Progress Report
Geant4 simulation update
- code consists of 116 files and ~11k lines ( comments are not
taken into account), see http://dilbert.physics.wm.edu/elog/Software/122
for details.
- current stable version: v50
(since last weekend)
- includes: target,
collimators, minitorus coils and field, main magnet coils and
field, dual VDCs, handle bar detector
- the drift cells geometry is parameterized (height,
width, length, and angle) and is defined by an input file
- the location and tilt angle of the VDCs and
Cerenkov detector are defined by an input file.
- different approaches to define the magetic
field as local fields bound to the location of the coils have
failed, the field of the mini torus was always ignored by Geant4.
Took a while to figure this out
since the field effects of the mini torus are small.Working solution is
a global magnetic field manager, which simply summes up the
two fields.
- Besides my misunderstanding of the non cross
section weighted Q2 entry in the PAW ntuple I found a bug in my Q2
extraction
( q2 instead of q2[0],
see http://dilbert.physics.wm.edu/elog/Software/116)
- for a correct cross section weighting the weight factcor (weight_n)
is now included in Geant4
- I was plagued by segementation faults for the last weeks when I
tried to run with the full geometry for more than ~3500 events. Even
used a two day evaluation
license of a professional debugger (insure++
, $8000 license) but without success. After the code was clean up (e.g.
header files, pointer initialization) and Root
was downgraded from developer to production
version it does not crash anymore. However there is still a
memory leakage problem when I disable cerenkov light production
in the simulation.
-
with the current Qweak setup beeing implemented in Geant4 I took a look
on the hit distribubtion of VDC (http://dilbert.physics.wm.edu/elog/Software/124).
A coarse estimation of the active area is 78"x18" with a
very generous safety margin. I have to test if the VDC frame can be hit
by ajacent octants which gives me an upper
limit of the overall length.
- Just finished: wire spacing:
simulations were done with different wire distance between
25/64" and 32/64" with a stepping size of 1/64".
Sorry , have not made a multigraph plot yet (http://dilbert.physics.wm.edu/elog/Software/119).
The hit distribution is fine for a cell width smaller than 29/64". For
a higher
wire spacing you get unwanted 3 cell hits . . .
- pending simualtion
issuses:
- including a real main magnet
environment, e.g. coil support plate sticking into the octant (http://dilbert.physics.wm.edu/elog/Software/125)
- including the shielding wall ,
therefore we need the the location and size of the cutouts
- including the beamline and
"precollimator"
- an
independent (in)elastic event generator
Drawings
After the extraction of the active area I have started to
produce engineering drawings of the wire chamber frames with
SolidWorks. We have drawings of various drift chambers (Hall A VDC,
HKS, SOS, Region 2 (Norm), and MAMI) and I'm using them as
templates for my drawings. So far I have done drawings of the alu
baseplate and the HV frame.
They are not final but good enough for an engineering review at JLab (http://dilbert.physics.wm.edu/elog/Construction/78).
The drawings are "dynamic and parameterized", means that if I have to
change the dimensions of the chambers, the position of the
grooves and holes will change accordingly (e.g. the groove has a 2in
distance to the outer frame size, 29 holes in the horizontal direction
with relative positions).
At present I'm working on the gas flow channels and the alignment of
the O-rings needed for stacking the frames without interference (http://dilbert.physics.wm.edu/elog/Construction/79)
I expect to have a full drawing package ready for the next quarter
since the bulk part of the Geant4 package is mostly completed for my
purpose.
Clean Room
Will be hooked up mid/end of April according to the facility management
...
That's all folks