onstruction and performance test of the drift chambers at the target area of the External Target

he multiwire drift chambers at the target area of the External Target Facility of CSR are constructed for tracking radioactive ion beams that enter and exit the target. Two drift chambers with a sensitive area of 8 × 8 cm² are positioned upstream of the target, while another two drift chambers with a sensitive area of 16 × 16 cm² are placed upstream of the target. The drift chambers were tested using 350 MeV/u ⁷⁸Kr beams and cocktail secondary beams. To improve drift time precision, the time walk effect is corrected by using the measured energy. The impact of δ-rays on the multiplicity and spatial resolution is assessed using beams with various atomic number and different applied voltages. The optimal voltage to minimize the impact of δ-rays is obtained. An optimal spatial resolution of 35 μm for the drift chambers is achieved.