Model Coupled Accelerator Tuning

Abstract

Relativistic charged particle optics in the context of accelerator physics have been treated using transfer matrix methods since the 1950s. The realization that a hyperellipsoidal charged particle distribution could likewise be transformed if its 6-dimensional covariance matrix was used, with diagonal elements as the squared sizes, allowed for a computationally efficient and generalizable means to perform beam optics studies and analysis. Initially confined to elements with constant focal strengths, representable as square functions along the reference orbit and limited to constant energy beamline sections, such methods have not been applied to accelerated beam envelopes. Instead, the latter have to date been reserved for multiparticle simulations, more computationally taxing. The envelope code TRANSOPTR, developed at Chalk River Nuclear Laboratories in the late 1970s, added to the repertoire of envelope simulation capabilities by using a quadraticized Hamiltonian about a Frenet-Serret reference particle frame, for numerical integration of beam envelopes subject to scalar and vector potentials, including time-dependency. In this work, the beam-envelope simulation capabilities of TRANSOPTR are extended to include rf quadrupole accelerators and applied to include drift tube linear accelerators, enabling a full envelope model of the ISAC-I linac, leading to the identification of a long standing issue with its design tune. A corrective tuning prescription is elaborated for the ISAC-DTL. The novel tuning method significantly reduces accelerator operation complexity and therefore overhead time, by coupling machine tuning to parallel, beam diagnostic fed simulations. The generalizibility of the MCAT approach and speed of TRANSOPTR produce a suitable candidate for site-wide roll-out as the standard feedback driven accelerator tuning control software.