Re: NuSAG Q #9

From: Hans Jostlein (
Date: Thu Jun 23 2005 - 16:23:29 CDT

Thanks, Steven and Josh, for tackling Q9.

I do want to state, for the record, that I hold a very different view for what Steve expresses below (if I understand him right).

I do wholeheartedly agree with what Josh says:
"Cross-calibration of the detectors by moving them is intended as a
bottom-line test of Braidwood's entire data acquisition, calibration, and analysis chain."

This is not to diminish the importance of all the steps we expect to implement for the blow-by-blow calibration,
--PMT gains
--oil levels
--response to neutron source
--energy deposit by straight cosmic muons
--Boron acceptance
--chemical analyses
--event based tests such as event distribution, energy spectra,etc etc

The strength of the Braidwood experiment is, indeed, in the multiple ways of cross checking.
The gist of my comment is just that the side-by-side calibration measures the (acceptance*efficiency) integral very precisely,
with little requirement for analysis and interpretation, and we should be proud of being able to do that.



----- Original Message -----
From: "Steven Biller" <>
To: "Josh R Klein" <>
Cc: <>; <>; <>; <>; "Nick Jelley" <>; <>
Sent: Wednesday, June 22, 2005 4:12 PM
Subject: RE: NuSAG Q #9

  No, only my brain is deuterated (SNO will do that to you)!

  - Steve

   Thanks---this sounds good. I presume you mean 12B, not 8B, though of course
if we used deuterated scintillator, maybe...

On Wed, Jun 22, 2005 at 10:25:38AM +0100, Steve Biller wrote:
> Hi Josh,
> I think this looks good and puts things in the proper context
> regarding how we use the near-site measurements. My own view is
> that the phrase, "Cross-calibration of detectors" (which we always use)
> is misleading and sends people off in the wrong direction. It's
> more accurate to say, "Cross-check of calibration systems," which
> is exactly what you go on to describe. In talks, I always make it
> a point to state that this is NOT, in itself, a calibration of
> the detectors - but it is an important, high-level check that our
> calibration systems work.
> Another thing is that you might also want to mention 8B
> as another way we will check things in the 2 near,2 far configuration.
> I'd suggest adding something like this at the end of the 1st
> paragraph in that section:
> "We will also check our relative efficiencies to an accuracy of ~0.5%
> using beta-decays from 8B, which will be produced via muon spallation
> throughout the volume of each detector with essentially identical
> rates at near and far sites."
> Finally, I worry just a bit about saying that the last move is
> the "most critical," as this might suggest we will not be able to
> demonstrate things sufficiently until the end of the experiment
> and will be hanging everything on that last step. I would favour
> replacing the first sentence of the last section with something
> more like:
> "As a final check, towards the end of the experiment we will replace
> one of the near detectors with one from the far site. After movement..."
> - Steve
> Josh R Klein wrote:
> >Hi,
> >I've attached a very preliminary draft response to the NuSAG question $9,
> >dealing
> >with calibrations and the movement of the detectors. Please send comments,
> >thoughts, suggestions, etc. It isn't very quantitative, but we may be
> >able to use
> >some of the simulation results to beef it up. The bottom line is that we
> >don't have
> >to worry about things being constant, since we will measure and re-measure
> >everything anyway. The one place this might not be true is for the volume
> >and the
> >distribution of the Gd---we need to think about that a little bit.
> >
> > Thanks,
> > Josh
> >
> >
> >------------------------------------------------------------------------
> >
> >\section{What must remain constant?}
> >
> > Cross-calibration of the detectors by moving them is intended as a
> >bottom-line test of Braidwood's entire data acquisition, calibration, and
> >analysis
> >chain. The requirements for constancy of detector parameters is minimal,
> >however,
> >because nearly all the parameters will be re-measured before and after any
> >move.
> >The most important part of the detector which must remain the same is
> >therefore the
> >calibration system itself, in particular its geometry and its positioning
> >accuracy,
> >as these can affect the calibration we will do at each position. Even
> >here,
> >however, we will be able to check for changes in the system, for example by
> >comparing the expected point at which a source just touches the inner
> >vessel to the
> >point when it actually does. We are not concerned with changes in the
> >calibration
> >sources themselves, as these can be moved from one detector to another at
> >any time.
> >We outline below the calibration plans for the various configurations.
> >
> >
> >\subsection{Two Modules Near Site (Initial Running)}
> >
> > We will use the initial configuration, in which two modules are both
> >installed in the near site, to shakedown and commission the detectors as
> >well
> >as to understand the relationship between the detector parameters
> >(attenuation and
> >scattering lengths, PMT gains, electronics channel efficiencies, neutron
> >capture
> >efficiencies, etc.) and the overall detection efficiency. During this
> >time, we will
> >use both the embedded optical sources (LEDs on the outer sphere) as well
> >as the
> >calibration system itself to deploy $\gamma$, electron, neutron, and
> >optical sources
> >throughout the volumes (the same radioactive sources can be deployed in
> >both
> >detectors). The goal of these source deployments is to build a complete
> >detector
> >model which will allow us to predict the relative detector efficiencies to
> >much
> >better than 1\%, and to verify that our model also correctly predicts the
> >dependence
> >of the relative efficiency on any parameters which might change during the
> >move to
> >the far location. At the end of this initial period we will understand
> >the sources
> >of difference (if any) in the response of the two detectors, and the
> >bottom-line
> >test of this will be in comparing the antineutrino fluxes measured by each
> >detector.
> >
> >
> >\subsection{Two Modules Near, Two Far}
> >
> > In the second configuration, in which one of the near detectors has
> > been
> >moved to the far location and an additional module added to both the near
> >and far
> >locations, we will begin by re-calibrating the moved detector and
> >comparing its
> >parameters to those we measured at the near location. These calibrations
> >will
> >include measurements of the optical parameters (embedded LEDs and diffuse
> >deployed source), PMT gains and channel efficiencies (LED's and deployed
> >source), neutron capture efficiency (AmBe source), the overall energy
> >scale of
> >the detector (AmBe and elecron source), and the volume of the scintillator
> >(direct measurement). With these parameters we will then update our
> >detector
> >model and predict what the relative response and efficiency of the
> >detector is
> >after the move. We will test our prediction by moving one or more
> >radioactive
> >sources between the near and far detectors.
> >
> > During this stage, we will also perform the same comparison between
> >the two modules at each location as we did in the initial configuration.
> >Again, we will be measuring the detector parameters upon which our model
> >depends, and comparing the prediction to radioactive source runs in each
> >detector. The final comparison will be the measurements of the neutrino
> >fluxes between each of the modules at the same location---they should
> >agree to
> >well within the systematic uncertainties derived from the calibration.
> >
> >\subsection{Swapping of Two Modules}
> >
> > The final and most critical move will be the last. After movement
> > and
> >recalibration, we should be able to predict precisely what we expect the
> >moved
> >detectors to measure relative to the ones which have remained stationary.
> >
> >

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