This document will show you how to calibrate an MKS RGA device through 'Process Eye Professional'. Calibration will be needed when the collected data shows to much noise >46 AMU, or not defining 'Baseline-zero' accurately. When baseline-zero is not accurate, data in linear mode will show peaks beneath y-axis 0, after >46 AMU. Use Figure 1 as reference.

Figure 1. RGA Recall Screen of Cart #3 Data

a)      b)

Figure 2 (a) Leak Valve (b) Calibration Percentage Calculations Confluence- Calibr.



*Note: CCG must work, CANNOT do this work without it.

Initial Prep Guide:

  1. Gather equipment needed
    1. Leak valve
    2. Wrenches 
    3. Nitrogen tubing line
    4. Relevant Hardware
  2. Ensure Nitrogen Dewar is full, and/or is at least more than half full.
  3. Close-off RGA section with its respective valve
    1. Leaving it under vacuum
  4. Close-off turbo/roughing pump section with respective valve
    1. If cart 2: Turn off Turbo, leave roughing pump on
    2. Leaving that section under vacuum
  5. Connect nitrogen line to inlet valve with pressure relief valve
    1. Allow approximately 5 minutes for system to be backfilled with nitrogen
  6. Remove blank from RGA cart hose, and replace with leak valve (Reference Figure 2)
    1. Ensure nitrogen is flowing through the system before starting this step!
    2. Ensure leak valve is tightly closed before placing onto hose
  7. Once leak valve is tightly sealed/connected to hose, let the system backfill with nitrogen again
    1. Make the connection to the leak valve at the end of the hose, making sure to tighten bolts all the way until metal to metal contact is made.
    2. Backfill for approx. 3-4 minutes
  8. Close, and then remove nitrogen line from current position and relocate to it respective spot on the leak valve
    1. Ensuring the leak valve is tightly closed, so no nitrogen is flowing into the system
  9. Turn on the roughing pump+turbo. (Do not open the valve to the RGA head YET!)
    1. Monitor the pressure at the roughing pump by observing the pressure at the Pirani gauge(s) as you throttle the valve(s) which open the roughing to the system.
    2. Pump for approx. 3-4 minutes, wait for pressure to reach a value below 5*10-7
  10. If turbo and pump are separately operated- Cart 2
    1. Since turbo is off, go ahead and throttle open the roughing pump
    2. Ensure the CCG is working, CANNOT continue without it.
    3. Once the cart and hose pressure are below 10-2 torr, switch on the turbo pump and wait for pressure to reach a value below 5*10-7 or close to it.
    4. If pressure will not go this low, it is likely there is a leak somewhere on the cart or on the new connection
  11. Open the valve to the RGA head slowly while observing any pressure changes at the cold cathode.
    1. Pressure should equalize slowly. If pressure spikes, throttle the valve until the pressure equalizes.
      1. This would be an indication that the RGA was last vented or has off-gassed (oops!).

Software Guide:


*Important: RGA Sum of Calibration.ppt

  1. Log in to computer, go into 'Process Eye Professional' 
  2. Click on 'Recipe List', then click on 'Easy View'
  3. The RGA connected to computer through ethernet will have a distinct filled in symbol to its left. 
    1. This will open up an EasyView tab of respective RGA device
    2. If the device does not automatically connect, refer to this how-to document: https://confluence.slac.stanford.edu/x/dRoEEw
  4. Turn on the filament, and select analog data view (see section 10 of HPS document for more details on Process Eye Professional).
  5. Collect data for 5 minutes at accuracy 5 before continuing. At Accuracy of 3 is fine.
  6. Note the pressure at the cold cathode. Slowly open the leak valve until the pressure slowly starts to rise. Keep opening the leak valve until the pressure at the cold cathode reads 1e-6 torr.
    1. At this point the 28 AMU (nitrogen) should be the highest peak in the RGA scan.
  7. Open a bar graph and use the marker tool to select all the highest peaks on the graph. At accuracy of 6.
    1. Input the values to the provided spreadsheet to get the pressure that the RGA thinks it sees and to then get the percentage of the total pressure the nitrogen provides
    2. Spreadsheet: https://docs.google.com/spreadsheets/d/15D6ebvvUcVcYYJx70cF8eDa5uTvCGoae9l0nPlBS-ts/edit?usp=sharing 
      1. Example on Cart 2 Tab, at the top (reference Figure 3). Copy & paste calibration example to desired spot
  8. BEGIN CALIBRATION
    1. If you have issues connecting to RGA, or get following error, ensure RGA labeled IP matches the IP that ProcessEye assumed IP.
      1. If not, you will need to go into RGA Device Manager, and reconfigure the RGA
        1. 'Configure' Tab>Click on desired RGA>Insert (IP:Label IP)(Subnet: 255.255.0) (Gateway: Leave Empty)

Step 1: Faraday Calibration

  1. Close out Analog Spectra, Turn off Filament, Turn off Filament, CLOSE OUT EasyView .
    1. If easyview screen is open, rga can't be accessed during calibration, resulting in calibration error
  2. Select the Faraday calibration and hit next
  3. In the next window, be sure that the correct RGA head is selected and hit next. 
  4. Under “configuration name” select EasyView. This window will show you the current settings for the device that was selected in the previous screen. Write down these values (Current Faraday Sensitivity, last calibrated, Electron energy, Filament Emission, Ion Energy, and Extractor Volts). Hit next
  5. This window asks to select the mass peak to use for calibration. Type 28 into the field for the mass to be used for Faraday calibration and use the pressure at the cold cathode (1e-6 Torr) as the anticipated process pressure gauge reading. Use the calculated contribution percentage from the spreadsheet. Hit next.
  6. This window gives you various runtime options. Select:
    1. Run with no operator intervention
    2. Acquire data from the peak center only
    3. Apply the results of this calibration to both filaments.
    4. **** Double check that the pressure at the cold cathode still reads what you said the anticipated pressure gauge reading would be and if not open the leak valve slightly more and hit finish.
  7. Start collecting data in EasyView with the Faraday cup and wait until it gives a sum of scanned mass value. Compare this to the value at the cold cathode. If it is within a factor of 3 of the cold cathode then continue. If not, repeat the calibration.

Step 2: Multiplier 1&2 Calibration

  1. Close 'Process Eye Window' fully, and reopen.
  2. Select the multiplier calibration button  and hit next.
  3. Choose 'Multiplier 1' and hit next
  4. Select 'Use Faraday detector to determine the pressure at the calibration mass and hit Next
  5. Change the mass to be used to 28 and hit next
  6. Select 'Define the gain in terms of the exact gain
    1. Enter 50 for the Detector gain and hit Next
  7. Select 'Run with no operator intervention', 'acquire data from the peak centre only', and 'apply the results of this calibration to both filaments'
    1. Double Check that the pressure at the CCG still reads the anticipated value, if not, open the leak valve slightly to until CCG reads that anticipated value
  8. Hit Finish
    1. Note: If calibration stability is poor, calibration needs to be done again.
  9. Repeat M1 Steps 1-7 for Multiplier 2 calibration, except now entering 100 for Detector gain

Step 3: Multiplier 3 Calibration

**This step requires a lower pressure throughout the system, so close the leak valve, allowing systems to reach e-8's or e-9s regime. Mentioned regime is required for Multiplier 3 to function properly.

  1. Close 'Process Eye Window' fully, and reopen.
  2. Once in the e-8 or e-9 regime, Select the multiplier calibration button  and hit next.
  3. Scale to an externa, pressure gauge on the process Chamber
    1. Insert CCG Value
  4. Change the mass to be used to 28 and hit next
  5. Select 'Define the gain in terms of the exact gain
    1. Enter 200 for detector gain
  6. Select 'Run with no operator intervention', 'acquire data from the peak centre only', and 'apply the results of this calibration to both filaments'
    1. Double Check that the pressure at the CCG still reads the anticipated value, if not, open the leak valve slightly to until CCG reads that anticipated value
  7. Hit Finish
    1. Note: If calibration stability is poor, calibration needs to be done again.

Step 4: Testing Calibration Status/Effectivity

**For pressures lower than 1e-7, multiplier 3 should be used for scanning.

  1. Collect data, about 4 scans, in accuracy 5, with Multiplier 3.
  2. Observe the pressure (sum of scanned masses) at the RGA head
  3. It should now be within a factor of 2 of the CCG
    1. If this is not the case, repeat the calibration process for the multipliers, increasing or decreasing the gain depending on if the pressure reads to low or too high, respectively
  4. Collect 2 hours of data (preferrably 12-24hrs), Accuracy 6, and report RGA data/status to Peter, and later to ServiceNow
  5. Insert Calibration result into Google spreadsheet under 'Cart Qual Status' and to its respective Cart Tab.









EXTRA HELPFUL INFORMATION:

Valve positions:

                                     open                                                                                                close

                         


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