JP3210610B2 - Drift tube type linac - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle passing through a drift tube by generating a high-frequency voltage between a plurality of drift tubes in which magnets are incorporated and generating a high-frequency voltage between the adjacent drift tubes. In connection with the drift tube type linac which was made to accelerate
In particular, it relates to a drift tube type linac that can efficiently accelerate charged particles with a small amount of high-frequency power.

[0002]

2. Description of the Related Art As an injector for a physical experiment device or a circular accelerator such as a cyclotron or a synchrotron, a beam passing port is provided at the center as shown in FIG.
A large number of drift tubes 20 incorporating magnets acting as beam acceleration electrodes are arranged in a straight line along the beam acceleration axis, and a high-frequency voltage is generated between the adjacent drift tubes 20 so that the inside of the drift tubes 20 is reduced. Drift tube type linacs (linear accelerators) adapted to accelerate passing charged particles are known.

In FIG. 4, reference numeral 10 denotes a vacuum tank constituting a high-frequency cavity of the linac main body, 12 denotes an inlet side wall to which an inlet side drift tube 22 is fixed, and 14 denotes an outlet side wall to which an outlet side drift tube 24 is fixed. , 16 are supports for supporting the respective drift tubes 20.

In such a linac, as shown in FIG. 5, when an AC voltage is applied to the drift tubes 20 periodically arranged on the beam acceleration axis, charged particles are accelerated or decelerated at a gap g between the drift tubes. You. At this time, when the particle reaches the gap g, if the length of the drift tube is increased in proportion to the particle velocity, the particle is always accelerated so that the high-frequency phase of the electric field always becomes the acceleration phase. Will be.

FIGS. 6 and 7 show acceleration states in an Alvaret-type linac. That is, as shown in FIG. 6, when the beam 8 exists in the gap g between the drift tubes 20, the beam 8 receives an acceleration force and a diverging force in the horizontal and vertical directions. Then, after a half cycle of the high frequency, beam 8
Are present in each drift tube 20 so that beam 8
Does not receive a deceleration force, but only receives a horizontal (vertical) convergence force and a vertical (horizontal) divergence force.

Since the drift tube type linac is a cavity in which a drift tube is arranged along a beam acceleration axis, the drift tube 20
In order to generate a high-frequency voltage in between, for example, as shown in FIG. 8, high-frequency power having a frequency equal to the natural frequency (resonance frequency) of the cavity resonance mode is supplied from an external high-frequency power supply 30. 8, reference numeral 32 denotes a coaxial tube for transmitting high-frequency power generated by the high-frequency power source 30 to the linac 10, and reference numeral 34 denotes a coupler that short-circuits the inner tube of the coaxial tube 32 to the outer tube.

The drift tube type linac has a TEM mode in addition to the Alvare type using the TM010 mode due to the difference in the resonance mode (pattern of the high frequency electromagnetic field generated at the time of resonance) used for generating the high frequency voltage. Videley type with modified coaxial resonator and interdigital-H using TE110 mode
There are types.

[0008]

In any case, the drift tube used in the conventional drift tube type linac has a simple thick cylindrical shape as shown in FIGS. For example, a quadrupole magnet 26 is incorporated, but there is a problem in that the energy of the accelerating particles is high and the efficiency of the high-frequency power decreases as the length of the drift tube 20 increases.

More specifically, the conventional drift tube 20
Since the whole was thick, as shown in FIG. 11, the ratio of the electric field (solid line E) contributing to beam acceleration in the total electric field (indicated by solid line E and broken line F) generated between the drift tubes 20 was small, and the gap was small. Most of the capacitance A between them did not contribute to the formation of the accelerating electric field, and the high-frequency energy (high-frequency electric field) existing there was wasted. In the figure, R is a beam passage port.

In order to increase the electrode efficiency even a little,
As shown in FIG. 12, the cross-sectional shape of the drift tube 20 may be devised so as to be close to a trapezoidal shape, but the efficiency has not been sufficiently increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to improve the power efficiency of a drift tube type linac and reduce high frequency power required for operation.

[0012]

According to the present invention, a plurality of drift tubes each including a magnet are arranged in a line, and a high-frequency voltage is generated between adjacent drift tubes to pass through the drift tubes. In a drift tube type linac adapted to accelerate charged particles, the above problem is solved by making only the portion of the drift tube into which a magnet is incorporated thick, and thinning the region without a magnet.

[0013] The shape of both ends of the drift tube is
It has a ring shape protruding inward .

In a conventional drift tube type linac,
The reason that the power efficiency decreases as the drift tube becomes longer is that the capacity between adjacent drift tubes that does not contribute to the formation of the accelerating electric field (A in FIG. 11) increases as the drift tube length increases. It is in.

Therefore, in the present invention, the portion which does not need to incorporate a magnet is made thin, as shown in FIG.
Of the capacitor A, which does not contribute to the formation of.
As is apparent from a comparison between FIG. 1 and FIG. 11, FIG. 1 according to the present invention has an electric field (shown by a solid line E and a broken line F) contributing to beam acceleration, which accounts for the total electric field generated between the drift tubes. (Indicated by solid line E) is high. Therefore, if the thickness of the region of the drift tube without magnets is made as thin as possible, wasteful high-frequency energy is reduced,
Power efficiency can be increased and power consumption can be reduced.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In the first embodiment of the present invention, as shown in FIG. 2, the cross-sectional shape of the drift tube 20 is made thick only at the portion where the quadrupole magnet 26 similar to the conventional example is incorporated, and the region without the magnet is uniform. It has a thin thickness.

According to this embodiment, the capacity not contributing to the formation of the accelerating electric field is minimized, and the power efficiency of the drift tube type linac can be maximized.

Next, a second embodiment of the present invention will be described in detail with reference to FIG.

In the second embodiment, not only the magnet-free region of the drift tube 20 is made thinner, but also the shape of both ends is formed into a ring shape protruding inward to form a desirable electric field. .

According to this embodiment, a favorable electric field can be generated between the drift tubes by accelerating the charged particles.

In the above embodiment, a quadrupole magnet is incorporated in the drift tube, but the type of magnet incorporated in the drift tube is not limited to this.

High-frequency power is applied to a drift tube type linac incorporating the drift tube 20 according to the present invention, and a predetermined resonance mode is excited to efficiently generate an accelerating electric field between the drift tubes 20 so that an on-beam axis is generated. The charged particles passing through are accelerated to a predetermined speed.

In the above description, the Alvaret type linac having the simplest structure has been described as an example.
It is apparent that the application target of the present invention is not limited to this, and the present invention can be similarly applied to a Videley type and an interdigital-H type.

[0025]

According to the present invention, the capacity that does not contribute to the formation of the accelerating electric field can be reduced, and the power efficiency can be improved. Therefore, the high-frequency power required for operating the linac can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining the principle of the present invention.

FIG. 2 is a sectional view showing the first embodiment of the present invention.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a conventional Alvare type drift tube type linac.

FIG. 5 is a perspective view for explaining the operation principle of the drift tube type linac;

FIG. 6 is a sectional view showing a state where an electric field is applied in the beam acceleration direction.

FIG. 7 is a sectional view showing a state where an electric field is applied in the beam deceleration direction.

FIG. 8 is a sectional view for explaining a method of applying a voltage to the drift tube.

FIG. 9 is a longitudinal sectional view showing an example of a sectional shape of a conventional drift tube.

FIG. 10 is a transverse sectional view of the same.

FIG. 11 is a sectional view for explaining a problem of the conventional example.

FIG. 12 is a sectional view showing the configuration of another example of a conventional drift tube.

[Explanation of symbols]

 8 Beam 10 Vacuum tank 20, 22, 24 Drift tube 26 Quadrupole magnet 30 High frequency power supply

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05H 7/22

Claims (2)

(57) [Claims] A plurality of drift tubes each having a magnet incorporated therein are linearly arranged, and a high-frequency voltage is generated between adjacent drift tubes to accelerate charged particles passing through the drift tubes. In a drift tube type linac, a drift tube type linac is characterized in that only a portion of the drift tube where a magnet is incorporated is made thick, and a region without a magnet is made thin. 2. A drift tube type linac according to claim 1, wherein both ends of said drift tube are formed in a ring shape protruding inward .