0000000000542680
AUTHOR
Charles C Havener
Depletion of the excited state population in negative ions using laser photodetachment in a gas-filled RF quadrupole ion guide
International audience; The depopulation of excited states in beams of negatively charged carbon and silicon ions was demonstrated using collisional detachment and laser photodetachment in a radio frequency quadrupole ion guide filled with helium. The high lying, loosely bound 2 D excited state in C − was completely depleted through collisional detachment alone, which was quantitatively determined within 6%. For Si − the combined signal from the population in the 2 P and 2 D excited states was only partly depleted through collisions in the cooler. The loosely bound 2 P state was likely to be completely depopulated and the more tightly bound 2 D state was partly depopulated through collision…
Time profile of ion pulses produced in a hot-cavity laser ion source.
The time spreads of Mn ions produced by three-photon resonant ionization in a hot-cavity laser ion source are measured. A one-dimensional ion-transport model is developed to simulate the observed ion time structures. Assuming ions are generated with a Maxwellian velocity distribution and are guided by an axial electric field, the predictions of the model agree reasonably well with the experimental data and suggest that the ions are radially confined in the ion source and a substantial fraction of the ions in the transport tube are extracted.
Three-step resonant photoionization spectroscopy of Ni and Ge: ionization potential and odd-parity Rydberg levels
In preparation of a laser ion source, we have investigated multi-step laser ionization via Rydberg and autoionizing states for atomic Ni and Ge using a mass separator with an ion beam energy of 20 keV. For both elements resonant three-step excitation schemes suitable for modern Ti:sapphire laser systems were developed. Rydberg series in the range of principal quantum numbers 20 n 80 were localized, assigned and quantum numbers were allocated to the individual resonances. Ionization potentials (IP) were extracted from fits of the individual series and quantum defects of individual levels were analysed for confirmation of series assignment. For Ni the ionization potential could be extracted w…
Ion production from solid state laser ion sources.
Laser ion sources based on resonant excitation and ionization of atoms are well-established tools for selective and efficient production of radioactive ion beams. Recent developments are focused on the use of the state-of-the-art all solid-state laser systems. To date, 35 elements of the periodic table are available from laser ion sources based on tunable Ti:sapphire lasers. Recent progress in this field regarding the establishment of suitable optical excitation schemes for Ti:sapphire lasers are reported.
Laser ion source tests at the HRIBF on stable Sn, Ge and Ni isotopes
Abstract As one step in the ion source development for the Rare Isotope Accelerator, a hot-cavity laser ion source using an all-solid-state titanium–sapphire laser system has been tested at the Holifield Radioactive Ion Beam Facility. Resonance ionization of stable isotopes of Sn, Ge and Ni has been studied in a Ta hot cavity. Efficient three step resonant ionization schemes applying frequency tripling for the first excitation step and using auto-ionizing or atomic Rydberg states in the ionizing step have been identified for all three elements, resulting in laser ion beams of typically around 100 nA. By saturating most of the optical excitation steps involved, ionization efficiencies of 22%…
Resonant three-photon ionization spectroscopy of atomic Fe
Laser spectroscopic investigations on high-lying states around the ionization potential (IP) in the atomic spectrum of Fe have been carried out for the development of a practical three-step resonance ionization scheme accessible by Ti: sapphire lasers. A hot cavity laser ion source, typically used at on-line radioactive ion beam production facilities, was employed in this work. Ionization schemes employing high-lying Rydberg and autoionizing states populated by three-photon excitations were established. Five new Rydberg and autoionizing Rydberg series converging to the ground and to the first four excited states of Fe II are reported. Analyses of the Rydberg series yield the value 63 737.68…
Optical spectroscopy and performance tests with a solid state laser ion source at HRIBF
An ISOLDE-type hot-cavity laser ion source based on high-repetition-rate Ti:Sapphire lasers has been set up at the Holifield radioactive ion beam facility. To assess the feasibility of the all-solid-state laser system for applications at advanced radioactive ion beam facilities, spectroscopy and performance tests have been conducted with this source. The results of recent studies on excitation schemes, source efficiency, beam emittance and ion time structure are presented.
Time profiles of ions produced in a hot-cavity resonant ionization laser ion source
Abstract The time profiles of Cu, Sn, and Ni ions extracted from a hot-cavity resonant ionization laser ion source are investigated. The ions are produced in the ion source by three-photon resonant ionization with pulsed Ti:Sapphire lasers. Measurements show that the time spread of these ions generated within laser pulses of about 30 ns duration could be larger than 100 μs when the ions are extracted from the ion source. A one-dimensional ion-transport model using the Monte Carlo method is developed to simulate the time dependence of the ion pulses. The prediction of the model agrees reasonably well with the experimental data. To reproduce the observed ion time profiles, we find it necessar…