Leak Testing on Mass Spectrometers

Description

If there is a potential leak in a mass spectrometer it is best to systemically rule out locations for the leak. In general you start with a rate of rise and systemically open up and close valves until you think you have found the general location of the leak. At that point you will need Argon gas to spot check locations within that region.

Procedure

  1. Perform a Rate of Rise until it become clear where the general area of the leak is coming from.

  2. Use Argon to test seals in the suspected area.

  3. If the leak is small it make take a few minutes for the argon to make it’s way into the system. Spend around 4 minutes in each area.

  4. If there is a leak, there will be a spike in m40.

Rate of Rise

Description

This procedure is used to establish a general background level gas in the mass spectrometer. The procedure starts by isolating the mass spectrometer and closing the valve to the ion pump, allowing to gas to start building up in the mass spectrometer. The signal should slowly start to rise as gas starts building up from the sidewalls of the mass spectrometer. Before opening the extraction line up to the mass spectrometer, close the valve to the ion pump connected to the extraction line.

Procedure

  1. Set the mass spec into the configuration shown in Figure xx.

  2. Turn off Monitor Mode in ArArExperiments.

  3. Go to Scan Settings and set Integration Time to 0.52 s.

  4. In Intrument Control go to Graph View and click Reset Chromotagram and Set Time Zero.

  5. Double click H1 on the graph and then double click the graph. It should now be reading the signal on H1.

  6. Close the valve to Ion Pump Mass Spec.

  7. Sample Chamber Configuration:

    1. If sample chamber valve already open to prep system, close valve between chamber and prep system.

    2. If sample chamber is valve closed and opening it to the system, leave valve open.

  8. Establish a rise for 120 s.

  9. Close Ion Pump Prep System.

  10. Let gas accumulate for another 120 s.

  11. Sample Chamber Configuration

    1. Open valve to the sample chamber.

    2. Open manual valve to sample chamber. Watch the graph to make sure there isn’t too much gas being let into the mass spectrometer.

  12. Let gas accumulate for another 120 s.

  13. Zoom in on the chromotagram over 60 s time period and calculate the accumulation of gas over a that time period.

  14. Record a screen shot and the rate of rise number in fA/min into the respective Teams Channel for the mass spectrometer that is being worked on.