Amplifier Discriminator Tests

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One of the troubleshooting techniques that can be used to test the counting circuitry of an auger or XPS system is called “tickling the brick”.   The term came about from when the early PHI systems used the Princeton Applied Research (PAR) 1120 amplifier discriminator for pulse count detection of electrons. The 1120 kind of looked like a brick, and so the term “tickling the brick” was born.

Basically, tickling the brick tests the brick (amplifier discriminator) and the counting circuitry.   This is one of the first troubleshooting steps that you would take if you are not getting any counts at all with your auger, XPS or SIMS system.

The 1120 amplifier discriminator is still in use on many PHI systems, as is its newer replacement, the 1182.  The 1120 and 1182 are used with single channel detectors.

In addition to the 1120 and 1182 amplifier discriminators, the “tickling the brick” concept can also be applied to PSD and MCD detectors on XPS systems.

The procedures for each amplifier discriminator type are described below.

Amplifier-Discriminator

1120/1182 Test Procedure

  1. Set up a alignment (can be any range) and select the 1120/1182 as the signal input. For most PHI systems using AugerScan software, that will be PC1 input in the hardware properties dialog box.
  2. Remove the bnc input that goes between the analyzer and the 1120/1182
  3. Turn off the analyzer control and electron multiplier supply as they are not needed.
  4. Start the alignment acquisition and then stick a piece of wire into the bnc input of the 1120/1182. This wire will act like an antenna and you should see between 20 million and 30 million CPS of noise.
  5. Remove the wire and the counts should go to zero.

If the counts behave as expected then both the 1120/1182 and the counting circuitry are working properly.

PSD Position Sensitive Detector Preamp Test Procedure

PSD

PSD

 

 

 

 

 

 

 

 

  1. Set up an alignment (can be any range) and select the PSD as the signal input. For most PHI systems using AugerScan software, that will be the PSD input in the hardware properties dialog box.
  2. Turn the card rack power OFF.
  3. Remove the bnc inputs to the PSD that goe between the analyzer and the PSD. These are the little white wires that go from Preamps A and B to the analyzer.
  4. Connect a test clip to the center pins of each of the little white wire bnc connectors.
  5. Start the alignment acquisition and then with your fingers touch the ends of both of the test clips that go to the center pins of each of the little white wire bnc connectors. The test clips will act like an antennae and you should see about 50K to 80K CPS of noise. Both clips need to be touched at the same time. NOTE: The clips go to the wires, not the BNC connectors on the analyzer.
  6. Remove the test clips and the counts should go to zero.

If the counts behave as expected then both the PSD preamp and the counting circuitry are working properly.

Make sure that the card rack power is OFF when you reconnect the PSD cables to the analyzer.

MCD Amplifier/Discriminator Test Procedure.

MCD

MCD

 

 

 

 

 

 

  1. Set up an alignment (can be any range) and select the MCD as the signal input. For most PHI systems using AugerScan software, that will be the MCD input in the XPS hardware properties dialog box.
  2. Turn the card rack power OFF.
  3. Unscrew the MCD amplifier discriminator from the analyzer flange and carefully remove it. NOTE: Use care when reinstalling it after the test procedure to make sure you do not bend any pins. Also make sure that the card rack power is OFF when you reinstall the amplifier discriminator on the analyzer flange
  4. Turn on the card rack power and start the alignment.
  5. There are 20 socket connectors visible on the end of the MCD amplifier discriminator. Each of those connectors (except for the middle 4) represents one of the 16 channels that are connected to the MCD detector inside the analyzer.
  6. Start the alignment acquisition and then stick a wire into each of the open pins on the end of the MCD preamp, one at a time. The test clips will act like an antennae and you should see about 20K to 80K CPS of noise when the clip is inserted.
  7. Remove the wire and the counts should go to zero.
  8. Repeat steps 6 and 7 for each of the other pins on the end of the MCD amplifier discriminator.

If the counts behave as expected then both the MCD amplifier/discriminator and the counting circuitry are working properly.

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