Status of the SPIRAL2 injector commissioning.

The SPIRAL2 injector, installed in its tunnel, is currently under commissioning at GANIL, Caen, France. The injector is composed of two low energy beam transport lines: one is dedicated to the light ion beam production, the other to the heavy ions. The first light ion beam, created by a 2.45 GHz electron cyclotron resonance ion source, has been successfully produced in December 2014. The first beam of the PHOENIX V2 18 GHz heavy ion source was analyzed on 10 July 2015. A status of the SPIRAL2 injector commissioning is given. An upgrade of the heavy ion source, named PHOENIX V3 aimed to replace the V2, is presented. The new version features a doubled plasma chamber volume and the high charge state beam intensity is expected to increase by a factor of 1.5 to 2 up to the mass ∼50. A status of its assembly is proposed.

Light ion source for proton∕deuteron production at CEA Saclay for the Spiral2 project.

The production of rare radioactive ion beam (RIB) far from the valley of stability is one of the final purposes of the Spiral2 facility in Caen. The RIB will be produced by impinging a deuteron beam onto a carbon sample to produce a high neutron flux, which will interact with a uranium target. The primary deuteron beam is produced by an ion source based on ECR plasma generation. The deuteron source and the low energy beam transport (LEBT) has been assembled and tested at CEA Saclay. Diagnostics from other laboratories were implemented on the LEBT in order to characterize the deuteron beam produced and compare it to the initial simulations. The ion source has been based on a SILHI-type source, which has demonstrated good performances in pulsed and continuous mode, and also a very good reliability on long term operation. The 5 mA of deuteron beam required at the RFQ entrance is extracted from the plasma source at the energy of 40 kV. After a brief description of the experimental set-up, this article reports on the first beam characterization experiments.

Transport of intense ion beams and space charge compensation issues in low energy beam lines (invited).

Over the last few years, the interest of the international scientific community for high power accelerators in the megawatt range has been increasing. For such machines, the ion source has to deliver a beam intensity that ranges from several tens up to a hundred of mA. One of the major challenges is to extract and transport the beam while minimizing the emittance growth and optimizing its injection into the radio frequency quadrupole. Consequently, it is crucial to perform precise simulations and cautious design of the low energy beam transport (LEBT) line. In particular, the beam dynamics calculations have to take into account not only the space charge effects but also the space charge compensation of the beam induced by ionization of the residual gas. The physical phenomena occurring in a high intensity LEBT and their possible effects on the beam are presented, with a particular emphasis on space charge compensation. Then, beam transport issues in different kind of LEBTs are briefly reviewed. The SOLMAXP particle-in-cell code dedicated to the modeling of the transport of charge particles under a space charge compensation regime is described. Finally, beam dynamics simulations results obtained with SOLMAXP are presented in the case of international fusion materials irradiation facility injector.

Experimental evidence of the 90 degrees stop band in the GSI UNILAC.

In a particle accelerator with a periodic structure beam space charge force may excite resonant beam emittance growth if the particle's transverse phase advance approaches 90 degrees . A recent simulation study with the PARMILA code [D. Jeon, Phys. Rev. ST Accel. Beams 12, 054204 (2009)]10.1103/PhysRevSTAB.12.054204 has shown the feasibility of measuring the stop band of this fourth order resonance in the GSI Universal Linear Accelerator UNILAC and proposed its experimental verification, which is reported here. Measurements of transverse phase space distributions behind a periodically focusing structure reveal a fourfold symmetry characteristic of fourth order resonances as well as a resonance stop band above sigma_{0}=90 degrees per focusing cell. These experimental findings agree with results from three different beam dynamics simulation codes, i.e., DYNAMION, PARMILA, and TRACEWIN.

Experimental evidence of space charge driven emittance coupling in high intensity linear accelerators.

In high intensity linacs emittance exchange driven by space charge coupling may lead to the well-known "equipartitioning" phenomenon if the stop band at sigma(parallel) = sigma(perpendicular) is crossed at sufficiently slow rate. This Letter is the first experimental evidence of this phenomenon in a high intensity linear accelerator, here the UNILAC at GSI. Measurements of emittances at the entrance and exit of one drift tube linac tank comprising 15 lattice cells are taken for a set of transverse and longitudinal tunes. The onset of exchange on the stop band of previously derived "stability charts" confirms theoretical predictions. The measured transverse emittance growth also compares well with results from the beam dynamics simulation codes DYNAMION and TRACEWIN.