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Applying permanent magnet technology to beam focusing in klystrons can reduce power consumption and increase reliability. These features benefit a variety of applications especially for large facilities that use a large number of klystrons such as the International Linear Collider. The low magnetic field needed for the purpose allows us to use inexpensive ferrite magnets instead of rare earth magnets. In order to evaluate the feasibility of such a focusing system with ferrite magnets, a test model for 750 kW L-band klystron was constructed. As a result of the power test, we attained 94% of the output power compared to an electromagnet.

Compact H(+) ECR ion source using permanent magnets is under development. Switching the hydrogen gas flow in pulse operations can reduce the gas loads to vacuum evacuation systems. A specially designed piezo gas valve chops the gas flow quickly. A 6 GHz ECR ion source equipped with the piezo gas valve is tested. The gas flow was measured by a fast ion gauge and a few ms response time is obtained.

We have developed a prototype rotating-permanent magnet sextupole lens (named rot-PMSx) for more efficient experiments with neutron beams in time of flight (ToF) mode. This lens can modulate the focusing strength over range 1.5 × 10 4 T / m 2 ⩽ g ′ ⩽ 5.9 × 10 4 T / m 2 . Synchronization between the modulation and the beam pulse produces a focused beam without significant chromatic aberration. We anticipate that this lens could be utilized in focusing small angle neutron scattering (SANS) instruments for novel approach to high resolution SANS. We carried out experiments testing the principle of this lens at the very cold neutron (VCN) beamline (PF2) at Institut Laue-Langevin (ILL), France. The focused beam image size at the detector was kept constant at the same beam size as the source ( ≈ 3 mm ) over a wavelength range of 30 A ⩽ λ ⩽ 48 A in focal length of ≈ 1.14 m . The flux gain was about 12 relative to a beam without focusing, and the depth of focus was quite large. These results show the good performance of this lens and the system. Thereupon we have demonstrated the performance of this test bed for high resolution focusing of VCN-SANS for a well-studied softmatter sample; a deuterium oxide solution of Pluronic F127, an (PEO)100(PPO)65(PEO)100 tri-block copolymer in deuterium oxide. The results of the focusing experiment and the focusing VCN-SANS are presented.

Permanent magnets are superior to electromagnets in generating strong multipole magnetic fields. Their fields are sometimes stronger than those that can be generated by superconducting magnets with the same bore radius, when the number of poles are higher. Three fabricated multipoles including a quadrupole magnet for the ILC (International Linear Collider) final focus doublet, a quadrupole magnets as a spin filter for cold neutrons, and a sextupole magnet for neutron beam focusing are described.

Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ =40 A were focused by the PMSx at a focal length of about 0.5 m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure.

We have established a novel method which make electron scattering off short-lived radioactive nuclei come into being. This novel method was named SCRIT (Self-Confining RI ion Target). It was based on the well known "ion trapping" phenomenon in electron storage rings. Stable nucleus, 133 Cs , was used as target nucleus in the R&D experiment. The luminosity of interaction between stored electrons and Cs ions was about 1.02(0.06) × 1026 cm -2 s -1 at beam current around 80 mA. The angular distribution of elastically scattered electrons from trapped Cs ions was measured. And an online luminosity monitor was used to monitor the change of luminosity during the experiment.

We have succeeded to compress the energy spread of a laser-produced proton beam to 1.6% at FWHM by an RF electric field synchronous to the pulse laser. Protons generated by this laser originally had a continuous energy spectrum with no peaks. Radial focusing and defocusing effects caused by the transverse component of the RF field were also observed. Concerning these effects, we simulated the energy spectra from the calculated value of the electric field by POISSON; the simulation could almost reproduce the experimental results. By applying this beam as an injection beam of a synchrotron, a compact acceleration system for particle cancer therapy is expected to be realized.

A closed orbit is corrected for single-turn injection to perform laser cooling experiments of 40 keV 24 Mg + beam at the small laser-equipped storage ring (S-LSR). Closed orbit distortion (COD) corrections have been carried out using a downhill simplex method, and CODs of less than ± 0.5 mm have been achieved throughout the whole circumference. The injection orbit and the CODs are optimized to pass through the two aperture holes in the alignment targets located in the laser cooling section with an algorithm to maximize beam lifetime. The CODs at the aperture holes are reduced to be less than ± 0.2 mm , assuring an overlap between the laser and the 24 Mg + ion beam.

We have experimentally confirmed an improvement of Q-value by mitigating the skin effect in an RF coaxial cavity. This was achieved by putting an insulated conductor foil on the lengthwise portion of the inner conductor of the cavity with the foil's end region raised by additinal spacer. By properly selecting the geometry and material of the layers, the Q-value at the 150 MHz resonance of the cavity was improved by 10%. The data have shown good agreement with the 2-dimensional simulation results.

For the investigation of free radicals with regards to cancer radiotherapy by ions, short-bunch formation followed by fast extraction was applied to a 7 MeV proton beam at S-LSR after electron-beam cooling. Using phase rotation with an applied RF voltage of 800 V, a short-bunch with a duration of 3.1 ns at 2 σ was created for a beam intensity of 1.4×10 8 , and fast extracted by a kicker magnet. Short-bunch formation by bunched cooling with a minimum bunch length of 15.7 ns at 2 σ was also carried out with an extraction efficiency of almost 100%.

A short-pulse (~210 fs) high-power (~1 TW) laser was focused on a tape target 3 and 5 µm in thickness to a size of 11×15 µm2 with an intensity of 3×1017 W/cm2. Protons produced by this laser with an energy spread of 100% were found to be improved to create peaks in the energy distribution with a spread of ~7% by the application of the RF electric field with an amplitude of ±40 kV synchronous to the pulsed laser. This scheme combines the conventional RF acceleration technique with laser-produced protons for the first time. It is possible to be operated up to 10 Hz, and is found to have good reproducibility for every laser shot with the capability of adjusting the peak positions by control of the relative phase between the pulsed laser and the RF electric field.

A beam test for the feedback damping of a coherent instability at small-laser equipped storage ring (S-LSR) was carried out. The instability caused beam loss, which limited the stored beam current to be about 600 mA during beam stacking with electron cooling. A vertical feedback damping system (VFS) using an electro-static beam position monitor (ESBPM) and a vertical kicker was applied to suppress this beam instability. The VFS realized not only suppressing the vertical coherent instability, but also revealing the characteristics of the feedback damping.

A scheme of the real-time optimization of proton production by an intense short-pulse laser interacting with a foil target was developed using a time-of-flight measurement with a plastic scintillator. Owing to special treatments, the detection of protons using a scintillation counter has become possible under heavy backgrounds such as laser light itself, laser-generated hard X-ray, self-emission light, and electrons from the laser-produced plasma. With such a real-time measurement of protons, the energy spectrum of protons could be obtained shot by shot, and the experimental conditions for optimal proton production could be determined very efficiently.

In order to widely spread out particle beams utilized in cancer therapy, laser-produced ions are developed as the injection beam for an ion synchrotron dedicated for cancer therapy. Such a laser ion source is expected to contribute largely to the realization of compactness of the size and low cost of the cancer therapy accelerator. The energy spectrum of the laser-produced ions, however, has no peak, but their intensities decrease exponentially according to the increase of the energy. For the purpose of modifying such a situation, we have proposed a scheme to rotate the beam in the longitudinal phase space with the use of the RF electric field, which is phase-adjusted with the pulse laser. We aim for a reduction of the energy spread of ± 5% selected by an energy analyzer and slits to ±1% by such phase rotation. For this purpose, a quarter wavelength resonator with two gaps with the same resonant frequency as the source laser has already been fabricated, together with its RF power source. The above phase rotation system and its recent experimental realization are presented.

Design of quadrupole magnets for a compact ion accumulation and cooler ring, S-LSR, is presented. By requirements from lattice parameters and spatial boundaries for real installation in S-LSR, quadrupole magnets with relatively short magnetic length but wide horizontal aperture are needed. In this paper, we present results obtained from magnetic field calculations by 2D and 3D modelings, and describe the optimization of a pole face shape and fringing edge (chamfer cut design).

A new compact ion cooler ring (S-LSR) in Kyoto University has a circumference of 22.197 m and maximum magnetic rigidity of 1 T/m. One of the research subjects of S-LSR is a test bed to produce crystalline beams. Ring optics is designed to satisfy several required conditions for the beam ordering such as a small betatron phase advance and small magnetic error. We plan two cooling approaches. One is an electron beam cooling with 7 MeV proton beam from a linac. This target is 1-dimensional Coulomb strings. The beam-ordering simulation is carried out using the S-LSR parameters. The other is laser cooling with 35 keV Mg + beam from an ion source. The goal of the laser cooling experiment is to produce two-dimensional and three-dimensional crystals.

The design and the magnetic field measurement of the quadrupole magnet for the compact ion ring, S-LSR, are presented. Because the S-LSR is a compact ring accelerator, whose components take up most of the space in the arc sections. Therefore, we have to optimize the integrated field gradient in the quadrupole magnetic field taking account of the effect of the neighboring field clamp. Under these conditions plus requirements from accelerator parameters, the design of the S-LSR quadrupole magnet was optimized by means of 2D and 3D modeling calculations. A magnet field measurement by a Hall probe is carried out together with the field clamp and S-LSR bending magnet. Both results of the calculation and the measurement present the almost same result as that for the effect of the field clamp.

A pulse stretcher operation of KSR using slow electron beam extraction by the third-order resonance in combination with an RF knockout method has been accomplished. The extracted beam energy, number of extracted electrons in a single pulse, maximum duration and duty factor are 60 MeV, 1.4×108, 40 s and 90%, respectively. The beam spill can be controlled from 0.2 s to 40 s by adjusting of the power for RF knockout.

We report the first observation of indirect resonantly enhanced transverse laser cooling of a bunched, stored ion beam of 40 keV $^{24}\mathrm{Mg}^{+}$. The longitudinal velocity distribution and the horizontal beam size of the laser-cooled $^{24}\mathrm{Mg}^{+}$ ion beam with 280 nm laser light were simultaneously observed by the use of standard fluorescence-based techniques. Keeping the operation point at (2.068, 1.105), the synchrotron tune (${\ensuremath{\nu}}_{s}$) was changed from 0.0376 to 0.1299. A strong decrease in the cooled horizontal beam size and a corresponding increase in the equilibrium cooled momentum spread were observed at the expected synchrobetatron resonance coupling condition of ${\ensuremath{\nu}}_{s}=0.068$, which is the first observation of a resonantly induced coupling for enhanced indirect transverse laser cooling of an ion beam, and is an important step towards creating a crystalline ground state of the beam.

A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H2 gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

A laser-driven repetition-rated 1.9 MeV proton beam line composed of permanent quadrupole magnets (PMQs), a radio frequency (rf) phase rotation cavity, and a tunable monochromator is developed to evaluate and to test the simulation of laser-accelerated proton beam transport through an integrated system for the first time. In addition, the proton spectral modulation and focusing behavior of the rf phase rotation cavity device is monitored with input from a PMQ triplet. In the 1.9 MeV region we observe very weak proton defocusing by the phase rotation cavity. The final transmitted bunch duration and transverse profile are well predicted by the PARMILA particle transport code. The transmitted proton beam duration of 6 ns corresponds to an energy spread near 5% for which the transport efficiency is simulated to be 10%. The predictive capability of PARMILA suggests that it can be useful in the design of future higher energy transport beam lines as part of an integrated laser-driven ion accelerator system.

The dynamics of a MeV laser-produced proton beam affected by a radio frequency (rf) electric field has been studied. The proton beam was emitted normal to the rear surface of a thin polyimide target irradiated with an ultrashort pulsed laser with a power density of $4\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$. The energy spread was compressed to less than 11% at the full width at half maximum (FWHM) by an rf field. Focusing and defocusing effects of the transverse direction were also observed. These effects were analyzed and reproduced by Monte Carlo simulations. The simulation results show that the transversely focused protons had a broad continuous spectrum, while the peaks in the proton spectrum were defocused. Based on this new information, we propose that elimination of the continuous energy component of laser-produced protons is possible by utilizing a focal length difference between the continuous spectral protons and the protons included in the spectral peak.

A novel technique for forming internal targets, named SCRIT (Self-Confining RI Ion Target), has been developed, which can make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. SCRIT confines the ions of interest by utilizing the “ion trapping” phenomenon in the electron storage ring. Approximately 107 stable 133Cs ions were trapped in a three-dimensional configuration along the electron beam axis at an electron beam current of 75mA. The angular distribution of the electrons scattered from the trapped 133Cs ions was successfully measured, and a collision luminosity of 1026/(cm2 s) was achieved.

A phase rotation scheme of laser‐produced ions from a solid target by the application of a synchronized RF electric voltage with a pulsed laser has been experimentally investigated with the use of a 100 TW laser, J‐KAREN at JAEA, KPSI. Up to now, energy peaks of up to around 2.0 MeV have been created with a FWHM of 2.6% with good reproducibility using a two‐gap resonator of a quarter wave length with the same frequency as the source laser (∼80 MHz). It is also found that the position of the peak can be well controlled by adjusting the relative phase between the RF electric field and the laser, which is very promising for real applications of such laser‐produced protons. In order to also apply such a phase rotation system for higher energy protons (

We carried out a demonstrative electron scattering experiment using a novel ion-trap target exclusively developed for short-lived highly unstable nuclei. Using stable $^{133}\mathrm{Cs}$ ion as a target, this experiment completely mimicked electron scattering off short-lived nuclei. Achieving a luminosity higher than ${10}^{26}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ with around only ${10}^{6}$ trapped ions on the electron beam, the angular distribution of elastic scattering was successfully measured. This experiment clearly demonstrates that electron scattering off rarely produced short-lived nuclei is practical with this target technique.

A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An "ion trapping" phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7 x 10(6) stable 133Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8) x 10(25) cm(-2) s(-1) by measuring elastically scattered electrons.

At S-LSR, abrupt reduction of momentum spread of 7 MeV proton beam to ~2 times 10-6 at proton number of -2000 has been observed, which indicates phase transition to 1 dimensional ordered state. Attained proton temperatures after transition are 26 mueV and 1 meV for longitudinal and transverse directions, respectively, which compared with the corresponding values of 20 mueV and 34 meV for electron beam, indicates the magnetization of electron. Laser cooling of 24Mg+ has also been started and momentum spread of ~108 ions is reduced to 2 times 10-4, saturated with the momentum transfer from transverse degree of freedom by intra-beam scattering.

The ordering of protons has been observed at a new storage ring, S-LSR, at Kyoto University. Abrupt jumps in the momentum spread and the Schottky noise power were observed for protons for the first time at a particle number of $\ensuremath{\sim}2000$, upon applying electron cooling with electron currents of 25, 50, and 100 mA. The transition temperature was 0.17 and 1 meV in the longitudinal and transverse directions, respectively. The transverse temperature of the proton beam was much below that of electrons at the transition, which played an essential role in the ordering of protons.

At ICR, Kyoto University, an ion storage and cooler ring, S‐LSR has been constructed. Its mean radius and maximum magnetic rigidity are 3.6 m and 1.0 Tm, respectively. 24Mg+ ions with the kinetic energy of 35 keV are to be laser‐cooled by the frequency doubled ring dye laser with the wavelength of 280 nm. In order to avoid the shear heating, dispersion compensation is planned by the overlap of the electric field with the dipole magnetic field in all 6 deflection elements. Intermediate electrodes, which can be potential adjusted, are to be utilized so as to realize a uniform electric field radial direction within a rather limited vertical gap, 70 mm of the dipole magnet. Synchro‐betatron coupling needed for 3‐dimensional laser cooling is to be realized by placing the RF cavity at the siraight section with finite dispersion for the normal mode lattice, which is expected to realize 1 dimensional string. For the case of dispersion compensated lattice to suppress the shear heating, possibility of realizing “ta...

A compact ion cooler ring, S‐LSR is under construction in Kyoto University. One of the subjects of S‐LSR is a realization of the crystalline beams using the electron beam and the laser cooling. The ring is designed to be satisfied several required conditions for the beam ordering, such as a small betatron phase advance, a small magnetic error and a precise magnet alignment. The design phase advance per a period is less than 127 degree. The calculated closed orbit distortion and the stopband is less than 1 mm and 0.001 without correction, respectively.

Electron scattering is a superior method to investigate the internal structure, such as charge distribution, of atomic nuclei. Most of the radii of nuclei were determined unambiguously by that. However, radioactive isotopes (RI) which recently came up to a major research interest have not been accessible due to the difficulty in making fixed targets and taking measurements before they decay. We proposed a conceptually new target called SCRIT (Self‐Confining Radioactive Isotope ion Target) as opposed to a collider method. The luminosity expected for SCRIT is inevitably low (typically on the order of 1.E+27/cm2/s) and a large acceptance detector system is required. We plan to perform a coincidence measurement using an electron arm and a recoil ion detector which needs to be developed. Current status of the ion trapping with a prototype SCRIT and the background measurement results in an electron storage ring will be discussed.

An experiment to control dispersion of beams in one bending section has been carried out. This experiment is based on a theory that the dispersion of accumulated beams can be controlled, if they are bent by a cross field composed of magnetic and an electric fields. Suppression of the dispersion can ease a shear which affects the 3‐dimensionally ordered structure of the ultimate‐low‐temperature beams. In order to realize this scheme experimentally, we have manufactured a set of electrodes to create precise electric fields whose strength is 6.6 × 104 V/m for 24Mg+, 35keV beam. The electrodes have been inserted to the gap of dipole magnet. 3‐dimensional field calculation shows that the error of the electric fields is less than 0.1% within ± 5mm from the reference orbit. We also tested the effect of the electric field using a single set of bending elements. The result showed that the linear dispersion can be controlled or canceled by changing the ratio of magnetic and electric fields.

A novel method has been established to realize the experiment of electron scattering off short-lived nuclei. The method was based on the well known "ion trapping" phenomenon in electron storage rings. In the R&D experiments at Kyoto University, stable nucleus, 133Cs, was employed as the target nucleus. The luminosity of scattering experiment was nearly 1026 cm−2s−1 at electron beam current around 75 mA. The angular distribution of elastically scattered electrons from trapped Cs ions was measured and the result was well fitted by theoretical calculation. It was indicated that higher luminosity can be reached with larger electron beam current.

The efficiency of indirect transverse laser cooling with synchro-betatron resonance coupling has been improved with the reduction in beam intensity by scraping the tail part of the beam. In order to measure the beam size at a low beam intensity, a new scheme to measure the beam profile by observation of the survival ratio with changing the scraper position has been established. With 104 particles, the transverse cooling time was reduced to 1.2 s, and the cooled horizontal and vertical beam sizes were 0.19 and 0.61 mm, corresponding to temperatures of 20 and 29 K, respectively, which is largely improved compared with that in our previous experiment [Nakao et al.: Phys. Rev. ST Accel. Beam 15 (2012) 110102].

Permanent magnet quadrupoles (PMQ) and sextupoles (PMSx) have been fabricated and tested. Their effective strengths are variable. The PMQ has been developed as a final focus magnet for a linear collider. There is enough space to put Gluckstern's 5-ring singlet structures in each incoming beam line. The magnetic center offsets and higher harmonic components can be adjusted by adjusting the positions of the magnet pieces with screws on holders. The measured integrated gradient can be reduced down to less than 1% of the maximum strength. The PMSx has been developed to focus pulsed cold neutrons for a small angle neutron scattering (SANS) experiment. The strength is modulated by a so called double ring structure, where the inner ring is fixed and the outer ring is rotated. A torque canceller can reduce the torque to rotate the outer ring by one third of its original magnitude. The focal length of the fabricated triplet lens is less than 50 cm for Very Cold Neutrons (VCN). It is demonstrated that VCN-SANS can shorten a SANS beamline, which usually has a few tens of meters, down to 2~3 meters.

A laser-cooling experiment of a 40 keV 24Mg+ beam was carried out in the small laser-equipped storage ring (S-LSR). A laser co-propagating with the beam and an induction accelerator were utilized in the experiment. The lowest longitudinal temperature achieved in the present experiment was 3.6 K for 3?104 ions stored in the ring. It was found that the number of stored ions is related to the temperature at the final equilibrium state of the laser cooling. This relation shows that the longitudinal temperature of the laser-cooled beam linearly couples with the transverse one through intra-beam scattering.

Laser ion production has been studied for downsizing of the accelerator dedicated for cancer therapy. For optimization of various parameters such as pre-pulse condition, target position, laser spot size on the target, laser pulse width and so on, time of flight (TOF) measurement utilizing the detected signal by a plastic scintillation counter played an essential role for real time measurement. Protons up to ~900 keV and ~600 keV are produced from the thin foil targets of Ti 3 μm and 5 μm in thickness, respectively. Modification of the energy distribution of the laser-produced ions with Maxwell distribution by utilizing an RF electric field synchronized to the pulse laser, which is the rotation of the ion beam in the longitudinal phase space (Phase Rotation), has been demonstrated for the first time. By using the Ti Sapphire laser of the wave length and pulse duration of 800 nm and a few hundreds fs, respectively, intensity increase of factor 3 in a certain energy bins is attained creating energy peaks with the energy spread about 7 %, which is found to be reproduced with good probability.