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High-power (1 MW), long-pulse operations up to 300 s were demonstrated by multi-frequency oscillations at 170 GHz, 137 GHz, and 104 GHz. A multi-frequency gyrotron based on the design of the ITER gyrotron has been developed and studied. By redesigning the built-in mode convertor and internal mirrors of the ITER gyrotron, the internal scattered power of the gyrotron was reduced while maintaining the same output beam size and beam direction for the three frequencies. In addition, the mirrors of a matching optics unit were designed to efficiently couple the RF beam at 170 GHz, 137 GHz, and 104 GHz oscillations to a waveguide 50 mm in diameter, the same size that will be used in ITER. An HE 11 mode content of ∼94% was achieved for the three frequencies. Output powers of 1 MW at 170 GHz and 137 GHz, and 0.9 MW at 104 GHz were demonstrated up to 300 s. These oscillation frequencies can facilitate in a wide range of toroidal magnetic field operations at ITER, including plasma start-up and electron heating and current drive.

量子科学技術研究開発機構では，国際熱核融合実験炉 ITER 用ジャイロトロンの研究開発を進めてきた．ITER で期待される 1 MW 出力での繰り返し連続運転に対して，空胴共振器の熱負荷を低減させた高次数 TE31,11モードのジャイロトロン試作機を開発した．この開発研究では，TE31,11モードの発振を阻害する不要な周波数の異なるモードの存在が明らかとなり，その発振抑制を実現する運転手法を開発し，安定した 1 MW 出力の定常運転を実証した．この成果をもとに，ITER ジャイロトロン実機の製作を開始し，２機のジャイロトロンの性能確認試験を完了させた．双方ともに出力 1 MW かつ効率５０％ の３００秒定常運転，0.8 MW 以上の６０秒間 5 kHz 出力変調運転，出力 1 MW／３００秒 の２０ショット高繰り返し運転にて運転信頼度９０％以上を達成し，ITER の要求条件を満足した．

量研では、全8機のITERジャイロトロン実機の製作を完了し、5機の性能試験を実施し、出力1MW/効率50％/300秒発振の高繰り返し運転を90%以上の運転信頼度で成功させている。また、ITERの幅広い運転領域に対応するために複数周波数ジャイロトロンの開発研究も進めている。開発試験では、狙い通りに170GHzと137GHz発振では1MW/300秒、104GHz発振では0.9MW/300秒という単一ジャイロトロンによる3周波数での高出力連続運転を成功させた。, 核融合エネルギー連合講演会

ITERをはじめとする大型トカマク装置で運用される1MW級電子サイクロトロン加熱電流駆動システムでは、あらゆる磁場配位に対して入射モード(O/X)を制御する目的で低損失のマイターベンド型偏波器が用いられる。本研究では、偏波器の応答関数を抽出し、偏波器を擁する伝送路から真空容器への出力偏波の計算手法を確立した。実際の伝送系を用いて検証を実施した結果、計算と実測偏波の差は十分小さく、モード純度98.5%以上を達成できることが分かった。本手法はITER水平ランチャー内部の可動ミラーの反射角を考慮した偏波計算にも適用できる。, 第14回核融合エネルギー連合講演会

JT-60SAの初期研究フェーズで用いられるECH/CD装置（138GHz/110GHz/82GHz）について伝送路のレイアウト設計と評価を行った。新たに設計したレイアウトでの伝送効率を評価するために、これまで考慮されてこなかった、伝送路を構成する導波管の接合部におけるミスアライメントによる傾きや、伝搬するミリ波の偏波角も考慮した、従来よりも現実に即した伝送損失の計算を行ってきた。今回、本計算の妥当性を評価するため、既存の伝送路を使用して、伝送効率を測定し、計算値と比較した。その結果、計算結果が実験結果とよく一致し、計算が現実の伝送効率をよく表すことが明らかとなった。新レイアウトの伝送効率は本計算によると、入射ポートまでの距離の長い系統で84%、より短距離の系統では87%（いずれも110GHz）であり、目標値である伝送効率80%以上を見込めるレイアウトとなっていることが分かった。また、本伝送路では2台の偏波器を用いた偏波制御を行うが、伝送路上に配置する偏波器の位置に依存して3周波数の一部に生成できない偏波が存在する。そこで、新レイアウト上での偏波器の位置に対する出力可能な偏波状態を総当たりで計算し、プラズマ実験で必要となる偏波状態と比較、その差が最小となる偏波器の最適な位置を求めた。これにより、新レイアウトにおいて3周波数いずれもプラズマ入射時のモード純度99%以上が達成可能な偏波器の配置に成功した。, 第14回核融合エネルギー連合講演会

On JT-60SA an integrated commissioning has been conducting. During the integrated commissioning phase, measurements of the transmission efficiency and the conditioning of the ECRF TLs have been carried out. In order to evaluate the transmission efficiency, the RF power was calorimetrically measured at the dummy loads (DLs) installed at two different positions close to the gyrotron and the end of each TL. As a result, the transmission efficiency was evaluated to be 70% for Unit 1, and 81-85% for three frequencies of Unit 2. The commissioning and conditioning of the ECRF systems has also been conducted. The progress of the commissioning is also reported., Korea-Japan Workshop on Physics and Technology of Heating and Current Drive

量研は、ITER国内機関として8機のジャイロトロンを調達する。ITERジャイロトロンは、2016年より製作を開始して、2021年5月に8機目が完了した。これらのジャイロトロンは、量研のテストスタンドにて性能確認試験を順次実施しており、周波数170GHz/出力1MW/効率50％/運転信頼度90%/5kHz出力変調といった試験要件に対して、既に4機が完遂し、現在5機目が試験中である。一方、ITER機構からの研究要請により170GHz/104GHzの2周波数ジャイロトロンの設計開発も行ってきた。現在、2周波数ジャイロトロン試作機を製作中であり、10月から実証試験を開始する計画である。, 第38回 プラズマ・核融合学会 年会

This paper presents a progress of the achievement of performance tests of ITER-gyrotrons developed in QST and design of dual-frequency (170 GHz and 104 GHz) gyrotron to enhance various operation scenarios in ITER such as characteristics studies of H-mode/ELM at low magnetic field. Major achievements of the ITER gyrotron developments are as follows: (i) Manufacturing of 6 out of 8 sets of ITER gyrotrons was completed. Factory acceptance test (FAT) in QST has been progressed and 2 of 6 gyrotrons achieved required specifications such as 1 MW / 300 s / 50 %, 5 kHz modulation with ≥ 0.8 MW etc. The 50 mm diameter waveguide transmission-line and a matching optics unit (MOU) for ITER were newly introduced to perform the operation test at the same environment as ITER-site and excitation of HE11 mode purity of ≥ 95 % at the waveguide inlet was also successfully demonstrated, satisfying the requirement. (ii) Design of dual-frequency gyrotron, which is able to operate continuous wave of 1 MW power, was successfully completed., 28th IAEA Fusion Energy Conference (FEC 2020)

In many tokamak devices in the world, electron cyclotron wave heating plays an important role in plasma control, and polarization control by polarizers is essential to select an appropriate injection mode. Generally, a polarizer internally decomposes the input electric field into two orthogonal components (fast polarization and slow polarization) and generates a phase difference between those components to produce a polarization different from the input. Therefore, the response of a polarizer is characterized by two parameters: the angle at which the electric field is decomposed and the generated phase difference. In Stokes space, each polarization is represented as a vector, and it is known that a rotation operator represents the response of a polarizer. In this presentation, we propose the new method to determine polarizers' response parameters by converting the input and output polarizations into Stokes vectors to identify the rotation operators from a necessary and sufficient dataset. In the conventional method, the measured electric field components are analyzed in real space, and the equation for determining the response parameters of the polarizer tends to be complicated. However, by considering the polarizer's response geometrically in Stokes space, the response parameters can be determined more prospectively. In order to confirm the analysis method, a polarization measurement were carried out using a horn antenna detector and two polarizers for 110/138 GHz transmission lines. The method to determine the response parameters of one polarizer and to simultaneously determine the response parameters of two polarizers were verified. In both cases, it was confirmed that the output polarizations calculated from the determined response parameters agreed with the measured polarizations with a purity of more than 99%., Korea-Japan Workshop on Physics and Technology of Heating and Current Drive

現在JT-60SAのECRF設備のコミッショニングが進められている。今回統合コミッショニング期において使用される二系統のECRF設備について、伝送路の損失と伝送効率を評価するための熱量測定を行った。計測の結果、小口径導波管を用いている1号機では60%の、大口径導波管を用いている2号機では三周波数いずれに対しても81-85%の伝送効率を得た。本会議では熱力測定および伝送路中の各要素における損失評価の結果と、現在までに進められているECRF設備のコミッショニングの進捗について報告する。, Korea-Japan Workshop on Physics and Technology of Heating and Current Drive

ITERにおける電子加熱/電流駆動(ECH/ECCD)用の水平ポートランチャーは量研機構により調達される予定であり、2021年の最終設計レビューに向けて設計が進められている。これに対して量研機構では昨年度、ITER機構が指定する導波管の配置に準拠すると同時に加熱/電流駆動特性の要求値を満足させるための光学設計を最終化させることに成功した。本報告では、トカマク配位安定化のための電流分布制御に関する計算の進捗を含む、水平ランチャーの現設計から想定されるプラズマの加熱/電流駆動特性を報告した。, 第37回 プラズマ・核融合学会 年会

JADAの調達機器であるITER水平ランチャーの光学設計は昨年度に最終化された。本発表では、水平ランチャーの最新の光学設計に基づいてプラズマブレークダウン時の水平ランチャーの運用方法について調査することを目的として、真空容器中での電子サイクロトロン波の吸収パワーを評価した。, 31st Symposium on Fusion Technology (SOFT2020)

We developed a prototype low reflection dummy load for calorimetric power measurements in high-power millimeter wave systems. The dummy load is featured by low reflection of millimeter waves by an internal cylinder designed for increasing the length of the ray trajectory in the dummy load. This structure prevents the millimeter wave reflection from the dummy load by absorbing the waves by the inner surface of the cylinder. Initial tests at high powers of up to 0.5MWfor 0.25 s were successfully able to measure output power with lower reflection back to the source than that of conventional short pulse dummy loads used in the past.

A gyrotron and a matching optics unit (MOU) for the multi-frequency electron cyclotron heating and current drive (ECH/CD) system in JT-60SA have been developed successfully. The gyrotron demonstrated stable operation at high powers of 1.5 MW for 5 s and 1.9 MW for 1 s at 110 GHz. To obtain high HE11 mode purity (> 90%) at the outlet of the waveguide in the ECH/CD launcher, a MOU for operating at three frequencies of 82 GHz, 110 GHz, and 138 GHz that includes three pairs of water-cooled phase correcting mirrors has been developed, which allows the mirrors to be changed without opening the evacuated MOU. The mode purity at the inlet of a dummy load in the transmission line was evaluated at high-power and an HE11 mode purity of > 90% was obtained at three frequencies.

Temperature rise of the waveguide transmission line for high-power long-pulse ECH/CD system has been evaluated experimentally using the dummy load transmission line in JT-60SA. It has been demonstrated that the waveguide components with the inner diameter of 60.3 mm are applicable for 1 MW/100 s transmission at 110/138 GHz required in JT-60SA. A newly developed pre-load installed in front of the dummy load reduced the temperature rise of the waveguide due to the reflection from the dummy load. With this pre-load, the temperature rise distribution in the 37 m-long test transmission line was measured to simulate the real transmission line condition for tokamak experiment. As a result of the high-power experiments, it has been clarified that the temperature of the waveguides close to miter-bends could be increased by approximately 120 K for 1 MW/100 s operation at 110 GHz, in the worst case, and it is marginal for the stable operation with the waveguides made of aluminum alloy. The heat loads on the waveguides have been evaluated as 23 kW/m2 for the worst case between miter bends, 12-23 kW/m2 within 4 m from miter bend and 4-12 kW/m2 for waveguide far from miter bends. The evaluated heat loads will be taken into account for the final design of the TL components and cooling for the JT-60SA ECH/CD system.

For successful tokamak operation with adequate mode selection of the electron cyclotron wave, launching wave polarization should be accurately controlled. In this study, a new method is proposed to efficiently identify the response of polarizers using a geometric approach in the Stokes space, focusing on the fact that polarization can be represented as a vector in Stokes space and the response of a polarizer can be described as a rotation. The proposed methods are intended (i) to determine the response parameters of a polarizer or (ii) to determine the response parameters of two polarizers simultaneously. A simple measurement system was prepared to observe the polarizers’ output polarization in the 110/138 GHz transmission line. The determined response parameters of two polarizers can reproduce measured polarizations with sufficient accuracy above 99 %. The direction of an output polarization circularity, the only feature of a polarization that could not be directly known from the prepared measurement, could also be determined with sufficient accuracy.

This paper presents the progress of performance tests of ITER gyrotrons developed at QST and the design of dual-frequency (170 GHz and 104 GHz) gyrotrons to enhance various operation scenarios in ITER, such as characteristics studies of H-mode/ELM at low magnetic fields. The major achievements in developing the ITER gyrotrons are as follows: (i) manufacturing of eight ITER gyrotrons and their auxiliary components has been completed. Performance tests at QST have been progressing and four of the eight gyrotrons achieved the required test criteria—1 MW/300 s/50%, 5 kHz modulation with > 0.8 MW. Excitation of LP01 mode having a purity of > 95% was also successfully demonstrated using a 50 mm-diameter waveguide transmission line, satisfying the specification. (ii) The design of dual-frequency gyrotrons capable of 1 MW continuous-wave operation, was successfully completed.

Based on the latest optical design of ITER ECH&CD equatorial launcher, the power absorption at the plasma breakdown is evaluated with considering reflections by the 3-dimensional first wall structure. The beam diffusion is simulated by a bunch of spreading rays and the reflections on the first wall is analyzed for each ray. The power absorption is evaluated by the optical thickness when the rays pass across the resonant surface. The frequency of EC wave is 170 GHz and the density of concern is from 2.5x10^15 m^-3. As a result, at least 2 MW is absorbed out of 6.7 MW injection from the Top row in the case of fundamental O-mode injection even at the breakdown. In the case of 2nd harmonic X-mode injection, the total absorbing power is 200 kW at the electron density of 10^18 m^-3 and the electron temperature of 5 eV, which is proportional to the electron density and the electron temperature. It is found that a certain injection angle should be excluded in order to prevent intense stray RF injection up to 4 MW propagating toward specific ports within a few reflections.

Installation of an accelerator-based boron neutron capture therapy (AB-BNCT) system was started in April 2014 at the Southern Tohoku BNCT Research Center (STBRC), and clinical trials began in January 2016. There are two treatment rooms, which have same specifications, and the beam quality equivalency was confirmed both rooms. Here, we describe the design and construction of the first hospital-based AB-BNCT facility in the world with multiple treatment rooms.

A cesiated DC negative ion source has been developed for proton cyclotrons in medical applications. A continuous H− beam of 23 mA was stably extracted at an arc power of 3 kW. The beam current gradually decreases with a constant arc power and without additional Cs injection and the decay rate was about 0.03 mA (0.14%) per hour. A feed-back control system that automatically adjusts the arc power to stabilize the beam current is able to keep the beam current constant at ±0.04 mA (±0.2%).

A filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In Cs-free operation, continuous H(-) beam of 10 mA and D(-) beam of 3.3 mA were obtained stably at an arc-discharge power of 3 kW and 2.4 kW, respectively. In Cs-seeded operation, H(-) beam current reached 22 mA at a lower arc power of 2.6 kW with less co-extracted electron current. The optimum gas flow rate, which gives the highest H(-) current, was 15 sccm in the Cs-free operation, while it decreased to 4 sccm in the Cs-seeded operation. The relationship between H(-) production and the design/operating parameters has been also investigated by a numerical study with KEIO-MARC code, which gives a reasonable explanation to the experimental results of the H(-) current dependence on the arc power.

Background and purpose To confirm the feasibility of accelerator-based BNCT (AB-BNCT) for treatment of multiple liver tumors and malignant pleural mesothelioma (MPM), we compared dose distribution and irradiation time between AB-BNCT and reactor-based BNCT (RB-BNCT). Material and methods We constructed treatment plans for AB-BNCT and RB-BNCT of four multiple liver tumors and six MPM. The neutron beam data on RB-BNCT were those from the research reactor at Kyoto University Research Reactor Institute (KURRI). The irradiation time and dose–volume histogram data were assessed for each BNCT system. Results In BNCT for multiple liver tumors, when the 5 Gy-Eq dose was delivered as the mean dose to the healthy liver tissues, the mean dose delivered to the liver tumors by AB-BNCT and RB-BNCT was 68.1 and 65.1 Gy-Eq, respectively. In BNCT for MPM, when the mean lung dose to the normal ipsilateral lung was 5 Gy-Eq, the mean dose delivered to the MPM tumor by AB-BNCT and RB-BNCT was 20.2 and 19.9 Gy-Eq, respectively. Dose distribution analysis revealed that AB-BNCT is superior to RB-BNCT for treatment of deep-seated tumors. Conclusions The feasibility of the AB-BNCT system constructed at our institute was confirmed from a clinical viewpoint in BNCT for multiple liver tumors and MPM.

We launched a new intervention study called REPRINTS in which senior volunteers engaged in reading picture books to children. Sixty-nine volunteers and 72 participants in a control group, all aged 60 years and over, living in three urban locations, participated in a baseline health checkup in June 2004. After completion of a three-month training seminar, volunteers visited public elementary schools and kindergartens in groups of 6 to 10 for an 18 month period. They were assessed again by a follow-up health checkup in March 2006. At the follow-up, social network scores (frequency of contact with grandchildren and others around the neighborhood) and self-rated health improved or was maintained at a significantly higher rate for the 37 individuals volunteering most intensively as compared to those who did not volunteer or volunteered minimally. In conclusion, through intensively being engaged in the intergenerational volunteer programs during 21 months, self-rated health and social networks were more likely ...

This Manuscript examines a conference to promote intergenerational programs and practices, which was held in Tokyo in the summer of 2006. We especially focus on: (a) some of the factors that promoted social networking activities for intergenerational unity among participants at the conference and (b) some of the ways in which the networking activities affected participants' satisfaction and motivation to be repeaters. Our findings are drawn from a review of participants' responses on a questionnaire that they filled out at the conclusion of the conference. In short, the conference a useful opportunity for those interested in social networking in intergenerational unity. It was found that successful networking experiences can serve to encourage participants to be repeaters of future conferences, which implies for contributing to more stability and unity in the emergent intergenerational movement.

Intergenerational practice is thriving in Japan. There are many accounts of innovative and dynamic intergenerational programs throughout the country, as exhibited by the programs illustrated in thi...

A multi-cusp DC H− ion source has been developed for cyclotrons in medical use. Beam optics of the H− ion beam is studied using a 2D beam trajectory code. The simulation results are compared with the experimental results obtained in the Mark I source, which has produced up to 16 mA H− ion beams. The optimum extraction voltages show good agreement between the calculation and the experimental results. A new ion source, Mark II source, is designed to achieve the next goal of producing an H− beam of 20 mA. The magnetic field configurations and the plasma electrode design are optimized for Cs-seeded operation. Primary electron trajectory simulation shows that primary electrons are confined well and the magnetic filter prevents the primary electrons from entering into the extraction region.

Japan's intergenerational movement is thriving, but it is difficult to capture the whole picture. Nevertheless, in this special issue of the Journal of Intergenerational Relationships (JIR) we atte...

Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation & treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutron collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8×109 neutrons/cm2/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with 10B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.

We have launched a new intervention study, called "REPRINTS" (Research of productivity by intergenerational sympathy), in which senior volunteers aged 60 years and over are engaged in reading picture books to school children, regularly visiting public elementary schools since 2004.So far, no repeated cross-sectional studies to demonstrate indirect effects on parents have been reported, although reciprocal effects on senior volunteers and children have been demonstrated. The purpose of this study was to examine the changes of evaluation of "REPRINTS" program by parents of school children during the 2 years.Four to six volunteers as a group visited an elementary school in a suburb of Kawasaki city twice a week to read picture books. A baseline survey was conducted one month after launching the volunteer activity. First to fourth follow-up surveys were conducted every 6 months after baseline surver. Of 368 parents, 230 whose children were in 1st-4th grade were analyzed.School grade of children, gender, emotional image scale of older adults by the SD (Semantic Differential) method (13 items), parents' evaluation of activity of "REPRINTS" volunteers such as promotion of reading for children, or children's respect for older adults, appreciation, familiarity with older adults, indirect effects on promotion of safety in the community, and reducing parent's physical and psychological burdens of volunteer service for school. Repeated cross-sectional analyses by ANCOVA, adjusted for confounding factors, were conducted in order to compare changes in responses between parents of 1st-2nd grade children (lower-grade children) with those of 3rd-4th grade-children (middle-grade children). We examined experiences of being read with picture books, greeting and having conversations with volunteers among all of 330 students of 1st-4th grade. These three items were examined using Chi-squared test to compare longitudinal change between parents of lower-grade and middle-grade children.Evaluation of children's familiarity with older adults significantly declined among parents of middle-grade children, but was maintained among those of lower-grade children during the 2 years. Physical burdens of volunteer service for school were lower among parents' of lower-grade children at baseline, and were significantly reduced among parents' of all grades. Promotion of reading for children, indirect effects on promotion of safety in the community, and frequency of hearing episodes of "REPRINTS" volunteers from children were higher among parents' of lower-grade children at baseline. Psychological burdens were reduced and level of knowledge of "REPRINTS" volunteers was increased among parents' of all grades. In terms of parents' emotional image scale of older adults in general, no significant difference was found among the grades of school children and number of surveys for all the subscales of 'socialization', 'activity', and 'cheerfulness'.The level of knowledge and a number of items of evaluation of "REPRINTS" volunteers were significantly increased among parents of both lower-grade and middle-grade children during the 2-year intervention. This study indicates that the "REPRINTS" program can contribute to establishing trust and reliance between generations of older adults and parents of school children with the children as mediators.

The feature and mechanism of flame acceleration and transition to detonation are not fully understood. In particular, the occurrence of “explosions in explosion” in the transition processes is very important phenomena which is worth studying carefully. The present study aims to observe this phenomena and to elucidate the transition processes by using the high-speed Schlieren photography.

We have been developed an epithermal neutron source for boron neutron capture therapy(BNCT), consisting of a cyclotron accelerator that can provide a ∼ 1 mA, 30 MeV proton beam, a neutron production beryllium target and the moderator that can reduce the energy of fast neutrons to an effective energy range. In order to validate the simulations, we measured the depth distribution of the thermal neutron flux in water phantom located at the treatment position. The measured results were compared with the simulations using the MCNPX Monte Carlo code. The good agreement between the simulations and measurements was shown. The thermal neutron flux with the proton current of 430 μA was 7.4 × 108 (neutrons cm−2 s−1) at the depth of around 20 mm in the water phantom. This intensity corresponds to the neutron source of Kyoto University Research Reactor (KUR), at which 275 clinical trials of BNCT have been performed. We experimentally confirmed that our cyclotron based neutron source can use for clinical trials of BNCT.

In order to generate epithermal neutrons for boron neutron capture therapy (BNCT), we proposed the method of filtering and moderating fast neutrons, which are emitted from the reaction between a beryllium target and 30 MeV protons accelerated by a cyclotron, using an optimum moderator system composed of iron, lead, aluminum, calcium fluoride, and enriched (6)LiF ceramic filter. At present, the epithermal-neutron source is under construction since June 2008 at Kyoto University Research Reactor Institute. This system consists of a cyclotron to supply a proton beam of about 1 mA at 30 MeV, a beam transport system, a beam scanner system for heat reduction on the beryllium target, a target cooling system, a beam shaping assembly, and an irradiation bed for patients. In this article, an overview of the cyclotron-based neutron source (CBNS) and the properties of the treatment neutron beam optimized by using the MCNPX Monte Carlo code are presented. The distribution of the RBE (relative biological effectiveness) dose in a phantom shows that, assuming a (10)B concentration of 13 ppm for normal tissue, this beam could be employed to treat a patient with an irradiation time less than 30 min and a dose less than 12.5 Gy-eq to normal tissue. The CBNS might be an alternative to the reactor-based neutron sources for BNCT treatments.

A multi-cusp DC H(-) ion source has been designed and fabricated for medical applications of cyclotrons. Optimization of the ion source is in progress, such as the improvement of the filament configuration, magnetic filter strength, extraction electrode's shape, configuration of electron suppression magnets, and plasma electrode material. A small quantity of Cs has been introduced into the ion source to enhance the negative ion beam current. The ion source produced 16 mA of DC H(-) ion beam with the Cs-seeded operation at a low arc discharge power of 2.8 kW.