Hideshi Muto

Slow beam extraction at TARN II

Abstract A slow beam extraction system using the third order resonance has been constructed at TARN II and beam extraction tests have been performed. By the ordinary scheme where the tune is shifted to the resonance with ramping the excitation strength of the lattice quadrupole magnets, an extraction efficiency of 90% is attained. A new scheme increasing the horizontal emittance of the circulating beam is applied to extract the beam. A very long beam spill of 800 s is obtained by this scheme. A method using a transverse rf field is also studied experimentally, resulting in an extracted beam with smaller emittance.

Hybrid-type long-lived carbon stripper foils

Abstract A new method for the preparation of hybrid-type long-lived carbon stripper foils was developed. The new procedure is based on a modification of our controlled dc arc-discharge method. The carbon foils are of the multilayer type and the layers are composed of carbon particles emitted from the electrodes in the ac arc-discharge and from the cathode in the dc arc-discharge. With this simple and powerful method long lived carbon stripper foils can be prepared with higher reliability and reproducibility than with the previous procedure.

Development of heavy ion beam sputtering method for long-lived carbon stripper foils

Abstract A heavy noble gas ion beam sputtering (HIBS) technique was developed to prepare carbon stripper foils with a characteristic of long lifetime. The dependence of lifetimes on the mass of noble gas was also investigated. Compared with foils made by lighter ions such as Ne and Ar, the foils made by Kr and Xe noble gases were not so much stronger mechanically, but were long-lived under bombardment with a 3.2 MeV Ne+ ion beam 3 μA in intensity and 3.5 mm in diameter. The mean lifetime in the case of Kr sputtering gas was around 51 mC, 20 times longer than that of commercially available foils. The key point in producing long-lived foils with Kr or Xe noble gas ions was found to be to decrease the amount of oxygen contaminants as much as possible.

Nitrided carbon foils as long-lived charge strippers

Abstract Nitrided carbon stripper foils with excellent lifetimes and mechanical properties have been made by a new method based on reactive nitrogen-ion-beam sputtering. The foils showed no shrinkage and maintained mechanical flexibility during long periods of irradiation by ion beams. The average integrated current stripped by such foils before breakage was 75 mC using a 3.2 MeV Ne+ beam flux of 4 μA, 3.5 mm in diameter. This capability is about 30 times greater than commercially available carbon stripper foils. Details are given for the method of preparation and the compositions of the foils produced.

Behaviour of carbon stripper foils prepared by a mixed ion beam sputtering method

Abstract Carbon stripper foils have been prepared by a mixed ion beam sputtering method and the lifetime measured by using 3.2 MeV Ne+ ions. Foils prepared by the mixed ion beam sputtering method have lifetimes ranging from 10 to 125 times longer than those produced by thermal evaporation method. Changes in foil thickness with increasing fluence were examined. The lifetime and sputtering ratio of the carbon foils were found to be strongly dependent on thickness.

Production of beams from solid materials at Center for Nuclear Study electron cyclotron resonance ion sourcea)

Two methods for the feed of vapor from solid materials in the Center for Nuclear Study ECR ion source are described. A rod placed near the wall of the plasma chamber, operating up to a melting point of 2600 °C, has been used for CaO, SiO2, and FeO. An oven with a number of openings, operating up to 800 °C, has been used for P2O5, Li, and S. Typical ion beam intensities of (7)Li(2+), (6)Li(3+), (40)Ca(12+), and (56)Fe(15+) are achieved 280, 75, 28, and 7 eμA, respectively. High intensity heavy ion beams are stably supplied into the azimuthally varying field cyclotron.

Grating monochromator for electron cyclotron resonance ion source operation

Recently, we started to observe optical line spectra from an ECR plasma using a grating monochromator with a photomultiplier. The light intensity of line spectrum from the ECR plasma had a strong correlation with ion beam intensity measured by a magnetic mass analyzer. This correlation is a significant information for beam tuning because it allows the extraction of the desired ion species from the ECR plasma. Separation of ion species of the same charge to mass ratio with an electromagnetic mass analyzer is known to be an exceptionally complex process, but this research gives new insights into its simplification. In this paper, the grating monochromator method for beam tuning of a Hyper-ECR ion source as an injector for RIKEN azimuthal varying field (AVF) cyclotron is described.

Plasma spectroscopy of metal ions for hyper-electron cyclotron resonance ion sourcea)

In this research, the optical line spectra of metal ions from ECR plasma were observed using a grating monochromator with a photomultiplier. The light intensity of line spectrum from the ECR plasma had a strong correlation with ion beam intensity measured by a magnetic mass analyzer. This correlation is a significant information for the beam tuning process, because it allows to conduct the extraction of the desired metal ion species from the ECR plasma. Separation of ion species of the same charge to mass ratio with an electromagnetic mass analyzer is known to be an exceptionally complex process, but this research provides a new approach for its simplification. In this paper the grating monochromator method for metal ion beam tuning such as (40)Ca(12+), (56)Fe(15+), and (85)Rb(20+) of hyper-ECR ion source as an injector for RIKEN Azimuthal Varying Field cyclotron is described.

Characteristics and beam tracking of a compact storage ring for FEL operation

Abstract The CSA (Compact Storage and Acceleration) ring for FEL was projected in 1989 [T. Hattori et al., Proc. 14th Linear Accelerator Meeting, Japan (1989) 212]. The lattice of the ring is a double bend double achromatic type. The circumference is 15 m. In spite of the short circumference, the ring has two long straight sections for undultors. The bending magnets were completed and their magnetic field strength was measured [Y. Takahashi et al., Proc. 8th. Symp. on Accelerator Science and Technology 8 (1991) 419]. This paper will present the design and the characteristics of the ring. Furthermore, results of beam tracking are reported.

Note: An innovative method for 12C4+ suppression in 18O6+ beam production in an electron cyclotron resonance ion source

It is a major and complex task to accelerate an ion which has the same charge to mass ratio with strong contaminant ions, such as 12C4+ in the 18O6+ beam. An innovative method has been developed to suppress the contaminant ions in the Electron Cyclotron Resonance (ECR) ion source by introducing Li vapor. The ion distribution inside the ECR zone was obtained by the optical analysis of ions inside the ECR ion source. The 12C4+ ions were suppressed as much as by a factor of 10, whereas the 18O6+ beam changed little with the use of this technique.