Large Area Picosecond Photodetectors (LAPPDs) are micro-channel based photosensors featuring hundreds of square centimeters of sensitive area in a single package and timing resolution on the order of 50 ps for a single photon detection. However, until recently LAPPDs did not exist in finely pixelated 2D readout configurations that in addition to the high-resolution timing would also provide the high spatial resolution required for Ring Imaging CHerenkov (RICH) detectors.
One of the more modern LAPPD models, the so-called Gen II LAPPD, provides the opportunity to overcome the lack of pixellation in a relatively straightforward way. The readout plane of Gen II LAPPD is external to the sealed detector itself. It is a conventional inexpensive capacitively coupled printed circuit board (PCB) that can be laid out in a custom application-specific way for 1D or 2D sensitive area pixellation. This allows for a much shorter readout-plane prototyping cycle and provides unprecedented flexibility in choosing an appropriate segmentation that then could be optimized for any detector needs in terms of pad size, orientation, and shape. We fully exploit this feature by designing and testing a variety of readout PCBs with conventional square pixels and interleaved anode designs. Data acquired with the LAPPDs in the lab will be shown using a laser system to probe the response of several interleaved and standard pixelated patterns. Results from beam tests at Fermilab Test Beam Facility will be presented as well, including world’s first Cherenkov ring measurement with this type of a photosensor. 2D spatial resolutions well below 1 mm will be demonstrated for several pad configurations. First data illustrating the prospects of achieving a timing resolution of a RICH detector well below 20 ps by using signals of multiple Cherenkov photons produced by a primary charged particle in a sensor quartz window in a finely pixelated readout plane configuration will be presented.
Very recently, a DC-coupled LAPPD model (High Resolution Picosecond Photodetector, HRPPD) with internal 3.2 mm pixellation became available. Efforts towards building a mechanical and electrical interface for these photosensors, including prototyping of versatile pixelated multi-layer ceramic anode plates, will be presented. HRPPD application as a photosensor in the electron-going endcap RICH detector at the Electron Ion Collider (EIC) will be discussed.