Optimization of Beam Transmission in the extraction lines of the K130 Room Temperature Cyclotron at Variable Energy Cyclotron Centre (VECC), Kolkata

Abstract

The K130 Room Temperature Cyclotron (RTC) at the Variable Energy Cyclotron Centre (VECC), Kolkata has delivered a variety of ion beams for experimental programs with stable performance since the 1970s. The extracted beams are transported to experimental stations through four beamlines. In this work, a two-step semi-numerical optimization framework is presented to improve the transmission efficiency of these transport lines. At its core, the method relies on multiparticle simulations to account for beam losses and nonlinear effects, which render the problem analytically intractable. To address these complexities, a derivative-free global optimization framework is developed to systematically improve beam transmission in the cyclotron beamlines, and its effectiveness is demonstrated experimentally. In the first phase, the beam parameters at the beamline entrance are estimated using Bayesian optimization constrained by experimentally measured transmission ratios for selected optics configurations. In the second phase, the quadrupole gradients are optimized using the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) to maximize beam transmission. Optimized settings computed using this simulation based semi numerical methodology were then experimentally validated, achieving beam transmissions exceeding 70%.