JP3924624B2 - Synchrotron vibration frequency control device and control method thereof - Google Patents

Description

  The present invention relates to a synchrotron using an induction accelerating cell, and more particularly to an apparatus for controlling a synchrotron oscillation frequency by controlling generation timing of an induced voltage and a control method therefor.

  The synchrotron includes a high-frequency synchrotron and a synchrotron using an induction accelerating cell. FIG. 6 shows the principle of acceleration of charged particles by the high-frequency acceleration cavity 4, and FIG. 7 shows the principle of acceleration of charged particles by the induction acceleration cell.

  The high-frequency synchrotron 16 applies a high-frequency accelerating voltage to charged particles such as protons that have entered the vacuum duct by an incident device by the high-frequency accelerating cavity 4 synchronized with the magnetic field excitation pattern of the deflecting electromagnet that constitutes the high-frequency synchrotron 16. This is a circular accelerator that circulates the design trajectory 2 around the bunches 3 in the vacuum duct while accelerating the charged particles.

  On the other hand, the synchrotron using the induction accelerating cell is a circular accelerator that is different from the high-frequency synchrotron 16 in acceleration method and accelerates by applying an induction voltage by the induction accelerating cell.

  FIG. 6A shows a state in which incident protons orbit around the design orbit 2 of the high-frequency synchrotron 16 as several bunches 3. When the bunch 3 reaches the high frequency acceleration cavity 4, it is accelerated to a predetermined energy level by applying a high frequency acceleration voltage synchronized with the magnetic field excitation pattern.

  Here, the bunch 3 refers to a charged particle group in which the charged particles undergo phase stability and circulate around the design trajectory 2.

  A charged particle is a generic term for “charged particles” in which certain elements in the periodic table of elements start with ions and electrons in a certain positive or negative valence state. Furthermore, charged particles include particles having a large number of constituent molecules such as compounds and proteins.

  FIG. 6B shows the relationship between the bunch 3 and the applied high-frequency acceleration voltage 4b. The horizontal axis t represents the temporal change in the high-frequency acceleration cavity 4. The vertical axis v is the voltage value of the high frequency 4a. Vofs is a high-frequency acceleration voltage value 4c necessary for accelerating the bunch 3 calculated from the gradient (time change rate) of the magnetic field excitation pattern of the deflection electromagnet at a certain moment of acceleration.

  A voltage required for acceleration is applied to the bunch 3 as a high-frequency acceleration voltage 4b calculated from the gradient (time change rate) of the magnetic field excitation pattern of the deflection electromagnet. The high-frequency acceleration voltage 4b has both a function of applying a voltage necessary for accelerating the bunch 3 and a confinement function of preventing the bunch 3 from diffusing in the traveling axis direction.

  When accelerating the bunch 3 with the high-frequency synchrotron 16, these two functions are indispensable. The time zone of the high-frequency acceleration voltage 4b having these two functions is limited, and it has been known that the time zone shown in gray cannot be used for acceleration in the high-frequency acceleration cavity 4.

  In particular, the confinement function is sometimes called phase stability. Here, the phase stability means that each charged particle is converted into a bunch 3 by receiving a convergence force in the direction of the traveling axis by the high-frequency acceleration voltage 4b, and returns to the traveling axis direction of the charged particle. In other words, it means circulating in the high-frequency synchrotron 16.

  FIG. 7 shows the principle of acceleration of charged particles by the induction accelerating cell and the type of induced voltage. The induction accelerating cell is applied with an induction accelerating cell for confining the charged particle beam in the traveling axis direction (hereinafter referred to as a confining induction accelerating cell) and an induced voltage for accelerating the charged particle beam in the traveling axis direction. There are induction accelerating cells (hereinafter referred to as accelerating induction accelerating cells).

  Instead of the confinement induction cell, the high-frequency acceleration cavity 4 may be used to confine the bunch 3 in the traveling axis direction.

  FIG. 7A shows how the bunch 3 is confined by the confining induction acceleration cell. The induced voltage applied to the bunch 3 by the confining induction accelerating cell is referred to as a barrier voltage 9.

  In particular, an induced voltage applied to the bunch head 3d in the direction opposite to the traveling axis direction of the bunch 3 is referred to as a negative barrier voltage 9a, and the voltage value is referred to as a negative barrier voltage value 9c.

  The induced voltage applied to the bunch tail 3e in the same direction as the traveling axis direction of the bunch 3 is referred to as a positive barrier voltage 9b, and the voltage value is referred to as a positive barrier voltage value 9d.

  As a result, phase stability is imparted to the bunch 3 as with the conventional high frequency 4a. The horizontal axis t is a temporal change in the induction cell for acceleration and the vertical axis v is a barrier voltage value to be applied (induction voltage value for acceleration in FIG. 7B).

  FIG. 7B shows how the bunch 3 is accelerated by the induction cell for acceleration. The induced voltage applied to the bunch 3 by the accelerating induction accelerating cell is referred to as an accelerating induced voltage 17.

  In particular, the induced voltage 17 for acceleration necessary for acceleration in the traveling axis direction of the bunch 3 applied to the entire bunch 3 from the bunch head 3d to the bunch tail 3e is referred to as an acceleration voltage 17a.

  In addition, during the time when the bunch 3 does not exist in the acceleration induction accelerating cell, the acceleration induction voltage 17 different from the acceleration voltage 17a is called a reset voltage 17b. This reset voltage 17b is for avoiding magnetic saturation of the induction cell for acceleration.

  With these barrier voltage 9 and induction voltage 17 for acceleration, any energy level (hereinafter referred to as “arbitrary energy level”) allowed by the magnetic field strength of the deflecting electromagnet that constitutes the synchrotron using the induction acceleration cell with an arbitrary charged particle by one accelerator. It is thought that the energy level can be accelerated.

Furthermore, by using an induction accelerating cell, a bunch 3 (super) with a length of 1 microsecond having a time width several times to 10 times the beam length accelerated by the conventional high-frequency synchrotron 16 is used. It is considered possible to accelerate the bunch).
Journal of the Physical Society of Japan vol. 59, no. 9 (2004) p601-p610

  Here, the induction accelerating cell has the same structure in principle as an induction accelerating cavity for a linear induction accelerator that has been manufactured so far. The induction accelerating cell has a double structure including an inner cylinder and an outer cylinder, and a magnetic material is inserted into the outer cylinder to create an inductance. A part of the inner cylinder connected to the vacuum duct around which the bunch 3 circulates is made of an insulator such as ceramic.

  When a pulse voltage is applied from the DC charger to the primary electric circuit surrounding the magnetic body, a primary current (core current) flows through the primary conductor. This primary current generates a magnetic flux around the primary conductor, and the magnetic material surrounded by the primary conductor is excited.

  As a result, the magnetic flux density penetrating through the toroidal magnetic material increases with time. At this time, an induction electric field is generated in accordance with Faraday's induction law at the secondary insulating portion, which is both ends of the inner cylinder of the conductor, with the insulator interposed therebetween. This induction electric field becomes an electric field. The part where the electric field is generated is called an acceleration gap. Therefore, it can be said that the induction accelerating cell is a one-to-one transformer.

  By connecting a switching power source for generating a pulse voltage to the primary side electric circuit of the induction accelerating cell and turning the switching power source on and off from the outside, the generation of the acceleration electric field can be freely controlled.

  FIG. 8 shows control of synchrotron vibration and conventional synchrotron vibration frequency.

  It is known that in the high-frequency synchrotron 16 confinement of charged particles in the traveling axis direction and its acceleration method, the phase space region in which the bunch 3 can be confined, in particular, the traveling axis direction (time axis direction) is limited in principle. It has been.

  Specifically, the bunch 3 is decelerated in the time domain where the high frequency 4a is a negative voltage, and the charged particles diverge in the direction of the traveling axis and are not confined in the time domain where the polarity of the voltage gradient is different. That is, only the acceleration region 4 d that is approximately between the dotted arrows can be used to accelerate the bunch 3.

  In the acceleration region 4d, the phase of the high frequency 4a is moved and controlled so that the center acceleration voltage 3f, which is a constant voltage, is always applied to the bunch center 3c. Therefore, the charged particles positioned on the bunch head 3d are more than the bunch center 3c. Since the energy reaches the high frequency acceleration cavity 4 faster, the head acceleration voltage 3g smaller than the center acceleration voltage 3f received by the bunch center 3c is received and decelerated.

  On the other hand, the charged particles located at the bunch tail 3e have a lower energy than the bunch center 3c and reach the high-frequency acceleration cavity 4 later, so that the charged particles receive and accelerate the tail acceleration voltage 3h higher than the center acceleration voltage 3f received by the bunch center 3c. During acceleration, the particles repeat this process.

  This is called phase stability and is one of the three major principles that enables synchrotron acceleration of charged particles along with resonance acceleration and strong convergence.

  When the bunch 3 receives the phase stability and the charged particles constituting the bunch 3 rotate around the bunch center 3c in a point-symmetric manner in the acceleration direction, this is called synchrotron vibration 3i, and the rotation frequency of the charged particles at that time Is called synchrotron oscillation frequency.

  Here, the confinement is a function that is necessary because the charged particles constituting the bunch 3 always have variations in kinetic energy. The variation in kinetic energy causes a difference in the time for the bunch 3 to reach the same position after making one round of the design trajectory 2. This time difference increases as the laps are repeated unless confinement is performed, and the charged particles diffuse throughout the design trajectory 2.

  When positive and negative induced voltages are applied to both ends of the bunch 3, the particles that are insufficient in energy and delayed in circulation are given energy by the positive induced voltage, resulting in an excessive energy state. Charged particles that have turned around excessively lose energy due to a negative induced voltage, resulting in a lack of energy.

  As a result, the particles whose circulation is delayed are accelerated, and conversely, the particles whose rotation is fast are delayed in rotation, and as a result, the bunch 3 can be localized in a certain region in the direction of the traveling axis. This series of functions is called bunch 3 confinement.

  The function of the confining induction accelerating cell is equivalent to that obtained by separating only the confining function of the conventional high-frequency accelerating cavity 4.

  The confinement is constant so that a charged particle beam incident on a synchrotron using an induction accelerating cell from an injection device can be induced and accelerated in another induction accelerating cell by an induction voltage having a predetermined polarity by the induction accelerating cell. This means that it has a function of reducing the length to a bunch 3 having a length of 3 mm or changing to a bunch 3 having various lengths, and a function of giving phase stability to the bunch 3 during acceleration.

  The term “acceleration” means that after the bunch 3 is formed, the bunch 3 has a function of applying an induction voltage 17 for acceleration.

  In the conventional high-frequency synchrotron 16, it is known that the bunch 3 receives a high frequency that cannot be predicted at the stage of designing from the apparatus constituting the high-frequency synchrotron 16. This phenomenon is called disturbance. This disturbance is an electromagnetic wave emitted by each device constituting the synchrotron, and is given to the bunch 3 as a high frequency frequency that is always determined for each acceleration depending on the installation state.

  When the frequency of the synchrotron vibration 3i of the bunch 3 coincides with the frequency of the disturbance or becomes an integral multiple, resonance is induced in the synchrotron vibration 3i, the charged particles deviate from the ideal energy, and the bunch 3 diffuses in the direction of the traveling axis. However, the time width of the acceleration region 4d of the high frequency 4a is exceeded and a loss occurs. Similarly, when an induction cell for acceleration is used for acceleration of a charged particle beam, it exceeds the length of the application time 17c of the acceleration voltage 17a and is lost.

  For example, the charged particles on the bunch head 3d receive the high-frequency acceleration voltage 4b in the opposite direction to the acceleration direction, cannot synchronize with the synchrotron magnetic field excitation pattern, and collide with the vacuum duct wall surface and disappear.

  In acceleration of charged particles, the loss of particles is not only a problem that acceleration efficiency decreases, but also any charged particles are in a high energy state, so it is important to radiate the vicinity that collides with the vacuum duct wall. With other problems.

Therefore, in the conventional acceleration of charged particles, in order to prevent loss of charged particles due to disturbance, the synchrotron oscillation frequency is controlled by the amplitude fluctuation device 16a that can change the amplitude of the high frequency 4a, and the frequency of the disturbance. I avoided tune-in.
JP-A-8-88100

  Specifically, the high frequency 4a synchronized with the normal magnetic field excitation pattern is changed to a high frequency 4f with an amplitude increase 4e, and a high frequency 4h subjected to phase shift 4g is applied to the bunch 3.

  By performing the control as described above, it is possible to synchronize the circulation frequency of the bunch 3 with the magnetic field excitation pattern by keeping the central acceleration voltage 3f of the bunch 3 constant. Note that the center acceleration voltage 3f applied to the bunch center 3c changes at the high frequency 4f in which the amplitude is simply changed, and cannot be synchronized with the magnetic field excitation pattern.

  In addition, the bunch head 3d is applied with a deceleration voltage 4i in a direction opposite to the head acceleration voltage 3g given by the normal high frequency 4a. On the other hand, an increase 4j is applied to the bunch tail 3e with respect to the head acceleration voltage 3g given by the normal high frequency 4a. As a result, the synchrotron vibration 3i is increased.

  Therefore, the disturbance frequency can be avoided by controlling the synchrotron vibration 3i by the amplitude fluctuation device 16a. Therefore, in the acceleration by the high-frequency acceleration cavity 4, it was possible to prevent activation due to loss of charged particles.

  However, when the charged particles are accelerated by the induction accelerating cell, it is difficult on the circuit to change the negative barrier voltage value 9c and the positive barrier voltage value 9d by the confining induction accelerating cell. Further, since the negative barrier voltage value 9c and the positive barrier voltage value 9d are applied only to the bunch head 3d and the bunch tail 3e and cannot be applied to other charged particles, the conventional high-frequency synchrotron 16 Adopting the method of changing the voltage value used in the above has little effect.

  Naturally, the conventional method requiring the amplitude fluctuation device 16a is problematic in that the construction cost of the synchrotron is increased.

  Accordingly, an object of the present invention is to provide a synchrotron vibration frequency control device 5 that can apply an induced voltage in synchronization with the circulation of the bunch 3 by an induction accelerating cell, and a control method therefor.

In order to solve the above-mentioned problem, the present invention provides an induction accelerating cell 6 that is connected to an annular vacuum duct having a design orbit 2 of a bunch 3 in the synchrotron and applies a barrier voltage 9 to the bunch 3; A switching power source 5b for driving the induction accelerating cell 6, a pattern generator 8b for generating a gate signal pattern 8a for controlling on and off of the switching power source 5b, and a gate parent signal 8c on which the gate signal pattern 8a is based. The stop pattern of the barrier voltage 9 that is given in advance to the variable delay time calculator 13a in synchronization with the circulation of the bunch 3 by a passing signal 7a that is a passing signal of the bunch 3 from the bunch monitor 7 in the vacuum duct. 14, a digital signal processing device 8 d that stops the barrier voltage 9 at a fixed number of turns of the bunch 3. It has a structure of the synchrotron oscillation frequency control device 5, characterized in that to control the synchrotron oscillation frequency composed of Ranaru intelligent controller 8. Further, in the synchrotron, the negative barrier voltage 9a which is an induced voltage opposite to the traveling axis direction 3a of the bunch 3 applied to the bunch head 3d and the same direction as the traveling axis direction of the bunch 3 applied to the bunch tail 3e An induction accelerating cell 6 to which a barrier voltage 9 consisting of a positive barrier voltage 9b, which is an inductive voltage, is applied, a switching power supply 5b for driving the induction accelerating cell 6, and a gate signal for controlling on / off of the switching power supply 5b. A barrier is intermittently provided to the bunch 3 by an intelligent control device 8 comprising a pattern generator 8b for generating a pattern 8a and a digital signal processing device 8d for controlling on / off of a gate parent signal 8c on which the gate signal pattern 8a is based. The configuration of the synchrotron oscillation frequency control method is characterized by applying a voltage 9 .

  Since this invention is the above structure, the following effects are acquired. Since the amplitude fluctuation device 16a is not required, a synchrotron can be installed at low cost. Further, since the variable width of the synchrotron oscillation frequency is widened, beam instability can be avoided.

  Therefore, the beam loss can be reduced, and activation of the environment due to the beam loss can be prevented. Since it is possible to accelerate charged particles only by the induction accelerating cell 6 without using the high-frequency accelerating cavity 4, the conventional accelerator is used to limit the charged particles to be accelerated. It is easy to accelerate charged particles in all charged states to an arbitrary energy state. In addition, the operating cost of the accelerator can be kept low.

  The synchrotron was realized by a synchrotron oscillation frequency control method characterized by intermittently applying a barrier voltage 9 to the bunch 3 by the induction acceleration cell 6.

  Below, based on an accompanying drawing, the synchrotron vibration frequency control apparatus 5 which is this invention, and its control method are demonstrated in detail.

  FIG. 1 is a schematic view of a synchrotron using an induction accelerating cell including a synchrotron vibration frequency control apparatus according to the present invention.

  The synchrotron 1 using the induction accelerating cell 6 using the synchrotron vibration frequency control device 5 according to the present invention includes a design trajectory 2 around the incident bunch 3 in the vacuum duct and a deflecting electromagnet that guarantees strong convergence. 13h, consisting of a device such as a converging electromagnet.

  Here, the case where the high frequency 4a is controlled by the high frequency accelerator including the conventional high frequency acceleration cavity 4 is shown. The synchrotron vibration frequency control of the bunch 3 is performed by a newly incorporated synchrotron vibration frequency control device 5.

  The synchrotron vibration frequency control device 5 is an induced voltage in the direction opposite to the traveling axis direction 3a of the bunch 3 applied to the bunch head 3d connected to the vacuum duct in which the design orbit 2 around which the bunch 3 circulates is located. An induction acceleration cell 6 for applying a barrier voltage 9 which is a negative barrier voltage 9a and an induced voltage in the same direction as the traveling axis direction 3a of the bunch 3 applied to the bunch tail 3e and a positive barrier voltage 9b, the induction acceleration cell 6 A switching power supply 5b capable of applying a pulse voltage via a transmission line 5a, a DC power supply 5b for supplying power to the switching power supply 5b, and an intelligent control for feedback control of the on / off operation of the switching power supply 5b. The device 8 comprises an induced voltage monitor 5d for knowing the induced voltage value applied from the induction accelerating cell 6.

  The intelligent control device 8 according to the present invention includes a pattern generator 8b that generates a gate signal pattern 8a that controls the on / off operation of the switching power supply 5b, and the generation of the gate signal pattern 8a by the pattern generator 8b. It comprises a digital signal processing device 8d for calculating a gate parent signal 8c which is a signal.

  The gate signal pattern 8 a is a pattern for controlling the barrier voltage 9 of the induction accelerating cell 6. A signal for determining the application time 17c and generation timing of the negative barrier voltage 9a when applying the barrier voltage 9, and a signal for determining the application time 17c and generation timing of the positive barrier voltage 9b when applying the positive barrier voltage 9b. And a signal for determining a pause time between the negative barrier voltage 9a and the positive barrier voltage 9b. Therefore, the gate signal pattern 8a can be adjusted according to the length of the bunching 3 to be accelerated.

  The pattern generator 8b is a device that converts the gate parent signal 8c into a combination of on and off of the current path of the switching power supply 5b.

  The switching power supply 5b generally has a plurality of current paths, adjusts the current passing through each branch, and controls the direction of the current to generate positive and negative voltages in the load (here, the induction accelerating cell 6). (FIG. 2).

  The induction accelerating cell 6 has the same function as a conventional confining induction accelerating cell. However, since the conventional induction accelerating cell for confinement imparts phase stability to the charged particles, the barrier accelerating cell 6 constituting the present invention is applied to the barrier voltage 9 for each turn of the bunch 3. When used in combination with another device having a confinement function, it is different from the point that it can function not only for confinement but also for synchrotron vibration frequency control.

  FIG. 2 is an equivalent circuit of the synchrotron vibration frequency control device. The equivalent circuit 10 of the synchrotron vibration frequency control device can be expressed as a switching power supply 5b that is constantly supplied with power from the DC charger 5c connected to the induction accelerating cell 6 via the transmission line 5a.

  The induction acceleration cell 6 is shown as a parallel circuit of an induction component L, a capacitance component C, and a resistance component R. The voltage across the parallel circuit is the negative barrier voltage 9a felt by the bunch 3 or the positive barrier voltage 9b.

  In the circuit state of FIG. 2, the first switch 11a and the fourth switch 11d are turned on by the gate signal pattern 8a, and the voltage charged in the bank capacitor 11 is applied to the induction accelerating cell 6 to the acceleration gap 6a. In this state, a negative barrier voltage 9a for accelerating the bunch 3 is generated.

  Next, the first switch 11a and the fourth switch 11d, which were turned on, are turned off by the gate signal pattern 8a, and the second switch 11b and the third switch 11c are turned on by the gate signal pattern 8a. A positive barrier voltage 9b opposite to the induced voltage is generated in the gap 6a, and the magnetic saturation of the magnetic material of the induced acceleration cell 6 is reset.

  Then, the second switch 11b and the third switch 11c are turned off by the gate signal pattern 8a, and the first switch 11a and the fourth switch 11d are turned on. By repeating such a series of switching operations by the gate signal pattern 8a, it becomes possible to confine the bunch 3 and control the synchrotron oscillation frequency.

  The gate signal pattern 8a is a signal for controlling the driving of the switching power supply 5b, and is digitally controlled by the intelligent control device 8 including the digital signal processing device 8d and the pattern generator 8b based on the passing signal 7a of the bunch 3. The

  The negative barrier voltage 9a or the positive barrier voltage 9b applied to the bunch 3 is equivalent to a value calculated from the product of the current value in the circuit and the matching resistor 12. Therefore, the negative barrier voltage value 9c and the positive barrier voltage value 9d applied can be known by measuring the current value with an ammeter as the induction voltage monitor 5d.

  Therefore, the induced voltage signal 5e obtained by the induced voltage monitor 5d, which is an ammeter, can be fed back to the digital signal processing device 8d and used to generate the next gate parent signal 8c.

  FIG. 3 is a block diagram of the digital signal processing apparatus. The digital signal processing device 8d includes a variable delay time calculator 13a, a variable delay time generator 13c, an on / off selector 13e, and a gate parent signal output unit 13g.

  The variable delay time calculator 13 a is a device that determines the variable delay time 13. The variable delay time calculator 13a is provided with a definition formula of the variable delay time 13 calculated based on information on the type of charged particles and the magnetic field excitation pattern. A series of equations (1) to (6) for calculating a variable delay time 13 to be described later, or a necessary variable delay time pattern.

  Information on the type of charged particle is the mass and valence number of the charged particle to be accelerated. As described above, the energy that the charged particles obtain from the barrier voltage 9 is proportional to the valence number, and the velocity of the charged particles obtained thereby depends on the mass of the charged particles. Since the change in the variable delay time 13 depends on the velocity of the charged particles, these pieces of information are given in advance.

  The variable delay time 13 is a negative signal from the generation of the passing signal 7a of the bunch monitor 7 by using the digital signal processing device 8d in order to adjust the generation timing of the barrier voltage 9 to the time when the bunch 3 passes the induction accelerating cell 6. This is the time for adjusting the time until the barrier voltage 9a or the positive barrier voltage 9b is applied.

  Specifically, the time from the reception of the passing signal 7a from the bunch monitor 7 to the generation of the gate parent signal 8c is controlled inside the digital signal processing device 8d.

Δt which is the variable delay time 13 is the movement time from the bunch monitor 7 where the bunch 3 is placed in any of the design trajectories 2 to the induction acceleration cell 6, t ₀ , and the digital signal processing device from the bunch monitor 7 applying pass t ₁ the transmission time of the signal _7a, and a digital signal processor 8d output from the gate master signal 8c negative barrier in induction cell 6 on the basis of the voltage 9a or the positive barrier voltage 9b, to 8d the transmission time required until When t ₂ is determined by the following equation (1).
Δt = t ₀ − (t ₁ + t ₂ ) (1)

  For example, assuming that the movement time of the bunch 3 at a certain acceleration time is 1 microsecond, the transmission time of the passing signal 7a is 0.2 microsecond, and after the gate parent signal 8c is generated, the negative barrier voltage 9a or If the transmission time 7d required until the positive barrier voltage 9b is generated is 0.3 microseconds, the variable delay time 13 is 0.5 microseconds.

Δt changes with the progress of acceleration. This is because t ₀ changes as the acceleration of the bunch 3 progresses. Therefore, in order to apply the negative barrier voltage 9 a or the positive barrier voltage 9 b to the bunch 3, it is necessary to calculate Δt for each turn of the bunch 3. On the other hand, t ₁ and t ₂ are constant values if each device constituting the synchrotron using the one-end induction accelerating cell 6 is installed.

t ₀ can be obtained from the orbital frequency (f _REV (t)) of the bunch 3 and the length (L) of the design trajectory 2 along which the bunch 3 moves from the bunch monitor 7 to the induction acceleration cell 6. Moreover, you may actually measure.

Here, a method for obtaining t ₀ from the circulation frequency (f _REV (t)) of the bunch 3 is shown. If C ₀ is the total length of the design trajectory 2 around which the bunch 3 circulates, t ₀ can be calculated in real time by the following equation (2).
t ₀ = L / (f _REV (t) · C ₀ ) [seconds] Expression (2)
f _REV (t) is obtained by the following equation (3).

f _REV (t) = β (t) · c / C ₀ [Hz] (3)
Here, β (t) is a relativistic particle velocity, and c is the speed of light (c = 2.998 × 10 ⁸ [m / s]). β (t) is obtained by the following equation (4).

β (t) = √ (1- (1 / (γ (t) ² )) [dimensionless] Equation (4)
Here, γ (t) is a relative theoretical coefficient. γ (t) is obtained by the following equation (5).

γ (t) = 1 + ΔT (t) / E ₀ [Dimensionless] (5)
Here, ΔT (t) is an increase in energy given by the acceleration voltage 17a, and E ₀ is the stationary mass of the charged particle. ΔT (t) is obtained by the following equation (6).

ΔT = ρ · C ₀ · e · ΔB (t) [eV] (6)
Here, ρ is the radius of curvature of the deflecting electromagnet 13h, C ₀ is the total length of the design orbit 2 around which the bunch 3 circulates, e is the charge amount of the charged particles, and ΔB (t) is the intensity of the beam deflection magnetic field from the start of acceleration. It is an increase.

The static mass (E ₀ ) of charged particles and the charge amount (e) of charged particles vary depending on the type of charged particles.

  When the equation for obtaining the series of variable delay times 13 (Δt) described above is obtained by the definition equation and the variable delay time 13 (Δt) is obtained in real time, the definition equation is given to the variable delay time calculator 13a of the digital signal processing device 8d.

Therefore, if the distance (L) from the bunch monitor 7 to the induction acceleration cell 6 and the total length (C ₀ ) of the design trajectory 2 around which the bunch 3 circulates are determined, the variable delay time 13 is uniquely determined by the circulation frequency of the bunch 3. Determined. Furthermore, the circular frequency of the bunch 3 is also uniquely determined by the magnetic field excitation pattern.

  Further, if the type of charged particles and the setting of the synchrotron using the induction accelerating cell 6 are determined, the necessary variable delay time 13 at a certain acceleration time is also uniquely determined. Therefore, if the bunch 3 performs an ideal acceleration according to the magnetic field excitation pattern, the variable delay time 13 can be calculated in advance according to the above definition formula.

  The variable delay time 13 given as described above is output to the variable delay time generator 13c as a variable delay time signal 13b which is digital data.

  The variable delay time generator 13c is a counter based on a certain frequency, and is a device that allows the passage signal 7a to pass after being held in the digital signal processing device 8d for a certain period of time. For example, if the counter is 1 kHz, the counter value 1000 is equivalent to 1 second. That is, the length of the variable delay time 13 can be controlled by inputting a numerical value corresponding to the variable delay time 13 to the variable delay time generator 13c.

  Specifically, the variable delay time generator 13c varies the generation of the gate parent signal 8c based on the variable delay time signal 13b that is a numerical value corresponding to the variable delay time 13 output by the variable delay time calculator 13a. Control for stopping for a time corresponding to the delay time 13 is performed. As a result, the generation timing of the negative barrier voltage 9a or the positive barrier voltage 9b can be matched with the time when the bunch 3 reaches the induction accelerating cell 6.

  For example, when the variable delay time calculator 13a outputs the variable delay time signal 13b having a numerical value of 150 to the variable delay time generator 13c, which is a counter of 1 kHz, the variable delay time generator 13c Control is performed to delay the generation of the pulse 13d.

  The variable delay time generator 13c receives the passing signal 7a from the bunch monitor 7 and the variable delay time signal 13b from the variable delay time calculator 13a, and for each bunch 3 that has passed through the bunch monitor 7, the next barrier voltage 9 And the pulse 13d, which is information of the variable delay time 13, is output to the on / off selector 13e.

  Here, the passing signal 7 a is a pulse generated at the moment when the bunch 3 passes the bunch monitor 7. The pulse includes a voltage type, a current type, an optical type, and the like having an appropriate intensity depending on the type of the medium or cable transmitting the pulse. The bunch monitor 7 for obtaining the passing signal 7a may be a monitor that senses the passage of protons conventionally used in the high-frequency synchrotron 16.

  The passage signal 7a is used to give the passage timing of the bunch 3 as time information to the digital signal processing device 8d. By the passage of the bunch 3, the position of the bunch 3 in the traveling axis direction 3a on the design trajectory 2 is obtained by the rising portion of the generated pulse. That is, the passing signal 7 a is a reference for the start time of the variable delay time 13.

  The on / off selector 13e is a device that determines whether the barrier voltage 9 is generated (on) or not (off).

  For example, when the negative barrier voltage value 9c (positive barrier voltage value 9d) required at a certain moment is −0.5 kV (0.5 kV), 1 = pulse 13f is generated, 0 = pulse 13f is not generated It is defined as

  A negative barrier voltage 9a (or positive barrier voltage 9b) having a constant value of −1.0 kV (1.0 kV) is used, and the negative barrier voltage 9a (or positive barrier) is applied every turn while the bunch 3 makes 10 turns. Whether or not the voltage 9b) is applied is expressed as [1, 0,..., 1].

  Then, if 1 is 5 times and 0 is 5 times, the average negative barrier voltage value (positive barrier voltage value) received by the bunch 3 during 10 laps is -0.5 kV (0.5 kV). Become. In this way, the on / off selector 13e can digitally control the negative barrier voltage 9a or the positive barrier voltage 9b.

  For example, the equivalent barrier voltage value pattern is a case where the negative barrier voltage value 9c (positive barrier voltage value 9d) is changed from 0 V to -1 kV (1 kV) per second and is controlled at intervals of 0.1 second. The equivalent barrier voltage value pattern is 0 kV for 0.1 seconds from the start of acceleration, −0.1 kV (0.1 kV) for 0.1 to 0.2 seconds, and −0 for 0.2 to 0.3 seconds. .2 kV (0.2 kV)... A data table such as −1.0 kV (1.0 kV) for 0.9 to 1.0 seconds.

  Also, the negative barrier voltage value 9c or the positive barrier voltage value 9d necessary for a certain time can be calculated in real time for each turn of the bunch 3. When the negative barrier voltage value 9c or the positive barrier voltage value 9d necessary for a certain time is calculated in real time, the magnetic field strength at that time is beamed from the deflecting electromagnet 13h constituting the synchrotron 1 using the induction accelerating cell 6. What is necessary is just to calculate with the same arithmetic expression as the case where it receives as the deflection | deviation magnetic field strength signal 13i and calculates beforehand.

  The pulse 13f for controlling the generation of the gate parent signal 8c, which is determined based on the negative barrier voltage value 9c necessary for a certain time during acceleration given as described above or the positive barrier voltage value 9d, is generated. It outputs to the gate parent signal output device 13g.

  The gate parent signal output unit 13g is a pulse for transmitting a pulse 13f including information on both the variable delay time 13 and the barrier voltage 9 that has passed through the digital signal processing device 8d to the pattern generator 8b, that is, the gate parent. It is a device that generates a signal 8c.

  The rising edge of the pulse, which is the gate parent signal 8c output from the gate parent signal output unit 13g, is used as the generation timing of the barrier voltage 9. The gate master signal output unit 13g is a voltage type, current type, or optical type having an appropriate pulse intensity depending on the type of medium or cable that transmits the pulse 13f output from the on / off selector 13e to the pattern generator 8b. It has a role to convert.

  Similarly to the passing signal 7a, the gate parent signal 8c is output at the moment when the variable delay time 13 for adjusting the passage of the bunch 3 and the generation timing of the negative barrier voltage 9a or the positive barrier voltage 9b has elapsed. This is a rectangular voltage pulse output from the device 13g. The pattern generator 8b starts operating by recognizing the rising edge of the pulse which is the gate parent signal 8c.

  The digital signal processing device 8d configured as described above is based on the gate signal pattern 8a for controlling the driving of the switching power supply 5b based on the passing signal 7a from the bunch monitor 7 in the design orbit 2 around which the bunch 3 circulates. The gate master signal 8c is output to the pattern generator 8b. That is, it can be said that the digital signal processing device 8d controls on and off of the induced voltage.

  By calculating the variable delay time 13, the necessary negative barrier voltage value 9c, or the positive barrier voltage value 9d in real time, the magnetic field excitation of the synchrotron 1 using the induction accelerating cell 6 without changing any setting. Corresponding to the pattern, it becomes possible to apply the negative barrier voltage 9a or the positive barrier voltage 9b synchronized with the circulation frequency of the bunch 3.

  When the variable delay time 13 is calculated in advance, a necessary variable delay time pattern (FIG. 7) corresponding to an ideal variable delay time pattern (FIG. 7) in the variable delay time calculator 13a, an on / off selector By simply rewriting the equivalent acceleration voltage value pattern in 13e to a calculation result in accordance with the selected charged particle and magnetic field excitation pattern, the passage timing of the bunch 3 and the generation timing of the barrier voltage 9 can always be matched. Therefore, it becomes possible to accelerate arbitrary charged particles to an arbitrary energy level.

  Hereinafter, the synchrotron vibration frequency control method will be described using the synchrotron vibration frequency control device 5 according to the present invention.

  FIG. 4 shows a gate signal pattern for simulation. Conventionally, it has been considered that the barrier voltage 9 applied by the confining induction accelerating cell must be applied every turn of the bunch 3 in order to prevent the charged particles from diffusing in the traveling axis direction 3a.

  However, even if the barrier voltage 9 is intermittently applied while simulating the state of confinement of charged particles, if the barrier voltage 9 is secured more than a certain number of times, the bunch 3 is confined without diffusing for a certain time. Has been found to be possible.

  Therefore, while the bunch 3 goes around the design trajectory 2 100 times, using the stop patterns 14 of the three types of gate signal patterns 8a in which the time zone during which the barrier voltage 9 is applied is changed, The frequency was analyzed using simulation. The stop pattern 14 of the three types of gate signal patterns 8a shown here is an example of the embodiment of the present invention. The analysis result is shown in FIG.

  The horizontal axis (T) in FIG. 4 is the number of turns 3 j of the bunch 3. On on the vertical axis means the generation of the barrier voltage 9, and off means the interruption of the barrier voltage 9.

  In the case (1) 14a, the barrier voltage 9 is applied every time until the bunch 3 turns 3j1-70 and 81-90, and the barrier voltage 9 is applied until the bunch 3 turns 3j71-80 and 91-100. Stop the occurrence of.

  In the case (2) 14b, the barrier voltage 9 is applied every time until the number of turns 3j1-80 of the bunch 3, and the generation of the barrier voltage 9 is stopped until the number of turns 3j81-100 of the bunch 3.

  In the case (3) 14c, the barrier voltage 9 is applied every time until the bunch 3 turns 3j1-40 and 51-90, and the barrier voltage 9 is applied until the bunch 3 turns 3j41-50 and 91-100. Stop the occurrence of.

  Therefore, the stop pattern 14 of the three types of gate signal patterns 8a has the same total number of application (80 times) of the barrier voltage 9, but is different in the application position (number of rounds). That is, the barrier voltage 9 having a different pattern is intermittently applied to the bunch 3.

  FIG. 5 shows the simulation analysis result of FIG. The graph of FIG. 5 is the synchrotron vibration frequency spectrum 15.

  The horizontal axis represents frequency (Hz), and the vertical axis represents the distribution of charged particles. Case (1) 14a, case (2) 14b, and case (3) 14c correspond to the three types of gate signal patterns 8a in FIG.

  The charged particles constituting the bunch 3 do not all exist with the same synchrotron vibration frequency, but exist as a group having a certain synchrotron vibration frequency range.

  Therefore, the charged particles having the highest synchrotron vibration frequency present in the bunch 3 exhibit properties that approximate the synchrotron vibration frequency of the bunch 3.

  Therefore, by comparing the distribution of charged particles, that is, by comparing the most frequent synchrotron vibration frequencies existing in the bunch 3, the relationship with the change in the synchrotron vibration frequency of the bunch 3 due to the difference in the gate signal pattern 8a. Can be confirmed.

  The median of case (1) 14a is 350 Hz, the median of case (2) 14b is 285 Hz, and the median of case (3) 14c is around 310 Hz.

  From this result, it can be said that the synchrotron oscillation frequency can be controlled from 285 Hz to 350 Hz by adjusting the generation timing of the gate signal pattern 8a, that is, the barrier voltage 9.

  Therefore, it means that the control for changing the synchrotron oscillation frequency can be performed so as not to resonate with the frequency of the disturbance. Therefore, only by incorporating the induction accelerating cell 6 into the synchrotron, it is possible to reduce the beam loss due to the disturbance and to prevent the environment from being activated.

1 is a schematic view of a synchrotron using an induction accelerating cell including the present invention. It is an equivalent circuit of a synchrotron vibration frequency control device. It is a block diagram of a digital signal processing apparatus. It is a gate signal pattern for simulation. It is a simulation analysis result of FIG. It is a figure which shows the acceleration principle of the charged particle by a high frequency acceleration cavity. It is a figure which shows the acceleration principle of the charged particle by an induced voltage. It is a figure explaining the synchrotron vibration by a high frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Synchrotron 2 Design orbit 3 Bunch 3a Advancing axis direction 3c Bunch center 3d Bunch head 3e Bunch tail 3f Center acceleration voltage 3g Head acceleration voltage 3h Tail acceleration voltage 3i Synchrotron vibration 3j Number of rotations 4 High frequency acceleration cavity 4a High frequency 4b High frequency Acceleration voltage 4c High-frequency acceleration voltage value 4d Acceleration region 4e Amplitude increase 4f High-frequency 4g Phase shift 4h High-frequency 4i Deceleration voltage 4j Increase 5 Synchrotron oscillation frequency control device 5a Transmission line 5b Switching power supply 5c DC charger 5d Induction voltage monitor 5e Induction voltage monitor Signal 6 Induction acceleration cell 6a Acceleration gap 7 Bunch monitor 7a Passing signal 8 Intelligent controller 8a Gate signal pattern 8b Pattern generator 8c Gate parent signal 8d Digital signal processor 9 Barrier voltage 9 Negative barrier voltage 9b Positive barrier voltage 9c Negative barrier voltage value 9d Positive barrier voltage value 10 Equivalent circuit of synchrotron oscillation frequency control device 11 Bank capacitor 11a First switch 11b Second switch 11c Third switch 11d Fourth switch 12 matching resistor 13 variable delay time 13a variable delay time calculator 13b variable delay time signal 13c variable delay time generator 13d pulse 13e on / off selector 13f pulse 13g gate parent signal output 13h deflection electromagnet 13i beam deflection magnetic field strength signal 14 stop pattern 14a Case (1)
14b Case (2)
14c Case (3)
DESCRIPTION OF SYMBOLS 15 Synchrotron vibration frequency spectrum 16 High frequency synchrotron 16a Amplitude fluctuation apparatus 17 Induction voltage 17a Acceleration voltage 17b Reset voltage 17c Application time

Claims (2)

  In a synchrotron, an induction accelerating cell that applies a barrier voltage to a bunch, a switching power source that drives the induction accelerating cell, a pattern generator that generates a gate signal pattern that controls on and off of the switching power source, and the gate signal A synchrotron vibration frequency control device comprising an intelligent control device comprising a digital signal processing device for controlling on and off of a gate parent signal as a basis of a pattern. In the synchrotron , a negative barrier voltage which is an induced voltage opposite to the traveling axis direction of the bunch applied to the bunch head and a positive barrier which is an induced voltage in the same direction as the traveling axis direction of the bunch applied to the bunch tail An induction accelerating cell that applies a barrier voltage composed of a voltage, a switching power source that drives the induction accelerating cell, a pattern generator that generates a gate signal pattern that controls on and off of the switching power source, and a base of the gate signal pattern A control method of a synchrotron oscillation frequency, wherein a barrier voltage is intermittently applied to a bunch by an intelligent control device comprising a digital signal processing device for controlling on and off of a gate parent signal .

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