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Description
The ISLS (ISOLDE Superconducting Linear Spectrometer) is a by-product of the ISOLDE Superconducting Recoil Separator (ISRS) project. It integrates MAGDEM (MAGnet DEMonstrator), the fundamental building block of the ISRS particle storage ring.
MAGDEM is an extremely compact, helium-free Nb-Ti CCT superconducting magnet cooled by a single Gifford–McMahon (GM) cryocooler. It incorporates nested quadrupole and dipole functions within a single cryostat. The cryostat features a 200 mm clear aperture for the transport of heavy-ion reaction products and has an overall length of only ~750 mm. The innovative design places a 2.3 T dipole coil inside a 10 T/m quadrupole coil, providing the 36° bend required for ion analysis and storage in the ISRS ring.
The aim of the ISLS is to integrate MAGDEM into an ion-optical system for nuclear reaction studies, thereby demonstrating its performance and validating beam dynamics simulations. The system also includes a reaction chamber for both solid and gas targets, focusing elements, and focal-plane detectors. The main design goals of the ISLS are high transmission (ideally approaching 100%), a compact layout compatible with the XT03 experimental area at HIE-ISOLDE, and high mass dispersion to optimize isotope separation.
The baseline ion-optical design was developed using the codes BMAD, GICOSY, and COSY INFINITY. The beam optics were optimized in the horizontal (x–a) and vertical (y–b) phase spaces, while mass, energy, and momentum deviations (δm, δE, and δp) were treated as parameters. The required focusing condition at the final focal plane is point-to-point imaging in both transverse planes, i.e., (x,a) = (y,b) = (0,0). The proposed ISLS lattice consists of two quadrupole magnets surrounding MAGDEM in a symmetric QMQ configuration. This arrangement minimizes optical aberrations while maintaining a compact footprint and provides mass and energy dispersions of approximately 0.6 cm/% together with a momentum dispersion of approximately 1.2 cm/%.
Commissioning with both stable and radioactive ion beams is foreseen during LS3 to validate the magnet performance and benchmark the beam dynamics simulations relevant to the ISRS over a range of isotopes and beam energies. The expected performance of the ISLS will be presented for representative nuclear reactions involving light- and medium-mass isotopes of interest for nuclear astrophysics.