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Accelerators and storage rings
Nuclear I n s t r u m e n t s and Methods 171 (1980) 627 © North-Holland Publishing C o m p a n y
628
BOOK REVIEWS C.L. Olsen and U. Schumacher, Collective ion Acceleration, Springer Tracts in Modern Physics 84 (ed. G. H6hler; Springer-Verlag, Berlin, Heidelberg, 1979).
Collective methods o f acceleration (eds. N. Rostoker and M. Reiser);Accelerators and Storage rings, Vol. 2 (eds. J.P. Blewett and F.T. Cole; Harwood, New York, 1979). These two books, on the same subject, are very different in character and are quite complementary. The first is a m o n o g r a p h suitable for those wishing for the first time to learn a b o u t collective acceleration or for those workers in the field who wish either to broaden their understanding or have on their desk a compilation of basic ideas and concepts along with a very comprehensive list of references. The second is a collection of the papers presented at the 3rd International Conference on Collective methods o f acceleration (University of California at Irvine, May 1978) and conrains forty-two separate contributions which, together, describe the cutting-edge o f research in the field as of that date and, reasonably accurately, as of early 1980. Collective acceleration is the use of the self-fields (electric and/or magnetic) of collections of charges to focus and/or accelerate particles. Usually the "charge" is created by electrons and the "particles" are ions. The consequences o f the self-fields of accelerated particles was first appreciated decades ago and has been the subject of intensive analysis during the last twenty years. Most of this effort has been directed towards avoiding the undesired consequences of these self-fields and the work is often categorized as evaluating "space charge limits" on the performance o f conventional accelerators and storage rings. In collective acceleration one seeks to turn these self-fields to a useful purpose. The self-fields of changes can be very large and therein lies the incentive for investigation o f the subject for it is conceivable that one could achieve, collectively, fields far b e y o n d the limit of laboratory-produced fields (limited, for example, by high-voltage breakdown or the critical fields of superconductors) and hence greatly reduce the cost and size of particle accelerators. The use of collective fields for acceleration was first proposed, in 1951, by Harvie. Alfven and Weinholm, in 1952, independently proposed the idea and actually a t t e m p t e d an experimental d e m o n s t r a t i o n (which failed). But it was at the first international conference on accelerators, at CERN in 1956, that three seminal papers, on collective (and coherent) acceleration, by Budker, Veksler and Fainberg, really caught the attention o f workers t h r o u g h o u t the world. (Two of these papers are reprinted in the Rostoker and Reiser book, which book is - most appropriately - dedicated to the late G.I. Budker.) The particular approach o f an electron ring accelerator was first a n n o u n c e d by Veksler et al. in 1967, and subsequently m u c h work, in m a n y countries, has been p u t into this device. (See the reprint in the Rostoker and Reiser book, which there is incorrectly dated as 1956.) So m u c h for general and histrical c o m m e n t s . Readers
desiring more information (and there is a great deal more!) would do well to turn to the Olsen and Schumacher book. In the first half of this book, Olsen gives a comprehensive discussion of the acceleration of ions by intense electron beams. Although early work was done by Plyutto, it was the discovery, in 1968, by Graybill and Uglum that an intense electron beam injected into a neutral gas produced ions of energies greater than the electron energy - and travelling up-gradient; i.e., in the direction o f the electron - that really started this field of endeavor. Subsequently there has been m u c h experimental work, which is carefully described and comprehensively referenced by Olsen. The explanation o f the p h e n o m e n a has challenged m a n y theorists and there are a n u m b e r o f models which have been put forth through the years. Olsen discusses these theories in fair detail and firmly concludes that the "OIsen t h e o r y " is the correct theory. It is not clear to this reviewer what exactly is the "Olsen theory". It seems to be defined, implicitly, as a proper evaluation of all relevant physical p h e n o m e n a associated with an electrostatic acceleration mechanism. However, I wish to emphasize that the reader is presented with sufficient details of the experiments and theories to form his own j u d g e m e n t s concerning the significance of the contributions of various workers, and the validity of diverse models. Finally, in a very stimulating section, Olsen presents some thirty-seven concepts (!) for extending the use of the strong collective fields in intense relativistic electron beams ( ~ 1 0 0 MV/m) to large distances so as to obtain more than present energies ( ~ 1 0 MeV/nucleon for H, He, and N). Of course the success of these concepts depends upon a correct understanding o f the physics as well as overcoming the problems associated with realization of the device and it will be m o s t interesting to see which - if any - of these proposals will result in practical accelerators. In the second half of the Olsen and Schumacher book, Schumacher gives a comprehensive - and most readable discourse on electron ring accelerators. This field was pioneered by Veksler and his co-workers, b u t after 1967 received theoretical and experimental effort in m a n y laboratories t h r o u g h o u t the world. Unfortunately, the only laboratory presently active in electron ring accelerator research is Dubna, where Sarantsev leads the group which Veksler created, in the early sixties, to work on electron rings. The electron ring accelerator is a particularly simple collective accelerator. The collective electric field is formed by a very thin (bicycle tire) ring o f relativistic electrons. After formation, the ring is partially neutralized by ions and then accelerated (for example, by a slightly decreasing 627
628
Book Reviews
magnetic field) thus dragging along the ions. Because the configuration is simple, the understanding is considerable and Schumacher goes through the extensive theoretical work in a careful, interesting, pedagogically sound, and comprehensive manner. Also, Schumacher reviews the many proposals which are variations on the basic concept. In his final section, Schumacher describes in some detail the experimental programs on electron ring accelerators. Of particular interest are those at Garching and Dubna where ions have been successfully accelerated, b u t only to a rather modest energy ( ~ 2 MeV/nucleon for N). In fact, it is the complexity and sensitivity of the electron ring a c c e l e r a t o r despite the fact that it has been d e m o n s t r a t e d to be workable - w h i c h has led to the present termination of almost all development work. It has appeared to m a n y that the approach has no advantages over conventional accelerators, b u t readers are urged to read S c h u m a c h e r ' s a r t i c l e - where an impressive body of understanding and technical accomplishment is described - and then form their own opinion. The conference proceedings, edited by Rostoker and Reiser, cover the whole field of collective acceleration. Consequently, the volume is m u c h more comprehensive than the Olsen and Schumacher m o n o g r a p h ; aspects of collective acceleration not even m e n t i o n e d in the m o n o g r a p h receive whole sections of this book. Those particularly interested in acceleration by intense electron b e a m s or electron ring accelerators will find sections on these two approaches, b u t because they are covered more completely in the m o n o g r a p h it is r e c o m m e n d e d that those so interested read the m o n o graph. A n y collection of papers from a conference inevitably suf%rs from well-known defects which need not be detailed here. On the other hand, the present collection presents the reader with a very good survey of the present state of the field. Of particular interest are those papers in fields not
covered by the monograph. There is a whole section on wave acceleration, which d e m a n d s attention, for this is an approach which currently is receiving m u c h theoretical and experimental effort. In the scheme proposed and being pursued by D r u m m o n d a collective eigenmode on an electron b e a m (the Doppler-shifted cyclotron mode) is stimulated to grow, controlled in amplitude and velocity, and employed to accelerate ions. Naturally, there are many aspects of this scheme which need study and the papers on the D r u m m o n d proposal go into considerable detail and hence are most interesting. A n o t h e r most interesting part of the book is the section on new problems and concepts. Here, amongst other mindstretching ideas, the reader will find a description of Rostoker's collective focusing accelerator. In this device, which is currently under laboratory investigation, a toroidal ring of electrons is employed to electrostatically hold and focus ions thus eliminating the need for large external magnetic fields. The ions are accelerated by conventional rf induction fields while magnetic mirrors prevent the electrons from being simultaneously accelerated by the rf fields. The monograph, of Olsen and Schumacher, is a comprehensive discussion of the two major types of collective accelerators (that is, the two that have actually, to date, achieved the acceleration of ions) and the proceedings, of Rostoker and Reiser, presents in m a n y contributions a survey of the whole field. But this field has not produced a single practical accelerator. Yet the promise is there. To those interested in the promise, which may or may not materialize into reality in the future, or to those interested in a great deal of very good physics, often combining some of the most sophisticated concepts and techniques of accelerator physics and plasma physics, this reviewer can, and does, r e c o m m e n d these two books. ANDREW M. SESSLER
Status and prospects o f thermal breeders and their effect on luel utilization, IAEA Techn. Report Series No. 195 (1979). Beside summarizing ably the status of thermal breeders the book is very timely and welcome to reactivate more systematic considerations of potentially available nuclear power options and to open the eyes for the m a n y neglected future i m p r o v e m e n t s available in the nuclear power technology when the antai technology and antai nuclear m o v e m e n t s have frozen the discussion about nuclear power to essentially present day light water reactors that represent only a first product of this broad new technology. The book is well organized and easy to follow. It explains the importance and benefits of pushing ahead with near breeders and h o w the thermal versions c o m p l e m e n t on the t h o r i u m fuel cycle the fast breeders on the u r a n i u m cycle. It also indicates the smaller environmental impacts and
advantageous safety features of these reactors. Restricting itself to the CANDU-Th, light water, molten salt and heavy water suspension breeders or near breeders the book makes no m e n t i o n of other potential solutions such as accelerator (spallation) breeding or gas-core reactors with very low fissile inventories which could be made available in time to solve a more severe u r a n i u m shortage crisis. In the valuable comparative strategy studies of various reactor combinations the book does include one high temperature reactor case and one fast breeder (LMFBR) case along side with the systems treated in the book while other promising i m p o r t a n t H T R and the very promising gas-cooled fast breeder (GCFR) cases are n o t mentioned. REINO EKHOLM
628
BOOK REVIEWS C.L. Olsen and U. Schumacher, Collective ion Acceleration, Springer Tracts in Modern Physics 84 (ed. G. H6hler; Springer-Verlag, Berlin, Heidelberg, 1979).
Collective methods o f acceleration (eds. N. Rostoker and M. Reiser);Accelerators and Storage rings, Vol. 2 (eds. J.P. Blewett and F.T. Cole; Harwood, New York, 1979). These two books, on the same subject, are very different in character and are quite complementary. The first is a m o n o g r a p h suitable for those wishing for the first time to learn a b o u t collective acceleration or for those workers in the field who wish either to broaden their understanding or have on their desk a compilation of basic ideas and concepts along with a very comprehensive list of references. The second is a collection of the papers presented at the 3rd International Conference on Collective methods o f acceleration (University of California at Irvine, May 1978) and conrains forty-two separate contributions which, together, describe the cutting-edge o f research in the field as of that date and, reasonably accurately, as of early 1980. Collective acceleration is the use of the self-fields (electric and/or magnetic) of collections of charges to focus and/or accelerate particles. Usually the "charge" is created by electrons and the "particles" are ions. The consequences o f the self-fields of accelerated particles was first appreciated decades ago and has been the subject of intensive analysis during the last twenty years. Most of this effort has been directed towards avoiding the undesired consequences of these self-fields and the work is often categorized as evaluating "space charge limits" on the performance o f conventional accelerators and storage rings. In collective acceleration one seeks to turn these self-fields to a useful purpose. The self-fields of changes can be very large and therein lies the incentive for investigation o f the subject for it is conceivable that one could achieve, collectively, fields far b e y o n d the limit of laboratory-produced fields (limited, for example, by high-voltage breakdown or the critical fields of superconductors) and hence greatly reduce the cost and size of particle accelerators. The use of collective fields for acceleration was first proposed, in 1951, by Harvie. Alfven and Weinholm, in 1952, independently proposed the idea and actually a t t e m p t e d an experimental d e m o n s t r a t i o n (which failed). But it was at the first international conference on accelerators, at CERN in 1956, that three seminal papers, on collective (and coherent) acceleration, by Budker, Veksler and Fainberg, really caught the attention o f workers t h r o u g h o u t the world. (Two of these papers are reprinted in the Rostoker and Reiser book, which book is - most appropriately - dedicated to the late G.I. Budker.) The particular approach o f an electron ring accelerator was first a n n o u n c e d by Veksler et al. in 1967, and subsequently m u c h work, in m a n y countries, has been p u t into this device. (See the reprint in the Rostoker and Reiser book, which there is incorrectly dated as 1956.) So m u c h for general and histrical c o m m e n t s . Readers
desiring more information (and there is a great deal more!) would do well to turn to the Olsen and Schumacher book. In the first half of this book, Olsen gives a comprehensive discussion of the acceleration of ions by intense electron beams. Although early work was done by Plyutto, it was the discovery, in 1968, by Graybill and Uglum that an intense electron beam injected into a neutral gas produced ions of energies greater than the electron energy - and travelling up-gradient; i.e., in the direction o f the electron - that really started this field of endeavor. Subsequently there has been m u c h experimental work, which is carefully described and comprehensively referenced by Olsen. The explanation o f the p h e n o m e n a has challenged m a n y theorists and there are a n u m b e r o f models which have been put forth through the years. Olsen discusses these theories in fair detail and firmly concludes that the "OIsen t h e o r y " is the correct theory. It is not clear to this reviewer what exactly is the "Olsen theory". It seems to be defined, implicitly, as a proper evaluation of all relevant physical p h e n o m e n a associated with an electrostatic acceleration mechanism. However, I wish to emphasize that the reader is presented with sufficient details of the experiments and theories to form his own j u d g e m e n t s concerning the significance of the contributions of various workers, and the validity of diverse models. Finally, in a very stimulating section, Olsen presents some thirty-seven concepts (!) for extending the use of the strong collective fields in intense relativistic electron beams ( ~ 1 0 0 MV/m) to large distances so as to obtain more than present energies ( ~ 1 0 MeV/nucleon for H, He, and N). Of course the success of these concepts depends upon a correct understanding o f the physics as well as overcoming the problems associated with realization of the device and it will be m o s t interesting to see which - if any - of these proposals will result in practical accelerators. In the second half of the Olsen and Schumacher book, Schumacher gives a comprehensive - and most readable discourse on electron ring accelerators. This field was pioneered by Veksler and his co-workers, b u t after 1967 received theoretical and experimental effort in m a n y laboratories t h r o u g h o u t the world. Unfortunately, the only laboratory presently active in electron ring accelerator research is Dubna, where Sarantsev leads the group which Veksler created, in the early sixties, to work on electron rings. The electron ring accelerator is a particularly simple collective accelerator. The collective electric field is formed by a very thin (bicycle tire) ring o f relativistic electrons. After formation, the ring is partially neutralized by ions and then accelerated (for example, by a slightly decreasing 627
628
Book Reviews
magnetic field) thus dragging along the ions. Because the configuration is simple, the understanding is considerable and Schumacher goes through the extensive theoretical work in a careful, interesting, pedagogically sound, and comprehensive manner. Also, Schumacher reviews the many proposals which are variations on the basic concept. In his final section, Schumacher describes in some detail the experimental programs on electron ring accelerators. Of particular interest are those at Garching and Dubna where ions have been successfully accelerated, b u t only to a rather modest energy ( ~ 2 MeV/nucleon for N). In fact, it is the complexity and sensitivity of the electron ring a c c e l e r a t o r despite the fact that it has been d e m o n s t r a t e d to be workable - w h i c h has led to the present termination of almost all development work. It has appeared to m a n y that the approach has no advantages over conventional accelerators, b u t readers are urged to read S c h u m a c h e r ' s a r t i c l e - where an impressive body of understanding and technical accomplishment is described - and then form their own opinion. The conference proceedings, edited by Rostoker and Reiser, cover the whole field of collective acceleration. Consequently, the volume is m u c h more comprehensive than the Olsen and Schumacher m o n o g r a p h ; aspects of collective acceleration not even m e n t i o n e d in the m o n o g r a p h receive whole sections of this book. Those particularly interested in acceleration by intense electron b e a m s or electron ring accelerators will find sections on these two approaches, b u t because they are covered more completely in the m o n o g r a p h it is r e c o m m e n d e d that those so interested read the m o n o graph. A n y collection of papers from a conference inevitably suf%rs from well-known defects which need not be detailed here. On the other hand, the present collection presents the reader with a very good survey of the present state of the field. Of particular interest are those papers in fields not
covered by the monograph. There is a whole section on wave acceleration, which d e m a n d s attention, for this is an approach which currently is receiving m u c h theoretical and experimental effort. In the scheme proposed and being pursued by D r u m m o n d a collective eigenmode on an electron b e a m (the Doppler-shifted cyclotron mode) is stimulated to grow, controlled in amplitude and velocity, and employed to accelerate ions. Naturally, there are many aspects of this scheme which need study and the papers on the D r u m m o n d proposal go into considerable detail and hence are most interesting. A n o t h e r most interesting part of the book is the section on new problems and concepts. Here, amongst other mindstretching ideas, the reader will find a description of Rostoker's collective focusing accelerator. In this device, which is currently under laboratory investigation, a toroidal ring of electrons is employed to electrostatically hold and focus ions thus eliminating the need for large external magnetic fields. The ions are accelerated by conventional rf induction fields while magnetic mirrors prevent the electrons from being simultaneously accelerated by the rf fields. The monograph, of Olsen and Schumacher, is a comprehensive discussion of the two major types of collective accelerators (that is, the two that have actually, to date, achieved the acceleration of ions) and the proceedings, of Rostoker and Reiser, presents in m a n y contributions a survey of the whole field. But this field has not produced a single practical accelerator. Yet the promise is there. To those interested in the promise, which may or may not materialize into reality in the future, or to those interested in a great deal of very good physics, often combining some of the most sophisticated concepts and techniques of accelerator physics and plasma physics, this reviewer can, and does, r e c o m m e n d these two books. ANDREW M. SESSLER
Status and prospects o f thermal breeders and their effect on luel utilization, IAEA Techn. Report Series No. 195 (1979). Beside summarizing ably the status of thermal breeders the book is very timely and welcome to reactivate more systematic considerations of potentially available nuclear power options and to open the eyes for the m a n y neglected future i m p r o v e m e n t s available in the nuclear power technology when the antai technology and antai nuclear m o v e m e n t s have frozen the discussion about nuclear power to essentially present day light water reactors that represent only a first product of this broad new technology. The book is well organized and easy to follow. It explains the importance and benefits of pushing ahead with near breeders and h o w the thermal versions c o m p l e m e n t on the t h o r i u m fuel cycle the fast breeders on the u r a n i u m cycle. It also indicates the smaller environmental impacts and
advantageous safety features of these reactors. Restricting itself to the CANDU-Th, light water, molten salt and heavy water suspension breeders or near breeders the book makes no m e n t i o n of other potential solutions such as accelerator (spallation) breeding or gas-core reactors with very low fissile inventories which could be made available in time to solve a more severe u r a n i u m shortage crisis. In the valuable comparative strategy studies of various reactor combinations the book does include one high temperature reactor case and one fast breeder (LMFBR) case along side with the systems treated in the book while other promising i m p o r t a n t H T R and the very promising gas-cooled fast breeder (GCFR) cases are n o t mentioned. REINO EKHOLM