JPH118098A - Temperature control system for accelerating tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more economical temperature control system for accelerating tube by simplifying the temperature control of cooling water. SOLUTION: An electric heater 12 and a temperature sensor 15 are mounted so as to be brought into contact with an accelerating tube 1. Based on the output of the temperature sensor 15 which directly-measured the temperature of the accelerating tube 1, the electric heater is controlled to control the temperature of the accelerating tube, thereby maintaining respective resonance cavities at fixed dimensions for assurance of stable accelerating magnetic fields. In order to prevent generation of excessive magnetic fields due to current, it is desirable that the resistance wire should be formed so as to go and return on the roughly same route.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a temperature control system for an acceleration tube used in a particle accelerator for accelerating charged particles to high energy.

[0002]

2. Description of the Related Art A high-energy particle beam accelerated by a linear accelerator is used for cancer treatment, sterilization of medical supplies, and sulfur compound S.
Applied technologies have been developed and put to practical use in many fields, such as an environmental improvement device for decomposing Ox and NOx, NOx, and the like, use of synchrotron light, generation of a storage ring free electron laser, and the like. Among them, the free electron laser has been developed in various countries since Mayday, when the principle demonstration experiment was successfully performed in May 1977. In particular, basic demonstrations have been completed for devices using linear accelerators, and in recent years, specific utilization studies have been extended to the medical field, the nuclear field such as isotope separation, and the semiconductor field.

[0003] Free electron lasers require a charged particle beam that is stable in time and of high quality. The accelerating tube has a number of resonance cavities (acceleration structure) with extremely high Q value. When the charged particles are accelerated, microwaves of the resonance frequency are input into this acceleration structure, and the same phase velocity as the accelerating particles is obtained. This is performed by generating an accelerating electric field. Therefore, in order to form a high quality charged particle beam, it is necessary that the resonance mode in the accelerator tube and the frequency of the microwave to be excited exactly match.

However, since the accelerating tube is formed of a metal having a relatively large coefficient of thermal expansion, the shape of each resonance cavity is greatly affected by the temperature. If the dimension and shape of the resonance cavity deviate from a predetermined value, the resonance mode changes or a high Q value cannot be maintained, and the state of particle acceleration changes due to the dispersion of beam energy and the beam quality deteriorates. Therefore, in order to form a stable accelerating electric field, it is preferable to keep the temperature of the accelerating tube constant with time and to make the temperature distribution of the entire accelerating tube uniform.

Further, in the state where the charged particle beam is present, since the energy is supplied from the accelerating microwave to the charged particles, the intensity of the microwaves in each cavity is not constant but distribution occurs. Therefore, the thermal load differs for each cavity and a temperature distribution occurs, and the thermal expansion differs for each cavity due to the thermal load distribution. Thus, a distribution of the resonance frequency occurs, and a shift in the acceleration phase occurs, thereby deteriorating the acceleration performance. there were.
For this reason, conventionally, heat generated in the accelerating tube is eliminated by passing cooling water whose temperature is controlled by providing a cooling water pipe in the accelerating tube, and the temperature over the entire length of the accelerating tube is within about ± 0.1 degrees with respect to a predetermined temperature. Has been managed to fit in. In order to achieve such strict temperature control, it was necessary to distribute a large amount of cooling water whose temperature was precisely controlled.

FIG. 8 is a block diagram showing an example of conventional cooling water temperature control. Cooling water is temperature-controlled in a cooling water tank by a chiller and a heater at a width of about 1 degree Celsius, and then sent to an acceleration tube by a pump via an electric heater. The cooling water absorbs the heat generated in the accelerating tube while passing through a cooling water pipe provided in the outer wall, and is carried out. The electric heater is adjusted based on the cooling water temperature measured at the outlet of the accelerating tube so that the temperature deviation is about ± 0.1 degrees. Further, in order to reduce the axial temperature distribution width in the accelerating tube, there must be no difference in temperature between the upstream and the downstream, so it was necessary to flow an extremely large amount of cooling water. In addition, there has been devised to reduce the temperature difference by flowing part of the cooling water from the downstream to the upstream without flowing the entire cooling water from the upstream to the downstream of the accelerating tube.

Japanese Patent Application Laid-Open No. 8-273898 has a cooling water jacket formed so as to increase its thickness in a stepwise manner in response to a thermal load distribution decreasing from one end of the accelerating tube to the other end. There is disclosed an acceleration tube in which the thermal expansion distribution existing in the axial direction of the acceleration tube is eliminated by adjusting the contact area with the cooling water or the heat transfer of the contact surface. In this method, it is still necessary to circulate a considerable amount of water in order to maintain the temperature of the accelerating tube, and in particular, the response time to temperature change and the time required from startup to steady operation depend on the amount of circulating water. It is the same that a large amount of circulating water is required for stabilization. Therefore, equipment for circulating a large amount of cooling water and equipment for controlling the temperature of a large amount of circulating water are required, which is a great constraint on the installation location and the like.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a temperature control system capable of simplifying the temperature control of the cooling water and easily adjusting the temperature of the acceleration tube as a whole. Another object of the present invention is to provide a temperature control system for reducing a temperature distribution width generated in an axial direction of an acceleration tube.

[0009]

In order to solve the above-mentioned problems, a temperature control system for an acceleration tube used in a particle accelerator for accelerating charged particles includes an electric heater and a temperature sensor which are installed in contact with the acceleration tube, and a temperature sensor for the temperature sensor. The electric heater is controlled based on the output to adjust the temperature of the acceleration tube.
In the past, an electric heater was sometimes used in the accelerating tube temperature control system, but the electric heater was usually used for adjusting the temperature of the cooling water, and was not directly installed in contact with the accelerating tube. Conventionally, the temperature generated by the accelerating tube is sufficiently removed to make the temperature close to room temperature, and the cooling water is circulated abundantly so that there is no temperature difference in the axial direction. This is based on the technical idea of ensuring

However, the inventors of the present invention have found that it is sufficient to control the temperature distribution to be constant regardless of the temperature level in the accelerator tube for the dimensional stability of the accelerator tube. Attention has been directed to the present invention. In other words, the temperature of the accelerating tube rises due to the heat generated in the accelerating tube, and the dimensions of each part are expanded by thermal expansion. The temperature of the accelerating tube is determined by the balance between the amount of heat generated in the accelerating tube and the amount of heat radiation or the amount of heat absorbed by positive means. Therefore, it is not always constant depending on the environment and operating conditions of the device.

Therefore, the accelerating tube temperature control system of the present invention provides an electric heater for heating the accelerating tube and a temperature sensor in contact with the accelerating tube, and uses the result of directly measuring the temperature of the accelerating tube to determine the temperature on the heating side. By controlling and keeping the accelerating tube at a constant temperature, each resonance cavity is maintained at a constant size to secure a stable accelerating electric field. When the temperature of the accelerating tube is too high, it is desirable to provide a radiation fin on the accelerating tube or install an air conditioner in a room where the device is installed to promote heat radiation from the accelerating tube. It should be noted that even if a deviation occurs in the resonance mode of the resonance cavity due to the difference in the temperature level of the accelerator tube, the frequency of the input microwave can be deviated and adjusted to an appropriate resonance wavelength.

Further, it is preferable that a resistance heating wire of the electric heater is provided so as to reciprocate in substantially the same path so that the same amount of heating current flows in opposite directions. If a current flows around the accelerating tube, the electromagnetic field generated by this current affects the motion of charged particles in the accelerating tube, and the orbit is disrupted. Therefore, when using an electric heater, it is necessary to perform advanced electromagnetic shielding so that an extra electromagnetic field is not generated inside the acceleration tube. However, if the heating current reciprocates in almost the same path, the current excites an electromagnetic field of the same strength in both the forward and reverse directions, so that the two cancel each other out, thereby suppressing the generation of an electromagnetic field. Even if no shielding means is introduced, the movement of the charged particles can be prevented from being disturbed.

Further, the electric heater used in the temperature control system for the accelerating tube of the present invention is divided into a plurality of blocks, and independently controls applied electric power based on the output of a temperature sensor provided for each block. You may do so. If such an electric heater is used, the temperature can be controlled independently for each block of the electric heater in accordance with the temperature distribution generated due to the different heat load of each cavity, so that the resonance frequency of the cavity can be appropriately set. Adjustment can prevent deterioration of the acceleration performance.

Further, the electric heater may be configured so that a heat generation amount per unit length is provided with a gradient to offset a heat generation amount distribution in the acceleration tube. The heat load distribution generated in the accelerator tube in the presence of the charged particle beam is large on the inlet side and small on the outlet side. If the density of the electric heater is adjusted so as to be thinner at the inlet side and thicker at the outlet side so as to offset this heat load distribution, the temperature distribution state equalized by a single heater control system including a heater power supply and a temperature detector is obtained. Obtained and economical. In order to adjust the density of the electric heater, the number of windings of the heater resistance wire per unit length of the accelerating tube is changed, or the resistance wire is wound in a coil shape to adjust the length of the resistance wire per unit length. Simple methods are available.

Further, a cooling water pipe may be provided in the axial direction of the acceleration pipe. If the acceleration tube does not reach the appropriate temperature level simply by offsetting the heat generated in the acceleration tube by heat radiation to the outside air, it is necessary to flow cooling water in the above cooling water pipe in the axial direction of the acceleration tube to take heat. preferable. Also in this case, unlike the conventional case, the heat generated in the accelerator tube is appropriately removed by the cooling water, and then the temperature is adjusted to the target temperature by the electric heater. Therefore, it is not necessary to control the temperature of the cooling water strictly. In addition, since the difference between the temperature of the acceleration tube and the temperature of the cooling water may be large, the amount of cooling water may be smaller. Therefore, a cooling water temperature control device having a smaller capacity, a lower accuracy and a much simpler configuration than the conventional cooling water device is sufficient, and the economy as a temperature control system for the entire acceleration tube is improved.

The temperature of the electric heater can be controlled by PID control. By using the PID control including the proportional operation, the integral operation, and the differential operation, it is possible to achieve an improvement in responsiveness that cannot be obtained by on-off control or the like frequently used in normal heater control. Since a delay in heat transfer when the accelerating tube is heated by the electric heater can be used, the control output in the PID control may be a pulse type signal in addition to an analog signal. May be adjusted.

A free electron laser device according to the present invention is characterized in that a linear accelerator equipped with any of the above accelerating tube temperature control systems is used. As a result, the temperature control system is simplified, and the construction cost and the operation cost of the entire free electron laser device are much more economical than the conventional one.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a temperature control system for an accelerating tube according to the present invention will be described in detail with reference to the drawings.

[0019]

Embodiment 1 FIG. 1 is a block diagram showing a first embodiment of an accelerating tube temperature control system according to the present invention, and FIG. 2 is a sectional view of the accelerating tube in the first embodiment. Explaining with reference to FIGS. 1 and 2, the accelerating tube 1 of the present embodiment has a cylindrical shape formed of oxygen-free copper, and has a disk-like shape having a hole at the center where a charged particle passes. Are divided into a number of resonance cavities by the acceleration tube disk 2. A plurality of cooling water pipes 3 are provided in the outer wall of the acceleration tube 1 in the axial direction, through which cooling water absorbs heat loss generated in the resonance cavity during operation and is carried out of the acceleration tube. The cooling water heated by the acceleration tube returns to the cooling water tank 4.

The cooling water tank 4 is provided with a heat exchanger or a secondary cooling pipe 5 and an electric heater 7. The cooling water is cooled by the heat exchanger or the secondary cooling pipe 5 while staying there. After being heated by the electric heater 7 and adjusted to an appropriate temperature, it is sent out again into the cooling water pipe of the acceleration pipe 1. The secondary cooling pipe 5 may be connected to the refrigerator 6 or may simply supply the refrigerant from an external cold source. Temperature detection end 10 provided in cooling water tank 4
Measures the water temperature, and the measured output is input to the controller 9 via the temperature converter 11. The control output of the controller 9 controls the amount of heat generated by the electric heater 7 by adjusting the output of the heater power supply 8. The control accuracy of the cooling water temperature in the cooling water tank 4 is preferably about 1 degree Celsius.

An electric heater 12 is wound around the outer circumference of the accelerating tube 1 and fixed by a method such as welding, bonding or binding. A heating current is supplied to the electric heater 12 from a heater power supply 13. The current output of the heater power supply 13 is controlled by a controller 14.
Control output. The controller 14 is connected to a temperature converter 16 for converting the output of the temperature detecting end 15 for measuring the temperature of the accelerating tube into an appropriate electric signal. Electric heater 1
Reference numeral 2 has a structure in which resistance heating wires are paired in a reciprocating manner, so that a supplied heating current always flows in the opposite direction. Therefore, the electromagnetic field excited by the current is canceled out, and does not affect the motion of the charged particles in the acceleration tube 1.

The controller 14 performs a proportional operation, an integral operation,
It is preferable to control the electric heater 12 using PID control including a differential operation. In ordinary temperature control, a simple control algorithm such as on / off control is often used by utilizing the fact that there is an appropriate first-order lag in heat transfer. For this purpose, PID control is employed.

In the conventional temperature control method using only cooling water, it is necessary to circulate a large amount of cooling water to keep the temperature of the accelerating tube as close as possible to the temperature of the cooling water. And the burden on operating costs was heavy. However, according to the temperature control system for the accelerator tube of the present embodiment, the heat load generated in the accelerator tube is appropriately removed with cooling water to adjust the final accelerator tube temperature by controlling the temperature of the electric heater. The amount of water is small and the temperature control of the cooling water does not need to be strict. Therefore, the equipment cost and the final operation cost of the entire temperature control system of the acceleration tube can be saved. Further, when the microwave power supplied to the acceleration tube is small, it may be sufficient to omit the cooling by the cooling water and expose the acceleration tube to an atmosphere around the acceleration tube to allow the acceleration tube to cool. Note that a radiation fin may be provided to enhance the effect of such cooling. In such a configuration, if the air conditioning equipment for adjusting the atmosphere is properly prepared,
Since only the control system for the electric heater attached to the accelerating tube is required, the economy of the apparatus is further improved. Further, the free electron laser device using the accelerating tube temperature control system of the above embodiment does not require a large-sized device for controlling the cooling water temperature, which has been conventionally required, so that equipment costs and operation costs are low. In addition to this, there is also an advantage that the location conditions are relaxed and the device can be introduced in various places.

[0024]

Embodiment 2 FIG. 3 is a side view showing a mounted state of an acceleration tube heater used in a second embodiment of the acceleration tube temperature control system of the present invention, and FIG. 4 is a sectional view of the acceleration tube. Referring to FIG. 3 and FIG. 4, the acceleration tube 1 of the present embodiment will be described.
The outer wall formed around the resonance cavity partitioned by the acceleration tube disk 2 is provided with a large number of holes in the axial direction. These holes become cooling water pipes 3 every other hole, and cooling water is supplied. The holes interposed between the cooling water pipes 3 pass through the electric heater 21 respectively, and the heater power is supplied in the same manner as the electric heater of the first embodiment. 13 is electrically connected. The rest of the configuration is the same as in the first embodiment. As described above, by using the electric heater 21 directly embedded in the wall of the acceleration tube, it is possible to more directly control the thermal expansion of the resonance cavity and to generate a desired resonance mode. In this case as well, the influence of the electromagnetic field can be suppressed by forming the electric heater with a pair of resistance wires that allow current to flow in both the forward and reverse directions contained in a sheath. One end of the resistance wire may be connected so that the same current always reciprocates at the same position. Alternatively, a power supply electrode is connected to a pair of independent resistance wires opposite to each other, and a current of the same intensity is supplied. You may make it flow in a reverse direction.

[0025]

Third Embodiment FIG. 5 is a drawing showing the distribution of heat loss generated in the accelerating tube, and FIG. 6 is a block diagram showing a mounting state of the accelerating tube heater in the third embodiment of the accelerating tube temperature control system of the present invention. It is. The amount of heat generated by the microwaves in the accelerator tube is not uniform. As can be seen from FIG. 6 showing an example in which the output of the input microwave is 40 MW when the length of the accelerating tube is 3 m, the power loss, that is, the calorific value tends to be large near the entrance and gradually decrease toward the exit. . Therefore, when controlling the temperature of the long accelerating tube using the electric heater in order to make the temperature of the accelerating tube uniform in the longitudinal direction, some measures need to be taken.

In the third embodiment of the present invention, the electric heater which is installed in contact with the accelerating tube is divided into a plurality of blocks 23 in the longitudinal direction, and a heater power supply 24 is provided for each block.
The controller 25 controls the applied power independently based on the output of a temperature sensor (not shown).
Other components are the same as the system of the first embodiment. If such an electric heater is used, in accordance with the temperature distribution generated due to the different heat load of each cavity,
Since the temperature is controlled independently for each block of the electric heater, the resonance frequency of the cavity can be appropriately adjusted to prevent deterioration of the acceleration performance. The controller 25 controls each heater power supply 24 independently. However, it goes without saying that the controller 25 may be provided independently for each heater block.

[0027]

Fourth Embodiment FIG. 7 is a block diagram showing a mounting state of an acceleration tube heater in a fourth embodiment of the acceleration tube temperature control system of the present invention. This embodiment is different from the third embodiment in that a large number of heater blocks are provided and temperature is controlled independently of each other. Instead, the inlet side is thin and the outlet side is thin so as to offset the distribution of the amount of heat loss shown in FIG. The electric heater 26 employs a heating wire arrangement having a heating value distribution such that the heating value is increased. The density of the electric heater 26 is adjusted by a simple method such as changing the number of windings of the heater resistance wire per unit length of the acceleration tube, or adjusting the length of the resistance wire per unit length by winding the resistance wire in a coil shape. be able to.

When the electric heater 26 having such a structure is used, one heater power supply and one temperature detector are used.
It is economical to obtain a uniform temperature distribution over the full acceleration length by the heater control system of the formula. It is needless to say that cooling using cooling water can also be used when using the electric heater 26 having a distribution of the generated heat. Also in this case, in order to prevent the movement of the charged particles in the accelerating tube from being disturbed by the current flowing through the electric heater, it is preferable to flow the currents in opposite directions with a pair of resistance wires.

In each of the above embodiments, the temperature control system can be very economically constructed to omit or simplify the circulation of the cooling water. However, since the temperature control relies on heating by an electric heater, the temperature of the accelerating tube is usually reduced. The temperature will be maintained at a much higher level than the ambient temperature. However, even if the temperature level of the accelerating tube is somewhat high, if the temperature fluctuation is small in time and space, the dimensional accuracy of the accelerating tube can be kept at a desired value. Can be maintained.

[0030]

As described above in detail, according to the temperature control system for an acceleration tube of the present invention, a simpler temperature control system can be provided instead of performing the temperature control in the acceleration tube by precise temperature control of the cooling water. Since the temperature control system is used, a much more economical temperature control system can be constructed as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a temperature control system for an accelerator tube according to the present invention.

FIG. 2 is a cross-sectional view of the acceleration tube in the first embodiment.

FIG. 3 is a side view showing a mounted state of an acceleration tube heater used in a second embodiment of the acceleration tube temperature control system of the present invention.

FIG. 4 is a cross-sectional view of an acceleration tube according to a second embodiment.

FIG. 5 is a diagram showing a distribution of heat loss generated in an acceleration tube.

FIG. 6 is a block diagram showing a mounting state of an accelerating tube heater in a third embodiment of the accelerating tube temperature adjusting system of the present invention.

FIG. 7 is a block diagram showing a mounting state of an acceleration tube heater in a fourth embodiment of the acceleration tube temperature control system of the present invention.

FIG. 8 is a block diagram showing a conventional accelerating tube temperature control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration pipe 2 Acceleration pipe disk 3 Cooling water pipe 4 Cooling water tank 5 Secondary cooling pipe 6 Refrigerator 7 Electric heater 8 Heater power supply 9 Controller 10 Temperature detection end 11 Temperature converter 12 Electric heat heater 13 Heater power supply 14 Controller 15 Temperature detecting end 16 Temperature converter 21 Electric heater 23 Heater block 24 Heater power supply 25 Controller 26 Electric heater

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayuki Kawai 118 Futatsuka Noda City, Chiba Prefecture Kawada Heavy Industries Noda Factory Co., Ltd. (72) Inventor Akihiro Nakayama 118 Futatsuka Noda City Chiba Prefecture Kawasaki Heavy Industries Noda Factory Co., Ltd.

Claims (7)

[Claims] 1. An accelerating tube for use in a particle accelerator for accelerating charged particles to high energy, comprising an electric heater and a temperature sensor in contact with the accelerating tube, and further comprising a controller. Controlling the electric heater to adjust the temperature of the acceleration tube. 2. The electric heater comprises a resistance wire arranged so as to reciprocate substantially the same path, so that an applied current reciprocates the substantially same path so that an electromagnetic field generated by the current is canceled. The temperature control system for an acceleration tube according to claim 1, wherein the temperature control system is configured. 3. The electric heater according to claim 1, wherein the electric heater is divided into a plurality of blocks, and the applied electric power is controlled independently based on an output of a temperature sensor provided for each block. Accelerating tube temperature control system. 4. The temperature control of the accelerating tube according to claim 1, wherein the electric heater has a gradient in the calorific value per unit length so as to offset the calorific value distribution in the accelerating tube. system. 5. The temperature control system for an acceleration pipe according to claim 1, wherein a cooling water pipe is further provided in an axial direction of the acceleration pipe. 6. The temperature control system for an accelerator tube according to claim 1, wherein the controller performs PID control. 7. A free electron laser device using a linear accelerator equipped with the temperature control system for an acceleration tube according to claim 1. Description: