Sensors and Measurement Techniques for Chemical Gas Lasers Mainuddin Gaurav Singhal A. L. Dawar Sensors and Measurement Techniques for Chemical Gas Lasers International Frequency Sensor Association Publishing, S. L. Mainuddin, Gaurav Singhal, A. L. Dawar Sensors and Measurement Techniques for Chemical Gas Lasers Copyright © 2014 by IFSA Publishing, S. L. E-mail (for orders and customer service enquires): [email protected] Visit our Home Page on http://www.sensorsportal.com All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (International Frequency Sensor Association Publishing, Barcelona, Spain). Neither the authors nor International Frequency Sensor Association Publishing accept any responsibility or liability for loss or damage occasioned to any person or property through using the material, instructions, methods or ideas contained herein, or acting or refraining from acting as a result of such use. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identifies as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. ISBN-13: 978-84-617-1865-8 ISBN-10: 84-617-1865-8 BN-20140711-AA BIC: TJFC Contents Contents Preface ............................................................................................................ 9 Contributors.................................................................................................. 13 1. Overview of Chemical Lasers: Sensors and Measurement Needs ........ 15 Historical Perspective ................................................................................ 15 1.1 Hydrogen Fluoride/ Deuterium Fluoride Laser ................................... 19 1.2 Chemical Oxygen Iodine Laser ............................................................ 22 1.3 CO2 Gas dynamic Laser ....................................................................... 26 1.4 Sensors and Measurement Needs ......................................................... 30 References .................................................................................................. 33 2. Direct Sensors: Types and Selection........................................................ 37 2.1 Sensor Fundamentals ........................................................................... 38 2.1.1 General Classification ................................................................... 39 2.1.2 Transducer Characteristics ............................................................ 40 2.2 Temperature Sensors ............................................................................ 41 2.2.1 Thermocouples.............................................................................. 42 2.2.2 Resistance Temperature Detectors (RTDs)................................... 45 2.2.3 Thermistors ................................................................................... 46 2.2.4 Integrated Circuits (ICs) Temperature Sensors ............................. 47 2.2.5 Infrared/Optical Pyrometers.......................................................... 50 2.3 Selection of Temperature Sensors ........................................................ 51 2.4 Pressure Sensors .................................................................................. 52 2.4.1 Capacitance Sensors...................................................................... 53 2.4.2 Strain Gauge Sensors .................................................................... 56 2.4.3 Tenso-resistive Type (Piezoresistive Strain Gauge) Sensors ........ 57 2.5 Selection of Pressure Sensors............................................................... 59 2.6 Level Sensors ...................................................................................... 60 2.6.1 Hydrostatic (Differential) Pressure Based Liquid Level Sensor ... 61 2.6.2 RF Capacitance Liquid Level Sensors .......................................... 62 2.6.3 Ultra Sonic and Sonic Liquid Level Sensors................................. 63 5 Sensors and Measurement Techniques for Chemical Gas Lasers 2.7 Selection of Level Sensors .................................................................... 65 2.8 Flow Sensors 67 2.8.1 Positive Displacement Flow Meters.............................................. 68 2.8.2 Velocity Flow Meters.................................................................... 68 2.8.3 Mass Flow Meters......................................................................... 68 2.8.4 Differential Flow Meters............................................................... 69 2.9 Selection of Flow Sensors..................................................................... 70 2.10 Optical Sensors................................................................................... 76 2.10.1 Thermal Detectors....................................................................... 76 2.10.1.1 Thermocouples / Thermopiles ............................................. 76 2.10.1.2 Pyroelectric Detectors.......................................................... 77 2.10.1.3 Thermistors / Bolometers..................................................... 77 2.10.2 Photon Detectors......................................................................... 78 2.10.2.1 Silicon/Germanium Detectors.............................................. 79 2.10.2.2 Mct Detectors....................................................................... 79 2.10.2.3 Indium Antimonide (InSb)................................................... 79 2.10.2.4 Ternary Compounds Detectors ............................................ 80 2.10.2.5 Alternate Indium Antimonide Detectors.............................. 80 2.10.2.6 Platinum Silicide (PtSi) Detectors ....................................... 81 2.11 Selection of Optical Sensors............................................................... 81 References .................................................................................................. 83 3. Diagnostic Techniques.............................................................................. 87 3.1 Specie Concentration Measurement..................................................... 88 3.1.1 Optical Emission........................................................................... 90 3.1.1.1 Singlet Oxygen Yield............................................................. 91 3.1.1.2 Water Vapor Concentration................................................... 93 3.1.2 Optical Absorption........................................................................ 95 3.1.2.1 Chlorine Utilization (Cl2) Concentration .............................. 98 3.1.2.2 Sulphur Hexafluoride (SF6) Concentration ........................... 99 3.1.2.3 Iodine (I2) Concentration..................................................... 100 3.1.3 Diode Laser based Absorption Spectroscopy.............................. 101 3.1.4 Raman Spectroscopy................................................................... 102 3.1.5 Cavity Ring Down Spectroscopy (CRDS) for Trace Detection of Gases.................................................................................................... 105 3.2 Cavity Medium Characterization ....................................................... 107 3.2.1 Small Signal Gain (SSG) Measurement...................................... 108 3.2.1.1 Probe Beam Method ............................................................ 108 3.2.1.2 Voigt Profile Method........................................................... 110 3.2.2 Mach Number Diagnostics.......................................................... 113 3.2.2.1 Pitot Static Tube Method ..................................................... 113 3.2.2.2 Laser Doppler Velocimetry (LDV)...................................... 115 6 Contents 3.2.2.3 Voigt Profile Method........................................................... 117 3.2.3 Medium Homogeneity................................................................. 118 3.2.3.1 Gain Mapping ...................................................................... 119 3.2.3.2 Optical Interferometer.......................................................... 120 3.2.3.3 Laser Induced Fluorescence (LIF) / Planar-LIF (PLIF)....... 122 3.3 Laser Output Power and Pulse Shape Measurement ......................... 125 3.4 Selection of Diagnostic Techniques.................................................... 128 References ................................................................................................ 129 4. Signal Conditioning ................................................................................ 133 4.1 Signal Sources .................................................................................... 133 4.1.1 Grounded Signal Sources............................................................ 134 4.1.2 Floating Signal Sources............................................................... 134 4.1.3 Single-ended Measurement......................................................... 135 4.1.4 Differential-ended Measurement................................................. 136 4.2 Analog and Digital Signals................................................................. 136 4.2.1 Operating Voltage and Output Signal Selection ......................... 137 4.3 Sensor Circuits for Signal Conditioning............................................. 138 4.3.1 Wheatstone Bridge.....................................................................