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| TU6PFP012 | Extra Dose Reduction by Optimizing RF-KO Slow-Extraction at HIMAC | 1318 |
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A 3D scanning method gated with patient's respiration has been developed for the HIMAC new treatment facility. In the scanning irradiation, the RF-KO slow-extraction method has been used, because of the quick response to beam on/off from the synchrotron. However, a small amount of beam remained just inside the separatrix is extracted just before turning on the transverse RF field, which brings the extra dose. We proposed to apply another transverse RF-frequency component matched with the betatron frequency of the particles in the vicinity of the stopband, in addition to the original transverse RF field for the RF-KO slow-extraction. Using the proposed method, the particles just inside the separatrix, which cause the extra dose, can be selectively extracted during the irradiation; as a result, the extra dose can also be reduced. The validity of this approach has been verified by the simulation and the measurement with the non-distractive 2D beam profile monitor. We will report the result of this approach. |
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| TH5PFP029 | Optical Measurement System of Laser-Cooled Mg Ion Beam | 3257 |
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Funding: This work is supported by Advanced Accelerator Development Project of MEXT and the Global COE program "The Next Generation of Physics, Spun from Universality and Emergence". Transverse laser cooling experiments of 24Mg+ beam have been carried out at S-LSR, which is a small ion storage and cooler ring. According to a simulation, it is expected that under such a condition as the difference of synchrotron and betatron tunes is near integer, synchro-betatron coupling occurs and transverse laser cooling will be achieved*. In order to confirm this situation, the horizontal beam size and momentum spread are measured optically with CCD camera and PAT (post acceleration tube), respectively**,***. CCD camera observes fluorescence from the beam at the laser cooling section. Typical measured horizontal beam size is 0.5mm (1 σ). In some condition, an increase of fluorescence strength is observed, which indicates the beam concentration to the center, where the beam and the laser can interact. PAT is utilized for measurement of a longitudinal beam velocity profile. By application of electric potential to the PAT, the beam velocity is slightly modified. Since only particles which have velocities in a certain region can interact with the laser, the time variation of the florescence during voltage sweep represents the longitudinal velocity profile of the beam. *H. Okamoto, Phys. Rev. E 50, 4982 (1994) |
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| TH5PFP030 | Recent Approach to Crystalline Beam with Laser-Cooling at Ion Storage Ring, S-LSR | 3260 |
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Funding: The present work was supported by Advanced Compact Accelerator Development program by MEXT of Japanese Government. Support from Global COE, The Next Generation of Physics, is also greatly appreciated. Creation of 3-dimensional crystalline beam by application of laser-cooling for a Mg ion beam with kinetic energy of 40 keV is a major research subject of the ion storage ring, S-LSR, at ICR, Kyoto University*. Based on the success of longitudinal laser cooling in 2007**, an approach to extend the effect of laser cooling to the transverse degree of freedom has been performed. An indication of heat transfer from the horizontal to longitudinal direction has been obtained by synchro-betatron coupling. By application of bunched beam laser cooling at the operation point around (2.07, 1.10), the momentum spread of the cooled ion beam has been observed to have a peak at a synchrotron tune around 0.07 and simultaneously transverse beam size seems to be reduced in this region. An increase of beam brightness in the horizontal profile has also been observed by measuring spontaneous emission of absorbed laser light. In the present paper, strategy to reach the final 3-dimensional crystalline state by application of 3-dimensional laser cooling by careful adjustment of coupling among 3 degrees of freedom is to be presented based upon the recent experimental results. *A. Noda, M. Ikegami, T. Shirai, New Journal of Physics, 8, 288-307(2006). |
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| TH5PFP031 | Laser Cooling Experiment with Resonant Coupling at S-LSR | 3263 |
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Funding: Work supported by Advanced Accelerator Development Project of MEXT, the Global COE program "The Next Generation of Physics, Spun from Universality and Emergence" and the Grant-in-Aid for JSPS Fellows. Laser cooling experiments have been carried out at Small Laser-equipped Storage Ring(S-LSR). In order to achieve transverse cooling, a resonant coupling method* is applied. In this method, the transverse temperature is cooled indirectly by synchro-betatron coupling, through an RF electric field at a straight section with a finite dispersion of 1.0 m. In this experiment, a Mg+ beam is cooled by a co-propagating laser with a wavelength of 280 nm under various values of tunes and several diffenence resonant conditions of a synchrotron and betatron tune. The momentum spread are measured by observing laser-induced fluorescence light by using a post acceleration tube. The transverse beam profiles are measured with a CCD camera. When the synchrotron tune and the horizontal betatron tune are 0.065 and 2.064, respectively, an enhancement of momentum spread is observed. In this resonant condition the momentum spread is increased from 1.5x10-4 to 3.0x10-3 at 3x107 stored particles. The effect of resonant coupling for transverse beam sizes is now under investigation. The tune dependence and time variation of the beam sizes by laser cooling is also a subject in the present experiments. *H. Okamoto, Phys. Rev. E 50, 4982 (1994) |
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| TH6REP001 | Development of Screen Beam-Profile-Monitor System for High-Energy Beam-Transport Line at the HIMAC | 3947 |
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The screen monitor system is an important tool for beam diagnostic of the high-energy-beam transport line at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). We have developed a very thin fluorescent film and high speed charge-coupled-device camera. Because the fluorescent film is very thin (ZnS:Ag 2mg/cm3), the beam is measured with semi-non-destructively. Consequently we can use more than two monitors at the same time and multiple locations. Moreover we employ a high-speed three-processer for image processing, the system can be applied for online monitoring and interlock system (100Hz). When the beam profile measured by this system is inevitably changed over the setting tolerance during therapeutic irradiation for the patient, the beam is immediately turned off. The design and measurement result by irradiation test are discussed. |
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| TH4GAI02 | Recent Progress on HIMAC for Carbon Therapy | 3137 |
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Based on more than ten years of experience of the carbon cancer therapy with HIMAC, we have proposed a new treatment facility for the further development of the therapy with HIMAC. This facility will consist of three treatment rooms: two rooms equipped with horizontal and vertical beam-delivery systems and one room with a rotating gantry. For the beam-delivery system of the new treatment facility, a 3D hybrid raster-scanning method with gated irradiation with patient’s respiration has been proposed. A R&D study has been carried out toward the practical use of the proposed method, although this method was verified by a simulation study. In the R&D study, we have improved the beam control of the size, the position and the time structure for the proposed scanning method with the irradiation gated with patient’s respiration. Further, owing to the intensity upgrade of the synchrotron, we can successfully extend the flattop duration, which can complete one fractional irradiation with one operation period and can increase the treatment efficiency of the gated irradiation. We will report the recent progress on HIMAC for carbon therapy. |