CLAS12 Drift Chamber Prototyping

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

• 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 DCs, 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