MODERN VACUUM PRACTICE – Book Reviews


3rd Edition Reviews


(1) by Eur Ing Eur Phys Dr Steve Hoath, ADPhil Ltd, Cambridge, UK

This third Edition of the widely used and valuable book for engineers, technicians and students in the vacuum community contains enough to warrant a purchase even to those still using earlier editions. The fully revised sections and new material now included, such as measurement unit conversion graphs and questions and answers, have extended the scope of the book without changing the book’s emphasis on clear line drawings and photographs, with some concise descriptions to help get the technical messages across.
Practice is an important key-word: the trouble-shooting tables provide excellent guides, which means that the reader finds that they can solve issues they face very effectively. As a user of the earlier edition, I have found the lack of equations was rarely a drawback, because the book succeeds in painting a good picture of what is happening (or should be).


The new sections on vacuum applications, chemical pumping and the much expanded section on helium mass spectrometer leak detection are very welcome additions to Modern Vacuum Practice, and thereby give the book an even more industrial flavour. There is also an important element of education about safety issues throughout the text, which of course extends to all vacuum users and importantly new workers in the field.

 

I personally would have liked to see even more modern items included as well, such as mass flow controller and moisture sensor, and some more semiconductor related system examples, but such limits can always be overcome via the author’s website links. Nigel Harris is, once again, to be congratulated on a really significant achievement, and I will not hesitate to recommend your purchase of a Modern Vacuum Practice, 3rd Edition.


 
(2) by Austin Chambers. Honorary Fellow, Department of Physics, University of York, UK

Aimed at technical staff, engineers and scientists in laboratory and industrial environments, this is a new and fully revised edition of a book already highly regarded in its earlier versions. It is considerably enlarged, reflecting developments in the technology and its application in the last decade, and the introduction of some new features in its format that will enhance its value to the reader. The text is the outcome of the author's large experience in teaching the subject as Corporate Technical Training Manager at BOC Edwards, and his extensive knowledge of the many sectors of industry where vacuum technology is applied. The style of writing is direct and informative, backed up by the use of clear, well chosen diagrams.


Three introductory chapters prepare the reader for the substantial middle part of the book which describes the gauging and pumps by which vacua are measured, characterised and produced. This is followed by descriptions of the additional hardware - vacuum components and valves - from which whole systems are made and leads naturally to the consideration of system design. Applications in the diverse and important subject of chemical processing are described. Chapters on leak detection and safety concerns, followed by a 'question and answer' section, a bibliography and various appendices, bring the book to a conclusion.


As with the earlier versions the author has designed a path through the subject that does not employ the traditional mathematically rendered introduction to gas behaviour and other matters. It is an appropriate route that presents the essential concepts and quantities involved effectively, with good examples to which the reader can easily relate. Basic terms and units are clearly defined and numerical conventions and practices properly discussed. The inclusion of a table of significant dates in the history of the subject is a feature not only useful for reference but also with motivational value - conveying a sense of the role of this technology as a significant factor in general technological progress. The motivational aspect continues in chapter 2 in which the applications of vacuum are surveyed. A selection of them is discussed, in particular the methods and uses of vacuum coating for a wide range of consumer products, for example compact discs and architectural glass. Other applications, especially its importance in the semiconductor industry, emphasise the breadth of its role. Relevant physical concepts are the subject of the next relatively short chapter which deals with gases, vapours and related matters, the processes occurring at the surfaces that form the vacuum boundary, measures of flow and the molecular behaviour of gases. Figure 3.5, which relates pressure, number density, mean free path and monolayer formation time over the various ranges of vacuum is an excellent source of information and could perhaps have been more exploited qualitatively at this stage with benefit to later discussions, but this is a small criticism.


At this point we reach the main subject matter of the book - the knowledge and understanding that underlies the practical means of creating, measuring and characterising a vacuum for a range of modem purposes that involve low to ultra-high vacuum. The chapters on vacuum gauges and gas identification are thoroughgoing and informative, with basic terminology defined, and the concept of active gauging introduced prior to a description of the various gauges in common use. How these work, their range, accuracy, operational 'do's and don'ts’ and suitability for particular purposes are dealt with in a way that should give the user confidence to operate them properly, with a good understanding of the significance of their readings, and a good basis of knowledge on which to choose a gauge for a particular purpose. Summarising tables reinforce the text. The chapter on gas identification, as well as describing the instruments available, has a discussion of the qualitative interpretation of spectra, which contains a useful table on possible sources of the more common individual components of the residual gas.


The treatment of pumps is especially valuable and informative. Each principal type gets a chapter on its own. Oil-sealed rotary pumps, nowadays displaced to some extent by dry pumps, are still widely used in scores of applications. Their workings, oil preferences, accessories, performance and occasional maladies are dealt with in a way that is very helpful to the user. In semiconductor applications, the harsh conditions required for the handling of, for example, corrosive gases and gas-borne particulates proved very problematical for oil-sealed pumps and were a strong incentive to the development of oil-free pumps, or 'dry pumps,' as they are usually called. These are now used increasingly in a number of other applications, including those that require clean conditions uncontaminated by oil vapours, and the chapter devoted to them in a similar way gives describes the different types available, their characteristics, application, and operational concerns that arise. The development of these pumps has been one of the significant trends of recent years and it is good to have the authors succinct discussion.


Pumps for high and ultra high vacuum - the diffusion pump and its accessories, turbomolecular pumps, their drag stages, cryopumps, and sorption and getter pumps are similarly treated in a way that explains their construction, action, performance, special requirements and matters of operational good practice. Maintenance and safety issues are dealt with and, most usefully, troubleshooting procedures for under-achieving systems. Summaries at the end of each chapter mean that comparisons between them can be made in considering the choice of pump for a particular purpose.


The range of components and valves available is described with the aid of good diagrams and essential information about sizes, applications and the properties of vacuum compatible materials of construction and cleaning procedures. A chapter devoted to considerations in system design introduces the concept of conductance and the important effective pumping speed formula is derived. The changing nature of gas flow as pressure falls is discussed, though in quoting a pressure for the onset of molecular flow at a pressure below 10-3 mbar, a 50mm pipe size is implied, but not stated. Consistently with this, the 1mbar entries along the top line of figure 13.1 would be 0.1 mbar. Numerical examples of the use of conductance formulas, and the calculation of pumping speeds, outgassing loads and pressures achieved are given. The pump-down time formula is presented and discussed. A new feature, saving the labour of calculation, is the inclusion of easily used nomograms for determining molecular flow conductance of pipes, pump-down times and pressures achieved, once values of dimensions, pumping speeds and outgassing rates are assumed.


Aside from its general interest, the chapter on the use of vacuum in chemical processing will be of considerable value to practitioners in that field. A thorough treatment of methods of leak detection in a book with this title is of course essential, and similarly strong guidance on the safe use of equipment. Both these subjects are addressed with authority in the final chapters. The book closes with various appendices, a good bibliography and index, and - a particularly valuable feature - a set of 90 short 'questions and answers' that range over the subject matter, to test and reinforce the learning.


All in all this is a fine text that fulfils its aims. With its broad scope and detailed up-to-date information it is very good value for money and deserves a wide readership.

 

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