2011/04/21

1800	Start tower removal procedure.
2100	Tower taken to clean room.
2300	Lifting source holder reveals fallen screw on Q2. It comes from the Q3 housing. It's tall enough to short Q2 to chassis, so it is reasonable to assume that it fell out during diassembly. Otherwise we would have seen some sign of this in the data.
	Wire bonds look intact.
	DIB1 is at the bottom of the photographs in Figure 1. The Am-241 source above Q3 was located on the other side of the scratch to this DIB.

Figure 1: View of crystal upon lifting off source holder. It is likely that the screw fell out during the disassembly process.

Larger image: 1536 × 2048	Larger image: 2048 × 1536

2330	GM-tube placed over collimation holes show no activity above the background rate for any of the sources. We expect 20 Bq. GM-tube exposed to test source shows the expected count rate, illustrating that it works. All sources show a rate of 30 Bq when the lead disc and copper plate are removed: lower than expected from a 1 μCi (37 kBq) source. GM-tube is inefficient, and probably not sensitive enough to measure low count rates. Perhaps there is another way to perform this measurement.

2330

GM-tube placed over collimation holes show no activity above the background rate for any of the sources. We expect 20 Bq. GM-tube exposed to test source shows the expected count rate, illustrating that it works. All sources show a rate of 30 Bq when the lead disc and copper plate are removed: lower than expected from a 1 μCi (37 kBq) source. GM-tube is inefficient, and probably not sensitive enough to measure low count rates. Perhaps there is another way to perform this measurement.