Radio frequency focused drift tube linear accelerator
First Claim
1. A drift tube linear accelerator comprisinga cylindrical tank excited with RF fields in the TM010 RF cavity mode, said tank having an input for receiving a particle beam and an output for emitting said particle beam at a higher energy level;
- a plurality of drift tubes axially arranged in said tank, said plurality of drift tubes being configured to define an acceleration gap between each drift tube, wherein said particle beam is accelerated as it traverses through said gap and wherein said particle beam is focused as it traverses through said drift tube, said drift tube comprising;
a first electrode supporting a first pair of fingers protruding substantially into the center of said drift tube from a first end of said drift tube, said first pair of fingers lying in a first plane;
a second electrode supporting a second pair of fingers protruding substantially into the center of said drift tube from a second end of said drift tube opposite of said first end, said second pair of fingers lying in a second plane substantially perpendicular to said first plane; and
means for supporting said first electrode and said second electrode along said axis of said tank;
wherein said pairs of fingers form a four finger geometry and wherein said first and second electrodes have alternating RF electrical potentials of different magnitudes, said potential differences establishing RF electric quadrupole fields in a region between said pairs of fingers, said focusing of said particle beam resulting from said RF electric quadrupole fields.
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Abstract
A drift tube linac incorporates rf-electric quadrupole focusing by employing drift tubes with only one drift-tube stem per particle wavelength and in which the lowest frequency RF cavity mode has a transverse magnetic field (TM010 -mode). Each drift tube comprises two separate electrodes that form a capacitor that couples to the axial electric field of the primary cavity mode. The electrodes operate at different electrical potentials, as determined by the RF fields in the cavity, and are supported by a single stem along the axis of a cylindrical cavity. Each electrode supports two fingers pointing towards the opposite end of the drift tube, forming a four fingered geometry that produces an RF quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to the particle wavelength (βλ) where β is the particle velocity in units of the velocity of light and λ is the free space wavelength of the rf. The particles traverse two distinct regions, namely the gaps between drift tubes, where the acceleration takes place, and the regions inside the drift tubes, where the RF focusing takes place. The linac of the present invention transforms the reverse fields into transverse fields for focusing such that the beam is not decelerated.
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Citations
10 Claims
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1. A drift tube linear accelerator comprising
a cylindrical tank excited with RF fields in the TM010 RF cavity mode, said tank having an input for receiving a particle beam and an output for emitting said particle beam at a higher energy level; a plurality of drift tubes axially arranged in said tank, said plurality of drift tubes being configured to define an acceleration gap between each drift tube, wherein said particle beam is accelerated as it traverses through said gap and wherein said particle beam is focused as it traverses through said drift tube, said drift tube comprising; a first electrode supporting a first pair of fingers protruding substantially into the center of said drift tube from a first end of said drift tube, said first pair of fingers lying in a first plane; a second electrode supporting a second pair of fingers protruding substantially into the center of said drift tube from a second end of said drift tube opposite of said first end, said second pair of fingers lying in a second plane substantially perpendicular to said first plane; and means for supporting said first electrode and said second electrode along said axis of said tank; wherein said pairs of fingers form a four finger geometry and wherein said first and second electrodes have alternating RF electrical potentials of different magnitudes, said potential differences establishing RF electric quadrupole fields in a region between said pairs of fingers, said focusing of said particle beam resulting from said RF electric quadrupole fields. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
Specification