Re: Systematics of humidity captures

[Bernhard Lauss <lauss@berkeley.edu>]

Please find my first draft answer at

http://weak0.physics.berkeley.edu/weakint/research/muons/private/bernhard/humidityrun9.html


		have a nice day

			Bernhard




*******************************************************************
Bernhard Lauss                 E-Mail: lauss@socrates.berkeley.edu
Physics Department
366 LeConte Hall
University of California @ Berkeley
Berkeley, CA 94720                             Tel: (510)-642 4057
United States                                  Fax: (510)-642 9811
*******************************************************************

On Mon, 6 Feb 2006, Bernhard Lauss wrote:

>
>
> Dear Claude,
>
> I am just this time working on the requested
> impurity note for run9,  which
> exactly deals with this problem, too.
>
> Your numbers are correct but .....
>
> I think the factor of 2 comes finally tracked down from
> the question what is the PURA humidity sensor measuring.
>
> It is measuring the dew point, which we then
> translate into relative humidity of
> water molecules with respect to hydrogen molecules
> by some tables (from our PNPI colleques, or less
> exact in the "Handbook of chemistry ofr physics"),
> if my understanding is correct.
>
> Now all our and your caculations about the transfer rate
> are taking into account atomic concentrations.
> Therfore we have to recalculate the
> measured humidity from the PURA device
> with an extra factor of 2 due to
> molecular versus atomic concentration
> and then the reading is
> 35/2 ppb humidity,
> which is a factor of 2 off from your correct calculation.
>
>
>  I'll send you my suggestions for the solution to this
> factor 2 as son as I have written it up nicely, today or tomorrow.
>
>
>
> 		best regards
>
> 			Bernhard
>
>
>
>
>
> *******************************************************************
> Bernhard Lauss                 E-Mail: lauss@socrates.berkeley.edu
> Physics Department
> 366 LeConte Hall
> University of California @ Berkeley
> Berkeley, CA 94720                             Tel: (510)-642 4057
> United States                                  Fax: (510)-642 9811
> *******************************************************************
>
> On Mon, 6 Feb 2006, Claude Petitjean wrote:
>
> > Dear friends,
> >
> > I reevalulated the systematics of muon captures on
> > water (in fact, oxygen) in our tpc as follows:
> >
> > Our humidity sensors measured 35 ppb in eqilibrium
> > state (c_O = 3.5 10^-8). The normalized density
> > in 10 bar protium is phi = 0.0116 and the reduced
> > transfer rate to O is lambda_Tr_O = 0.85 10^11/s
> > (Schellenberg et al.).
> >
> > The effective muon transfer rate to Oxygen is then:
> > lambda_tr_O * phi * c_O =
> > 0.85 10^11/s * 0.0116 * 3.5 10^-8  = 34.5/s
> >
> > and the transfer probability per muon ~34.5/l_mu
> > = 34.5 / 455700 = 7.6 10^-5
> >
> > The muon capture rate in Oxygen is l_c_O = 97400/s
> > (Eckhause), the probability l_c_O/(l_c_O + l_o) =
> > = 0.176.
> >
> > We expect thus in 35 ppb H2O 0.176 * 7.6 10^-5 =
> > = 1.34 10^-05 Oxygen captures per muon.
> >
> > In reality we saw (background deducted)
> > ~ 1.1 10^-05. Thus if we assume an overall
> > detection efficiency epsilon_O = 0.82 for
> > observing in the tpc the mu-O captures, then our
> > impurity measurements agree exactly with the
> > theoretical expectation from the humidity measurement!
> >
> > Question to Peter, Francoise and other experts:
> >
> > - Do you see anything wrong with my numbers?
> >
> > - Where is the factor 2 of too many impurity captures
> >    which was repeatedly claimed during the last run?
> >
> > - Is my conclusion correct, that the impurity events
> >    of our last 2 runs were clearly dominated by the
> >    humidity?
> >
> > Lets discuss this on tomorrows teleconf.
> >
> > With best regards
> >
> > Claude
> >
> >
>