Data Acquisition Black vs White Shahab Khan and Peter Torres

Map of Cells Each Cell was assigned a number Distance between the center of each cell was measured distance was converted to number of pulses from the stepping motor

Distance in terms of pulses Now, There is a map to get to each cell The electronic home position is the center of the center cell Each other cell has coordinates relative to the home position Cell # Left (y) Right (x) 4550,cw ,ccw 2628,ccw 2628,cw 5256,ccw ,cw 2628,ccw 2628,cw

Measurement Procedure Objective to measure each cell’s response to the incidence of radiation from Strontium- 90 at a fixed voltage applied to the PMT There are 12 X 7 = 84 cells total The stepping motor was used to travel to each cell in the unit 500 measurements were made at the center of each cell, the mean values were recorded

Results: noticeable difference All 84 measurements were made (not too enlightening to present entire data here) All cells were in working order There were a lot of variations between different cells, from 397 nA nA There was a trend difference between black painted cells and white painted cells

Results: comparing two units

Possible sources of difference In general, there will be some variation in the output of each cells due to the variation of the thickness of the paint applied to each cell The energy of the radiation is low enough such that the skin depth penetration of the radiation is noticeable

Radiation reflects around inside the white coated cells until the photons enter the optical guide Some radiation transmits through the cell walls into the other cells Black paint was used to cover the white paint in order to reduce cross-talk The black paint will absorb some of the radiation

In addition, the black paint may have seeped through the pores in the white paint Thus reducing the effectiveness of the white paint to reflect the radiation If we increase the white paint, the skin depth will increase and we reduce the output current

Future Tests to determine how effective is the black paint compared to white paint to reduce cross talk Topological scan of surface of the unit of cells