DELPHI Inner Detector (ID)


Technical description

The Inner Detector (ID) is a tracking and triggering detector. It consists of two parts: the JET chamber and the Trigger Layers (TL). The JET chamber is a driftchamber, subdivided into 24 sectors of 15 degrees in phi. Each sector consists of 24 sense wires, measuring drifttime. The driftgas used is CO2 with a small admixture of Isobutane. This together with the special shaping of the driftfield, makes that for >1.0 GeV tracks coming from the interactionpoint, all 24 signals on the sense wires arrive more or less at the same time.

The TL consist of 5 cylindrical layers of 192 Straw tubes. The tubes in subsequent planes are staggered by half a cell. The cell width is about 8 mm. Pulse heights are measured, and drift times.

Full angular coverage is down to 15 (165) degrees in theta.

It looks like (here with a Z0 in it!)

Quantities measured

For each event, 3 types of information are produced :

Accuracy

Trigger:

Dedicated electronics is used to produce the local trigger results for the first and second level. ID trigger data are correlated with the OD ones in order to reduce the rate due to cosmic and beam gas events. The third level is done by software. The IDOD trigger is very useful to cover the cracks between the TPC sectors.