For more precise instructions or clarifications of steps, please consult the manual.
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
Open GIS software (Iwtmgs - I want to measure gas samples)
Load appropriate .ini file
Check indicator lights are on
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 |
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)
&
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
If not already done, create targets with the appropriate sample and prep number and save them into the database
Input the target data from chameleon into EA
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
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
At the end, GIS shuts down and puts position 2 back in but does not tell ACS it is done
Finalize the gas measurement in ACS and schedule a sleep task to run after
In the EA software, run the Sleep task
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.