Next‐generation solid‐state detectors for charged particle spectroscopy

The performance of silicon avalanche photodiodes (APDs) and single crystal chemical vapor deposit diamond detectors (DDs) are reviewed in comparison with conventional silicon based solid-state detectors (SSDs) from the perspective of space plasma applications. Although the low-energy threshold and the energy resolution are equivalent to SSDs, DDs offer a high radiation tolerance and very low leakage currents due to a wider band gap than silicon. In addition, DDs can operate at higher temperatures, are insensitive to light (>226 nm), and are capable of timing analysis due to the higher intrinsic carrier mobility. APDs also offer several advantageous features. Specificially, APDs have a lower energy threshold (<0.9 keV) and a higher energy resolution (<0.7 keV FWHM at room temperature), along with a linear response due to a strong electric field causing signal amplifications within the detector. Therefore APDs can be used to detect lower-energy particles, covering a larger portion of the energy spectrum than conventional SSDs. Further, the strong internal electric field gives them a sub-nanosecond response time by the charge mobility saturation, allowing them to make precise timing measurements of ions. These novel detector techniques can be potentially applied to improve the measurements of suprathermal particles, whose energies lie between typical ranges of conventional sensors for low-energy plasmas and energetic particles. Although the origin and evolution of the suprathermal particles are the key to understanding the acceleration and heating processes in space plasma, they are not well understood due to the technical difficulties of making the measurement.