1

Coordinate Detector: prototype design

• The Coordinate Detector (CDET):

Three independent vertical planes with 15 cm plastic shield in front, all planes as close as possible

One detector plane consists of four sections each covering 96x116 cm2

The active element of each section is a stack of 0.5x3 cm2 scintillator bars, split in half, viewing the target

WLS fibers run through holes in the bars and transmit light to H8711-10 16-channel PMT

• The prototype reported here, will represent mechanically one section of the CDET:

Instead of using 5 mm thick scintillators we will use plastic bars cut from 3/16” acrylic sheet; no holes in the bars

The fibers will run from the end of the bars to the cookies

No light sealing

2

CDET prototype design• Prototype with the cover removed

• Front plate: ¼” aluminum

• Six vertical stacks (each 32 bars), split in half

• Each stack is strapped to the front plate at different positions to make transition between the sections

• The straps run through holes in the front plate

• 1/2” smooth polyester straps, 0.5 mm thick, with seals

• niches in the stacks for straps

3

Connection between detector sections

• End of the front plate of one section inserted into the other section

• Cover on the back attached to the two cross-bars

• Light tightness using black tape and sealant between sections (front and back plates), on the cover edges and in the openings for the straps

• End plugs on the top and bottom sections (not in the present design)

• Scintillators removed from the left half to see the openings for the straps

•Fibers not shown

• All dimensions in mm

4

Fibers to PMT connections

• Cross-bar (1/2” Al) attached to front plate

• Cookies with 16 holes in which fibers are glued

• PMT holders with PMTs glued to them

5

Cookie and PMT holder attachment

• PMT is glued in a plastic PMT holder

• PMT holder is firmly attached with four screws to the cross bar while the PMT goes through a hole sticking outside of the cross-bar by 1.5 mm

• The WLS (not shown) are glued in the cookie inside 16 holes

• The cookie is attached to the front plate with four screws with springs (not shown)

•Two dowel pins in the cross bar center the positions of the PMT holder and the cookie (along red line)

6

Cookie and PMT holder attachment

• PMT holder is firmly attached with four screws to the cross bar while the PMT goes through a hole sticking outside of the cross-bar by 1.5 mm

•The cookie is attached to the front plate with four screws with springs (not shown)

•Two dowel pins in the cross bar center the positions of the PMT holder and the cookie

7

Outlook

• Prototype of one section of the CDET designed to test mechanically the concept:

The rigidity of the whole construction (trying to minimize distance between planes using only ¼” front plate)

The cross-bar: at some places it has 1.5 mm wall

The technique of gluing PMT to the PMT holder and the fibers to the cookie

The attachment of the cookies (with fibers already glued) to the cross-bar

Stacking the bars at the right angles and strapping them to the front plate

Tolerances: gluing the PMT to the PMT holder, centering the PMT to the fibers

To design tools helping all of the above operations

• The technical documentation is close to completion, expect it in few weeks