Resonance Ionization Laser Ion Source Research Articles

Ion-source development at the off-line LERIB test-facility at iThemba LABS

The Low Energy Radioactive Ion Beam (LERIB) facility [1] will be used to produce low-energy radioactive-ion beams (RIBs) with energies up to 60 keV. Radioactive reaction products will be created by a 66 MeV proton-beam impinging on a target made of carbide disks, such as SiC [2]. These reaction products will then be ionized in a target-ion-source (TIS) and extracted as beam. The TIS design allows three ion-sources: a surface ion-source [3], a forced electron-beam induced arc-discharge (FEBIAD) ion-source [4], and a resonance-ionization laser ion-source, or RILIS. The surface-ionization source was commissioned with stable beams in October 2021. The production of ions from Group-1 elements was accomplished with beams of 39K+, 41K+ and 23Na+ where currents were measured in the μA range. This source may be advantageous for producing stable pilot-beams for future radioactive-beam experiments. The FEBIAD is still in development at present.

First on-line application of the high-resolution spectroscopy laser ion source PI-LIST at ISOLDE

We report on the development, characterization, and first application of a specialized resonance ionization laser ion source for high-resolution spectroscopy applications below usual hot cavity Doppler broadening limitations, for on-line experiments at CERN-ISOLDE. The new PI-LIST ion source comprises perpendicular laser/atom beam interaction in a radio-frequency quadrupole unit directly downstream the hot atomizer cavity. A spectral linewidth of 200–300MHz is demonstrated, with the potential to achieve below 100MHz. Compared to standard in-source laser ionization, the efficiency reduction factor ranges from a few 100 to above 1000. The implementation of this ion source concept at thick target radioactive ion beam facilities will greatly enhance capabilities for nuclear structure investigations without demanding dedicated experimental beam line setups, and will facilitate the delivery of isomer-pure beams to experimental stations.

Laser photo-ionization study of nat Ag using opto-galvanic signal at SPES offline laser lab

Resonant Ionization Laser Ion Source (RILIS) is one of the most advancing techniques for the production of radioactive ion beams (RIBs) in ISOL facilities. SPES project at INFN-LNL is a second generation ISOL facility which aims to produce several isotopes in a couple of years. Within the framework of this project, resonant photo-ionization schemes of several elements are studied in the offline laser lab, to be later implemented in the SPES Laser Ion Source. Silver is one of the elements being studied for the stated purpose. In this article, we report a resonant photo-ionization scheme of silver tested with a hollow cathode lamp (HCL). Evidence of high lying Rydberg states around 60945.32 cm−1 has also been observed by studying the fast opto-galvanic signal detected.

Decay modes of the 9/2− isomeric state in Tl183

The internal transition decay and α decay of the T1/2=53.3ms, 9/2− isomeric state in the neutron-deficient isotope, Tl183, have been studied using the Resonance Ionization Laser Ion Source and the Windmill detection setup at the ISOLDE facility at CERN. Clean samples of Tl183m were produced by selective laser ionization and subsequent mass separation. An internal transition cascade of 356.5–272.2 keV γ rays has been identified. Multipolarities of these transitions have been determined by means of simultaneous γ-ray and conversion-electron spectroscopy. Improved data for the fine structure of the Tl183m→Au179 decay were deduced. This involves a 6058 keV α-decay transition, which populates a previously unknown state in Au179, that is tentatively assigned as a (9/2−). It is interpreted as a coupling of the 1h9/2 proton-intruder with the excited 0+ state in the Pt178 core.1 MoreReceived 11 January 2022Accepted 3 March 2022DOI:https://doi.org/10.1103/PhysRevC.105.034338Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayCollective modelsElectromagnetic transitionsEnergy levels & level densitiesIsomer decaysNuclear decayNuclear spin & parityNuclear structure & decaysRare & new isotopesShell modelProperties150 ≤ A ≤ 189Nuclear Physics

Laser-assisted nuclear decay spectroscopy of Au176,177,179

A study of the laser-ionized and mass-separated neutron-deficient isotopes Au 176 , 177 , 179 was performed using the Resonance Ionization Laser Ion Source and the Windmill detection setup at ISOLDE, CERN. New and improved data on complex fine-structure α decays of the three isotopes were deduced, providing insight into the low-lying levels in the daughter nuclei Ir 172 , 173 , 175 . New information on the properties of β -decay daughter products Pt 177 , 179 was also obtained. From the first in-source laser spectroscopy measurements of the hyperfine structure in the atomic 267.6-nm transition of Au 176 , the nuclear magnetic moments for both high- and low-spin α -decaying states were deduced. Together with the values determined from the additivity relations, they were used to propose the most probable spins and configurations for both states. The α -decay branching ratios were determined as b α ( Au ls 176 ) = 58 ( 5 ) % and b α ( Au hs 176 ) = 29 ( 5 ) % .

Polarization-dependent laser resonance ionization of beryllium

Using TRIUMF's off-line laser ion source test stand with a system of tunable titanium sapphire lasers, the polarization dependence of laser resonance ionization has been investigated using beryllium. A significant polarization dependence was observed for the excitation path 1S0 → 1P1∘ → 1S0, which are typical transitions for alkaline-earth and alkaline-earth like elements. This polarization dependence was further verified on Be radioactive isotopes at TRIUMF's isotope separator and accelerator facility (ISAC). Laser polarization was proven to be an important parameter in operating resonance ionization laser ion sources (RILIS).The polarization spectroscopy was performed off-line both on the 2p2 1S0 autoionizing (AI) state and high-n Rydberg states of the 2sns1S0 and 2snd1D2 series. The energy of the 2p2 1S0 AI state and ionization potential (IP) of beryllium were extracted as 76,167(6) cm−1 and 75,192.59(3) cm−1. Polarization spectroscopy can be used to determine the J values of newly found states in in-source spectroscopy of the complex/radioactive alkaline-earth like elements such as Ra, Sm, Yb, Pu and No.

First laser ions at the CERN-MEDICIS facility

The CERN-MEDICIS facility aims to produce emerging medical radionuclides for the theranostics approach in nuclear medicine with mass separation of ion beams. To enhance the radioisotope yield and purity of collected samples, the resonance ionization laser ion source MELISSA was constructed, and provided the first laser ions at the facility in 2019. Several operational tests were accomplished to investigate its performance in preparation for the upcoming production of terbium radioisotopes, which are of particular interest for medical applications.

RILIS laser ion source development for ISOL systems at RISP

The Resonance Ionization Laser Ion Source (RILIS) system has been developed for the future on-line laser ion source for a new heavy ion accelerator, RAON, in Korea. A tunable laser system consisting of four Ti:Sapphire lasers pumped by a Nd:YAG laser has been set up for the application in the RILIS laser ion source development in the ISOL facility of the Rare Isotope Science Project (RISP)/IBS. As a milestone of extraction of rare isotopes produced through uranium fission, double magic nucleus of 132Sn is our first target. Three step resonance ionization schemes with four laser wavelengths, at 286 nm, 301 nm, 811 nm and 823 nm, have been investigated for Sn. In this paper, we present the recent results and the current status of the hot-cavity type laser ion source development in the off-line ion source test facility of RISP, including measurements of ionization efficiency and mass resolving power.

Recent RILIS developments at the TRIUMF offline laser ion source test stand

In the search of efficient laser resonance ionization schemes and optimal source parameters, offline laser ion source development is of importance for successful online radioactive beam delivery. An overview and update on recent TRIUMF’s resonance ionization laser ion sources (TRILIS) offline developments is presented. This includes titanium-sapphire (Ti:Sa) laser development and the investigation of the laser ionization efficiency dependence on source temperature and laser polarization.

Developments towards the delivery of selenium ion beams at ISOLDE

.The production of selenium ion beams has been investigated at the CERN-ISOLDE facility via two different ionization methods. Whilst molecular selenium (SeCO) beams were produced at ISOLDE since the early 1990s, recent attempts at reliably reproducing these results have so far been unsuccessful. Here we report on tests of a step-wise resonance laser ionization scheme for atomic selenium using the ISOLDE Resonance Ionization Laser Ion Source (RILIS). For stable selenium an ionization efficiency of 1% was achieved. During the first on-line radioisotope production tests, a yield of approx 2.4 times 10^4 ions/μC was measured for 71Se+, using a ZrO2 target with an electron impact ion source. In parallel, an approach for extraction of molecular carbonyl selenide (SeCO) beams was tested. The same ion source and target material were used and a maximum yield of approx 3.6times 10^5 ions/μ C of 71SeCO+ was measured.

Resonance laser ionization spectroscopy of tellurium

Resonance ionization schemes for tellurium are investigated with a resonance ionization laser ion source and Ti:Sapphire lasers for fundamental research applications. We present the first three-step resonance ionization spectra of atomic Te. Several autoionizing Rydberg series converging to the first excited state of Te+ are observed and assigned to 5p3 (2Do3/2) ns and nd configurations. Our results include confirmation and significant expansion of the Rydberg series previously reported as well as observation of three new series. From the series convergence limits the ionization potential of tellurium is revised to be 72,669.006(42)stat(20)sys cm−1.

Lu and Pr beam development for resonance ionization laser ion sources

Resonance Ionization Laser Ion Sources (RILIS) are efficient and element selective ion sources, which are well suited for radioactive ion beam facilities. Using TRIUMF's off-line laser ion source test stand with a system of tunable titanium sapphire (Ti:Sa) lasers, laser resonance ionization schemes for lutetium (Lu) and praseodymium (Pr) have been investigated with a particular focus on autoionizing states. New ionization schemes via Rydberg states and autoionizing states were found and compared at the off-line test stand. The data from on-line RILIS delivery of Lu radioactive isotopes is presented.

Atom beam emersion from hot cavity laser ion sources

Ion sources exploiting laser resonance ionization offer efficient and element-selective radioactive ion beam production at the leading isotope separation on-line facilities worldwide. Most commonly, laser resonance ionization takes place inside a resistively heated atomizer tube directly coupled to the production target, where the element of interest is evaporated and provided as atomic vapor. While naturally the majority of atoms is ionized inside this hot cavity, a fraction of the neutrals effuses towards the high voltage beam extraction system of the subsequent mass separator.We report on several systematic investigations on this phenomenon regarding its significance and implications on the operation of resonance ionization laser ion sources. Experiments suggest a less sharply directed atom cone than expected from theoretical model, up to a lateral opening angle of 45°. Inside the tubular volume defined by the laser beam diameter around the central axis behind the source exit, more than 90% of potentially ionizable atoms are found within the first 2 cm. Geometrical constraints for the construction of devices based on ionization in the effusing atom beam directly downstream of the hot cavity are derived, and causes for cross-mass beam contamination are identified. Counter measures using laser repetition rate synchronized beam gating by fast electrostatic beam deflection to overcome these problems are presented.

MELISSA: Laser ion source setup at CERN-MEDICIS facility. Blueprint

The Resonance Ionization Laser Ion Source (RILIS) has become an essential feature of many radioactive ion beam facilities worldwide since it offers an unmatched combination of efficiency and selectivity in the production of ion beams of many different chemical elements. In 2019, the laser ion source setup MELISSA is going to be established at the CERN-MEDICIS facility, based on the experience of the workgroup LARISSA of the University Mainz and CERN ISOLDE RILIS team. The purpose is to enhance the capability of the radioactive ion beam supply for end users by optimizing the yield and the purity of the final product. In this article, the blueprint of the laser ion source, as well as the key aspects of its development and operation are presented.

New program for measuring masses of silver isotopes near the N = 82 shell closure with MLLTRAP at ALTO

The ISOL facility ALTO, located at Orsay in France, provides stable ion beams from a 15 MV Tandem accelerator and neutron-rich radioactive ion beams (RIB) from the interaction of a γ-flux induced by a 50 MeV 10 μA electron beam in a uranium carbide target. A magnetic dipole mass separator and a resonance ionization laser ion source allow to select the ions of interest. New setups are under preparation to extend the fundamental properties measured at ALTO of ground and excited states of exotic nuclei. For example, high-precision mass measurements for an accurate determination of the nuclear binding energy. To perform these measurements two devices will be hosted at ALTO: a radio frequency quadrupole to cool and bunch (RFQCB) the continuous radioactive beam and the double Penning trap mass spectrometer MLLTRAP, commissioned off-line at the Maier-Leibnitz Laboratory (MLL) in Garching, Germany. The unique production mechanism using photo-fission at the ALTO facility allows for mass measurements in a neutron rich area of nuclides of major interest around 132Sn with less isobaric contamination than using proton drivers. In this context, we plan to measure neutron-rich silver isotopes (Z = 47, A > 121) to explore the possible weakening of the shell gap for Z < 50 and its impact on the A = 130 r- process nucleosynthesis. The ground-state light silver masses (A < 121), known with a precision below 20 keV, will be used for the on-line commissioning of MLLTRAP and to characterize the performance of the detection system. The status and timeline of the novel setup is presented.

Optimization of a laser ion source for 163Ho isotope separation.

To measure the mass of the electron neutrino, the "Electron Capture in Holmium-163" (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in 163Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the 163Ho sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation using the Gibbs energy minimization method. The new setup provides an improved selectivity of laser ionization vs interfering surface ionization of 2700(500) and an overall efficiency of 41(5)% for the ion-implantation process.

In-source laser spectroscopy of dysprosium isotopes at the ISOLDE-RILIS

A number of radiogenically produced dysprosium isotopes have been studied by in-source laser spectroscopy at ISOLDE using the Resonance Ionization Laser Ion Source (RILIS). Isotope shifts were measured relative to 152Dy in the 4f106s25I8 (gs) →4f106s6p(8,1)8o (418.8nmvac) resonance transition. The electronic factor, F, and mass shift factor, M, were extracted and used for determining the changes in mean-squared charge radii for 145mDy and 147mDy for the first time.

β decay of In133 : γ emission from neutron-unbound states in Sn133

Excited states in Sn-133 were investigated through the beta decay of In-133 at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for In-133, allowing us to study separately, and in detail, the beta-decay branch of In-133 J(pi)= (9/2(+)) ground state and its J(pi) = (1/2(-)) isomer.Thanks to the large spin difference of the two beta-decaying states of In-133, it is possible to investigate separately the lower and higher spin states in the daughter, Sn-133, and thus to probe independently different single-particle and single-hole levels. We report here new gamma transitions observed in the decay of In-133, including those assigned to the deexcitation of the neutron-unbound states.

Radium ionization scheme development: The first observed autoionizing states and optical pumping effects in the hot cavity environment

This paper reports on resonance ionization scheme development for the production of exotic radium ion beams with the Resonance Ionization Laser Ion Source (RILIS) of the CERN-ISOLDE radioactive ion beam facility. During the study, autoionizing states of atomic radium were observed for the first time. Three ionization schemes were identified, originating from the 7s2 1S0 atomic ground state. The optimal of the identified ionization schemes involves five atomic transitions, four of which are induced by three resonantly tuned lasers. This is the first hot cavity RILIS ionization scheme to employ optical pumping effects. The details of the spectroscopic studies are described and the new ionization schemes are summarized.

β -delayed neutron emission from Ga85

Decay of $^{85}\mathrm{Ga}$ was studied by means of $\ensuremath{\beta}$-neutron-$\ensuremath{\gamma}$ spectroscopy. A pure beam of $^{85}\mathrm{Ga}$ was produced at the Holifield Radioactive Ion Beam Facility using a resonance ionization laser ion source and a high-resolution electromagnetic separator. The $\ensuremath{\beta}$-delayed neutron emission probability was measured for the first time, yielding 70(5)%. An upper limit of 0.1% for $\ensuremath{\beta}$-delayed two-neutron emission was also experimentally established for the first time. A detailed decay scheme including absolute $\ensuremath{\gamma}$-ray intensities was obtained. Results are compared with theoretical $\ensuremath{\beta}$-delayed emission models.