JP2020030986A - Method for establishing acceleration electric fields in rf cavities at high speed - Google Patents
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本発明は、一台のＲＦ源を用いて、二つの特性が異なるＲＦ空洞を駆動するＲＦ電力とＲＦ電力の出力周波数であるＲＦ周波数をそれぞれの所定の値に高速で到達させ、ＲＦ空洞に所定の電場を形成する、「ＲＦ空洞に加速電場を高速で立ち上げる方法」に関する。 The present invention uses a single RF source to quickly reach an RF power that drives an RF cavity having two different characteristics and an RF frequency that is an output frequency of the RF power to respective predetermined values, and to reach the RF cavity. The present invention relates to a method of forming an electric field at a high speed in an RF cavity.
一．ＢＮＣＴ陽子加速器におけるＲＦ空洞について
特許文献１に示すように、中性子捕捉療法（ＢＮＣＴ）に用いる高周波加速器（ここでは、ＢＮＣＴ陽子加速器）におけるＲＦ空洞はＲＦＱ（Ｒａｄｉｏ Ｆｒｅｑｕｅｎｃｙ Ｑｕａｄｒｕｐｏｌｅ Ｌｉｎａｃ：高周波４重極型リニアック）空洞と、ＤＴＬ（Ｄｒｉｆｔ Ｔｕｂｅ Ｌｉｎａｃ：ドリフトチューブリニアック）空洞の二種類のＲＦ空洞で構成され、その二つのＲＦ空洞は構成と特性が大きく異なっている。
one. Regarding the RF cavity in the BNCT proton accelerator As shown in Patent Document 1, the RF cavity in the high frequency accelerator (here, the BNCT proton accelerator) used for neutron capture therapy (BNCT) is RFQ (Radio Frequency Quadrupole Linac: high frequency quadrupole linac). ) And two types of RF cavities, a DTL (Drift Tube Linac) cavity, and the two RF cavities have greatly different configurations and characteristics.
構成面では、ＲＦＱ空洞とＤＬＴ空洞（以下、単に「それらＲＦ空洞」ともいう）に備えられている共振周波数調整システムが異なっている。ＲＦＱ空洞の共振周波数調整システムは冷却水循環システムを用いて水温で共振周波数を調整する。一方、ＤＴＬ空洞の共振周波数調整システムは冷却水循環システムと可動式機械チューナーを用いて共振周波数を調整する。 In terms of configuration, the resonance frequency adjustment systems provided in the RFQ cavity and the DLT cavity (hereinafter, also simply referred to as “their RF cavities”) are different. The RFQ cavity resonance frequency adjustment system uses a cooling water circulation system to adjust the resonance frequency at the water temperature. On the other hand, the resonance frequency adjustment system of the DTL cavity adjusts the resonance frequency using a cooling water circulation system and a movable mechanical tuner.
他方、ＲＦＱ空洞とＤＬＴ空洞の高周波の特性面では、主に次のような違いがある。
（１）
二つのＲＦ空洞は、負荷品質係数（ｌｏａｄｅｄ ｑｕａｌｉｔｙ ｆａｃｔｏｒ、以下「ＱＬ値」という）が大きく異なっている。ＱＬ値が大きいほうが、ＲＦ空洞の周波数帯域は狭くて、消耗電力は少ない。
ＲＦＱ空洞のＱＬ値は約３５００で、ＤＴＬ空洞のＱＬ値は約１６０００でＲＦＱ空洞のＱＬ値の約５倍である。またＱＬ値が大きく異なっていることから、ＱＬ値に関連するすべての特性が大きく異なっている。例えば、ＲＦ空洞自身の消費電力の割合、ＲＦ空洞のＲＦ立上げ時の充填時間（ｆｉｌｌｉｎｇ ｔｉｍｅ）などが大きく異なっている。
（２）
二つのＲＦ空洞は、ビームに対しての機能と負荷も大きく異なっている。
ＲＦＱ空洞の加速電場はビームを加速しながらｂｕｎｃｈｉｎｇする。ＤＴＬ空洞の加速電場はビームを加速するだけである。
さらに、二つのＲＦ空洞は、ビームに与えるエネルギー及びビーム負荷が異なっている。ＲＦＱ空洞はビームを３ＭｅＶまで加速し、ピーク電流５０ｍＡの場合のビーム負荷は１５０ｋＷである。一方、ＤＴＬ空洞はビームを更に８ＭｅＶまで加速するので、５０ｍＡの場合にビーム負荷は２５０ｋＷとなる。
On the other hand, there are mainly the following differences in the high frequency characteristics of the RFQ cavity and the DLT cavity.
(1)
The two RF cavity, load quality factor (loaded quality factor, hereinafter referred to as "Q L value") is significantly different. More Q L value is large, the frequency band of the RF cavity is narrow, power consumption is small.
Q L value of RFQ cavity is about 3500, Q L value of DTL cavity is about 5 times the Q L values RFQ cavity at about 16000. Further, since the QL values are largely different, all the characteristics related to the QL values are largely different. For example, the ratio of the power consumption of the RF cavity itself, the filling time at the time of RF startup of the RF cavity, and the like are greatly different.
(2)
The two RF cavities also have very different functions and loads on the beam.
The accelerating electric field in the RFQ cavity bunch while accelerating the beam. The accelerating electric field in the DTL cavity only accelerates the beam.
Furthermore, the two RF cavities differ in the energy imparted to the beam and the beam load. The RFQ cavity accelerates the beam to 3 MeV and the beam load is 150 kW for a peak current of 50 mA. On the other hand, the DTL cavity accelerates the beam further to 8 MeV, so at 50 mA the beam load is 250 kW.
二．ＲＦＱ空洞とＤＴＬ空洞を駆動するＲＦ源について
特性の異なる二つのＲＦ空洞であるＦＱ空洞とＤＬＴ空洞を駆動するＲＦ源は、２台の独立なＲＦ源を用いる場合と、一台のＲＦ源で行う場合がある。それぞれの利点と欠点を表１にまとめた。
two. Regarding the RF source driving the RFQ cavity and the DTL cavity The two RF cavities having different characteristics, the FQ cavity and the DLT cavity, are driven by two independent RF sources. May be done. The advantages and disadvantages of each are summarized in Table 1.
通常の加速器研究開発では、複数の特性が異なるＲＦ空洞は、各々独立したＲＦ源で駆動することが一般的である。特に、ＲＦＱ空洞とＤＴＬ空洞の特性は大きく異なっていることから、２台の独立したＲＦ源が必要であるということが今までの常識的な考えであった。 In ordinary accelerator R & D, it is common that a plurality of RF cavities having different characteristics are driven by independent RF sources. Particularly, since the characteristics of the RFQ cavity and the DTL cavity are greatly different, it has been a common sense that two independent RF sources are required.
しかし、ＢＮＣＴ陽子加速器は、大型科学研究施設用ではなく、将来的に多くの医療機関に普及することを目指しているため、できるだけ低コストで、高性能であることが望まれる。 However, since the BNCT proton accelerator is not intended for large-scale scientific research facilities but is intended to be widely used in many medical institutions in the future, it is desirable that the BNCT proton accelerator be as low-cost as possible and have high performance.
従って、低コストと高性能の両立は重要課題で、ＢＮＣＴ陽子加速器では敢えて一台のＲＦ源で二つのＲＦ空洞を駆動する構成を採用し、医療用高周波加速器としての実現性を最優先にすることにした。 Therefore, achieving both low cost and high performance is an important issue, and the BNCT proton accelerator dare adopts a configuration in which two RF cavities are driven by one RF source, placing the highest priority on the feasibility as a medical radio frequency accelerator. It was to be.
三．加速電場立ち上げ制御について
一台のＲＦ源で、二つのＲＦ空洞に、ＲＦ電源をＲＦ周波数で供給して加速電場を形成する場合に、ＬＬＲＦ制御に多くの課題がある。特に、加速電場立ち上げ時の制御は非常に重要で、医療利用できる高周波加速器の要求を満たす性能を実現しなければならない。
three. Acceleration Electric Field Startup Control When a single RF source supplies RF power to two RF cavities at an RF frequency to form an acceleration electric field, LLRF control has many problems. In particular, the control at the time of starting the accelerating electric field is very important, and it is necessary to realize the performance that satisfies the requirements of the medically applicable high-frequency accelerator.
医療用高周波加速器の加速電場立ち上げについて、基本的な要求は二つある。
一つは、加速電場立ち上げの際、それらのＲＦ空洞からの反射電力を同時にできるだけ最小に抑えなければならないことである。
そうしないと、どちらの一方から大きな反射電力があった場合に、設備の重故障を避けるための自動インターロック保護システムが作動し、立ち上げ失敗となり、途中で終了してしまうためである。
There are two basic requirements for setting up the accelerating electric field of a medical high-frequency accelerator.
One is that during the start-up of the accelerating electric field, the reflected power from their RF cavities must be minimized at the same time.
Otherwise, if there is a large reflected power from either one, the automatic interlock protection system for avoiding a serious failure of the equipment will be activated, the start-up will fail, and the operation will be terminated halfway.
もう一つは、加速電場立ち上げの所要時間をできるだけ短くしなければならないことである。目標は５分間以内である。
そうしないと、治療中に加速器運転再開が必要な場合に、患者の待ち時間が長くなって、医療用治療装置としての条件を満たさなくなる。
Second, the time required to start up the accelerating electric field must be as short as possible. The goal is within 5 minutes.
Otherwise, when it is necessary to restart the accelerator during the treatment, the waiting time of the patient becomes longer, and the condition as a medical treatment device is not satisfied.
一方、ＲＦＱ空洞とＤＴＬ空洞の特性は大きく異なっているから、加速電場立ち上げの際に、それらＲＦ空洞の温度と共振周波数は、時間の経過に伴い、それぞれ異なる変化を示し、一般的なＬＬＲＦの手法では、上記の二つの要求を満たすのは非常に困難である。
従って、加速電場立ち上げの制御について、一台のＲＦ源で二つのＲＦ空洞を駆動する場合、二台の場合よりも、より正確かつ精密な制御システムの開発が必要である。
On the other hand, since the characteristics of the RFQ cavity and the DTL cavity are significantly different, when the accelerating electric field is started, the temperature and the resonance frequency of the RF cavity show different changes over time, and a general LLRF cavity. It is very difficult to satisfy the above two requirements by the method of (1).
Therefore, for controlling the start-up of the accelerating electric field, when two RF cavities are driven by one RF source, it is necessary to develop a more accurate and precise control system than when two RF cavities are used.
そこで、本発明は、一台のＲＦ源を用いて、二つの特性が異なるＲＦ空洞を駆動するＲＦ電力とＲＦ電力の出力周波数であるＲＦ周波数をそれぞれの所定の値に高速で到達させ、ＲＦ空洞に所定の電場を形成する、「ＲＦ空洞に加速電場を高速で立ち上げる方法」を提供することを目的とする。 Therefore, the present invention uses a single RF source to cause RF power for driving an RF cavity having two different characteristics and RF frequency, which is the output frequency of RF power, to reach their respective predetermined values at high speed, It is an object of the present invention to provide a "method of quickly setting up an accelerating electric field in an RF cavity" in which a predetermined electric field is formed in a cavity.
（１）
第一ＲＦ空洞及びチューナーを有する第二ＲＦ空洞と、特性が異なる前記第一ＲＦ空洞及び前記第二ＲＦ空洞に、駆動電力であるＲＦ電力をＲＦ周波数で出力、供給することで、前記第一ＲＦ空洞及び前記第二ＲＦ空洞に加速電場を形成させる一台のＲＦ源を備える高周波加速器において、
前記第一ＲＦ空洞及び前記第二ＲＦ空洞の起動時に、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の両方の共振周波数を検出し、
前記ＲＦ源から前記第一ＲＦ空洞及び前記第二ＲＦ空洞に出力する前記ＲＦ電力の前記ＲＦ周波数を、前記検出にて得た前記共振周波数のいずれか一方に一致させるよう変調し、変調した周波数である変調周波数で、前記第一ＲＦ空洞及び前記第二ＲＦ空洞に前記ＲＦ電力を出力するとともに、
前記チューナーを制御して、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の共振周波数を同じにすることで、
前記第一ＲＦ空洞及び前記第二ＲＦ空洞の共振周波数と前記ＲＦ電力の前記ＲＦ周波数を同じにし、
前記第一ＲＦ空洞及び前記第二ＲＦ空洞からの反射電力を低減させることで、
前記ＲＦ源から出力され、前記第一ＲＦ空洞及び前記第二ＲＦ空洞を駆動する前記ＲＦ電力及び前記ＲＦ周波数を所定値に短時間で到達させ、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の加速電場を高速に所定の電場に形成することを特徴とする
ＲＦ空洞に加速電場を高速で立ち上げ方法。
（２）
前記第一ＲＦ空洞がＲＦＱ空洞で、前記第二ＲＦ空洞がＤＴＬ空洞であることを特徴とする
（１）に記載のＲＦ空洞に加速電場を高速で立ち上げ方法。
（３）
前記共振周波数の検出を、ＱＬ値が高い前記ＲＦ空洞から行うことを特徴とする（１）に記載のＲＦ空洞に加速電場を高速で立ち上げ方法。
（４）
前記加速電場高速立ち上げ方法が、ＢＮＣＴ陽子加速器に利用される場合においては、前記ＱＬ値が高いＲＦ空洞が、前記ＤＴＬ空洞であることを特徴とする（３）に記載のＲＦ空洞に加速電場を高速で立ち上げ方法。
とした。
(1)
The first RF cavity having the first RF cavity and the tuner, and the first RF cavity and the second RF cavity having different characteristics are output and supplied with RF power as driving power at an RF frequency, so that the first RF cavity and the second RF cavity have different characteristics. A high frequency accelerator comprising an RF cavity and an RF source for forming an accelerating electric field in the second RF cavity,
Upon activation of the first RF cavity and the second RF cavity, detecting a resonance frequency of both the first RF cavity and the second RF cavity,
The RF frequency of the RF power output from the RF source to the first RF cavity and the second RF cavity is modulated to match one of the resonance frequencies obtained in the detection, and the modulated frequency Outputting the RF power to the first RF cavity and the second RF cavity at a modulation frequency that is
By controlling the tuner to make the resonance frequency of the first RF cavity and the second RF cavity the same,
The resonance frequency of the first RF cavity and the second RF cavity and the RF frequency of the RF power are the same,
By reducing the reflected power from the first RF cavity and the second RF cavity,
The RF power and the RF frequency that are output from the RF source and drive the first RF cavity and the second RF cavity reach a predetermined value in a short time, and the first RF cavity and the second RF cavity A method for rapidly setting up an accelerating electric field in an RF cavity, wherein the accelerating electric field is rapidly formed into a predetermined electric field.
(2)
The method according to (1), wherein the first RF cavity is an RFQ cavity and the second RF cavity is a DTL cavity.
(3)
The method according to (1), wherein the detection of the resonance frequency is performed from the RF cavity having a high QL value.
(4)
Accelerating the accelerating electric field fast startup method, when utilized in BNCT proton accelerator, said Q L value is higher RF cavity, it the RF cavity according to (3) the a DTL cavity How to start electric field at high speed.
And
本発明は、上記構成であるので、次の効果を奏する。
本発明の方法では
（一）従来法に比して、４−１０倍も短く（３−５分に短縮）、加速電場を高速に立ち上げることが可能となる。
（二）ＲＦＱ空洞とＤＴＬ空洞など異なる複数の型のＲＦ空洞を有する高周波加速器に対し、一台のＲＦ源でＲＦ電力供給が可能になる。
（三）加速電場立ち上げの時、ＲＦＱ空洞とＤＴＬ空洞の共振周波数とＲＦ源の出力ＲＦ周波数は同じであり、それらＲＦ空洞からの反射電力を極めて少ないレベルに維持することができる。その結果、高周波加速器の運転維持は容易になるし、高周波加速システム全体（ＲＦ源、ＲＦ ｄｕｍｍｙ ｌｏａｄなど）に対する負荷は最少となり、機器故障確率も低減するので、高周波加速器システム全体は長寿命になる。
（四）加速電場立ち上げの時、入口水温は一定でも高速で立ち上げが可能となる。
（五）ＲＦ源とＬＬＲＦ制御はそれぞれ一台で、建設費用は約半分になり、敷地もコンパクトになり、高周波加速器は小型化できる。
との効果がある。
Since the present invention has the above configuration, the following effects can be obtained.
According to the method of the present invention, (1) the acceleration electric field can be started up at a high speed, which is 4 to 10 times shorter (3 to 5 minutes) than the conventional method.
(2) A single RF source can supply RF power to a high-frequency accelerator having a plurality of different types of RF cavities such as an RFQ cavity and a DTL cavity.
(3) When the accelerating electric field is started, the resonance frequency of the RFQ cavity and the DTL cavity and the output RF frequency of the RF source are the same, and the reflected power from these RF cavities can be maintained at an extremely small level. As a result, the operation and maintenance of the high-frequency accelerator are facilitated, the load on the entire high-frequency accelerator system (RF source, RF dummy load, etc.) is minimized, and the probability of equipment failure is reduced, so that the entire high-frequency accelerator system has a long life. .
(4) When the accelerating electric field is started, it can be started at a high speed even if the inlet water temperature is constant.
(5) The RF source and the LLRF control are each one, and the construction cost is reduced by about half, the site is compact, and the high frequency accelerator can be downsized.
Has the effect.
以下、添付の図面を参照し、本発明の実施の形態について、従来技術と対比しながら、詳細に説明する。なお、本発明は下記形態例に限定されるものではない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings in comparison with the related art. The present invention is not limited to the following embodiment.
・従来技術
加速電場を所定の値に立ち上げる従来技術は、図１（１）に示すように、「ＲＦ空洞の共振周波数を加速器運転周波数ｆ０に維持しながら、徐々にＲＦ源の出力ＲＦ電力を上げる」方法であった。
なお、図１の記号の意味は次の通りである。
ｆ０：加速器運転周波数
ｆ１：ＲＦＱ共振周波数
ｆ２：ＤＴＬ共振周波数
ｆｒｆ：ＲＦ源の出力ＲＦ周波数
· Prior art accelerating electric field of the prior art launching a predetermined value, as shown in FIG. 1 (1), while keeping the resonant frequency of the "RF cavity accelerator operation frequency f 0, and gradually the output RF of the RF source It was a way to "power up."
The meanings of the symbols in FIG. 1 are as follows.
f 0 : accelerator operating frequency f 1 : RFQ resonance frequency f 2 : DTL resonance frequency f rf : output RF frequency of RF source
従来技術では、ＲＦＱ空洞３及びＤＴＬ空洞４の立ち上げの際は、加速器運転周波数ｆ０を持つ一台のＲＦ源２から、徐々に、ＲＦ源の出力ＲＦ電力を上げて、それらＲＦ空洞に与える。そうすると、それらＲＦ空洞が昇温するので、それらＲＦ空洞に付いている共振周波数調整システムを使って、それらＲＦ空洞のＲＦＱ共振周波数ｆ１及びＤＴＬ共振周波数ｆ２を、共に、加速器運転周波数ｆ０に近づけていく。 In the prior art, upon start-up of the RFQ cavity 3 and DTL cavity 4, from a single RF source 2 with accelerator operating frequency f 0, gradually increasing the output RF power of the RF source, their RF cavity give. Then, since the RF cavities heat up, the RFQ resonance frequency f 1 and the DTL resonance frequency f 2 of the RF cavities are both changed to the accelerator operating frequency f 0 by using the resonance frequency adjusting system attached to the RF cavities. Approaching.
ＲＦＱ空洞３は冷却水６の入口水温を調整することで、ＲＦＱ共振周波数ｆ１を加速器運転周波数ｆ０に維持する。一方、ＤＴＬ空洞４は冷却水６の入口水温調整とチューナー５の調整で、ＤＴＬ共振周波数ｆ２を加速器運転周波数ｆ０に維持する。 RFQ cavity 3 by adjusting the inlet temperature of the cooling water 6, to maintain the RFQ resonance frequency f 1 to the accelerator operation frequency f 0. On the other hand, DTL cavity 4 by adjusting the inlet water temperature adjusting a tuner 5 the cooling water 6, to maintain the DTL resonant frequency f 2 to the accelerator operation frequency f 0.
このような調整を行うことで、それらＲＦ空洞からの反射電力をある設定した閾値の以内に維持しながら、少しずつＲＦ源の出力ＲＦ電力を高めていく必要がある。冷却水６を提供する冷却水循環システムは、一回の温度調整に相当時間がかかるため、通常水温から目標水温まで安定するには１０分以上必要である。 By performing such an adjustment, it is necessary to gradually increase the output RF power of the RF source while maintaining the reflected power from the RF cavities within a set threshold. Since the cooling water circulation system that provides the cooling water 6 takes a considerable amount of time for one temperature adjustment, it takes 10 minutes or more to stabilize from the normal water temperature to the target water temperature.
従って、ＲＦ源２は時間をかけて、少しずつ出力ＲＦ電力を高めいくしかない。そうしないと、共振周波数の維持が間に合わない。実際ＢＮＣＴ陽子加速器では、この従来の方法を使って要求された出力までにＲＦを立ち上げるのに、約２０分〜３０分ぐらいの時間が必要である。 Therefore, the RF source 2 has no choice but to gradually increase the output RF power over time. Otherwise, the maintenance of the resonance frequency cannot be made in time. In fact, in the BNCT proton accelerator, it takes about 20 to 30 minutes to raise RF to the required output using this conventional method.
故に、従来技術の方法では、加速電場立ち上げの時間がかかるため、医療用の施設としての要求を満たすことができない。その問題を解決しないと、ＢＮＣＴ陽子加速器は最終的に普及可能な信頼できる医療装置に至らない。 Therefore, according to the method of the related art, since it takes time to start up the accelerating electric field, it cannot meet the requirements as a medical facility. Unless that problem is solved, the BNCT proton accelerator will not eventually become a viable and reliable medical device.
ここで、従来技術を整理すると、
ＢＮＣＴ陽子加速器のような高周波加速器において、一台のＲＦ源を用いて、二つの特性が異なる第一ＲＦ空洞（ＲＦＱ空洞）、チューナーを備える第二ＲＦ空洞（ＤＴＬ空洞）に加速電場を所定の値に到達させる立ち上げ方法であって、
前記ＲＦ源から前記第一ＲＦ空洞及び第二ＲＦ空洞に前記高周波加速器の加速器運転周波数を持つ加速電場を供給し、
前記第一ＲＦ空洞及び前記第二空洞が共振するように、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の冷却水の水温及びチューナーを調整することで、前記第一ＲＦ空洞及び前記第二空洞からの反射を低減させる共振調整工程を経た後、
前記ＲＦ源の出力ＲＦ電力を上げて前記前記第一ＲＦ空洞及び前記第二ＲＦ空洞の温度を上昇させることで前記共振にズレを生じさせ昇温工程を行い、
再び、前記前記第一ＲＦ空洞及び前記第二ＲＦ空洞が共振するように、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の前記冷却水の水温及び前記チューナーを調整し、前記第一ＲＦ空洞及び前記第二空洞からの反射を低減させる再共振調整工程を経る、
一連の前記共振調整工程、昇温工程、再共振調整工程を、
前記ＲＦ源の出力ＲＦ電力が所定の値に到達するまで繰り返す、立ち上げ方法を採用していた。
Here, when the prior art is organized,
In a high-frequency accelerator such as a BNCT proton accelerator, a single RF source is used to apply an acceleration electric field to a first RF cavity (RFQ cavity) having two different characteristics and a second RF cavity (DTL cavity) having a tuner. Start-up method to reach the value,
Supplying an accelerating electric field having an accelerator operating frequency of the high-frequency accelerator to the first RF cavity and the second RF cavity from the RF source;
The first RF cavity and the second cavity are adjusted by adjusting the cooling water temperature and the tuner of the first RF cavity and the second RF cavity so that the first RF cavity and the second cavity resonate. After a resonance adjustment step to reduce reflection from
Raising the temperature of the first RF cavity and the second RF cavity by raising the output RF power of the RF source to cause a shift in the resonance and perform a temperature raising step,
Again, the water temperature and the tuner of the cooling water of the first RF cavity and the second RF cavity are adjusted so that the first RF cavity and the second RF cavity resonate, and the first RF cavity and Through a re-resonance adjustment step of reducing reflection from the second cavity,
A series of the resonance adjustment step, a temperature raising step, a re-resonance adjustment step,
A start-up method of repeating until the output RF power of the RF source reaches a predetermined value has been adopted.
ＲＦ空洞の温度調整は、水冷機構であり、水の温度を設定してからＲＦ空洞の温度が安定するまで数分以上かかる。従来技術における、上記繰り返しサイクルは数十サイクル必要であり、２０分から３０分の立ち上げ時間を要している。医療用高周波加速器などでは患者を待たせる必要があるなど著しい時間的損失が避けられない。 The adjustment of the temperature of the RF cavity is a water cooling mechanism, and it takes several minutes or more until the temperature of the RF cavity is stabilized after setting the temperature of the water. In the prior art, the repetition cycle requires several tens of cycles, and requires a startup time of 20 to 30 minutes. In medical high-frequency accelerators and the like, significant time loss is inevitable, such as the need to make patients wait.
・本発明
他方、本発明は、図１（２）に示すように、主に、ＢＮＣＴ用に「二つの特性が異なるＲＦ空洞に対して、一台のＲＦ源の出力ＲＦ周波数変調よるＲＦ空洞の加速電場早い立ち上げ方法」という新しい技術を開発した。
具体的には、ＲＦＱ空洞３及びＤＴＬ空洞４の立ち上げの際は、ＱＬ値が高いＲＦ空洞、ＢＮＣＴ陽子加速器ではＤＴＬ空洞４の共振周波数ｆ２を検出して、ＲＦ源の出力ＲＦ周波数ｆｒｆをＤＴＬ共振周波数ｆ２に変調し、それらＲＦ空洞に出力する。同時にＤＴＬ空洞４のチューナー５を調整して、ＤＴＬ空洞４のＤＴＬ共振周波数ｆ２をＲＦＱ共振周波数ｆ１にする。
そうすると、それらＲＦ源の出力ＲＦ周波数ｆｒｆとＤＴＬ空洞の共振周波数ｆ２とＲＦＱ空洞の共振周波数ｆ１、その三つの周波数は同じになるため、それらＲＦ空洞からの反射電力は同時に最小に維持できる。その理由は、ＲＦ電力はＲＦ空洞に入る時、そのＲＦ電力のＲＦ周波数により、ＲＦ空洞内で形成した加速電場と、ＲＦ空洞からの反射電力が変わる。ＲＦ周波数はＲＦ空洞の共振周波数で、ＲＦ空洞内に形成した電場は最大となり、ＲＦ空洞からの反射電力は最小となる。
従って、ＲＦ源の出力ＲＦ電力が所定の値に到達する時間を大幅に短縮することが可能となる。
本発明の方法によれば、立ち上げ中も冷却水入口温度は一定のままでよく、その点からも、加速電場高速立ち上げが可能である。
The present invention On the other hand, as shown in FIG. 1 (2), the present invention is mainly used for BNCT for “RF cavities by RF power modulation of one RF source for RF cavities having two different characteristics. A new technology called "Rapid start-up method of the accelerating electric field".
Specifically, upon start-up of the RFQ cavity 3 and DTL cavity 4, Q L value is high RF cavity, in BNCT proton accelerator and detects the resonance frequency f 2 of the DTL cavity 4, the output RF frequency of the RF source modulate f rf to the DTL resonance frequency f 2 and output to those RF cavities. At the same time by adjusting the tuner 5 the DTL cavity 4, the DTL resonance frequency f 2 of the DTL cavity 4 in RFQ resonance frequency f 1.
Then, since the output RF frequency f rf of these RF sources, the resonance frequency f 2 of the DTL cavity, and the resonance frequency f 1 of the RFQ cavity become the same, the reflected power from these RF cavities is simultaneously kept at a minimum. it can. The reason is that when the RF power enters the RF cavity, the RF frequency of the RF power changes the accelerating electric field formed in the RF cavity and the reflected power from the RF cavity. The RF frequency is the resonance frequency of the RF cavity, the electric field formed in the RF cavity becomes maximum, and the reflected power from the RF cavity becomes minimum.
Therefore, the time required for the output RF power of the RF source to reach the predetermined value can be significantly reduced.
According to the method of the present invention, the cooling water inlet temperature may be kept constant during the startup, and from that point, the acceleration electric field can be started at a high speed.
そして、ＢＮＣＴ陽子加速器の立ち上げ試験では、冷却水６の入口水温を一定にして、本発明の新しい加速電場立ち上げの方法を適用すると、加速電場立ち上げの時間は、従来の２０分〜３０分から、３分〜５分に短縮することができた。
この新しいＲＦの立ち上げの方法である本発明は、現時点で同類の高周波加速器において、はじめての研究開発、実用例である。
In the start-up test of the BNCT proton accelerator, when the inlet water temperature of the cooling water 6 is kept constant and the new method of starting up the accelerating electric field of the present invention is applied, the time required for starting up the accelerating electric field is 20 minutes to 30 minutes. Minutes to 3-5 minutes.
The present invention, which is a method of starting up a new RF, is the first R & D and practical example of a high-frequency accelerator of the same kind at present.
図２に、（１）従来技術と、（２）本発明を適用したＢＮＣＴ陽子加速器における加速電場立上げの試験結果を示した。 FIG. 2 shows the test results of (1) the prior art and (2) the start-up of the accelerating electric field in the BNCT proton accelerator to which the present invention is applied.
図２の記号の意味は次の通りである。
ｐｆ＿ｋｌｙ：ＲＦ源（ここではｋｌｙｓｔｒｏｎ）の出力ＲＦ電力
Ｐｒ＿ＲＦＱ：ＲＦＱ空洞からの反射電力
Ｐｒ＿ＤＴＬ：ＤＴＬ空洞からの反射電力
Ｄｆｒｑ＿ＤＴＬ＝ｆ２−ｆ０
Ｄｆｒｑ＿ＲＦＱ＝ｆ１−ｆ０
ｆ０：加速器運転周波数
ｆ１：ＲＦＱ共振周波数
ｆ２：ＤＴＬ共振周波数
The meanings of the symbols in FIG. 2 are as follows.
pf_kly: output RF power of RF source (here, klystron) Pr_RFQ: reflected power from RFQ cavity Pr_DTL: reflected power from DTL cavity Dfrq_DTL = f 2 −f 0
Dfrq_RFQ = f 1 −f 0
f 0 : accelerator operating frequency f 1 : RFQ resonance frequency f 2 : DTL resonance frequency
試験条件は、加速器の運転繰り返しは５０Ｈｚ、ＲＦ幅は１ｍｓ、ＲＦ源の出力ＲＦ電力の所定値は８５０ｋＷ、加速器運転周波数（ｆ０）は３２４ＭＨｚである。 The test conditions were as follows: the repetition of the accelerator operation was 50 Hz, the RF width was 1 ms, the predetermined value of the output RF power of the RF source was 850 kW, and the accelerator operation frequency (f 0 ) was 324 MHz.
従来技術では、（１）のグラフに、ＲＦ源の出力ＲＦ電力が、縦軸０から所定値まで、つまり、加速電場立上げ所要時間は２０〜３０分であった。他方、本発明では、（２）のグラフに、ＲＦ源の出力ＲＦ電力が０から所定値まで、また両空洞（ＲＦＱ空洞とＤＴＬ空洞）の共振周波数ｆ１及びｆ２が加速器運転周波数ｆ０と一致するまで、すなわち、縦軸において、Ｄｆｒｑ＿ＲＦＱ＝ｆ１−ｆ０＝０、Ｄｆｒｑ＿ＤＴＬ＝ｆ２−ｆ０＝０になるまで、つまり、加速電場立上げ所要時間は３〜５分に短縮され、加速電場高速立ち上げ方法であることがわかる。 In the prior art, in the graph of (1), the output RF power of the RF source is from the vertical axis 0 to a predetermined value, that is, the time required to start up the acceleration electric field is 20 to 30 minutes. On the other hand, in the present invention, (2) the graph of the output RF power of the RF source is 0 to a predetermined value, also coincides with the resonance frequencies f1 and f2 is the accelerator operating frequency f 0 of the two cavities (RFQ cavity and the DTL cavity) Until, ie, on the vertical axis, Dfrq_RFQ = f 1 −f 0 = 0 and Dfrq_DTL = f 2 −f 0 = 0 , that is, the time required to start up the acceleration electric field is reduced to 3 to 5 minutes, It turns out that it is an electric field high-speed starting method.
グラフに、ＲＦ源の出力ＲＦ電力が０（縦軸）から所定値まで、また両空洞（ＲＦＱ空洞とＤＴＬ空洞）の共振周波数が加速器運転周波数と一致（特にＤＴＬ空洞の共振周波数が加速器運転周波数と一致）なったころから、つまり、加速電場立ち上げ時間は、２分５０秒であることがわかる。 The graph shows that the output RF power of the RF source ranges from 0 (vertical axis) to a predetermined value, and that the resonance frequencies of both cavities (RFQ cavity and DTL cavity) match the accelerator operating frequency (particularly, the resonance frequency of the DTL cavity is the accelerator operating frequency). It can be seen from the time when the above-mentioned condition is satisfied), that is, the acceleration electric field start-up time is 2 minutes and 50 seconds.
図３の記号の意味は次の通りである。
Ｄｆｒｑ＿ＲＦＱ＝ｆ１−ｆ０
Ｄｆｒｑ＿ＤＴＬ＝ｆ２−ｆ０
その中
ｆ０：加速器運転周波数
ｆ１：ＲＦＱ共振周波数
ｆ２：ＤＴＬ共振周波数
ｐｆ＿ｋｌｙ／１０：ＲＦ源（ここではｋｌｙｓｔｒｏｎ）の出力ＲＦ電力の１０分の１という
Ｐｒ＿ＲＦＱ：ＲＦＱ空洞からの反射電力
Ｐｒ＿ＤＴＬ：ＤＴＬ空洞からの反射電力
The meanings of the symbols in FIG. 3 are as follows.
Dfrq_RFQ = f 1 −f 0
Dfrq_DTL = f 2 −f 0
Among them, f 0 : accelerator operating frequency f 1 : RFQ resonance frequency f 2 : DTL resonance frequency pf_kly / 10: Pr_RFQ: 1/10 of the output RF power of the RF source (here, klystron): Pr_DTL: reflected power from the RFQ cavity : Power reflected from DTL cavity
試験条件は、加速器の運転繰り返しは５０Ｈｚ、ＲＦ幅は１ｍｓ、ＲＦ源の出力ＲＦ電力の所定値は８５０ｋＷ、加速器運転周波数（ｆ０）は３２４ＭＨｚである。 The test conditions were as follows: the repetition of the accelerator operation was 50 Hz, the RF width was 1 ms, the predetermined value of the output RF power of the RF source was 850 kW, and the accelerator operation frequency (f 0 ) was 324 MHz.
本発明は、医療用分野において、低コスト、省スペースで、医療用高周波加速器を提供することができる。 INDUSTRIAL APPLICABILITY The present invention can provide a low-cost, space-saving medical high-frequency accelerator in the medical field.
１ ＬＬＲＦシステム
２ ＲＦ源
３ ＲＦＱ空洞
４ ＤＴｌ空洞
５ チューナー
６ 冷却水
1 LLRF system 2 RF source 3 RFQ cavity 4 DTl cavity 5 Tuner 6 Cooling water
Claims (4)
前記第一ＲＦ空洞及び前記第二ＲＦ空洞の起動時に、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の両方の共振周波数を検出し、
前記ＲＦ源から前記第一ＲＦ空洞及び前記第二ＲＦ空洞に出力する前記ＲＦ電力の前記ＲＦ周波数を、前記検出にて得た前記共振周波数のいずれか一方に一致させるよう変調し、変調した周波数である変調周波数で、前記第一ＲＦ空洞及び前記第二ＲＦ空洞に前記ＲＦ電力を出力するとともに、
前記チューナーを制御して、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の共振周波数を同じにすることで、
前記第一ＲＦ空洞及び前記第二ＲＦ空洞の共振周波数と前記ＲＦ電力の前記ＲＦ周波数を同じにし、
前記第一ＲＦ空洞及び前記第二ＲＦ空洞からの反射電力を低減させることで、
前記ＲＦ源から出力され、前記第一ＲＦ空洞及び前記第二ＲＦ空洞を駆動する前記ＲＦ電力及び前記ＲＦ周波数を所定値に短時間で到達させ、前記第一ＲＦ空洞及び前記第二ＲＦ空洞の加速電場を高速に所定の電場に形成することを特徴とする
ＲＦ空洞に加速電場を高速で立ち上げ方法。 The first RF cavity having the first RF cavity and the tuner, and the first RF cavity and the second RF cavity having different characteristics are output and supplied with RF power as driving power at an RF frequency, so that the first RF cavity and the second RF cavity have different characteristics. A high frequency accelerator comprising an RF cavity and an RF source for forming an accelerating electric field in the second RF cavity,
Upon activation of the first RF cavity and the second RF cavity, detecting a resonance frequency of both the first RF cavity and the second RF cavity,
The RF frequency of the RF power output from the RF source to the first RF cavity and the second RF cavity is modulated to match one of the resonance frequencies obtained in the detection, and the modulated frequency Outputting the RF power to the first RF cavity and the second RF cavity at a modulation frequency that is
By controlling the tuner to make the resonance frequency of the first RF cavity and the second RF cavity the same,
The resonance frequency of the first RF cavity and the second RF cavity and the RF frequency of the RF power are the same,
By reducing the reflected power from the first RF cavity and the second RF cavity,
The RF power and the RF frequency, which are output from the RF source and drive the first RF cavity and the second RF cavity, reach a predetermined value in a short time, and the first RF cavity and the second RF cavity A method for rapidly setting up an accelerating electric field in an RF cavity, wherein the accelerating electric field is rapidly formed into a predetermined electric field.
請求項１に記載のＲＦ空洞に加速電場を高速で立ち上げ方法。 The method of claim 1, wherein the first RF cavity is an RFQ cavity and the second RF cavity is a DTL cavity.
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