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To provide a very powerful vanadium (V) beam with an intensity of at least 6 particle μA for synthesizing a new superheavy element (SHE) with atomic number Z = 119, we have developed a high-temperature oven (HTO) system to evaporate the metallic V powder inside the new superconducting (SC) electron cyclotron ion source. We successfully extracted a V13+ beam with a maximum beam intensity of 600 eμA with 2.8-kW microwave power and 900-W heating power of the HTO. Furthermore, from a systematic study of the dependence of the beam intensity on the microwave power and the HTO power, we successfully produced a V13+ beam of 300 eμA at a consumption rate of 3 mg/h, allowing a one-month duration continuous beam to carry out the SHE synthesis. In addition, to avoid serious damage to newly introduced SC acceleration cavities by beam losses, the beam should be transported with a well-controlled emittance. To efficiently limit the beam emittance, we employed a slit triplet consisting of three pairs of slits installed around the focus point of the low-energy beam transport. The first result of the emittance reduction was observed by a pepper-pot type emittance meter as a function of the acceptance of the slit triplet. [ABSTRACT FROM AUTHOR]

A new RIKEN 28-GHz superconducting electron cyclotron resonance ion source (SC-ECRIS) has been installed for the superconducting RIKEN linear accelerator (SRILAC). The new SC-ECRIS control system mainly consists of programmable logic controllers (PLCs) embedded with the Experimental Physics and Industrial Control System. To improve the reliability as compared with previous control systems, two types of PLC central processing units, sequential and Linux, have been installed in the same unit. Past experience has shown that new types of designs that can rapidly respond to system scalability are key. By connecting PLC stations using star-topology field buses, their rapid and cost-effective response to system changes is realized for the new devices. Furthermore, a unique data acquisition system employing a 920-MHz-band radio was developed to measure analog data such as the temperature at the high-voltage stage. [ABSTRACT FROM AUTHOR]

We measured the beam intensity of highly charged heavy ions and x-ray heat load for RIKEN superconducting electron cyclotron resonance ion source with 28 GHz microwaves under the various conditions. The beam intensity of Xe20+ became maximum at Bmin ∼ 0.65 T, which was ∼65% of the magnetic field strength of electron cyclotron resonance (BECR) for 28 GHz microwaves. We observed that the heat load of x-ray increased with decreasing gas pressure and field gradient at resonance zone. It seems that the beam intensity of highly charged heavy ions with 28 GHz is higher than that with 18 GHz at same RF power. [ABSTRACT FROM AUTHOR]

Cluster structures in the neutron-rich nucleus 12Be were experimentally investigated via α-inelastic scattering. Excited states in the 12Be nucleus were populated by a 12Be(αα') reaction at 60 A MeV in the inverse kinematics, and identified by measuring a 6He+6He and α+8He breakup channels in coincidence. The differential cross section and the angular correlations between the decay particles were obtained for each excitation energy at 10–20 MeV for 6He+6He and at 9–19 MeV for α+8He, respectively, reconstructed by the measured momentum vectors of the two helium isotopes. A multipole decomposition analysis based on the distorted-wave Born approximation was applied for the angular distribution of the inelastic scattering together with the angular correlation between the decay particles with respect to the directions of the incident beam and to the momentum transfer simultaneously. From the decomposed excitation energy spectra for J=0-4, several new excited states were identified. The 0+ excited states were candidates of the band-head of a largely deformed rotational band. The 11.3-MeV 0+ state was found to decay only into the 6He+6He channel. This result support the recent theoretical result by the generalized two-center cluster model. Several negative-parity excited states were observed in the α+8He channel. These excited states possibly forming a negative-parity rotational band, which is very closed to the positive-parity band, can be connected to the existence of the extremely developed cluster structure in 12Be. [ABSTRACT FROM AUTHOR]

The next generation heavy ion accelerator facility, such as the RIKEN radio isotope (RI) beam factory, requires an intense beam of high charged heavy ions. In the past decade, performance of the electron cyclotron resonance (ECR) ion sources has been dramatically improved with increasing the magnetic field and rf frequency to enhance the density and confinement time of plasma. Furthermore, the effects of the key parameters (magnetic field configuration, gas pressure, etc.) on the ECR plasma have been revealed. Such basic studies give us how to optimize the ion source structure. Based on these studies and modern superconducting (SC) technology, we successfully constructed the new 28 GHz SC-ECRIS, which has a flexible magnetic field configuration to enlarge the ECR zone and to optimize the field gradient at ECR point. Using it, we investigated the effect of ECR zone size, magnetic field configuration, and biased disk on the beam intensity of the highly charged heavy ions with 18 GHz microwaves. In this article, we present the structure of the ion source and first experimental results with 18 GHz microwave in detail. [ABSTRACT FROM AUTHOR]

We have been developing a high-temperature oven using UO2 in the 28 GHz superconducting electron cyclotron resonance ion source at RIKEN since 2013. A total of eleven on-line tests were performed. The longest operation time in a single test was 411 h, and the consumption rate of UO2 was approximately 2.4 mg/h. In these tests, we experienced several problems: the ejection hole of a crucible was blocked with UO2 and a crucible was damaged because of the reduction of tungsten strength at high temperature. In order to solve these problems, improvements to the crucible shape were made by simulations using ANSYS. [ABSTRACT FROM AUTHOR]

A RIKEN 18 GHz electron cyclotron resonance ion source (18 GHz ECRIS) is used as an external ion source at the Radioactive Ion Beam Factory (RIBF) accelerator complex to produce an intense beam of medium-mass heavy ions (e.g., Ca and Ar). In most components that comprise the RIBF, the control systems (CSs) are integrated by the Experimental Physics and Industrial Control System (EPICS). On the other hand, a non-EPICS-based system has hardwired controllers, and it is used in the 18 GHz ECRIS CS as an independent system. In terms of efficient and effective operation, the 18 GHz ECRIS CS as well as the RIBF CS should be renewed using EPICS. Therefore, we constructed an 18 GHz ECRIS CS by using programmable logic controllers with embedded EPICS technology. In the renewed system, an operational log system was developed as a new feature, for supporting of the18 GHz ECRIS operation. [ABSTRACT FROM AUTHOR]

For RIKEN radio isotope beam project, we started to construct the new superconducting electron cyclotron resonance ion source (SC-ECRIS), which has an operational frequency of 28 GHz, in 2007. The main feature of this ion source is that we can produce large size of resonance zone with six sets of solenoid coils. Before starting, we intensively studied the effect of several key parameters of ECRIS (magnetic field configuration, microwave power density, negatively biased disk) on the plasma. In this article, we describe the effect of key parameters on the plasma and detailed structure of the new SC-ECRIS. [ABSTRACT FROM AUTHOR]

The Coulomb dissociation of 27P was studied experimentally using 27P beams at 57MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in 27P was determined to be (2.8±0.5)×10-5eV. The total ( M1 + E2) gamma decay width of the state, which is of astrophysical interest, is estimated by combining the experimental result and a shell model calculation. The reaction rate of 26Si(p,γ)27P is deduced from the estimated total gamma decay width. The astrophysical implication derived from estimated gamma decay width is discussed. [ABSTRACT FROM AUTHOR]

We measured the main plasma parameters (density of electron, temperature of electrons, and ion confinement time) as a function of Bmin and Binj with laser ablation technique. We observed that the Bmin mainly affects the temperature and density of electrons and all of the three parameters increase with increasing the Binj. We also observed that the gas pressure of the plasma chamber at the rf injection side became minimum at the optimum value for Bmin at fixed gas flow. This result indicates that the ionization efficiency becomes maximum at optimum value for Bmin. From these results, it is concluded that the plasma production is strongly dependent on the Bmin (plasma generator). We also observed that the Binj affects the ion confinement time, temperature, and density of electrons. All of the three parameters increase with increasing Binj. [ABSTRACT FROM AUTHOR]

We have constructed four high performance electron cyclotron resonance (ECR) ion sources in RIKEN and produced a variety of intense beams of heavy ions (e.g., 2 emA of Ar8+, 0.6 emA of Kr13+, 0.3 emA of Xe20+). During the improvement of their performance, we found that several key parameters play essential role on increasing the beam intensity. The parameters are plasma electrode position, magnetic field configuration, property of the chamber wall material and position of a biased disk. To investigate how the parameters influence on the beam intensity, we made a systematic study using the laser ablation method. In these experiments, we observed that Bmin influences the electron density and confinement time of ECR plasma. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line. [ABSTRACT FROM AUTHOR]

In order to produce a high-intensity and stable 48Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we have begun testing the production of a calcium beam using a micro-oven. To minimize the consumption rate of the material (48Ca), we introduced the "hot liner" method and investigated the effect of the liner on the material consumption rate. The micro-oven was first used to produce the 48Ca beam for experiments in the RIKEN radioisotope beam factory, and a stable beam could be supplied for a long time with low consumption rate. [ABSTRACT FROM AUTHOR]

Over the past two years, we have tried to improve the performance of the RIKEN superconducting electron cyclotron resonance ion source using several methods. For the production of U vapor, we chose the sputtering method because it is possible to install a large amount of material inside the plasma chamber and thus achieve long-term operation without a break, although it is assumed that the beam intensity is weaker than in the oven technique. We also used an aluminum chamber instead of a stainless steel one. Using these methods, we successfully produced ~180 eµA of U35+ and ~230 eµA of U33+ at the injected radio frequency (RF) power of ~4 kW (28 GHz). Very recently, to further increase the beam intensity of U35+, we have started to develop a high temperature oven and have successfully produced a highly charged U ion beam. In this contribution, we report on the beam intensity of highly charged U ions as a function of various parameters (RF power and sputtering voltage) and discuss the effects of these parameters on the beam stability in detail. [ABSTRACT FROM AUTHOR]

We have been developing the 28 GHz ECR ion source in order to accelerate high-intensity uranium beams at the RIKEN RI-beam Factory. Although we have generated U35+ beams by the sputtering method thus far, we began developing a high-temperature oven with the aim of increasing and stabilizing the beams. Because the oven method uses UO2, a crucible must be heated to a temperature higher than 2000 °C to supply an appropriate amount of UO2 vapor to the ECR plasma. Our high-temperature oven uses a tungsten crucible joule-heated with DC current of approximately 450 A. Its inside dimensions are φ 11 mm x 13.5 mm. Since the crucible is placed in a magnetic field of approximately 3 T, it is subject to a magnetic force of approximately 40 N. Therefore, we used ANSYS to carefully design the crucible, which was manufactured by machining a tungsten rod. We could raise the oven up to 1900 °C in the first off-line test. Subsequently, UO2 was loaded into the crucible, and the oven was installed in the 28 GHz ECR ion source and was tested. As a result, a U35+ beam current of 150 µA was extracted successfully at a RF power of approximately 3 kW. [ABSTRACT FROM AUTHOR]

In order to supply a high-intensity and stable 48Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we are conducting operational tests of a micro-oven. A mixture of CaO and Al powders is placed into the crucible of the micro-oven and heated to produce metallic calcium by a reductive reaction. The successful production of a calcium beam was confirmed. In addition, we reduced the material consumption rate by using a so-called "hot liner," and we enhanced the beam intensity by applying a negative voltage bias to the micro-oven, the effect of which is similar to the effect of a "biased disk." [ABSTRACT FROM AUTHOR]

The control system for the RIKEN 28 GHz superconducting electron cyclotron resonance ion source (28 GHz SC-ECRIS) consists of a distributed control system based on the experimental physics and industrial control system. To maintain the beam quality for the long beam-service time at the radioactive isotope beam factory, beam tuning to prevent subtle changes in the 28 GHz SC-ECRIS conditions is required. Once this is achieved, it should then be possible to check conditions and operate the ion source at any time. We have designed a web-based operational interface to remotely control the ion source, but for access and control from several locations, suitable access security, policies, and methods are required. We thus implemented an operator intervention system that makes it possible to safely access the network externally with the permission of on-site accelerator operators in the control room. [ABSTRACT FROM AUTHOR]

A highly charged uranium (U) ion beam is produced from the RIKEN superconducting electron cyclotron resonance ion source using 18 and 28 GHz microwaves. The sputtering method is used to produce this U ion beam. The beam intensity is strongly dependent on the rod position and sputtering voltage. We observe that the emittance of U35+ for 28 GHz microwaves is almost the same as that for 18 GHz microwaves. It seems that the beam intensity of U ions produced using 28 GHz microwaves is higher than that produced using 18 GHz microwaves at the same Radio Frequency (RF) power. [ABSTRACT FROM AUTHOR]

For the RIKEN radio isotope factory (RIBF) project, we produced the multicharged uranium beam with two methods. To produce lower charge state U ion beams (14+–20+) we used the UF6 gas as an ionized gas. The typical beam intensity of U14+–20+ was 2–1 particle μA at the extraction voltage of 14 kV. To produce higher charge state U ion beam (U35+), we chose the sputtering method. The beam intensity was 70 particle nA at the extraction voltage of 5.4 kV. Using this method, we successfully produced multicharged U beam continuously for one month without break for RIBF commissioning. [ABSTRACT FROM AUTHOR]

The plasma potential of liquid-He-free superconducting electron cyclotron resonance ion source was measured as a function of minimum strength of mirror magnetic field (Bmin) and gas pressure with the method based on the retarding electric field. We observed that the plasma potential decreased with increasing Bmin up to 0.5 T and then gradually increased again. The plasma potential increased with increasing gas pressure. When we add the O2 gas to the Ar plasma (gas mixing method), plasma potential gradually decreased with increasing the O2 gas pressure. [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]

In order to investigate the ion-optical parameters of the RIKEN 18 GHz electron cyclotron resonance ion source injection line into the RIKEN RFQ linac, we measured the beam emittance for a wide mass range of the ions. First results indicate a strong extraction current dependence of the normalized emittance. When using the insertion method to produce metallic ions from solid rod with high melting point, we observed that the beam emittance of metallic ions was very large compared to the beam emittance of ions from gaseous element. It may be due to the plasma instability caused by inserting the rod into the plasma deeply. © 2004 American Institute of Physics. [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]

To investigate the effect of the plasma electrode position on the beam intensity, we measured the beam intensity of Ar ions, with various charge states as a function of the electrode position. In this experiment, we observed that the beam intensity of highly charged Ar ions is strongly dependent on the electrode position and that there is the suitable position to maximize the beam intensity. The optimum position varies with the charge state of ions. The beam intensity of 1.3 mA for Ar[sup 8+] was obtained at the optimum plasma electrode position. [ABSTRACT FROM AUTHOR]

Intense beams of heavy ions with medium charge states (1.3 mA of Ar[sup 8+], 200 µA of Xe[sup 20+]) have been produced from a RIKEN 18 GHz electron cyclotron resonance ion source (ECRIS) using various kinds of techniques, e.g., utilization of an aluminum cylinder and a biased disk, and optimization of the plasma electrode position. Furthermore, we have recently constructed two superconducting ECRISs (operational frequencies of 14 and 18 Hz) which have unique characteristics, i.e., they do not need liquid He to obtain the superconductivity of solenoid coils and utilize the G-M refrigerator instead. These sources are suitable to generate intense beams of heavy ions with very high charge states. We obtained 10 µA of Xe[sup 30+], 5 µA of Xe[sup 33+], and 1.5 µA of Xe[sup 36+] at a radio frequency power of 700 W (14 GHz microwave) without using the gas mixing method. Through various experiments, we confirmed that not only the magnetic field strength and microwave power but also the characteristics of the plasma chamber surface play the essential role for the production of highly charged heavy ions. [ABSTRACT FROM AUTHOR]

The effect of the surface of A1[sub 2]O[sub 3] on the beam intensity of highly charged Ar ions is described. To investigate this effect clearly, we directly plated the surface with 20 µm A1[sub 2]O[sub 3] of the Al cylinder (A1[sub 2]O[sub 3] plating method). This cylinder was inserted into the plasma chamber and it covered its inner wall of. We then measured the beam intensity of highly charged Ar ions carefully. By comparing the beam intensity using the A1[sub 2]O[sub 3] plating method and the Al cylinder, it is confirmed that the A1[sub 2]O[sub 3] surface is very effective in increasing the beam intensity of highly charged heavy ions. The best result of 290 eµA of Ar[sup 11+] was obtained by using this method. [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]

We have started a new project, in which we have utilized an electron cyclotron resonance ion source (ECRIS) and a heavy ion linac for trace element analysis. This combination is expected to identify many kinds of trace elements simultaneously with very low background [very low detection limits (sub-pg/g) were attained by this method] without the pretreatment of a sample. This system is also applicable to fast neutron radiography, because it is possible to produce intense fast neutron beams. When we produce 100 μA of a Li beam from the ECRIS and use the nuclear reaction of H(Li,n)B at ∼2 MeV/u for production of neutrons, we can easily produce an intense focused fast neutron beam (∼2 MeV, 10[sup 10] particles/s). It has great advantages for neutron radiography. (1) We can minimize the background of the neutrons and gamma rays produced by the neutron-induced reaction, because the neutrons are emitted just at a forward angle. (2) Intense fast neutron beams can be easily produced. This kind of beam is very useful for fast neutron radiography. In this article, we present the experimental results of trace element analysis of several ceramic rods. We also present the basic idea of fast neutron radiography using this system and the planned experiment in detail. [ABSTRACT FROM AUTHOR]

The stellar reaction 26Si(p,γ) 27P was studied in the Coulomb dissociation of 27P. Two known resonance levels in 27P were excited and a candidate for the third excited state was found in the 26Si p relative energy spectrum. The E2 resonance strengths wy were obtained to be (6.5 ± 1.3) x 10-11, (6.0 ± 1.1) x 10-10, and (1.10 ± 0.27) x 10-10 MeV. The total (E2 + M1) ϖγ value for the first excited state was evaluated to be Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed with the help of the shell model. The error was estimated from the deviation of theoretical predictions with the same shell model from experimental strengths obtained in the present study for 27P and earlier ones for the mirror nucleus 27Mg. The astrophysical reaction rate for the 26Si(p,γ) 27P reaction was also calculated and compared with previous estimations. [ABSTRACT FROM AUTHOR]

Isoscalar monopole and dipole responses in unstable nucleus 14O have been studied for a wide excitation energy range by inelastic α scattering at 60 A MeV in inverse kinematics. In order to deduce isoscalar compressional strengths, the multipole decomposition analysis was carried out and the DWBA calculation for isoscalar excitation was studied. Result from the multipole decomposition analysis, isoscalar monopole and dipole strengths were identified corresponding to 63±12% and 109±15% of energy-weighted sum rule in , respectively, for the measured decay channels of , , , , and . [Copyright &y& Elsevier]

Abstract: The excitation of the neutron-rich nucleus 28Ne has been investigated via heavy-ion inelastic scattering in reversed kinematics. The value was determined to be , which is smaller than expected from the low excitation energy of the first state. A comparison with theoretical predictions suggests that the suppressed collectivity in 28Ne is characteristic of nuclei lying on the boundary of the ‘island of inversion’. [Copyright &y& Elsevier]

The Coulomb dissociation of 27P was studied experimentally using 27P beams at 57 MeV/nucleon with a lead target. The E2 gamma decay width of the first excited state in 27P was extracted. Assuming the same E2/M1 mixing ratio as the one for the mirror nucleus 27Mg, the gamma decay width of the state, which is of astrophysical interest, is estimated to be ten times smaller than the value calculated by J. A. Caggiano et al. [Copyright &y& Elsevier]

The energy of the first excited state in the very neutron-rich nucleus 30Ne was determined via proton inelastic scattering. A liquid hydrogen target was bombarded by a radioactive 30Ne beam, and energies of the de-excitation γ rays emitted from excited 30Ne nuclei were measured. The observed transition is likely to be the one from the first 2+ state to the ground state of 30Ne. The excitation energy, 791 (26) keV, is lower than that of 32Mg, indicating an enhancement of deformation as the neutron excess increases in the N = 20 isotones. [Copyright &y& Elsevier]

The radiative width of the 3/2+ state at 6.793 MeV in 15O has been experimentally determined to be Γγ=0.95+0.60−0.95 eV by intermediate-energy Coulomb excitation. Our result independently supports the recent studies which point to a minor contribution of this state to the astrophysical rate of the 14N(p,γ)15O reaction in the CNO-cycle hydrogen burning in massive stars. [Copyright &y& Elsevier]

The energy of the first excited state of the very neutron-rich nucleus 30Ne was determined by proton inelastic scattering. A liquid hydrogen target was bombarded by a beam of radioactive 30Ne at 48 MeV/nucleon, and energies of the de-excitation γ rays emitted from the excited 30Ne were measured. The observed transition is likely to be the one from the first 2+ state to the ground state of 30Ne. The excitation energy, 791(26) keV, is lower than that of 32Mg, indicating enhancement of deformation as the neutron excess increases in the N=20 isotones. The results indicate that 30Ne belongs to the ‘island of inversion’. [Copyright &y& Elsevier]

A novel technique with a radioactive isotope beam has been employed for in-beam γ-ray spectroscopy of a very neutron-rich isotope 34Mg. The excited 34Mg were produced by the projectile fragmentation reaction induced by a radioactive 36Si beam at 50 MeV/nucleon on a 385 mg/cm2 9Be target. Deexcitation γ rays were detected in coincidence with the 34Mg fragments. The measured excitation energy, 660±10 keV, implies a large deformation of 34Mg. [Copyright &y& Elsevier]