Readout System for Medium-Size Experiments

In a vast area of fundamental nuclear/particle physics investigations are performed with relatively simple setups, encompassing up to few thousands of analog data sources. Multiplicity for events in such experiments is usually of the order of few tens. On the other hand, high precision studies require accumulating of large data samples and therefore the readout system must work reliably at trigger rates between one and a few tens of thousands per second, without any significant dead-time. To meet these requirements it is necessary to utilize a fast bus and/or protocol for the data transmission. In contrast to the present generation of high energy physics experiments, here the usage of complicated multiplexing schemes with specially developed chips and boards as well as many-level triggering and event-building techniques is rather disadvantageous. This Chapter describes a readout system which fulfills all the needs of moderate-size experiments and possesses a number of attractive features which allow its easy modification for specific demands. Rather than utilizing possibilities of creating electronic boards tailored strictly to the needs of a particular application, the discussed implementation is based on modular electronics, which parts are still in possession of many laboratories all over the world. In (frequent) cases, when budget limitations do not allow to follow the path of a completely new design of dedicated custom-made boards, application of older electronic modules might be the only way to successfully perform the planned measurements. In the described system use is made of CAMAC based electronics, which turns out to provide data throughput sufficient for most demanding applications. In fact, when the readout is coupled to the front-end processor via VME-bus buffers, it does not feel any speed limits present in the traditional CAMAC-based systems. The described modular electronic system is based on the standard FERA1 configuration, which applications in physics experiments are numerous, see e.g. (Vander Molen et al. 1991; Gazes et al. 1993; Elfman et al. 1997; Hagemann et al. 1999; Okamura 2000; Davin et al. 2001; Karpukhin et al. 2003; Loudos et al. 2004). The full power of the FERA readout system is gained by introducing an additional custom CAMAC module. In spite of its relative simplicity, the module allows to avoid the bounds imposed by the FERA standard. This includes a possibility to prolong the FERA data-bus over many crates for large setups. Configurations of the experimental apparatus require a logical grouping of the signal sources into subsystems corresponding to particular sets of detectors (wire chambers,