GIS-EA - Abridged Procedure

Owned by Collin Tiessen
Last updated: Sept 22, 2023
3 min read

 

0. Foreword

  • For more precise instructions or clarifications of steps, please consult the manual.

1. Getting started when arriving to sleeping machines:

Elemental Analyzer

Do not load samples until end.

Look for next violet warning bar below.

  • Wake EA & wait for temperatures to rise

  • Start new EA list

Make sure there are no samples in the carousel!

  • Reset carousel position to reference run

  • Auto run some RunIns

    • Mass 1mg, Method G_20s

    • After opening a system, could need 10+ of these

GIS Software

  • Open GIS software (Iwtmgs - I want to measure gas samples)

    • Load appropriate .ini file

  • Check indicator lights are on

ACS software

  • Wake up ACS and wait for Cs oven to heat up and equilibrate

  • You can revert to previous gas settings if there are some

  • Make sure you have a magazine with unsputtered gas cathodes loaded

Make sure all sequential positions are filled with gas cathodes with holes pointed down

2. Tuning

GIS Software

  • Switch to tuning tab in GIS and switch V3 to OxII bottle. (Make sure bottle is open)

Never pump on an open gas bottle

  • Pump out the lines

  • Prime with a little OxII and pump again.

  • Load some OxII in the syringe

  • Set to a good starting pressure (between 1000 and 1200 mbar)

GIS Software &ACS software

  • Load a fresh gas cathode and start a single run on ACS

  • Advance the syringe to raise the feeding pressure until onset of carbon is detected. You will likely have to back off if overfeeding.

    • You can tune on the 13C bar as usual but watching the long term behaviour on single run is also helpful.

  • Determine when overfeeding occurs and then lower the pressure back to just before the peak counts pressure setting.

    • Source potential leak currents tend to drop along with the carbon currents when overfeeding occurs.

  • By adjusting both the syringe feeding pressure and the Cs oven temperature, find an optimal setting that stays stable for a long time. This can take a while the first few times. After overfeeding, it takes a bit to recover.

  • Set the pressure setting when you are happy with it.

  • Once happy with the output level (3 uA minimum, but ideally can get as high as 10 uA), run tuning tasks on ACS. Tune:

    • Steerers

    • Box Lens

    • Extractor Potential

    • LE Magnet Pulsing

  • Last two are often the most important.

  • Pump out lines & syringe when done

3. Running Samples

Chameleon

  • If not already done, create targets with the appropriate sample and prep number and save them into the database

Elemental analyzer

  • Input the target data from chameleon into EA

acs software

  • Create and start a gas measurement task

    • Name magazine MICADAS# & Isotope(likely C for carbon) & YYMMDD & “GAS”

      • e.g. 37C220622GAS

    • Set cycle time to 10.0s

    • Once set, ACS waits for GIS to give it commands

GIS Software

  • Go to EA tab of GIS (or similar for Cracker or CHS)

  • Adjust V3 to the EA slot

  • Set the next and last cathode

  • Set the timer to stop the measurement after a set time (often 12 min)

    • It will either run until syringe is empty or the cut off time

  • Set the last EA index - the last slot in EA where you will have a sample

If you add more samples later, you will have to adjust the last EA index to reflect that

  • Pump the GIS lines again and do more RunIns if tuning took a long time.

You may now load your samples

Make sure to put them in the correct position as designated in the EA list.

  • Click Auto on GIS and agree to clean the trap.

    • GIS will acquire info from EA and quantify mass of carbon on the trap

    • GIS will pre-sputter the cathode while combusting the sample.

      • If the current is not below 200 nA after 120 seconds, the measurement will be aborted and you will have to manually manage the trapped sample (This threshold is adjustable in the Settings)

    • If the peak comes up quickly and then falls off after a few minutes, you are probably either overfeeding CO2, underfeeding Cs, or both

4. When you are done measuring and want to shut down

  • GIS software At the end, GIS shuts down and puts position 2 back in but does not tell ACS it is done

  • acs software Finalize the gas measurement in ACS and schedule a sleep task to run after

  • Elemental analyzer In the EA software, run the Sleep task

  • GIS software In GIS, V1 will be on flushing He into the source at a slow enough rate that it’s not a concern

    • But you can close the AMS valve and the He valve

      • Over a weekend or prolonged down time, it is good to turn off the pump as well.