1. Drift Chambers for CLAS12 -Mac Mestayer
Specifications:
physics a tracking specs. a design concepts a design
Design concepts:
‘regions’ a superlayers a layers a cells
‘umbrella’ design: minimize Dfdead
planar layout, triangular boxes: accuracy
Simulations, Prototyping Issues
Planned improvements and conclusion
March 7, CLAS12 Drift Chamber Review Mac Mestayer

2. Tracking: physics a design spec’s
electron beam
shift in Dq ~ 1 mrad a 2.5% shift in cross-sections
small cross-sections
L = 1035 /cm2/sec
measure hadronic state (esp. excl. reactions)
reject extra particles (missing mass)
|dp| ~ 50 MeV/c, sinqdf p & dq p ~ 20 MeV/c
other cuts: co-planarity, etc. a ~5 mrad
forward-going particles
5o minimum lab angle
broad coverage in center-of-mass
minimize dead area
March 7, CLAS12 Drift Chamber Review Mac Mestayer

3. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer
Design Specification
Goals:
Specifications:
measure cross-section accurately
q ~ 1 mrad
dp/p < 1%
select an exclusive reaction; e.g. only one missing pion
dp < .05 GeV/c
dq p < .02 GeV/c
sinq df p < .02 GeV/c
small
cross-sections
L = 1035/cm2/s
high efficiency
good acceptance
Df ~ 50% at 5o
March 7, CLAS12 Drift Chamber Review Mac Mestayer

4. Summary : spec’s a design concepts
Specifications:
Fwd.Design Features:
L = 1035/cm2/s
- high efficiency with large backgrounds
small cells
six 6-layer superlayers
30 mm wires
good dp/p, dq, df
planar chambers
identical cells (easy to calibrate)
~linear drift velocity
+/- 6o stereo angle
good acceptance
flanged frame
low wire tensions
Df ~ 50% of 2p at 5o
reliability
self-supporting design
March 7, CLAS12 Drift Chamber Review Mac Mestayer

5. March 7, 2007 CLAS12 Drift Chamber Review Mac Mestayer
Physics goal Physics spec Design spec.
measure cross-section accurately
q ~ 1 mrad
dp/p < 1%
planar chambers
identical cells (easy to calibrate)
250 mm accuracy/layer
select an exclusive reaction; e.g. only one missing pion
dp < .05 GeV/c
dq p < .02 GeV/c
sinq df p < .02 GeV/c
~linear drift velocity
+/- 6o stereo angle
small
cross-sections
L = 1035/cm2/s
high efficiency
small cells
six 6-layer superlayers
30 mm wires
good acceptance
Df ~ 50% of 2p at 5o
pre-bowed frames
low wire tensions
self-supporting design
March 7, CLAS12 Drift Chamber Review Mac Mestayer

6. Drift Chamber Design Decisions
6x6 layers
robust track-finding
+/- 6o stereo
better f resolution than CLAS
planar; self-supporting
identical cells, easy to calibrate, survey, repair
112 wires/layer
enough for 1035 operation
30 mm sense wire
92/08 Ar:CO2
faster, linear distance-vs-time, strong, more reliable stringing
low wire tension
thinner endplates
on-chamber amplifiers
good signal/noise
re-use hv, lv, ADB, TDC
lots of spares; cost savings; better segmentation
March 7, CLAS12 Drift Chamber Review Mac Mestayer