Abstract
Within the framework of the DESIR/SPIRAL-2 project, a radio-frequency quadrupole cooler named SHIRaC has been studied. SHIRaC is a key device of SPIRAL-2, designed to enhance the beam quality required by DESIR. The preliminary study and development of this device has been carried out at Laboratoire de Physique Corpusculaire de CAEN (LPC Caen), France. The goal of this paper is to present the experimental studies conducted on a SHIRaC prototype. The main peculiarity of this cooler is its efficient handling and cooling of ion beams with currents going up as high as $1\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$ which has never before been achieved in any of the previous coolers. Much effort has been made lately into these studies for development of appropriate optics, vacuum and rf systems which allow cooling of beams of large emittance ($\ensuremath{\sim}80\ensuremath{\pi}\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$) and high current. The dependencies of SHIRaC's transmission and the cooled beam parameters in terms of geometrical transverse emittance and the longitudinal energy spread have also been discussed. Investigation of beam purity at optimum cooling condition has also been done. Results from the experiments indicate that an emittance reduction of less than $2.5\ensuremath{\pi}\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ and a longitudinal energy spread reduction of less than 4 eV are obtained with more than 70% of ion transmission. The emittance is at expected values whereas the energy spread is not.
Highlights
In the context of generation of newly developed nuclear facilities based on the ISOL method [1] for the production of rare and exotic ion beams with intensities up to 1 μA and emittances up to 80π mm mrad [2], the SPIRAL-2 project is being installed at GANIL laboratory in France [3,4,5]
A sketch of the experimental line is shown in Fig. 6; the radio-frequency quadrupole (RFQ) chamber is preceded with the injection part connecting it to an ionization surface source
At the optimum cooling conditions of 1 μA beam, the simulation results are of 67% of transmission, 2.5π mm mrad of emittance and 5.9 eV of energy spread and their respective experimental results are of 70% (2.3 Æ 0.7π mm mrad) and (6.5 Æ 0.7 eV). Before building this Spiral-2 High Intensity Radiofrequency Cooler (SHIRaC) prototype, the main challenge was to overcome the space charge stemming from the high beam currents
Summary
In the context of generation of newly developed nuclear facilities based on the ISOL method [1] for the production of rare and exotic ion beams with intensities up to 1 μA and emittances up to 80π mm mrad [2], the SPIRAL-2 project is being installed at GANIL laboratory in France [3,4,5]. There are several instruments which are operating at the world’s radioactive beam installations and are capable of providing low beam emittances with good efficiency. For this purpose, a radio-frequency quadrupole cooler (RFQC) should be installed in front of the HRS.
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