CHARGE STRIPPERS FOR ACCELERATION OF URANIUM BEAM AT RIKEN RI-BEAM FACTORY

A uranium beam was accelerated to 345 MeV/nucleon using two or three stages of charge strippers at the RIKEN RI-beam factory. The dependence of the charge state dis- tribution of uranium on the carbon foil thickness was mea- sured at 0.67, 0.87, 11, and 51 MeV/nucleon. Rotating charge strippers were constructed to strip high-intensity beams. the RIKEN heavy-ion linac (RILAC), the RIKEN ring cy- clotron (RRC), a fixed-frequency ring cyclotron (fRC), an intermediate-stage ring cyclotron (IRC), and a supercon- ducting ring cyclotron (SRC). The latter three ring cy- clotrons, the fRC, the IRC, and the SRC, are newly con- structed. The three stripper sections are placed downstrea m of the first three accelerators, the RILAC, the RRC, and the fRC. The beam energies incident on the strippers are 0.67, 11, and 51 MeV/nucleon, respectively. A uranium beam was accelerated to 345 MeV/nucleon using two or three charge strippers. The design process of the newly constructed ring cyclotrons required the charge state distribution and equilibrium thickness of the charge strippers. However, we could not obtain sufficient data, particularly on the third stripper placed between the fRC and the IRC. Thus, the charge state distribution and the equilibrium thickness were estimated by calculations (3, 4). The validity of the calculations was checked by comparison with the measured charge state distributions of ions lighte r than uranium at the same energy region. The GLOBAL calculation (3) accurately reproduced the charge state dis - tributions of Kr and Xe at equilibrium (2). In this paper, the charge state distributions of uranium measured at 0.67, 0.87, 11, and 51 MeV/nucleon are presented, and the struc- ture of one of the two rotating strippers is described.