JP2014175249A - Cyclotron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cyclotron the start-up time of which can be shortened.SOLUTION: A cyclotron 1 includes a pair of upper pole 24 and lower pole 26 facing each other, an electromagnet coil 12 (main coil 32) wound around the outer periphery of each pole 24, 26, a cooler 18 supplying a fluid performing heat exchange with the electromagnet coil 12, and a control unit 22 for reducing the value of a current flowing through the electromagnet coil 12 below the current value during operation, depending on an operation stop signal being inputted, and performing operation stop control for adjusting the flow rate or temperature of the fluid supplied from the cooler 18.

Description

  The present invention relates to a cyclotron.

  A cyclotron is a kind of particle accelerator for accelerating charged particles such as protons. Patent document 1 is disclosing the cyclotron provided with a core, an electromagnet coil, and a high frequency generator.

  The core includes a pair of upper pole portion and lower pole portion that form a main magnetic field facing each other, and a yoke portion that magnetically connects the upper pole portion and the lower pole portion. The electromagnet coil is formed between a main coil arranged so as to surround the outer periphery of the upper pole part and the lower pole part in order to form a main magnetic field, and an upper pole part and a lower pole part in order to form an isochronous magnetic field. And a trim coil. Due to the magnetic field formed by these cores and electromagnet coils, the charged particles introduced into the center of the cyclotron move outward while drawing a circular orbit (spiral orbit).

  The high frequency generator includes a pair of dee electrodes having a fan shape, for example, and a high frequency power source. A high-frequency power source generates an alternating electric field in which the direction of the electric field is switched between the dee electrodes at a constant period, and passes through the dee electrode by synchronizing the timing of the charged particles passing between the dee electrodes and the period of the high-frequency electric field. Every time charged particles are accelerated.

JP 2000-150199 A

  By the way, in a cyclotron, it is necessary to flow a very large current through an electromagnetic coil to form a magnetic field. Therefore, Joule heat generated from the electromagnet coil is transmitted to the core, and the separation distance between the upper pole portion and the lower pole portion changes due to thermal expansion of the core. Specifically, since the volume of the yoke part is larger than that of the upper pole part and the lower pole part, the yoke part thermally expands so that the upper pole part and the lower pole part are separated from each other. The separation distance increases.

  When the separation distance increases, the magnetic field distribution changes, the magnetic field and the high-frequency electric field do not correspond to each other, the charged particle acceleration efficiency decreases, and a stable charged particle beam (beam) cannot be obtained. Therefore, normally, the magnetic field and the high-frequency electric field are associated with each other assuming the separation distance in a state where a large current flows through the electromagnetic coil and the core is heated (when the cyclotron is in operation).

  However, when the cyclotron is not in operation, no current flows through the electromagnet coil, so the temperature of the electromagnet coil and the core decreases. Therefore, when the cyclotron is restarted, it takes time until the electromagnetic coil and the core reach a predetermined temperature and a desired magnetic field distribution is obtained. Especially when the cyclotron is stopped for a long time on weekends, regular inspections, etc., and the temperature of the electromagnet coil and the core is extremely reduced, or when the cyclotron is large and the volume (heat capacity) of the electromagnet coil and core is large. It may take 10 or more hours to complete the start-up of the cyclotron after obtaining the magnetic field distribution. The reason why such a long time is required is that the efficiency of heat conduction between the electromagnet coil and the yoke part is poor, and furthermore, the heat capacity of the yoke part, the upper pole part, and the lower pole part is large.

  Therefore, an object of the present invention is to provide a cyclotron capable of shortening the startup time.

  A cyclotron according to one aspect of the present invention includes a pair of first and second pole portions facing each other, an electromagnetic coil wound around the outer periphery of the first and second pole portions, and an electromagnetic coil. In accordance with the flow path through which the fluid for heat exchange flows and the operation stop signal input, the current value flowing through the electromagnetic coil is made smaller than the current value during operation, and the flow rate or temperature of the fluid flowing through the flow path is adjusted. And a control unit that performs operation stop control.

  In the cyclotron according to one aspect of the present invention, the control unit makes the current value flowing through the electromagnetic coil smaller than the current value during operation in accordance with the input operation stop signal, and the flow rate of the fluid flowing through the flow path or Perform stop control to adjust temperature. For this reason, Joule heat generated in the electromagnet coil decreases as the current value decreases. However, since the flow rate or temperature of the fluid flowing through the flow path is adjusted, the amount of heat exchanged between the electromagnet coil and the fluid is small. Become. Therefore, even if the operation of the cyclotron is stopped, the temperature of the first and second pole portions during operation does not extremely decrease, so that a large change is hardly caused in the separation distance between these pole portions. As a result, since the desired magnetic field distribution can be maintained even when the cyclotron is not in operation, it is possible to shorten the start-up time of the cyclotron.

  By the way, in order to shorten the start-up time of the cyclotron, it is conceivable to cool the electromagnet coil while energizing the electromagnet coil when the cyclotron is not in operation, as in the case of operation. In this case, the power consumption becomes extremely large even though the cyclotron is not operating. However, in the cyclotron according to one aspect of the present invention, when the control unit performs the cyclotron operation stop control, the current value flowing through the electromagnetic coil becomes smaller than the current value during operation. Therefore, it is possible to save power while shortening the start-up time of the cyclotron.

  A temperature sensor for measuring the temperature of the first or second pole portion is further provided, and the control portion performs temperature control of the first or second pole portion after the operation stop control and is measured by the temperature sensor. The amount of current that flows through the electromagnet coil may be increased when becomes below a predetermined threshold. In this case, even if the flow rate or temperature of the fluid flowing through the flow path is adjusted, even if the temperature of the first or second pole portion further decreases, current flows through the electromagnetic coil and Joule heat is generated. Therefore, the Joule heat is transferred to the first and second pole portions. Therefore, the temperature of the first and second pole portions can be set within a desired range in which a desired magnetic field distribution can be obtained.

  The control unit may perform the operation stop control for adjusting the flow rate or the temperature of the fluid flowing through the flow path while setting the current value flowing through the electromagnet coil to 0 according to the input operation stop signal. In this case, since no current flows through the electromagnetic coil when the cyclotron is not in operation, further power saving can be achieved.

  The temperature sensor may be disposed in the first or second pole portion.

  The temperature sensor may be a platinum resistance temperature sensor.

  A temperature sensor for measuring the temperature of the first or second pole portion is further provided, and the control portion performs temperature control of the first or second pole portion after the operation stop control and is measured by the temperature sensor. The temperature of the fluid flowing through the flow path may be raised when the value becomes equal to or less than a predetermined threshold value. In this case, even if the flow rate or temperature of the fluid flowing through the flow path is adjusted, the temperature of the fluid flowing through the flow path rises even if the temperature of the first or second pole portion further decreases. Therefore, the heat of the fluid is transferred to the first and second pole portions. Therefore, the temperature of the first and second pole portions can be set within a range where a desired magnetic field distribution can be obtained.

  A cyclotron according to another aspect of the present invention includes a pair of first and second pole portions facing each other, an electromagnet coil wound around the outer periphery of the first and second pole portions, and first and second In response to the heater for heating the pole part of the motor and the input operation stop signal, the current value flowing through the electromagnet coil is made smaller than the current value during operation, and the first and second pole parts are heated by the heater. A control unit that performs operation stop control.

  In the cyclotron according to another aspect of the present invention, the control unit makes the current value flowing through the electromagnet coil smaller than the current value during operation in accordance with the input operation stop signal, and the first and second by the heater. The stop control is performed to heat the pole part. Therefore, Joule heat generated in the electromagnetic coil decreases as the current value decreases. However, since the first and second pole portions are heated by the heater, even if the operation of the cyclotron is stopped, The temperature of the 1st and 2nd pole part does not fall extremely. Therefore, it is difficult for a large change to occur in the separation distance between these pole portions. As a result, since the desired magnetic field distribution can be maintained even when the cyclotron is not in operation, it is possible to shorten the start-up time of the cyclotron.

  By the way, in order to shorten the start-up time of the cyclotron, it is conceivable to cool the electromagnet coil while energizing the electromagnet coil when the cyclotron is not in operation, as in the case of operation. In this case, the power consumption becomes extremely large even though the cyclotron is not operating. However, in the cyclotron according to one aspect of the present invention, when the control unit performs the cyclotron operation stop control, the current value flowing through the electromagnetic coil becomes smaller than the current value during operation. Therefore, it is possible to save power while shortening the start-up time of the cyclotron.

  ADVANTAGE OF THE INVENTION According to this invention, the cyclotron which can shorten starting time can be provided.

FIG. 1 is a schematic view showing a cyclotron according to the present embodiment. FIG. 2 is an enlarged view showing the electromagnetic coil portion of FIG. FIG. 3 is a diagram showing changes in current and flow rate. FIG. 4 is a diagram illustrating another example of changes in current and flow rate. FIG. 5 is a diagram showing still another example of changes in current and flow rate. FIG. 6 is a schematic diagram showing another example of the cyclotron according to the present embodiment.

  Embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are exemplifications for explaining the present invention and are not intended to limit the present invention to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  As shown in FIG. 1, the cyclotron 1 according to the present embodiment includes a core 10, an electromagnetic coil 12, an electromagnetic coil power supply 14, a high frequency generator 16, a cooling device 18, a hot water supply device 20, and a control. Part 22. The core 10 includes a pair of an upper pole portion 24 and a lower pole portion 26 that form a main magnetic field facing each other, and a yoke portion 28 that magnetically connects the upper pole portion 24 and the lower pole portion 26. The upper pole part 24 and the lower pole part 26 are located in a vacuum box 30 whose inside is evacuated.

  In the present embodiment, a temperature sensor 24 a is provided in the upper pole portion 24. Although not shown, a temperature sensor may also be provided in the lower pole portion 26. As these temperature sensors, for example, platinum resistance temperature sensors can be used. Data on the temperature detected by the temperature sensor is input to the control unit 22.

  The electromagnet coil 12 includes a main coil 32 and a trim coil 34. The main coil 32 is for forming a main magnetic field, and is configured by winding a hollow metal tube 36 (also called a hollow conductor) as shown in detail in FIG. The main coil 32 includes a first portion 32 a disposed so as to surround the outer periphery of the upper pole portion 24, and a second portion 32 b disposed so as to surround the outer periphery of the lower pole portion 26. The first portion 32a and the second portion 32b are electrically connected in series.

  The trim coil 34 is for forming an isochronous magnetic field, and is disposed between the upper pole portion 24 and the lower pole portion 26. However, the electromagnet coil 12 may not include the trim coil 34. The electromagnet coil power supply 14 causes a current to flow through the electromagnet coil 12 (the main coil 32 and the trim coil 34) based on an instruction from the control unit 22.

  When charged particles are introduced into the center of the cyclotron 1, the charged particles move outward while drawing a circular orbit (spiral orbit) by the magnetic field formed by the core 10 and the electromagnetic coil 12. That is, a region in the vacuum box 30 and between the upper pole portion 24 and the lower pole portion 26 functions as an acceleration space for charged particles.

  The high frequency generator 16 includes a pair of dee electrodes 38 having a fan shape, for example, and a high frequency power source 40. The Dee electrode 38 is disposed in the vacuum box 30 and between the upper pole portion 24 and the lower pole portion 26 (between the trim coils 34). That is, the dee electrode 38 is located in the acceleration space.

  The high frequency power supply 40 supplies high frequency power to the dee electrode 38 based on an instruction from the control unit 22, and generates an alternating electric field (high frequency electric field) in which the direction of the electric field is switched between the dee electrodes 38 at a constant cycle. By synchronizing the timing at which the charged particles pass between the dee electrodes 38 and the period of the high-frequency electric field, the charged particles are accelerated each time they pass through the dee electrode 38.

  The cooling device 18 cools the electromagnet coil 12 by circulating a cooling medium (fluid) such as cooling water through the pipes 42 and 44. The pipe 42 extending between the cooling device 18 and the main coil 32 is branched into two, the inlet side of the metal tube 36 constituting the first portion 32 a of the main coil 32, and the second portion of the main coil 32. Each of them is connected in parallel to the inlet side of the metal pipe 36 constituting 32b. The piping 44 extending between the cooling device 18 and the main coil 32 is branched into two, the outlet side of the metal tube 36 constituting the first portion 32 a of the main coil 32, and the second portion of the main coil 32. Each of them is connected in parallel to the outlet side of the metal pipe 36 constituting 32b. Therefore, the fluid flowing from the cooling device 18 flows through the metal tube 36 constituting the first portion 32a and the metal tube 36 constituting the second portion 32b, respectively, and after exchanging heat with the main coil 32, Return to the cooling device 18. That is, the cooling device 18, the pipes 42 and 44, and the metal pipe 36 that constitutes the first and second portions 32 a and 32 b constitute a flow path through which a fluid flows.

  Valves 46 and 47 are provided in the pipes 42 and 44, respectively, and are opened and closed based on instructions from the control unit 22. The pipe 44 is provided with a flow meter 48, and flow rate data measured by the flow meter 48 is input to the control unit 22.

  The hot water supply device 20 circulates a heating medium (fluid) such as hot water through the pipes 50 and 52 and the pipes 42 and 44 to keep the electromagnetic coil 12 warm. The pipe 50 is connected to the pipe 42. The pipe 50 is provided with a valve 54 that is opened and closed based on an instruction from the control unit 22. The pipe 52 is connected to the pipe 44. The pipe 44 is provided with a valve 56 and is opened and closed based on an instruction from the control unit 22.

  The control unit 22 switches the cyclotron between the operating state and the non-operating state according to the input operation signal or operation stop signal. When the operation signal is input to the control unit 22, the control unit 22 instructs the electromagnetic coil power source 14, the high frequency power source 40, and the cooling device 18 to form a main magnetic field, an isochronous magnetic field, and a high frequency electric field, respectively.

  On the other hand, when the operation stop signal is input to the control unit 22, the control unit 22 instructs the high frequency power supply 40 to stop the high frequency power supply to the dee electrode 38. Further, as shown in FIG. 3, the control unit 22 instructs the electromagnetic coil power supply 14 to reduce the magnitude of the current flowing through the main coil 32 than when the cyclotron 1 is operating, and to the valves 46 and 47. An instruction is made to reduce the flow rate of the fluid circulating between the cooling device 18 and the main coil 32 (metal pipe 36). The distance between the upper pole portion 24 and the lower pole portion 26 is maintained by the magnitude of the current flowing through the main coil 32 and the flow rate of the fluid circulating between the cooling device 18 and the main coil 32 (metal tube 36). To be set. The magnitude of the current and the flow rate may be set according to values obtained in advance through experiments or the like, or the magnitude of the current and the flow rate may be set according to the temperature measured by the temperature sensor 24a.

  In the present embodiment as described above, Joule heat generated in the electromagnetic coil 12 decreases as the current value decreases, but the flow rate of the fluid flowing through the flow path is adjusted to be small. The amount of heat exchanged with the fluid is also reduced. Therefore, even if the operation of the cyclotron 1 is stopped, the temperature of the pole portions 24 and 26 during operation does not extremely decrease, so that a large change occurs in the separation distance between the upper pole portion 24 and the lower pole portion 26. It becomes difficult. As a result, since the desired magnetic field distribution can be maintained even when the cyclotron 1 is not in operation, the start-up time of the cyclotron 1 can be shortened.

  By the way, in order to shorten the start-up time of the cyclotron 1, it is conceivable to cool the electromagnet coil 12 while energizing the electromagnet coil 12 even when the cyclotron 1 is not in operation, as in the case of operation. In this case, the amount of power consumption becomes extremely large although the cyclotron 1 is not operating. However, in the cyclotron 1 according to the present embodiment, when the control unit 22 performs the operation stop control of the cyclotron 1, the current value flowing through the electromagnetic coil 12 becomes smaller than the current value during operation. Therefore, it is possible to save power while shortening the start-up time of the cyclotron.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to above-described embodiment. For example, when an operation stop signal is input to the control unit 22, the control unit 22 instructs the electromagnet coil power supply 14 to set the magnitude of the current flowing through the main coil 32 to 0 as shown in FIG. 4. In addition, the valves 46 and 47 may be instructed to reduce the flow rate of the fluid circulating between the cooling device 18 and the main coil 32 (metal pipe 36). In this case, since no current flows through the electromagnetic coil 12 when the cyclotron 1 is not in operation, further power saving can be achieved.

  When the operation stop signal is input to the control unit 22, the control unit 22 instructs the electromagnet coil power supply 14 to make the magnitude of the current flowing through the main coil 32 smaller than that during the operation of the cyclotron 1 (the current In addition, the fluid (hot water) may be circulated between the main coil 32 and the hot water supply device 20 by instructing the valves 46, 47, 54, and 56. In this case, although the Joule heat generated in the electromagnet coil 12 decreases as the current value decreases, hot water is supplied to the electromagnet coil 12 to keep the temperature. Therefore, even if the operation of the cyclotron 1 is stopped, the temperature of the pole portions 24 and 26 during operation does not extremely decrease, so that a large change occurs in the separation distance between the upper pole portion 24 and the lower pole portion 26. It becomes difficult. As a result, since the desired magnetic field distribution can be maintained even when the cyclotron 1 is not in operation, the start-up time of the cyclotron 1 can be shortened.

  Instead of or in addition to the hot water supply device 20, the fluid circulating between the cooling device 18 and the main coil 32 is heated by, for example, a heater provided in the pipes 42 and 44, and the temperature of the fluid is adjusted. You may make it do.

  In the present embodiment described above, the control unit 22 instructs the electromagnetic coil power supply 14 to make the magnitude of the current flowing through the main coil 32 smaller than when the cyclotron 1 is operating, and also instructs the valves 46 and 47. The flow rate of the fluid circulating between the cooling device 18 and the main coil 32 (metal pipe 36) is adjusted to be small. In this case, even if the operation of the cyclotron 1 is stopped, the temperature of the pole portions 24 and 26 during operation does not extremely decrease. However, as shown in FIG. The temperature can gradually decrease. Therefore, after the control unit 22 performs the operation stop control of the cyclotron 1, when the temperature of the upper pole unit 24 detected by the temperature sensor 24a becomes equal to or lower than a predetermined threshold value, the control unit 22 14 may be controlled to temporarily increase the amount of current flowing through the electromagnetic coil 12 as shown in FIG. In this case, current flows through the electromagnet coil 12 to generate Joule heat, and the Joule heat is transferred to the pole portions 24 and 26. Accordingly, the temperatures of the pole portions 24 and 26 can be set within a desired range in which a desired magnetic field distribution can be obtained. At this time, as shown in FIG. 5C, it is not necessary to control the flow rate of the fluid circulating between the cooling device 18 and the main coil 32 (metal pipe 36), and the flow rate is temporarily reduced. The temperature may be controlled to be further reduced, or hot water may be supplied from the hot water supply device 20 to temporarily raise the temperature of the fluid flowing in the main coil 32 (metal pipe 36).

  The determination as to whether or not the temperature of the upper pole portion 24 has become equal to or lower than a predetermined threshold value may be made based on the temperature of the upper pole portion 24 measured by the temperature sensor 24a as described above, or for a predetermined time. It may be performed depending on whether or not. Specifically, an experiment or the like is performed in advance to measure a time during which the temperature of the upper pole portion 24 is equal to or lower than a predetermined threshold, and when the time has elapsed, the control unit 22 controls the electromagnetic coil power supply 14. Then, as shown in FIG. 5B, the amount of current flowing through the electromagnetic coil 12 may be temporarily increased.

  As shown in FIG. 6, the cyclotron 1 may further include a heater 58 instead of or in addition to the cooling device 18 and the hot water supply device 20. In the example of FIG. 6, the heater 58 is disposed so as to cover the outer surface of the core 10. When the operation stop signal is input to the control unit 22, the control unit 22 instructs the electromagnet coil power supply 14 to make the magnitude of the current flowing through the main coil 32 smaller than that during the operation of the cyclotron 1 (the current In addition, the heater 58 is instructed to heat the core 10 (pole portions 24 and 26). In this case, although the Joule heat generated in the electromagnet coil 12 decreases as the current value decreases, the heat of the heater 58 is transferred to the pole portions 24 and 26. Accordingly, the temperatures of the pole portions 24 and 26 can be set within a desired range in which a desired magnetic field distribution can be obtained. In addition, since the power consumption in the heater 58 is extremely smaller than the power consumption in the electromagnet coil power supply 14, further power saving can be achieved. As long as the pole portions 24 and 26 can be heated by the heater 58, the heater 58 may cover a part of the outer surface of the core 10 or may be embedded in the core 10.

  The present invention is generally applicable to cyclotrons including synchrocyclotrons.

  DESCRIPTION OF SYMBOLS 1 ... Cyclotron, 10 ... Core, 12 ... Electromagnetic coil, 14 ... Electromagnetic coil power supply, 16 ... High frequency generator, 18 ... Cooling device, 20 ... Hot water supply device, 22 ... Control part, 24 ... Upper pole part, 24a ... Temperature Sensor 26 ... Lower pole part 32 ... Main coil 36 ... Metal tube 58 ... Heater

Claims (7)

A pair of first and second pole portions facing each other;
An electromagnet coil wound around the outer periphery of the first and second pole portions;
A flow path through which a fluid that exchanges heat with the electromagnetic coil flows;
A control unit that performs an operation stop control for adjusting a flow rate or a temperature of a fluid flowing through the flow path, while making a current value flowing through the electromagnet coil smaller than a current value during operation according to an input operation stop signal; A cyclotron equipped with. A temperature sensor for measuring the temperature of the first or second pole portion;
The controller is configured to perform the operation stop control, and when the temperature of the first or second pole portion measured by the temperature sensor is equal to or lower than a predetermined threshold value, the electromagnet The cyclotron according to claim 1, wherein the amount of current flowing through the coil is increased.   The said control part performs the said operation stop control which adjusts the flow volume or temperature of the fluid which flows through the said flow path while setting the electric current value which flows into the said electromagnetic coil to 0 according to the operation stop signal input. The cyclotron according to 1 or 2.   The cyclotron according to claim 2, wherein the temperature sensor is disposed in the first or second pole portion.   The cyclotron according to claim 4, wherein the temperature sensor is a platinum resistance temperature sensor. A temperature sensor for measuring the temperature of the first or second pole portion;
The control unit performs the flow control after performing the operation stop control and when the temperature of the first or second pole unit measured by the temperature sensor becomes a predetermined threshold value or less. The cyclotron according to claim 1, wherein the temperature of the fluid flowing through the passage is increased. A pair of first and second pole portions facing each other;
An electromagnet coil wound around the outer periphery of the first and second pole portions;
A heater for heating the first and second pole portions;
Control for performing operation stop control in which the current value flowing through the electromagnet coil is made smaller than the current value during operation and the first and second pole portions are heated by the heater according to the input operation stop signal. And a cyclotron.

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