RESEARCH OF RADON DETECTION BASED ON AIR MESH AND PULSE IONIZATION CHAMBER AT NORMAL

摘要

The research of radon detection based on air mesh and pulse chamber at normal is presented in details. The Instrument consists of air mesh, pulse chamber, signal amplification and discriminator and MCU. Radon of ambient air can directly make a free diffusion to the high-pressure chamber, because The Instrument uses a new type of atmospheric air-gridded pulse ionization chamber, ventilated with ambient air.A voltage pulse in the Resistance connected to Collecting electrode is produced when the charged particles moving through the gas in high-pressure chamber, can make the air ionize to create the charged ion-pairs (negatively charged ion and positively charged ion),which drift to the cathode and anode respectively with the effect of the directional electric field.The voltage pulse height represents the ionizability of an incident particle. And the relative counting can be made for the incident particles, reflecting the changes of the radon concentrations in air, and the total measurement too. But the pulse signal, from Front-end detector, is very weak, so they need to be amplified and shaped by amplification and discriminator circuit and RC-CR band-pass filter, compared with a given threshold voltage through the Pulse discriminator to produce the digital signals which micro-controller system can handle and for which SCM can make the counting, storage and display. Then, this Instrument is a design of appropriate devices for short-term measurements, and some criteria used in the design of this instrument are field measurements applicability, portability, convenience and reliability.