R.K. Tyagi

Parametric studies of a supersonic COIL with angular jet singlet oxygen generator

Chemical oxygen-iodine laser (COIL) having a wavelength of 1.315 μm has been developed using a singlet oxygen generator (SOG) with a novel approach. Generated singlet oxygen is taken out of the SOG at an angle of 40° to avoid the problem of carry over of droplets, which is one of the major drawbacks of horizontal systems. The system has been operated using uncooled nitrogen as a buffer gas. The paper reports the results on the studies carried out on this COIL system. Under optimum conditions, we have been able to achieve stable and reproducible output power of 350 W for a chlorine flow rate of 22 mmol/s thus yielding a chemical efficiency of 17.5%.

Supersonic COIL with angular jet singlet oxygen generator

Abstract Supersonic Chemical Oxy-iodine Laser has been developed using a Singlet Oxygen Generator (SOG) with a novel approach. Generated singlet oxygen is taken out of the SOG at an angle of 40° to avoid the problem of carry over of droplets, which is one of the major drawbacks of horizontal system. The system has been operated up to 22 mmol/s chlorine flow rates. Chlorine utilization and singlet oxygen observed have been more than 90% and 60%, respectively. The observed maximum output power was 350 W , thus yielding a chemical efficiency of 17.5%.

Design and realization of a 500W-class jet-type singlet oxygen generator with angular exit

Singlet Oxygen Generator ( SOG ) with a novel approach has been designed and fabricated. Singlet oxygen is taken out of the SOG at an angle of 40° thus avoiding the carry over of droplets, which is one of the major drawbacks of horizontal system. The paper discusses various design parameters for such type of SOG. For flow rates of chlorine up to 22 mmol/sec, the chlorine utilization and singlet oxygen yield have been observed to be ~ 90% and ~64% respectively.

Diagnostics and Data Acquisition for Chemical Oxygen Iodine Laser

This paper focuses on the implementation of various diagnostics for optimizing chemical oxygen iodine laser. This paper also dwells on the measurement methodologies and instrumentation employed in these diagnostic systems. The prime diagnostics are for the measurement of vital species in form of iodine, singlet oxygen, and chlorine. Iodine concentration measurement (absorption at λ = 499 nm ), chlorine utilization (absorption at λ = 330 nm), and singlet oxygen yield (emission at λ = 1.27 μm) have been implemented based on optical absorption/emission principle. Furthermore, online Mach number determination, which is critical for supersonic gas flows, laser pulse detection (at λ = 1315 nm ), and flow rate measurement and control over wide range, have been carried out. A dedicated diagnostics and data acquisition system (DDAS) customized for parameter monitoring have been developed. The developed DDAS also serves the purpose of precise operation sequencing and parameter control. It is a 168-channel personal-computer-based system with customized interface electronics employing Visual C++ programming language with user-friendly graphical user interfaces. A detailed uncertainty analysis of various critical parameters has been also presented.

CHARACTERIZATION AND STUDIES ON HYDRO DYNAMICALLY STABLE OPERATION OF AN ANGULAR JET SOG FOR COIL

Chemical oxygen-iodine Laser (COIL) is one of the fast emerging high power laser source for near Infrared (λ=1.315μm) laser generation. The heart of the system is the singlet oxygen generator (SOG) which is a pumping source for this laser. A Jet type SOG with a novel approach was designed and fabricated. Singlet oxygen was taken out of the SOG at an angle of 40° thus avoiding the carry over of droplets, which is one of the major drawbacks of horizontal system. The preliminary results have been reported in our earlier publication. The present paper discusses the performance of this generator for various operational conditions viz. diluents gas nitrogen / helium, basic hydrogen peroxide composition, generator pressure and gas velocity. Further, conditions for the stable operation from generator as well as chlorine injection point of view have been identified.

Real-time data acquisition and control system for a chemical oxygen–iodine laser

A user-friendly data acquisition and control system (DACS) for a chemical oxygen–iodine laser (COIL) has been developed. The system is capable of handling 117 analogue/digital channels for performing various operations such as on-line acquisition, control, display, safety measures and status indication of various subsystems. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a COIL. The DACS system has been programmed using Advantech-GeniDAQ software. This software has also been used to convert the acquired data into graphical form. Using this DACS, more than 200 runs were given performed successfully.

Performance comparison of supersonic ejectors with different motive gas injection schemes applicable for flowing medium gas laser

A class of flowing medium gas lasers with low generator pressures employ supersonic flows with low cavity pressure and are primarily categorized as high throughput systems capable of being scaled up to MW class. These include; Chemical Oxygen Iodine Laser (COIL) and Hydrogen (Deuterium) Fluoride (HF/DF). The practicability of such laser systems for various applications is enhanced by exhausting the effluents directly to ambient atmosphere. Consequently, ejector based pressure recovery forms a potent configuration for open cycle operation. Conventionally these gas laser systems require at least two ejector stages with low pressure stage being more critical, since it directly entrains the laser media, and the ensuing perturbation of cavity flow, if any, may affect laser operation. Hence, the choice of plausible motive gas injection schemes viz., peripheral or central is a fluid dynamic issue of interest, and a parametric experimental performance comparison would be beneficial. Thus, the focus is to experimentally characterize the effect of variation in motive gas supply pressure, entrainment ratio, back pressure conditions, nozzle injection position operated together with a COIL device and discern the reasons for the behavior.

Modeling of a Transversely Pumped Aprotic Liquid Laser

The present paper discusses laser kinetic modeling of diode pumped flowing medium aprotic liquid laser containing Nd3+ ions in POCl3 solvent host. Transverse pumping has been examined, which is ideal from point of view of laser scalability to higher power levels. In the computations, spectroscopic parameters of aprotic solution having an Nd3+ ion concentration of 0.3 M have been considered and numerical calculations were performed for analyzing the effect of various parameters including; active ion concentration, gain medium length, absorption depth, output coupler transmission and input pump power on laser output and efficiency. The results indicate that nearly 1.5 kW laser output may be obtained for an input pump power of 5.0 kW with a slope efficiency of nearly 31% having a threshold pump power requirement of 300 W for a given cell length of 15 cm. Hence, a set of optimized parameters have been obtained for designing an efficient transversely diode pumped kW level flowing liquid laser.

Overview of Optical Techniques for Characterization of High-Power Infrared Gas Lasers

High-power lasers typically form a multidisciplinary technological area laced with innumerable challenges in its realization as a practical system. The prime amongst them are infrared gas laser sources, such as carbon dioxide gas dynamic laser, hydrogen fluoride, deuterium fluoride laser, and chemical oxygen iodine laser. Each of these laser systems is associated with a unique as well as complex active medium environment involving intense interaction between lasing and pumping species under specific gas dynamic conditions. The parameters viz., specie concentration of the lasing, pumping mediums and other by-products, medium homogeneity, individual constituent gas flow rate, pressure and temperature at critical locations, and cavity Mach number are very crucial in determining the output of the gas laser system. It is essential to determine these parameters nonintrusively, with necessary precision so as to optimize these lasers especially in case of large-scale systems. Thus, the focus of this paper is to review and discuss the existing applicable optical detection methodologies ranging from the more established methods, such as optical absorption/emission spectroscopy, to very contemporary, such as Raman spectroscopy, cavity ring down spectroscopy, laser-induced fluorescence/planer laser-induced fluorescence, and so on, which are relevant for the diagnostic needs of gas lasers.

Data acquisition system for flowing gas lasers

The present paper describes a dedicated data acquisition system (DAS) for gas lasers in general and for chemical oxygen iodine laser (COIL) in particular. The developed DAS is a PC based 170-channel system using PCI bus and RS 485 serial communication for fast and slow data handling respectively. It comprises of Advantech PCI 1716 multi function data acquisition board and RS 485 based ADAM modules. It also includes custom built interface electronics circuits for sensors/actuators and optical diagnostics for gas concentration measurement. The application software is developed using VC++ programming language with six graphical user interfaces for facilitating single person operation.