Particle Detectors
MASS
The High MASS Resolution Spectrometer (MASS), part of the SMS Package on WIND, is designed to measure the elemental and isotopic composition of the solar wind from 0.5 to 12 keV/e. MASS combines an electrostatic deflection system with a static electric harmonic potential inside the time-of- flight analyzer to obtain mass resolutions of M/?M ~ 100. As ion passes through a thin carbon foil to enter the time-of-flight system secondary electrons are scattered and collected by a microchannel plate (MCP) to generate a start signal. The harmonic potential causes the ion to travel in a parabolic trajectory, impinging on a second MCP to create the stop signal. The potential also causes the time-of-flight (calculated from the start and stop pulses) to be only a function of the mass/charge* of the particle, where the charge is that of the ion after passing through the carbon foil. Since most of the particles emerge either neutral or singly charged the calculated time-of- flight is proportional to mass (a time-of-flight is not determined for the neutral particles). For more information, see: http://space.umd.edu/wind/sms.html