FAST BEAM TRIGGER


Technical description
---------------------
A new fast trigger system has been installed at H8 beamline at the SCT site.
The trigger signal is determined by coincidence of 2 plastic scintillator
signals T1 and T2. The 2 scintillators + PMTs (Philips XP2020) are located
on the beam in front of tested modules. The PMTs are fed by HV Power Supply
(Wenzel Elektronik N1130) at the counting room in a NIM crate. Anode signals
from the PMTs go to discriminators (Tennelec TC 454 Quad CFD) in the same crate.
Coincidence Unit (LeCROY 465) generates the trigger signal using the output
logic signals from the discriminators.

Cabling and preset parameter values of the setup are marked in a table:

------------------------------------------------------------------------*
					T1		T2		*
------------------------------------------------------------------------*
position				lower		upper		*
									*
cables:									*
	HV supply			T1 red		T2 red		*
	HV output no. (rear)		3		4		*
	PMT signal			T1 black BNC	T2 black BNC	*
	discriminator signal		T1 LEMO		T2 LEMO		*
	discriminator channel no.	2		3		*
									*
parameters:								*
	HV suply			-2000V		-2000V		*
	discriminator threshold		-0.6V		-0.6V		*
------------------------------------------------------------------------*


Usage
----

Switching ON:
	Switch ON HV supply and wait until green LED is on.
Switching OFF:
	Switch OFF HV supply.

Checking HV, current:
	Use V/I monitor output at the HV suply.

Contact
-------
         Charles University Prague group, 
         Zdenek.Dolezal@cern.ch, 
         Vit.Vorobel@cern.ch