20-610 3kV Adjustment

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The 20-610 high voltage gun supply used on PHI 600 and 660 scanning Auger systems provides the beam voltage, filament current and emission voltage to the Lab6 filament in the cylindrical mirror analyzer.

As part of the linearity adjustment process, the beam voltage is set to 3 keV so that the top of the elastic peak comes in at 3 keV.

The 3 keV elastic peak adjustment potentiometer in the 20-610 is R108.   The process is simple:

  1. Adjust the specimen stage Z axis for maximum counts and best shape of the peak during a 3 keV elastic peak alignment.
  2. Adjust the analyzer control gain so that the AES peaks come in at the correct location in a survey. Typically clean copper is used since it has both low and high energy peaks.
  3. Reacquire the elastic peak but do not move the specimen stage. If the elastic peak does not come it at 3 keV, move the elastic peak to 3 keV by adjusting R108 in the 20-610.

Sometimes there is not enough range of adjustment with the R108 potentiometer.  For those cases, this blog post will explain how to modify the PCB 100 board in the 20-610 in order to extend the 3 kV adjustment range.

The schematic below shows the R108 potentiometer circuit.

R108 Pot

The ends of R108 are connected to + and – 12V via two 49.9 K ohm resistors, R107 and R109. Adjusting R108 adds a small offset current to IC 103, which in turn changes the 3 kV output of the 20-610.

If there is not enough range with R108 then we need to change the balance between the + and – 12 volt supplies.   The way to do that is to remove R107 and replace it with a 100 k ohm trim potentiometer that is set to an initial value of 49.9 K ohms. 100 K ohm trim pots are available from any electronic component vendor (Digikey, Newark, Mouser….)

To prep the 100 K ohm trim potentiometer, the center wiper connection needs to be soldered to either end as shown below.

Bend center pin

With an ohmmeter, measure the resistance between the trim pot legs and adjust it for a resistance of 49.9 K ohms.

Turn off the 20-610 and on the back of the unit, unplug the main power cord, the remote program cable and the unscrew and remove the large HV cable connector. If there is a ground wire attached, remove it as well.

Place the 20-610 on a work bench and remove the 100 board. You will need to remove the board tie down bracket. Important! – Make sure that the 20-610 in unplugged when removing or installing the board tie down bracket as it is very close to some exposed wires that have voltage on them when the 20-610 is plugged in.

 

R100 board location in 20-610

remove bracket

 

 

 

Unsolder R107 and install the new trim pot on the back side of the 100 board.   You will need to bend the two pins on the trim pot so that the adjustment screw faces up.

R107 resistor

Reinstall the 100 board inside the 20-610.  Make sure that it is seated all the way into the mother board connector. Reinstall the board tie down bracket. Do not put the cover back on the 20-610.

Install the 20-610 into the electronics rack and reconnect the large HV cable (be sure to screw it in all the way), and the HV programming cable.  Make sure that the 20-610 main power switch is  OFF and then plug in the main power cord into the interlocked power strip.

Slide the 20-610 out enough so that you can get to R108 and the new trim pot.  Make sure that the 20-610 main power is OFF.

Remove the filament cap from the analyzer (3 screws) and connect a DVM and high voltage probe to either of the filament tabs.  The ground reference on the high voltage probe should be connected to the vacuum chamber.

 

***Caution, high voltage is present! Refer adjustment to qualified personnel ***

Turn on the 20-610 and using AugerMap and the normal turn on procedure, set the beam voltage to 3 kV.

***Caution, high voltage is present! Refer adjustment to qualified personnel ***

Center R108 and then adjust the new 100 K ohm trim pot so that the voltage on the filament cap is 3,000 volts.

Turn off the beam voltage in AugerMap and then turn off the 20-610.

Reconnect the filament cap to the analyzer.  Press down on the cap as you tighten the 3 screws that hold the cap onto the top of the CMA filament adjustment housing.

Turn the 20-610 back on and turn the beam voltage on and set it to 3 kV.  Bring up the filament current to the normal operating point (typically 1.3 amps)

Perform the AES calibration procedure and adjust R108 so that the elastic peak comes in at 3 keV.   When you are finished with the AES calibration, put the cover back on the 20-610 (front 2 cover screws only) and slide it back into the console.  The AES calibration procedure is listed below –

Auger energy calibration on 600 and 660 scanning Auger systems

This procedure requires sliding the 20-610 high voltage supply out and removing the cover to gain access to the beam voltage offset potentiometer, R108. Turn off the 20-610 when sliding it in out or in, and when removing or installing the cover.

Procedure:

  1. Load a sample of pure copper.
  2. If you are using AugerMap software, set the magnification to 10,000X and use the Area Scan mode to minimize sample topography effect on the Auger signal.
  3. Perform an elastic peak alignment and adjust the Z axis sample position to obtain maximum counts and best peak shape.
  4. Sputter the sample clean until no carbon or oxygen is present.
  5. Re-acquire the elastic peak to ensure that the sample is at the optimum position: highest counts and best peak shape. When the elastic peak is differentiated, the positive and negative excursions should be equal and symmetrical.
  6. From this point on, do not move the sample!
  7. With the beam voltage at 3kV, acquire a survey from 30eV to 1030eV, using .5eV/step, 50 ms/point.
  8. Differentiate the survey and check the peak positions against the correct values as listed in the PHI handbook or other reference. A typical value is 920eV for the high energy peak and 60eV for the low energy peak on copper.
  9. Note: If using AugerScan software, you can simply adjust the scale factor in the AES
  10. Acquire an alignment with a range of 900 to 940, .5eV/step, 15ms/point and do the adjustment in real time. For copper, set the n/e peak to approximately 917eV. When differentiated, the high energy Cu peak should be 920eV.
  11. Acquire another survey and check that the differentiated peak positions are correct. Document the results for future reference and file it in the system calibration log.
  12. Acquire another elastic peak, but do not move the sample!
  13. If the elastic peak is not centered at 3kV, then adjust R108 in the Bertan 20-610 High Voltage power supply to center the elastic peak.

Calibration is complete.

From this point on, every-time you set the elastic peak, the sample will be at the focal point of the analyzer (maximum signal and best shaped peak), and all of the Auger peaks will be in the correct positions.

New high speed 5kV floating Picoammeter

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RBD Instruments has released a new version of its 9103 USB Picoammeter which incorporates faster reads per second with 5000 DC volts of isolation to chassis ground.

9103 HV

9103 HV

 

 

 

 

 

 

 

 

Increasing the DC voltage isolation from chassis ground to 5000 volts (5kV) opens up new possibilities for researchers such as direct DC current measurement of very small electron and photo multiplier signals.  Electron and ion beam measurements can be biased to reduce secondary electrons or to retard the beam as needed for experiments.

Designed to provide accurate bipolar DC current measurements in noisy environments such as synchrotron beam lines, the 9103 can measure bi-polar DC currents from low picoamps to milliamps.

The drawing below shows how the 9103 is floated on your HV power supply.  The high voltage is referenced to chassis ground, and the signal ground is referenced to the high voltage.   To help keep the supply and signal connections clear, the HV connection is a MHV connector and the signal input is a SHV connector.

Floating picoammeter

Floating picoammeter

 

There are a number of manufacturers of programmable DC power supplies that can be used to float the 9103 up to whatever voltage is needed (as long as you do not exceed +/- 5 kV).

For example, TDK-Lambda provides a programmable 0 to 6.5kV supply that can be voltage limited to 5 kV and can drive up to 2 mA of current.

The model number for a 120 VAC line input is PHV6.5P2-USB-1P115.  The base model has a ripple of 700mV which is somewhat high, but TDK-Lambda does offer a low ripple option that gets the ripple down to 75mV.  You can also easily make a simple RC filter to do the same thing.    A number of interface options are available (USB, Ethernet, Serial, analog….

TDK Lambda supply

TDK Lambda supply

 

 

 

 

PHV series

PHV series

 

 

 

 

 

 

 

 

The new high speed option for the 9103 increases the reads per second from 40 to over 500, which is fast enough to perform optical chopper experiments.  And, by taking more reads in the same amount of time as the first generation 9103 could, the accuracy is improved.

The Actuel software included with the 9103 provides new features for high speed acquisitions and display, but you can also write your own software to control the 9103 using the simple ASCII commands or in LabVIEW.

Since 9103s can be synced, it is now possible to configure a multichannel DC Picoammeter with up to 256 channels that has high speed, high voltage, or both options.

And if you do not need the high speed or high voltage options, the standard 9103 USB Picoammeter is still available as well.

For more information visit the RBD Instruments website at http://www.rbdinstruments.com

 

04-500 Old style X-ray source filament conversion

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The very early PHI 04-500 and 04-548 X-ray sources used a small filament that had couplers to make the connection between the X-ray source and the filament.

04-500 04-548 old style filament

04-500 04-548 old style filament

 

 

 

 

 

 

 

 

 

In addition, the couplers were held in place with a notched ceramic that had a special pointed set screw which pressed into a copper wire that in turn made the connection to the electrical feedthrough on the source.

 

 

 

 

 

 

 

 

 

This connection scheme worked well enough as long as you set the filaments properly and did not ramp the current up too quickly.  Even then, the filaments were prone to warping out of shape over time.  Also the couplers could loosen up and then the filaments would short out.

PHI’s solution was to redesign the filament where the filaments were brazed into a ceramic base instead of using couplers.  This resulted in a very stable filament base where the filaments can’t move at all and so they no longer warped out of position (unless you ran the filament current up too quickly).

Recently I updated an older 04-500 X-ray source from the old style to the new style filaments.  You can see the before and after in the pictures below.

old 04-500

Old Style 04-500 X-ray source

new 04-500

Updated 04-500 X-ray source

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This update will result in more stable X-ray source operation and extended filament lifetime.

The new style filaments cost more than the old style filaments by quite a bit.  But factoring in the improved performance, longer lifetime and reduced downtime it may be worth the additional cost.

If you have an old style source please keep this filament conversion in mind the next time you need filaments or a complete source rebuild.

Contact RBD Instruments for more information.