JP5096893B2 - Microwave ion source equipment - Google Patents

Description

  The present invention relates to a microwave ion source apparatus in which a source gas is excited by microwaves into plasma and extracted as an ion beam.

  In general, in a microwave ion source, a plasma chamber is installed in a high voltage region of several KV to several hundred KV, and ions generated therein are accelerated by an electric field between the plasma chamber and an extraction electrode to form an ion beam. . For this reason, a plasma chamber, a device installed at the same potential as the plasma chamber, and a control device for driving the device are installed in a high voltage region of several KV to several hundred KV (see, for example, Patent Document 1).

  Therefore, normally, as shown in FIG. 8, a microwave ion source (hereinafter referred to as an ion source) 80 and a source gas cylinder 81 for supplying a source gas (for example, hydrogen gas) to the ion source 80, an ion source. An ion source control device 84 such as a source gas flow rate adjusting means (hereinafter referred to as a mass flow controller) 82 for adjusting the source gas flow rate to 80 and a high voltage region side control device 83 for controlling the mass flow controller 82 is connected to a high pressure deck ( It is installed inside the control equipment installation box 85) insulated with insulators and the like. Then, power is supplied to the ion source control device 84 via the power cable 88 using the insulating transformer 87 installed outside the high voltage region 86, and from the low voltage region side, for example, the ground potential region side control device 89. Control signals are transmitted and received by the optical cable 90.

JP-A-9-55170

  In the conventional microwave ion source apparatus, the ion source control device 84 such as the mass flow controller 82 and the high voltage region side control device 83 is installed in the high pressure deck 85 together with the ion source 80 and the raw material gas cylinder 81 as described above. Therefore, the ground potential region side control device 89 such as the high voltage deck 85, the insulating transformer 87, or the optical conversion / voltage conversion device for the control signal is necessary, and the microwave ion source device becomes large and expensive. It was.

  In addition, when the ion source control device 84 is installed inside the high-pressure deck 85, when a spark is generated from the high-pressure deck 85, there is also a problem that the ion source control device 84 malfunctions due to spark noise.

  Further, even in a device in which only an electromagnet is installed in the ground potential region, such as the device disclosed in Patent Document 1, a mass flow controller or a microwave power source is installed in a high voltage region, so that a high voltage deck is required. Become.

  Therefore, in order to eliminate the high-voltage deck and reduce the cost, it is necessary to install a microwave power source or a mass flow controller in the ground potential region. For the microwave power source, a well-known DC cut is provided in the middle of the waveguide. By inserting, the DC potential can be insulated and the microwave power source can be installed in the ground potential region. On the other hand, in order to install the mass flow controller in the ground potential region, it is conceivable to connect the mass flow controller and the ion source with an insulating gas pipe made of an insulating tube or the like to distribute the raw material gas.

However, when the mass flow controller and the ion source are connected by an insulating gas pipe, the gas pressure inside the ion source is reduced to a gas pressure at which plasma can be generated. To several hundred Pa). For this reason, the glow discharge inside the insulating gas pipe cannot be suppressed, and there has been a problem that the ion source operation becomes unstable due to the discharge in the pipe and the insulating gas pipe is damaged.

  In order to suppress the discharge in the insulating gas pipe, the gas pressure in the insulating gas pipe may be increased. For this purpose, as illustrated in FIG. 9, the gas is supplied to the high voltage region 86 where the ion source 80 is installed. It is conceivable to provide a valve 91 that can adjust the flow rate. However, in such a configuration, although discharge in the insulating gas pipe 92 is suppressed, in order to operate the valve 91, the high voltage in the high voltage region 86 is dropped or an insulating rod or the like (not shown) is used. There is a problem that it is difficult to adjust the gas flow rate with high accuracy necessary for adjusting the ion source 80 because it is necessary to open and close the valve 91 and adjust the gas flow rate.

  The present invention has been made to solve the above-mentioned problems, and after reducing the cost, suppresses discharge in the source gas pipe for distributing the source gas to the ion source, and adjusts the source gas flow rate. A microwave ion source apparatus that enables highly accurate gas flow rate adjustment using a means is provided.

A microwave ion source device according to the present invention is a micro ion device that is disposed in a high voltage region and includes an ion source that excites a source gas supplied from a source gas supply source by a microwave into a plasma and extracts it as an ion beam. in the wave ion source device, provided in the high voltage region of the raw material gas pipe flowing the raw material gas supplied from the material gas supply source, a differential pressure forming means for forming a difference between the pressure of the feed gas, the difference And a valve for adjusting the flow rate of the raw material gas to the ion source together with the pressure forming means, and constituting a series connection body in which the differential pressure forming means and the valve are connected in series. In addition, a plurality of the serially connected bodies are arranged in parallel .

  According to the microwave ion source device of the present invention, since the microwave ion source is controlled by a control device placed in a low voltage region, for example, a ground potential region, a high voltage deck or the like is not required, and the cost of the device is reduced. In addition, by placing the control device in a low voltage region, for example, a ground potential region, it is possible to suppress malfunction of the control device due to sparks from the high voltage deck. Furthermore, it is possible to suppress the discharge in the raw material gas pipe and adjust the gas flow rate with high accuracy.

  Preferred embodiments of a microwave ion source apparatus according to the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block configuration diagram of a microwave ion source device according to Embodiment 1 of the present invention. In FIG. 1, an ion source 1 guides a microwave generated by a microwave power source (not shown) to a vacuum chamber (not shown) by a waveguide (not shown) and serves as a source gas supply source. A raw material gas such as hydrogen gas is supplied from the gas cylinder 2, and this raw material gas is excited by microwaves to form plasma. The ion source 1 is installed in the high voltage region 3 and extracts an ion beam from the plasma by an extraction electrode provided at the outlet of the vacuum chamber.

The source gas from the gas cylinder 2 is supplied to the ion source 1 through the first gas pipe 6 constituted by the insulating gas pipe 4 and the non-insulating gas pipe 5. The non-insulating gas pipe 5 is installed in the high voltage region 3, and the insulating gas pipe 4 is installed outside the high voltage region 3. An air drive valve 7 constituting a valve means is installed at a connection portion between the insulating gas pipe 4 and the non-insulating gas pipe 5, and the air drive valve 7 is opened and closed by a remote control valve 8 operating with compressed air. Be controlled.

  A thin tube 9 is connected to a predetermined length portion of the non-insulating gas pipe 5 arranged in the high voltage region 3, and a filter 10 is installed in the upstream portion of the thin tube 9 so that foreign matter does not flow into the thin tube 9. ing. The narrow tube 9 functions as a differential pressure forming means for forming a difference in gas pressure in the high voltage region of the first gas pipe 6.

  The insulating gas pipe 4 is provided with a mass flow controller 11 as a raw material gas flow rate adjusting means and a pressure gauge 12 as a pressure detecting means connected in series. The mass flow controller 11 adjusts the pressure by adjusting the flow rate of the source gas, and thereby performs high-precision gas flow rate adjustment necessary for adjusting the ion source 1.

  Furthermore, in the microwave ion source device according to Embodiment 1, a second gas pipe 13 is provided in parallel with the first gas pipe 6 between the ion source 1 and the gas cylinder 2. Similarly to the first gas pipe 6, the second gas pipe 13 includes a non-insulating gas pipe 14 disposed in the high voltage region 3 and an insulating gas pipe 15 disposed outside the high voltage region 3. Has been. The second gas pipe 13 is also configured to supply the source gas of the gas cylinder 2 to the ion source 1.

  An air driven valve 16 is installed at the connection between the non-insulating gas pipe 14 and the insulating gas pipe 15. The air drive valve 16 is controlled by a remote control valve 17 that operates with compressed air.

  A thin tube 18 is connected to a predetermined length portion of the non-insulating gas pipe 14 installed in the high voltage region 3, and a filter 19 is installed in the upstream portion of the thin tube 18 so that foreign matter does not flow into the thin tube 18. ing. However, the insulating gas pipe 15 constituting the second gas pipe 13 is not provided with a mass flow controller or a pressure gauge as a raw material gas flow rate adjusting means.

  In the above description, the case where the first and second gas pipes are constituted by insulating gas pipes and non-insulating gas pipes has been illustrated and described. However, the first and second gas pipes may be formed of only insulating gas pipes. It may be configured. What is required is that the boundary portion between the high voltage region and the ground potential region is formed of an insulating gas pipe.

The microwave ion source apparatus according to Embodiment 1 is configured as described above, and the operation thereof will be described next.
Since the ion source 1 is installed in a high potential region of several kV to several hundred kV using a high voltage power source, the inside of the insulating gas pipe 4 connecting the high voltage region 3 and the outside of the high voltage region 3 in FIG. The gas pressure cannot be reduced so much. In order to avoid this, the first embodiment is provided with a thin tube 9 that provides a difference in gas pressure in the high voltage region 3.

  Specifically, when the diameter of the thin tube 9 is set to about several tens to several hundreds of μm, when the gas flow rate supplied to the ion source 1 is about 0.1 to 10 ccm, the length is several centimeters and approximately 1 atm. Since a differential pressure can be provided, it is possible to suppress internal discharge of the first and second gas pipes 6.

In order to obtain a desired gas flow rate in the first gas pipe 6 constituted by the insulating gas pipe 4 and the non-insulating gas pipe 5, the length of the narrow tube 9 is determined by the following procedure.
(1) The minimum gas flow rate supplied to the ion source is determined.
(2) Three types of thin tubes having different lengths are prepared, a raw material gas is supplied to one side, a vacuum is applied to one side, and each gas flow rate is measured.
(3) The length of the narrow tube and the gas flow rate are plotted, and the length of the narrow tube corresponding to the gas flow rate is determined.
The length is experimentally determined in this way because the gas flow in the gas pipe is a molecular flow (low pressure) where there is no collision between gas molecules from a viscous flow (atmospheric pressure to low pressure) whose flow velocity is determined by the collision between gas molecules. This is because it is difficult to obtain a theoretical flow rate because it changes to a (˜vacuum) region.

Further, as described above, the following problems remain in the supply of the raw material gas only by the first gas pipe 6 constituted by the insulating gas pipe 4 and the non-insulating gas pipe 5.
That is, the mass flow controller 11 is used to adjust the gas flow rate, but when the gas flow rate is changed by the mass flow controller 11, the gas pressure inside the insulating gas pipe 4 also varies. On the other hand, the range of gas pressure that can be handled by the mass flow controller 11 is not so large, and is generally about 0 to 2 atm. For this reason, in order to suppress the discharge inside the insulating gas pipe 4, if the pressure of about 0.5 atm is required at the minimum, the change range of the internal pressure of the insulating gas pipe is 0.5 to 2 atm. Since the gas flow rate is almost proportional to the pressure change, the flow rate range that can be handled is limited to about four times. On the other hand, the ion source 1 often introduces gas several times to several tens of times at the time of start-up.

  In order to solve this problem, in the first embodiment, the second gas pipe 13 is provided separately from the first gas pipe 6 in which the mass flow controller 11 is installed. As described above, the second gas pipe 13 is provided side by side with the first gas pipe 6, and does not include a mass flow controller as a gas flow rate adjusting means, and can supply a large flow rate gas. Then, only when the ion source 1 is started, the air drive valve 16 provided in the high voltage region 3 is driven using compressed air supplied via the remote control valve 17 so that the ion source 1 is The source gas is supplied through the first gas pipe 6 and the source gas is also supplied through the second gas pipe 13 so that the ion source 1 can be stably ignited.

  Further, since the narrow tubes 9 and 18 are thin, the fine tubes 9 and 18 may be blocked by foreign matters in the gas pipes 5 and 14 and the raw material gas cannot be supplied. Filters 10 and 19 are provided on the upstream side.

  As described above, according to the microwave ion source device according to the first embodiment, since the control of the ion source 1 is performed by the control device placed in the low voltage region, for example, the ground potential region, a high voltage deck or the like becomes unnecessary. It is possible to reduce the cost of the apparatus, and by placing the control device in a low voltage region, for example, a ground potential region, it is possible to suppress malfunction of the control device due to sparks from the high voltage deck. Further, the discharge in the raw material gas pipe is suppressed, and the gas flow rate can be adjusted with high accuracy.

  Further, apart from the first gas pipe 6 where the mass flow controller 11 is installed, a second gas pipe 13 that enables the supply of a large flow rate gas is provided in parallel without providing a mass flow controller as a gas flow rate adjusting means, At the time of starting the ion source 1, since the source gas is circulated through the first gas pipe 6 and the source gas is also circulated through the second gas pipe 13, the ion source 1 can be stably ignited.

Embodiment 2. FIG.
Next, a microwave ion source device according to Embodiment 2 of the present invention will be described. In the first embodiment, when the flow of the raw material gas to the insulating gas pipe is stopped due to a failure of the mass flow controller or the like, there is a possibility that the device is damaged due to the discharge accompanying the decrease in the internal pressure of the gas pipe. The second embodiment can cope with such troubles.

  FIG. 2 is a block diagram of a microwave ion source device according to Embodiment 2 of the present invention. As shown in the figure, the microwave ion source device according to Embodiment 2 includes an upstream side of the mass flow controller 11. And a bypass pipe 20 that connects the downstream side of the pressure gauge 12 is provided. The bypass pipe 20 is provided with a control valve 21 for controlling the gas flow rate of the bypass pipe 20, and the control valve 21 outputs a control signal based on the internal pressure of the insulating gas pipe 4 detected by the pressure gauge 12. It is controlled by a valve controller 22 which is a valve control means. Therefore, the bypass pipe 20 and the control valve 21 function as raw material gas pressure holding means. In addition, about another structure, it is the same as that of Embodiment 1, and description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The microwave ion source apparatus according to Embodiment 2 is configured as described above, and the operation thereof will be described next.
Since the discharge is caused by a pressure drop in the insulating gas pipe 4, the internal pressure of the insulating gas pipe 4 is monitored by the pressure gauge 12. When the gas pressure of the raw material gas becomes lower than a preset gas pressure, this is detected by the valve controller 22 and the control valve 21 provided in the raw material gas bypass pipe 20 is opened. Thereby, the pressure of the raw material gas in the insulating gas piping 4 is raised, and discharge is avoided. The setting of the mass flow controller 11 may be fully opened. However, when the cause of the failure is in the mass flow controller 11, it may not be possible to deal with, and the above configuration is appropriate. Further, as shown in the present embodiment, by combining the mass flow controller 11 and the control of the valve controller 22, the control range of the raw material gas flow rate can be increased during normal operation of the mass flow controller 11. It is possible to cope with the failure of the controller 11, and the installation of the mass flow controller 11 is not essential.

  Further, in order to avoid the discharge due to the pressure drop of the insulating gas pipe 4, if the application does not care much about the impurities of the source gas, as shown in FIG. 3, as shown in FIG. The differential pressure valve 30 is controlled so that air flows in automatically when the gas pressure in the insulating gas pipe 4 decreases by a predetermined value or more, and the gas pressure in the insulating gas pipe 4 is maintained at the predetermined value. In this case, the differential pressure valve 30 functions as a raw material gas pressure holding means. As shown in the present embodiment, by combining the mass flow controller 11 and the control of the differential pressure valve 30, the control range of the raw material gas flow rate can be increased when the mass flow controller 11 is operating normally. As described above, the mass flow controller 11 is not indispensable.

  Further, in order to avoid discharge due to the pressure drop of the insulating gas pipe 4, the internal pressure of the insulating gas pipe 4 is monitored by a pressure gauge 12 as shown in FIG. When it becomes smaller, by using the circuit breaker 40 which is a voltage interruption means, it is configured to stop the high voltage to the ion source 1, so that the mass flow controller 11 or the like fails and the insulating gas pipe 4 is discharged. Even when the flow of the raw material gas is stopped, it is possible to prevent discharge due to a decrease in the internal pressure of the gas pipe and to prevent the equipment from being damaged.

  As described above, according to the microwave ion source device according to the second embodiment, even when the supply of the source gas to the insulating gas pipe 4 is stopped due to a failure of the mass flow controller 10 or the like, the inside of the gas pipe There is no risk of damage to the equipment due to the discharge accompanying the decrease in pressure, and a highly reliable microwave ion source device can be provided.

Embodiment 3 FIG.
Next, a microwave ion source device according to Embodiment 3 of the present invention will be described. FIG.
These are the block block diagrams of the microwave ion source apparatus which concerns on Embodiment 3 of this invention, and this Embodiment controls the flow volume of source gas by using a combination of a plurality of thin tubes.

  In FIG. 5, the raw material gas from the gas cylinder 2 is supplied to the ion source 1 by flowing through a first gas pipe 6 including an insulating pipe 4 and a non-insulating pipe 5. As in the first or second embodiment, the first gas pipe 6 is provided with an air drive valve 7 and a thin tube 9. The air drive valve 7 is a remote control valve 8 that operates with compressed air. It is comprised so that it may be controlled by.

  Similarly to the first gas pipe 6, the first gas pipe 6 is composed of insulating gas pipes 4a to 4c and non-insulating gas pipes 5a to 5c, respectively, and the narrow tubes 9a to 9c and the air drive valve 7a. The second to fourth gas pipes 6a to 6c provided with ~ 7c are juxtaposed with each other. The source gas is also supplied to the ion source 1 by flowing through the second to fourth gas pipes 6a to 6c. The thin tubes 9 and 9a to 9c are configured to have different flow rates, and the air drive valves 7a to 7c are controlled by the remote control valves 8a to 8c that operate with compressed air. Yes. In the third embodiment, the mass flow controller, the pressure gauge, and the filter installed upstream of the thin tubes 9, 9a to 9c are not installed, but the other configurations are the same as in the first embodiment. Yes, the description is omitted by giving the same reference numerals.

The microwave ion source apparatus according to Embodiment 3 is configured as described above, and the operation thereof will be described next.
In the first embodiment, precise gas flow control using a mass flow controller is performed. However, when precise flow rate adjustment is not required, different flow rates are used as in the present embodiment shown in FIG. And the gas supply can be controlled by the air drive valves 7 and 7a to 7c.

  In this case, unless the gas cylinder 2 is emptied, the gas pressure in the insulating gas pipes 4, 4 a to 4 c does not fall below the atmospheric pressure, so the gas supply is stopped due to some trouble as shown in the first embodiment. In this case, discharge does not occur, and it can be applied to applications that require higher reliability.

  In addition, the lengths of the thin tubes 9 and 9a to 9c shown in the present embodiment are set so that the gas flow rate is, for example, 1: 2: 4: 8, thereby opening and closing the air driven valves 7 and 7a to 7c. The gas flow rate can be adjusted to 16 levels from 0 to 15 by the combination. Of course, as shown in the first embodiment, one may be set to a large flow rate for the microwave ion source ignition. Further, if the supply pressure can be changed twice, continuous flow rate control is possible.

Embodiment 4 FIG.
Next, a microwave ion source device according to Embodiment 4 of the present invention will be described. FIG. 6 is a block diagram of a microwave ion source apparatus according to Embodiment 4 of the present invention. In this embodiment, the gas pressure in the insulating gas pipe is not increased, and the insulation is maintained at a low pressure. In order to suppress discharge inside the gas pipe, an embodiment in which a high magnetic field region is provided in a part of the insulating gas pipe is shown.

In FIG. 6, a high magnetic field region 60 is provided in a part of the insulating gas pipe 4. This high magnetic field region 60 applies a magnetic field having a magnetic flux density of several gauss to several k gauss, preferably a magnetic flux density of 100 gauss or more, in order to suppress discharge in the low vacuum region. In addition, it is applied to the vertical method, and discharge is suppressed by limiting the movement of electrons and ions that flow out of the plasma and trigger the discharge. Then, as in the first or second embodiment, the flow rate of the source gas supplied from the gas cylinder 2 to the ion source 1 installed in the high voltage region 3 is precisely adjusted by the mass flow controller 11. In this embodiment, no narrow tube is provided in the insulating gas pipe 4 as in the above embodiments.

  According to the fourth embodiment, the internal pressure of the insulating gas pipe 4 is maintained at a low pressure regardless of the change in the flow rate, so that the setting range of the gas flow rate can be set within the specification range of the mass flow controller 11. In addition, since no thin tube is installed and there is no thin portion in the diameter of the insulating gas pipe 4, there is no fear of clogging with foreign matter.

Embodiment 5 FIG.
Next, a microwave ion source device according to Embodiment 5 of the present invention will be described. FIG. 7 is a block diagram of a microwave ion source device according to Embodiment 5 of the present invention.
When the high magnetic field region 60 is provided in a part of the insulating gas pipe 4 as in the fourth embodiment, the magnetism of the high magnetic field region 60 may affect the magnetic field of plasma generation of the microwave ion source 1. . Therefore, in the fifth embodiment, as shown in FIG. 7, in order to reduce the magnetic field region and avoid interference with the microwave ion source 1, a permanent magnet 70 is used as a magnetic field generating means, and a magnetic shield 71 is provided around the permanent magnet 70. Is provided.

  In the present embodiment, since a high voltage is applied to both ends of the high magnetic field region, if a conductive material including the permanent magnet 70 and the magnetic shield 71 is provided around the insulating gas pipe 4, the insulating gas pipe 4 When the withstand voltage characteristic is low, a discharge is generated through the insulating gas pipe 4. In order to avoid this, an insulator 72 is provided around the insulating gas pipe 4 to improve the withstand voltage characteristics.

  By the way, in each said embodiment, although embodiment which applied this invention to the microwave ion source apparatus was described, this invention uses a microwave, and also applies a vertical magnetic field, and is the same frequency as a microwave frequency. It can be applied to a microwave ion source apparatus including an ECR (Electron Cyclotron Resonance) ion source that causes the electron cyclotron motion of the gas to generate resonance absorption, and can be applied to all of those equipped with an ion source excited by a microwave. is there.

  The microwave ion source device according to the present invention described in detail above is a linear accelerator system and an accelerator system for accelerating an ion beam extracted from the microwave ion source, and medical applications by irradiating a human body with the accelerated ion beam. Medical accelerator system that performs (treatment, sterilization, etc.), high-energy beam application device that performs semiconductor generation, material modification, processing, radioisotope manufacturing, etc. by irradiating the object with the accelerated ion beam , Neutron generator and ion beam process device, microwave plasma source for generating plasma by microwave discharge, and semiconductor generation, material modification, processing by irradiating the object to be processed with plasma generated by microwave discharge It can be applied to a plasma process apparatus that performs the above.

It is a block block diagram of the microwave ion source apparatus which concerns on Embodiment 1 of this invention. It is a block block diagram of the microwave ion source apparatus which concerns on Embodiment 2 of this invention. It is a block block diagram which shows the other example of the microwave ion source apparatus which concerns on Embodiment 2 of this invention. It is a block block diagram which shows the further another example of the microwave ion source apparatus which concerns on Embodiment 2 of this invention. It is a block block diagram of the microwave ion source apparatus which concerns on Embodiment 3 of this invention. It is a block block diagram of the microwave ion source apparatus which concerns on Embodiment 4 of this invention. It is a block block diagram of the microwave ion source apparatus which concerns on Embodiment 5 of this invention. It is a block block diagram of the conventional microwave ion source apparatus. It is a block block diagram of the other conventional microwave ion source apparatus.

Explanation of symbols

1, 80 Ion source 2, 81 Gas cylinder 3, 86 High voltage region 4, 4a-4c, 15, 92 Insulating gas pipe 5, 5a-5c, 14 Non-insulating gas pipe 6 First gas pipe 6a Second Gas piping 6b 3rd gas piping 6c 4th gas piping 7, 7a-7c, 16 Air drive valve 8, 17, 17a-17c Remote control valve 9, 9a-9c, 18 Narrow tube 10, 19 Filter 11, 82 Mass flow Controller 12 Pressure gauge 13 Second gas pipe 20 Bypass pipe 21 Control valve 22 Valve controller 30 Differential pressure valve 40 Circuit breaker 60 High magnetic field area 70 Permanent magnet 71 Magnetic shield 72 Insulator 83 High voltage area side control device 84 Ion source control Equipment 85 High-pressure deck 87 Insulation transformer 88 Power cable 90 Optical cable 91 Valve

Claims (10)

In a microwave ion source apparatus provided with an ion source that is arranged in a high voltage region and is excited by microwaves from a source gas supplied from a source gas supply source into a plasma and extracted as an ion beam.
A differential pressure forming means for forming a difference in the pressure of the raw material gas, provided in a high voltage region portion of the raw material gas pipe for circulating the raw material gas supplied from the raw material gas supply source ;
A valve that is installed in the high voltage region together with the differential pressure forming means and adjusts a raw material gas flow rate to the ion source,
A microwave ion source device comprising a series connection body in which the differential pressure forming means and the valve are connected in series, and a plurality of the series connection bodies are arranged in parallel . 2. The microwave ion source apparatus according to claim 1, wherein a thin tube is used as the differential pressure forming means . Claims, characterized in that the low voltage region part between one and the raw material gas supply source the series connection body, with a raw material gas flow rate adjusting means for adjusting the pressure by adjusting the flow rate of the raw material gas The microwave ion source device according to claim 1 or 2 . A pressure detecting means for detecting the pressure of the raw material gas in the low voltage region between the valve and the raw material gas flow rate adjusting means, and a detection value of the pressure detecting means being lower than a predetermined value; The microwave ion source apparatus according to claim 3, further comprising a source gas pressure holding unit that holds the pressure of the source gas at the predetermined value . The raw material gas pressure holding means is a bypass pipe arranged in parallel with the raw material gas pipe, and a control valve that is installed in the bypass pipe and operates based on a detection value of the pressure detection means. 4. The microwave ion source device according to 4. 5. The microwave ion source device according to claim 4, wherein the source gas pressure holding unit is a differential pressure valve that is installed in the source gas pipe and operates based on a detection value of the pressure detection unit . A pressure detecting means for detecting the pressure of the raw material gas in the low voltage region between the valve and the raw material gas flow rate adjusting means, and a detection value of the pressure detecting means being lower than a predetermined value; The microwave ion source device according to claim 3 , further comprising a voltage cutoff unit that cuts off a high voltage to the ion source. 4. The microwave ion source device according to claim 3 , further comprising a high magnetic field region generating means for generating a high magnetic field region in the low voltage region portion between the valve and the source gas flow rate adjusting means . 9. The microwave ion source device according to claim 8, wherein the high magnetic field region generating means is constituted by a permanent magnet . The microwave ion source device according to claim 8 or 9, wherein a magnetic flux density in a direction perpendicular to a flow direction of the source gas in the high magnetic field region is 100 gauss or more .

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