Re: Revisions to the high-Z impurity correction table

[Claude Petitjean <claude.petitjean@psi.ch>]

Dear Tom,

thanks for reply. Here is a continuation of the discussion from my part:

Looking at    http://kaon.physics.berkeley.edu:8080/run8/1112
I'm still convinced, that the basic impurity levels (and probably ratios)
were hardly much different than what we had in runs 9+10.
Fortunately, the Chemists did a lot of N2 sample measurements during
run 8, so we know quite well that soon after starting the CHUPS
circulation, the N_2 impurity level was and remained at the 10 ppb
level (same as in runs 9+10).

If I understand your numbers right, the observed rate of impurity
capture events in run 8 is by an order of magnitude larger (same
as was observed in runs 9+10).

And even in the beginning of the stable (and clean) run 8 measuring
period, where we had larger impurity rates, I see no reason, why
the  ratio between Nitrogen and Oxygen impurities might not have
been the same (or at least similar) as in the low impurity phase.
(Of course we were not aware of this insight during run 8 due to
the unreliable water vapor measurements.)

This can be assumed, because the impurities, N_2 ans H2O, both
originate from the outgasing walls and tpc materials; and both are
cleaned away by exactly the same method, namely being run through
lq-N_2 cooled active carbon traps which are believed to be 100%
effectiv for both species.
 
Since you can calculate from the N_2 doped run a precise detection
efficiency for N_2 impurity captures, you can determine - using the
chemists sample analysis - the fraction of Nitrogen captures.

Conc. water contents, the chemists analysis was unreliable and
should probably be discarded. Perhaps the analysis of runs 9+10
will yield some cross cecks, since we had there the online monitors
running.

I hope my comments are useful for the finalisation of your corrections..

With best regards

Claude


Tom Banks wrote:

>Dear Claude,
>
>thanks for taking the time to carefully read through the memo.  Concerning
>your question about the impurity composition of the Run8 clean fill: You
>are absolutely correct that the final impurity correction will include a
>mix of nitrogen and (most likely) oxygen contributions; see my August 1
>worklog page
>
>  http://weak0.physics.berkeley.edu/weakint/research/muons/private/tbanks_dir/TeleConf/2006Aug1/2006Aug1.html
>
>for a preliminary treatment of this next stage in the correction
>procedure.  However, the bulk of the Run8 clean fill captures were due to
>nitrogen, from the period when CHUPS was cleaning the pressure vessel.
>See, e.g., the period from 0--200 hours in attachment 2 in
>
>  http://kaon.physics.berkeley.edu:8080/run8/1112
>
>When you say that 90% of the impurities come from humidity, I think you
>are referring to equilibrium conditions *after* CHUPS has cleaned out the
>system as much as possible.  In Run8, such equilibrium conditions were
>achieved for only a portion of the clean fill running period.  When
>Bernhard performed his Run8 correction estimates last May,
>
>  http://weak0.physics.berkeley.edu/weakint/research/muons/private/bernhard/analysis_10May06.pdf
>  http://weak0.physics.berkeley.edu/weakint/research/muons/private/bernhard/highz-analysis-run8-10may06.html
>
>he conservatively assumed that 90% of the Run8 clean fill capture yield
>was due to nitrogen, and that 10% was due to oxygen.  It remains for me to
>corroborate these numbers.
>
>It is worth noting that, as you mentioned, the (delta_r/Y) numbers are
>pretty much the same for all of the relevant high-Z elements.  Of greater
>concern is the detection efficiency for different elements: we can
>calibrate the efficiency for nitrogen, but oxygen is at present an
>unknown.  Since the detection efficiency appears in the denominator of the
>correction formula, it has the potential to dramatically blow up the
>error.
>
>Regards,
>Tom
>
>  
>