Many remote sensing instruments include the detection of photon/particle events, position decoding and time-of-hit measurement. Microchannel plates (MCPs) are widely used to detect photons and particles for position sensing and relative time of impact in imaging and time-of-flight (TOF) spectrometers. Two dimensional delay lines are used for fast and accurate readout of MCPs. Instruments that use these techniques are Neutral Atom Imagers and Particle Spectrometers to study planetary magnetospheres; photon counting detectors for spectrographic imaging in the far-UV and extreme-UV to study the earth's aurora and airglow; laser range finders. In all these there is a requirement of accurate and/or fast time interval measurement. An advance TOF system-on-a-chip has been developed that includes the complete signal processing electronics for MCP readout: two channels (start- stop) of amplifiers and constant fraction discriminators (CFDs), an 11-bit Time to Digital Converter (TDC), and control/readout logic. The TOF chip is capable for a time resolution of <50ps including time walk and time jitter, the dead time is as low as 0.5us; the power dissipation is a function of counting rate and time resolution-for resolution of ~100ps the power is <20mW at rates <100K/sec and <50mW at rates <1M/sec. The TOF chip flies on the NASA/IMAGE spacecraft launched in 2000 and is part of many other science instruments such as particles and fields, and laser altimeter on MESSENGER.
We present result from laboratory testing of a compact Energetic Particle Detector capable of making particle measurements in a variety of heliospheric and planetary environments. This ion composition telescope utilizes a novel electron-optics design and newly developed microcircuits to achieve combined directional particle flux measurements and high resolution mass spectroscopy in an extremely lightweight and low power package. The detector design provides for a high geometric factor and reasonable directional capability while maintaining excellent resistance to background radiation due to its small size and specialized coincidence logic. The prototype device, with an integrated time-of-flight custom integrated circuit, has been extensively characterized with electronic pulsers, radioactive sources in a vacuum chamber, and accelerator particle beams, revealing performance which substantially meets all requirements for mass resolution, bandwidth, power consumption, and weight allocation. A flight version would provide comprehensive measurements of the energetic particle environment on a mission where payload mass is tightly constrained, such as solar probe or a discovery-class mission.
We are developing an Energetic Particle detector capable of making particle measurements in a variety of heliospheric environments, and, in particular in the outer corona of the sun. The current concept is a miniature ion composition/electron telescope that will measure the energy spectra, mass composition and detailed pitch angle distribution of energetic ions and electrons from approximately 10 keV per nucleon to approximately 3 MeV total energy. The telescope is made up of two main components: a time of flight section and a solid state detector array. A collimator defines the acceptance angles for the incoming particles while the time of flight and solid state detector sections measure the velocity and energy of the ions. Electrons are recorded as essentially zero time of flight particles. The miniaturized detector is approximately 100 mm in diameter and measures particles in 6 angular sectors across 140 degree(s); each sector has an opening angle of 12 degree(s) in the orthogonal direction. Extensive use of VLSI techniques and chip on board design allows all electronics to be mounted on circular boards that mate directly to the detector. The entire instrument is less than 0.5 kg in mass and requires less than 0.5 W of regulated power.