Sep. 24, 08 daytime

ND TEST#1
The purpose is to investigate the linearity of the analog signal, especially the 0-1km region of the low-altitude channel.
Integration time = 10 min
There is a 10 min temporal difference of data1 and data2. The configurations of data1 and data2 are the same excpet data2 has a ND with optical density equal to 1.

Channel 2:
The nonconstant ratio of data1/data2 for analog signal suggests that data2 signal has nonlinear behavior under ~1km. But the PC signal under 4MHz looks linear after a 5ns dead-time correction. We expect a more linear agreement between data1 and data2 after SIB correction.

Channel 5:
The ratio of analog looks basically constant, also for the PC under ~3MHz. Data1/data2 of analog has a slightly negative slope at initial bins which is similar with the ratio of ungated/gated signal. The dead time is estimated about 10ns which is different with that in channel-2 due to different PMT.