RIKEN, Wako, Saitama
In 2008, the RIKEN RI-Beam Factory (RIBF) succeeded in providing heavy ion beams of 48Ca and 238U with 170 particle-nano-ampere and 0.4 particle-nano-ampere, respectively, at an energy of 345 MeV/u. The transmission efficiency through the accelerator chain has been signifcantly improved owing to the continuous efforts paid since the first beam in 2006. From the operational point of view, however, the intensity of the uranium beam should be much increased. We have, therefore, constructed a superconducting ECR ion source which is capable of the microwave power of 28 GHz. In order to reduce the space-charge effects, the ion source was installed on the high-voltage terminal of the Cockcroft-Walton pre-injector, where the beam from the source will be directly injected into the heavy-ion linac by skipping the RFQ pre-injector. The test of the ion source on the platform has started recently with an existing microwave source of 18 GHz. This pre-injector will be available in October 2009. We will show further upgrade plan of constructing an alternative injector for the RIBF, consisting of the superconducting ECR ion source, an RFQ, and three DTL tanks. An RFQ linac, which has been originally developed for the ion-implantation application will be reused for the new injector. Modification of the RFQ as well as the design study of the DTL are under progress. The new injector, which will be ready in FY2010, aims at independent operation of the RIBF experiments and super-heavy element synthesis.
LBNL, Berkeley
Notre Dame University, Notre Dame
Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The DIANA project (Dakota Ion Accelerators for Nuclear Astrophysics) is a collaboration between the University of Notre Dame, University of North Carolina, Western Michigan University, and Lawrence Berkeley National Laboratory to build a nuclear astrophysics accelerator facility 1.4 km below ground. DIANA is part of the US proposal DUSEL (Deep Underground Science and Engineering Laboratory) to establish a crossdisciplinary underground laboratory in the former gold mine of Homestake in South Dakota, USA. DIANA would consist of two high-current accelerators, a 30 to 400 kV variable, high-voltage platform, and a second, dynamitron accelerator with a voltage range of 350 kV to 3 MV. As a unique feature, both accelerators are planned to be equipped with either high-current microwave ion sources or multi-charged ECR ion sources producing ions from protons to oxygen. Electrostatic quadrupole transport elements will be incorporated in the dynamitron high voltage column. Compared to current astrophysics facilities, DIANA could increase the available beam densities on target by magnitudes: up to 100 mA on the low energy accelerator and several mA on the high energy accelerator. An integral part of the DIANA project is the development of a high-density super-sonic gas-jet target which can handle these anticipated beam powers. The paper will explain the main components of the DIANA accelerators and their beam transport lines and will discuss related technical challenges.
JINR/FLNR, Dubna
Four heavy ions cyclotrons are in operation at FLNR now. Heavy ion beams used for super heavy elements synthesis, RIB production and application. Plan for seven years accelerator development and operation are presented.
CNRS-IN2P3/LPSC, Grenoble
The basic principles of the ECR charge state breeder (CSB) are recalled, special attention is paid to the critical parameters allowing the optimization of the ECR charge breeders characteristics (efficiency yield, charge breeding time, capture potential deltaV). An overview is given on the present ECR charge breeders situation and results worldwide. Possible means to increase the 1+ ion beam capture for light ions is presented. In the context of radioactive environment, possible technological improvements and/or simplifications are suggested to facilitate the maintenance and to reduce the human intervention time in case of a subsystem failure.
ANL, Argonne
Funding: Work supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The construction of the Californium Rare Ion Breeder Upgrade (CARIBU), a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS), is nearing completion. The facility will use fission fragments from a 1 Ci 252Cf source; thermalized and collected into a low-energy particle beam by a helium gas catcher. In order to reaccelerate these beams, the existing ATLAS ECR1 ion source was redesigned to function as an ECR charge breeder. The helium gas catcher system and the charge breeder are located on separate high voltage platforms. An additional high voltage platform was constructed to accommodate a low charge state stable beam source for charge breeding development work. Thus far the charge breeder has been tested with stable beams of rubidium and cesium achieving charge breeding efficiencies of 5.2% into 85Rb17+ and 2.9% into 133Cs20+.
LBNL, Berkeley
Funding: This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract DE AC03-76SF00098.
The development of the superconducting 28 GHz ECR ion source VENUS at the Lawrence Berkeley National Laboratory (LBNL) has pioneered high field superconducting ECR ion sources and opened a path to a new generation of heavy ion accelerators. Because of the success of the VENUS ECR ion source, superconducting 28 GHz ECR ion sources are now key components for proposed radioactive ion beam facilities. This paper will review the recent ion source development program for the VENUS source with a particular focus on the production of high intensity uranium beams. In addition, the paper will discuss a new R&D program started at LBNL to develop ECR ion sources utilizing frequencies higher than 28 GHz. This program addresses the demand for further increases of ion beam intensities for future radioactive ion beam facilities. The most critical technical development required for this new generation of sources is the high-field superconducting magnet system. For instance, the magnetic field strengths necessary for 56 GHz operation produce a peak field in the magnet coils of 12-14 T, requiring new superconductor material such as Nb3Sn. LBNL has recently concluded a conceptual, comparative design analysis of different coil configurations in terms of magnetic performance and has developed a structural support concept compatible with the preferred magnetic design solution. This design effort concludes that a sextupole-in-solenoid ECR magnet structure (VENUS type) is feasible with present Nb3Sn technology, but that an inverted geometry (solenoid-in sextupole) exceeds the capability of Nb3Sn superconductors and can be ruled out as candidate for a 56 GHz ECR ion source.
Goethe Universität Frankfurt/IAP, Frankfurt
MSU/NSCL, East Lansing
ECR and EBIS have become well-known ion sources for most heavy ion accelerator projects. The basic difference arises from the method, how energy is provided to create dense energetic electrons: An ECR uses microwave heating of a magnetically confined plasma, while in an EBIS the energy comes from a power supply to accelerate an electron beam and focus it to high density in a strong solenoidal magnetic field. Basically ECR sources are dc sources of heavy ions but the afterglow extraction also provides intense mA pulses in ms. In contrast to this EBIS sources provide an intense ion pulse in 1-100 μs and therefore find application in feeding synchrotrons. This determines most of the accelerator applications: ECR sources have very successfully extended the range (and life) of cyclotrons, while EBIS has found application at high energy facilities. For radioactive beam facilities, both kind of sources are in use. ECR sources in the trapping mode (ECRIT) perform the ionization (charge breeding) of high intensity primary beams, while EBIS can reach higher charge states at lower emittance, which provides an improved signal to noise ratio for rare isotopes.
INFN/LNL, Legnaro
PIAVE-ALPI is the INFN-LNL superconducting heavy ion linac, composed by an SRFQ (superconducting RFQ) section and three QWR sections for a total of 80 cavities installed and an equivalent voltage exceeding 70 MV. In the last years the SRFQ and the bulk niobium QWR came into routine operation, the medium energy QWR section was upgraded with a new Nb sputtered coating, ECR source was firstly improved by using water cooled plasma chamber and then replaced with a new one. The operation of the accelerator complex allowed acquiring a strong experience on many operational issues related to ECRIS, superconducting cavities and cryogenics, beam control and manipulation (with the new and higher accelerating gradient). The paper reports about operational experience, the present limitations and the future perspectives of the facility in view of the experimental campaign with the EU detector AGATA and of the use of PIAVE ALPI as RIB post-accelerator for SPES radioactive ion beam facility.
Osaka Univ., Suita
An electron cyclotron resonance ion source (ECRIS) has been developing long time and their performance is still extending at present. Recently, they are not only used in producing multi-charged ions, but also molecules and cluster ions. A new type of ion source with a wide operation window is expected for various uses. We developed a novel magnetic field configuration ECRIS. The magnetic field configuration is constructed by a pair of comb-shaped magnetic field by all permanent magnets and has opposite polarity each other with ring-magnets. This magnetic configuration suppresses the loss due to E×B drift, and then plasma confinement is enhanced. We conduct preliminary extracting and forming large bore ion beam from this source. We will make this source a part of tandem type ion source for the first stage. Broad ion beams extracted from the first stage and transfer like a shower to plasma generated by the second stage. We hope to realize a device which has a very wide range operation window in a single device to produce many kinds of ion beams. We try to control plasma parameters by multiply frequency microwaves for broad ion beam extraction. It is found that plasma and beam can be controllable on spatial profiles beyond wide operation window of plasma parameters. We investigated feasibility of the device which has wide range operation window in a single device to produce many kinds of ion beams as like universal source based on ECRIS.