User:Sergio.ballestrero/Data acquisition

Work in Progress for Data acquisition

- many terms will need explainations, foot notes (how to make them?) or links

DAQ in Nuclear and Particle Physics

In nuclear and particle physics, data acquisition is a fundamental part of the chain that connects the material experiment to the physical interpretation.

The starting point of the chain are the particle detectors, like scintillators or drift chambers, that pick up a signal from the event. The initial signal may be directly an electrical signal, or for example a light signal, that needs to be converted to an electrical one (via a photomultiplier). This electrical signal undergoes analog processing, usually by a preamplifier (located near to the detector) and by a shaping amplifier (or spectroscopy amplifier) that also acts as a noise rejection filter.

The amplified analog signal can then be used in different ways. It can be fed to an ADC to record the amplitude of the signal amplitude ^[1] , or it can be used as input to a discriminator (a simple threshold discriminator or a constant fraction discriminator) to generate a logic signal.

A logic signal can be applied to a TDC, to a scaler unit, a pattern unit, or be used for the trigger logic chain.

The analog electronics and the trigger logic are most often implemented in NIM modules.

The signals are trasmitted on coaxial cables with matched impedances for input, output and the cable itself. For high precision spectrosopy the preferred choice are 93 ohm cables with BNC connectors, while 50ohm cables with BNC or LEMO connectors are for general analog signals and NIM standard logic signals. Logic signals in ECL standard can instead be trasmitted on standard ribbon cable or, for longer distances or for higher noise immunity, on twisted pair ribbon cables.

Notes

1. ^ a spectroscopy amplifier is normally used for charge signals, like those from scintillators or semiconductor detectors, and it operates by integrating the current signal, producing a voltage signal
2. ^ the amplitude of the signal, be it either a voltage amplitude or a charge amplitude, is usually proportional to the physical signal, for example the energy deposited in a scintillator or in a silicon detector

References

• W. R. Leo: "Techniques for Nuclear and Particle Physics Experiments", Springer, 1994, ISBN 3-540-57280-5