05/12/2011 random coincidence cosmic test

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The powers are:

PS1 and PS2:  -1000 V (the old 2-channel TENNELEC TC952)
n's: -1100 V (the new 2-channel C.A.E.N N471)

The thresholds are:

PS1 and PS2:  -80 mV
n's: -200 mV

The discriminator widths are:

PS1: -20 ns
PS2: -10 ns
n's: -20 ns

Let's do the random coincidence cosmic ray test 1.

PS1 and PS2 is about 30 cm away from each other. And let's look on the coincidence signal between PS1 and PS2:

	total counts	time	counts/min	counts/sec
PS1	[math]10247\pm101.2[/math]	70 min	[math]146.4\pm1.44[/math]	[math]2.44\pm0.02[/math]
PS1	[math]12969\pm113.9[/math]	70 min	[math]185.3\pm1.63[/math]	[math]3.09\pm0.03[/math]
PS1+PS2 (30 cm away)	[math]3\pm1.7[/math]	70 min	[math]0.043\pm0.024[/math]	[math]0.0007\pm0.0004[/math]

And below my scope pictures of this rear event:

Let's do the random coincidence cosmic ray test 2.

But now the distance between PS1 and PS2 is about 5 cm. And let's look on the coincidence signal between PS1 and PS2:

	total counts	time	counts/min	counts/sec
PS1	[math]\pm[/math]	70 min	[math]\pm[/math]	[math]\pm[/math]
PS1	[math]\pm[/math]	70 min	[math]\pm[/math]	[math]\pm[/math]
PS1+PS2 (5 cm away)	[math]\pm[/math]	70 min	[math]\pm[/math]	[math]\pm[/math]

And below my scope pictures of no so rear event as before:

So what is that?

purely random events from different reaction?. But why they are depend from distance?

maybe some of them is the sub-products from one events separated in space? (air showers)