Abstract
Photek (U.K.) and the TORCH collaboration are undertaking a three year development program to produce a novel square MCP-PMT for single photon detection. The TORCH detector aims to provide particle identification in the 2–10 GeV/c momentum range, using a Time-of-Flight method based on Cherenkov light. It is a stand-alone R&D project with possible application in LHCb, and has been proposed for the LHCb Upgrade. The Microchannel Plate (MCP) detector will provide a single photon timing accuracy of 40 ps, and its development will include the following properties: (i) Long lifetime up to at least 5 C/cm2; (ii) Multi-anode output with a spatial resolution of 6 mm and 0.4 mm respectively in the horizontal and vertical directions, incorporating a novel charge-sharing technique; (iii) Close packing on two opposing sides with an active area fill factor of 88% in the horizontal direction. Results from simulations modelling the MCP detector performance factoring in the pulse height variation from the detector, NINO threshold levels and potential charge sharing techniques that enhance the position resolution beyond the physical pitch of the pixel layout will be discussed. Also, a novel method of coupling the MCP-PMT output pads using Anisotropic Conductive Film (ACF) will be described. This minimises parasitic input capacitance by allowing very close proximity between the frontend electronics and the MCP detector.
Highlights
Photek (U.K.) and the TORCH collaboration are undertaking a three year development program to produce a novel square Microchannel Plate (MCP)-PMT for single photon detection
The performance of a detector using a charge sharing technique for interpolating between physical readout pads is impacted by several factors from the MCP detector design, the exact geometry of the hybrid anode and performance of the readout electronics
The TORCH project presents a number of challenges for designing a suitable photon detector for their application, requiring long lifetime (5 C/cm2 extracted charge over detector lifetime), high rate operation (36 MHz/cm2 detected photon), high time resolution (< 50 ps) and a high channel count/density readout in a square form factor for minimum dead area
Summary
The TORCH spatial resolution requirement of 8 × 128 pixel readout in a 53 × 53 mm square detector could be solved using a multi-anode MCP-PMT, with an anode pitch of 0.414 mm in the fine direction. The detector in development for TORCH uses a structured 8 × 64 structured multi-anode readout, chosen to meet detector occupancy requirements, which at a detected photon rate of 36 MHz/cm requires that no more than three neighbouring readout pads can be used for the charge sharing calculation. This choice avoids pulse pile up, where neighbouring events overlap on the readout anode compromising cluster identification and the imaging algorithm which will see only one event with a position at the centre of gravity of the two events. The MCP detector’s hybrid anode has been designed as a 64 × 64 device, with an external printed circuit board to connect eight neighbouring pads in the coarse resolution dimension to form a single channel
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