Extended forward tracking: annular MRPC

The BGO and forward spectrometer does not cover the full acceptance in the laboratory system, especially not in the forward direction. Between θlab = 25 degrees (BGO) and θlab = 8/12 degrees (Dipolespectrometer) the system is blind. To cover this region with a system for at least charge particle detection we are planning to install a phi-symmetric Multi-gap Resistive Plate Chamber (MRPC). This sub-detector is a contribution from external collaborators (INFN Rome and University of Rome).

Figure 3.46: left CAD drawing of the MRPC with 16 phi sectors MRPC. right MRPC and its support structure included in the experiment, between BGO (only rail system visible) and forward spectrometer.

The active area of the annular MRPC is covering a range between θmin = 8 degrees (radiusmin = 140 mm) and θmax = 25 degrees (radiusmax = 430 mm). The detector consists of two stacks, is divided in 16 phi sectors and has in total 480 channels. The expected spatial resolution is 1 cm2 and the time resolution is about σt ≈ 50 ps. Since the MRPC is a ”stop” detector, a ”start” detector is needed. For this pupose an additional detector with a high time resolution can be installed in the tagging range or alternatively, the tagging hodoscope can be used. Figure 3.46 shows a technical drawing of the installed MRPC in the detector setup. The readout system will be instrumented with 16 modules of 32 channel multihit TDC (CAEN V1290A) with a 25 ps resolution (LSB). The required operating resources are a 15 kV high voltage supply and gas mixture of 96% C2 F4 H2 + 3% C4 H10 + 1% SF6.

All necessary material for the construction is already purchased and the detector is currently under construction. The support structure at the experimental area will be installed in October 2012. In parallel final performance tests of the full detector will be prepared and perfomed in November 2012 at CERN (T10 beamline). The detector and the electronic chain will be fully equipped and ready in spring 2013. Figure 3.47 shows a picture taken during the manufacturing of a prototype detector.

Figure 3.47: Photograph of MRPC prototype.