clas12 drift chamber prototyping
DESCRIPTION
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 2007TRANSCRIPT
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 ObjectivesDrift 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 ObjectivesDrift 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
Electrical ObjectivesDrift 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 PrototypeExploded 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 PrototypeBasic 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 Christoand Richard Getz
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007
Region 1 DC PrototypeWire 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 PrototypeMechanical 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 wayDC will be assembled in ODU cleanroom
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007
Region 1 DC PrototypeWire stringing of one sector of existing CLAS region 2 DC in ODU cleanroom
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007
Wire feeding apparatus
New All-Plastic Feed-throughPossibility to improve detection efficiency on wire close to feed-through
• Improve detector acceptance at very small scattering anglesStudy 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 PrototypeInitial primary goal to test new all-plastic feed-through design Will be used for in-beam test at Idaho State UniversityMechanical design finished
Design Steve Christo
Stephen Bültmann - ODU JLab 12 GeV Upgrade Drift Chamber Review, March 2007
TimelineRegion 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