You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 5 Next »

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, 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

Figure 2. Leak Valve 

Figure 3. Calibration Percentage Calculations

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. Leaving it 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. 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.
    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. Do not open the valve to the RGA head!
  10. If turbo and pump are separately operated
    1. 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 10-7.
    2. 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. This would be an indication that the RGA was last vented (oops!).

Software Guide:

  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.
  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. 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. 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
    1. Spreadsheet: https://docs.google.com/spreadsheets/d/15D6ebvvUcVcYYJx70cF8eDa5uTvCGoae9l0nPlBS-ts/edit?usp=sharing 
      1. Example on Cart 2 Tab, at the top (reference Figure 3). 

Step 1: Faraday Calibration

  1. Close the EasyView window and select the Faraday calibration and hit next
  2. In the next window, be sure that the correct RGA head is selected and hit next. 
  3. 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
  4. 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.
  5. 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.
  6. 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 Calibration

  1. Select the multiplier calibration button  and hit next.
  2. Choose 'Multiplier 1' and hit next



Related Documents







  • No labels