Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei

TL;DR

This paper presents a novel resonant laser ionization gas cell system designed for efficient production and extraction of short-lived nuclei at high energies, featuring innovative differential pumping and ion transport mechanisms.

Contribution

It introduces a compact, high-pressure gas cell with differential pumping and a sextupole ion guide, enabling rapid extraction of short-lived nuclei for the first time.

Findings

Successful demonstration of fast evacuation minimizing decay loss

Agreement between observed behavior and simulations

Enhanced efficiency in extracting short-lived nuclei

Abstract

A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN's fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa - 10^-3 Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by a quadrupole mass separator. Observed behaviors agree with the results of gas flow and Monte Carlo simulations.