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To achieve high-resolution selection and separation of mono-isotopic beams through projectile fragmentation or in-flight fission and to efficiently transport the secondary beams to the Rare-RI Ring (R3) for mass determination, the BigRIPS separator combined with the High-resolution Achromatic (HA) beam-line of SHARAQ is served as a two-stage separator. The first stage from F0 to F2 is used for separation of the nuclei of interest through a Bρ-ΔE-Bρ method and the second stage from F3 to S0 is employed for identification of the beam with a Bρ-ΔE-TOF method. With this scheme, all the secondary ions can be well separated on an event by event basis and be utilized for mass measurements by two complementary methods: the conventional magnetic-rigidity-time-of-flight (Bρ-TOF) method employing the BigRIPS-HA beam-line to measure exotic nuclides within 1 μ s and the newly established isochronous mass spectrometry (IMS) approach via the R3 with a measurement duration less than 1 ms. This report presents the technique advances of the BigRIPS-HA-SHARAQ-R3 as a separator/spectrometer and give a brief description of its application to the complementary TOF methods for mass measurements at RIBF.

See paper for full list of authors; The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

The BigRIPS fragment separator in the RIKEN RIBF project is characterized by fourteen superconducting triplet quadrupoles (STQ's) with large apertures and high-field gradients. While the five STQ's on the first stage of the BigRIPS are cooled by a liquid helium cryogenic plant, the nine STQ's on the second stage are cooled by small cryocoolers on their cryostat. This first stage serves to produce and separate RI beams, so that the first two STQs are exposed to the high radiation from the production target and beam dumps, which causes radiation heat loads as well as radiation damages. Measurements of the radiation heat loads to the cryostats of the first two STQs during commissioning operations of the RIBF facility are reported.

We are preparing for a high resolution spectroscopy of the 1s and 2s pionic states of 121Sn in the 122Sn(d,3He) reaction at the incident deuteron energy of ~500 MeV. The measurement will provide accurate information on the strong interaction between the pion and the nucleus, which leads to quantitative determination of the magnitude of the quark condensate at the normal nuclear density.

The BigRIPS fragment separator in the RIKEN RI beam factory has an air-core type superconducting quadrupole triplet as the first focusing element. The quadrupole triplet consists of three air-core superconducting coils having effective lengths of 500 mm, 800 mm, and 500 mm, and the maximum field gradients of 24 T/m, 20 T/m, and 20 T/m. All three quadrupoles are assembled into a single cryostat and cooled by liquid-helium bath cooling using a cryogenic plant. The coils have a flat racetrack shape and their warm bore radii are 90 mm, 120 mm, and 120 mm. Its cryostat characterized by gas-cooled current leads with multiple electrodes is also discussed.

In the RI beam factory project, heavy ion beams are transported from the K 2500 MeV superconducting ring cyclotron (SRC) to the superconducting fragment separator, called BigRIPS. Magnets for the beam transport line from the SRC to the BigRIPS are reported. All the magnets are resistive type and the beam line consists of two kinds of dipoles and three kinds of quadrupoles. One of the dipole, having the maximum field strength of 2.0 T, a gap height of 60 mm, and a core length of 3.51 m is discussed in detail.

Measurements of the magnetic field distributions of the superconducting triplet quadrupoles (STQs) and the room-temperature dipoles for the BigRIPS separator are performed in order to use ion optics calculations of the BigRIPS. This report describes the results of magnetic field-map measurement of the superferric-typed STQ and dipole magnet including the field mapping device we employed for the measurements.

Since 1997, RIKEN Nishina Center has been constructing the Radioactive Isotope Beam Factory (RIBF) and succeeded in beam commissioning of its accelerator complex at the end of 2006. The world's first superconducting ring cyclotron (SRC) is the final booster in the RIBF accelerator complex which is able to accelerate all-element heavy ions to a speed of about 70% of the velocity of light. Assembling of the superconducting sector magnets was completed in August 2005. The superconducting coils were successfully cooled down and excited for tests on many operational aspects: magnetic force, coil protection and quality of magnetic field, showing that they work as designed. After a series of tests the other components were installed and tested under stray fields from the sector magnets. Local magnetic shields were put to the components which could not work under the stray fields. After setups of beam vacuum and radio frequency, beam commissioning started. The first beam was extracted at the end of 2006 and the first uranium beam was extracted in March 2007.

The RIKEN RI Beam Factory (RIBF) has started its operation after ten years of construction [1]. It is designed to provide beams of various kinds of unstable nuclei with the world's highest intensities. The institute RIKEN was founded in 1917, and covers a variety of research fields such as physics, chemistry, medical science, biology, and engineering. RIKEN has a long history of constructing accelerators. The first cyclotron in Japan was built in 1937 by Yoshio Nishina in the former RIKEN campus, and the RIKEN's 4th cyclotron completed in 1966 was the first heavy-ion cyclotron in Japan, which accelerated light nuclei to the energy around 7 MeV/nucleon.

In order to greatly upgrade the capability of its existing heavy-ion accelerator facility, RIKEN is constructing a new radioactive isotope (RI) beam facility, called “RI Beam Factory”. This facility is of an in-flight RI beam separation scheme. Three new ring cyclotrons with K-values of 570 MeV, 980 MeV and 2500 MeV, respectively, boost energies of the output beams from the existing K540-MeV ring cyclotron up to 440 MeV/nucleon for light ions and 350 MeV/nucleon for very heavy ions. The K2500-MeV ring cyclotron, SRC is the world’s first superconducting ring cyclotron. These energetic heavy-ion beams are converted into intense RI beams via projectile fragmentation of stable isotopes or in-flight fission of uranium isotopes by a superconducting fragment separator, BigRIPS. The combination of the SRC and the BigRIPS will greatly expand our knowledge of nuclear world into presently inaccessible region on the nuclear chart. The new ring cyclotrons and the Big RIPS will be commissioned in late 2006. Construction of a part of major experimental installations planned is expected to start in 2007.

Superconducting triplet quadrupoles (STQs) with large apertures and high field-gradients are employed for the in-flight radioactive-isotope (RI) beam separator BigRIPS at RIKEN. It consists of fourteen STQs and six room-temperature dipoles. The use of the STQs makes it possible to achieve important features of the BigRIPS separator: large acceptances and a large magnetic rigidity, allowing efficient production of RI beams. The BigRIPS separator is presently under construction and assembly as a major installation in the RIKEN RI-beam factory project, and the commissioning is scheduled in early 2007. In this paper we present the status and overview of the BigRIPS separator, emphasizing the STQs and their liquid-helium cryogenic systems.

RIKEN Nishina Center for accelerator-based science in RIKEN is constructing the radioactive isotope beam factory (RIBF), which is capable of providing the world's most intense RI beams over the whole range of atomic masses. The world's first superconducting ring cyclotron (SRC) is the final booster in the RIBF accelerator complex which is able to accelerate all-element heavy ions to a speed of about 70% of the velocity of light. Assembling of six superconducting sector magnets in the SRC vault was completed in August 2005. This paper describes results of their cool-down and excitation tests, which were performed to check the magnet system from the various points of views: magnetic force, coil protection, magnetic field and operation of their cryogenic cooling system.

Irradiation tests have been carried out in view of selecting the cryogenic temperature sensors for use in the RIKEN Superconducting Ring Cyclotron (SRC). About 300 temperature sensors will be installed, and most of them will be exposed to high radiation doses during the operation of accelerator. Those cryogenic temperature sensors, Cernox/spl trade/, CGR and PtCo, at room temperature were bombarded by the intense 210 MeV proton beam at the RIKEN Accelerator Research Facility (RARF) of RIKEN.

Three superferric quadrupoles with a pole-tip radius of 170 mm and a design field gradient of 14.1 T/m have been constructed and mapped for use as spectrometer elements. All three quadrupoles are assembled into a single cryostat and cooled by liquid-He bath cooling method. A small Gifford-McMahon/Joule-Thomson (GM/JT) cooler, mounted on the cryostat, requiries He gas that evaporates in the He vessel. The high-T/sub c/ superconducting current leads and radiation shield surrounding the He-vessel, cooled by a small GM cooler, reduce the heat load of the He vessel. Both cryocoolers operate using separate water-cooled compressors and allow us a stand-alone operation of the quadrupole magnets without big cryoplant. Results of quench protection tests, measured heat loads and mapped results are presented.

K2500 - superconducting ring cyclotron with 6-sectors is being constructed at RIKEN as one of the energy booster of the existing K540 ring cyclotron. The bending magnet for beam injection should be superconducting. Required fields are 3.8 T and radius of the coils is 1.2 m. After the fabrication, it was cooled down and excited. The magnet reached the designed field with one quench and training effect were clearly observed, which shows that it will works well to inject the beam into the superconducting cyclotron.

The sector magnets of the K2500-MeV superconducting ring cyclotron (SRC), which is under construction for the RIKEN RI beam factory, are described. The SRC consists of six sector magnets, four rf resonators, etc. each sector magnet is 7.2 m in length and 6 m in height and 800 t (metric ton) in weight; the sector angle is 25 deg. The required maximum magnetic field is 3.8 T. the superconductor for the main and trim coil has a rectangular shape (8 mm by 15 mm) consisting of a Rutherford-type NbTi cable located at the center of an Al-alloy stabilizer housing. The main coil is bath-cooled and the trim coil is directly cooled. Each component of the sector magnet as well as the cryogenic cooling system was completed in the spring of 2003.

A radio frequency quadrupole LINAC has been designed for the VECC-RIB project for an input beam energy of 1.0 keV/u and q/A≥1/16. The output energy will be about 90 keV/u for a 3.4 m long, 35 MHz structure. A half-scale cold model of the RFQ has been fabricated and tested for rf structure design study. The beam dynamics and rf-structure design along with the results of the cold model tests will be presented.

A K2500 superconducting ring cyclotron with 6-sectors is being constructed at RIKEN as one of the energy boosters of the existing K540 ring cyclotron. The bending magnet for beam injection should be superconducting. Required fields are about 4 T and the radius of curvature of the coils is about 1.2 m. Its design was finalized for real production based on successful results of the R&D coils. In this paper the final design will be described with the status of the fabrication.

Special designs have been adopted for the magnetic channels of the injection and extraction systems of the RIKEN Superconducting Ring Cyclotron (SRC). These magnetic channels are installed in the chambers between upper and lower coils of the sector magnets of the SRC, and superimpose additional magnetic fields on the base field of the sector magnets to inject or extract various beams. Maximum magnetic rigidity of the beam is considerably higher than that of conventional cyclotron, and the spaces to install the magnetic channels are limited by the size of the chambers and turn separation of the beams. Therefore powerful and compact magnetic channels are required. And besides, all magnetic channels were specified as normal-conducting magnets to reduce fabrication cost and to assure reliability. However, it is difficult to generate high magnetic fields by conventional normal-conducting magnetic channels with conductors only. Therefore, novel designs for powerful and compact normal-conducting magnetic channels were devised by use of iron as efficiently as possible. Detail designs are in progress.

For the design of the protection system of the superconducting main coils of the RIKEN superconducting ring cyclotron, the quench characteristics is calculated in terms of current decay, temperature rise, voltage development etc., using the computer program "QUENCH-M." The AC losses and pressure rise pertaining the quench are also estimated.

A six-sector superconducting ring cyclotron (SRC) is being constructed as a primary post accelerator of the existing accelerator complex for the RIKEN RI beam factory. In the SRC some superconducting magnets with high performances will be used for beam injection and extraction. Design study and R&D of them are described along with brief description of the outline of the systems.

A six-sector superconducting ring cyclotron (SRC) is being constructed as a primary post accelerator of the existing accelerator complex for the RI beam factory. Mechanical design of the main coil vessel of the SRC is described.

A new type of variable-frequency radio-frequency quadrupole (RFQ) linac has been constructed as a new preinjector for the RIKEN heavy-ion linac (RILAC). The RFQ resonator, based on a folded-coaxial structure with a movable shorting plate, is compact even in a low frequency region below 20 MHz. It accelerates ions with mass-to-charge ratios of 5.3 to 26.4 in the energy range up to 450 keV per charge, by varying its resonant frequency from 17.4 to 39.0 MHz. Moreover, the power loss is small in the low frequency region; the rf power consumption in cw mode is 7 kW at 17.4 MHz, and it increases to 30 kW at 39.0 MHz at the maximum intervane voltage of 36.8 kV. We initiated this project in 1991, and installed the new preinjector consisting of an electron cyclotron resonance ion source of 18 GHz and this RFQ in 1996. Since the installation, the beam intensity has become larger by more than 1 order of magnitude than that formerly obtained with the Cockcroft–Walton preinjector. Recently, the maximum power of the beam extracted from the RILAC and that from the ring cyclotron has reached 560 W and 2 kW, respectively.

Design, especially about the structure and quench stability, of the superconducting sector magnets for the RIKEN superconducting ring cyclotron is described. Special features of the sector magnets are the triangular shape superconducting coil, cold pole arrangement for supporting of the huge magnetic forces and the cryogenic stable coils. A full-scale superconducting model is now under construction as a prototype sector magnet.

Superconducting sector magnets are to be the main components of the superconducting ring cyclotron for the RIKEN RI beam factory. The sector magnet has superconducting main and trim coils. A cryogenic stabilization method is applied to both coils in order to make them quench-free. Both superconducting coils and their wires, design of stabilization, quench simulation, and measurement of the stabilized currents using small test coils are described.

The Variable Energy Cyclotron Centre, Calcutta is presently developing an ISOL postaccelerator-type radioactive ion beam (RIB) facility. In this method, the primary reaction products will be ionized in an on-line ECR ion source, isotopically separated to single out the product of interest and then accelerated up to an energy of . For the postacceleration we plan to use a low- heavy-ion radio frequency quadrupole (RFQ) followed by a heavy-ion IH LINAC. The RF structure and beam dynamics design of the RFQ and LINAC will be presented.

The world-top-class radioactive-isotope-beam (RIB) facility, which is called “RI beam factory (RIBF)”, is under construction at RIKEN. This facility is based on the so-called “in-flight RI beam separation” scheme. Commissioning of a new high-power heavy-ion booster system consisting of a cascade of three ring cyclotrons with K=570 MeV (fixed frequency, fRC), 980 MeV (Intermediate stage, IRC) and 2500 MeV (superconducting, SRC), respectively, is scheduled for late in 2006. This new ring-cyclotron cascade system boosts energies of the output beams from the existing K540-MeV ring cyclotron up to 440 MeV/nucleon for light ions and 350 MeV/nucleon for very heavy ions. These energetic heavy-ion beams are converted into intense RI beams via the projectile fragmentation of stable ions or in-flight fission of uranium ions by a superconducting isotope separator, BigRIPS. The combination of the SRC and the BigRIPS will expand our nuclear world into presently unreachable region. Major experimental installations are under priority discussion as the second-phase program of the RIBF project. Construction of the second phase is expected to start in 2006.

A new approach to study the high momentum component of deuteron D-state wave function by measuring the polarization correlation coefficient, C∥, for the 3 H e( d , p)4He reaction has been proposed. In order to carry out the experiment, a spin exchange type polarized 3He target was constructed at RIKEN Accelerator Research Facility (RARF). The density of the target was 2.2 × 1020 cm−3 (8.2 amagats), and the polarization was about 10%. The spin flip system worked well. The experiment has been carried out in November, 1996, at RARF, using a polarized deuteron beam of 270 MeV.

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.

Beam intensities of medium charge‐state Ar, Kr and Xe ions have been measured under the various conditions. Beam intensities were strongly dependent on the plasma electrode position and Bmin. By optimizing these parameters, 2 mA of Ar8+, 0.6 mA of Kr13+, and 0.3 mA of Xe18,20+ were obtained. We observed that the RF power of 100∼150W was enough to produce 1mA of Ar8+ form RIKEN 18 GHz ECRIS by optimizing these parameters.

In the RI beam factory project, an intermediate-stage ring cyclotron and a six-sector superconducting ring cyclotron (IRC and SRC) are designed to boost the energy of the ion beams available from the existing RIKEN ring cyclotron (RRC). The output energies designed to the SRC are 400 MeV/u for light ions such as carbon and are 150 MeV/u for heavy ions such as uranium. In the present report, we describe the recent status of design study of the injection and extraction systems for the SRC.

We have constructed the high performance ECRISs for RIKEN RI Beam factory project and successfully produced intense beams of highly charged heavy ions. RIKEN 18 GHz ECRIS can especially produce intense beams of medium charge states of heavy ions (1.3 mA of Ar8+, 200 eμA of Xe20+) by applying the various techniques, e.g., Al cylinder method, biased electrode method, optimization of the plasma electrode position. Very recently, we successfully produced intense beams of highly charged heavy ions (10 eμA of Xe30+, 1 eμA of Xe36+) from the Liquid He free SC-ECRIS with operational frequency of 14 GHz.

The RARF has a heavy‐ion accelerator complex consisting of a K540‐MeV ring cyclotron as a booster accelerator and two different types of injectors. The facility provides not only nuclear physicists but also researchers of atomic physics, nuclear chemistry, material science, radiobiology and others with various kinds of heavy‐ion beams of an energy range of 10 MeV/nucleon to 100 MeV/nucleon. One of remarkable features of this facility is capability of supplying RI (radioactive isotope) beams with the world‐highest level of intensities. In these several years the RI beam has opened up a quite new and fascinating heavy‐ion science. In order to further promote this new science, we propose ‘‘RIKEN RI Beam Factory’’ as a future project of the RARF: The existing facility will be expanded into the ‘‘Factory’’ where high‐intensity RI beams of the whole mass range will become available in a wide energy range up to several hundred MeV/nucleon. The concept of this new proposal as well as currently‐running upgrade programs relevant to the project will be presented.

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.

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 5.8MeV∕u with intensities of more than 1pμA (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 36to76.4MHz, whereas the last four are operated at a fixed frequency of 75.5MHz. The design study started in 1997 and the booster was commissioned in 2001. The total voltage gain of the booster ever achieved is 11MV, which is 70% of the designed value of 16MV. 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.

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, 1010 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 fo...