The performance of the GlueX Forward Calorimeter was studied using a small version of the detector and a variable energy electron beam derived from the Hall B tagger at Jefferson Lab. For electron energies from 110MeV to 260MeV, which are near the lower-limits of the design sensitivity, the fractional energy resolution was measured to range from 20% to 14%, which meets the design goals. The use of custom 250MHz flash ADCs for readout allowed precise measurements of signal arrival times. The detector achieved timing resolutions of 0.38ns for a single 100mV pulse, which will allow timing discrimination of photon beam bunches and out-of-time background during the operation of the GlueX detector.

We describe the development of a photovoltaic high-voltage supply, which transforms low-voltage DC to several kV. The device is noise-free since no use is made of alternating current. A prototype has been constructed to generate a variable voltage between 1.8 and 2.0kV for the purpose of biasing a photomultiplier tube. The relative output voltage is stable to better than 0.05% for temperatures between 10 and 34°C and for load currents up to 20μA.