To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually ...opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.
A saturated absorption spectroscopy setup was developed and optimised for the characterisation of a home-built and a commercial Fabry-Pérot interferometer (FPI). The free spectral range of these FPIs ...has been determined with reliable statistical and systematic errors. These FPIs will be used for accurate wavelength determination of broad- and narrowband pulsed Ti:sapphire lasers used in resonance ionisation spectroscopy experiments.
The FURIOS laser ion source at IGISOL-4 Reponen, M.; Moore, I.D.; Pohjalainen, I. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317
Journal Article
Recenzirano
•The commissioning of the FURIOS laser ion source at IGISOL-4.•Laser ionization of silver.•Investigations of the dual-chamber gas cell with an alpha-recoil source.•Resonance ionization spectroscopy ...of copper.
The FURIOS laser ion source at the Accelerator Laboratory of the University of Jyväskylä has been moved to a new location as a part of the IGISOL-4 facility. The laser ion source project had a high priority which allowed the transport of laser light to be optimized during the design phase. The laser resonators have been upgraded with a dual etalon configuration leading to greatly reduced laser linewidth. The transport efficiency of the dual-chamber gas cell has been determined using an alpha recoil source, with efficiencies ranging from a few percent in the beam interaction chamber to nearly 20% in the ionization chamber. In addition, we present recent results from the re-commissioning of the laser system on stable copper isotopes.
A compact electrostatic trap has been designed and installed as part of the recent upgrades to the IGISOL IV facility. The ConeTrap provides an in vacuo optical pumping site for low energy (800 eV) ...ionic ensembles available for interaction periods of 10-100 ms. At present, 6.7(3) % of injected mass A=98 ions can be trapped, stored for 5 ms, extracted and transported to a laser-ion interaction region. This fraction represents those ions for which no perturbation to total energy or energy spread is observed. Proposed enhancements to the trap are designed to improve the trapping efficiency by up to a factor of 5. Differential pumping and reduction in background pressure below the present 10
−6
mbar will extend storage times beyond 100 ms.
Gas jet studies towards an optimization of the IGISOL LIST method Reponen, M.; Moore, I.D.; Pohjalainen, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2011, Letnik:
635, Številka:
1
Journal Article
Recenzirano
Gas jets emitted from an ion guide have been studied as a function of nozzle type and gas cell-to-background pressure ratio in order to obtain a low divergent, uniform jet over a distance of several ...cm. The jet has been probed by imaging the light emitted from excited argon or helium gas atoms. For a simple exit hole or converging-diverging nozzle, the jet diameter was found to be insensitive to the nozzle shape and inlet pressure. Sonic jets with a FWHM below 6
mm were achieved with a background pressure larger than 1
mbar in the expansion chamber. The measurements are supported by the detection of radioactive
219
Rn
recoils from an alpha recoil source mounted within the gas cell. A Laval nozzle produced a well-collimated supersonic jet at low background pressures with a FWHM of
∼
6
mm
over a distance of 14
cm. Direct Pitot probe measurements, on-axis, revealed a non-uniform pressure distribution in the gas jet of the Laval nozzle, supporting the visual observations. All measurements are motivated by the requirement of a good geometrical overlap between atoms and counter-propagating laser beams in the gas cell-based Laser Ion Source Trap (LIST) project. Computational fluid dynamics gas flow simulations were initiated to guide the future development of the gas jet system.
Abstract
An in-flight separator performs the important role of separating a single specific radioactive isotope (RI) beam from the thousands of RI beams produced by in-flight fission as well as ...projectile fragmentation. However, when looking at ``separation'' from a different viewpoint, more than 99% of simultaneously produced RI beams are just eliminated in the focal plane slits or elsewhere in the separator. In order to enhance the effective usability of the RIKEN in-flight separator BigRIPS, we have been developing an innovative method: parasitic laser ion source (PALIS), which implements parasitic low-energy RI beam production by saving eliminated RI beams during BigRIPS experiments. In this paper, we present the expected benefits and feasibility for the PALIS concept and the results of the first stopping examination for high-energy RI beams in the gas cell.
Three observables of interest for present and future reactors depend on the
β
decay properties of the fission products: antineutrinos from reactors, the reactor decay heat and delayed neutron ...emission. In these proceedings, we present new results from summation calculations of the first two quantities quoted above, performed with evolved independent yields coupled with fission product decay data, from various nuclear data bases or models. New TAGS results from the latest experiment of the TAGS collaboration at the JYFL facility of Jyväskylä will be displayed as well as their impact on the antineutrino spectra and the decay heat associated to fission pulses of the main actinides.
The search for the existence of 229mTh at IGISOL Sonnenschein, V.; Moore, I. D.; Raeder, S. ...
The European physical journal. A, Hadrons and nuclei,
04/2012, Letnik:
48, Številka:
4
Journal Article
Recenzirano
An overview of preparatory work aiming at the identification of the low-lying 7.6 eV isomer in
229
Th through a measurement of its hyperfine structure is presented. A
233
U recoil gas cell has been ...developed and has undergone several iterations in order to improve the efficiency of extracting a low-energy beam of
229
Th
+
ions. Spectroscopic studies on stable
232
Th have been carried out to establish an efficient laser ionization scheme. The latter will be applied in connection with the gas cell in order to improve the extraction efficiency by accessing the neutral atomic fraction. In addition to that of the
229
Th ground state, the hyperfine structure of the isomer can then be determined either by collinear laser spectroscopy on the extracted and accelerated ions or by direct in-source/in-jet high-resolution Resonance Ionization Spectroscopy (RIS). The first experiments using high-resolution RIS have been performed and isotope shifts of
228
Th,
229
Th and
230
Th relative to
232
Th were measured on an atomic 7
s
2
→ 7
s
7
p
ground-state transition at 380.42 nm. A template of the ground-state hyperfine structure of
229
Th has been established for a 261.24 nm UV transition. This is an important step towards identification of the isomeric state.
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