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Production of spin polarized short-lived nucleus 12N (I π = 1 + , T 1/2 = 11 ms) using heavy ion reactions at intermediate energies has been performed. Typical polarization of about −25 % and +10 % through the projectile fragmentation Be(14N, 12N)X and the charge exchange CH2(12C, 12N)X processes, respectively, was obtained. The present study proved that the combination of a 12C beam and a proton target provides a fairly good quality of polarized 12N beam in terms of intensity and energy uniformity, and is promising for materials science use of 12N as a nuclear probe.

We report our studies in various fields of Physics through nuclear moments utilizing the β-NMR technique, including material sciences, nuclear structures and fundamental symmetries. Especially, we focus on the recent progress in the studies on the electronic structure in Pt through Knight shifts of various impurities, lattice locations of impurities, electric field gradients, the analysis of nuclear spin in terms of its components, anomaly in the spin expectation value for 9C-9Li mirror pair, the G-parity conservation law, and the Ramsey resonance on UCN for future neutron EDM measurements.

SAGA HIMAT [1], the fourth carbon ion beam therapy facility in Japan, is located in Tosu city, Saga prefecture (Figures 1 and 2). The SAGA HIMAT Project is a collaborative work among the local governments, regional industries, and medical societies in the Kyushu area. The initial cost of this facility was approximately ¥15 billion, which was covered by donations, investments, and local government aid. The facility is managed by a nonprofit organization, SAGA HIMAT Foundation. At SAGA HIMAT [2], carbon ions are accelerated to up to 70% of light speed by 2 linear accelerators and a synchrotron. The accelerated ion beams are transported to treatment rooms A and B. The range of extracted energy is 140 to 400 MeV/u (Table 1). Room A has horizontal and 458 oblique beam lines; room B has horizontal and vertical beam lines. Broad beams are used and each outlet measures 15 cm3 15 cm (Figures 3 and 4). In preparation for treatment, radiation technologists create an immobilization device customized for each patient placed on a mock treatment couch. Dose compensation boluses adjusted to the shape of the irradiation fields are designed from the computed tomography (CT) simulation data and produced by outside manufacturers. We also have a regular CT scanner and magnetic resonance imaging for diagnosis. Treatment room C is now under construction for pencil beam scanning therapy. SAGA HIMAT is a stand-alone outpatient clinic specialized for carbon ion cancer therapy. The patients initially visit a cancer treatment facility of their choice, receive a diagnosis and staging of the cancer, and are referred to our institution for carbon ion

A fast three-dimensional scanning irradiation method is under development at the Heavy Ion Medical Accelerator in Chiba (HIMAC) as the next stage of heavy ion cancer therapy. This method requires highly accurate control of the beam size, energy, and intensity. To improve the accelerated beam’s quality, a new scheme for the synchrotron RF system has been developed. The new system adopts a periodic time clock system (T-clock) instead of an ordinary B-clock system. The new T-clock system is synchronized with a power line frequency of 50 Hz for synchronization with the synchrotron power supply. An ordinary B-clock system results in error pulses owing to the small analog signal of the magnetic field of the main dipole magnet, and the errors cause dipole oscillation of the beam in the RF bucket. Using the new T-clock generator at 192 kHz, we have observed an improvement in the acceleration efficiency and bunch shape compared to the B-clock generator.

A systematic investigation on the longitudinal and transverse momentum (P_L and P_T distributions of projectile-like fragments (PLFs) produced at intermediate energies has been performed experimentally. The momentum distributions of PLFs in a broad range of mass and charge, produced from 290 MeV/u Ar- and Kr-beams with various targets (C, Al, Nb, Tb and Au), were observed. The analysis of P_L distributions with an asymmetric Gaussian function provides the deceleration effect and the width of the distributions with good precision. A definite systematics is found in both the deceleration effect and the width. The broader width obtained at the low-momentum side indicates the contribution of multi-step processes at this energy. The target and energy dependencies of the induced momentum width are also shown. The analysis of P_T distributions with an off-centered Gaussian function provides not only the width, but also the orbital-deflection effect. In principle, the width is independent on the target, and is consistently reproduced based on the previously proposed formulation. In contrast, the deflection effect shows a strong target dependence. In the case of one-nucleon removed fragments, the main part of the deflection effect can be understood by the Coulomb repulsion. The systematics of the momentum distributions, shown in the present studies, is important for evaluating the production cross sections of PLFs. Especially, the P_T distribution is crucial to deduce production cross sections from the production rates of PLFs, which are observed at the forward angle within the limited angular acceptance.

We report recent situation of anomaly in spin expectation value found in 9 C- 9 Li mirror pair, recent analysis of the nuclear spin in terms of orbital or intrinsic and proton or neutron, and a result from the study of the G -parity conservation law through β -ray angular correlation in terms of its nuclear orientation.

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.

Based on more than 10 years of experience with HIMAC, we have proposed a new treatment facility for the further development of therapy with HIMAC. The new facility, as an extension of the existing one, has been designed and the related R&D work has been carried out. The following descriptions give a summary account of the design study and the related R&D work for this new treatment facility at HIMAC.

In order to deliver a high-quality beam for biophysics experiments, an electron cooler, a wideband rf system, and an extraction kicker have been installed in the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). A demonstration of beam manipulation during cooling and fast extraction is presented in this paper.

We have tested the timing properties of several thin plastic scintillators (10-500 mu m) designed for the Rare-RI Ring project at the R I beam factory. The experiments were performed at the heavy-ion synchrotron facility, HIMAC (Heavy Ion Medical Accelerator in Chiba), using a Xe beam with an energy of 200 MeV/nucleon. The scintillation light was read Out by fast-timing photomultipliers through standard fishtail-shaped light guides. The resultant timing resolutions reached a few tens of picoseconds, which satisfied our requirement for the project. We also measured charge-state distributions for Xe42+ and Fe20+ ions penetrating carbon foils of 10-500 mu g/cm(2) thickness. The results were compared with a theoretical model calculation for charge-state evolution. (c) 2008 Elsevier B.V. All rights reserved.

The electric quadrupole (Q) moment of short-lived nucleus 25Al \((I^{\pi} = 5/2^{+}, T_{1/2} = 7.18~{\rm s})\) has been measured for the first time, by means of the β-NQR technique. The spin polarization of 25Al was produced in heavy ion collisions and was kept in a α-Al2O3 single crystal for as long as 2 s and the quadrupole coupling frequency was obtained as ∣ eqQ / h(25Al in Al2O3) ∣ = (4.05 ±0.30) MHz. From the result, the Q moment was determined as ∣ Q(25Al)∣ = (240 ±20) mb. The present Q moment is larger by 30% than the shell model value of 184 mb, calculated by OXBASH code, which may show additional deformation of the nucleus.

The magnetic moment of 28p (Iπ =3+, T1/2 =270.3 ms) in the ground state has been measured by the β-nuclear magnetic resonance method for the first time. The measured magnetic moment of |μ(28P)|=0.309(9) μN is well reproduced by the shell model value of +0.306 μN. The shell model calculation also yields a proton density distribution with a long tail. The present results provide a strong confirmation of the configuration of the 2s1/2 proton which should lead to the proton halo.

The magnetic moment of short lived β-emitter 24mAl (426 keV, Iπ = 1 + , T1/2 = 131 ms) has been measured by means of β-NMR technique, for the first time. From the β-NMR spectrum, the magnetic moment was determined as \(\left| {\upmu}\left( ^{\rm 24m}{\rm Al} \right) \right|=\left( {2.99\pm 0.09} \right){\upmu}_{\rm N}\). Combined with the known magnetic moment of the mirror partner 24mNa, the expectation value of is obtained to be (0.08 ± 0.12). These values are reproduced well by the shell model calculation.

For the effective utilization of the favorable properties of heavy-ion beams in cancer treatment, it is important to evaluate the range of incident ions and the deposited dose distribution in a patient's body. For this purpose, the utilization of positron emitters induced in therapeutic irradiation is, at present, the only feasible method for in situ and non-invasive monitoring of heavy-ion therapy. In this study, we performed irradiation experiments with three species of ions to a water target, and the annihilation gamma-ray distributions were obtained with a positron camera. We applied the maximum likelihood estimation (MLE) method for the detected distributions to derive the range of incident ions and the deposited dose distribution in the target. As a result, the ranges were determined with a difference between the MLE range R MLE and the experimental range R exp less than 1.1 mm. The good agreement between the estimated dose distribution with the MLE method and the measured one implies that a deposited dose distribution in a target could be estimated from a detected annihilation gamma-ray distribution.

The spin-lattice relaxation times T1 for short-lived β emitters 25Al(I = 5/2, T1/2 = 7.2 s) and 28P(I = 3, T1/2 = 270 ms) in Pt were measured by means of the β-NMR technique. As a result, T1[25Al in Pt] = (1.1 \(^{+\ 0.7}_{-\ 0.3})\) s and T1[28P in Pt] >0.5 s were obtained at temperatures of 17 and 20 K, respectively. The Knight shifts were estimated from the Korringa relation, which were evaluated by comparing to the first principle calculations.

In proton therapy, it is important to evaluate the field irradiated with protons and the deposited dose distribution in a patient's body. Positron emitters generated through fragmentation reactions of target nuclei can be used for this purpose. By detecting the annihilation gamma rays from the positron emitters, the annihilation gamma ray distribution can be obtained which has information about the quantities essential to proton therapy. In this study, we performed irradiation experiments with mono-energetic proton beams of 160 MeV and the spread-out Bragg peak beams to three kinds of targets. The annihilation events were detected with a positron camera for 500 s after the irradiation and the annihilation gamma ray distributions were obtained. In order to evaluate the range and the position of distal and proximal edges of the SOBP, the maximum likelihood estimation (MLE) method was applied to the detected distributions. The evaluated values with the MLE method were compared with those estimated from the measured dose distributions. As a result, the ranges were determined with the difference between the MLE range and the experimental range less than 1.0 mm for all targets. For the SOBP beams, the positions of distal edges were determined with the difference less thanmore » 1.0 mm. On the other hand, the difference amounted to 7.9 mm for proximal edges.« less

Reaction cross sections of Li-8 on stable targets were measured at intermediate energies. With the existing experimental data of interaction cross sections at 790 MeV/nucleon the nucleon density distribution of Li-8 was extracted by the use of the modified Glauber model. Meanwhile, the existing data of B-8 have been also reanalyzed. Structures of Li-8 and B-8 were compared through the density. On the basis of dilute surface densities, the discussion of Li-7(n,gamma) Li-8 and Be-7(p,gamma) B-8 capture reactions was performed within the framework of the direct capture reaction mechanism. The calculations agreed quite well with the experimental data as well as other analyses.

A compact cavity for acceleration has been developed with cobalt-based amorphous cores, which is a part of research and development (RD at both sides of the gap there are quarter-wave coaxial resonators. The total length of the cavity is as short as 1.5 m and the inner diameter of the vacuum chamber is 190 mm. Considering the requirements for easy operation and maintenance, a transistor RF amplifier was used instead of the commonly used tetrode in the final stage. Each resonator has a maximum impedance of 400 Ω at 2 MHz, and a 1:9 impedance transformer has been attached to use a solid state amplifier of 50 Ω output impedance. In the frequency range from 0.4 to 8 MHz, an acceleration voltage of more than 4 kV can be obtained with a total input RF power of 8 kW. In this paper the structure of the cavity, the obtained core impedance, and their performances under high-power test are presented.

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.

Based on 10 years experience of carbon therapy at HIMAC, new facility project is in progress at NIRS. In this paper, the design of the synchrotron and its transport system dedicated for carbon therapy based on the machine study at HIMAC and the results of the studies are presented. © 2001 Elsevier Science. All rights reserved

To explore the potential of double irradiation source, radioactive 9 C-ion beam, in tumor therapy, a comparative study on the surviving effect of human salivary gland cells at different penetration depths between 9 C and 12 C-ion beams has been carried out. The 9 C-ion beam came out more efficient in cell killing at the depths around its Bragg peak than the 12 C beam, especially at the distal side of the Bragg peak. Compared to the 12 C beam, an increase in RBE by a factor of up to 2.13 has been observed at the depths distal to the Bragg peak of the 9 C beam. The 9 C beam showed an enhanced biological effect at the penetration depths around its Bragg peak, corresponding to the stopping region of the incident 9 C-ions and where the delayed low-energy particles were emitted. Further analysis revealed that cell lethality by the emitted particles from the stopping 9 C-ions is responsible for the excessive biological effect at the penetration depths around the Bragg peak of the 9 C beam.

We developed a cobalt-based amorphous core as a new magnetic-alloy (MA) core for a loaded radio frequency (RF) cavity. Because of its low-quality-factor, high-permeability property, the core is suitable for constructing an untuned broadband accelerating cavity. While FINEMET FT-3M has been widely used as the core material, the permeability of our newly developed amorphous core is found to be approximately twice that of FINEMET FT-3M. This amorphous core is thus an excellent candidate for achieving a high-impedance cavity with low power consumption. Several measurements were taken in order to understand its feasibility and stability. The actual large-size cores were then manufactured for the first time for accelerator use.

Heavy ion cancer therapy using energetic 12C ions has been carried out successfully at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. The method has advantages over traditional radiation therapy using an energetic photon beam in two respects: the dose concentration owing to the Bragg peak and high biological effects. The development of a cancer therapy using 11C ions is also currently underway at HIMAC, however, there remains the problem of beam attenuation due to nuclear fragmentation reactions in the body of the patient; this requires modification of the dose calculation for the therapy. To the best of our knowledge, no research on 11C-induced nuclear fragmentation reactions has yet been published. We propose a method of identifying the nuclear fragmentation reaction event induced by the carbon beams using a total-absorption-type target detector, that plays the role of a human phantom, and a system of plastic scintillation counters surrounding the phantom. We have carried out measurements for the carbon beams with the detector system. A portion of the beam energy is lost as escaping fragment particles from the phantom, leading to a decrease in beam intensity. We were able to successfully detect nuclear reaction events on an event-by-event basis

We performed an experimental study of charge identification of heavy ions from helium to carbon having energy of about 290 MeV/u using an emulsion chamber. Emulsion was desensitized by means of forced fading (refreshing) to expand a dynamic range of response to highly charged particles. For the track reconstruction and charge identification, the fully automated high speed emulsion read-out system, which was originally developed for identifying minimum ionizing particles, was used without any modification. Clear track by track charge identification up to Z=6 was demonstrated. The refreshing technique has proved to be a powerful technique to expand response of emulsion film to highly ionizing particles.

The electric quadrupole coupling constants eqQ/h of 8B (I π = 2+, T 1/2 = 769 ms) and 13B (I π = 3/2−, T 1/2 = 17.4 ms) in single crystal TiO2 have been precisely measured by the β-NQR technique. The ratios of these Q moments to Q(12B) were determined as |Q(8B)/Q(12B)| = 4.882(32) and |Q(13B)/Q(12B)| = 2.768(24).

For spot-scanning irradiation, we have developed a new control system in the experiments involving secondary beams of short half-lives. Fast beam switching and spot-by-spot dose monitoring were incorporated into this system. The control system can interface with various instruments, perform sequencing of measurements, control the motion of instruments and data acquisition. Synchronized communications with the period of beam spills in the LAN are introduced in the system to avoid the conflicts among computer communications. As an example of measurement, the results of dose distribution in 3D spot-scanning irradiation are presented.

Purpose: To evaluate the potential importance of radioactive 9 C-ion beam in cancer radiotherapy. Methods and Materials: Human salivary gland (HSG) cells were exposed to a double-radiation-source 9 C beam at different depths around the Bragg peak. Cell survival fraction was determined by standard clonogenic assay. For comparison, the same experiment was conducted for a therapeutic 12 C beam. To determine relative biologic effectiveness (RBE) values, HSG cells were also irradiated with 60 Co γ-rays of fractionation scheme as the reference. Results: The 9 C beam was more efficient in cell killing at the depths around its Bragg peak than was the 12 C beam, which corresponded to the 9 C-ion stopping region and where delayed low-energy particles were emitted. The RBE value at 50% survival level for the 9 C beam varied from 1.38 to 4.23. Compared with the 12 C beam, the RBE values for the 9 C beam were always higher; an increase in RBE by a factor of up to 1.87 has been observed at the depths distal to the Bragg peak. Conclusion: The potential advantage of radioactive 9 C-ion beam in cancer therapy has been revealed at low dose rate in comparison with a therapeutic 12 C beam. This observation, however, remains to be investigated at therapeutic dose rates in the future.

The momentum dependences of the nuclear spin polarization P and alignment A of 13B(I π = 3/2+, T 1/2 = 17.36 ms) produced in the 100A MeV 15N + Be collisions have been measured by detecting β-ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some relaxation mechanisms must be take into account. Comparing the signs of the observed alignment of 12B, the sign of the quadrupole coupling constant eqQ of 13B in TiO2 was determined to be positive.

The electric quadrupole coupling constants eqQ/h of 20Na (Iπ = 2+, T 1/2 = 449.7 ms), 21Na (Iπ = 3/2, T 1/2 = 22.49 s) and 25Na (Iπ = 5/2, T 1/2 = 59.6 s) in single crystal ZnO and TiO2 were precisely measured by applying the β-NMR technique. The ratio of the quadrupole moments between 20Na (25Na) and 21Na was determined to be 0.728 ± 0.023 (0.011 ± 0.002).

A magnetic alloy (MA)-loaded cavity has been installed in Heavy Ion Medical Accelerator in Chiba (HIMAC). A beam study with a new Direct Digital Synthesis (DDS) system has been performed. The DDS system can generate multi-harmonic RF that includes up to 3 different RF frequencies. The multi-harmonic RF is amplified by a solid state and final amplifiers. These harmonic frequencies are in the band width of the MA RF system. Beam acceleration was performed by the system, and the acceleration efficiency was improved by both dual and triple harmonic RF.

This article gives a new experimental estimate of the fraction of 11 C nuclear absorption in plastic scintillator, (C 9 H 10 ) n , according to nuclear reactions, and compares the results with an empirical formula based on a microscopic nuclear reaction model by Kox et al. [Phys. Rev. C 35 (1987) 1678]. The result establishes that the model is applicable to 11 C.

The emitted particles from a β -delayed particle decay beam must enhance biological effects in the region of interest and such a radioactive ion beam may be useful in cancer treatment. To test this therapeutic purpose of β -delayed particle decay beams, 9 C beams were produced in the secondary beam line at HIMAC for the first time. The thickness of production target and degrader to yield a 9 C beam with higher production rate and purity was optimized and the momentum distribution of the produced 9 C beam under the optimal condition was measured. For upcoming radiobiological experiments, a uniform irradiation field for the produced 9 C beam was made by means of wobbling magnets.

Secondary beam courses have been constructed at HIMAC. There are two beam courses, SB1 and SB2, which were designed as branches from the PH2 (a primary beam course) at the same point. The SB1 course is used mainly for medical applications with a positron emitter beam, where an irradiation system was installed for this purpose. The SB2 course is expected for general experiments. In this paper, the current status of the secondary beam courses in HIMAC is presented.

The magnetic moment of 33 Cl ( I π = 3 / 2 + , T 1 / 2 = 2.51 s ) has been re-measured precisely by β -NMR method. The obtained magnetic moment | μ | = 0.7549 ( 3 ) μ N is consistent with the old value 0.7523 ( 16 ) μ N , but is 5 times more accurate. The value is well reproduced by the shell model calculation, μ S M = 0.70 μ N . Combined with the magnetic moment of the mirror partner 33 S, the nuclear matrix elements 〈 l p 〉 , 〈 l n 〉 , 〈 S p 〉 , and 〈 S n 〉 were derived.

To investigate the production mechanism of projectile-like fragments (PLFs) at intermediate energies, the momentum distributions of PLFs produced in reactions at E / A = 95, 290, and 430MeV were measured at RIKEN and NIRS. A correlation and a systematics in the width of the transverse momentum distribution were derived from the results. The production cross sections derived from the observed momentum distributions show the target and the incident energy dependences.

The nuclear moments of 13B(Iπ = 3/2−, T1/2 = 17.36ms) have been re-measured precisely in order to establish the spin manipulation technique for the study of the alignment correlation term in mass system A = 13. From the β-NMR on 13B in Pt, the magnetic moment was determined as |μ(13B)| = 3.1778(5)μN. From the β-NQR on 13B in TiO2, the Q moment has been determined as |Q(13B)| = 36.6(8)mb. We have measured the alignment correlation term α_E for 13B β decay for the first time and obtained a preliminary result as α−(13B) = 0.15(12)%/MeV.

The momentum dependences of the nuclear spin polarization P and alignment A of 12 B ( I π = 1 + , T 1 / 2 = 20.20 ms) [ 13 B ( I π = 3 / 2 − , T 1 / 2 = 17.36 ms)] produced in 100 A MeV 13 C [ 15 N] + Be collisions have been measured by detecting the β -ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some depolarization mechanisms must be taken into account related with the collision process itself. Comparing the signs of the observed alignment of 12 B and 13 B, the sign of the quadrupole moment Q ( 13 B) was determined to be positive.

Owing to the potentially therapeutic enhancement of delayed particles in treating malignant diseases by radioactive 9C-ion beam, LET spectra at different penetration depths for a 9C beam with 5% momentum spread, produced in the secondary beam line (SBL) at HIMAC, were measured with a multi-wire parallel-plate proportional counter. To compare these LET spectra with those of a therapeutic 12C beam under similar conditions, the 12C beam was replaced with an 11C beam, yielded in the SBL as well and having almost the same range as that of the 9C beam. The LET spectra of the 9C beam and its counterpart, i.e. the 11C beam, at various depths were compared, especially around the Bragg peak regions. The results show that nearby the Bragg peak lower LET components decreased in the LET spectra of the 9C beam while extra components between the LET peak caused by the primary beam and the lower components due to the fragments could be observed. These additional contributions in the LET spectra could be attributed to parts of the emitted particles from the radioactive 9C ions with suitable conditions regarding the LET counter. Integrating these LET spectra in different manners, depth-dose and dose-averaged LET distributions were obtained for the 9C and 11C beams, forming the basic data sets for further studies. In general, the depth-dose distributions of the 9C and 11C beams are comparative, i.e. almost the same peak-to-plateau ratio. The ratio for the 9C beam, however, has room to increase due to the geometric structure limitation of the present detector. The dose-averaged LETs along the beam penetration are always lower for the 9C beam than for the 11C beam except at the falloff region beyond the Bragg peak. Applying the present depth-dose and dose-averaged LET data sets as well as the essential radiobiological parameters obtained with 12C beams previously for HSG cells, an estimate concerning the HSG cell surviving effects along the penetration of the 9C and 11C beams shows that lower survival fractions for the 9C beam at the distal part of the Bragg peak, corresponding to the stopping region of the incoming 9C ions, can be expected when the same entrance dose is given. It is still hard to appreciate the potential of 9C beams in cancer therapy based on the present LET spectrum measurement, but it provides a substantial basis for upcoming radiobiological experiments.

A fast stochastic cooling is an inevitable function for the pre-cooling of RI beam. A new pick-up structure is designed and tested with heavy ion beam of 200 MeV/u. The measured results of characteristics of pick-up were described. In addition, a beam simulator was developed for the off line measurement of pick-up characteristic. Results of measurement of new type pick-up electrode were presented with the beam simulator.

A new type of beam chopper has been developed and installed at HIMAC (Heavy Ion Medical Accelerator in Chiba) in NIRS (National Institute of Radiological Sciences). The chopper has only 11.6 cm length and has been set between the ion sources and the RFQ. It is similar to a beam transformer, and modulates the beam kinetic energy by 10%. The beam is successfully chopped because the RFQ has a rather small energy acceptance. A chopped beam was injected into the synchrotron and a beam study has been performed. A very short bunch was formed and accelerated to the top energy. The behavior of the short bunch shows that a dipole oscillation was excited because of an unexpected frequency error of the RF system. It was caused by noise in the B-clock (Gauss Clock) circuit. The dipole oscillation caused by the frequency error was significantly reduced and the acceleration efficiency was improved by replacing the B-clock module.

Due to the favorable characteristics of heavy-ion beams such as dose localization as well as high relative biological effectiveness, heavy-ion cancer therapy is attracting growing interests all over the world. The application of β-delayed particle decay beams like 9 C ions in cancer therapy is expected to further improve the treatment efficacy of the modality of heavy-ions. For the first time 9 C beams were produced in the secondary beam line (SBL) of the HIMAC facility with a primary 12 C beam of 430 MeV/n. The production conditions providing a 9 C beam with higher production rate and purity were optimized using different thick production targets and degraders. The results show setting the momentum acceptance to the full value of 5% the production rate is 9.07 × 10 −6 and the purity is 82.88% for the produced 9 C beam under the optimal condition. Because of the large momentum spread for a secondary beam, the momentum distribution of the produced 9 C beam at the optimal condition was measured. The momentum among the beam had a nearly Gaussian profile with a standard deviation of 26.1 MeV/c/n and the largest component of the momenta appeared around 838.9 MeV/c/n. In order to form a relatively large uniform irradiation field being appropriate to further biological experiments for the produced 9 C beam, the scanning magnets in the irradiation system of the SBL, operating in a wobbling mode, was used. A uniform irradiation field of 20 mm in diameter could be achieved with homogeneity of 93.8%. The work presented in this paper provides a substantial basis for the further studies with 9 C beams for the therapeutic purpose.

It is desirable to reduce range ambiguities in treatment planning for making full use of the major advantage of heavy-ion radiotherapy, that is, good dose localization. A range verification system using positron emitting beams has been developed to verify the ranges in patients directly. The performance of the system was evaluated in beam experiments to confirm the designed properties. It was shown that a 10C beam could be used as a probing beam for range verification when measuring beam properties. Parametric measurements indicated the beam size and the momentum acceptance and the target volume did not influence range verification significantly. It was found that the range could be measured within an analysis uncertainty of +/-0.3 mm under the condition of 2.7 x 10(5) particle irradiation, corresponding to a peak dose of 96 mGyE (gray-equivalent dose), in a 150 mm diameter spherical polymethyl methacrylate phantom which simulated a human head.

A positron camera, consisting of a pair of Anger-type scintillation detectors, has been developed to verify ranges by using positron emitter beams. Each detector head is equipped with a NaI(Tl) crystal (diameter: 600 mm , thickness: 30 mm ) for high detection efficiency. To get a low counting rate for this application, the electric circuit was designed for flexibility in measurement and analysis by software. The energy and position were calibrated for high measurement accuracy. A spatial resolution of 8.6 mm in FWHM within a ±50 mm region (field of view) and a linear response of a 0.3 mm standard deviation within a ±200 mm region were obtained. The camera was designed so as to measure the ranges within an accuracy of 1 mm under a dose limitation (about 100 mGyE ) to reduce the safety margin for the irradiation field, and it met the required characteristics.

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.

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 RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method.

The magnetic moment of the short-lived β emitter 35Ar ( I π =3/2 + , T 1/2 =1.77 s) has been remeasured by means of the combined technique of polarized nuclear beams and β-NMR. The obtained magnetic moment is 0.6322(2) μN. This value is consistent with the old data, but is one order of more magnitude precise. The value is well reproduced by the shell model calculation.

In cancer treatment with heavy ions, verification of the ion range in the patient's body is important. For this purpose, a positron emitter beam provides the possibility of range verification. To use the positron emitter beam, we have constructed a secondary beam course and its irradiation system. In this paper the constructed system is presented together with some results of beam experiments.