JPH06101399B2 - Beam closed orbit correction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a beam closed orbit correction device for an accelerator, and particularly to a highly accurate automatic correction of electron beam position of an accelerator for industrial use such as synchrotron radiation generation. The present invention relates to a beam closed orbit correction device suitable for

[Conventional technology]

In a small accelerator used for generating synchrotron radiation, an electron beam is accelerated by a high frequency, and a closed orbit of the beam is formed by a magnetic field of an electromagnet. For this,
Excitation current control of the electromagnets arranged around the closed orbit is performed accurately, but the high frequency acceleration frequency (frequency of high frequency for acceleration) also affects the accuracy of the closed orbit. Conventionally, there has been a method in which the high-frequency acceleration frequency is always controlled to be a constant value, or frequency control is performed based on the radial deviation detected at the beam monitor installation point and the beam rotation speed.

[Problems to be solved by the invention]

For the electromagnets that compose the accelerator, it is required that the leakage magnetic field to the outside be minimized in addition to high homogeneity of the magnetic field, and the optimal design of the electromagnet system is made. It is impossible to do so, and this stray magnetic field is one of the causes of deviation of the beam closed orbit.

However, in the conventional accelerator, the countermeasure against the effect of the stray magnetic field has not been taken independently, and the effect of other factors has been taken into consideration by manually adjusting the excitation of the steering electromagnet. For this reason, the adjustment becomes complicated and a very long adjustment period is required.

An object of the present invention is to provide a beam closed orbit correction device that corrects the deviation of the closed orbit due to the stray magnetic field and eliminates the above-mentioned problems of the prior art.

[Means for solving problems]

The above purpose corresponds to the magnitude of the exciting current of the electromagnet,
When the value of the acceleration frequency that minimizes the deviation of the beam closed orbit due to the stray magnetic field is called the optimum frequency, a data table for storing the optimum frequency value for each exciting current value of the electromagnet and For the excitation current pattern determined by the above, the memory means is provided for reading the optimum frequency at each control time point of the pattern from the data table, generating the optimum frequency pattern corresponding to the pattern, and storing the optimum frequency pattern. Is achieved by

[Action]

When the value of the exciting current of the electromagnet is fixed and the acceleration frequency is changed, the deviation of the beam closed orbit changes. Since there is an acceleration frequency that minimizes this deviation, that is, an optimum frequency, this is calculated in advance using a calculation model for each exciting current value and stored in the data table. By referring to this table, the time series of the optimum frequency is obtained for the excitation current pattern (curve of the excitation current with time) given to the operating state of the accelerator at that time, and this is stored in the memory. If the reading frequency control target value is controlled in synchronization with the change in the exciting current, the deviation of the closed orbit due to the leakage magnetic field can be optimized.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In the figure, the accelerator is composed of a deflection electromagnet 6, a quadrupole electromagnet 9, a high frequency acceleration cavity 4, etc., and the deflection electromagnet 6 is excited by an electromagnet power source 8 controlled by an electromagnet power source control device 7. The high-frequency acceleration cavity 4 is supplied with high-frequency power from a high-frequency acceleration power source 10 controlled by a high-frequency acceleration control device 5 to accelerate the beam.

In the high-frequency acceleration control device 5, and the set value f _o commanded from the rf frequency setting circuit 1, a high frequency acceleration frequency measurement
and f _m by butt-jointing the subtractor 12, performs frequency control.

A data table 2 is provided in the high frequency acceleration frequency setting circuit 1. As will be described later, the high-frequency acceleration frequency (optimum frequency) that is optimized over the entire circumference of the accelerator in the beam closed orbit due to the stray magnetic field is obtained by calculation in advance for each reference bending electromagnet excitation current, and the table 2 Stored as the optimum frequency. Further, similarly, as described later, by actually fetching the exciting current signal J flowing in the deflection electromagnet 6 and referring to the data table 2, the optimum frequency for each control cycle of the high frequency acceleration frequency is automatically generated, and Is stored in the memory 3 as high frequency acceleration optimum frequency pattern data. The contents of the memory 3 are sequentially synchronized by the timing system 11 in synchronization with the control cycle.
To the high-frequency acceleration control device 5 is outputted as a high-frequency acceleration frequency setting value f _o, the frequency control is performed.

Next, a method of creating the optimum frequency reference data table 2 will be described. It is the magnetic field that determines the orbit of the beam, and therefore, the excitation current of the electromagnet required to generate a predetermined magnetic field is required to have high accuracy and high stability. Second
The figure shows an example of the excitation current pattern of the deflection electromagnet 6. It is operated repeatedly in this pattern. Power control time t ₁
Then, the reference exciting current J is J ₁ , and similarly t ₂ to t _n correspond. During acceleration, the magnitude of the stray magnetic field changes with the change of the exciting current J, and accordingly, the deviation of the beam closed orbit also changes.

FIG. 3a is an example of the result of calculation of the deviation of the beam closed orbit when the bending magnet exciting current is I _{1 over} the entire circumference of the accelerator with the high-frequency acceleration frequency as a parameter. As shown in this figure, there is a high-frequency acceleration frequency f ₁ that optimizes the deviation of the beam closed orbit when the deflection magnet exciting current is I ₁ . Similarly, FIG. 3b is an example of the result of calculating the deviation of the beam closed trajectory when the bending magnet exciting current is I ₂ , and the optimum frequency is f ₂
Becomes Such optimum frequencies f _{1 to} f _n are obtained and stored in the data table 2 of FIG. 1 as reference data.

Next, the direction in which the high frequency acceleration optimum frequency pattern is created will be described. The operation case of the accelerator is not fixed in one way, but the deflection electromagnet excitation current pattern generally changes accordingly, and the optimum high-frequency acceleration frequency pattern also changes with this. Come on.

To deal with this, in FIG. 1, the optimum frequency corresponding to this data is obtained from the exciting current value J actually flowing in the electromagnet by referring to the data table 2. That is, when the measured excitation current value at the power supply control time t ₁ is J ₁ , the optimum frequency for the excitation current value closest to J ₁ is referred to as the optimum frequency F ₁ at this time by referring to the data table 2. If J ₁ is closest to I ₁ , then the optimum frequency F ₁ = f ₁ . Similarly, the optimum frequency F ₂ to F _n corresponding to the excitation current measurement side J ₂ through J _n in the control time t ₂ ~t _n is determined, which is stored in the memory 3 as the high-frequency accelerating optimum frequency pattern. FIG. 4 shows an example of this pattern.

As described above, even if the excitation pattern of the deflection electromagnet 6 changes, the high frequency acceleration optimum frequency pattern can be automatically generated. Then, as described above, the content of the high-frequency accelerating optimum frequency pattern memory 3, in synchronization with the control cycle by a command from the timing system 11, by providing a frequency control setting value f _o to the high-frequency acceleration control device 5, leakage Optimal frequency control that corrects the deviation of the closed orbit due to the magnetic field can be performed.

〔The invention's effect〕

According to the present invention, it is possible to automatically and optimally correct the deviation of the beam closed trajectory due to the magnetic field at the time of acceleration, so that there is an effect that the adjustment can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of an exciting current pattern of a deflection electromagnet, FIG. 3a and FIG.
FIG. 3b is a diagram exemplifying the result of simulating the high frequency acceleration frequency dependence of the closed orbit deviation due to the stray magnetic field, and FIG. 4 is a diagram showing an example of the high frequency acceleration optimum frequency pattern. 1 ... High-frequency acceleration frequency setting circuit, 2 ... Data table,
3 ... Optimal frequency pattern memory, 4 ... High frequency acceleration cavity,
5 ... High-frequency acceleration control device, 6 ... Bending electromagnet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akinori Shibayama, 3-1, Morinosato Wakamiya, Atsugi City, Kanagawa Prefecture, Atsugi Telecommunications Research Laboratories, Nippon Telegraph and Telephone Corporation (72) Masayuki Nakajima, 3-1, Wakamiya Morinosato, Atsugi City, Kanagawa Japan Telegraph and Telephone Corporation Atsugi Electro-Communication Research Laboratory

Claims (1)

[Claims] 1. A path of a beam accelerated by a high frequency is electrically charged.
Beam closed track formed by controlling the magnetic field generated by a magnet
Beam closed track to compensate for road offset due to stray magnetic fields
In the road correction device, the above calculated using the calculation model
Optimum frequency of the above high frequency that minimizes the deviation of the beam closed orbit
Number for each exciting current value of the electromagnet, and predict the result.
Data table to be stored for each control point
The optimum frequency for the detected value of the exciting current of the electromagnet
From the above data table,
And the pattern memory to store it at each control point
Read the optimum frequency corresponding to each from the pattern memory
And set this as the set target value to control the above high frequency.
A high frequency control means for controlling the bee
Closed orbit correction device.