Testing SEPICA

We helped to prepare SEPICA for testing by mapping out the collimator. The device that hold the radiation source is controlled by a computer program which allows us to move the device horizontally and vertically. The program only reads the number of rotations the device has gone in a certain direction. Our map corresponds the program's position readout to the physical position in front of the collimator.

Point	X (mm)	Y (mm)	Computer's x (P)	Computer's y (p)
A	5	5	0	0
B	45	7	220	39
C	107	7	464	39
D	175	7	706	39
E	240	7	939	39
F	240	45	1112	251
G	250	45	1230	248
H	310	45	1462	246
I	375	45	1698	221
J	440	45	1936	208
K	480	45	2109	198
L	480	105	2117	477

We wanted to determine where the radiation source should be placed in order to achieve the greatest throughput. We did nine runs of alpha particles with no deflection, each positioned a different place on the collimator. This drawing represents the top right quadrant of the collimator. These are the throughputs we obtained for each position:

2.8%	2.2%	1.4%
5.5%	9.3%	7.4%
50.4%	54.3%	51.4%

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