1. CLAS12 Drift Chamber Prototyping
Goals and Objectives
Validate Design
Test Assembly Techniques
Find Optimum Operating Conditions
Status of Prototype Chambers
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

2. Design Objectives Drift Chamber Design and Operability
Measure relative gain as a function of high voltage
Electric fields increased compared to CLAS DCs
Validate choice of faster drift gas
Mixture of 92% Ar and 8% CO2 compared to old mixture of 90/10
Measure particle detection efficiency along the wire
In particular close to the attachment point (wire feed-throughs)
Verify low noise related to readout electronics or cathode emission
Test and confirm wire tensions and wire deflections
Check for electrostatic oscillations
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

3. Mechanical Objectives
Drift Chamber Construction and Assembly
Measure deflections of chamber frame under load of wire tension and window bowing
End-plates holding wire feed-throughs to be installed into pre-bowed chamber box frame
Compare to Finite Element Analysis calculations
Validate procedure to survey wire positions and translation to frame of DC
Validate alignment holes and fixtures on chamber framework
Assembly
Chamber frame including tolerances
Chamber strong-back for handling and mounting
Wire feed-through placement
Wire stringing including fixtures and procedures
Circuit board attachment and contact to wires
Gas-tight window design and attachment
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

4. Electrical Objectives
Drift Chamber Readout Electronics
Validate new larger diameter sense wires (20  30 m)
Requires higher voltage between sense and field wires to achieve gas gain of 5 ·104
Measure HV plateau curve and noise levels
Measure leakage currents on readout boards
Validate adequacy for higher voltage requirement resulting in about 10% higher electric fields
Measure signal cross talk
Test new printed circuit board material
Improved high voltage isolation and reduced water absorption by polyimide as compared to FR-4 (presently used)
HV and LV Cable
Frame patch panel on back-plane to route existing cables to boards via smaller diameter on-chamber cables
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

5. Prototype Chambers Full size sector of region 1 drift chamber
Validate design and assembly techniques
Operate DC with varying voltages and gases
Test printed circuit board designs and materials
Small drift chamber to test initially new all-plastic design wire feed-throughs and particle detection efficiency as a function of position along wire (Idaho State University)
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

6. Region 1 DC Prototype Beam Line
Exploded view of box frame and end-plates
Design Steve Christo and Richard Getz
Beam Line
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

7. Region 1 DC Prototype
Basic mechanical and electrical design as for the current CLAS DC’s, but simpler geometry
Use same aluminum end-plate material and thickness (7.9 mm)
Cell size comparable and sense wires slightly thicker
Printed circuit board design using same components
Design Steve Christo
and Richard Getz
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

8. Region 1 DC Prototype Wire feed-throughs as used for CLAS region 1 DC
Metal trumpet insert molded into plastic holder
Crimp pin position defined by plastic holder
Design Steve Christo
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

9. Region 1 DC Prototype Mechanical design well advanced
End-plates being fabricated
Design for frame close to being finished
Design of printed circuit boards for readout and high voltage sides are well advanced
Vendors for fabrication of wire feed-throughs with metal trumpets contacted
Enough feed-throughs on hand for prototype DC
Need to re-qualify manufacturer and process
Design and construction of assembly and stringing fixtures under way
DC will be assembled in ODU cleanroom
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

10. Region 1 DC Prototype
Wire stringing of one sector of existing CLAS region 2 DC in ODU cleanroom
Wire feeding apparatus
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

11. New All-Plastic Feed-through
Possibility to improve detection efficiency on wire close to feed-through
Improve detector acceptance at very small scattering angles
Study electric field along wires close to feed-through
Potentially coat tip of feed-through (partially) with conductor
Design Steve Christo
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

12. Small DC Prototype
Initial primary goal to test new all-plastic feed-through design
Will be used for in-beam test at Idaho State University
Mechanical design finished
Design Steve Christo
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007

13. Timeline Region 1 DC prototype
End-plates ordered (arrive middle of March)
Box frame almost designed (should be available middle of April)
DC mounting and handling fixtures ready middle of April
Assembly and survey last week of April
ODU cleanroom ready on April 1
Begin stringing of wires at ODU middle of May for two months
Printed circuit boards ready by end of June
Gas system and DAQ ready by end of June
Turn on DC in August
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007