DESIR is, together with S3-LEB, the low-energy part of the SPIRAL2 ISOL facility at GANIL. The High-Resolution mass Separator (HRS) included in DESIR is a 180° symmetric online separator with two 90° magnetic dipole sections arranged with electrostatic quadrupoles, sextupoles and a 48-pole electrostatic multipole on the mid plane. The HRS is now completely mounted at LP2i Bordeaux and under commissioning for the next years before its transfer to the entrance of the DESIR facility. Optical aberrations, mainly introduced by the dipoles, must be corrected up to the highest possible order to guarantee an optimal resolution of the separator. They are measured with a pepperpot-type emittance-meter, analyzed then corrected with the multipole. Up to now, 2nd order (hexapolar) and part of 3rd order (octupolar) aberrations are under control and an optimal FWHM separation has been achieved for two identical beams with a relative energy difference of ΔE/E(≡ΔM/M)=1/23400. In this paper, we present the effects of optical aberrations on the beam and its emittance figure, as well as the effect of the associated corrections with the multipole. Finally, we will show the latest resolution measurements and associated methodology. 

Commissioning of the DESIR high-resolution mass separator

We report on the conception and first tests of the General Purpose Ion Buncher (GPIB), the radio-frequency beam-cooler and buncher that will supply the DESIR (Decay, Excitation and Storage of Radioactive Ions) experimental hall to be constructed to complement the SPIRAL1 and SPIRAL2 facilities in GANIL. Its goals are both to reduce the emittance and if necessary to bunch the radioactive ion beam from the GANIL production facilities to adapt it to the needs of the different experimental setups in the DESIR hall. The mechanical design is similar to the existing ISCOOL quadrupole at ISOLDE but the new radio-frequency system enables a much stronger radial confinement. The GPIB is developed at LP2i Bordeaux1 in parallel with the PIPERADE double Penning trap and a beamline has been constructed there to characterize both. The cooling of a 30 keV beam to an emittance of 3 π mm mrad and a transmission above 80% in continuous mode is demonstrated for currents up to a few nA. Some first results concerning the bunching mode are also shown though this mode is still under development. 

/pdf/the-general-purpose-ion-buncher-a-radiofrequency-quadrupole-2ot3xaaw.pdf

The general purpose ion buncher: A radiofrequency quadrupole cooler-buncher for DESIR at SPIRAL2

A double Penning trap is being commissioned at CENBG Bordeaux for the future DESIR/SPIRAL2 facility of GANIL. The setup is designed to perform both high-resolution mass separation of the ion beam for trap-assisted spectroscopy, and high-accuracy mass spectrometry of short-lived nuclides. In this paper, the technical details of the new device are described. First offline tests with the purification trap are also presented, showing a mass resolving power of about 10 5 .

E. Minaya Ramirez

Papers

PIPERADE: A double Penning trap for mass separation and mass spectrometry at DESIR/SPIRAL2