1. CLAS12 Forward Tracking: Status and Challenges
Region 1- Idaho State stringers are doing final wires on the 3rd and 4th chambers. Have a full stringing crew in place
Region 2- Old Dominion is almost finished stringing the 6th (final) Region 2 chamber. They have fully tested all previous chambers at high voltage; found very few problems and fixed all of them.
Region 3- First two Region 3 chambers are done with stringing, and have gas bags in place. High-voltage testing is underway. (see photo)
Installation Plans- Rack locations for high-voltage, low-voltage and signal readout will all be on the floor to both sides of the torus. Plans are being made to begin cable and connector labeling and refurbishment; delayed somewhat by recent flood.
Overall: Most sub-tasks have been completed; stringing is about 60% complete (see project summary plot)
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

2. ‘Region 3’ Work at Jlab & Project Status
CLAS12 Drift Chamber Construction Status
Region 3 Chambers at Jlab
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

3. DC12 Challenges and Mitigation Strategy
Refurbishing old equipment:
we plan to re-use HV cables and distribution boxes but some pins are damaged and difficult to buy
we plan to re-use post-amplifier/discriminator boards and crates and LeCroy FASTBUS TDC’s (difficult to maintain)
evaluate equipment; investigate alternative solutions (started); we have many spares
On-chamber instrumentation:
HV boards must be mounted on chamber; cables soldered on with full length rolled up
design, prototype, test, re-design (we have an experienced crew)
Achieving 250 micron resolution:
survey to 100 microns relative to toroidal geometry
know B-field to <1% relative to toroidal geometry
account for distortions: wire sags and endplate bowing of ~1mm size
 we have a very reproducible link-mounting scheme; survey points will be included in the cryostat design; conceptual plans for B-field mapping started; we have experience doing alignment using real data
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

4. A new DC board with tracking trigger ?
based on capabilities of a new “drift chamber readout board”: amplifier, discriminator, TDC
FPGA architecture allows “segment-finding”
fully-pipelined readout of data and trigger logic
 trigger can associate a charged track with a hit in a scintillator-based detector
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

5. CLAS12 Forward Tracking: Status and Challenges
How does it work?
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

6. CLAS12 Forward Tracking: Status and Challenges
Underlying logic?
Move triangular template across superlayer; occupancy of 2 or greater is a ‘half-cluster’, aligned ‘half-clusters’  ‘cluster’
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

7. Operating Cost Savings
Units Saved / Year
Cost / Unit
Yearly Savings
Data Storage Tapes
3000 Tbytes * .75
35$ / Tbyte
80 k$
Maintenance Manpower
100 FTE days
45$/day
4 k$
Power Savings
60,000 kW-hrs
0.10$/kW-hr
6 k$
Offline cpu Cycles
10^8 cpu-secs ?
Total Cost Savings
~ 100 k$
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

8. CLAS12 Forward Tracking: Status and Challenges
DCRB Cost and Schedule Table 1
Project Cost
Description
Quantity
Price
Labor
Notes
Ext Price
Turnkey Production
252
$1600
2 weeks
Procurement
$405K
Delivery ARO
8 wks. delivery
Acceptance Testing
3 weeks
Specify/Purchase 9U x 160mm VXS crate 18
$10K
1 weeks
$180K
Crate acceptance
Power test
Full crate DCB test verification
Full function test
Installation & commissioning
4 weeks
Hall installation/test
Totals
15 weeks
$585K
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

9. Magnetic Field Measurement
Small manufacturing defects can lead to measurable changes in tracking
what is the effect of a 2mm radial shift in one coil?
on a small-angle, high-momentum electron
in the bore (convenient place to measure B)
7o, 10 GeV/c electron
B ~ 2 T
r = 42 cm
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

10. Magnetic Field Measurement
2mm coil shift  0.7 % change in B at 42 cm radius
2mm coil shift  40 Gauss dipole field on axis
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

11. CLAS12 Forward Tracking: Status and Challenges
Summary
The CLAS12 drift chamber project proceeds well; still plenty to do: instrumentation, installation, commissioning and calibration.
An alternative DC readout board with FPGA technology enables flexible charged-track triggering, reduces tape usage and offline computing, and saves money.
Small distortions in torus manufacture can cause significant tracking distortions; schemes to measure magnetic field must be developed.
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges

12. Forward Tracker: Dependence of Momentum Resolution on DC Resolution
Backup slide:
Multiple scattering
dominates
fractional
momentum
resolution vs.
Effect of changing resolution 250 350 microns
Oct. 10, 2012
CLAS12 Forward Tracking: Status and Challenges