Electron scintillators eSC

The electron hodoscope will be instrumented as a detector system which can operate independently or in coincidence with the chamber system. The array consists of inner and outer scintillators. Each detector slab is about 84 cm long and 14 cm wide. Each element will be read out on both sides with photomultiplier tubes. This allows reconstruction of the (detector element) and z position (time difference) of the electron trajectory. We plan both analog (using MHz wave form digitizer) as well as digital readout (using CAEN TDC's) of the detectors. The scintillator is a simplified version of the proposed MuLan detector. We hope to exploit the synergy between the two projects both in detector hardware and the above mentioned analog readout.

Within the next few months the following studies to define the final geometry of the hodoscope elements will take place.

• We will test prototypes of different thickness (3 mm to 1 cm) to study the light collection efficiency and homogeneity. Good collection efficiency allows low discriminator thresholds, which reduce our sensitivity to threshold/stability variations. Although this sensitivity is less critical in a dc experiment than in a pulsed mode, it still should be kept as small as possible.
• The end face of the scintillator has a very similar size as the MuLan tiles. Thus we will use similar lightguides and phototubes. In order to finalize the light guide design we plan to compare to the collection properties of the light coupling using a 45 reflective mirror to ideal adiabatic strips.

The 64 phototubes of the electron hodoscope will each have their own CAEN TDC channel. Sufficient discriminator channels are available at UIUC. The z resolution will be limited by the relatively poor TDC bin width of 1.6 ns. The analog readout will allow a time resolution of $\sim$0.2 ns. Moreover it also permits walk and attenuation corrections as well as careful pile-up studies.