SiPM Based Focal Plane Detectors Operated Alongside PMTs for Large Imaging Atmospheric Cherenkov Telescopes

We describe the design, construction, and subsequent operation in the telescope camera of two modules based on two different silicon photomultiplier (SiPM) detectors. Based on simulation results and initial prototypes, pixel detectors with an active area of 324 mm 2 have been fabricated, along with their associated control electronics and specially designed light concentrators. A low-noise analog pulse summation circuit was used to implement rapid signal response (~2.5 nsec) for this detection area while maintaining resolution of individual photoelectron peak spectra used for calibration. Data recorded during camera operation is analyzed for comparison to the photomultiplier devices.