Spatial Distribution Of Charged Particles Research Articles

Charged species profiles in oxygen plasma

The charged species profiles have been studied in oxygen plasma of asymmetrically driven capacitively coupled rf discharge. The electron (ne), negative (n), and positive (p) ion densities have been measured by Langmuir probe in a wide range of pressures (3–30 Pa) and interelectrode distances (2–10 cm). At small powers (ne<1015 m−3) it was obtained that the electronegativity is high (n/ne∼10) and the electron density profile is flat in plasma bulk. The negative ion density profile is nearly flat in the ion–ion core, where n≫ne, and falls off towards the plasma-sheath boundary with n≈0 with the spatial scale πDn/(2γd), determined by the negative ion diffusion coefficient Dn and detachment frequency γd. As the pressure decreases, this spatial scale exceeds half of the interelectrode distance and the negative ion density profile tends to a parabolic one. The obtained spatial distributions of charged particles are compared with the results of self-consistent modeling by use of a fluid approach for ions, and kinetic equation for electrons. Numerical simulation results agree well with both theory predictions and measurement data.

Amorphous silicon pixel radiation detectors and associated thin film transistor electronics readout

We describe the characteristics of thin (1 μm) and thick (> 30 μm) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays, γ rays and thermal neutrons. For x-ray, γ ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For thermal neutron detection we use thin (2∼5 μm) gadolinium converters on 30 μm thick a-Si:H diodes. For direct detection of minimum ionizing particles and others with high resistance to radiation damage, we use the thick p-i-n diode arrays. Diode and amorphous silicon readouts as well as polysilicon pixel amplifiers are described.

Amorphous silicon based radiation detectors

We describe the characteristics of thin(1μm) and thick (>30μm) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and γ rays. For x-ray, γ ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays.

Equilibrium spatial distribution of charged particles

Equilibrium spatial distribution of charged particles