Twenty Years of Rad-Hard K14 SPAD in Space Projects

During last two decades, several photon counting detectors have been developed in our laboratory. One of the most promising detector coming from our group silicon K14 Single Photon Avalanche Diode (SPAD) is presented with its valuable features and space applications. Based on the control electronics, it can be operated in both gated and non-gated mode. Although it was designed for photon counting detection, it can be employed for multiphoton detection as well. With respect to control electronics employed, the timing jitter can be as low as 20 ps RMS. Detection efficiency is about 40%in range of 500 nm to 800 nm. The detector including gating and quenching circuitry has outstanding timing stability. Due to its radiation resistivity, the diode withstands 100 krad gamma ray dose without parameters degradation. Single photon detectors based on K14 SPAD were used for planetary altimeter and atmospheric lidar in MARS92/96 and Mars Surveyor ’98 space projects, respectively. Recent space applications of K14 SPAD comprises LIDAR and mainly time transfer between ground stations and artificial satellites. These include Laser Time Transfer, Time Transfer by Laser Link, and European Laser Timing projects

Three-dimensional gas-liquid simulation of an airlift bubble column reactor

Basic hydrodynamic parameters of an airlift reactor with internal loop were estimated experimentally and simulated using commercially available CFD software from Fluent. Circulation velocity in a 32-dm(3)-airlift reactor was measured using the magnetic tracer method, meanwhile the gas hold-up was obtained by analysis of the pressure drop using the method of inverted U-tube manometers. Comparison of simulated (in two and three dimensions) and experimental data was performed at different superficial gas velocities in the riser

Gas-liquid simulation of an airlift bubble column reactor

The simulation of two-phase flow for an experimental airlift reactor (32-l volume) using commercially available software from Fluent Incorporated is presented here (http://www.fluent.co.uk). Data from the simulation is compared with the experimental data obtained by the tracking of a magnetic particle and analysis of the pressure drop to determine the gas hold-up. Comparisons between vertical velocity and gas hold-up were made for a series of experiments where the superficial gas velocity in the riser was adjusted between 0.01 and 0.075 m s-1. © 2003 Elsevier B.V. All rights reserved