Modifications for the Aerogel Cerenkov counter

The most important change for the electronics between the Aerogel Cerenkov counter and the Ring Image Cerenkov counter is the difference of the characteristics of PMT. Also, the mean photo-electrons per one PMT is changed. Thus, the gain and time constant of pre-amplifier should be changed. The PMT characteristics of each detectors are shown in Table 5.

表 5: The PMT characteristics for each detectors.

	Aerogel	RICH
Type	Hamamatsu E6316-01 (improved)	H71315
The number of channel	600 (300*2)	5120
Gain	$10^7$	$10^7$
Mean p.e per PMT	$\sim 10$	$\sim 3$
Typical pulse height	70mV	$20mV$
Rise time	15 ns	2 ns

The possible modifications for the Aerogel Cerenkov counter are follows.

• Gain of the pre amplifier should be changed to match the dynamic range of the Int-R chip and the AMU/ADC chip.
• Band width of the pre amplifier and the Int-R chip should be checked. In fact, the rise time of the PMT signal of RICH is smaller than that of Aerogel. Thus, band width should be enough for the Aerogel PMT.
• The number of channel on one board could be changed. It depends on the layout of the detector and the trigger scheme.