Wide Aperture Multipole Magnets of Separator COMBAS

The highresolving wide aperture separator COMBAS has been designed and commissioned at the FLNR, JINR. Its magnetooptical structure is based on strong focusing principle. The magnetic fields of analysing magnets M_1, M_2, M_7, M_8, contain quadrupole components of alternating sign that provide necessary beam focusing. Besides, all the magnets M_1M_8, contain sextupole and octupole field components, which minimizes the 2nd and 3rd order aberrations. All this allowed one to increase their apertures, to effectively form a beam of the required sizes, and to decrease the channel length. This implementation of wide aperture magnets with combined functions is unique for the separation technology. Threecomponents magnetic measurements of all the magnets were performed. The measured data allow reconstructing the 3Ddistributions of the fields in all the magnets. 3Dmaps are supposed to be used for particle trajectory simulations throughout the entire separator

The COMBAS fragment separator of radioactive nuclei and the FOBOS 4#pi#-detector for charged particles

The projectile-like fragment separator COMBAS is being designed at the Flerov Laboratory of Nuclear Reactions, JINR Dubna, for providing radioactive nuclear beams. COMBAS is a compact achromatic beam line with a high resolving power of 4360. It accepts fragments within 6.4 msr solid angle and with a momentum spread of 10%. The method of isotopic separation is based on a combination of magnetic rigidity and energy loss analysis. The separated radioactive beam is planned to be transported either into a time-projection chamber in the regime gas target - gas detector or to a secondary target positioned in the centre of the FOBOS 4#pi#-array or to another set-up. The FOBOS detector is intended for heavy ion reaction studies in the bombarding energy range of 10-100 AMeV at the cyclotron U-400M of the FLNR. Presently, only primary cyclotron beams are used because COMBAS is not yet complete. FOBOS consists of a gas-detector ball of 30 position-sensitive avalanche counters and 30 axial ionization chambers behind them and an outer scintillator shell of 210 CsI(Tl) counters surrounding the gas detectors. An array of 96 phoswich counters cover the very forward angles. All charged reaction products can be measured in a wide dynamic range and in a geometry convering a substantial part of 4#pi#. First data have been taken concerning fission and emission of intermediate-mass fragments in the reactions "7Li (43 AMeV) on "2"3"2Th and "1"4N (34 AMeV) on "1"9"7Au. (orig.)15 refs.SIGLEAvailable from TIB Hannover: RR 1847(103) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman