The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) and the data processing unit (S3DPU) for SWICS, SWIMS and SEPICA

The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) ir; the main in strument on the Advanced Composition Explorer (ACE) to determine the ionic charge states of solar and interplanetary energetic particles in the energy range from approximate to 0.2 MeV nucl(-1) to approximate to 5 MeV charge( -1). The charge state of energetic ions contains key information to unravel source temperatures, acceleration, fractionation and transport processes f or these particle populations. SEPICA will have the ability to resolve indi vidual charge states and have a substantially larger geometric factor than its predecessor ULEZEQ on ISEE-1 and -3, on which SEPICA is based. To achie ve these two requirements at the same time, SEPICA is composed of one high- charge resolution sensor section and two Low-charge resolution, but large g eometric factor sections. The charge resolution is achieved by the focusing of the incoming ions, through a multi-slit mechanical collimator, deflecti on in an electrostatic analyzer with a voltage up to 30 kV, and measurement of the impact position in the detector system. To determine the nuclear ch arge (element) and energy of the incoming ions, the combination of thin-win dow Bow-through proportional counters with isobutane as counter gas and ion -implanted solid state detectors provide for 3 independent Delta E (energy loss) versus E (residual energy) telescopes. The multi-wire proportional co unter simultaneously determines the energy loss Delta E and the impact posi tion of the ions. Suppression of background fi om penetrating cosmic radiat ion is provided by an anti-coincidence system with a CsI scintillator and S i-photodiodes, The data are compressed and formatted in a data processing u nit (S3DPU) that also handles the commanding and various automatted functio ns of the instrument. The S3BPU ir shared with the Solar Wind Ten Charge Sp ectrometer (SWICS) and the Solar Wind ion Mass Spectrometer (SWIMS) and thu s provides the same services for three of the ACE instruments. It has evolv ed out of a lone family of data. processing units for particle spectrometer s.