Region 1 Drift Chamber

1
Region 1 Drift Chamber

• Overview
• Design
• Status of Prototype Chambers

Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
2
CLAS 12 Cut View

• Region 1 Drift Chamber

2.1 m distance from target to region 1 DC Drift
Chambers designed as six planar sectors
Torus
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
3
R1 DC Design Parameters

• Scattering angle coverage from 5º to 40º
• minimum 50 ?-coverage
• Luminosity 1035 cm-2 sec-1
• 250 µm position accuracy
• Two wire superlayers clocked by 6º
• Six wire planes per superlayer
• 112 sense wires per plane
• Self-supporting chamber

SVT around target
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
4
Parameter Changes in Comparison to CLAS

• Hexagonal drift cell geometry
• Sense wire diameter increase from 20 µm to 30 µm
• Increase drift voltage by about 150 V ( 5
  relative change)
• Change Ar/CO2 gas mixture from 90/10 to 92/8
• Result
• Same gas gain of 5 104
• Increased drift velocity
• More linear drift velocity
• linear drift time - distance relation
• Short time window of 150 nsec

Design Steve Christo
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
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
CLAS 12 GeV Upgrade Workshop, May
2007
6
Region 1 DC Prototype

• Exploded view of box frame and end-plates
• End-plates will be pre-bowed in frame by shims
• After pre-tensioning end-plates will be flat (as
  under wire and gravitational load)

Design Steve Christo and Richard Getz
Beam Line
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
7
Region 1 DC Prototype
Maximum deflection 1.83 mm
Finite Element Analysis of plate deflection by
Katherine Wilson and Dave Kashy
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
8
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 slightly smaller and sense wires
  slightly thicker
• Printed circuit board design using same
  components
• Wire lengths from 9 cm to 200 cm

Design Steve Christo and Richard Getz
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
9
Region 1 DC Prototype

• Panel interface between new small cables from STB
  boards and exisiting cables to readout racks

Design Steve Christo and Richard Getz
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
10
Region 1 DC Prototype
Conductive Rubber Tube
Circuit Board
Crimp Pin
Feedthrough
Endplate
Design Steve Christo
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
11
Region 1 DC Prototype

• Wire feed-throughs as used for CLAS region 1 DC
• Metal trumpet insert molded into plastic holder
• Wire position defined by trumpet flare and not by
  crimp pin position

Design Steve Christo
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
12
Region 1 DC Prototype

• Mechanical design well advanced
• End-plates machined and surveyed
• Stainless steel frame being fabricated at JLab
• Design of printed circuit boards for readout and
  high voltage sides are mostly finished and one
  readout board available
• 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
• Mechanical assembly of DC frame and end-plates
  plus survey at JLab
• Available for stringing by middle of July
• DC wires will be strung in ODU cleanroom

Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
13
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
CLAS 12 GeV Upgrade Workshop, May
2007
14
Small DC Prototype

• Initial primary goal to test new all-plastic
  feed-through design
• Mechanical assembly finished and wire stringing
  started at ODU
• Circuit boards manufactured

Design Steve Christo
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
15
Electronics

• Signal translator board designed
• U-plane (superlayer) built and V-plane designed
• High voltage board designed
• Design of cable breakout/adaptor box started
• New smaller cable between pre-amp and breakout
  box being ordered
• Circuit boards for baby-chamber available and
  tested

Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
16
Signal Translator Board
Design Chris Cuevas, Bill Gunning, and Mark Taylor
Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007
17
Timeline

• Region 1 DC prototype
• DC frame with end plates built and aligned by
  early July
• DC mounting and handling fixtures ready end of
  June
• ODU cleanroom ready in July
• Begin stringing of wires at ODU beginning of
  August for two months
• Printed circuit boards ready by end of June
• Gas system and DAQ ready by end of June
• Turn on DC in October/November
• Note Incurred about two month delay of schedule
  presented in the beginning of March (about two
  month ago)

Stephen Bültmann - ODU
CLAS 12 GeV Upgrade Workshop, May
2007