Minutes of DRAGON meeting, 10 August 2004

Present: AR, CR, DH, JC, KO, MA, CV, JP, DG, LB, DFOT, AO, GR, MT, PM, AH

1.  Corrections to Previous Minutes:

Court-style recording technique was found acceptable

2.  BGO Measurements

DG - Y88 and Cs137 sources used with BGO array closed and measurements taken.  Fitting 
to be finished for next week and data to be presented.  Note that the tray at the bottom 
of the target is still in place.

3.  DAQ report

JP - Things are being accomplished (more things than recorder was able to write down).
By the end of the week we should have the same electronics but split into 2 crates.
There is still lots to do.  Would like the DAQ group to rewrite front end but probably
won't happen.  "Point of no return" fast approaching, when modules start to get relocated.
Pictures are being taken.

4.  Power Supplies

DH - As of this afternoon 4 power supplies will be locked out as they are being switched
over.

5.  YSLITM-Bot

Peter is still working on this one.

6.  PGAC

JC - Signals have been seen and no modifications have been made yet.  Appears to still 
be working as reported earlier.  Would like to add two 25 micron wire planes to double 
signal but unsure how this will affect the timing.  Current rise time about 10 ns, 
although it's claimed that one can have 1-2 ns for rise-time.

DH - Any missing pieces?

JC - We think not.

DH - Ready to put in gas ion chamber envelope?

JC - Would first like to add extra wire planes (should add 1/4 inch) then trying fitting it
in there.  Note that all planes are wires and not foils.  Get 16% beam loss, up from 11%, 
if one adds the two extra 25 micron wire planes.  Maybe replace the 50 micron position
resolution wires with 25 micron wires to minimize beam "blockage".  Two additional planes 
would be cathode planes.

CR - How small are signals?

JC - They are small and really ugly.

CR - What is the source of the noise?

JC - This is undetermined as of yet.  We're using Americium alphas.  Might get a better
idea of rise time resolution if we use fission fragments.  Still lots of stuff to test and try.

AO - The rate at the back is low, so leading edge of signal should be only concern.  
Why worry about tail in data?

JC - Tail has unknown effect on leading edge.  We would like to understand it.

AO - One might expect low pressure alphas to give lots of jitter.  Highly ionizing
particles would be a better test.  TWIST time expansion chamber also had trouble with 50
micron wires.  Townsend coefficients not fully understood.  Perhaps this is similar problem.

JC - Are the expectations of the PGAC correct?  Papers say one can achieve 1mm position
resolution and 300 ps timing resolution, although not at the same time.

CR - Sure nothing is missing?  Like missing wires?

JC - Haven't looked inside yet but outer position resolution wires look fine

7.  MA has some trouble with GEANT

MA - Events are getting lost after MD1.

Many suggestions follow, some of which Mike has already had a look at.

8.  MT has data from Cybele's and Uwe's runs (see attached file)

MT - Some work still has to be done before high confidence in fit but this what has been
done up until now.  Omega-gamma has dropped a little and E-res has gone up.  Is a troubling 
point that is not shown on this graph and really doesn't agree with the new data.  Used a 
double arctan function to fit the data, where the data is based purely on singles.

9.  Next week

Dave - Interlock Logic
Dario and Andres - BGO report
Mike - Will show us something...

11:14 meeting concludes