kyle.ryan@LIGO.ORG - posted 16:43, Thursday 16 October 2014 - last comment - 09:41, Friday 17 October 2014(14489)
Ran aux. pump cart by BSC6 at Y-end between ~1100 - 1500 hrs. local -> Valved-in RGA to Y-end (briefly)
Took faraday analog scan of the Y-end at the request of others -> Data is useless (as expected) as the unbaked RGA (background) dominates the entire spectra. Note that the RGA is pumped only by the Y-end volume (i.e. the local pump cart is valved-out while the RGA is valved-in to the Y-end). A valid RGA scan was not attempted here as the setup time isn't justified (at this time).
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Thanks Kyle.
AMU 20 and 22 (neon isotopes) certainly do not appear to be significant but as Kyle notes the RGA is too wet to say much else. After other priorities are dealt with the RGA will be baked. It is unknown when we can get around to this.
If neon were present we should expect to see both 20 and 22 at the ratio of the isotopes ( 90/9 ).
The amu 20 that we normally see in our systems is most likely doubly ionized argon(40). We have argon (and other air components) because of the large quantity of viton in our system which acts as an air reservoir. In addition the ion pumps do not pump argon or other noble gases very well.
I do not think there is much neon in the spectrum. The 20 peak looks like doubly ionized argon and there is not much at 22. The pressure of neon is less than 10^-10 torr, so if there is a leak it is less than 10^-7 torr liters/sec. Much too small to account for the reduction in overall pressure measurement in the pods. RW
Lowering the Electron Energy to 50eV should lower the rate of doubly ionized Argon without significantly decreasing the sensitivity to Neon. This is the setting we used in the Pod leak check, thanks to Rai's calculations.