[Sbs_gems] [Revised Logentry] Setting the Ar-CO2 mixing ratio to 70%-30% (with JLab system)

[chandan at jlab.org]

Logentry Text:
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The GEM experts wanted to drop the Ar-CO2 ratio from 79%-21% to 70%-30% (these numbers from the JLab-based binary gas analyzer.
This binary analyzer was calibrated by Jack earlier (https://logbooks.jlab.org/entry/3939313).

So, I went through Jack's calculation - posted in the following link.
https://hallaweb.jlab.org/tech/Detectors/public_html/hall_a/detectors_daq/gas_shed/mixer_for_bb_gems_2021/argon-co2_mixing_ratio_for_gem_detectors.txt

Currently, the voltage setting for the Ar MFC (both for SBS and BB) is 4.44 V.
With the Ar conversion factor (1.443), this voltage corresponds to 4.44*1.443 = 6.41 SLM.
If the requested Ar ratio is 70%, then the total gas flow (assuming we are keeping the same Ar flow as it was earlier) would be 6.41/0.7 = 9.15 SLM.
So, CO2 flow is (9.16-6.41)=2.75 SLM - this corresponds to the set value for the CO2 MFC -  2.75/0.745 (0.745 is the CO2 conversion factor) = 3.69 V.

So, the CO2 flow controllers (for both the SBS and BB sides) are set to 3.69 V.

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/4283620
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