Saturday, February 26, 2011

Book Review - EMP Radiation and Protective Techniques

Book Review - EMP Radiation and Protective Techniques

EMP Radiation  and Protective Techniques
by LW Ricketts, JE Bridges, J Miletta
A Wiley-Interscience Publication, 1976

1.            Nuclear weapons can have devastating effects. Usually, one thinks only of the blast, thermal, and radiation effects as they relate to the human body. However, considering only these factors ignores some of the other devastating effects. One such effect is that of the nuclear electromagnetic    pulse   (EMP).   The   effects   of   the   nuclear electromagnetic pulse must be considered and calculated when preparing for a nuclear war.

2.            Electromagnetic Pulse (EMP) is now recognised as one of the most important nuclear weapon threats. EMP from a weapon detonated many hundreds, even thousands, of kilometres away is capable of disrupting or damaging electronic equipment, especially modern digitally controlled systems. Equally important, in many cases EMP is not accompanied by any other prompt nuclear weapon output. These conclusions are supported by a considerable number of data developed from both sophisticated analyses and non-nuclear-threat-level experiments on electronic equipment.

3.            The importance of EMP is now clearly established, and a considerable amount of information is appearing in the open literature. Much of this information, however, is processed exclusively on a single topic and often does not address problems that are of immediate concern. Moreover so much “good” information has now become available that it is often impossible to extract the essentials and lay out a meaningful hardening program.

4.         The book shows how quantitative data on EMP pickup, component susceptibility, and hardening performance can be developed and integrated into EMP hardening requirements for specific electronic components or subsystems. These hardening requirements can be stated in a form (in terms of EMP pickup currents and voltages) readily understandable by various system design specialists. The book also describes the management aspects necessary for long term EMP hardening.

5.         The author has summarised information on hardening allocation in such a simple language that it can be understood even by the reader having nil experience in the field. This first involves identification of threat, the related EMP environment, and then the EMP pickup. The pickup is compared with the susceptibility to determine the total isolation required, which is then allocated to specific components of the system. The hardening isolation required can be reduced by proper component and system design. Laboratory methods similar to many existing procedures for EMC (electromagnetic compatibility) and RFI (radio-frequency interference) can be employed to confirm these analyses.

6.         The book is divided into three parts. Each part is further divided into chapters which cover specific topics. The author has definitely put in hard work and has covered a broad spectrum of the subject. Each chapter covers the related topics in great detail.

7.         In Part I EMP Environment and Pickup are nicely covered in two chapters. In chapter 1 the author discusses the EMP environment from a system and trade-off viewpoint. Twelve environments of significance are identified that may affect the various system design or operational mode options, and are explained with the help of a diagram. Further Near-Surface Burst, Mid-Altitude Burst and Exoatmospheric Burst are explained in detail with the help of figures and mathematical expressions. The author has covered the topics in such a way that even beginners can draw fruitful lessons from the text and other means used. Chapter 2 deals with the conversion of the EMP environment into currents and voltages that may be applied to sensitive components. This helps to give a means to the reader to understand as to how we can measure EMP in terms of quantities such as current, voltage and energy. Examples of results from calculations which are included, definitely enables the reader to obtain a feeling for the type of EMP pickup likely to be encountered. Similarly approximate formulas are presented that characterize the pickup in terms of a single lumped parameter circuit or Thevenin’s equivalent generator.

8.         Part II covers the Behaviour of Components and Subsystems. A large amount of data is tabulated in this part and also in Appendix B which covers the susceptibility tables. In chapter 3 the susceptibility on a quantitative basis of typical electronic parts, such as transistors, resistors and capacitors is discussed at length by the author. Although electronic components can be acted on directly by an EMP, the main threat to electrical components is the induced transients generated by EMP-system interaction. The chapter deals with the effects of short-duration electrical transients on electronic components. The prime attention is given to the failure thresholds of components, with emphasis on semiconductor devices. The electrical response of components to high-level transients is also discussed. All this is discussed with the help of well described graphs, diagrams and mathematical equations, which further helps the reader to understand the issue in an efficient manner. Chapter 4 deals with numerous formulas and other data that permit estimating the performance of various hardening components such as envelope shields, cable and connector shields, baluns, filters, surge arresters, transformers, chokes, disconnects, spark gaps, zener diodes and varistors. This chapter also tells how to calculate the hardening or shielding effectiveness of the various protective techniques and devices. Chapter 5 gives an insight to the practical aspects of the techniques described in chapter 4. The author has covered as to how to conduct the various laboratory test procedures required to evaluate the effectiveness of shields, vents, gaskets, cables, connectors, filters, surge arresters and chokes. This chapter shows how to setup and how to perform the various test procedures in the lab. The diagrammatic description of each procedure can be used to conduct these tests in the lab.

9.         Part III of the book gives an insight in to the System Aspects. Chapter 6 presents the management aspects of EMP hardening with emphasis on quality assurance. It also covers numerous system design aspects, including operational upset control, harmonising EMP, lighting and RFI requirements, and the development of a grounding and cabling plan. The chapter covers EMP hardening management, EMP control plan, design and development, maintenance and operations and monitoring of operational systems. The chapter also covers EMI, EMC, RFI, EMR, HERO and RADHAZ in brief. Shielding and Susceptibility Zoning Approaches, System Aspects of Damage Protection and System Aspects of Upset Protection are also covered. In Chapter 7 the author has nicely discussed one method of developing hardening allocations-specifying quantitative performance requirements for components and subsystems. The author has nicely addressed how hardening allocation approach may involve breaking the system up into various subsystems. Then the EMP hardening performance requirements are applied in a specific and quantitative way to each of these elements. This chapter also covers Buried Facility Allocations, Mobile Shielded Van Allocations and Aircraft Allocations which gives an adequate exposure to the reader.

10.       Apart from these seven chapters the author has also provided three appendices, which prove quite helpful. Appendix A contains a Glossary of Relevant Terms so that the reader can get a quick reference to various terms used in different chapters. Appendix B gives the various Susceptibility Tables, which contains susceptibility data on electronic circuits and components. Appendix C covers the various Simulation Facilities. 

11.       The book covers the activity relating to the susceptibility of electronic components and circuits used in electronic or electrical systems to the EMP environment or, more specifically, to the effects of transient voltages and currents that result from EMP energy being coupled into cables, antennas, power distribution systems, and other conductive structures. Particular emphasis has been given by the author to the margin of tolerance in the specifications of a device, circuit or subsystem. This can be a very important consideration in evaluating the degradation in the EMP environment.

12.       The book describes each topic adequately with the help of graphs, diagrams and mathematical expressions which will definitely be helpful for persons working in the field of EMP. Certain topics such as effects of EMP radiations on human body could also have been touched upon. The book also gives an exhaustive list of references and with the bibliography provided one can easily go out and enhance his knowledge of the subject.

Reviewed by one of my students Vikas Agnihotri

No comments: