JP2502377Y2 - Electron beam accelerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electron beam accelerating device for generating an electron beam having a compressed energy width for use in a free electron laser or the like. The present invention relates to an electron beam accelerator capable of suppressing the spread.

[Prior Art] Generally, in a free electron laser device or the like, an electron beam having a small energy width is used to satisfy a laser oscillation condition. Therefore, the electron beam accelerator applied to this type of device needs to generate an electron beam having a sufficiently compressed energy width.

FIG. 4 shows, for example, “Nuclear Device and Method (Nucl.Instr.and
Meth.) "(153, 1978) 343-346,
It is a block diagram which shows the conventional electron beam acceleration device with a free electron laser device.

In the figure, (1) is an electron gun that emits an electron beam E,
(2) is a pre-buncher that focuses the electron beam E, (3) is a focusing coil that focuses the focused electron beam E, (4) is a buncher accelerating tube that further focuses and accelerates the focused electron beam E ( Reference numeral 5) is a regular accelerating tube that further accelerates the electron beam E from the buncher accelerating tube (4) on a linear orbit, and these constitute a linear accelerator for the electron beam E.

(6) to (8) are devanching deflection electromagnets for deflecting the electron beam E from the regular accelerating tube (5) to have a time (phase) spread (devanching) according to energy, The central debunching deflection electromagnet (7) is set to have a double deflection angle and anti-polarity with respect to the inlet side and outlet side debunching deflection electromagnets (6) and (8). (9) is an energy width compression acceleration tube that compresses the energy width of the electron beam E after debunching.

(10) is a klystron that supplies microwaves to the buncher accelerating tube (4), (11) to (13) are power dividers that divide microwaves, (14) to (16) are power dividers (11)
Is a phase shift attenuator that adjusts the phase and electric power of microwaves via (13) to (13) and supplies them to the pre-buncher (2), regular accelerating tube (5) and energy width compression accelerating tube (9).

The above (6) to (16) constitute an electron beam accelerator together with the linear accelerators (1) to (5).

A free electron laser device (20) is supplied with an electron beam E from an electron beam accelerating device, and includes a pair of translucent deflection electromagnets (21) and (22) and deflection electromagnets (21) and (22). Undulators (23) on the straight track between
And a pair of mirrors (24) and (25) arranged so as to face the undulator (23) in the axial direction together with the deflection electromagnets (21) and (22).

FIG. 5 is an explanatory diagram schematically showing the energy width and the phase width of the electron beam E in the phase space.

In the figure, the vertical axis γ is energy and the horizontal axis is phase. (A) is a state before being incident on the devanching deflection electromagnets (6) to (8), and (b) is a devanching deflection electromagnets (6) to (8). ), And (c) is the state after passing through the energy width compression accelerating tube (9).

Next, the operation of the conventional electron beam accelerator will be described with reference to FIGS. 4 and 5.

Cloistron (10) is a power divider (11) ~ (13)
And the pre-buncher (2), buncher accelerating tube (4), and regular accelerating tube (5) via the phase shift attenuators (14) to (16).
, And the energy width compression accelerating tube (9) are supplied with microwaves of required phase and power, respectively.

The electron beam E emitted from the electron gun (1) is focused by the pre-buncher (2), focused by the focusing coil (3), clustered and accelerated by the buncher accelerating tube (4), and then by the regular accelerating tube (5). It is further accelerated and is incident on the debunching deflection electromagnets (6) to (8).

At this time, since the energy of the electron beam E is not constant, the electron beam E incident on the debunching deflection electromagnet (6) is
As shown in FIG. 5 (a), it has a large energy width in the vertical axis γ direction.

This electron beam E is generated by the debunching deflection electromagnet (6)-
By passing through the deflection orbit of (8), a phase corresponding to the energy is obtained, and the phase width is widened in the horizontal axis ψ direction as shown in FIG. 5 (b).

Then, after passing through the energy width compression accelerating tube (9), the fifth
As shown in FIG. 6C, the energy width is compressed in the vertical axis γ direction.

The electron beam E whose energy width has been compressed in this way is supplied to the free electron laser device (20), passes through the undulator (23) between the deflection electromagnets (21) and (22), and passes through the mirror (24).
And laser oscillation of the laser light between (25) is performed.

[Problems to be Solved by the Invention] As described above, the conventional electron beam accelerator uses the debunching deflection electromagnets (6) to (8) and the energy width compression accelerating tube (9) to compress the energy width. Therefore, as shown in FIG. 5 (c), the phase width spreads in the horizontal axis direction,
There is a problem that the current density in the undulator (23) deteriorates and the oscillation efficiency of the free electron laser device (20) decreases.

The present invention has been made to solve the above problems, and obtains an electron beam accelerating device capable of holding the phase width (bunch width) at the same level before the energy width compression when the energy width of the electron beam is compressed. This is the purpose.

[Means for Solving the Problems] An electron beam accelerator according to the present invention is a debunching deflection electromagnet for debunching an electron beam accelerated by a linear accelerator, and a bunching deflection device for compressing the phase width of the electron beam after debunching. An electromagnet, an energy width compression cavity for accelerating and decelerating the electron beam after phase width compression to compress the energy width, and a quadrupole electromagnet for focusing and collimating the energy width compressed electron beam. It is a thing.

[Operation] In this invention, the bunching deflection electromagnet compresses and compensates the spread of the phase width of the electron beam generated during debunching to the same extent as before debunching, and the energy width compression cavity arranged on the exit side of the bunching deflection electromagnet. However, the electron beam is accelerated and decelerated according to the orbital dispersion corresponding to the energy width to compress the energy width, and the electron beam focused by the quadrupole electromagnet is supplied in parallel.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an embodiment of the present invention,
(6), (10) and E are the same as described above. or,
The configuration not shown is as shown in FIG.

Reference numeral (7A) is a debunching deflection electromagnet for debunching the electron beam E together with the debunching deflection electromagnet (6), and is set to have the same deflection angle and antipolarity with respect to the debunching deflection electromagnet (6) on the inlet side. .

(30) is a bunching deflection electromagnet for compressing the phase width of the electron beam E after debunching to compensate to the same extent as before debunching, and (31) is an energy width arranged at the exit side of the bunching deflection electromagnet (30). It is a compression cavity.

Reference numeral (32) is a quadrupole electromagnet provided at the focal position of the bunching deflection electromagnet (30), and the focused electron beam E is collimated and supplied to the free electron laser device (20).

(33) is a power divider for dividing the microwave from the klystron (10), and (34) is for adjusting the phase and power of the divided microwave and supplying it to one end of the energy width compression cavity (31). Phase shift attenuator, (35) is a phase shift attenuator (3
Power divider to further divide the microwave from 4), (3
Reference numeral 6) is a phase shift attenuator for adjusting the phase and power of the microwave divided by the power divider (35) and supplying the same to the other end of the energy width compression cavity (31).

FIG. 2 is an explanatory view showing the energy width compression characteristic of the energy width compression cavity (31), and the linear portion of the acceleration / deceleration characteristic of the electron beam E, which is a sine curve, is used for energy width compression.

FIG. 3 is an explanatory view schematically showing the energy width and the phase width of the electron beam E in the phase space as in FIG.
Is a state before being incident on the debunching deflection electromagnets (6) and (7A), (b) is a state after passing through the devanching deflection electromagnets (6) and (7A), and (c) is an energy width compression cavity (31). ) Is the state after passing.

Next, the operation of one embodiment of the present invention will be described with reference to FIGS.

Similar to the above, the electron beam E after passing through the linear accelerator
Has a large energy width in the vertical axis γ direction as shown in FIG.

By passing through the deflection orbits of the debunching deflection electromagnets (6) and (7A), this electron beam E has a phase corresponding to the energy, and as shown in FIG. The width can be widened. At this time, since the length of the deflection trajectory is half of the above, the spread of the phase width is also half of that in the case of FIG. 5 (b).

The electron beam E that has passed through the debunching deflection electromagnets (6) and (7A) undergoes energy dispersion according to the difference from the central energy, and the orbits thereof are parallel electron beams.
At this time, the phase width also increases corresponding to the energy of the electron beam E. Here, the minimum energy electron beam is indicated by E _MIN , the central energy electron beam is indicated by E _C , and the maximum energy electron beam is indicated by E _MAX .

The electron beam E debunched in this way passes through the bunching deflection electromagnet (30), and the phase width is compressed while maintaining dispersion due to the energy difference.

That is, the bunching deflection electromagnet (30) deflects the electron beam E so that the electron beam having a larger energy has a longer orbit and compensates for the expansion of the phase difference, and makes the phase width as small as the width before debunching. Therefore, the electron beam E after the phase width compression
Is compensated to a phase width similar to that of FIG. At this time, each electron beam E _MIN , E _C and E _MAX due to energy dispersion
The orbital position of is retained.

Next, the electron beam E passes through the energy width compression cavity (31) arranged on the exit side of the bunching deflection electromagnet (30). At this time, as shown in FIG.
_MIN is accelerated to the maximum, maximum energy electron beam E _MAX is decelerated to the maximum, and central energy electron beam E _C passes through without being accelerated or decelerated.

Therefore, the electron beam E after passing through the energy width compression cavity (31) is converged near the central energy as shown in FIG. 3 (c), and the energy width is compressed in the vertical axis γ direction. At this time, since the phase width has been compressed by the bunching deflection electromagnet (30) in advance, the phase width in the horizontal axis direction does not widen. In this way, the electron beam E having a large energy width obtained from the linear accelerator is compressed into an energy width and a phase width applicable to the free electron laser device (20).

Finally, the electron beam E whose phase width and energy width are compressed
Is incident on the quadrupole electromagnet (32), but the quadrupole electromagnet (32)
Since the center position of is the focal point of the bunching deflection electromagnet (30), the electron beam E is focused on a parallel orbit and supplied to the free electron laser device (20).

In the above embodiment, the case where the electron beam E is supplied to the free electron laser device (20) has been described, but the same operational effect can be obtained even when used as a radiation source for a low energy positron diffraction device or a positron microscope. Needless to say.

As described above, according to the present invention, the debunching deflection electromagnet for debunching the electron beam accelerated by the linear accelerator, the bunching deflection electromagnet for compressing the phase width of the electron beam after debunching, and the phase An energy width compression cavity for accelerating and decelerating the width-compressed electron beam to compress the energy width, and a quadrupole electromagnet for converging and collimating the energy width-compressed electron beam are provided. Since the energy width and the phase width are simultaneously compressed, the density of the bunched electron beam is increased, and an electron beam accelerating device capable of supplying an electron beam applicable to a free electron laser device or the like is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the essential parts of an embodiment of the present invention, and FIG.
1 is an explanatory view showing the characteristics of the energy width compression cavity in FIG. 1, FIG. 3 is an explanatory view showing the energy width and phase width of an electron beam according to the present invention in a phase space, and FIG. FIG. 5 is a configuration diagram showing a conventional electron beam accelerator, and FIG. 5 is an explanatory diagram schematically showing the energy width and phase width of an electron beam by the conventional apparatus in a phase space. (1) ... Electron beam source, E ... Electron beam (5) ... Regular accelerating tube (6), (7A) ... Debunching deflection electromagnet (30) ... Bunching deflection electromagnet (31) ... Energy width compression cavity (32) ... Quadrupole electromagnet In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Scope of utility model registration request] 1. A linear accelerator including an electron beam source, a debunching deflection electromagnet for debunching an electron beam accelerated by the linear accelerator, a bunching deflection electromagnet for compressing the phase width of the electron beam after debunching, and a phase. An electron beam provided with an energy width compression cavity for accelerating and decelerating the width-compressed electron beam to compress the energy width, and a quadrupole electromagnet for focusing and collimating the energy width-compressed electron beam. Accelerator.