Beam optics design studies of the ISNS high energy beam transport line

Accelerator physics design study of the proposed Indian Spallation Neutron Source (ISNS) is in progress at RRCAT. The proposed configuration consists of a 1 GeV superconducting H^- linac, followed by a 1 GeV proton accumulator ring (AR) and the required beam transport lines. High energy beam transport (HEBT) line connects the linac to the AR. On the basis of functions, HEBT line is divided into three sections. Various design objectives e.g., the betatron phase advances between transverse halo scrapers, the achromatic conditions in arc and dogleg, and the beam twiss parameters matching are achieved using the SIMplex and Simulated Annealing (SIMSA) algorithm. While selecting a lattice, it is ensured that the beta functions are smooth; dispersion (D_x) is sufficiently high for momentum collimation, and the size of dipole magnets are within the fabrication capability. Since the outermost electron is loosely bound in H^- ion, design of the HEBT line is performed with various constraints to ensure beam loss < 1 W/m. In this paper, details of the lattice design of HEBT line, along with the specifications of its components are given. (author)