JPH0719679B2 - Storage beam current stabilization control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stabilizing accumulated beam current in a ring for acceleration and accumulation used in a light source for semiconductor lithography and a beam accumulation ring of full energy injection type.

[Conventional technology]

In recent years, the use of synchrotron radiation as a light source for lithography and a light source for medical X-ray fluoroscopy that replaces ultraviolet rays is expected. This is because the synchrotron radiation has a continuous spectrum and contains strong and highly directional soft X-rays. Such soft X-rays are X-rays of lithography technology from the viewpoint of throughput and resolution. This is because it is ideal as an X-ray source for medical fluoroscopy.

FIGS. 3 (a) and 3 (b) show when electrons orbiting in the orbit of the ultrahigh vacuum ring (5) (50) at a speed close to the speed of light are deflected by the deflection electromagnet (51). The outline of the synchrotron radiation facility that emits synchrotron radiation is shown. Of these, FIG. 1A shows a device configuration of the acceleration / accumulation / combining ring (50), which is expected mainly as an industrial light source, which enables downsizing of the device. In the injection mode, the beam injected into the ring (50) in a low energy state from the beam injector (10) such as an electronic linac is the ring (50).
Accelerated while orbiting inside to reach a high energy state,
Further, the output of the synchrotron radiation emitted during the orbit increases due to the increase in the energy.

On the other hand, the one shown in FIG. 2B is a synchrotron radiation facility consisting of a full-energy injection type ring structure constructed for medium and large-scale research facilities assuming that the beam life is longer than that of the ring structure. is there. 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. The beam accelerated to the state is incident on the next beam storage ring (5) and circulates in the ring (5) for a long time while retaining its energy, while synchrotron radiation is kept for a long time. Radiate.

[Problems to be solved by the invention]

In the above two beam orbiting rings (5) (50), in order to raise the beam current value in the ring from a zero state to a predetermined high current value (reference value described later) in a short time,
Usually, the beam is injected with the capability (full incident beam current value and shortest period) close to the limit of the beam injector system provided in these rings.

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, the beam current is attenuated at a very slow speed unless additional incidence or the like is performed, but the beam current is in a stable state and synchrotron radiation light can be obtained for a long time. Therefore, in this mode, control is usually performed so that the attenuation of the beam current is minimized.

[Problems to be solved by the invention]

In the above-mentioned initial injection mode, beam injection is performed with high efficiency until the beam current reaches a predetermined reference value. Normally, the incident beam current value per incident is very large and the incident cycle is extremely short. Therefore, once the beam current value rises close to the reference value, there is almost no attenuation of the beam current until the next incidence, so when the next incidence occurs, the reference value is far exceeded. There was something that happened.

Even if the mode is changed to the accumulation mode after the beam current value slightly exceeds the reference value in this way, it takes a considerable time until the level is lowered to the reference value (for example, the beam life is 8 hours). If the reference value is set to 200 mA and the reference value is exceeded by about 10 mA, it takes about 24 minutes to decay to 200 mA). Therefore, the output of the synchrotron radiation generated during that time far exceeds the radiation output generated at the reference value, and the desired radiation output cannot be stabilized. When using it, the exposure time must be changed.

The present invention was devised in view of the above problems of the prior art. The incident condition of beam incidence in the initial incidence mode is changed immediately before the beam current value reaches the reference value, and the incident beam current value is changed to the reference value. It is something that tries not to exceed.

[Means for solving problems]

Therefore, the stored beam current stabilization control method of the present invention is a beam orbiting ring which has a beam injector and which generates synchrotron radiation while the incident beam orbits,
The beam current is detected, or the output of the emitted light emitted from the ring is detected, and the detected beam current value or the detected beam current value in the initial incidence mode in which the beam is incident at a predetermined incident beam current value and trigger signal timing. The incident beam current value and / or the trigger signal timing is changed immediately before the beam current value obtained from the detected synchrotron radiation output reaches a reference value, and then the detected beam current value or the beam current value obtained from the synchrotron radiation output is changed. The basic feature is that the mode is changed to the accumulation mode at the time when reaches the reference value.

In the above-mentioned configuration, the reference value means that the intensity of the synchrotron radiation emitted from the beam orbiting ring is X-ray exposure or X-ray exposure.
It refers to the beam current value when it is in a state suitable for line transmission and can be stably obtained. In normal accumulation mode, the beam current value is adjusted around this reference value to operate stably for a long time. The control will be performed.

In the present invention, control such as lowering the incident beam current value is performed as one method of changing the beam incident condition immediately before the beam current reaches the reference value. The control is mainly performed by adjusting the beam injection efficiency in the beam injector system and the beam orbiting ring. In the electron linac of the beam injector system, the voltage applied to the klystron is adjusted, the RF frequency of the klystron is also adjusted, and the steering magnetic field control is performed. , And by controlling the timing of beam emission from the linac (the same adjustment will be made when the beam is extracted from the microtron).
In the (Low energy Beam Transfer) system, the bending magnet (Be
nding magnet) and steering magnetic field control and wire grid control. For electronic synchrotrons, voltage adjustment and timing adjustment for inflectors, pertabeta, deflectors, kickers, etc., steering magnetic field control, and further HBT (High energy Beam Transfer) In the system, in addition to adjusting the magnetic field of the BM and steering, in addition to the acceleration and storage ring and the beam orbiting ring such as the beam storage ring, the voltage and timing of the inflector and pertabeta are adjusted. By these adjustments, the incidence efficiency of the beam on the beam orbiting ring is greatly influenced.

On the other hand, another method of changing the beam incidence condition is to perform control such as delaying the trigger signal timing in beam incidence (lengthening the signal period). That is, when the time from one incidence to the next incidence becomes long, the beam current is attenuated to some extent during that time, so that the beam current value in the ring rises gradually even after the next incidence.

Of course, the above two methods may be combined and implemented. Further, these incident conditions are not limited to being changed once, but may be changed in multiple steps. With such control, the rising curve of the beam current value in the initial incidence mode gradually becomes gentle, and the detected beam current value or the beam current value obtained from the detected synchrotron radiation output does not significantly exceed the reference value. . Therefore, when these detected values reach the reference value, the mode is changed and the storage mode is entered.

〔Example〕

 Specific examples of the present invention will be described below.

FIG. 1 shows an outline of an implementation configuration of the method of the present invention in a synchrotron radiation facility of a full energy incidence type. In the figure, (1) to (4) are beam injector systems for accelerating an electron beam, of which (1) is an electron linac and (2) is
LBT, (3) is an electron synchrotron, and (4) is an HBT. Further, (5) is a beam storage ring for injecting an accelerated electron beam from the beam injector system and causing it to orbit within it to obtain synchrotron radiation.

In this embodiment, a beam current monitor (6) for detecting the accumulated beam current in the orbit of the beam accumulation ring (5).
Is installed, and the detected value is input to the control calculator (7) described later. The operation of each component of the beam injector system and the beam storage ring (5) is controlled by the control calculator (7). In particular, a trigger signal is output from the control calculator (7) based on the signal period generated by the cycle signal generator (8) including the master oscillator (8a), whereby the beam injector system for beam injection and The operation of the storage ring (5) is controlled. or
The second BM (deflection electromagnet) of the LBT (2) is provided with magnetic field control means capable of adjusting the magnetic field by variably controlling the applied current, and the applied current is controlled by the control calculator (7). By doing so, the efficiency of beam incidence on the beam storage ring (5) can be changed.

With this control calculator (7), 3.2
180 mA for 2 minutes at a rate of 5 mA / incident once a second
Accumulated beam current up to weak (current rising speed is 90mA / min
Is). When the beam current value reaches 180 mA by detecting the beam current by the current monitor (6), the control calculator (7) adjusts the magnetic field of the second BM of the LBT (2).
The injection efficiency was reduced to 1 mA / injection (as a result, the current rising speed was 20 mA / min). As a result, the mode is changed when the detected beam current value is approximately 200 mA,
Changed to accumulation mode without significantly exceeding mA. The control accuracy at this time was ± 1 mA.

FIGS. 2 (a) and 2 (b) are graphs showing the beam current detection results obtained in the above Example and graphs showing the beam current detection results when the method of the present invention was not carried out in exactly the same equipment. It is a figure. From these graphs, it is understood that the change of the beam injection condition at the time of the initial injection by the method of the present invention is very excellent in the stability of the beam current immediately after the mode is changed to the accumulation mode.

〔The invention's effect〕

As described above in detail, according to the accumulated beam current stabilization control method of the present invention, the beam current value in the ring may greatly exceed the reference value due to the change of the incident condition of the incident beam in the initial injection mode. Therefore, the beam current immediately after the mode is changed to the accumulation mode is stably controlled to a substantially reference value.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of a full energy injection type synchrotron radiation facility of an embodiment to which the method of the present invention is applied, and FIG. 2 (a).
FIG. 3B is a graph showing the transition of the detected beam current value in the beam storage ring of the synchrotron radiation facility when the method of the present invention is carried out and when it is not carried out. FIG. FIG. 3 is an explanatory diagram showing a device configuration example, and FIG. 6B is an explanatory diagram showing a full energy injection type ring configuration example. In the figure, (1) is electronic linac, (2) is LBT, (3)
Is an electron synchrotron, (4) is an HBT, (5) is a beam storage ring, (6) is a beam current monitor, (7) is a control calculator, (8) is a cycle signal generator, and (8a) is a master oscillator. Shows each.

Claims (1)

[Claims] 1. A radiant light which has a beam injector and which detects a beam current thereof or is radiated from the ring by a beam orbiting ring which generates synchrotron radiation light while the incident beam orbits. Output is detected, and the beam current value obtained from the detected beam current value or the detected synchrotron radiation output reaches the reference value in the initial incidence mode in which the beam is incident at a predetermined incident beam current value and trigger signal timing. Immediately immediately before, the incident beam current value and / or the trigger signal timing is changed, and then the mode is changed to the accumulation mode when the detected beam current value or the beam current value obtained from the emitted light output reaches a reference value. A method of stabilizing a stored beam current, which is characterized in that