JPH0443600A - Control for stabilizing accumulated beam current - Google Patents

Abstract

PURPOSE:To prevent an incidental beam current from exceeding a reference value by changing an incidental beam current value/trigger signal timing just before the beam current value reaches the reference value, and changing into an accumulation mode when it reaches the reference value. CONSTITUTION:A beam current monitor 6 for detecting an accumulated beam current is installed in a rounding track of a beam accumulation ring 5, and its detection value is inputted to a control and design computer 7. Just before the detected beam current value reaches a reference value in an initial incidence mode where a beam incidence is performed for a predetermined incidental beam current value and a trigger signal timing, the incidental beam current value and/or the trigger signal timing are changed, and the mode is changed into an accumulation mode when the detected beam current value reaches the reference value. The beam current value in the ring can thus be prevented from exceeding the reference value largely, thereby a stable control is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a storage beam current stabilization control method in an acceleration storage ring and a full-energy incidence type beam storage ring used in a light source for semiconductor lithography.

[Conventional technology]

In recent years, synchrotron radiation has been expected to be used as a lithography light source and a medical X-ray fluoroscopy light source in place of ultraviolet light. This is because synchrotron radiation has a continuous spectrum and contains powerful and highly directional soft X-rays, and these soft X-rays are the This is because it is ideal as a radiation source and as an X-ray source for medical fluoroscopy.

Figures 3(a) and 3(b) show ultra-high vacuum rings (5) (50
) shows an outline of a synchrotron radiation facility that emits synchrotron radiation when electrons orbiting at a speed close to the speed of light are deflected by a deflection electromagnet (51). Of these, FIG. 2(a) shows the device configuration of an acceleration/storage ring (50) that is expected to be used primarily as an industrial light source that can reduce the size of the device. In the incident mode, a beam injected into the ring (50) in a low energy state from a beam injector (10) such as an electron linac is accelerated while circulating in the ring (50) and reaches a high energy state, Furthermore, the output of the synchrotron radiation light emitted during this rotation increases due to the increase in energy.

On the other hand, same 1i! The one shown in (b) is a synchrotron radiation facility with a full-energy incidence ring configuration, which is constructed for medium- to large-scale research facilities because the beam life is longer than that of the ring configuration. In this example, in addition to an electron linac (1) as a beam injector, an acceleration ring such as an electron synchrotron (3) used only for beam acceleration is used, and in the injection mode, the acceleration ring generates full energy. The beam, which has been accelerated to a state of radiate.

[Problem that the invention seeks to solve]

The above-mentioned beam orbiting rings (5) and (50) are usually used in order to raise the beam current value in the rings from zero to a predetermined high current value (reference value to be described later) in a short period of time. The beam is injected at a capacity (full incident beam current value and shortest period) that is close to the limit of the beam injector system provided by the ring.

Then, when the beam current value reaches approximately the reference value, the mode is changed, and the above-mentioned initial incidence mode is changed to the accumulation mode. In the accumulation mode, unless additional injection is performed, the beam current attenuates at a very slow rate, but becomes stable, and synchrotron radiation can be obtained for a long time. Therefore, in this mode, control is normally performed to minimize beam current attenuation.

[Problem that the invention seeks to solve]

In the above-mentioned initial injection mode, highly efficient beam injection is performed until the beam current reaches a predetermined reference value, and the incident beam current value per injection is usually very large and the injection period is also extremely short. Therefore, once the beam current value rises to near the standard value, there is almost no attenuation of the beam current until the first incidence, and therefore, when the next incidence occurs, it will far exceed the standard value. There were times when I ended up.

Even if the mode is changed to accumulation mode after the beam current value has far exceeded the reference value, it will take a considerable amount of time for the level to drop to this reference value (for example, if the beam life is reduced to 8 hours). Assuming that the standard value is 200mA, if the standard value is exceeded by about 10mA, the 200mA
Therefore, the synchrotron radiation output generated during that time far exceeds the synchrotron radiation output generated at the reference value, and the target synchrotron radiation output is not reached. As a result, stability cannot be obtained, and when the light source is used as a semiconductor exposure light source, the exposure time must be changed.

The present invention has been devised in view of the above-mentioned problems of the prior art, and it changes the incident conditions for beam incidence in the initial incidence mode just before the beam current value reaches the reference value, so that the incident beam current value reaches the reference value. The aim is to avoid exceeding the limit.

[Means for solving problems]

Therefore, the accumulated beam current stabilization control method of the present invention uses a beam circulation ring that has a beam injector and generates synchrotron radiation while the incident beam circulates.
Detecting the beam current or detecting the output of the synchrotron radiation emitted from the ring, and detecting the detected beam current value or Immediately before the beam current value obtained from the detected synchrotron radiation output reaches the reference value, the incident beam current value and/or the trigger signal timing are changed, and then the beam current value obtained from the detected beam current value or the synchrotron radiation output is changed. The basic feature is that the mode is changed to the accumulation mode when the value reaches a reference value.

In the above configuration, the reference value means that the intensity of the synchrotron radiation light emitted from the beam orbiting ring is
This refers to the beam current value when the state is suitable for line transmission and can be stably obtained. In normal accumulation mode, the beam current value is adjusted to around this reference short value and stable operation is performed for a long period of time. This will be controlled as follows.

In the present invention, one method of changing the beam incidence conditions immediately before the beam current reaches the reference value is to perform control such as lowering the incident beam current value. This control is mainly performed by adjusting the beam incidence efficiency in the beam injector system and the beam orbiting ring, and in the electronic linac of the beam injector system, adjustment of the voltage applied to the klystron, adjustment of the RF frequency of the klystron, and control of the magnetic field of steering are performed. This is done by controlling the emission timing of the beam from the linac, etc. (approximately the same adjustment is made when extracting the beam from the microtron), and
BT (Low energy Beam Trans
In the fer) system, a bending electromagnet (Bending Magnet)
net) and steering magnetic field control and control by putting in and out wire grids, and in electronic synchrotrons, voltage adjustment and timing adjustment for inflectors, perturbators, deflectors, kickers, etc., steering magnetic field control, etc. Furthermore, HB T (High Energy Beam
In the transfer system, this is done by adjusting the magnetic field of the BM and steering, and in addition, by adjusting the voltage and timing of the inflector and perturbator in beam circulation rings such as the acceleration storage ring and the beam storage ring.

These adjustments greatly affect the incidence efficiency of the beam in the beam circulation ring.

On the other hand, another method of changing the beam incidence conditions is to perform control such as delaying the trigger signal timing (lengthening the signal period) during beam incidence. That is, as the time between one injection and the next injection becomes longer, the beam current attenuates somewhat during that time, so that even if there is a next injection, the beam current value in the ring will rise only gradually.

Of course, the above two methods may be implemented in combination, and the changes in these injection conditions are not limited to one implementation, but may be performed in multiple stages, and with this kind of control, during the initial incidence mode. The rising curve of the beam current value gradually draws a gentle curve, and the beam current value obtained from the detected beam current value or the detected radiation output does not significantly exceed the reference value. Therefore, when these inspection values reach the reference values, the mode is changed and the mode is shifted to the accumulation mode.

〔Example〕

Specific examples of the present invention will be described below.

FIG. 1 shows an outline of the implementation configuration of the present invention method in a full-energy incidence type synchrotron radiation facility. In the figure, (1) to (4) are beam injector systems that accelerate the electron beam, of which (1) is an electron linac, (2) is an LBT, (3) is an electron synchrotron, and (4) is an HBT.
It is. Further, (5) is a beam storage ring which receives an accelerated electron beam from the beam injector system and rotates the electron beam therein to obtain synchrotron radiation light therefrom.

In this embodiment, a beam current monitor (6) detects the accumulated beam current during the orbit of the beam storage ring (5).
is installed, and its test height value is input into a control calculator (7) to be described later. Also, the beam injector system and beam storage ring (
The operation of each component 5) is controlled by a control calculator (7). Especially the master oscillator (8
A trigger signal is output from the control calculator (7) on the basis of the signal period generated by the cycle signal generator (8) with a), which causes the beam injector system and the storage ring ( 5) operation is controlled. Also L
The second BM (bending electromagnet) of B T (2) is equipped with a magnetic field control means that can adjust the magnetic field by variably controlling the applied current, and the control calculator (7) adjusts the applied current. Through control, the beam incidence efficiency to the beam storage ring (5) can be changed.

With this control calculator (7), in the initial incidence mode, 3.
The beam current was accumulated at a rate of 180 mA for 2 minutes at a cycle of once every 2 seconds and at a rate of 5 mA/person (the current rising rate was 90 mA/win).

When the beam current value reaches 180 mA by detecting the beam current by the current monitor (6), the control calculator (7)
adjusted the magnetic field of the second BM of L B T (2) and lowered its incidence efficiency to 1 mA/injection (as a result, the current rising speed was 20 mA/win), and as a result, the detection The mode change was performed when the beam current value was approximately 200 mA, without significantly exceeding 200 mA.

Changed to accumulation mode. The control accuracy at this time is ±1m
It was A.

Figures 2 (a) and 2 (b) are graphs showing the beam current detection results obtained in this example, and graphs showing the beam current detection results when the method of the present invention was not carried out using the same equipment. It is a diagram. From these graphs, it can be seen that changing the beam incidence conditions at the time of initial incidence according to the method of the present invention is very superior in terms of stability of the beam current immediately after the mode is changed to the accumulation mode.

[Effects of the Invention] As detailed above, according to the accumulated beam current stabilization control method of the present invention, the beam current value in the ring can be significantly increased from the reference value by changing the incident conditions of the incident beam in the initial incidence mode. Since the beam current is never exceeded, the beam current immediately after the mode change to the accumulation mode is stably controlled to approximately the reference value.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an overview of a full-energy incidence type synchrotron radiation facility according to an embodiment to which the method of the present invention is applied, and Fig. 2(a)
(b) is a graph showing the transition of the detected beam current value in the beam storage ring of the above synchrotron radiation facility when the method of the present invention is implemented and when the method of the present invention is not implemented. An explanatory diagram illustrating an example of the device configuration. FIG. 3B is an explanatory diagram illustrating an example of the ring configuration of the full-energy incidence method. In the figure, (1) is an electronic linac, and (2) is an LBT. (3) is an electron synchrotron, (4) is an HBT, (5)
is the beam storage ring, (6) is the beam current monitor, and (7) is the beam storage ring.
) is a control calculator, (8) is a cycle signal generator, (8a
) indicates the master oscillator.

Claims (1)

[Claims] A beam orbiting ring that has a beam injector and generates synchrotron radiation light while the incident beam orbits, and detects the beam current or detects the radiation emitted from the ring. In addition to detecting the light output, the beam current value obtained from the detected beam current value or the detected synchrotron radiation output is set as a reference value in an initial incidence mode in which beam incidence is performed at a predetermined incident beam current value and trigger signal timing. The incident beam current value and/or the trigger signal timing are changed immediately before reaching the reference value, and then, when the beam current value determined from the detected beam current value or the synchrotron radiation output reaches the reference value, the mode is changed to the accumulation mode. A storage beam current stabilization control method characterized by: