Particle Swarm Optimization of High Rigidity Spectrometer*

We conduct research on two coupled ion optics systems, the High Transmission Beam Line (HTBL) and the High Rigidity Spectrometer (HRS) at the Facility for Rare Isotope Beams (FRIB). Beams from FRIB are directed into the HTBL to measure the energy and velocity and transmit them to the reaction target at the end. The products are then separated and characterized in the HRS. We simulate them using an ion optical simulation COSY INFINITY.

To maximize the momentum resolving power of the HRS, we need to shrink the size of the beam spot at the end of the HTBL. We also need to maximize the transmission rate of both systems.

In this project, we use Particle Swarm Optimization (PSO) to optimize both systems in higher order. PSO is a global optimization algorithm specializing in high-dimensional problems. It has two internal parameters: inertia a and acceleration b. A good optimizer must have good final results in repeated tests. The goal of this project is to find the most reliable combination (a,b) of the PSO for HTBL and HRS.

So far we have identified combinations (0.85, 0.4) and (0.8, 0.45) that provided significantly more reliable results for HRS. They also performed well for HTBL in early tests. We will explore more in the parameter space and report the testing results for both systems.