On-axis RF coupler and HOM damper for superconducting accelerator cavities
First Claim
1. An on-axis radiofrequency coupler for a particle accelerator having a superconducting cavity comprising:
- a radiofrequency (rf) waveguide stub operable to receive an rf power signal transmitted through an rf waveguide from a rf power source, said waveguide stub being operable to convert the mode of said rf power signal from a transverse electric (TE) mode into a transverse electromagnetic (TEM) mode, said stub having first and second aligned openings in first and second opposing side walls thereof, respectively, which openings are alignable with the axis of a particle beam line of a superconducting particle accelerator cavity, said waveguide stub further including a ceramic tube connecting said openings in sealing relationship and extending coaxially with said beam line;
an electrically conductive coupler tube having first and second ends, said coupler tube extending coaxially through said openings in said opposing walls of said waveguide stub and through said ceramic tube, said first end of said coupler tube extending into and being connected to a tubular vacuum bellows assembly affixed to the outside of said first wall of said waveguide stub and centered on said first opening, said bellows assembly including a linear drive translator operable to selectively move said coupler tube in translation coaxially along said axis of said beam line;
said coupler tube being sized and positioned such that said second end of said coupler tube penetrates a tubular electrically conductive extension of said superconducting cavity by a variable distance determined by the actuation of said drive translator, such that said coupler tube and said tubular extension function as a coaxial transmission line to introduce said rf power signal into said accelerator cavity, and whereby the electromagnetic load in said cavity can be selectively balanced to achieve optimum particle acceleration and energy efficiency.
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Accused Products
Abstract
An on-axis rf power coupler for a superconducting particle accelerator includes a coaxial coupler tube that passes through a rf waveguide stub connected to a rf power source. The coupler tube is movable in translation along the axis of the beam path by a piezoelectric drive to permit variation of the coupling between the rf power source and the resonant signal in the accelerator. A tubular rf window extending through the waveguide stub, together with a vacuum bellows assembly connected to the coupler tube, isolate the vacuum inside the accelerator cavity from the vacuum in the rf waveguide and stub. A choke joint in the wall of the waveguide selectively passes unwanted HOM signals out of the waveguide stub and away from the accelerator cavity, where they are dissipated by ferrite tiles on the coupler tube. The upstream end of the coupler tube and a tubular extension of the accelerator cavity form a coaxial line for introducing rf power into the accelerator. Further, the upstream end of the coupler tube separates the rf signal in the cavity from unwanted HOM signals and diverts the latter through the choke joint for isolation and dissipation.
248 Citations
20 Claims
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1. An on-axis radiofrequency coupler for a particle accelerator having a superconducting cavity comprising:
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a radiofrequency (rf) waveguide stub operable to receive an rf power signal transmitted through an rf waveguide from a rf power source, said waveguide stub being operable to convert the mode of said rf power signal from a transverse electric (TE) mode into a transverse electromagnetic (TEM) mode, said stub having first and second aligned openings in first and second opposing side walls thereof, respectively, which openings are alignable with the axis of a particle beam line of a superconducting particle accelerator cavity, said waveguide stub further including a ceramic tube connecting said openings in sealing relationship and extending coaxially with said beam line; an electrically conductive coupler tube having first and second ends, said coupler tube extending coaxially through said openings in said opposing walls of said waveguide stub and through said ceramic tube, said first end of said coupler tube extending into and being connected to a tubular vacuum bellows assembly affixed to the outside of said first wall of said waveguide stub and centered on said first opening, said bellows assembly including a linear drive translator operable to selectively move said coupler tube in translation coaxially along said axis of said beam line; said coupler tube being sized and positioned such that said second end of said coupler tube penetrates a tubular electrically conductive extension of said superconducting cavity by a variable distance determined by the actuation of said drive translator, such that said coupler tube and said tubular extension function as a coaxial transmission line to introduce said rf power signal into said accelerator cavity, and whereby the electromagnetic load in said cavity can be selectively balanced to achieve optimum particle acceleration and energy efficiency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An on-axis radiofrequency coupler for a particle accelerator having a superconducting cavity comprising:
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a radiofrequency (rf) waveguide stub for receiving an rf power signal transmitted through an rf waveguide from a rf power source, said waveguide stub being operable to convert said rf power signal from a transverse electric mode into a transverse electromagnetic mode, said stub having first and second aligned circular openings in first and second opposing side walls thereof, respectively, which openings are alignable with the axis of a particle beam line of a superconducting particle accelerator, said waveguide stub including a circular rf choke joint in said first wall, and said waveguide stub further including a ceramic tube connecting said openings in sealing relationship and extending coaxially with said beam line; an electrically conductive coupler tube having first and second ends, said coupler tube extending coaxially through said openings in said opposing walls of said waveguide stub and through said ceramic tube, said choke joint being sized and positioned relative to the exterior surface of said coupler tube so as to pass higher-order-mode (HOM) signals out of said waveguide stub and away from said accelerator cavity, while blocking lower frequency power rf signals resonant in said stub and in said accelerator cavity said coupler tube extending into and being connected to a tubular vacuum bellows assembly affixed to the outside of said first wall of said waveguide stub and centered on said first opening, said bellows assembly including a linear drive translator operable to selectively move said coupler tube in translation coaxially along said axis of said beam line; said coupler tube being sized and positioned such that said second end of said coupler tube penetrates a tubular electrically conductive extension of said superconducting cavity by a variable distance determined by actuation of said drive translator, such that said coupler tube and said tubular extension function as a coaxial transmission line to introduce said rf power signal into said accelerator cavity, and whereby the electrical loading in said cavity can be selectively balanced to achieve optimum particle acceleration and energy efficiency. - View Dependent Claims (11, 12, 13, 14, 15)
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16. An on-axis radiofrequency coupler for a particle accelerator having a superconducting cavity comprising:
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a radiofrequency (rf) waveguide stub for receiving an rf power signal transmitted through an rf waveguide from a rf power source, said waveguide stub being operable to convert said rf power signal from a transverse electric mode into a transverse electromagnetic mode, said stub having first and second aligned circular openings in first and second opposing side walls thereof, respectively, which openings are alignable with the axis of a particle beam line of a superconducting particle accelerator, said waveguide stub including a circular rf choke joint in said first wall, and said waveguide stub further including a ceramic tube connecting said openings in sealing relationship and extending coaxially with said beam line; an electrically conductive coupler tube having first and second ends, said coupler tube extending coaxially through said openings in said opposing walls of said waveguide stub and through said ceramic tube, said choke joint being sized and positioned relative to the exterior surface of said coupler tube so as to pass higher-order-mode (HOM) signals out of said waveguide stub and away from said accelerator cavity, while blocking lower frequency power rf signals resonant in said stub and in said accelerator cavity said coupler tube extending into and being connected to a tubular vacuum bellows assembly affixed to the outside of said first wall of said waveguide stub and centered on said first opening, said bellows assembly including a linear drive translator operable to selectively move said coupler tube in translation coaxially along said axis of said beam line; said coupler tube being sized and positioned such that said second end of said coupler tube penetrates a tubular electrically conductive extension of said superconducting cavity by a variable distance determined by actuation of said drive translator, such that said coupler tube and said tubular extension function as a coaxial transmission line to introduce said rf power signal into said accelerator cavity, and whereby the electrical loading in said cavity can be selectively balanced to achieve optimum particle acceleration and energy efficiency. - View Dependent Claims (17, 18, 19, 20)
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Specification