Articoli correlati a Total and Partial Pressure Measurement in Vacuum Systems
Sinossi
This book deals with the underlying theory and practical aspects of pressure gauges that are at present in general use. Because of the ever-increasing demands to provide a wider range of sophisticated and reliable vacuum equipment a good understanding of these instruments is of vital importance to all workers in the research and industrial sectors. Of the gauges considered only the mechanical types are absolute, in the sense that they measure pressure directly as a force upon a liquid column or a solid surface. Under ideal conditions it is possible to calculate their sensitiv- ities, which are the same for all gases and vapours. The recent developments in the viscous or molecular damping gauges indicate that these may also be considered absolute. Other gauges are indirect in that they involve the measurement of some secondary phenomenon which is pressure-dependent and therefore these gauges can only be used for measurement after calibration against an absolute standard. The radiometer or Knudsen type gauge has been excluded from the text since these are now only of historic interest. Also no mention is made of the integration techniques involving surface changes (such as work function) although these could have application under very special circumstances. The McLeod gauge is dealt with in some detail, for even though this gauge has few practical applications, it is the most sensitive absolute gauge available and has value as a reference standard.
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Contenuti
1 Mechanical manometers.- 1.1 Liquid manometers.- 1.2 The McLeod gauge.- 1.3 The diaphragm manometer.- 1.4 Viscous or friction-type gauges.- References.- 2 Thermal conductivity gauges.- 2.1 Basic principles.- 2.2 Measurement of thermal conductivity.- 2.3 Sensitivity.- 2.4 End losses.- 2.5 Accommodation coefficient and relative sensitivity.- 2.6 Alternative methods of bridge control.- 2.7 Useful range of the constant-voltage bridge.- 2.8 The lower limit to the useful pressure range.- 2.9 The importance of bridge-voltage and temperature fluctuations at high pressure.- 2.10 Compensation for temperature and voltage fluctuations.- 2.11 Physical changes in the gauge wire (ageing effects).- 2.12 Extension of working range to atmospheric pressure.- 2.13 Commercial gauges for laboratory and industrial use.- 2.14 The thermocouple gauge.- References.- 3 Thermionic cathode ionization gauges.- 3.1 Positive ion production in a gas.- 3.2 The principle of the thermionic cathode ionization gauge.- 3.3 The relative sensitivity for different gases.- 3.4 The measurement of low pressures.- 3.5 Extension of the range of the BA gauge to very low pressures.- 3.6 The precision to which measurements can be made with the hot cathode gauge.- 3.7 Gauges specially designed to operate at high pressure.- 3.8 Chemical and physical reactions in the hot cathode ionization gauge.- References.- 4 Cold-cathode ionization gauges.- 4.1 The development of cold-cathode (crossed-field) gauges.- 4.2 Commercial gauges for high- and ultra-high vacuum applications.- References.- 5 Gauge calibration.- 5.1 Basic considerations.- 5.2 Calibration against the transfer gauge.- 5.3 Comparison with absolute gauges.- 5.4 Series expansion techniques.- 5.5 Dynamic flow techniques.- 5.6 The measurement of gas throughput.- References.- 6 Gas analysis in vacuum systems: magnetic, crossed-field and time-of-flight analysers.- 6.1 Introduction.- 6.2 The magnetic deflection mass spectrometer.- 6.3 The trochoidal (or cycloidal) mass spectrometer.- 6.4 The omegatron.- 6.5 Time-of-flight (TOF) mass spectrometer.- 6.6 Interpretation of mass spectra.- References.- 7 Gas analysis in vacuum systems: quadrupole mass analysers.- 7.1 Introduction.- 7.2 Principles of the quadrupole mass filter.- 7.3 Design of small residual gas analysers (RGAs).- 7.4 The operating characteristics of the RGAs designed for general laboratory and industrial use.- 7.5 The use of electron multipliers for signal detection.- 7.6 Non-conventional methods of quadrupole operation.- 7.7 The monopole mass spectrometer.- 7.8 The three-dimensional quadrupole ion trap.- References.
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