Wide aperture multipole magnets of the kinematic separator COMBAS. Basic principles of magnets design

The high-resolving large aperture kinematic separator COMBAS has been created and commissioned. The magneto-optical structure of the separator is based on the strong focusing principle. The separator consists of wide aperture magnets M1-M8. Fields of the four magnets, M1, M2, M7, M8, contain quadrupole components of alternating (from magnet to magnet) sign, which provide horizontal and vertical beam focusing. Besides, all the magnets contain higher order field components, namely, sextupole and octupole, which compensate for the 2nd and 3rd order aberrations at the intermediate and final foci. All this allowed one to decrease the total number of magnet elements (and the total channel length), increase their apertures and form effectively the beam of the required longitudinal profile and transverse sizes at both the foci. Such implementation of the large aperture combined functions magnets, having in their field distributions components up to the 3rd order, is unique in the fragment-separation technique. Basic principles of the separator and magnet design, the design and manufacturing steps are presented. Comprehensive magnetic measurements of all the magnets have been done what became the basis of the field quality analysis. Procedures to estimate the magnets field quality and to correct field errors are presented. The measured data allow building 3D-maps of the fields in all the magnets. The 3D-maps are supposed to be used for the particle trajectory simulations throughout the entire separator