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A linac consisting of six rf cavities has been constructed as an energy booster of the RIKEN heavy-ion linac. Various heavy ion beams have been accelerated to 5.8 MeV/u with intensities of more than 1 pμA (particle microampere) in the continuous-wave mode. The booster cavities are based on a quarter-wavelength resonator of a coaxial structure. The first two cavities are frequency-variable in a range from 36 to 76.4 MHz, whereas the last four are operated at a fixed frequency of 75.5 MHz. The design study started in 1997 and the booster was commissioned in 2001. The total voltage gain of the booster ever achieved is 11 MV, which is 70% of the designed value of 16 MV. The high-intensity beams from the booster have been successfully applied to a systematic study on the synthesis of superheavy elements. The beam energy from the ring cyclotron has also been increased, owing to the additional velocity gain provided by the booster. [ABSTRACT FROM AUTHOR]

Beam intensities of highly charged Ar ions (Ar11+,12+) were measured as a function of plasma electrode position. We observed that the beam intensity of Ar11+,12+ increased when putting the electrode far from the electron-cyclotron-resonance zone. On the other hand, lower charged heavy ions (Ar8+,7+) dramatically decreased. We observed that the intense beam extraction strongly affects the plasma condition. It may be due to the ion pumping effect. [ABSTRACT FROM AUTHOR]

We have developed a new analytical system that consists of an electron cyclotron resonance ion source (RIKEN 18 GHz ECRIS) and a RIKEN heavy ion linear accelerator (RILAC). This system is called trace element analysis using electron cyclotron resonance ion source and RILAC (ECRIS-RILAC-TEA). ECRIS-RILAC-TEA has several advantages as described in the work of Kidera et al. [AIP Conf. Proc. 749, 85 (2005)]. However, many experimental results during the last several years revealed a few problems: (1) large background contamination in the ECRIS, particularly at the surface of the plasma chamber wall, (2) high counting of the ionization chamber and the data taking system that is monitored by the direct beam from the accelerator, and (3) difficulty in the selection of the pilot sample and pilot beam production from the ECRIS for the purpose of normalization. In order to overcome these problems, we conducted several test experiments over the past year. In this article, we report the experimental results in detail and future plans for improving this system. [ABSTRACT FROM AUTHOR]

As required by the research group of super heavy elements, highly intense beams of 58Fe and 64Ni ions were produced from RIKEN 18 GHz electron cyclotron resonance ion source [Nakagawa et al., Nucl. Instrum. Methods Phys. Res. A 396, 9 (1997)] using the MIVOC method. Maximum intensities of the supplied ion beams were 20 eμA at the extraction voltage of 15.9 kV for 58Fe13+ and 90 eμA at the extraction voltage of 17.5 kV for 64Ni13+. Consumption rate was about 1.2 mg/h for 58Fe and 64Ni, respectively. For the Radio Isotope Beam Factory [Yano, Proceedings of the 15th International Conference on Cyclotron and Their Application [(IOP, Bristol, 1999)] and various requests from users groups, we constructed a double beam injector system for the two ion sources as an external ion source of the Riken Heavy Ion Linear Accelerator [Odera et al., Nucl. Instrum. Methods Phys. Res. A 221, 187 (1984)]. Two ion sources; RAMSES [Arai et al., Nucl. Instrum. Methods Phys. Res. A 491, 9 (2002)] and 18 GHz ECRIS, will be placed at these at the beginning of next year. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We measured the beam oscillation of RIKEN 18 GHz electron cyclotron resonance ion source for various conditions. In this experiment, the frequency of the beam oscillation increases with increasing the gas pressure and decreases with increasing rf power. The oscillation frequency is strongly dependent on the negative voltage of biased disk, i.e., the frequency increases with increasing the negative voltage. We observed that the frequency is strongly dependent on the mass of ionized gas. [ABSTRACT FROM AUTHOR]

A new method for evaluating thrust with high-frequency variations beyond the resonant frequency using a disturbance observer is presented. Setpoint control is applied to a conventional pendulum-type thrust stand to keep the pendulum at the target position using a solenoid actuator. During control, pendulum acceleration and solenoid-actuator current are measured, and the disturbance observer determines thrust with a wide range of frequency variations. The method allows thrust to be evaluated not only with constant and low-frequency variations, but also with high-frequency variations outside the resonant frequency. A thrust measurement device is prototyped to investigate accuracy over a wide frequency range from 0 to 100 Hz and the effects of the proportional-derivative-integral (PID) controller design. Calibration yields thrust measurement errors of 20% below 90 Hz. PID controller design has a smaller influence on the accuracy of the proposed method than the conventional null-balance method, so the proposed method requires the same stability under PID control as that for the null-balance method.