AMS Tips, Tricks & FAQ s

Transcription

1 AMS Tips, Tricks & FAQ s Ed Fortner, Bill Brooks, John Jayne AMS User s Meeting /15/12 Leak Checking Tips 1

2 Normal 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 and difference 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 AB will be about the same as normal, but the closed air signal will have an elevated background. 2

3 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. 3

4 Inlet 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 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 < /6.5 P6 ~ 200 ~ /9.6 *Delta T = Pump Temp Ambient Temp 4

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. Filament 1 Bad installation Ion Cage Filament 2 Good installation 5

6 Critical ceramic washers This side down! 6

7 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 7

8 GND 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. Raw Diode Signal 8

9 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 waveforms at 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. 9

10 Digital Chopper Signal Chopper Circuitry Note Temperature dependant Under large changes in ambient Temperature, recalibration of the Chopper Triggering circuitry may be necessary. 10

11 Chopper Wiring EB Back Circular Connector A Blue 1-10V Speed Control - Chopper motor line 4 B Black Ground - Chopper line 3 and Servo Gnd (Black) C Orange 12 V - supply voltage Chopper Motor lines 1 and 2 D Green IR Raw Reflected Signal - Collector ~200mV at chopper frequency E Red Servo power (3.25V) F White Sensor Diode Ground H Brown 5V - Sensor Diode J Yellow Servo PWM signal K Purple Ground - Sensor Emitter Servo Replacement Detailed instructions can be found at: Also this should be in your Ship Folder 11

12 Blocked Chopped 12

13 Open Vmode Bleed Through in Wmode 13

14 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 14

15 Start/Stop Single Pump For 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 Pump Failures 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. 15

16 My PToF signal is nonexistent even though the chopper wheel is spinning and is moving from blocked to chop to open 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. END 16