The ARPA Institute is helping promote the advanced RPFMT for single photon detection capability and applications in various industrial and medical fields, through technical and financial means.

An RF timer of keV energy electrons is based on a helical deflector, which performs circular or elliptical sweeps of keV electrons by means of a 500 MHz radio frequency electromagnetic field. By converting the time dependence of incident electrons to a hit position dependence on a circle or ellipse, this device achieves extremely precise timing. Detection of the scanned electrons is implemented using a position sensitive detector based on microchannel plates and a delay line anode. Test studies started with thermo-electrons produced by a Tantalum disc cathode, which has a work function of 4.1 eV. This cathode was also used for experiments with 273 nm (4.54 eV) CW light diodes and 258 nm (4.8 eV) femtosecond laser beams incident on the cathode to produce photoelectrons. In this mode the RF timer became a radio frequency photomultiplier, RFPMT. The experiment with the RF synchronized femtosecond laser beam demonstrated ~10 ps resolution for RFPMT. This 10 ps resolution is mainly due to the technical parameters of the tube and should be relatively straightforward to improve by optimization parameters of the tube, minimizing distance between the cathode and accelerating electrode, and increasing the frequency of the applied RF. A few hundred fs time resolution is expected for single photons with such an optimized device, operated with a 10 GHz RF. A new time-correlated single photon counting technique with RFPMT. All these devices are capable of detecting single photons or electrons and determining their arrival times with a picosecond precision. Consequently, they have potential applications in many fields of science and industry, which includes fundamental physics, high energy and nuclear physics, chemistry, medical and biomedical imaging, and material science. Technological and industrial applications include accelerator physics, laser ranging, dynamic testing of integrated circuits and high-speed optical components for data storage and fiber optic telecommunication. 

Schematic of the RF timer of keV electrons.   1-Tantalum disc cathode; 2-accelerating electrode; 3-permanent magnet; 4-collimator; 5-electrostatic lens; 6-helical RF deflector; 7-RF scanned electrons; 8-dual MCP; 9-position sensitive anode.

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