SONTRAC

SONTRAC (SOlar Neutron TRACking imaging spectrometer) is being developed to measure the energy and incident direction of 20-250 MeV neutrons produced in solar flares. The intense neutron background in a low-Earth orbit requires that imaging techniques be employed to maximize an instrument's signal-to-noise ratio. Central to the SONTRAC instrument is a bundle composed of mutually perpendicular, alternating layers of parallel, scintillating, plastic fibers. Viewed by opto-electronic devices the bundle provides two orthogonal views of recoil proton tracks. The resulting stereoscopic data are used to determine the incident neutron's direction and energy on an event-by-event basis. Our long-term goal is to fully develop a flight-qualified detector system that will be available for use during the next solar maximum in 2010.

The development to date has included a two-dimensional prototype that was used to validate the basic concept. More recently, testing with a fully three-dimensional science model (SM) has been completed. Current efforts are geared towards the development of new readout schemes that will serve to reduce the size and weight of the full SONTRAC instrument. These improvements will lead to a more viable space-based instrument.