Introduction to H8
As shown in Figure 3.1, the UA9 experiment installs his setup at the beginning of the H8, the SPS extraction line in the North Area (experimental areas 128). Here, many devices are placed along the beam line, starting with the tracker apparatus, probably the main character of the chain, responsible for the track reconstruction. The tracker (or telescope) is composed by five XY-planes, each made of two silicon microstrip detectors; between them, the fourth plane is 45 rotated to solve ambiguities in the reconstruction from multiple outgoing tracks. The five planes forms two arms, one upstream and the other downstream of the crystal, that is installed on a high precision 4-stages goniometer between the second and the third plane (Figure 3.2).
It follows the trigger (a pair of plastic scintillators just after the last plane), which uses criteria to rapidly decide which events in a particle detector to keep when only a small fraction of the total can be recorded. A trigger system is necessary due to real-world limitations in computing power, data storage capacity and rates. Since experiments are typically searching for “interesting” events that occur at a relatively low rate, the trigger identifies the events that should be recorded for later analysis. The ratio of the trigger-rate to the event-rate is determined by the selectivity of the trigger itself.
At the same time of the Crystals tests, UA9 often performs tests and characterizations of new detectors useful for the experiment purposes. These activities take place in the experimental area 138, just downstream the 128 area.