Transcript W-7. ProtoDCReviewMarch2007 S Bueltmann

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
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
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 prebowed 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
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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
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
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
Region 1 DC Prototype
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
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
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
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
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
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
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
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