CA1085054A - Accelerating structure for a linear charged particle accelerator - Google Patents
Accelerating structure for a linear charged particle acceleratorInfo
- Publication number
- CA1085054A CA1085054A CA300,103A CA300103A CA1085054A CA 1085054 A CA1085054 A CA 1085054A CA 300103 A CA300103 A CA 300103A CA 1085054 A CA1085054 A CA 1085054A
- Authority
- CA
- Canada
- Prior art keywords
- accelerating
- cavity
- section
- cavities
- accelerating structure
- 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
Links
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
- H05H9/04—Standing-wave linear accelerators
Abstract
ABSTRACT OF THE DISCLOSURE :
An accelerating structure for a linear particle accelerator operating in the travelling wave mode or in the standing wave mode comprises at least one accelerating section and a complementary bunching or pre-accelerating section formed by a resonant cavity of the reentrant type magnetically coupled with the first cavity of the accelerating section by means of a coupling iris, the reentrant cavity having a length L = (2m + 1) .lambda.o/4 and the distance D separating the interaction spaces of the first cavity of the complementary section and the first cavity of the accelerating section being equal to D = (2k + ? +.alpha.) .pi..beta..lambda.o , with O?.alpha. ?, n and k being integers, .beta. being the reduced velocity v/c of the particles and .lambda.o being the operating wave length of the accelerator.
An accelerating structure for a linear particle accelerator operating in the travelling wave mode or in the standing wave mode comprises at least one accelerating section and a complementary bunching or pre-accelerating section formed by a resonant cavity of the reentrant type magnetically coupled with the first cavity of the accelerating section by means of a coupling iris, the reentrant cavity having a length L = (2m + 1) .lambda.o/4 and the distance D separating the interaction spaces of the first cavity of the complementary section and the first cavity of the accelerating section being equal to D = (2k + ? +.alpha.) .pi..beta..lambda.o , with O?.alpha. ?, n and k being integers, .beta. being the reduced velocity v/c of the particles and .lambda.o being the operating wave length of the accelerator.
Description
~08~i054 This invention relates to an accelerating structure intended to be used in a linear charged particle accelerator.
More particularly, the invention relates to the bunching (or preaccelerating) section preceding the accelerating section of this accelerator.
In certain apparatus using particle accelerator operating at microwave frequencies (C or X-band for example), it can be of advantage to have a compact accelerating structure supplied with microwave power by a single microwave generator.
However, conventional bunchlng means, as described for example in the US Patent No. 2 813 996, generally comprise two resonant cavities separated one from the other by a drift-tube havlng several wavelengths in length and means for adjusting the relative phase to the microwave energy fed to both cavities and accelerating structure. Manufacture of such accelerators and phase adjustment of the different resonant cavities-involves considerable difficulties. The accelerating structure according ; to the present invention enables this disadvantage to be obviated.
It is an object of the invention to provide an accelerating structure for a linear charged particle accelerator comprises at least one accelerating section formed by a series of resonant cavities electromagnetically coupled with one another and provided with axial orifices for the passage of the beam of particles, and a complementary cavity section disposed in front of and joined to the accelerating section in the path of the beam of particles. The complementary cavity section have a common wall with the first cavity of the accelerating section. The accelerating structure further comprises means for injecting a microwave signal into the accelerating structure. The complementary section is formed by a resonant cavity of reentrant type, magnetically coupled ' lOBS054 .
with the first cavity of the accelerating section by means of al: least one coupling iris. The reentrant cavity have a length such that the distance separating in the interaction spaces of the reentrant cavity and of the first cavity of the accelerating section is equal to D = (2k + n+ ~ OI with O~ 1, n and
More particularly, the invention relates to the bunching (or preaccelerating) section preceding the accelerating section of this accelerator.
In certain apparatus using particle accelerator operating at microwave frequencies (C or X-band for example), it can be of advantage to have a compact accelerating structure supplied with microwave power by a single microwave generator.
However, conventional bunchlng means, as described for example in the US Patent No. 2 813 996, generally comprise two resonant cavities separated one from the other by a drift-tube havlng several wavelengths in length and means for adjusting the relative phase to the microwave energy fed to both cavities and accelerating structure. Manufacture of such accelerators and phase adjustment of the different resonant cavities-involves considerable difficulties. The accelerating structure according ; to the present invention enables this disadvantage to be obviated.
It is an object of the invention to provide an accelerating structure for a linear charged particle accelerator comprises at least one accelerating section formed by a series of resonant cavities electromagnetically coupled with one another and provided with axial orifices for the passage of the beam of particles, and a complementary cavity section disposed in front of and joined to the accelerating section in the path of the beam of particles. The complementary cavity section have a common wall with the first cavity of the accelerating section. The accelerating structure further comprises means for injecting a microwave signal into the accelerating structure. The complementary section is formed by a resonant cavity of reentrant type, magnetically coupled ' lOBS054 .
with the first cavity of the accelerating section by means of al: least one coupling iris. The reentrant cavity have a length such that the distance separating in the interaction spaces of the reentrant cavity and of the first cavity of the accelerating section is equal to D = (2k + n+ ~ OI with O~ 1, n and
2 4 k being integers,~ being the reduced velocity v/c of the particles and ~O being the operating wavelength of the accelerator.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made tc the drawings, given solely by way of examples which accompany the following description, and wherein:
- Figs 1 to 3 diagrammatically illustrate three examples of embodiment of a linear accelerating structure according to the invention.
Fig. 1 shows an accelerating structure according to the invention comprising an accelerating section SA formed by a series of accelerating cavities Al, A2....... and a comple-mentary section Sc which may be a bunching section or an accelerating section, as explained hereinafter.
This complementary section Sc is formed by a resonant ; cavity C of the reentrant type. In the example illustrated, the cavity C has two portions of length 11 and 12 having different radii rl and r2, thus establishing an impedance match. In the example of embodiment shown in Fig. 1, the lengths 11, 12, r2 have been selected such that :
, L = 11 + 12 + r2 ~ (2m + 1) ~O
,~' where m is an integer at least equal to 1. The cavity C is ' magnetically coupled in a direct manner with the first cavity Al by means of a coupling iris Il formed in the thin wall of the cavity C adjacent the cavity A1. The lengths 11 and 12 of the portions of radii r1 and r2 are approximately l.~o :' ~085054 The centres of the interaction spaces of the cavities C and Al are se~arated by a distance D substantially equal to:
where k and n are integers at least equal to 1 and ~ satisfies the inequality: O~ is equal to the reduced velocity V/C
of the particles and ~O is the operating wave length in vacuo of the accelerating structure.
When ~= o and n in an even number (for example 2), the cavity C ispre-accelerating cavity and, when ~ = o and n is an odd number, the cavity is a bunching cavity.
In this last case (n = 1), during the operating of the accelerator using such a structure, the passage of the central particle of a bunch of particles through the inter-action space of the reentrant cavity C takes place at the instant when the microwave~field is zero in the cavity C.
The particles preceding the central particle are decelerated whilst the particles following it are accelerated, so that the beam of particles is bunched into groups.
In the case where the cavity C is used as a pre-accelerating cavity, the central particle of the bunch of parti-cles in question passes through the interaction space of the cavity C when the microwave field is maximal.
In the two cases considered, the central particle passes through tHe interaction space of the accelerating cavity Al when the microwave accelerating field is maximal.
However, the cavity C may also be determined in such a way that it acts both as a pre-accelerating and a pre-bunching cavity. This is the case if, where n is an odd number (for example 1), the number ~ is selected equal to 1 .
Accordingly:
D = (2k + 1 + 1) -1085VS~
If k = 1, then :
D = 11~ ~O
In order to avoid excitation of the revolution modes in the reentrant cavity ~, it is of advantage to couple the cavity C with the accelerating cavity Al by means of two irises Il and I2 disposed symmetrically on either side of the axis of the cavlty C or by means of three irises Il, I2, I3 disposed at 120 from one another.
1 By way of non-limiting example, if it is desired to pre-accelerate a beam of electrons having an energy of 30 KeV
in a particle accelerator operating at a frequency of 7.5 Ghz (~ = 4 cm), the interaction spaces of the cavities C and Al may be lengths of, respectively, 6 mm and 8 mm. The particular form of the reentrant cavity C, such as shown in Fi~. 1, which constitutes an impendance match to ~ /4, enables the coupling magnetic field to be increased by reducing the impendance of the equivalent microwave line and the electrical field near the axis of the structure to be increased by increasing that same impendance.
The complementary bunching and/or pre-accelerating section C such as defined above may also be associated with an accelerating standing-wave structure of the multiperiodic -!
type. In Fig. 3, the accelerating structure SA is a tri-periodic structure, such as described, for example by the Applicant in the U~S. Patent No. 3,953,758. This triperiodic structure comprising accelerating resonant cavities All, A12, A14 ...... and coupling cavities al3 "
,, .
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made tc the drawings, given solely by way of examples which accompany the following description, and wherein:
- Figs 1 to 3 diagrammatically illustrate three examples of embodiment of a linear accelerating structure according to the invention.
Fig. 1 shows an accelerating structure according to the invention comprising an accelerating section SA formed by a series of accelerating cavities Al, A2....... and a comple-mentary section Sc which may be a bunching section or an accelerating section, as explained hereinafter.
This complementary section Sc is formed by a resonant ; cavity C of the reentrant type. In the example illustrated, the cavity C has two portions of length 11 and 12 having different radii rl and r2, thus establishing an impedance match. In the example of embodiment shown in Fig. 1, the lengths 11, 12, r2 have been selected such that :
, L = 11 + 12 + r2 ~ (2m + 1) ~O
,~' where m is an integer at least equal to 1. The cavity C is ' magnetically coupled in a direct manner with the first cavity Al by means of a coupling iris Il formed in the thin wall of the cavity C adjacent the cavity A1. The lengths 11 and 12 of the portions of radii r1 and r2 are approximately l.~o :' ~085054 The centres of the interaction spaces of the cavities C and Al are se~arated by a distance D substantially equal to:
where k and n are integers at least equal to 1 and ~ satisfies the inequality: O~ is equal to the reduced velocity V/C
of the particles and ~O is the operating wave length in vacuo of the accelerating structure.
When ~= o and n in an even number (for example 2), the cavity C ispre-accelerating cavity and, when ~ = o and n is an odd number, the cavity is a bunching cavity.
In this last case (n = 1), during the operating of the accelerator using such a structure, the passage of the central particle of a bunch of particles through the inter-action space of the reentrant cavity C takes place at the instant when the microwave~field is zero in the cavity C.
The particles preceding the central particle are decelerated whilst the particles following it are accelerated, so that the beam of particles is bunched into groups.
In the case where the cavity C is used as a pre-accelerating cavity, the central particle of the bunch of parti-cles in question passes through the interaction space of the cavity C when the microwave field is maximal.
In the two cases considered, the central particle passes through tHe interaction space of the accelerating cavity Al when the microwave accelerating field is maximal.
However, the cavity C may also be determined in such a way that it acts both as a pre-accelerating and a pre-bunching cavity. This is the case if, where n is an odd number (for example 1), the number ~ is selected equal to 1 .
Accordingly:
D = (2k + 1 + 1) -1085VS~
If k = 1, then :
D = 11~ ~O
In order to avoid excitation of the revolution modes in the reentrant cavity ~, it is of advantage to couple the cavity C with the accelerating cavity Al by means of two irises Il and I2 disposed symmetrically on either side of the axis of the cavlty C or by means of three irises Il, I2, I3 disposed at 120 from one another.
1 By way of non-limiting example, if it is desired to pre-accelerate a beam of electrons having an energy of 30 KeV
in a particle accelerator operating at a frequency of 7.5 Ghz (~ = 4 cm), the interaction spaces of the cavities C and Al may be lengths of, respectively, 6 mm and 8 mm. The particular form of the reentrant cavity C, such as shown in Fi~. 1, which constitutes an impendance match to ~ /4, enables the coupling magnetic field to be increased by reducing the impendance of the equivalent microwave line and the electrical field near the axis of the structure to be increased by increasing that same impendance.
The complementary bunching and/or pre-accelerating section C such as defined above may also be associated with an accelerating standing-wave structure of the multiperiodic -!
type. In Fig. 3, the accelerating structure SA is a tri-periodic structure, such as described, for example by the Applicant in the U~S. Patent No. 3,953,758. This triperiodic structure comprising accelerating resonant cavities All, A12, A14 ...... and coupling cavities al3 "
,, .
Claims (9)
1. An accelerating structure for a linear charged particle accelerator comprising at least one accelerating section formed by a series of resonant cavities electromagne-tically coupled with one another and provided with axial orifices for the passage of the beam of particles, and a complementary cavity section disposed in front of and joined to said accelerating section in the path of said beam of particles, said complementary cavity section having a common wall with the first cavity of said accelerating section, said accelerating structure further comprising means for injecting a microwave signal into said accelerating structure, said complementary section being formed by a resonant cavity of reentrant type, magnetically coupled with said first cavity of said accelerating section by means of at least one coupling iris, said reentrant cavity having a length such that the distance separating in the interaction space of the reentrant cavity and of the first cavity of the accelerating section is equal to D = (2k + ? +.alpha.).pi..beta. .lambda.o, with 0?.alpha.? ?, n and k being integers, .beta. being the reduced velocity v/c of the particles and .lambda.o being the operating wavelength of the accelerator.
2. An accelerating structure as claimed in claim 1, wherein said cavity comprises two portions respectively having different radii r1 and r2, these two portions respectively having lengths of approximately
3. An accelerating structure as claimed in claim 1, wherein said cavity is a "pre-accelerating" cavity, .alpha. being equal to zero and n being an even number.
4. An accelerating structure as claimed in claim 1, wherein said cavity is a "bunching" cavity, .alpha. being equal to zero and n being an odd number.
5. An accelerating structure as claimed in claim 1, wherein said cavity is both a pre-accelerating and a bunching cavity, n being an odd number and .alpha. being substantially equal to 0.25.
6. An accelerating structure as claimed in claim 1 and operating in the traveling wave mode, said cavities, of the accelerating section being electrically coupled with one another by means of orifices for the passage of the beam, said means for injecting the microwave signal comprising a waveguide magnetically coupled with said first accelerating cavity of a coupling iris.
7. An accelerating structure as claimed in claim 1 and operating in the travelling wave mode, said cavities of the accelerating section being magnetically coupled with one another by means of at least one coupling hole formed in the common wall of two successive cavities, and in that said means for injecting the microwave signal into the accelerating structure comprises a waveguide magnetically coupled with the last cavity of the accelerating section by means of a coupling iris.
8. An accelerating structure as claimed in claim 7, wherein two successive resonant cavities of said accelerating section are magnetically coupled with one another by means of three coupling holes disposed at 120° from one another.
9. An accelerating structure as claimed in claim 1 and operating in the standing wave mode, said accelerating sections being a multiperiodic structure formed by accelerating resonant cavities and coupling cavities, of which the first cavity is magnetically coupled by means of an iris with said reentrant cavity.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7709808 | 1977-03-31 | ||
| FR7709808A FR2386231A1 (en) | 1977-03-31 | 1977-03-31 | ACCELERATOR STRUCTURE FOR LINEAR ACCELERATOR OF CHARGED PARTICLES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1085054A true CA1085054A (en) | 1980-09-02 |
Family
ID=9188854
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA300,103A Expired CA1085054A (en) | 1977-03-31 | 1978-03-30 | Accelerating structure for a linear charged particle accelerator |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4150322A (en) |
| CA (1) | CA1085054A (en) |
| DE (1) | DE2813912A1 (en) |
| FR (1) | FR2386231A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2551617B1 (en) * | 1983-09-02 | 1985-10-18 | Cgr Mev | SELF-FOCUSING LINEAR ACCELERATOR STRUCTURE OF CHARGED PARTICLES |
| FR2576477B1 (en) * | 1985-01-18 | 1987-03-06 | Cgr Mev | LINEAR ACCELERATOR ASSEMBLY OF LOADED PARTICLES |
| JPS61288400A (en) * | 1985-06-14 | 1986-12-18 | 日本電気株式会社 | Stationary linear accelerator |
| FR2679727B1 (en) * | 1991-07-23 | 1997-01-03 | Cgr Mev | PROTON ACCELERATOR USING MAGNETICALLY COUPLED PROGRESSIVE WAVE. |
| DE10333454B4 (en) * | 2003-07-22 | 2006-07-13 | GSI Gesellschaft für Schwerionenforschung mbH | Drift tube accelerator for accelerating ion packets |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2813996A (en) * | 1954-12-16 | 1957-11-19 | Univ Leland Stanford Junior | Bunching means for particle accelerators |
| FR2110799A5 (en) * | 1970-10-30 | 1972-06-02 | Thomson Csf |
-
1977
- 1977-03-31 FR FR7709808A patent/FR2386231A1/en active Granted
-
1978
- 1978-03-28 US US05/891,057 patent/US4150322A/en not_active Expired - Lifetime
- 1978-03-30 CA CA300,103A patent/CA1085054A/en not_active Expired
- 1978-03-31 DE DE19782813912 patent/DE2813912A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| FR2386231A1 (en) | 1978-10-27 |
| DE2813912A1 (en) | 1978-10-12 |
| US4150322A (en) | 1979-04-17 |
| FR2386231B1 (en) | 1981-02-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |