Development of a resonant laser ionization gas cell for high-energy, 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.

An ion guide laser ion source for isobar-suppressed rare isotope beams

“…It is used or foreseen at many ISOL facilities such as ISOLDE, 11 ISAC, 12 HRIBF, 13 IRIS, 14 ALTO, 10 SPIRAL, 15 SPES 16 as well as at on-line facilities with a gas cell stopper such as IGISOL, 17 LISOL, 18 and SLOWRI. 19 Although resonant laser ionization increases the yield of a desired element, the problem of surface-ionized background remains. To approach this proba) Electronic mail: sebastian.raeder@fys.kuleuven.be.…”

Proposal of a New Double-Nozzle Technique for In-Gas-Jet Laser Resonance Ionization Spectroscopy

“…Near the extraction nozzle having the small throat diameter, ions are extracted out of the gas cell into vacuum conditions by supersonic buffer gas jet. Description of various gas cell apparatus readers can find elsewhere, for example, in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and links within them.…”

“…The extraction of the ions into high vacuum is finally performed with the use of radiofrequency quadrupoles (RFQ) [7, 8, 11 and 20-26] or radio-frequency sextupoles (SPIG) [9,15] installed downstream for the ion beam transportation and focusing. Instead of traditional RFQ and SPIG rod-structures, a simple, compact and effective gas dynamic RF-only funnels can be used, as well.…”

Resonant three-photon ionization spectroscopy of atomic Fe

“…To provide RIBs of Fe isotopes with this RILIS, suitable ionization schemes have to be developed. Although multiphoton resonant ionization of Fe by dye lasers has been previously reported [16][17][18][19][20][21], the ionization schemes used for dye lasers are not suitable for the Ti:sapphire lasers. For example, a two-step scheme for dye lasers has been used to produce beams of neutron-rich 65,67 Fe isotopes [16].…”

“…Although multiphoton resonant ionization of Fe by dye lasers has been previously reported [16][17][18][19][20][21], the ionization schemes used for dye lasers are not suitable for the Ti:sapphire lasers. For example, a two-step scheme for dye lasers has been used to produce beams of neutron-rich 65,67 Fe isotopes [16]. It uses photons of 229.887 nm for the first excitation and 493.8 nm for the second excitation.…”