JPH08250299A - Electron beam generating method - Google Patents

Abstract

PURPOSE: To control the number of pulses of an electron beam to a single or a desiring number, wherein the electron beam is synchronized with the frequency, which is a part obtained by dividing RF by an integer wherein RF is accumulated by one time input to an RF bucket which contributes to FEL gain and is formed in an electron accumulating ring of an accelerator. CONSTITUTION: A gate circuit 19' provided with a time adjusting function is installed in an accelerating tube 10 through a klystron 16 in order to adjust the pulses of electron beam synchronized with the frequency of RF to have pulse numbers to be a desiring number corresponding to the necessity and thus the accumulating efficiency and accumulating quantity to an electron accumulating ring are made to be the maximum values. Consequently, monitoring can be carried out sharply and timing adjustment of the RF acceleration in the accelerating tube, phase adjustment, power adjustment, etc., are carried out extremely smoothly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The disclosed technology belongs to the technical field of a method of generating an electron beam in which an electron beam is made to enter a central orbit of a FEL device or the like using an electron storage ring with a short pulse.

[0002]

2. Description of the Related Art As is well known, electron beam generators are attracting attention in many industrial fields such as physics, chemistry, and biotechnology. Among them, high energy physics experimental equipment, synchrotron radiation facility, FEL equipment, It is used as an electron generator in many devices such as positron generators and plasma experimental devices.
For example, in the FEL generator (accelerator) 1 as shown in FIG. 7, the electron storage ring 2 has deflection electromagnets 3, quadrupole electromagnets 3 '... Arranged in a predetermined manner, and the RF cavity 4 is interposed. An undulator 7 is provided between the septum electromagnet 5 and the kicker electromagnet 6, reflection mirrors 8 for generating FEL are externally provided on the extension of the undulator 7, and an accelerating tube is provided from an electron generating mechanism 9 such as an electron gun. A beam transport line 11 via 10 passes through the septum electromagnet 5 and an electron beam passes through the incident orbit defined by the septum electromagnet 5 and the kicker electromagnet 6 and then circulates on the central orbit 12 at a predetermined RF cycle. Has been

In the central orbit 12, the frequency at which the accumulated electron beam bunches 13 and 13 are synchronized (frequency applied to the RF cavity) is the accelerator 1.
The existence of the short-pulse electron beam is allowed only in the tens to hundreds of buckets of the RF bunch (stable region where electrons exist), which is predetermined depending on the type.

Further, in the FEL generator, only the electron beam can obtain the FEL gain in synchronization with the frequency which is the inverse of the integral multiple of the round trip time of the light between the reflection mirrors 8 and 8 '(usually an integer is 1). Therefore, the other electron beam in the RF bucket causes instability such as beam coupled bunch, the energy dispersion is extremely deteriorated among the parameters of the electron beam directly related to the gain of the FEL, the beam size becomes large, and oscillation occurs. There is an inconvenience that the power becomes small.

In addition, there is a big negative point that the deterioration of the reflection mirrors 8 and 8 due to the beam that does not contribute to the gain becomes large and the FEL does not oscillate. Therefore, the beam is only provided to the bucket that contributes to the FEL gain. In order to generate a short electron beam of ns order that can be injected, it has already been used in many facilities and devices.
Short-grid pulse generators with snap-off diodes that use D-MOS transistors as switches to speed up the rise and clip line circuits to shorten the pulse width have already been used in many facilities, and at a prescribed high frequency. Circuits for synchronizing to RF are also used in linac FEL devices and SR optical facilities.

As shown in FIG. 2, the short pulse electron beam has a short pulse electron beam having an order of several nanoseconds on the horizontal axis and the electron beam current on the vertical axis. In the case of a small FEL device, it is necessary to synchronize with an RF cycle of a frequency having a time width of several hundred ns to several tens ns.

[0007]

The single-shot electron beam having a time width on the order of ns has the following problems due to the small total current as shown in FIG. .

First, since an electron beam having a time width on the order of ns of a single shot usually has a small total current,
It is difficult to monitor with a core monitor or the like, and generally, a monitoring device such as a core monitor is interposed between the electron gun and the accelerating tube and the like, but as described above, an electron with a time width of ns order is used. Since the total current of the beam is small, it is difficult to accurately perform the timing adjustment of RF acceleration, the phase adjustment, and the like, and it is extremely difficult to adjust the operation of the klystron or other accelerating tube.

Secondly, in the case of the small-sized storage ring, since the time during which the electron beam can be stored in the bucket 13 has the time for the electron beam to orbit the central orbit 12 a plurality of times, a single shot is required. In the electron beam having a time width of the order of ns, there is a problem that the amount of accumulated beam to the electron storage ring 2 at one time is not large.

On the contrary, the difference from the above single-shot beam is shown in FIG.
As shown in FIG. 3, it is possible to generate a large number of short pulses of the electron beam generated in the incident electron beam generator for the electron storage ring 2 as shown in FIG. Although the generator circuit is provided, the gate circuit in the generator circuit is of a fixed type, and the current amount increases during the acceleration adjustment in the accelerator 1 to facilitate monitoring, but many R
There is a drawback that the storage efficiency cannot be maximized when a short pulse electron beam synchronized with F is incident on the electron storage ring 2 (the storage efficiency referred to here means that the storage efficiency is the same as that in the ring). The ratio of the amount of beam accumulated in the central ring to the amount of incident beam).

For example, as shown in FIG. 3, when 100 pulses are incident on the ring, the beam accumulation time is as shown in FIG. 5, and 97 pulses are not processed. Therefore, there is a demerit that the inside of the device is contaminated with radiation.

[0012]

The object of the invention of this application is the difficulty of monitoring the ns-order short pulse electron beam generating mechanism used in the electron storage ring type accelerator such as the above-mentioned FEL device and SR optical facility based on the above-mentioned prior art. By R
An F adjustment mechanism (power adjuster), a storage efficiency in the electron storage ring, and a problem of poor storage amount are technical problems to be solved. As shown in FIG. As shown in the characteristic graph of the ratio of the accumulated beam to the incident beam on the vertical axis, the accumulation efficiency in the electron accumulation ring, and
It is an object of the present invention to provide an excellent electron beam generation method that can benefit the field of electron beam utilization in the electronic industry by adjusting the number of pulses that maximizes the accumulated amount.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the structure of the invention of this application, which is based on the above-mentioned object and has the above-mentioned object, is an electronic storage ring of an FEL device or an SR light facility. R of 5MHz to 50MHz, which is an integer fraction of the RF frequency supplied by the RF cavity
In order to accumulate a predetermined number of short pulse electron beams in synchronization with the F cycle, an ns (nanosecond) short pulse electron beam is emitted from a single shot to a predetermined number of RF in a short grid pulse generation mechanism of an electron generator such as a linac. A gate circuit with time adjustment is installed between the master pulse generator and the frequency divider from the short grid pulse generator to generate in synchronization with the cycle, and the most suitable monitoring is performed when adjusting the RF power from the klystron or phase adjustment. The number of pulses is increased so as to be performed, and the gate circuit with adjustment time can be adjusted and changed so as to maximize the storage efficiency and the storage amount when entering the storage ring. It is a measure taken.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the invention of this application will be described below with reference to FIGS.

The illustrated embodiment is an embodiment of an electron storage ring type accelerator 1 as an FEL device, and a septum electromagnet 5
The beam transport line 1 for the incident orbit (not shown) formed to be driven by the kicker electromagnet 6 and the central orbit 12 after the beam damping.
A core monitor (not shown) is provided in a circuit provided between the electron gun 9 and the acceleration tube 10 in FIG. 1, and a delay 17 provided side by side with a klystron 16 connected to the acceleration tube 10, 17 is a master pulse generator 1
8 are electrically connected.

The delay circuit 17 'is provided with a gate circuit 19' having a time adjusting function in place of the gate circuit 19 for a conventional fixed type short pulse beam or the like, and is connected to the frequency divider 20.

The frequency divider 20 is R
The signal from the F generator 23 is distributed, the RF frequency from the RF generator 23 is input via the amplifier 22 and the delay 21, and the optical signal / electrical signal converter / electrical signal / optical signal is transmitted via the optical cable. Short grid pulse generator 26 via grid pulse driver 25 via converter 24
It is connected to the electron gun 9 via.

In the above structure, the short grid pulse generator 26 is synchronized with the integral number (harmonic number) 1 of the RF frequency of the electron storage ring 2 by a predetermined number of ns.
A (nanosecond) short pulse grid is generated from the electron gun 9 and the klystron 16 is generated in the acceleration tube 10.
The beam is accelerated by the application of power by the beam transport line 11 through the septum electromagnet 5 and the bump orbit (not shown) formed by the septum electromagnet 5 and the kicker electromagnet 6. Accumulated.

In the meantime, the pulse generation signal input from the master pulse generator 18 via the delay 17 'by the action of the time adjusting gate 19' is changed from a single pulse beam to a preset number of pulse beams via the setting gate action. When the ring is incident, the number of pulses should be adjusted to maximize the accumulation efficiency and amount of accumulated beams, and when adjusting the accelerator, increase the number of pulses to facilitate short pulse monitoring and phase adjustment. Can be done.

Incidentally, FIGS. 5 and 4 are shown correspondingly,
In FIG. 4, three short pulses are shown corresponding to the beam accumulable time shown in FIG. 5, indicating that the accumulation efficiency is good and the accumulation amount is large.

Although not shown, the RF generator 2
It goes without saying that an even better system will be obtained if the RF supplied to 3 and the klystron 16 and the master pulse generator 18 are phase locked.

[0022]

As described above, according to the invention of this application, basically, the electron beam is monitored in the electron generating portion used in many devices such as a high energy physics experimental device, an SR light facility, and a FEL device. The number of ns incident from the beam transport to the septum magnet
Since it is possible to generate a predetermined number of (nanosecond) short pulse electron beams from a single shot, a large number of short pulses can be generated during acceleration adjustment with an accelerator, and monitoring can be performed easily.
The excellent effect that the timing adjustment of RF acceleration in the accelerating tube, the phase adjustment, and the power adjustment can be performed extremely smoothly is exhibited.

In addition, since the accumulation time of the beam in the accumulation ring is the time required for the electron beam to orbit the ring several times, the accumulation efficiency in the ring is good, and a large accumulation amount can be obtained. Played.

As described above, there is an effect that the number of pulses of the electron beam generated from the electron gun can be optimally adjusted.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an electron generating mechanism of an embodiment of the invention of this application.

FIG. 2 is a graph showing a synchronization characteristic of a short pulse electron beam with respect to an RF cycle.

FIG. 3 is a characteristic graph diagram of a conventional fixed gate type pulse time and electron beam current.

FIG. 4 is a graph showing a correspondence relationship of an electron beam current with respect to time in the embodiment of the invention of this application.

FIG. 5 is a graph of the ratio of incident beam of accumulated beam to time.

FIG. 6 is a block diagram of an electron generation mechanism of a FEL device according to the related art.

FIG. 7 is a schematic schematic plan view of a general aspect of an FEL device.

[Explanation of symbols]

 2 Electron storage ring 12 Central orbit 19 Gate circuit 19 'Gate circuit with time adjustment

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Kawai, 118 Futatsuka, Noda City, Chiba Prefecture, Kawasaki Heavy Industries, Ltd., Noda Factory (72) Shinji Hamada, 118 Futatsuka, Noda City, Chiba, Kawasaki Heavy Industries, Ltd. 72) Inventor Tetsuo Yamazaki 1-4-1, Umezono, Tsukuba-shi, Ibaraki Electronic Technology Research Institute, Industrial Technology Institute (72) Inventor Tomohisa Triangle 1-4-1, Umezono, Tsukuba-shi, Ibaraki Industrial Technology Research Institute In-house (72) Iwakazu Yamada, Iwatsu Yamada, 1-4-1, Umezono, Tsukuba-shi, Ibaraki Industrial Technology Research Institute

Claims (2)

[Claims] 1. A pulse time width which is provided along with a grid pulse generation mechanism when a pulse beam having a time width on the order of ns and synchronized with an RF high frequency is generated by using a grid pulser and is made to enter / accumulate the electron storage ring. An electron beam generating method, characterized in that the number of beam pulses generated is adjustable by using an adjustable gate circuit as desired. 2. The RF synchronizing frequency is 5 MHz to 50 MH
The electron beam generating method according to claim 1, wherein z is set.