A brief description of the start counter and the six slat hodoscope for the MRS is given below.
The start counter and slats are of identical design expect for the length of the scintillator. The scintillator is Bicron 408. It is 1.5cm thick, 5.0 cm high and 100 cm long ( the start counter is 40 cm long). On each end a Hamamatsu PMT ( H2431) is attached with optical cement. The tubes are old tubes from the E802 tof wall. Tubes were crudely tested for dark noise and gain. The “best” were selected for the array. Each counter is wrapped with Tyvek, a layer of heat shrink, and one layer of black vinyl tape. The vinyl tape was added when it was discovered that the heat shrink was not sufficiently light tight. The start counter does not have the heat shrink
The start counter is located approximately 9 cm in front of TPM1. It is centered at the beam height and right/left justified with the TPM1. The signals for the ADCs and TDCs use the channels of modules 35 and 36 of the left beam-beam array. The high voltage uses spare channels in the LRS 4032 which supplies High voltage for the beam-beam large PMTs. The signal cables are RG58 with BNC connectors on each end. The cables are 20 feet long (30ns). The HV cables are 20 feet long RG59 with SHV connectors.
The six slat Hodoscope is positioned behind TOFW. The slats have an overlap with the adjacent slat of 0.5 cm. The slats are staggered with a 4.5 cm distance. The slats are positioned with 25 cm on the right-hand side of the acceptance and 75 cm on the left hand side. The hodoscope is 40 cm behind TOFW in the center and rotated at an angle of 10 degrees. 16 ns RG58 cables were used to connect into the TOFW patch panels for ADCs and TDCs. 20 foot RG59 with SHV connectors is used for high voltage. The MRS 4032 main frame is used. An SHV tee is used at the LRS 4032 to provide both the left and right tube of each slat with the same high voltage. There are no sufficient available channels to provide separate high voltage. The table below provides the electronics matching for this hodoscope.
|
slat |
cable |
Tofw channel |
|
1 Left |
1 |
Bot1 |
|
2 Left |
2 |
Bot2 |
|
3 Left |
3 |
Bot3 |
|
4 Left |
4 |
Bot123 |
|
5 Left |
5 |
Bot124 |
|
6 Left |
6 |
Bot125 |
|
1 Right |
7 |
Up1 |
|
2 Right |
8 |
Up2 |
|
3 Right |
9 |
Up3 |
|
4 Right |
10 |
Up123 |
|
5 Right |
11 |
Up124 |
|
6 Right |
12 |
Up125 |
The numbers of the slats is from top to bottom. Left and Right is defined as looking from the beam vertex to the detector.
The disc. For the slats are presently set for a threshold of –150mV.