
The Digi-key cables have arrived, and I have began implementing them in the intensity drift measurements. There was a slight problem initially in connecting the SMA to BNC cables from the photodiode to the red pitaya, since the red pitaya was way on the other side of the lab. Cao and I connected the red pitaya to a new ethernet cable that extended far enough for the red pitaya to sit comfortably on the breadboard with the optics. Right now the PDAs are not connected to the red pitaya. I have connected them to the oscilloscope in order to read out how much voltage they produce upon incidence of 532nm laser light. This was done in order to make sure that they do not surpass the limit of the red pitaya (+-1V). I have not acquired a value for the readout voltage of the PDAs since I had to go to class. I will gather this preliminary data soon.
Entry  Thu May 18 14:07:08 2023, Peter, Update, VLC Update, 532nm Intensity Measurement Time_Series_Trial_4.pngTime_Series_Trial_5_2hrs.png
I figured out a method in which to capture power measurements including the initial seconds in which the beam is first turned on. I first clear and restart the kernel of the python notebook. Then I run the command to connect the red pitaya oscilloscope package to the input data being taken in both channels. To my understanding, this allows for data acquisition as the code compiles. I then started looping the 1.074s trigger bunches, and then roughly 2 seconds after I ran that command, I went and turned on the laser. The first plot shown is a 2 minute practice trial of me trying this technique to make sure that the python package was correctly registering the input of the red pitaya. It is clear that initially the laser is off, and then as I turned it on, the voltage in each channel spikes, which is compelling evidence that the code is working. I then set the data collection to be 7518 seconds (7000 loops), which is about 2 hours and 5 minutes. I repeated the same technique as for the first plot, only changing the amount of time I collected data. The second plot shown here is the voltage being read in each channel as a function of time. As we can see, over a period of hours, the intensity drifts quite dramatically for the first several minutes, and then begins to stabilize slightly. However, there are still some strong sudden fluctuations in each channel.
Entry  Tue Jun 6 16:15:09 2023, Peter, Update, VLC Update, Launch Optics for Visible Light Cavity IMG-0882.jpgIMG-0883.jpg
I assembled the first few components of the launch optics for the visible light cavity. Below is an image of the current table configuration, and the image is how the cavity will be oriented on the table.
Entry  Thu Sep 7 19:24:25 2023, Peter, Update, VLC Update, VLC Launch Chain IMG-3404(1).jpgIMG-3408(1).jpg
The launch optics up to the Faraday Isolator have been added to the breadboard. In the first image, the optics are (from L to R) the stirring mirror, half-wave plate, polarizing cube, 100mm f lens, electro-optical modulator, Faraday isolator, 50mm lens (not part of final design), stirring mirror (not part of final design)
Entry  Mon Oct 9 11:06:17 2023, Peter, Update, VLC Update, VLC Launch Chain IMG-3540.jpgIMG-3538.jpgIMG-3533.jpgIMG-3522.jpg
Implemented the new stage for the EOM. Took power data at different positions in the launch chain. Beam waist: 0.066mm (beam waist is inside EOM). Power before EOM: 0.473mW. Power after EOM: 0.452mW. Power after Faraday Isolator: 0.415mW. Might need to adjust better to configure for clipping losses. Images of setup are attached below.
Entry  Mon Oct 23 07:28:57 2023, Peter, Update, VLC Update, VLC Mode Matching Carney_VLC_Update.pdf
I have attached a pdf with slides of my latest updates.
Entry  Mon Nov 6 11:31:25 2023, Peter, Update, VLC Update, VLC Mode Matching VLC_Update_11_6_23.pdf
See Update Attached
Entry  Mon Nov 13 06:15:45 2023, Peter, Update, VLC Update, VLC Mode Matching VLC_Mode_Matching_3.pdf
Weekly Updates Attached in pdf
Entry  Fri Dec 8 11:15:21 2023, Peter, Update, VLC Update, VLC Assembly IMG_4194.jpgIMG_4195.jpgIMG_4197.jpgIMG_4196.jpg
The optics of the visible light cavity have been assembled. The mode matching telescope is folded through the two stirring mirrors at the corners shown in the image below, with the first lens (f=0.2m) before the first stirring mirror, and the second lens (f=0.5m) between the two stirring mirrors. The distance from the cavity to the edge of the table is 14cm. There is still some work to be done on the alignment of the cavity, as the beam does not seem to be completely centered on the two mirrors.
Entry  Tue Jan 16 10:01:21 2024, Peter, Update, VLC Update, VLC Faraday Isolator and Mode Matching VLC_Mode_Matching_Design_-_Remastered.pdf
Attached is a PDF of my weekly updates.
Entry  Mon Apr 15 11:51:03 2024, Peter, Update, VLC Update, VLC VLC_Update_April_15_2024.pdf
An update on the VLC project is attached below:
Entry  Mon May 13 14:53:29 2024, Peter, Update, VLC Update, VLC VLC_Update.pdf
VLC Update WEEK 7 attached below
Entry  Sat Feb 4 17:01:03 2023, Peter, Update, VLC Electronics, Laser Data OmegaX_M2_Fit_3.pngOmegaY_M2_Fit_3.png
Peter and Ryan took laser beam data. Configuration: 100mm focal length lens is ~100mm from lens. 150mm focal length lens is ~200mm from first lens. Beam waist is ~420mm from second lens. Beam waist is very small still. Had to input large amounts of error in data collection. Took width data successively at points near waist and at >= Rayleigh range. Plots are shown below. Key points: Took a while to figure out optimum configuration for lenses to be placed so that an accessible beam waist could be obtained. Beam waist is still very small. May need to do an ABCD calculation to see if there is anything bigger that can be obtained.
Entry  Tue Feb 28 19:31:05 2023, Peter, Update, VLC Electronics, 532 M2 Measurements X_width_and_Y_width.png
Took M2 measurements today. Configuration: Lens 1 (f = 50mm) at 0mm. Lens 2 (f = 150mm) at 200mm, camera at 350mm. The laser beam was being moved in -z direction on track (so further away from the first lens). Quick data shown in the sheets plot. Not a real fit. I was trying to see where the beam waist was if there even was one. Seems that it is much further than we have room for on the track. Will need to come back and take more data. I suggest maybe Dr. Richardson or Cao come and see the configuration in person and how the beam diverges for themselves on the detector card. Maybe they can offer pointers to make this go smoother.
Entry  Thu Mar 9 12:03:59 2023, Peter, Update, VLC Electronics, 532 M2 Measurements OmegaY_M2_Fit_3.pngOmegaX_M2_Fit_3.pngoptical_setup.jpg
Took more M2 Data today. Picture of the optical set up is shown below. lens1 f = 100mm, lens2 f = 50mm, lens3 f = 150mm. There was a nice converging/diverging beam profile, and the beam waist was able to be read by the camera. I took as much data as I could before clipping loss. The M2 value is quite high.
Entry  Fri Mar 10 12:08:09 2023, Peter, Update, VLC Electronics, 532 M2 Measurements OmegaX_M2_Fit_4.pngOmegaY_M2_Fit_4.png
Took more M2 laser data today. The configuration is the same as before except now the beam camera is the only component moving. Pictures can be seen below. The beam shape in x and y is very consistent with low error. However, the M2 value is still a bit high.
Entry  Tue Apr 4 09:39:58 2023, Peter, Update, VLC Electronics, 532 M2 Measurements OmegaY_M2_Fit_8.pdfOmegaX_M2_Fit_8.pdfM2_Measurements_Set_Up.svgBeam_Data_8_3lens.txt
Final M squared measurements were taken Wednesday, 3/29/23 by Peter and Ryan Hinosawa. 5 separate sets of data were taken, and upon discussion, we declared the plots shown below in attachment 1 and 2 as the final plots of our M squared measurements. The optical design of the M squared measurement process is given in attachment 3. The laser and three lenses shown below are mounted on the optical table. The track is placed behind the third lens, and the camera is moved along the track to take successive measurements of the beam's width. This will allow us to see a change in the beam's width over its propagation direction. The raw data is given in attachment 4 as a Beam_Data_8_3lens.txt file. This is eventually what gets used to generate the plots shown below. The code to run the analysis on these measurements (as well as analysis on the Gaussian intensity profile fitting) can be found: git@git.ligo.org:uc_riverside/visible-light-cavity.git
Entry  Tue Apr 4 16:43:53 2023, Jon, Update, VLC Electronics, Additional Thorlabs PDA10A2 PDA10A2.png
I ordered a second PDA10A2 and mounting post + spacer (which puts the aperture at the VLC's standard 3" beam height). These arrived today and I delivered them to the lab. They are sitting on the VLC table near the laser.
Entry  Tue Apr 25 11:56:37 2023, Jon, Update, VLC Electronics, Red Pataya has arrived Red_Pataya.jpg
The Red Pataya 125-14 starter kit that we ordered for locking the 532 nm cavity has arrived. I left it laying on the optical table near the laser.
Entry  Mon May 1 18:56:57 2023, Peter, Update, VLC Electronics, 532nm Intensity Measurement graphs.jpgTime_Series_Trial_1.png
I've configured the two PDA's to the Red Pitaya. I put a 50 ohm resistor connector to each red pitaya input port. This was because the oscilloscope showed that the voltage reading from the P polarization PDA was almost at 1V, which was the limit of the red pitaya. Once both S and P polarization PDA's were connected, I opened the red pitaya's oscilloscope. A screenshot of the voltage readings is shared below. Channel 1 (Yellow) is for S polarization. Channel 2 (Green) is for P polarization. It would seem that there is a significant amount of polarization in the P direction as opposed to the S direction. I then tried running the template time series measurement within the python notebook from channel 1 only. The python notebook graph is shown below. I have not figured out what are the units of time on the x axis, and I have not figured out how to change the amount of time that the red pitaya takes data. A plot of the time series measurement is shown below.
Entry  Tue May 2 15:55:33 2023, Peter, Update, VLC Electronics, 532nm Intensity Measurement IMG-0221.jpgIMG-0222.jpggraphs(1).jpgTime_Series_Trial_2.png
I changed the 1/2 wave plate from the lens mount to the rotational optic mount. This allowed me to rotate the 1/2 wave plate, which changed the respective polarization power transmitting through S and P polarization. Initially, more power was coupled into the P polarization. Now, with the 1/2 plate rotated, both channels are experiencing the same voltage reading. Before feeding the PDA signals into the red pitaya, a 50 ohm terminator had to be placed at the SMA connection port so that the input power into the red pitaya did not exceed 1V. With this configuration, both channels experience about 0.35mV. (See attached) I then opened the Jupyter notebook, and ran a demo time series measurement from the red pitaya. This time, I was able to get a plot featuring both channels (green is P polarization. Blue is S polarization). The plots are consistent with what is shown in the red pitaya oscilloscope. However, the time collection (I'm assuming) only runs for about 0.018s. I will have to write some of my own code to loop over this measurement, and collect more data.
Entry  Thu May 4 14:01:10 2023, Peter, Update, VLC Electronics, 532nm Intensity Measurement graphs(3).jpggraphs(2).jpg
I adjusted the rotational mount of the wave plate to see if the power can be 100% coupled into either S or P polarization. The images shown below of the oscilloscope indicate that this is not possible. The minimum transmitted power we can obtain in either S or P polarization is 75mV. The maximum voltage we obtain in either S or P polarization is ~ 740mV. This means that at a maximum, we can obtain ~ 90% polarization in either direction, indicating that our laser has a slightly elliptical polarization.
Entry  Tue May 16 11:56:33 2023, Peter, Update, VLC Electronics, 532nm Intensity Measurement Time_Series_Trial_3.png
With the configuration the exact same as before, I used the Jupyter notebook in the red pitaya's development package to collect data from both input channels. Last week, I was able to take data, yet only for a very short period of time, and I did not know how to change it. I went online to the red pitaya's user manual to figure out how to change the sampling period for longer. The link to the page is here: https://redpitaya.readthedocs.io/en/latest/appsFeatures/examples/acqRF-samp-and-dec.html#s-rate-and-dec Though I now know how to change the period of time for which data is taken, the maximum amount of time is still only about 8 seconds. So with help from Cao, we looped over the data taking samples, and got a mean value for each iteration. We then put all those mean values in an array, and plotted it. Below, we see a plot of both the S and P polarizations, and a sum of both of them. As seen in the graph, I have set the time to be able to take data for almost 2 minutes. There is some slight drift in the respective intensities. The next steps I believe are to convert the units into watts, and take data for longer periods of time.
Entry  Mon May 22 16:43:28 2023, Peter, Update, VLC Electronics, Laser intensity/polarization drift measurements S-P_Polarization_Diagram.svgPolar_angle_vs_time.pngRel_Intens_vs_time.png
In order to fully analyze the polarization data taken last Thursday, I needed to convert the signal output (which is in volts) to power (units of watts). I used the power meter to accomplish this. Keeping the exact same configuration of PD's and beam splitting, opened the red pitaya's oscilloscope package. I then took the power meter, and held it in front of the PD to measure the amount of Watts at each PD. I then wrote down the corresponding voltage being seen in the red pitaya. I took 5 sets of measurements for each PD to get experimental accuracy. I then used a simple y = mx + b fit to find out the constant m that converts the input wattage into voltage. For the s polarization, the conversion factor is 0.83. For the p polarization, the conversion factor is 1.12. I then used this data to plot polarization angle as a function of time, and the relative intensity drift as a function of time. The plots are shown below. The physical meaning of the polarization angle is shown in the unit circle diagram below, in which P is the total power.
Entry  Wed May 24 14:28:26 2023, Peter, Update, VLC Electronics, Laser intensity/polarization drift measurements Time_Series_Trial_7_16hrs.pngPower_vs_Time_16hrs.pngPolar_angle_vs_time_16hrs.pngRel_Intens_vs_time_16hrs.png
I went in and took polarization drift data for 16 hours. The run started at 6:08pm and finished at 9:15am the next day. The four plots below are the same plots shown for the 2 hour collection and previous trials, except they extend to 16 hours. The only one that is different is the Power vs. Time graph. This is a graph of the actual incoming power of the laser (as opposed to the signal voltage that the PDA's output into the red pitaya). This was done using the calibration factors of the respective PDA's and as we can see, since there is a difference in the calibration factors between detectors, there is a difference in the power that's coupled into S and P polarization.
Entry  Wed Apr 12 16:13:19 2023, Cao, Physics, VAC, Vacuum prep and installation VacAssy230412.png
Aiden, Pamella, Peter, Shane, Cao

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

    Reply  Fri Apr 21 00:06:43 2023, Jon, Update, VAC, Vacuum prep and installation - parts have arrived SS_parts.png

The two parts needed to complete the vacuum assembly (ELOG 70) have arrived.

  • (10) 5/16"-24 x 1 3/4" threaded rods - for attaching the turbo pump reducing nipple to the CF 4.5" gate valve;
  • (1) 45 degree CF 2.75" elbow for attaching the calibrated Ar/He leak to the chamber.

I left them laying on top of the ultrasonic washer. They both need to cleaned and baked following the standard procedure for stainless steel, as the threaded rods are visibly dirty.

Entry  Thu Apr 27 16:23:44 2023, Cao, Pamella and Julian, Physics, VAC, Installing vacuum system (cont.) IMG_0139.pngIMG_0136.png
    [Pamella, Cao and Julian, Shane]
  • Particles account
  • 10:37 am: Starting the particles account
    1. Zone 3:
      • 0.3u: 1662
      • 0.5u: 872
      • 1.0u: 415
    2. Zone 4:
      • 0.3u: 831
      • 0.5u: 124
      • 1.0u: 0
  • 11:14 am: Start removal of calibrated leak to install 45 deg elbow
  • 11:21 am: Elbow installed, re-install calibrated leak back on
  • 11:29 am: Finished re-install calibrated leak, start installing gate valve on pump line
  • 11:47 am: Finished installing gate valve, start installing reducing cross onto gate valve
  • 12:02 pm: Finished installing reducing cross, start installing 90 deg elbow to reducing cross
  • 12:17 pm: Finished installing reducing cross, lunch break
  • 01:24 pm: Come back to the lunch break.
  • 01:26 pm: Start installing vacuum hose to elbow.
  • 01:40 pm: Finished installing vacuum hose.
  • 01:43 pm: Start installing turbo pump.
  • 02:00 pm: finished installing turbo pump .
  • 02:10 pm: Start installing standard wall hose from turbo pump to scroll pump
  • 02:21 pm: finished installing hose onto scroll pump, start installing lid. Remove lid from chamber, insert viton O-ring. Place lid back
  • 02:30 pm: Secure lids with screw. Start installing turbo pump controller cable: Pass cable from outside (controller) up the top of clean tent and connect to 8 pin connector on turbo pump
  • 03:00 pm: Installing air cooling unit for turbo pump, found 8 M3 screws for air cooling unit in the C&B cabinet to install the fan bracket onto the back of turbo pump. Fan control cable is routed up to the top of the cleanroom to the controller
  • 03:15 pm: Installing full-range gauge cable to the controller outside cleanroom. Ethernet cables 1 and 2 are used. Cable 1 is used on the RGA line gauge. Cable 2 is connected to the main body gauge. Cable1 and 2 are connected controller's channel 1 and 2 respectively.
  • 04:00 pm: Finish installing gauges cables. Cables are routed up along the frame to the controller sitting outside the cleanroom
  • 04:15 pm: Finished. End-of-date particle count
    1. Zone 3:
      • 0.3u: 3699
      • 0.5u: 1454
      • 1.0u: 872
    2. Zone 4:
      • 0.3u: 1662
      • 0.5u: 706
      • 1.0u: 290
        Reply  Thu Apr 27 21:43:07 2023, Jon, Physics, VAC, Grounding vacuum system IMG_0141.pngIMG_0140.png

    This afternoon I made up a green 10 AWG grounding cable and connected it to the vacuum system.

    One end is tightly connected to the bottom flange of the vacuum chamber (photo 1). It is run along and up the table framing to the top of the cleanroom, where it exits into the overhead cable tray in the same location as the other power cables. It drops down from the top of the server rack all the way to the bottom, where the other end is connected to the lab's electrical ground in the rear of the 240 V UPS (photo 2).

    The connections were confirmed to be secure, but continuity testing with an ohmmeter remains to be done to confirm that the chamber and tabletop are indeed grounded.

        Reply  Fri Apr 28 18:16:57 2023, Cao, Physics, VAC, Grounding vacuum system 

    Quote:

    This afternoon I made up a green 10 AWG grounding cable and connected it to the vacuum system.

    One end is tightly connected to the bottom flange of the vacuum chamber (photo 1). It is run along and up the table framing to the top of the cleanroom, where it exits into the overhead cable tray in the same location as the other power cables. It drops down from the top of the server rack all the way to the bottom, where the other end is connected to the lab's electrical ground in the rear of the 240 V UPS (photo 2).

    The connections were confirmed to be secure, but continuity testing with an ohmmeter remains to be done to confirm that the chamber and tabletop are indeed grounded.

     

    [Cao]

    Continuity Test

    Following from Jon's grounding work on the vacuum system, I did a continuity test with the afternoon with a multimeter. The chamber is indeed grounded:
    • Chamber wall to optical table: continuity confirmed, resistance: 0 Ohm
    • Chamber wall to ground point connection on chamber: continuity confirmed, resistance: 0 Ohm
    • Turbo pump to ground point connection on chamber: continuity confirmed, resistance: 0 Ohm
    • Turbo pump to optical table: continuity confirmed, resistance: 0 Ohm
    • Optical table to chassis frame outside cleanroom: continuity confirmed, resistance: 0 Ohm
    • Front of chassis frame to earth point: continuity confirmed, resistance: 0 Ohm

    Entry  Fri Apr 28 19:00:13 2023, Cao, Physics, VAC, Tighten CF ports on vacuum chamber TightenCF.png
    [Cao]

    After Jon's comment yesterday that some of the connection did not seem to have good metal-metal contact, in particular the gate valve connection, I went through the ConFlat connections today and retighten them. I found a lot of the CF connections are not particularly tightened and there were a lot of range left that can be tightened with the wrench. After re-tightening, the copper gaskets are not visible anymore. For example, see the attached images for the difference before and after tightening.

    Note for future installation of CF

    • After tightening the bolts/ screws in jumping order (to provide uniform torque) and there is resistance appearing in further tightening, start going through each screw/ bolts in a direction, each time applying a small torque until it resists to further tightened
    • After each time going all the bolts/ screw and returning to the starting point, one will find they can further tighten the screws/ bolts. Repeat the process until no further tightening can be achieved
    • The copper gasket should not be clearly visible at the connection

    Entry  Mon May 1 17:10:25 2023, Julian, Cao, Physics, VAC, Installing Pirani gauge and RGA probe onto to vacuum chamber PXL_20230501_225241491.jpgPXL_20230501_235854958.jpgPXL_20230501_234750795.MP.jpg

    [Julian, Cao]

    • 03:00 pm: Particle count
      1. : Zone 3
        • 0.3 um: 498
        • 0.5 um: 124
        • 1 um: 124
      2. : Zone 4
        • 0.3 um: 748
        • 0.5 um: 457
        • 1 um: 374
    • 03:32 pm: Installing Pirani gauge onto pump line
    • 03:51 pm: Finish installing Pirani gauge, start installing RGA probe
    • 04:03 pm: Finish installing PRGA probe, start routing cable from gauge controller to Pirani gauge
    • 04:30 pm: All ethernet cables are routed and connected to gauge controllers
    • 04:48 pm: Power gauge controller up, all gauges are recognised and readout shows atmospheric pressure as expected (1000 mbar)
    • 04:51 pm: End-of-work particle count
      1. : Zone 3
        • 0.3 um: 1413
        • 0.5 um: 872
        • 1 um: 623
      2. : Zone 4
        • 0.3 um: 374
        • 0.5 um: 166
        • 1 um: 166
    We also closed all the valves so we can start testing vacuum pump down of isolated volume tomorrow.

    Entry  Tue May 2 17:03:14 2023, Jon, Cao, Physics, VAC, First pump-down test of vacuum chamber PXL_20230502_203343616.jpgPXL_20230502_210234897.MP.jpg

    [Jon, Cao]

    1. Re-routing of cables

    We re-routed the connections between the turbo pump and its fan to the controller. Instead of going through the side of the server rack, they are now routed along the the cable tray and came down from the top of the server rack.

    2. Planning for vacuum assembly re-configuration

    While preparing for our first pump-down, we notices that RGA pump line gate valve, at its fully closed position, is higher than the height of the chamber lid. The full range gauge attached to the RGA line, while not that high, can also cause obstruction during removal/ installation of the vacuum lid. The calibrated leak, eventhough is now running within the perimeter of the optical table, it stills introduce weak points that are susceptible to damage if personnel installing chamber lid may lean onto it. Thus we made a few suggested modification to the vacuum chamber assembly:
    • Move the entire RGA arm to the mirrored CF port, where the Up-to-Air valve is at
    • Move the Up-to-Air valve to the calibrated leak port
    • Move the calibrated Ar leak the main chamber full-range gauge port
    • Move the full-range gauge to the RGA line port

    3. First test pump-down

    1. With all valves closed, we started scroll pump, pump line quickly got down to 6.08 mbar from atmospheric 1000 mbar (measured by Pirani gauge, channel 3 on controller )
    2. We open Lesker angled valve and let the RGA arm pumped down, Pirani gauge read 6.3 mbar while the full-range guage on RGA line reads 4.9 mbar ( channel 1 on controller )
    3. We open the pump line gate to expose the pump to the main volume, all gaugues readout immediate rise back up 1000 mbar. After 3 minutes, we started to see channel 3 slowly dropped down. A minute later channel 1 and 2 (main body) also dropped down. The slow pressure dropping speed and 6.3 mbar measured earlier got us suspected that there is some large leaks
    4. We proceed to tighten all the ports as the vacuum is pumped down. In particular, we found that large feedthrough port still required a lot of tightening up
    5. As we tighten up all the ports, after 40 minutes, the gauges are now
      • Channel 1 : RGA line full-range gauge: 2.55E-1 mbar
      • Channel 2 : Main chamber full-range gauge: 2.60E-1 mbar
      • Channel 3 : Pump line Pirani gauge: 2.94E-1 mbar
      Compare this to the scroll pump manual , Table 1, page 3, the ultimate pressure of the scroll pump is 2.5E-1 Torr (3.3E-1 mbar), we thus managed to achieve scroll pump ultimate pressure
    6. Turn on turbo pump : Change turbo pump controller from REMOTE to FRONT PANEL mode by pressing both "COUNTERS" and "MEASURE" buttons at the same time, select "MODE=FRONT"
    7. Shorting interlock pin: since we do not have an interlock signal for the controller, use the provided DB-9 connector that has pin 3 and 8 shorted and connect this to the P1 IN connection at the rear of the controller (see attachment 1 )
    8. Press "START" on the controller to start the turbo pump
    9. The pressure readout from the gauges quickly dropped down. After 3 minutes, the Pirani range is maxed out at 0.5E-3 mbar. After 20 minutes, we recorded the following values:
      • Channel 1 : RGA line full-range gauge: 1.50E-5 mbar
      • Channel 2 : Main chamber full-range gauge: 1.89E-5 mbar
      • Channel 3 : Pump line Pirani gauge: 5.0E-4 mbar
      This is Medium vacuum , we want to further reduce this by 2 orders of magnitude. However, we can run RGA test + helium leak test at this pressure
    10. Turn off turbo pump, wait for 10 minutes, turn off scroll pump, open Up-to-Air valve, all pressure gauges indicated pressure returned back to atmospheric pressure

    3. To-do actions

    • Run RGA test to get information about contamination status of vacuum
    • Implement suggested changes in section 2
    • Check and modify suspected poor connection: Pirani gauge on pump line. A gap can be seen between connection. There's no good way to tighten it with the screw. Maybe use threaded pin + hex bolt?
    • Controller communications
    Entry  Wed May 3 19:03:47 2023, Julian,Pamella and Cao, Physics, VAC, Modify vacuum asssembly and install RGA vaccum_chamber_re-configuration.jpg
    [Pamella, Julian, Cao]
      Today we started re-configuring the vacuum chamber components.
      Particle count
    • 10:45 am : Starting the particle count in the clean room.
    • 11:13 am : Finished the particle count in the clean room.
    • Zone 3 :
      • 0.3 u: 2535
      • 0.5 u: 1413
      • 1.0 u: 789
    • Zone 4 :
      • 0.3 u: 457
      • 0.5 u: 290
      • 1.0 u: 207
        Starting the reconfiguration.
      • 11:21 am: Started removing up-to-air valve
      • 11:30 am: Finished removing up-to-air valve.
      • 11:33 am: Started removing calibrated Ar Leak and the elbow.
      • 11:35 am: Finished removing calibrated Ar Leak and started assembling the up-to-air valve.
      • 11:47 am: Finished assembling up-to-air valve.
      • 11:48 am: Started removing magnetron gauge.
      • 11:55 am: Finished removing magnetron gauge.
      • 11:57 am: Started installing the elbow and calibrated Ar Leak and started removing the RGA probe
      • 12:13 pm: Finished installing the elbow and calibrated Ar Leak.
      • 12:20 pm: Break for lunch.
      • 01:25 pm: Come back from lunch break.
      • 01:30 pm: Started removing RGA line.
      • 01:39 pm: Finished removing RGA line.
      • 01:39 pm: Started removing gate valve [RGA line] and finished removing gate valve.
      • 02:00 pm: Started installing gate valve in the new position.
      • 02:08 pm: Fished installing gate valve [RGA line].
      • 02:09 pm: Checked the screws in the elbow to gate valve. [RGA line].
      • 02:28 pm: Finished checking the screws in the elbow to gate valve [RGA line].
      • 02:29 pm: Started installing RGA line.
      • 02:39 pm: Finished installing RGA line.
      • 02:50 pm: Started installing magnetron gauge.(In this part we assembled gauge with the used gasket)
      • 03:02 pm: Finished installing magnetron gauge.
      • 03:04 pm: Started installing RGA probe [RGA line].
      • 03:13 pm: Finished installing RGA probe [RGA line].
      • 03:15 pm: Connected the cables to the magnetron gauge.
      • 03:20 pm: Started the testing in the vacuum chamber.
      • 04:30 pm: Started installing the RGA 200 and connected the cables (power cable and DB9 cable).
      • 04:52 pm: Finished installing the RGA 200 and connected the cables (power cable and DB9 cable).
      • 04:53 pm: Started testing the RGA connections. Logrus is able to recognize and connect to RGA unit. We are leaving the turbo pump on for a few hours before checking back for pressure readouts.
      • 05:00 pm : Starting the particle count in the clean room.
        1. Zone 3 :
          • 0.3 u: 2244
          • 0.5 u: 997
          • 1.0 u: 207
        2. Zone 4 :
          • 0.3 u: 2993
          • 0.5 u: 1579
          • 1.0 u: 498
      • 05:30 pm : Finished the particle count in the clean room.
      • 05:34 pm: Test pressure readout from the gauges.
        1. Channel 1 : 1.06E-5 mbar
        2. Channel 2 :8.89E-6 mbar
        3. Channel 3 :5.0E-4 mbar
      • 05:59 pm: Test pressure readout from the gauges.
        1. Channel 1: 9.09E-6 mbar
        2. Channel 2: 7.75E-6 mbar
        3. Channel 3: 5.0E-4 mbar
        Reply  Tue May 9 15:49:20 2023, Jon, Infrastructure, VAC, Permanent cable routing 

    Today I brought in a fresh supply of zip ties (we now have 1500 in the tool chest) and used them to permanentize the cable routing for the gauges, pumps, and RGA.

    I also brought and installed a 3-foot 15A extension cable for powering the scroll pump. Installing the cable required shutting down the pumps, which I did and then reverted via the following procedure:

    1. Close the 4.5" gate valve, 2.75" gate valve, and the bypass line angle valve.
    2. Shut down the turbo pump.
    3. Shut down the scroll pump.
    4. Unplug the scroll pump and install the extension cable.
    5. Power on the scroll pump.
    6. Power on the turbo pump.
    7. Open all three valves.

    Incidentally, before I started, I noticed that the pressure in the main volume had reached 7E-7 torr, which is lower than the pressures seen last week. The system quickly returned to this pressure after I restarted the pumps.

    Entry  Tue May 9 20:55:12 2023, Jon, Infrastructure, VAC, Calibrated Ar leak rate VTI-Calibrated-Ar-Leak.jpeg

    For future reference, the calibrated Argon source has a leak rate of 7.55E-8 atm cc/s, or equivalently 5.74E-8 torr L/s. This can be used to calibrate RGA scans to units of physical leakage (outgassing) rate.

    Entry  Fri May 12 20:28:34 2023, Aiden, Cao, Physics, VAC, Vacuum chamber Helium leak test PXL_20230512_211717602.jpgArLeak_230512.png

    [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

    After finishing the Helium 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

    Entry  Tue Jun 13 21:08:46 2023, Pamella, Infrastructure, VAC, Heater system - Installation IMG_7563.jpegIMG_7561.jpeg
    [Pamella, Cao and Jon]
      Heating system installation
    • Today we started installing the equipments for the heating system.
    • First: Started installing the heating cable on the top lid and covered it with aluminum tape.
    • Second: Started installing the insulation cover on top of the chamber lid.
    • Third:Started installing the heating cable from under the vacuum chamber and covered with aluminum tape.
    • Forth: Started installing the insulation cover under the vacuum chamber
    • Note: The under part of the chamber vacuum was very difficult to cover, so we spent a little time on it and we couldn't finish the whole installation today. So tomorrow we should be able to keep doing the installation.
    Entry  Wed Jun 14 15:35:36 2023, Pamella, Update, VAC, Heating system installation  heater_equipment_install.jpg
    [Pamella and Cao]
      Heating system installation - Second day.
    • Today we kept installing the equipment for the heating system.
    • First: Started installing the two heating cable around the chamber vacuum, the arms and covered it with aluminum tape.
    • Second: Started installing the insulation stuff around the vacuum chamber and around the connections points (the arms) in the vacuum chamber.
    • Third:Started installing the heater system (electronic device) and tried testing.
      • Note: The around part of the chamber vacuum was difficult to cover, so we spent a little time on. Also one heater system electronic device wasn't working because one fuse is burned so we could not finished this part and we need wait for a new one to replace and working on it.
    Entry  Tue Jun 20 22:14:24 2023, Pamella, Cao, Infrastructure, VAC, Short term testing of vacuum heater controller units 
    [Pamella, Cao]

    Fuse replacement

    • Replace blown 10A fuse in ucontroller outside cleanroom
    • Replace 10 A fuse in main power connection slot of the controller unit inside cleanroom
    • Pamella wiped down unit outside cleanroom.
    • Controller units turned on and temperature setpoint set to be 80 deg C
    • Temperature settle in approx. 15 minutes(as recorded by the RTD). No problems with fuses observed
    • Recording of pressure gauges (in Torr) :
      1. Before turning heater on :
        1. Gauge 1(main chamber): 3.73E-7
        2. Gauge 2(RGA line): 3.65E-7
        3. Gauge 3(Pump line): 3.8E-4
      2. After 15 minutes :
        1. Gauge 1(main chamber): 7.07E-7
        2. Gauge 2(RGA line): 6.12E-7
        3. Gauge 3(Pump line): 3.8E-4
    • Reduce setpoint temperature to 60 deg C due to Pinrani gauge (Gauge 3) temperature limit
    • Upon returned to lab to reduce temperature (35 minutes after turned on):
      1. Gauge 1(main chamber): 1.22E-6
      2. Gauge 2(RGA line): 9.98E-7
      3. Gauge 3(Pump line): 3.8E-4
    • Once temperature has settled to 60 C (approx 20 mins after changing setpoint), pressure readout showed:
      1. Gauge 1(main chamber): 1.37E-6
      2. Gauge 2(RGA line): 1.10E-6
      3. Gauge 3(Pump line): 3.8E-4
    • Heater left on for the whole afternoon, pressure readout upon returning to lab at 5:30 pm:
      1. Gauge 1(main chamber): 3.43E-6
      2. Gauge 2(RGA line): 2.61E-6
      3. Gauge 3(Pump line): 3.8E-4

    Entry  Wed Jun 21 20:25:05 2023, Cao, Infrastructure, VAC, Vacuum chamber bake attempt 1 6x

    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)
    • 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

        Reply  Tue Jun 27 21:47:56 2023, Jon, Infrastructure, VAC, Vacuum chamber bake attempt 1 IMG_0256.pngIMG_0257.pngIMG_0254.png

    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.

    Entry  Wed Jun 28 15:58:56 2023, Shane, Cao, Infrastructure, VAC, Power trip problem remains, source of smoke is insulation Pumpline_afterRemoveInsul.jpgRGAline_afterRemoeInsul.jpgMeltedInsulation1.jpgMeltedInsulation1.jpgMeltedInsulation2.jpg
    [Shane, Cao]

    With the new change in wiring configuration described in elog 136, we tried to power up the heaters for baking the vacuum chamber again.

    Given that we were worried about the turbo pump overheats, we set the setpoints of of bother high temperature controller and PID controller to be 120 deg C before turning the heaters on

    1. Evidence of smoke originating from CoolSkin insulation

    We then removed most of the CoolSkin insulation on the Pump and RGA lines ( apart from the one around the flexible bypass line connecting the two ) (see image Pumpline_afterRemoveInsul and RGAline_afterRemoeInsul) . Upon removal of the insulation, we noticed that the insulating foam melted onto the heating tape (see image MeltedInsulation1 and MeltedInsulation2). This is the first indication that the smoke had most likely coming from the insulating foam itself

    Once we started baking, upon reaching 80 degree range. We observed no smoke at the location that we removed the insulation. However, We observed smoked coming from underneath the insulation around the flexible pipe, and not from the velcro areas.

    What could be causing this, given that the maximum operating temperature of the insulation is 200 deg C? Most likely, the heating tape is much hotter than we think it is. But given that the temperature sensor readout is much lower than 200 deg C, it's likely that this is due to poor thermal contact and it takes a while for sensor to reach a thermal equilibrium with the heating tape. Here, I suggest we should implement the following:
    • We should look into usingsome form of thermal tape (if possible to secure the temperature sensors)
    • Unfortunately or controller does not allow programming process, we will have to implement manual temperature stepping, emulating ramping process over the first hour, until slowly reach 120 deg C
    • OR Tune the PID controller coeffs, especially P and I for longer rise time and settling time

    2. The heaters still trip our power

    Upon reaching 80 deg C,our main power trip. Unfortunately I don't know how to reset this. Do we need to contact facility on this? Reading elog 136, I noticed that both controllers are connected to the same circuit LP3B 6, which is the same circuit the some of the fan-filters and LED light panels of the cleanroom connected to. From the elog, the circuit has a 20 A limit . An max operation, the 2 heater controllers draw 30 Amps, approx 7 Amps for the fan-filters, and another 1.5 A for LED panel. The combination of these equipment must have overload the circuit and tripped it . Currently half the fans + lights are off in the cleanroom are off due to power trip. Here, I would make a suggestion that each heater controller should be connected to a separate circuit . Currently we LP3B 7 (same side next to LB3B 6) and LB3B 4 (opposite side of the rail) having no equipemts connected to them, but will require cable extensions.
    Entry  Thu Jun 29 18:27:26 2023, Jon, Cao, Infrastructure, VAC, Vacuum bake attempt 3: success! NewInsulation.pngBypassLineInsulation.jpg
    [Jon, Cao]

    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

    We started ramping up chamber temperature at 1:41 pm over the course of two hours:
    • 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
    We noticed some smoke emanating from flexible bypass line insulation but none from other locations that were previously smoking . We think this is because the high winding density around the bypass line for such a small volume. Adjustment for next bake: Change the location of PID controller RTD to the bypass line . For now, we remove the insulation around bypass to prevent insulation overheating and encourage convection cooling (see image)

    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.

    Entry  Mon Jul 3 14:32:24 2023, Cao, Infrastructure, VAC, Cooling down vacuum chamber 
    [Cao]

    After leaving the the chamber to bake at 120 deg C from Thursday 3:41 pm. Today I started to cool the chamber down to room temperature at 11:30 am (total bake duration: 91 hours 49 minutes). Ideally, this process should be ramped down slowly, approx. 6 degree per hour. However we had no ramping function with out controller. The only method to tune this cool/ heat rate is to tune the PID parameters, which are:

    1. Pb : Proportional band, this quantity is inversely proportional to the P-gain
    2. ti : Integral time. Increasing integral time makes the output response slower to error, thus the opposite effect of increasing integration gain
    3. td : Differential time
    Since the differential term doesn't contribute to rise time significantly, we neglect it for now and first change Pb and ti . The factory default settings :
    1. Pb : 50
    2. ti : 100 s
    3. td : 25 s
    Initially Ichanged Pb from 50 to 200 (max) and ti to 999 s (max) but there is a large offset error. Currently, Pb and ti are sitting on the following settings:
    1. Pb : 200
    2. ti : 800 s

    At this setting it takes 25-30 mins to drop 6 degrees, which is not as slow as we want but we will have to tune our PID more carefully. At the first stage, I dropped the temperature to 60 deg C. After 3 hours, we dropped the setpoint to 25 degrees and let the vacuum chamber to cool to room temperature.
    Entry  Wed Jul 5 15:46:47 2023, Aiden, Cao, Infrastructure, VAC, Vacuum Chamber Baking Update bake1_230705.png

    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.

    Entry  Thu Jul 6 16:16:03 2023, Aiden, Summary, VAC, Vacuum Chamber Baking Update 

    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.

    Entry  Fri Jul 7 15:11:39 2023, Aiden, Update, VAC, VAC System Heating Update 

    The temperature of the flange connecting to the turbo pump after reaching equilibrium is 74 degC. This means that it is safe to proceed with raising the temperature from 120 degC to 150 degC.

    Raised the set temperature of the chamber from 120 degC to 150 degC in 15 deg steps.

    Goto page 1, 2, 3 ... 8, 9, 10   Next  
    ELOG V3.1.3-7933898