R3

A description of the Region 3 (RIII) Design for CLAS12

Conceptual Design

The location of Region III on this drift chamber can be viewed as

Region III is assembled with 6 Eqi-shaped pieces. Each of these pieces resembles a Pizza slice which together forms the whole chamber.

A view of the 6 piece assembly can be viewed as

Each of these pieces is made of 3 kinds of plates.

1. Nose Plate (1 No.)

2. End Plate (2 No’s)

3. Face Plate (1 No.)

A Sample assembly of the slice can be Viewed as

End Plate:

There are 2 end plates for each slice which are attached opposite to each other. There are several holes on each end plate through which sets of sense wires are passed connected both the end plates of a particular slice. The whole area in which holes are drilled on each End plate can be further divided into 2 areas; upward wire area and Downward wire area. A sense wire from upward wire area of end plate ‘A’ is drawn to the downward wire area in the opposite end plate ‘B’ and vice versa. Both these wires are angled at 6 degrees to the imaginary midline, which passes through the Nose plate and the Face Plate of each slice. End plate can be Viewed as

Nose Plate:

This is the place which forms the base for each slice. Both the end plates are attached at the opposite ends of the Nose plate. The angled end of the end plates are attached to this nose plate, so that the end plates are projected at an angle in 3-D.

Face plate:

Face plate is the top plate which holds the end plate together on the top side.

Design criteria

The Design Criteria is to develop all the necessary dimensions from the known dimensions.

The known dimensions are

• Distance from target to first sense wire plane along a ray which is normal to the end plate = 4746.5 mm

• Chamber Tilt Angle = 25 Degrees

• Maximum Scattering Angle = 45 Degrees

• Minimum Electron Scattering angle = 5 Degrees

• Distance between the two Adjacent Pieces = 160 mm

The Definition of these given Dimensions can be viewed in the following pictures

Theses known dimensions are used in the determination of the remaining dimensions of the chamber.

Dimensions

End Plate

Dimensions of the End Plate can be Viewed Below

Preliminary Design Phase (9/24/07)

Design

Material and cross section of drift chamber frames, endplates, back plates, and nose plates

Endplate material

1. Polyeurethane Foam
   1. R3 Design specification: General Plastics Mfg. Co., "LAST-A-FOAM", FR-3700
   2. Youngs modulus: 140 MPa
   3. Density 240 kg/[math]m^3[/math]
2. Stanless steel plates
   1. 0.048 inch thick plates on both sides of Foam
   2. Youngs Modulus=
   3. Density =

Backplate Material

1. Hexcell Honeycomb foam HRH 10-1/8 -1.8
   1. 0.004" thick
   2. impregnated wih graphite fabric
   3. HRH-10 is the material name
   4. 1/8 represents the cell size (diameter between opposing flat section)
   5. Density= 1.8 lb/[math]ft^3[/math]
   6. Young's Modulus=

Wire hole patterns and feedthrough details

A Basic View of the Hole on the End Plate with the Feedthrough can be Shown Below

References

1. R3 status page at JLAB
2. CLAS detector NIM article Media:NIM_A449.pdf
3. Mac's CLAS 12 tracking design writeup May 15 , 2005 Media:CLAS12-5-2005.pdf
4. Mac's CLAS 12 tracking design writeup Jan. 1, 2007 Media:CLAS12-1-2007.pdf