Pulse Width Modulation controller based Thermal Stabilization for Iodine evaporation inflowing chemical laser

Abstract

Present paper focuses upon development of thermal stabilization scheme based on pulse width modulation (PWM) controller used for iodine evaporation in flowing chemical laser. Iodine acts a lasing medium in chemical oxygen iodine laser (COIL). In COIL, iodine crystals are put in iodine chambers and needs to be continuously evaporated in order to get vapor iodine. For efficient COIL operation, stabilized iodine evaporation is one of the prime needs. In addition, iodine transportation lines are also required to be heated to ~ 75°C-85°C in order to restrict the iodine deposition during transport. Iodine being hazardous to human beings, the said thermal operation has to be continuously monitored and controlled to provide uniform flow of iodine during safe laser operation. Thermal actions are performed by using several rod heaters and belt heaters. A PWM controller based in house thermal stabilization scheme has been developed using feedback mechanism for iodine evaporation with an accuracy of ±0.5°C instead of using commercially available controllers. It comprises of Operational Amplifier LF 356, Instrumentation Amplifier (IA) AD 620, LM 339 Comparator ICs, K type thermocouple and solid state relay (SSR).The developed hardware has been interfaced with data acquisition system (DAS) and all the temperatures were monitored and recorded online.