Speaker
Description
Summary
The present R&D is aimed at creating a newly compact, portable and rather
fast
appliance, performing the mostly used input front-end functions of an analog
channel within conventional detector electronics, and also allowing an
experimentator to use it as an elementary unit while composing a stack of these
channels in quantity over the limit assigned per unit.
In distinct from schematics of any wide spread manufactured signal
discrimanators, the given FAD (Fast Adder/Amplifier/Discriminator) deliver
physicists a feasibility of linear, prompt on the FAD inputs, summing any random
selected pairs of detector signals with next amplifying pulse sums by a gain
factor of 10 or 20.
This featuring leads to some FAD's advantages such as an extended dynamic range
of accepted detector signals, and a better signal to noise ratio as well.
Another distinction is the FAD can admit signals coming both from a scintillator
with an attached PMT, and/or from a MWPC-like detector; that goes right because of
input high voltage capacitors foreseen as optionally mounted in the FAD boards.
A basic FAD unit handles up to 4 input signals accepted thru high-frequency on-
board coaxial connectors. The unit contains two identical channels, where each
channel comprises a linear adder of 2 detector signals from the adjacent inputs,
a fast amplifier of the sum pulse, a high-speed leading edge discriminator (LED)
of this amplified sum, and a fast ECL- compatible output signal shaper as well.
Due to application of the best slew rate commercial SMDs, like 1 GHz operational
amplifiers and high-speed comparators from ADI, the FAD is able to support 320 MHz
input pulse bandwidth at the 20 dB gain factor.
Therefore, the basic FAD unit, of the 120x30 mm^2 printed circuit board (PCB)
dimensions, can be taken for a very fast and wide range front-end cell.
It goes to sum, to amplify, and to discriminate, according to regulated threshold
settings, 4 detector signals of above 1.1 ns rise time and 20 fC charge as minimum,
producing 2 balanced (+/-) and their "OR" ECL signals in outcome.
The first series of NIM standard modules, based on the FAD units, is prepared to
provide triggering and registering events within a 160-output scintillator detector
system, which is under construction to verify the ALICE TRD chambers by exposing
them in cosmic background or stimulated X-ray radiation.
Each of those NIM front-end electronic modules accumulates an assembly of 4 basic
FAD units, thus providing 16-input (8-channel) segment of the system. There are also
some additional schematics to elaborate an accurate setting of the controlled FADs'
threshold, and to convert all FADs' "OR" ECL signals into 2 output NIM-level
signals of an adjusted duration.
The series of 10 manufactured modules, lined in a system row, where
discriminating threshold can be set either separately for each module, or jointly
by a "daisy-chain" for a group of applied modules, completely cover all needs of
the pointed 160-output(80-channel) ALICE testing bench, which should be considered
like a pilot experience to further application and development of the FAD concept.
