US3263116A - Waveguide structure for linear particle accelerators having an undulating configuration - Google Patents

Waveguide structure for linear particle accelerators having an undulating configuration Download PDF

Info

Publication number
US3263116A
US3263116A US179430A US17943062A US3263116A US 3263116 A US3263116 A US 3263116A US 179430 A US179430 A US 179430A US 17943062 A US17943062 A US 17943062A US 3263116 A US3263116 A US 3263116A
Authority
US
United States
Prior art keywords
guide
mode
cavities
wave
apertures
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US179430A
Other languages
English (en)
Inventor
Azam Guy
Leboutet Hubert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
CSF Compagnie Generale de Telegraphie sans Fil SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CSF Compagnie Generale de Telegraphie sans Fil SA filed Critical CSF Compagnie Generale de Telegraphie sans Fil SA
Application granted granted Critical
Publication of US3263116A publication Critical patent/US3263116A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H9/00—Linear accelerators
    • H05H9/02—Travelling-wave linear accelerators

Definitions

  • the present invention relates to a novel wave guide structure, and more particularly to a novel wave guide structure for linear accelerators which effectively prevents the propagation of certain unwanted modes.
  • the linear accelerators which operate by interaction with a traveling wave utilize a wave guide constituted by a geometrically periodic structure, generally by -a cylinder of revolution containing transverse irises distributed at predetermined intervals, which are fixed to the cylinder along the periphery thereof and pierced at their center by a hole enabling passage of the beam of accelerated particles and coupling therebetween the cavities defined between the successive irises.
  • This structure may transmit waves at different modes each of which possesses its own bandpass.
  • the mode chosen for the acceleration of the particles is that which, when propagating through the cavities coupled with one another by holes having a diameter which diminishes progressively or in a stepwise manner, is derived by continuity from the mode TM of the cylindrical cavity defined by the space comprised between two irises 'in which there would be no coupling holes or apertures.
  • the other possible modes are parasitic modes which can, under certain circumstances, disturb functioning of the normal mode by removing energy therefrom. This trouble becomes evident, in general, with high currents of the accelerated beam, and particularly by the fact that the pulse of the beam collected on a target placed at the end of the accelerator presents deformations consisting either in a simple shortening in time with respect to the starting pulse or in a clip or saddle in the top of the pulse, of location, depth and width which vary with the respective cases.
  • the present invention aims at a periodic accelerator guide structure which avoids the above-indicated drawbacks.
  • the present invention provides means for preventing the tota lor partial coincidence, along the path of propagation, between the band-pass of the mode TM and the band of the second harmonics of the frequencies contained in the bandpass of the normal mode utilized for the interaction with a view toward the acceleration of the beam.
  • the means according to the present invention consist in substituting for the usual law of variation of the diameter of the coupling hole along the section of the accelerator, i.e., a law of progressive or step-wise decrease between a maximum entrance diameter and a minimum exit diameter, an undulating law between these two diameters, the undulations being either periodic or non periodic and extending at least over a length of guide over which, with a design according to the known art, this diameter would exceed a certain threshold which only depends on the frequency used and corresponds to the beginning of overlap between the band of the mode TM and the band of the second harmonics of the band of the normal mode.
  • a further object of the present invention resides in the prov1s1on of a wave guiding structure for .a linear accelerator which may be operated with high electron beam currents without endangering the efficiency by interference from parasitic modes removing useful energy from the electron beam to the detriment of the usable output.
  • Still another object of the present invention resides in the provision of a wave guiding structure for linear accelerators achieving all of the foregoing aims and objects without changing the performance thereof from the point of view of energy level as compared to the prior art structures.
  • FIGURE 1 is a diagram of curves given only by way of explanation
  • FIGURE 2 is an axial cross sectional view through a prior art guide construction
  • FIGURE 3 is an axial cross sectional view through a guide in accordance with the present invention to be substituted for the guide of FIGURE 2.
  • FIGURE 1 is a diagram showing, along the abscissa, the iris diameters d, and, along the ordinates, two scales, the one on the left corresponding to the frequencies f at an arbitrary scale, and the other, on the right, being double of the former and corresponding to the frequencies 2f at the same scale.
  • the variation of the band-pass of the desired normal mode derived from the mode TM the frequencies of this mode being read on the left scale and the band-pass being contained between the curves 1 and 2.
  • the band-pass of mode TM the frequencies of this mode being read on the scale at the right and the band-pass of this mode being contained between curves 3 and 4. All of these curves have been found experimentally with a particular device, but may be considered as typical for the guide structure of cylindrical form loaded with irises, independently of its dimension.
  • the modes which may be generated in a wave guide are distinguished from each other by the frequency bands susceptible of exciting them respectively, the position of the band depending in general on the structure of the circuit, for a given structure of its design, and for a given design of the circular iris structure, of the diameter of the holes in the irises.
  • This dependence is represented in FIGURE 1. It is evident therefrom that, if the diameter of the hole in the iris is D it is necessary that the excitation frequency be comprised between ma and mb (as read on the left-hand scale), if the mode TM is to be excited, and that, for exciting the mode TM the frequency must be comprised between me and me (as read on the right-hand scale).
  • the frequency must be comprised between ng and uh (on the scale at left) and, for exciting the mode TM it is necessary that the frequency be between ni and nk as read on the right-hand scale.
  • the band of the second harmonics of the frequencies of the band-pass of the normal mode begins to overlap with the band-pass of the mode TM so that the unwanted phenomena mentioned above begin to appear when a certain threshold of the diameter has been exceeded, which is variable with the frequency of the chosen wave.
  • the threshold is given by the diameter d corresponding to point B of the ordinate f on curve 3. This threshold can thus be determined experimentally for each given structure and for each frequency of the selected wave.
  • FIGURE 2 is a cross section through a guide portion calculated to obtain certain desired performances and made in accordance with the prior art. It is supposed that this realization has ended in the constitution of the guide section by a certain number of cavities of which the diameter of the coupling holes varies between a maximum value d at the inlet and a minimum value d at the outlet. For example, this variation has been realized in three steps or gradients the guide being constituted by the section I having cavities 5 with holes of d by the section III having cavities 6 with holes of intermediate diameters, and by section V having cavities 7 with holes of d These sections are, respectively, connected with one another by sections II and IV in which the diameter of the coupling holes varies progressively.
  • the inner diameters of the cavities are adjusted to maintain the appropriate law of variation of the phase velocity of the high frequency wave propagating through each cavity of the guide. It will also be supposed that the examination of the modes of propagation within the guide has shown the critical threshold d mentioned hereinabove in connection with FIGURE 1 to be smaller than a but larger than d i.e., that the unwanted phenomena mentioned hereinabove can be produced in the first part of the guide L, up to the point where the diameter of the coupling hole becomes smaller than d Acording to the present invention, after having calculated the guide for the desired performances, and after having determined in particular the number of cavities necessary for realizing the known structure of FIGURE 2, such structure is realized according to FIGURE 3, i.e., by substituting for the decreasing law of the diameter of holes of FIGURE 2, an undulating law, along the same section, between values d and d
  • the guide being generally constituted by a group of individual cavities, it is sufficient to disassemble or take apart the guide of FIGURE 2 and to regroup the cavities by intercalating a
  • the pitch of the cavities would be of 25 mm.
  • the length L covered by 15 cavities of sections I and II of FIGURE 2 is, in this case, equal to 375 mm.
  • the entirety of sections I to V being realized with 40 cavities, their distribution between the sections I to V' of FIGURE 3 produces 8 cavities per section, i.e., a section of 200 mm. length. This length is well below the value L defined hereinabove.
  • the drawing also shows a series of particle bunches 8 in FIGURE 3, resulting from bunching of the beam by interaction with the traveling wave propagating through the cavities 5 and 7.
  • a linear particle accelerator comprising a wave guide having a geometrically periodical structure, comprising transverse irises periodically distributed along said guide and having in their center coupling apertures between cavities defined between two successive irises, the size of said apertures varying substantially according to an undulatory law along said guide between a minimum size lower than the cut-out threshold of the TM mode, and a maximum size higher than the said threshold and a particle beam moving within said guide in inter-action with the traveling wave propagating therein.
  • a linear particle accelerator comprising a wave guide having a geometrically periodical structure, comprising transverse irises periodically distributed along said guide and having in their center coupling apertures between cavities defined between two successive irises, the size of said apertures varying substantially according to an undulatory law along said guide between a minimum size lower than the cut-out threshold of the TM mode, and a maximum size higher than the said threshold, a particle beam moving within said guide in inter-action with the travelling wave propagating therein, and the sizes of said cavities being variable in dependence on the sizes of corresponding central apertures, to adjust the phase velocity of the travelling wave propagating within the guide to the velocity of th accelerated particle.
  • a wave guiding structure for linear particle accelerators having a substantially geometrically periodical structure eifectively formed by substantially transverse irises periodically distributed along said guide and provided in the centers thereof with coupling apertures between cavities, the improvement essentially consisting in means in said wave guiding structure preventing the propagation therein of waves of predetermined frequencies that induce parasitic modes of operation, said means being effectively constituted by varying the size of said apertures along said guide substantially in accordance with an undulatory law between a minimum size lower than the cut-out threshold of the TM mode, and a maximum size higher than th said threshold and a particle beam moving within said guide in inter-action with the travelling wave propogating therein.
  • a wave guiding structure for a linear particle accelerator comprising a particle beam moving within said guide in inter-action with the travelling wave propagating therein, first means constituting a substantially geometrically periodical structure eifectively forming a plurality of cavities provided with coupling means therebetween in the form of .central apertures to enable passage therethrough of the accelerated particles, said first means effectively providing a predetermined band-pass for the fundamental frequencies and harmonics thereof of waves, the structures of which correspond to the desired modes, said central apertures forming an undulating pattern along the length of said wave guiding structure effectively preventing propagation therealong of waves the structures of which correspond to parasitic modes of which the frequencies are contained in said band-pass along a length of the guide equal to or greater than a wave length of said waves.
  • a wave guiding structure for linear particle accelerators having a given band-pass of frequencies and utilizing a mode neighboring the TM mode for the useful mode of operation and a particle beam moving within said guide in inter-action with the travelling wave propagating therein
  • the improvement essentially consisting in means in said wave guiding structure for elfectively preventing an overlap along the path of propagation for a distance equal to or greater than a Wave length between the bandpass of the TM mode and the band of the second harmonics of the frequencies contained within the band-pass of the operating mode.
  • a Wave guiding structure for linear particle accelerators having a substantially geometrically periodical cavity structure effectively formed by plural cavity means including substantially transverse irises periodically distributed along said guide and provided in the centers thereof with coupling apertures between cavity means, said cavity means in said wave guiding structure preventing the propagation therein of waves of predetermined frequencies that induce parasitic modes of operation, said cavity means being effectively constituted by varying the size of said apertures along said guide substantially in accordance with an undulatory law between a minimum size lower than the cut-out threshold of the TM mode, and a maximum size higher than the said threshold and a particle beam moving Within said guide in inter-action with the traveling wave propagating therein.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)
US179430A 1961-03-24 1962-03-13 Waveguide structure for linear particle accelerators having an undulating configuration Expired - Lifetime US3263116A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR856698A FR1293014A (fr) 1961-03-24 1961-03-24 Perfectionnements aux guides d'ondes pour accélérateurs linéaires

Publications (1)

Publication Number Publication Date
US3263116A true US3263116A (en) 1966-07-26

Family

ID=8751615

Family Applications (1)

Application Number Title Priority Date Filing Date
US179430A Expired - Lifetime US3263116A (en) 1961-03-24 1962-03-13 Waveguide structure for linear particle accelerators having an undulating configuration

Country Status (7)

Country Link
US (1) US3263116A (de)
BE (1) BE614845A (de)
CH (1) CH406471A (de)
DE (1) DE1178155B (de)
FR (1) FR1293014A (de)
GB (1) GB935000A (de)
NL (1) NL276257A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3597710A (en) * 1969-11-28 1971-08-03 Microwave Dev Lab Inc Aperiodic tapered corrugated waveguide filter
US3845422A (en) * 1973-04-17 1974-10-29 Microwave Dev Labor Stop band filter
US20070024394A1 (en) * 2005-07-27 2007-02-01 Mario Sorolla Microwave bandstop filter for an output multiplexer

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2176505B1 (de) * 1972-03-21 1975-10-24 Thomson Csf

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR969886A (fr) * 1948-07-23 1950-12-27 Csf Perfectionnements aux tubes à onde progressante
GB655410A (en) * 1947-10-06 1951-07-18 Nat Res Dev Improvements in and relating to electromagnetic wave propagating structures
US2623121A (en) * 1950-04-28 1952-12-23 Nat Union Radio Corp Wave guide

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB655410A (en) * 1947-10-06 1951-07-18 Nat Res Dev Improvements in and relating to electromagnetic wave propagating structures
CH278418A (de) * 1947-10-06 1951-10-15 Nat Res Dev Elektromagnetischer Wellenleiter.
US2641731A (en) * 1947-10-06 1953-06-09 English Electric Valve Co Ltd Wave propagating electron discharge device
FR969886A (fr) * 1948-07-23 1950-12-27 Csf Perfectionnements aux tubes à onde progressante
US2623121A (en) * 1950-04-28 1952-12-23 Nat Union Radio Corp Wave guide

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3597710A (en) * 1969-11-28 1971-08-03 Microwave Dev Lab Inc Aperiodic tapered corrugated waveguide filter
US3845422A (en) * 1973-04-17 1974-10-29 Microwave Dev Labor Stop band filter
US20070024394A1 (en) * 2005-07-27 2007-02-01 Mario Sorolla Microwave bandstop filter for an output multiplexer
US7468641B2 (en) * 2005-07-27 2008-12-23 Agence Spatiale Europeenne Microwave bandstop filter for an output multiplexer

Also Published As

Publication number Publication date
BE614845A (fr) 1962-07-02
NL276257A (de) 1964-10-12
CH406471A (fr) 1966-01-31
GB935000A (en) 1963-08-21
DE1178155B (de) 1964-09-17
FR1293014A (fr) 1962-05-11

Similar Documents

Publication Publication Date Title
US2881348A (en) Delay line for traveling wave tubes
GB942685A (en) High power electron discharge device
GB652219A (en) High frequency electric discharge device
DE69833662T2 (de) Multimodale dielektrische Resonanzvorrichtung, dielektrisches Filter, Synthesierer, Verteiler und Kommunikationsgerät
GB1597774A (en) Heavy-ion accelerating structure
US3657670A (en) Microwave bandpass filter with higher harmonics rejection function
US3906300A (en) Multiperiodic accelerator structures for linear particle accelerators
US5469022A (en) Extended interaction output circuit using modified disk-loaded waveguide
US2785381A (en) Electromagnetic wave filter
US3263116A (en) Waveguide structure for linear particle accelerators having an undulating configuration
US2963663A (en) Waveguide transducer
US4147956A (en) Wide-band coupled-cavity type traveling-wave tube
US4973924A (en) Mode converter for microwave power transmission circuit
US3593220A (en) High power microwave low-pass filter of the leaky wall type
US3750183A (en) Multimode antenna system
US3611214A (en) Waveguide reflective harmonic filter
US3205398A (en) Long-slot coupled wave propagating circuit
GB1078236A (en) High frequency electron discharge devices
SU560541A3 (ru) Полосно-пропускающий сверхвысокочастотный фильтр
US3471738A (en) Periodic slow wave structure
US4800322A (en) Broadband klystron cavity arrangement
US2842705A (en) Particle accelerator
US3846664A (en) Coupled cavity travelling wave tubes
US3068432A (en) Ladder type delay line
US3693038A (en) Traveling wave tube (twt) oscillation prevention device