10/16/2012

1

AMS Tips, Tricks & FAQ’s

Ed Fortner, Bill Brooks, John JayneAMS User’s Meeting 2012

10/15/12

Leak Checking Tips

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Nor

mal

Leak

If the Airbeam (m/z 28,32,40) has a diff/closed ratio of < 2 you probably have a leak.

One can further get a clue as to where the leak is by carefully looking at your closed anddifference Airbeam.

If the leak is in the PToF region, the difference Airbeam will be attenuated and the closed AB will not be changed too much from normal.

If it’s in the detection region, the difference ABwill be about the same as normal, but the closed air signal will have an elevated background.

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Using ToF as Leak Checker

• He or Ar are good choices.

• Using He may require a change in the timing window.

• Use controlled bursts of gas, don’t “flood” system.

• Depending on where the leak is, may need to wait several seconds for a response.

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Doesn’t work as well here… But leaks here will cause a higher Backing Pressure

Consult Pump Currents, Lens and Backing Pressures to get a clue of where to look

Inlet

What are the operating currents for all pumps?

Gas Load Off (mA)

Gas Load On(mA)

Delta T* (Degrees C)

(Closed/Open)

P2 ~ 450 ~ 850 9/13.3

P3 ~ 250 ~ 300 9/9.3

P4 ~ 200 ~ 250 6/5.9

P5 < 200 < 200 6.2/6.5

P6 ~ 200 ~ 200 9.6/9.6

*Delta T = Pump Temp – Ambient Temp

10/16/2012

5

Filament Installation

Install filaments such that they are as parallel as possible to the ion cage.Be EXTRA careful when installing that nothing is shorting. The ceramic washer is critical, as it isolates the filament from ground.

Bad installation

Good installationFilament 2

Filament 1

Ion Cage

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Critical ceramic washers

This side down!

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Tuning Tip:

• Tune both Filaments before leaving for the field.– This can save time and possibly prevent one

from having to vent while in the field. Also, sometimes a filament does not tune as well as one would like, so one may get a better tune with the second filament.

Chopper Frequency Calibration

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First, look the (chop base) TP on a scope (about 200mv scale), for the raw diode signal.

Next turn R5 (circled) until the raw diode signal is a nice peak.

GND

Raw Diode Signal

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Now measure the digital chopper signal at the dig TP.(If you can do this with the second channel of the scope so you can see both waveformsat once, that is best.)

Use the o-scope to measure the frequency of the signal (5v scale).

Turn the Chopper Frequency pot at the front of the EB all the way up.

You can then set the maximum chopper frequency to 250Hz by turning the circled pot.

Next adjust R12 so that the EB display matches the frequency measured by the scope.

Then turn the Chopper Frequency pot (at the front of the EB) down so that the chopper is spinning at approx 130hz.

You chopper frequency should now be calibrated.

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Digital Chopper Signal

Chopper Circuitry Note

• Temperature dependant

– Under large changes in ambient Temperature, recalibration of the Chopper Triggering circuitry may be necessary.

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EB Back Circular Connector

A Blue 1-10V Speed Control - Chopper motor line 4B Black Ground - Chopper line 3 and Servo Gnd (Black)C Orange 12 V - supply voltage Chopper Motor lines 1 and 2D Green IR Raw Reflected Signal - Collector ~200mV at

chopper frequencyE Red Servo power (3.25V)F White Sensor Diode GroundH Brown 5V - Sensor DiodeJ Yellow Servo PWM signalK Purple Ground - Sensor Emitter

Chopper Wiring

Servo Replacement

Detailed instructions can be found at:

http://cires.colorado.edu/jimenez-group/Reference/ChopServoReplacement.pdf

Also this should be in your Ship Folder

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Blocked

Chopped

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Open

Vmode Bleed Through in Wmode

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Lens = 3100V

Lens = 2000V

Interlock Explanation

• Master Interlock– Software Interlock– Polls all pumps– If any pump has an error, shuts down all pumps

• Ionizer Interlock– P5 falls below 90% of full rotational speed– Red LED on TPS, shuts off High Voltages

• Vaporizer Interlock– P4 and/or P6 fall below 90% of full rotational speed– Heater LED and Heater Power LCD on EB shut off– Shuts off power to Vaporizer

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Start/Stop Single PumpFor Diagnostics

If a pump has failed, but it is unclear which pump, start one pump at a time to help determine which pump is broken.

– Push knob, scroll to “Turbo Pumps”, push again

– Scroll to “Start/Stop Single”, push again

– Start with P2, and continue in order until a pump does not start

• The minimum frequency the Pump Controller can read is 100Hz. Therefore, if the frequency never goes above 100Hz, the pump is not spinning and has failed.

• We have noticed that the V81 Turbo Pump failure rate has gotten much better.

Pump Failures

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The ultimate issue is that the NI card has become “hung up”.

Close the DAQ software, turn off the computer, and actually unplug the computer for 10 seconds or so before plugging it back in.

If this doesn’t fix the problem then reseat NI card and try again.

Also ensure that your timing offset in the DAQ Timing tab is 50ns.

My PToF signal is nonexistent even though the chopper wheel is spinning and is moving from blocked to chop to open…

END