Region 3 Statuts Report

Lesson learned: when I edit my webpage at JLab and send it via FTP to my webserver:
                            dilbert.physics.wm.edu hosting Qweak and Pol3He websites will be
                            banned by JLab IT automatically ...


1) MAD test board

Undergraduate student Graham and I are designing a simple test board for the MAD chips. Primary idea is to have a quality test of the 600 MAD chips  before
they will be soldered on the front end boards. The test board will only allow basics functional tests like checking the discriminatiom and dis/enabling individual channels 
for rejecting broken MAD chips. For this test board we will use a ZIF test socket (ZIF: Zero Insert Force). This test socket allows a quick exchange of MAD chips without damaging the pins.
Unfortunately any test socket will add a lot of capacity to the sensitive MAD inputs which would spoil more sophisticated measurements like channel sensitivity and threshold behaviour.
We intend to study this with a few MAD chips which are directly soldered on a test board.
The test board design is based on a INFN thesis where the MAD chip properties have been measured. This thesis contains some blurred test board schematics pictures where INFN
could not provide us with the original schematics ... so Graham, INFN, and I needed some time to figure out the details ("reverse engineering").

2) Foil Stretcher

Just started to design a foil stretcher which we have to build soon. The foil will be clamped with PVC pipes into aluminum c-channels. The stretching of the foil is done by retracting the c-channels
to an outer position. Similar design was done at UVA (BigBite) and JLab (Hall A VDC).

   


3) Geant4 Simulation

- can now read in and process the primary event root file created by the event generator written by Michael

- still in progress: photon contribution to VDC electron tracks: ~20-25% . Thanks to Juliette for pointing out to me
  how to calcule the rate (wrong normalization in previous report)
 
-  written but not implemented in the event generator:

      a) Energy loss due to ionization (Bethe-Bloch) in the target
           Online CVS: http://dogbert.physics.wm.edu/cgi-bin/viewcvs/viewcvs.cgi/Qweak/Root/Macros/EnergyLoss/

             - takes into account the energy loss distribution (Landau) before the vertex (target,walls)
                target:  max ~11MeV.

      b) Internal Bremsstrahlung correction

           Online CVS: http://dogbert.physics.wm.edu/cgi-bin/viewcvs/viewcvs.cgi/Qweak/Root/Macros/IBCorrection/

                     Geant3: I could only this , added by Richard Jones

                        unif=RANDOM()
                        chi=log(Q__2/MELEC**2)-1
                        E_ENERGY=E_ENERGY*(1-exp(-unif*PI_/(2*alphaQED*chi)))

                      C     To obtain consistent kinematics, we treat the internal bremsstrahlung
                      C     photon as if it were colinear with the outgoing electron, and just
                      C     attenuate the energy of the scattered electron.  This leaves the
                      C     q2 of the vertex unchanged, and it corresponds to the peaking
                      C     approximation in the case of forward scattering, but away from the
                      C     forward direction it ignores small momentum components transverse
                      C     to the outgoing electron direction.  At some point this should be
                      C     checked because it affects the experimental q2 acceptance.
                      C     August 30, 2004: richard.t.jones@uconn.edu

          Internal Bremsstrahlungs correction in the Geant4/Root event generator is mainly based on the paper
          Phys. Rev. C, Vol 62, 025501: "QED radiative correction to virtual Compton scattering", M. Vanderhaegen et al.

          The article give a good recipe for applying/MC internal bremsstrahlung for elastic electron-proton scattering.
          Energy loss due to IB can happen before or after the scattering vertex in the framework of the peaking approximation
          (IB photon is emitted along the incoming/outgoing electron)
          This approach is also used in MCEEP by Paul Ulmer based on older papers.
          
4) Flatness Scanner

In VDC simulation and tracking we assume that the wires are perfectly alligned in the wire plane. In reality the wires will be string over a small bridge which is part
of the VDC wire frame. This bridge defines the vertical position of the wires  but is subject to surface waviness introduced by cutting and milling the large frames.

After talking to several companies about how to have a cheap but accurate measurement of the frame flatness as a part of a quality control we ended up with 2 companies
(Sensor Instruments and Schaefter+Kirchhoff). Both companies are selling an analog/digital light barriers for detecting the size, location or edge of an object within a collimated
laser beam.

For ATLAS drift tubes their position (height) was measured over a length of ~2m with a precision of sigma ~2.3um using a system of Sensor Instruments.
We require a precision of ~25um in a vertical wire offset (== wire diameter => delta_t = 0.5ns in arrival time ~= TDC resolution) .

 of <20um

             System from Sensor Instruments                                                                             System from Schaefter + Kirchhoff



5) Wire properties

Graduate student and I are designing a simple device which allows to determine the max. weight for stringing the wire.
The idea is to measure the elongation  of a ~1m long wire (~3-4mm) for different masses and figure out above which mass
the elongation becomes non-linear.

We expect to use a weight of 50-70g for stringing 25um wires.