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Conferring drought resistant traits to crops is one of the major aims of current breeding programs in response to global climate changes. We previously showed that exogenous application of acetic acid to roots of various plants could induce increased survivability under subsequent drought stress conditions, but details of the metabolism of exogenously applied acetic acid, and the nature of signals induced by its application, have not been unveiled. In this study, we show that rice rapidly induces jasmonate signaling upon application of acetic acid, resulting in physiological changes similar to those seen under drought. The major metabolite of the exogenously applied acetic acid in xylem sap was determined as glutamine—a common and abundant component of xylem sap—indicating that acetic acid is not the direct agent inducing the observed physiological responses in shoots. Expression of drought-responsive genes in shoot under subsequent drought conditions was attenuated by acetic acid treatment. These data suggest that acetic acid activates root-to-shoot jasmonate signals that partially overlap with those induced by drought, thereby conferring an acclimated state on shoots prior to subsequent drought.

Previous studies have revealed application of a magnetic field longitudinal to a carbon-ion beam enhances its biological effectiveness. This communication investigated how timing of the magnetic field application with respect to beam irradiation influenced this effect. Human cancer cells were exposed to carbon-ion beams with linear energy transfer (LET) of 12 and 50 keV/μm. The longitudinal magnetic field of 0.3 T was applied to the cells just before, during, or right after the beam irradiation. The effects of the timing on the biological effectiveness were evaluated by cell survival. The biological effectiveness increased only if the magnetic field was applied during beam irradiation for both LET beams.

A study of multiple-ion therapy with charged heavy-ion beams was performed to improve outcomes of refractory cancer treatments. We proposed the accelerator operation method for applying the multiple-ion therapy, to quickly switch the ion species and energies of the output beams. In this method, the irradiation ion species can be changed only by switching the selected ion source and the injector parameters, and the output beam energies can be varied without changing the magnetic operation patterns of the synchrotron. We verified the effectiveness of our approach by conducting experiments at the Heavy Ion Medical Accelerator in Chiba (HIMAC) and confirmed that the approach can provide the fast switching of both the ion species and the beam energies. The experimental results also demonstrated that our approach will greatly reduce the commissioning time and the routine adjustments for multiple-ion beams.

Purpose: Our previous study revealed that the application of a magnetic field longitudinal to a carbon-ion beam of 0.1 ≤ B//≤ 0.6 T enhances the biological effectiveness of the radiation. T...

Radiotherapy using high-energy carbon beams from the Heavy Ion Medical Accelerator in Chiba has been carried out at the National Institute of Radiological Sciences (NIRS) since June 1994, and more than 10 000 patients have been treated to date. With the prospective clinical results for the first ten years, we designed a compact accelerator facility for carbon-ion radiotherapy (CIRT), and performed related Research and Development (RD two of them have both horizontal and vertical fixed-irradiation-ports, and the other is a rotating-gantry port. For all ports, fast three-dimensional raster-scanning irradiation technology is employed. The rotating gantry equips ten combined-function superconducting magnets, and can deliver carbon ions having the energy of between E = 430 and 50 MeV/ u to an isocenter with irradiation angles of over ±180°. Construction as well as installation of the superconducting gantry was completed by the end of September 2015, and treatments using the gantry began since May 2015. Presently, we are further designing a next-generation compact facility as a future project; superconducting and laser technologies are to be used for accelerator design. In this paper, we report development of carbon-ion accelerator facilities as well as the future project.

Track-structure Monte Carlo simulations are useful tools to evaluate initial DNA damage induced by irradiation. In the previous study, we have developed a Gean4-DNA-based application to estimate the cell surviving fraction of V79 cells after irradiation, bridging the gap between the initial DNA damage and the DNA-rejoining kinetics by means of the two-lesion kinetics (TLK) model. However, since the DNA repair performance depends on cell line, the same model parameters cannot be used for the different cell lines. Thus, we extended the Geant4-DNA application with an updated TLK model for the evaluation of DNA damage repair performance in HSGc-C5 carcinoma cells which are typically used for evaluating proton/carbon radiation treatment effects. For this evaluation, we also performed experimental measurements for cell surviving fractions and DNA-rejoining kinetics of the HSGc-C5s cells. Concerning fast- and slow-DNA rejoining, the TLK model parameters were adequately optimized with the simulated initial DNA damage. Using the optimized TLK model, the Geant4-DNA simulation is now able to predict cell survival and DNA-rejoining kinetics for HSGc-C5s cells.

We here report the production of highly spherical protein nanoparticles based on the domain-swapping oligomerization of a circularly permuted trimeric protein, major histocompatibility complex (MHC) class II associated chaperonin. The size distribution of the nanoparticles can be adjusted to between 40 and 100 nm in diameter, and thus, these particles are suitable as drug carriers following purification under basic conditions. Our approach involves no harsh treatments and could provide an alternative approach for protein nanoparticle formation.

The National Institute of Radiological Sciences has investigated multiple-ion therapy using energetic beams of helium, carbon, oxygen, and neon ions, to improve treatment outcomes of refractory cancer. For this therapy, it is necessary to ensure the helium-ion beam purity to avoid irradiation by unwanted ions. Here, we develop a measurement method for monitoring beam purity. This method can measure the charge number of the ions in a high-purity beam using an ionization chamber and Faraday cup. In addition, it can be used to detect the contamination of the clinical helium-ion beam. We perform beam experiments to evaluate our beam-purity monitoring method and predict that our method is capable of detecting contamination below 1%.

Previously reported studies have revealed that the application of a magnetic field longitudinal to a carbon-ion beam enhances its biological effectiveness. Here we investigated how timing of the magnetic field application with respect to beam irradiation influenced this effect. Human cancer cells were exposed to carbon-ion beams with linear energy transfer (LET) of 12 and 50 keV/µm. The longitudinal magnetic field of 0.3 T was applied to the cells just before, during or immediately after the beam irradiation. The effects of the timing on the biological effectiveness were evaluated by cell survival. The biological effectiveness increased only if the magnetic field was applied during beam irradiation for both LETs.

In order to synthesize the Fe@C60 complex, iron ion beam irradiated to C60 thin films. The energy of the irradiated iron ions was controlled from 50 eV to 250 eV. The dose of that was controlled from 6.67 × 1012 to 6.67 × 1014 ions/cm2. By the analysis of the surface of the iron ion irradiated C60 thin films using laser desorption/ionization time-of-flight mass spectrometry, we could confirm the peak with mass/charge of 776. The mass/charge of 776 corresponds to Fe + C60. We obtained the maximum intensity of the peak with mass/charge of 776 under the irradiation iron ion energy and the dose were 50 eV and 3.30 × 1013 ions/cm2, respectively. Then, the separation of the material with mass of 776 was performed by using high performance liquid chromatography. We could separate the Fe + C60 from the iron ion irradiated C60 thin film. As a result, we could synthesize the Fe + C60 complex as a new material.

For systematic and genome-wide analyses of rice gene functions, we took advantage of the full-length cDNA overexpresser (FOX) gene-hunting system and generated >12 000 independent FOX-rice lines from >25 000 rice calli treated with the rice-FOX Agrobacterium library. We found two FOX-rice lines generating green calli on a callus-inducing medium containing 2,4-D, on which wild-type rice calli became ivory yellow. In both lines, OsGLK1 cDNA encoding a GARP transcription factor was ectopically overexpressed. Using rice expression-microarray and northern blot analyses, we found that a large number of nucleus-encoded genes involved in chloroplast functions were highly expressed and transcripts of plastid-encoded genes, psaA, psbA and rbcL, increased in the OsGLK1-FOX calli. Transmission electron microscopy showed the existence of differentiated chloroplasts with grana stacks in OsGLK1-FOX calli cells. However, in darkness, OsGLK1-FOX calli did not show a green color or develop grana stacks. Furthermore, we found developed chloroplasts in vascular bundle and bundle sheath cells of coleoptiles and leaves from OsGLK1-FOX seedlings. The OsGLK1-FOX calli exhibited high photosynthetic activity and were able to grow on sucrose-depleted media, indicating that developed chloroplasts in OsGLK1-FOX rice calli are functional and active. We also observed that the endogenous OsGLK1 mRNA level increased synchronously with the greening of wild-type calli after transfer to plantlet regeneration medium. These results strongly suggest that OsGLK1 regulates chloroplast development under the control of light and phytohormones, and that it is a key regulator of chloroplast development.

Downregulation of photosystem I (PSI) content is an essential process for cyanobacteria to grow under high-light (HL) conditions. In a pmgA (sll 968) mutant of Synechocystis sp. PCC 6803, the levels of PSI content, chlorophyll and transcripts of the psaAB genes encoding reaction-centre subunits of PSI could not be maintained low during HL incubation, although the causal relationship among these phenotypes remains unknown. In this study, we modulated the activity of psaAB transcription or that of chlorophyll synthesis to estimate their contribution to the regulation of PSI content under HL conditions. Analysis of the psaAB-OX strain, in which the psaAB genes were overexpressed under HL conditions, revealed that the amount of psaAB transcript could not affect PSI content by itself. Suppression of chlorophyll synthesis by an inhibitor, laevulinic acid, in the pmgA mutant revealed that chlorophyll availability could be a determinant of PSI content under HL. It was also suggested that chlorophyll content under HL conditions is mainly regulated at the level of 5-aminolaevulinic acid synthesis. We conclude that, upon the shift to HL conditions, activities of psaAB transcription and of 5-aminolaevulinic acid synthesis are strictly downregulated by regulatory mechanism(s) independent of PmgA during the first 6 h, and then a PmgA-mediated regulatory mechanism becomes active after 6 h onward of HL incubation to maintain these activities at a low level., This is a pre-copy-editing, author-produced PDF of an article accepted for publication in MICROBIOLOGY-SGM following peer review. The definitive publisher-authenticated version American Society for Microbiology, MICROBIOLOGY-SGM 155 (2009), 989-996; DOI 10.1099/mic.0.024018-0 online at: http://mic.sgmjournals.org/cgi/content/abstract/155/3/989

Heavy-ion therapy is one of the important methods for the cancer treatment. More than 3400 patients were treated between 1994 and 2007 at Heavy Ion Medical Accelerator in Chiba (HIMAC). For the promotion of carbon-ion therapy, a compact carbon-therapy facility was developed. The size of the new facility is three times smaller, while the accelerator can supply the beams similar to those used at HIMAC. The new irradiation system was developed in order to obtain a precise dose distribution for moving and/or deforming organs.

A compact injector for a heavy-ion medical-accelerator complex was developed. It consists of an electron-cyclotron-resonance ion-source (ECRIS) and two linacs, which are a radio-frequency-quadrupole (RFQ) linac and an Interdigital H-mode drift-tube-linac (IH-DTL). Beam acceleration tests of the compact injector were performed, and the designed beam quality was verified by the measured results, as reported earlier. Because the method of alternating-phase-focusing (APF) was used for beam focusing of the IH-DTL, the motion of beam ions would be sensitive to gap-voltage errors, caused during tuning of the gap-voltage distribution and by automatic-frequency tuning in actual operation. To study the effects of voltage errors to beam quality, further measurements were performed during acceleration tests. In this report, the effects of voltage errors for the APF IH-DTL are discussed.

The plasma potential and its distribution play an important role in the highly-charged ion production and it is an important parameter of the electron cyclotron resonance (ECR) plasma. Emitting probes have been successfully used to determine plasma potential distributions in many plasma machines. In the framework of the ATOMKI–ECRIS plasma diagnostics research project, plasma-induced emitting probe was developed. It was proved that in certain conditions such probes could be reliably used without being damaged and without disturbing the plasma. Important observations were made related to the biased-disc effect. In favor of establishing the method of emitting probe usage in ECR plasma, dedicated experiments were performed at the NIRS–Kei2 all permanent compact ECR ion source. Based on the experiences gained after the NIRS experiments, the ATOMKI plasma-induced probe measurements could be interpreted. It was shown that biasing the Disc electrode negatively with respect to the source potential, the plasma potential measured on the resonant zone decreased, while the well-known ion beam current increase was obtained. This result proves the previous assumption [K.E. Stiebing, O. Hohn, S. Runkel, L. Schmidt, H. Schmidt-Bocking, V. Mironov, G. Shirkov, Phys. Rev. ST Accel. Beams 2 (1999) 123501], that the biased-disc changes the plasma potential distribution creating favorable conditions for ion beam extraction.

We report on the modification of fullerenes with iron and chlorine using two individually controllable plasmas in the Bio-Nano electron cyclotron resonance ion source (ECRIS). One of the plasmas is composed of fullerene and the other one is composed of iron and chlorine. The online ion beam analysis allows one to investigate the rate of the vapor-phase collisional modification process in the ECRIS, while the offline analyses (e.g., liquid chromatography-mass spectrometry) of the materials deposited on the plasma chamber can give information on the surface-type process. Both analytical methods show the presence of modified fullerenes such as fullerene-chlorine, fullerene-iron, and fullerene-chlorine-iron.

A compact injector, designed for a heavy-ion medical accelerator complex, was constructed. It consists of an Electron-Cyclotron-Resonance Ion-Source (ECRIS) and two linacs, which are a Radio-Frequency-Quadrupole linac and an Interdigital H-mode Drift-Tube-Linac (IH-DTL) having the same operating frequency of 200 MHz. For beam focusing of the IH-DTL, the method of Alternating-Phase-Focusing (APF) was employed. The compact injector can accelerate heavy ions having a charge-to-mass ratio of q m = 1 3 up to 4.0 MeV / u . Use of the APF IH-DTL and operating frequency of 200 MHz allowed us to design compact linacs; the total length of the two linacs is less than 6 m. Beam-acceleration tests of the compact injector system were performed. The measured intensity of accelerated C 4 + 12 beams with the compact injector was 380 e μ A . Beam transmission of the APF IH-DTL was estimated to be as high as 96%, which is comparable to the value calculated by a simulation code. Transverse phase-space and energy distributions of accelerated beams were measured and compared with those calculated by the simulation code, and we found that they were agreed well with each other.

A compact Drift-Tube-Linac (DTL) using an Interdigital H-mode (IH) cavity was designed for an injector of medical accelerators. For beam focusing, the method of Alternating-Phase-Focusing (APF) was applied. The APF IH-DTL can accelerate heavy ions having a charge-to-mass ratio of q / m = 1 3 up to 4.0 MeV / u . Having optimized an array of synchronous phases for cells, namely arranging drift tubes and gaps appropriately, both longitudinal and transverse focusing strengths were produced just with the rf acceleration field, and therefore no focusing element or cooling equipments had to be installed in the cavity. This allowed us to employ a rather high operating frequency, and hence to design a compact and cost-effective cavity. A further advantage of the APF linac can be found in its operation. Since the parameters to be adjusted are just the level and phase of the input rf, beam tuning can be made with ease. Consequently, the APF linac is suitable for an injector for medical accelerators. Tuning methods of the gap voltages and cavity frequency as well as the design of the cavity for APF IH-DTL have been developed. After constructing the cavity, measurements of the electric field and tuning of the gap voltages were performed. Finally, the rf power was fed into the cavity. In this paper, the design and results of the measurements are described.

Since 1994, the clinical trial for cancer therapy with HIMAC has successfully progressed, and more than 2100 cancer patients have been treated with a carbon beam. Based on the development of the accelerator and irradiation technologies for 10 years, we have designed a new carbon-therapy facility for widespread use in Japan, and key technologies for the new facility have been developed. We describe the conceptual design of the new facility and the status of development for the key technologies.

A rotating gantry has been a popular tool for a radiation cancer therapy. However, the heavy-ion gantry is huge and expensive, because of the higher magnetic rigidity than that of a proton beam. As one of the downsizing methods, the field strength of a wobbling magnet for a uniform lateral-dose distribution should be increased. Since the field strength of the conventional wobbler is limited by an eddy-current effect under an operation frequency of around 50 Hz, we propose a new wobbling technique by rotating a pair of permanent magnets with a high magnetic field of around 2 T. For carbon-ion therapy, the proposed technique reduces the irradiation-port length considerably to around 2 m from more than 6 m in the conventional-gantry design.

The time structure of extracted beams has been improved in synchrotron rings with resonant slow-extraction including RF-knockout extraction. In order to control the global spill structure in the RF-knockout slow-extraction method, it is necessary to improve the amplitude modulation (AM) function of the transverse RF-field. For this purpose, a scheme with a simple model of the extraction process has been proposed. Using this simple model, an analysis was carried out for determining the parameter relevant to the diffusion process in the separatrix. With this parameter, the new AM function obtained by the analytical approach could provide a flat spill within ±23% in both a simulation and an experiment at the HIMAC synchrotron. Cooperating with the feedback system, the global spill structure was significantly suppressed to be less than ±5%.

A resonant slow-extraction method from synchrotron rings has been successfully developed in order to deliver a beam for a period of over several seconds. In the resonant slow-extraction method, an optimization of the parameters is necessary in order to keep the beam size and position constant during the extraction for sufficient use of the extracted beam. For this purpose, a simple method to measure the outgoing separatrix was proposed and verified at the HIMAC synchrotron. In this method, two tantalum rods each with diameter of 1 mm are used as internal probes located near the extraction channel. By observing the extracted beam under the rods inserted into the ring, the outgoing separatrix can be measured. This technique will significantly contribute to the operation of a synchrotron employing resonant slow-extraction.

An irradiation method for spot scanning has been developed in order to provide accurate irradiation even for an irregular target shape. In spot scanning irradiation, the beam is turned off while the beam position is shifted to the next spot for precise dose management. Recently, the fast beam cut-off method, which can achieve a cut-off time of around 50 μs, was proposed and verified at the Heavy Ion Medical Accelerator in Chiba synchrotron. In order to utilize such a speciality of the technique for spot scanning, the characteristics of fast beam switching were investigated while turning on/off both the transverse and longitudinal RF fields many times during a single flattop. As a result, it was verified that this technique provides more than 50 spots during a single flattop in the synchrotron operation pattern with a cut-off time of 50 μs. With an increase in a switching number, the momentum spread and the size of the extracted beam increase within the allowable range for practical usage.

We measured the charge fraction of 6.0 MeV/n heavy ions (C, Ne, Si, Ar, Fe and Cu) with a carbon foil at the NIRS-HIMAC injector. At this energy they are stripped with a carbon foil before being injected into two synchrotron rings with a maximum energy of 800 MeV/n. In order to find the foil thickness (DE) at which an equilibrium charge state distribution occurs, and to study the dependence of the DE-values on the projectile atomic number, we measured the exit charge fractions for foil thicknesses of between 10 and 350 μg/cm2. The results showed that the DE-values are 21.5, 62.0, 162, 346, 121, 143 μg/cm2 for C, Ne, Si, Ar, Fe, Cu, respectively. The fraction of Ar18+ ions was actually improved to 33% at 320 μg/cm2 from ∼15% at 100 μg/cm2. For Fe and Cu ions, the DE-values were found to be only 121 and 143 μg/cm2; there is a large gap between Ar and Fe, which is related to the differences in the ratio of the binding energy of the K-shell electrons to an electron energy (3.26 keV) corresponding to the velocity of a 6.0 MeV/n projectile. The well-known “two disjoint Gaussians (shell effect)” was also observed in the measured charge fractions of both Fe and Cu. The results of the charge fractions were also compared with other data and to calculations of Rozet et al. [2] , in which there was a good agreement for light ions (C); however, a significant difference was observed for ion species heavier than Ne.

Cyanobacteria, algae and plants reduce photosystem contents and modulate photosystem stoichiometry upon acclimation to high-light (HL) conditions to avoid the damage due to excess light energy. In order to elucidate the molecular mechanism of HL acclimation, mRNA levels of genes encoding subunits of photosystems were examined upon the change of photon flux density in the wild-type strain of Synechocystis sp. PCC 6803. Transcript levels and promoter activities of photosystem I (PSI) genes rapidly decreased upon the shift to HL to less than 10% of the initial level within 1 h, whereas responses of photosystem II (PSII) transcript levels were not coordinated. The prompt change of promoter activities of PSI genes, but not PSII genes, seems important for Synechocystis cells to regulate their photosystem contents in response to changes in photon flux density. mRNA stabilities of PSI genes also decreased during HL incubation. The down-regulation of PSI transcripts under HL did not depend on de novo protein synthesis, contrasting with the requirement of newly synthesized protein factor(s) for the accumulation of PSI transcripts under low light. When gene expression profiles were compared between wild-type cells and a pmgA-disrupted mutant that cannot modulate photosystem stoichiometry under HL, a large increase in the psaAB and psaA transcript levels was observed in the mutant under prolonged exposure to HL for 6 h. Repression of the promoter activity of the psaA gene by a pmgA-dependent mechanism was shown to be essential for the adjustment of photosystem stoichiometry under HL conditions., Copyright notice. c2003 Springer. All rights reserved. Publisher's version: http://www.springerlink.com/content/xuml42ertpu1945l/?p=7a361f357fc54d9aa1edc9acceef90f1&pi=10

Two advanced RF-knockout (RF-KO) slow-extraction methods have been developed at HIMAC in order to reduce the spill ripple for accurate heavy-ion cancer therapy: the dual frequency modulation (FM) method and the separated function method. As a result of simulations and experiments, it was verified that the spill ripple could be considerably reduced using these advanced methods, compared with the ordinary RF-KO method. The dual FM method and the separated function method bring about a low spill ripple within standard deviations of around 25% and of 15% during beam extraction within around 2 s, respectively, which are in good agreement with the simulation results.

The yields of highly charged ions have been improved by using a gas-pulsing technique in the pulsed Penning-ionized-gauge ion source (PIGIS) in the heavy-ion medical accelerator in Chiba. So far, this pulsed PIGIS has been operated under a low-duty factor (10−2–10−3), in which the gas flow is not being pulsed. A solenoid-type gas valve, having a simple structure compared to the piezo-electric type, was attached to the outside of the PIGIS chamber in order to control the gas flow into the PIGIS chimney. Beam tests for Ne with gas pulsing showed that the pressure response time should actually be a few tens ms, and the intensity of Ne6+ was increased by ten times, from 20 to 200 eμA. The gas pulsing also improved the average vacuum in the low energy beam transport (LEBT) line by a factor of 4. When producing H2+, H3+, and He1+ by PIGIS with gas pulsing, the beam loss of highly charged ions from electron cyclotron resonance ion sources in the LEBT was reduced to be negligible; meanwhile, it was around 30% wit...

An electron cyclotron resonance ion source (ECRIS) is used to generate multicharged ions for many kinds of the fields. We have developed an evaporator by using induction heating method that can generate pure vapor from solid state materials in ECRIS. We develop the new matching and protecting circuit by which we can precisely control the temperature of the induction heating evaporator. We can control the temperature within ±15 °C around 1400 °C under the operation pressure about 10(-4) Pa. We are able to use this evaporator for experiment of synthesizing process to need pure vapor under enough low pressure, e.g., experiment of generation of endohedral Fe-fullerene at the ECRIS.

In order to realize new investigations on physics, biology, and other fields, a metallic ion beam is quite effective and essential. To produce the metallic ion beam in an electron cyclotron resonance (ECR) ion source, how to supply the metallic gas into the ECR plasma is most important. At present, the NIRS-HEC, which is an 18 GHz ECR ion source installed for the Heavy Ion Medical Accelerator in Chiba at the National Institute of Radiological Sciences (NIRS), enables us to produce a stable Fe9+ beam of 180 eμA by the metal ions from volatile compounds technique. In addition, the development of a new gas supply method, using the electron-bombardment technique, is in progress. In this method, the tip of a metal target rod (2–6 mm diameter) at a high positive potential is melted by bombarding the thermoelectrons emitted from a surrounding hot filament and the evaporated gas is supplied into the ECR plasma.

A compact electron cyclotron resonance ion source has been developed for heavy-ion medical facilities. The beam intensity and stability were considerably improved by recent modifications on three points (length of sextupole, cooling system for the extraction electrode, and position of the Einzel lens). Initial results of C4+ beam tests show that an intensity of 180 eμA can be routinely obtained with simple tuning. The best record was 220 eμA for C4+, which meets the medical requirements. Throughout these tests, CH4 gas was used with 0.1 cc/min and the extraction voltage was fixed at 25 kV. Results on beam emittance and long-term stability are also briefly discussed.

We recently reported on the first observation of ion-pumping phenomenon in a low-duty pulsed Penning source at the heavy-ion medical accelerator (HIMAC) in Chiba and its effectiveness to produce multiply charged ions [Y. Sato et al., Nucl. Instrum Methods Phys. Res. A 450, 231 (2000)]. In the Penning-ionized gauge ion source (PIGIS) of the HIMAC, the gas flow is not being pulsed, but there is a transient pressure response in the source when the arc is pulsed that permits the production of high-charge-state ions under a reasonably low gas pressure obtained by ion pumping. The best record for Ar8+ is 700 eμA in a peak under a constant gas flow of 0.2 cc/min, an extraction voltage of 24 kV, and a pulsed arc power of 1 kV and 5 A with a duty factor of 0.5% (25 W on average). This yield is higher than those of cw PIGISs by a factor of 100–1000 having a similar design and power (peak). This article gives a brief review for the mechanism and effects of ion pumping in a pulsed PIGIS.

Experimental results on an 18 GHz electron cyclotron resonance (ECR) ion source (NIRS-HEC) and a 10 GHz ECR ion source (NIRS-ECR) at National Institute of Radiological Sciences (NIRS) show that an extracted beam intensity strongly depends on the radial magnetic field distribution generated by a permanent sextupole magnet. In order to understand these results, we simulated beam extraction under strong influences of space charge. In the simulation, a current intensity at a different position of an extraction slit is assumed to be roughly proportional to a corresponding transverse area of the ECR zone under the assumption that ions are extracted along a longitudinal magnetic flux line. The calculations show that an optimum value of the sextupole magnetic field strength may exist for a given extraction configuration and beam intensity. Based on the simulation, beam intensity measurements have been performed with six sextupole magnets having different magnetic field strengths for two ion sources, and the experimental results are consistent with the calculations.

Heavy ion radiotherapy awakens worldwide interest recently. The clinical results obtained by the Heavy Ion Medical Accelerator in Chiba at the National Institute of Radiological Sciences in Japan have clearly demonstrated the advantages of carbon ion radiotherapy. Presently, there are four facilities for heavy ion radiotherapy in operation, and several new facilities are under construction or being planned. The most common requests for ion sources are a long lifetime and good stability and reproducibility. Sufficient intensity has been achieved by electron cyclotron resonance ion sources at the present facilities.

Since 1994 at the National Institute of Radiological Sciences HIMAC, the NIRS Penning ionized-gauge ion source (PIGIS) has so far been used for radiotherapy with carbon beams and for basic research with several ion species. The source can produce beams from H2 to Fe with a charge-to-mass ratio of between 1/7 and 1/2. It is a hot-cathode type with a filament, of which the lifetime is on the order of a week and the cathode on the order of 1 month, under a low-duty pulsed operation (⩽0.5%) synchronized to the ring operation. This PIGIS can produce highly charged ions: for example, 1 e mA of Ar7+ or 500 eμ A of Si5+ ions (by sputtering) under the typical arc power of 5 kW in peak. This article describes the present status of the NIRS-PIGIS.

We have researched a compact medical accelerator with low investment and running cost for the popularization of heavy ion cancer therapy. As the first step, the compact injector system has been investigated for a Heavy Ion Medical Accelerator in Chiba at National Institute of Radiological Sciences. The proposed new injector system consists of a 6 MeV/u interdigital H-mode (IH) linac of 3.1 m long and a 18 GHz superconducting electron cyclotron resonance (ECR) (SC–ECR) ion source. The IH linac with high power efficiency is appropriate to a medical and industrial injector system. Its beam trajectory was simulated and a prototype has been constructed. The SC–ECR ion source has been designed to realize lightweight and low power consumption and the mirror field distribution was estimated.

Carbon–ion cancer treatment is successfully being made at the Heavy Ion Medical Accelerator in Chiba (HIMAC). Design philosophy for the ion sources for medical facilities are as follows: (1) sufficient beam intensity, a few hundred e μA; (2) long lifetime with good stability; (3) easy operation and easy maintenance; and (4) compactness. In order to develop such source for future heavy-ion facilities, we have tested compact electron cyclotron resonance (ECR) ion sources using permanent magnets both for axial and radial confinement of hot electrons. Since the yield of C2+ ion in the first developed source (2.45 GHz ECR) was 15 e μA and far below the medical requirement (∼150 e μA for the HIMAC), a new source has been proposed, having a frequency of 10 GHz. The extracted intensity of C4+ (and C2+) ions is expected to be higher than 200 e μA.

Since the narrowly concentrated ion-density distribution enhances the space charge effects, the extracted beam intensity is lower than case with a uniform distribution. In order to realize the uniform ion-density distribution at the extraction aperture for the higher beam intensity, the radial magnetic field given by the permanent sextupole magnet has been optimized. The ion-density distribution estimated by the TRAPCAD code depends on the magnetic trap configuration. The diameter of the electron cyclotron resonance (ECR) zone determined by the inner diameter of the sextupole magnet was enlarged, and consequently the density of the flux lines running through the ECR zone decreased at the extraction aperture. The ion-density distribution could become more uniform. The inner diameter of the sextupole magnet of an 18 GHz ECR ion source for the Heavy Ion Medical Accelerator in Chiba at the National Institute of Radiological Sciences was increased from 46 to 66 mm, so that the extracted intensities of Ar8+ and...

There is a desire that a carbon-ion radiotherapy facility will produce various ion species for fundamental research. Although the present Kei2-type ion sources are dedicated for the carbon-ion production, a future ion source is expected that could provide: (1) carbon-ion production for medical use, (2) various ions with a charge-to-mass ratio of 1/3 for the existing Linac injector, and (3) low cost for modification. A prototype compact electron cyclotron resonance (ECR) ion source, named Kei3, based on the Kei series has been developed to correspond to the Kei2 type and to produce these various ions at the National Institute of Radiological Sciences (NIRS). The Kei3 has an outer diameter of 280 mm and a length of 1120 mm. The magnetic field is formed by the same permanent magnet as Kei2. The movable extraction electrode has been installed in order to optimize the beam extraction with various current densities. The gas-injection side of the vacuum chamber has enough space for an oven system. We measured dependence of microwave frequency, extraction voltage, and puller position. Charge state distributions of helium, carbon, nitrogen, oxygen, and neon were also measured.

With about 1000-h of relativistic high-energy ion beams provided by Heavy Ion Medical Accelerator in Chiba, about 70 users are performing various biology experiments every year. A rich variety of ion species from hydrogen to xenon ions with a dose rate of several Gy/min is available. Carbon, iron, silicon, helium, neon, argon, hydrogen, and oxygen ions were utilized between 2012 and 2014. Presently, three electron cyclotron resonance ion sources (ECRISs) and one Penning ion source are available. Especially, the two frequency heating techniques have improved the performance of an 18 GHz ECRIS. The results have satisfied most requirements for life-science studies. In addition, this improved performance has realized a feasible solution for similar biology experiments with a hospital-specified accelerator complex.

A new electron cyclotron resonance ion source has been constructed at Oshima College with a 2.45 GHz magnetron microwave source and permanent magnets employed as the main components. In addition, a solid-state power amplifier with a frequency range of 2.5-6.0 GHz was installed to study two-frequency plasma heating. Three solenoid coils were set up for adjusting the axial magnetic fields. Argon plasma generation and ion beam production have been conducted during the first year of operation. Ion current densities in the ECR plasma were measured using a biased disk. For 2.45 and 4.65 GHz two-frequency plasma heating, the ion density was approximately 1.5 times higher than that of 2.45 GHz single-frequency heating.

Efficient production of multicharged ions has been investigated on the tandem-type ECRIS in Osaka University. According to the consideration of the accessibility conditions of microwaves to resonance and cutoff regions, it was suggested that the upper hybrid resonance (UHR) heating contributed to enhancement of ion beam intensity. In order to enhance multicharged ion beams efficiently, injecting higher frequency microwave with extraordinary (X-mode) toward UHR region has been tried. In this study, 2.45 GHz frequency microwaves are used for conventional ECR discharge, and 9.9 GHz frequency microwaves with X-mode are superimposed for UHR heating. The effects of additive microwave injection are investigated experimentally in terms of plasma parameters and electron energy distribution function (EEDF) measured by Langmuir probe and ion beam current. As the results show, it is confirmed that the electrons in the high energy region are affected by 9.9 GHz X-mode microwave injection from the detailed analysis of EEDF.

A new singly charged ion source using electron impact ionization has been developed to realize an isotope separation on-line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive (11)C ion beams. Low-energy electron beams are used in the electron impact ion source to produce singly charged ions. Ionization efficiency was calculated in order to decide the geometric parameters of the ion source and to determine the required electron emission current for obtaining high ionization efficiency. Based on these considerations, the singly charged ion source was designed and fabricated. In testing, the fabricated ion source was found to have favorable performance as a singly charged ion source.

A 2.45 GHz compact National Institute of Radiological Sciences electron cyclotron resonance (NIRS-ECR) ion source has been developed for heavy ion medical accelerator in Chiba at NIRS. A new ECR source is expected to produce C2+ ions of more than 160 eμA for the high-energy heavy-ion cancer treatment. An ECR-type ion source is adopted because of its excellent characteristics of long lifetime and easy operation. The compact ECR ion source is 15 cm in diameter, 20 cm in length, and about 20 kg in weight. A set of permanent magnets was adopted to generate both the axial mirror and the radial sextupole fields. Several gas materials, He, CO2, CH4, N2, and Ne, have been tested. The present performance for C2+ ions, however, is 15 eμA and far below the medical requirements. The estimated vacuum in the plasma chamber is around 5.0×10−5 Torr. A much better vacuum pressure is desired to produce C2+ ions of more than 100 eμA. The ECR plasma, however, cannot be kept stable under such a high vacuum pressure. As anothe...

A compact electron cyclotron resonance ion source with all permanent magnets has been developed for a new carbon therapy facility at NIRS. Initial tests with the Kei2 source have given a maximum intensity of 530𝑒𝜇A for C4+ at an extraction voltage of 40 kV and beam stability of better than 6% for 90 h at 280𝑒𝜇A at 30 kV. In these beam tests, there was continuously unwanted discharge around the puller at high-voltage extraction (above 40 kV). The start of discharge is caused by the short distance of 5 mm between the end of the plasma chamber and puller. At high-voltage extraction, this discharge will give rise to unwanted vapor from the copper puller. Then, the vacuum pressure in the extraction region will become worse. In order to suppress the discharge, the plasma chamber and puller were modified. Finally, a beam intensity of 380𝑒𝜇A was obtained with good stability at an extraction voltage of 30 kV. This article describes the modification of the puller for stable beam extraction, measurements of beam emittance, and improvement of C4+ intensity.

A compact 2.45 GHz ECR ion source has been developed at National Institute of Radiological Sciences (NIRS). The source was designed to provide doubly charged carbon ions, aiming at easy maintenance of the source. A set of permanent magnets was adopted to realize a minimum B structure. In pulse operation with a duty factor of 5%, the beam performance was measured with He, CO2, CH4, and N2 gases. With CO2 gas, analyzed beam currents are 160 and 15 eμA for C+ and C2+, respectively. Through the measurement of the microwave amplitude in the plasma chamber, it was found that the microwave power was not transmitted into the plasma chamber efficiently.