Author Archives: Randy

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.

BCF Database for AES

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Version 1.0 of the Backscattering-Correction-Factor Database for Auger Electron Spectroscopy program provided by NIST provides BSFs of homogeneous materials.

From the NIST website: This database provides values of backscattering correction factors (BCF) of homogeneous materials for quantitative surface analyses by Auger electron spectroscopy (AES). These BCFs are obtained from Monte Carlo simulations based on two models of electron transport in the material, a simplified model and an advanced model. One assumption for the former model is that the primary-electron beam is unchanged, in intensity, energy or direction, within the information depth for Auger-electron emission. This assumption becomes progressively less useful as the primary energy becomes closer to the core-level ionization energy for the relevant Auger transition or for increasing angles of incidence of the primary electrons.

BCFs can be calculated from both models so that users can readily ascertain the magnitudes of differences in BCFs from each model for materials and analysis conditions of interest. Analysts can readily specify the experimental conditions of interest (primary-beam energy, primary-beam angle of incidence, and, for the advanced model, analyzer-acceptance solid angle), the likely or estimated sample composition, the subshell of the element to be ionized, one of three available formulae for the inner-shell ionization cross section, and, for the advanced model, the Auger-electron transition of interest. The user can also select different numbers of trajectories in the Monte Carlo simulations so that tradeoffs can be made between calculation time and precision of the resulting BCF value. While simulations with the simplified model are generally faster than those with the advanced model, BCFs from the advanced model are considered more reliable. The results of a BCF calculation can be stored in a file for later use.

System Requirements: Personal computer operating on Windows 95, 98, NT, 2000, ME, XP, Vista, or 7, and hard disc space of at least 50 MB.System

Price: No Charge

You can download the program here – https://www-s.nist.gov/srd_online/index.cfm?fuseaction=home.main&productID=SRD154

 

25-110 Analyzer Filament

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This is an old tech tip that I wrote back in 2002. The 25-110 analyzer was the first CMA that Physical Electronics used a Lab6 filament in. These days there are not a lot of 590 systems still in operation, but the ones that are still work well especially as depth profile instruments. RBD provides Lab6 filaments and repair services for the venerable 590 scanning auger systems and the 25-110 analyzer.

General tips:

Use gloves.

Clean and demagnetize all of your tools.

Place all removed parts on a clean work area covered with aluminum foil.

If possible, dust off all parts with nitrogen as you re-assemble them.

Never force any part that doesn’t want to go.

Use methanol as a lubricant if screws don’t move easily.

 

To replace the filament in the 25-110 analyzer:

  1. Remove the magnetic shield (4 screws).
  2. Carefully remove the conical ceramic ring (4 flat-head screws) and remove the conical ceramic.
  3. Remove the outer cylinder (1 screw), being careful not to force it. If necessary, use a heat gun to loosen it up.
  4. Separate all of the wires in the bottom of the analyzer using 2 needle-nose pliers or tweezers. Be careful not to stress the wires.
  5. Position the wires so that you can easily remember where they belong. In the case of the F1 and F2 wires, this is easy. For the DELF/STIG wires, position the wires as upper right and upper left, lower right and lower left.
  6. Loosen the 4 spline set screws on the top of the inner cylinder by 1 turn CCW.
  7. Remove all but one of the 8 screws around the middle of the inner cylinder.
  8. Remove the upper inner cylinder grid cap (4 set screws).
  9. Holding on to the nose of the electron gun, remove the final screw at the middle of the inner cylinder.
  10. Carefully pull the electron gun up and out of the inner cylinder. Be careful not to stress any of the wire connectors.
  11. Place the electron gun on a sheet of aluminum foil.
  12. Loosen the bottom cap of the electron gun (4 screws and 4 set screws).
  13. Carefully slide the bottom cap down the ceramics for about 2 inches, enough room to get at the filament.
  14. Remove the filament assembly (4 cap screws, 2 splines connecting the filament wires).
  15. Install the new filament assembly and reverse all of the above steps.
  16. When you slide the electron gun ceramic tubes back down inside the analyzer be careful not to crimp the copper foil on the ceramics.  Also make sure that you tighten the set screws to hold the copper foil in place. If the copper foils slides up the ceramic it may cause arcing in the electron gun.

 

 

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