Realization and simulations of the new SPES Beam Cooler

TL;DR

This paper presents the design, realization, and simulation results of a new Beam Cooler for the SPES project, aiming to improve beam quality for high-resolution isotope separation in mass spectrometry.

Contribution

It introduces a novel Beam Cooler device for SPES, with detailed simulations of beam dynamics and gas distribution, enhancing beam emittance and energy spread control.

Findings

Significant reduction in beam emittance achieved in simulations

Energy spread improvement requires further optimization

Gas pressure management is crucial for beam quality

Abstract

In order to allow a good separation of isotopes in a High Resolution Mass Spectrometer (HRMS), the transverse emittance and the energy spread of the beam should have very low values, for this reason a Beam Cooler (BC) is planned to be located between the ISOL target, i.e. the beam source, and the HRMS in the new project Selective Production of Exotic Species (SPES). In the SPES project the spectrometer resolution must be higher than dm/m=5E-5 and thus the features of the beam at the entrance of the HRMS should be at least emittance (95%, normalized) < 8.3E-3 pi mm mrad and sigma_E < 1.5eV. A new BC has been designed and realized by the Laboratoire de Physique Corpuscolaire (LPC) at Caen, France, for the SPES facility at Laboratori Nazionali di Legnaro (LNL), near Padova, Italy. BCs cool down the beam thanks to a dissipative process in which the thermal energy passes from the beam ions to another medium whose constituent is typically much lighter, Helium gas in our case. This process takes place inside a confinement system that on the one hand to limit the spread of the cooling medium, and on the other to allow the beam to continue along the required trajectory, in the presented device it is a row of radio frequency quadrupoles in an almost closed chamber. This document presents the main features of the new BC together with the results of a preliminary study where the beam dynamic has been simulated. The analysis embeds also the investigation of the gas distribution inside and outside the BC. The beam dynamic simulations are based on the Simion code while the estimation of the gas distribution is computed with MolFlow+. Simulations show that accurately setting the BC leads to a large improvement of the emittance while the energy spread still needs to be improved. Limiting the gas pressure in the acceleration zone seems to allow the required final boost.