|
The most important observational challenges remaining in cosmic ray composition will require much increased detector areas to collect rare events while maintaining or improving upon present detector resolution. These goals include extending isotopic abundance measurements to higher energies, measuring isotopes beyond the Fe peak, and making elemental studies with single charge unit resolution through the Pb peak and beyond. Unfortunately, solid state cosmic ray spectrometers have, for practical purposes, approached their limit in collecting area. the fiber optic Cherenkov integrating system (FOCIS) could answer this need. Historically, most cosmic-ray Cherenkov detectors have been of the light-integrating type. The University of Chicago RICH experiment and the CAPRICE experiment are notable exceptions. These instruments measure the Cherenkov light cone to determine the incident particle velocity, avoiding the areal non-uniformities and time-dependent gain variations inherent in light-integrating Cherenkov detectors. FOCIS would use an array of special optical fibers to measure the light cone. These fibers would be simple and robust, could operate over a wide range of temperatures, and would not require onboard consumables (i.e., ionization gas). Fibers can also be left open to vacuum conditions. Thus FOCIS is well suited to balloon flights and long duration space-craft applications. Though the light collection efficiency of FOCIS would be vastly less than RICH or CAPRICE, it would otherwise share their advantages over light-integrating Cherenkov detectors and would be applicable to heavy ion studies. Monte-Carlo simulations of a FOCIS detector are presented. These simulations indicate that FOCIS would have a relatively flat resolution over a range of energies, in distinct contrast to conventional light-integrating Cherenkov detectors.
|
