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Introduction
Over the past decade, a small set of laboratories have been working on the development of resonance ionization mass spectrometry (RIMS) instruments for the purpose of element-selective isotope analysis without prior chemical separation. From hot particle forensics to cosmochemistry, RIMS has unlocked unique research opportunities for element-selective microanalysis.
Each instrument has been built with its unique set of capabilities and prospective applications. It is now time for RIMS users and collaborators to come together, share best practices, discuss challenges, and set collaborative goals moving forward.
Themes
Visits
One of the main applications of RIMS instruments is in the analysis of nuclear material, since so much can be learned about its current state and origin from its isotope ratios. With the ongoing decommissioning efforts at the Fukushima Daiichi Nuclear Powerplant, the workshop’s location in Fukushima City offers an urgent sense of purpose. It also provides the chance for RIMS users to visit RIMS instruments in Japan, built in collaboration with Kogakuin University, the JAEA at Oarai, and Nagoya University.
Please see the agenda attached below for the full travel schedule. The workshop will start from Tokyo, visiting Kogakuin University in Hachioji on Monday 25 March. The JAEA lab in Oarai will be visited on Tuesday 26 March. From there, the group will travel to the TEPCO facility near Tomioka on Wednesday 27 March. Talks will be held at the Institute for Environmental Radiation at Fukushima University on Thursday and Friday 28 - 29 March. For those who wish to visit Nagoya University's laser lab, a visit can take place on Saturday 30 March.
Most travel will be done by public transportation. Local trains can be payed for by Suica Card, which can be purchased and loaded at the airport or train station. The shinkansen is not covered by the Suica card. The attached document estimates the costs of each journey. It is recommended that participants travel light, ideally with a backpack and wearing comfortable shoes.
Accommodation
It is expected that those visiting the labs at the beginning of the week will be staying together in the same hotels. Rooms will be reserved for an estimated number of participants, however they should be booked and payed for by the participants themselves. More information will follow closer to the workshop date.
Public Outreach
The genesis for this event is a direct result of the activities of the LISA network. Within the LISA-4-Society actions, the event will feature a public lecture on the topic of nuclear forensics, in a collaborative English/Japanese presentation.
Funding
This Marie Sklodowska-Curie Action (MSCA) Innovative Training Networks (ITN) receives funding from the European Union’s H2020 Framework Programme under grant agreement no. 861198
Klaus Wendt - Fundamental laser spectroscopy and laser ion source development at the LARISSA laboratory of the University of Mainz – from 6-Lithium to 255-Fermium
Testuo Sakamoto - History of the Development of a High Spatial Resolution TOF-SIMS/SNMS Apparatus
Brett Isselhardt - Analysis of small samples of spent nuclear materials for interpreting reactor operating history
The LARISSA laboratory at the Institute of Physics of Johannes Gutenberg University was founded in 1988 shortly after the Chornobyl nuclear reactor accident to develop laser mass spectrometric techniques for the sensitive and selective determination of lowest-level contaminations of specific radiotoxic isotopes of relevance, as e.g. 41-Ca, 90-Sr, 236-U. In the past 35 years, R&D activities have been widely broadened by addressing the advancement of multi-step resonance ionization mass spectrometry (RIMS) and its application to numerous exotic elements and isotopes. For this purpose, the 30 keV RISIKO off-line radioactive ion beam (RIB) facility and the MABU quadrupole mass spectrometer were equipped with dedicated laser ion sources in combination with highly specialized solid-state lasers. A multitude of applications aside from the original goal of ultra-trace analytics, cover direct laser spectroscopic studies on the atomic and nuclear structures of rare isotopes complementing the identification of efficient and selective laser ionization schemes for use at on-line RIB production plants and in analytics. On top of this, ion beam purification and isotope selection for distinct fundamental studies are performed. This wide spectrum of applications addresses species from almost the entire periodic table of elements, for which two basic prerequisites are imperative: (1) the access to and the handling permission for altogether about 100 radioisotopes up to the German exemption limit including 47 isotopes out of 12 actinide elements and (2) the steadily ongoing refinement and adaptation of the laser systems. Optimized laser systems at present allow for (1) maintenance-free, stable long-term utilization, (2) fast automated access as well as wide-range continuous tuning of wavelengths or, alternatively, (3) narrow bandwidth operation for high-resolution spectroscopy. Today, more than 100 of these dedicated Ti:Sa laser types are in use worldwide, predominantly at large-scale research centers. A presentation of the Larissa lab together with recent results shall be given, highlighting the relevance of the work for the sensitive and selective ultra-trace analysis of radioisotopes by using conventional RIMS as well as resonant laser secondary neutrals mass spectrometry.
In 2004, I started to develop a new TOF-SIMS/SNMS apparatus aiming at individual particle analysis of aerosols such as PM2.5. Since collected aerosols are a mixture of particles with different origin and histories during drifting in air, bulk analysis like ICP-MS and GC-MS is limited to reveal the details of each particles. Traditionally, SEM-EDS or SEM-WDS was used for individual particle analysis. But such method has insufficient sensitivity and lateral resolution because of low emission probability of characteristic X-ray and scattering of electron beam in the solid, respectively.
Imaging SIMS was developed in early 1980s using Focused Ion Beam (FIB) coupled with QMS or Magnetic sector MS. For a long time, FIB-SIMS was known as “high-lateral resolution” SIMS, and its lateral resolution was around 100 nm. But FIB-SIMS has some problems for aerosol analysis. One is lack of sensitivity and simultaneous detection of many species (both elements and compounds).
I designed a TOF-SIMS/SNMS with high lateral resolution and simultaneous detection ability. First of all, the FIB was carefully designed for chopping the DC beam while maintain a small beam spot. And a TOF-MS was also designed aiming for both SIMS and SNMS by considering deep depth of field of input lens system. As a result, ultimate resolution of 40 nm and high transmission of TOF optics were realized.
The TOF-SIMS/SNMS apparatus was adopted to many kinds of small samples, aerosols, cells, steels, all-solid-state batteries. After the accident of 1F, I focused on resonance SNMS for precise isotope analysis and imaging. I and my colleagues are now challenging the analysis of small dusts collected in 1F and fuel debris in the future.
This work was supported by the following research funding:
JST Sentan-Keisoku (“Development of Advanced Measurement and Analysis Systems”)
Ministry of the Environment, “The Environment Research and Technology Development Fund”
JAEA Nuclear Energy S&T and Human Resource Development Project through concentrating wisdom Grant Number JPJA21P21465814.
Interpreting the operating history of a nuclear reactor is a key question in safeguards, non-proliferation, and studies of environmental contamination. It can help answer questions related to the amount and quality of Pu or other radioactive materials that were produced during the irradiation. Traditional approaches to characterizing spent nuclear fuels rely either on radiometric counting and/or mass spectrometry, usually relying on chemical purification of the specific analyte to increase precision and accuracy. Here we present an approach using resonance ionization mass spectrometry (RIMS) to precisely analyze small, solid samples of spent nuclear materials to characterize isotope ratios of multiple elements simultaneously, without prior chemical separation. Dispensing with chemical separation avoids the addition of chemistry “blanks” (background), measuring multiple elements from the same volume allows the correlation of multiple irradiation characteristics, and working from small samples decreases the radioactive hazards in the laboratory.
We have applied Lawrence Livermore National Laboratory’s Laser Ionization of Neutrals (LION) instrument [1] to several samples of spent nuclear material (see Figure 1). This presentation will explain how we can analyze nearly any combination of 3 elements including U, Pu, Am, Sr, Rb, Mo, Zr, Nd, Ba, Cs simultaneously [2], during a single measurement, usually with enough material remaining to analyze the others in a subsequent analysis. We will show how connecting multiple isotope ratios across elements and comparing those analytical results to computational models provide an improved understanding of the operating history of a nuclear reactor.
References:
[1] Savina, M.R., Isselhardt, B.H., Trappitsch, R., “Simultaneous Isotopic Analysis of U, Pu, and Am in Spent Nuclear Fuel by RIMS”, Anal. Chem., doi.org/10.1021/acs.analchem.1c01360, (2021).
[2] Savina, M.R., Isselhardt, B.H., Shulaker, D.Z., Robel, M., Conant, A.J., and Ade, B.J., “Fission products in spent nuclear fuel particles: Simultaneous Sr, Mo, and Ru isotopic analysis by Resonance Ionization Mass Spectrometry”, Sci. Rep., 13, no. 1 (2023): 5193, (2023).
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-843771.
Yoshikazu Hirayama - Resonant laser ionization for nuclear spectroscopy at KISS
Chao Zhang - Research on Sr-RIMS under the Triple Resonance Excitation 5s² ¹S₀ → 5s5p ¹P₁° → 4d² ¹D₂ → 4dnf or 4dnp
Darcy van Eerten - Spatially Resolved Multi-Element Analysis of Hot Particles in the SIRIUS RIMS instrument
We have developed the KEK Isotope Separation System (KISS) [1] at RIKEN to study the nuclear structure of the nuclei in the vicinity of neutron magic number $N$ = 126 and 152 from the astrophysical interest. These neutron-rich nuclei have been produced by using multinucleon transfer reactions [2] with the combinations of the low-energy $^{136}$Xe/$^{238}$U beams and the production targets of W, Ir, and Pt. At the KISS facility, these radioisotopes are ionized by applying in-gas-cell resonant laser ionization technique. In the ionization process, we can perform laser ionization spectroscopy of the refractory elements with the atomic number $Z$ = 72-78 such as Hf, Ta, W, Re, Os, Ir, and Pt, which can not be performed in other facilities. Laser spectroscopy can be used to effectively investigate the nuclear structure through the measured magnetic moments, isotope shifts (IS) $\Delta \nu$, changes in the mean-square charge radii $\delta$<$r^2$>, and quadrupole deformation parameters |<$\beta_2^2$>|$^{1/2}$.
We have studied the resonant ionization schemes of these elements by offline tests, and performed in-gas-cell resonant laser ionization spectroscopy of $^{199g,199m, 200, 201}$Pt [3], $^{196,197,198}$Ir [4], and $^{194,196}$Os [5] produced at KISS. By using a multi-reflection time-of-flight mass-spectrograph (MRTOF-MS) combined with resonant laser ionization technique, we could discover the new neutron-rich $^{241}$U isotope for the first time in 40 years [6].
In this workshop, we will report the results of resonant laser ionization spectroscopy at KISS, and the perspective of future plan at KISS.
References
[1] Y. Hirayama et al., Nucl. Inst. Meth. B353, 4 (2015), and B412, 11 (2017).
[2] Y.X. Watanabe et al., Phys. Rev. Lett. 172503, 1 (2015).
[3] Y. Hirayama et al., Phys. Rev. C 96, 014307 (2017), and 106, 034326 (2022).
[4] M. Mukai et al., Phys. Rev. C 102, 054307 (2020).
[5] H. Choi et al., Phys. Rev. C 102, 034309 (2020).
[6] T. Niwase et al., Phys. Rev. Lett. 130, 132502 (2023).
Resonance Ionization Mass Spectrometry (RIMS) leverages the energy differences in transition states between various elements and isotopes to achieve isobaric suppression and heightened isotopic selectivity. Furthermore, multi-step resonance ionization processes are capable of exciting atoms to specific Rydberg states, thus enhancing ionization efficiency. The focal point of this research is the three-step resonance ionization pathway involving the transition 5s² ¹S₀ → 5s5p ¹P₁° → 4d² ¹D₂ → 4dnf or 4dnp. The measurement of the isotope shift (IS) among Sr natural isotopes, the evaluation of resonance ionization efficiency, and the observation and analysis for Stark shift in high Rydberg-state Sr atoms have been done in this study.
Keywords: Resonance Ionization Mass Spectrometry, Sr-90 analysis, ionization efficiency, isotope shift, isotopic selectivity.
1.Introduction
RIMS for the determination of Sr-90 holds great promise in achieving a lower detection limit and a significant advantage in terms of high isotopic selectivity, particularly when employed within a multi-step ionization scheme. However, there is a need for further research into more efficient ionization schemes and the clarification of isotope shifts of Sr-90 concerning other Sr isotopes. In our laboratory, we have conducted related research on Sr-90 RIMS, with a focus on investigating the three-step resonance ionization schemes 5s² ¹S₀ → 5s5p ³P₁ → 5s5d ³D₂ → 4dnf or 4dnp, as documented in previous studies[1],[2]. Additionally, we explored the scheme 5s² ¹S₀→5s5p ¹P₁°→4d² ¹D₂→4dnf or 4dnp, as detailed in reference [3].
In this study, the scheme of 5s² ¹S₀→5s5p ¹P₁°→4d² ¹D₂→4dnf or 4dnp (corresponding to the laser scheme of 460.9 nm ~ 655.2 nm ~ 426.3 nm, named with the “scheme II”) was selected for in-depth research and analysis of its isotope selectivity, ionization efficiency, and the energy level characteristics of Rydberg-state Sr atoms in this transition channel.
The experiment setup is named with resonance ionization-quadrupole mass spectrometer (RI-QMS). The Sr atoms absorb three laser photons in the scheme II, transiting to the Rydberg state (n* = 39.4), and subsequently autoionize under the influence of a weak electric field (few V/cm). The Sr ions produced are selected by the QMS (Extrel RP 2010_A) and detected by the microchannel plate (MCP) for spectrum analysis.
For assessing the ionization efficiency, the two-stage resonance ionization process (460.9 nm ~ 405 nm; 5s² ¹S₀→5s5p ¹P₁°→(4d²+5p²)¹D₂, named with the “scheme I”), was used for comparison.
2.Methodology and experimental contents
To measure the isotope shift (IS) of the 460.9 nm laser, the resonance ionization spectrum under scheme I was directly employed. For the 655.2 nm laser, it was introduced to disrupt the resonance ionization spectrum under the scheme I, and IS was measured through the valleys on the new spectra.
In the RI-QMS, a weak electric field was employed to induce the ionization of excited Sr Rydberg atoms and propel the generated Sr ions from the ionization region into the QMS. In this scenario, the Stark effect occurs, and the energy level of n* = 39.4 is no longer singular and straight. Instead, the electric field strength and the energy level shifts adhere to a parabolic distribution, referred to as the quadratic Stark shift. This shift can be elucidated from a classical physics perspective, wherein the induced electric dipole moment by the external electric field interacts once again with the external electric field. To elucidate the characteristics of the Stark shifts for Sr atoms at this energy level, a method termed "dual electric field ion transport" was devised to convey Sr ions generated under the electric field near 0 V/cm into the QMS and MCP for a more comprehensive spectrum inspection.
3.Conclusion
In this study, the examined three-stage scheme (460.9 nm ~ 655.2 nm ~ 426.3 nm) showed notably higher ionization efficiency for Sr-88 compared to the two-stage scheme. The isotope shift for natural Sr isotopes with the 460.9 nm laser was measured and compared with peer-reviewed work. The isotope shift for the 655.2 nm laser was measured for the first time.
The Stark effect around the energy level of n* = 39 was explored. Findings show the quadratic Stark shifts with two opposite trends. Remarkably, negative polarizability values, a first at this energy level, were observed and explained by MQDT.
Reference
[1] Cheon D. et al. J. Spectrosc., 2018, 2018.
[2] Iwata Y. et al. Hyperfine Interact., 2020, 241: 1-8.
[3] Iwata Y. et al. J. Quant. Spectrosc. Radiat. Transf., 2021, 265: 107549.
[4] Bushaw B. A. et al. Spectrochim. Acta B At. Spectrosc., 2000, 55(11): 1679-1692.
[5] Anselment M. et al. Z. Phys. D At. Mol. Clust., 1986, 3(4): 421-422.
So-called ‘hot particles’ are micrometre-scale fragments deriving from nuclear fuel. In the Chornobyl Exclusion Zone, these particles have contaminated the environment since the accident. They are composed of partially spent fuel fragments of mostly low-enriched U, and (ultra)-trace levels of other actinides and fission products.
Nuclear materials that contaminate the environment present an ongoing challenge to characterize due to their small size and diverse morphology. The SIRIUS RIMS instrument in Hannover, Germany, analyses isolated hot particles through resonance ionization mass spectrometry (RIMS). It is an adaptation of a commercial time-of-flight secondary ion mass spectrometry (ToF-SIMS) instrument (IONTOF.V), and five Ti:Sa lasers. With two frequency-doubled, fast-switching Ti:Sa lasers, it is capable of rapid element-selective analysis of U, Np, Pu, Am, Sr, Zr. Isotope ratio analysis of these elements in hot particles reveal the particle’s origin, environmental sensitivity, and an estimation of the time spent in the environment.
Spatially resolved analysis can distinguish between fissionogenic and natural nuclides, which will be shown on a particle containing both natural Zr-cladding, and Zr fission products. In a second particle that has been bisectioned, environmentally-derived and fissionogenic Sr isotopes are homogenous over the cross-section, showing the particle’s interaction with the environment is not limited to the particle’s surface.
Matou Stemmler - Ionization scheme development for actinides at the LARISSA laboratory in Mainz
Naoki Matsumoto - Rapid Changeover of Target Element in Resonance Ionization Mass Spectrometry by switching fundamental/SHG Operation of Ti:Sapphire Laser
Kenji Nanba - Introduction to Fukushima Institute for Environmental Radiation
(IER) and recent work in trace analytical techniques
In order to perform ultra trace analysis of radionuclides in environmental samples based on resonance ionization mass spectroscopy (RIMS), efficient and highly element-selective laser excitation schemes are required. To analyse different all-relevant actinides within a single sample during one measurement, simple and versatile two-step ionization schemes need to be developed. The use of fully automated grating Ti:sapphire lasers featuring intra-cavity second harmonic generation allows for an easy and instantaneous change of the ionization scheme and therefore element of interest during the measurement.
In the past few years, the RIMS method has been successfully used at the RISIKO mass separator in the Institute of Physics Johannes Gutenberg University Mainz for the development of highly efficient and selective ionization schemes and spectroscopic studies on various actinides. This presentation will focus on the development of ionization schemes and on atomic and nuclear studies of the minor actinides that are present in spend nuclear fuel, which comprises neptunium, americium, and curium. New two-step excitation schemes for the analysis of ${}^{237,239}$Np, ${}^{241,243}$Am and ${}^{244-248}$Cm were identified and investigated and will be discussed.
In the analysis of samples containing fission products, nuclear fuel materials, actinide nuclides, it is necessary to combine the fundamental and second harmonic generation (SHG) of Ti:Sapphire laser to achieve efficient resonant ionization for the target elements. We developed a modified grating-type Ti:Sapphire laser that can instantly switch between fundamental and SHG operation mode, named mode switching Ti:Sapphire laser. Rapid changeover of Cs/Sr resonant ionization using two set of the mode switching Ti:Sapphire laser was demonstrated.
This work was supported by JAEA Nuclear Energy S&T and Human Resource Development Project through concentrating wisdom Grant Number JPJA21P21465814.
Karin Hain - Providing Element Selectivity in AMS measurements
Accelerator Mass Spectrometry (AMS) is the technique of choice for the detection of long-lived radionuclides with typical isotopic abundances of 10$^{−12}$ to 10$^{−16}$ (or 10$^7$ atoms per sample) in the environment. Interferences from stable isobars, however, usually restricted the applicability of this method to selected nuclides. The novel Ion-Laser InterAction Mass Spectrometry (ILIAMS) technique at the Vienna Environmental Research Accelerator VERA can overcome this limitation in many cases by highly-efficient isobar removal at eV-energies. In this way, nuclides can be measured for the first time with AMS while others become accessible also on low-energy AMS-systems. This opens up exciting possibilities e.g. in environmental radioactivity research ($^{90}$Sr, $^{99}$Tc, $^{135}$Cs) or Earth sciences ($^{26}$Al, $^{36}$Cl, $^{41}$Ca).
ILIAMS exploits differences in detachment energies (DE) within isobaric systems by neutralizing anions with DEs smaller than the photon energy via laser photodetachment. In addition, molecular interactions with the buffer gas can further enhance isobar suppression. Thereby, the VERA-facility has recently achieved the most sensitive detection of $^{90}$Sr at the 3 attogram level in mg of stable Sr from 300 mL of seawater and 1 g of coral aragonite. Furthermore, the laser-induced suppression of $^{236}$U during measurements of $^{236}$Np will considerably improve the characterisation of a spike material for the analysis of environmental $^{237}$Np. During the last 4.5 years we have intensively studied possibilities of analyzing environmental concentrations of $^{99}$Tc with AMS. Complementary to ILIAMS, high-energy AMS was applied using the 14 MV tandem accelerator at the Australian National University (ANU, Canberra). With this method, we determined the $^{99}$Tc concentration in selected samples from different environmental reservoirs, including 1 g peat bog samples and 10 L water samples from the Pacific Ocean and European rivers.
This project received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101008324 (ChETEC-INFRA) and No 824096 (Radiate) and from the Austrian Science Fund (FWF): I 4803-N and P 31614-N28.
Momo Mukai - Mass and isotope shift measurements of neutron-rich tungsten isotopes at KISS
Tetsu Sonoda - The development of the gas cell-based laser ionization technique for low-energy RI beam
Mitzi Urquiza - A cw-OPO seeded pulsed OPA system towards High-Resolution Laser Spectroscopy
The nuclei around Z = 72 - 78 are known as transitional nuclei, exhibiting a multitude of nuclear shapes depending on the neutron and proton numbers (N and Z) [1]. Around N = 116, various theoretical calculations predict prolate deformation for lighter isotopes, passing through γ-soft or triaxial shapes, and reaching oblate shapes in heavier isotopes [2,3]. The evolution of their nuclear structure has been investigated through the level structure and properties of β- and K-isomer decays obtained from γ-ray spectroscopy, nuclear electromagnetic moments, and charge radii obtained from laser spectroscopy, mainly for nuclei around the β-stability line and beyond N = 116 for osmium (Z = 76) and platinum (Z = 78). For neutron-rich nuclide around tungsten, fewer experimental results are known due to the difficulty of production.
The KEK Isotope Separation System (KISS) [4] was developed to perform nuclear spectroscopy of heavy neutron-rich isotopes produced by multi-nucleon transfer reactions. We conducted precise mass measurements using a multi-reflection time-of-flight mass spectrograph and isotope shift measurements of neutron-rich tungsten isotopes at KISS to study shape evolution. In this contribution the recent measurement results will be reported.
[1] R. F. Casten, Nucl. Phys. A 443, 1 (1985).
[2] L. M. Robledo et al., J. Phys. G 36, 115104 (2009).
[3] K. Nomura et al., Phys. Rev. C 83, 054303 (2011).
[4] Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res. B 412, 11 (2017)
We have been developing a gas cell-based laser ionization technique for the production of low-energy Radioactive Isotope (RI)-beam in two application schemes. One is to obtain a wide variety of the low-energy RI-beams from high-energy RI-beams provided by the BigRIPS fragment separator at RIKEN. And the other is ongoing phase for the feasibility study of the production of medical radioisotope:astatine-211 that is one of remarkable advantage isotopes for targeted alpha-particle therapy. Both applications owe to the selectivity and sensitivity by a resonant laser ionization technique that gives an opportunity for performing the laser spectroscopy on nuclear physics. The presentation includes an overview and current status of our project.
[Reference]
[1]T.Sonoda et al., Nucl.Inst.and Meth.B 295 1(2013).
[2]T.Sonoda et al., Prog. Theor. Exp. Phys. (2019), 113D02.
[3]T.Sonoda et al., RIKEN Accelerator Progress Report Vol56, in printing.
Resonant laser excitation in atomic spectrum studies unveils nuclear structures. Interactions of the nuclear ground state with the electronic shell induce hyperfine structure (HFS) and isotope shift (IS), enabling precise measurement of nuclear properties such as spin (I), magnetic dipole moment ($μ_I$), electric quadrupole moment ($Q_s$), and changes in mean square charge radii ($δ⟨r^2⟩$). Accessible with lasers, atomic transitions of valence electrons in the range of a few eV necessitate an optimal optical linewidth for high-resolution laser spectroscopy. Techniques like collinear resonance ionization spectroscopy employ a resonance peak linewidth of 40-70 MHz to resolve the HFS in most elements. Pulsed laser light with a full width at half maximum (FWHM) of less than 50 MHz has been achieved through various methods, including the seeding of a pulsed dye amplifier and injection-locking a titanium:sapphire (Ti:Sa) laser. As exotic nuclides demand hard to access wavelengths, new laser techniques are essential. While dye lasers and Ti:Sa-based systems prevail, an optical parametric oscillator (OPO) seeded dye amplifier system demonstrates comparable performance near 330 nm. This proposed setup aims to generate high-energy pulses (in the range of 1000 nm to 1530 nm) using a narrow-band cw-OPO seeded optical parametric amplifier (OPA) towards high-resolution spectroscopy of Actinides. Preliminary characterization of the pulse length and optical linewidth were done to meet specific experimental requirements, including mode-hope-free tuning suitability.
Felix Berg - Application of TOF-SIMS and rL-SNMS for the investigation of geochemical interactions of plutonium with Opalinus Clay and hardened cement paste
Vadim Gadelshin - Aerosol particle studies at rL-SNMS machine in Yekaterinburg: aspects and prospects
Paul Hanemann; Tobias Weissenborn - Location, Isolation, RIMS and Dissolution of Hot Particles from the Chornobyl Exclusion Zone
The safety case of a deep geological repository (DGR) for long-term nuclear waste storage requires extensive knowledge about the interactions of the radioactive inventory with the (geo-)technical and geological barriers. Due to their long half-life, high radiotoxicity and complex aqueous chemistry, plutonium isotopes are of major interest as high-level radioactive waste (HLW) that needs to be stored safely for generations. To assess the capabilities as well as limitations of possible concepts for a DGR, the study of the geochemical interactions of plutonium with materials considered for a long-term nuclear waste repository is required.
Argillaceous rock is considered as a potential host rock system for a deep geological repository in multiple European countries [1-4]. Opalinus Clay (OPA, Mont Terri rock laboratory, St-Ursanne, Switzerland) with its extensive compositional and structural heterogeneities has previously been studied as a reference material in batch sorption and bulk diffusion studies with plutonium [5,6]. Similarly, hardened cement paste (HCP) as reference for the construction material of a DGR and part of the multi-barrier approach, has been under investigation for its chemical interactions with plutonium in analogous experiments [7,8]. Unfortunately, batch sorption experiments or the destructive abrasive peeling required to gain diffusion profiles in migration studies do not result in information about the microstructure of the porous medium and the role of structural heterogeneities in the transport of the radionuclide cannot be assessed. If the data from these experiments is modeled, only averaged parameters for transport and retention are retrieved. Therefore, to have a better and more in-depth understanding of the interactions between radionuclides and these materials, a spatially resolved approach would be favorable.
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an analytical technique that allows for spatially resolved investigations of the composition of surfaces at the micrometer or even nanometer scale. In this technique, a primary ion beam is scanned over the surface and a full mass spectrum is retrieved for every sampled position by analyzing the sputtered secondary ions in a TOF-MS. By comparing the relative intensities for a mass detected at different positions, the distribution of an element or a chemical species is retrieved. One inherent major drawback of TOF-SIMS, especially when studying an analyte at low concentrations, are isobaric interferences. Resonance ionization mass spectrometry (RIMS) is a promising approach to resolve this issue [9]. RIMS uses multi-step photoionization via laser light to photo-ionize atomic species. Due to the unique electronic structure of every element, this is highly selective and results in excellent background suppression. The combination of TOF-SIMS and RIMS to resonant laser secondary neutral mass spectrometry (rL-SNMS) is a promising approach that has been demonstrated to suppress isobaric interferences and isolate the analyte signal [10-12].
We will present the current development state of the combined approach of TOF-SIMS and rL-SNMS for the study of sorption and diffusion samples of HCP and OPA with plutonium on the micrometer scale and assess the capabilities and limitations of both methods. The rL-SNMS setup consists of a TOF-SIMS III (IONTOF, Germany) and three Ti:Sa lasers jointly pumped by a Nd:YAG laser [11]. The sensitivity of the setup has been systematically investigated via sorption samples of HCP placed in contact with 10$^{-6}$ to 10$^{-9}$ M $^{239}$Pu(IV) under anaerobic conditions in artificial cement pore water. To showcase the analysis of diffusion profiles, we used samples of OPA placed in contact with 10$^{-6}$ M $^{242}$Pu(VI) in OPA pore water as mobile phase under aerobic conditions. The concentrations of Pu were in some cases deliberately set above the solubility limit to either ensure a constant equilibrium concentration in solution, or to assess the sensitivity of TOF-SIMS and rL-SNMS systematically. We will present a more method-oriented sample preparation as well as results concerning the oxidation state of plutonium in OPA pore water obtained via capillary-electrophoresis coupled to inductively coupled plasma mass spectrometry (CE-ICP-MS).
Acknowledgements
Funding from the German Federal Ministry of Education and Research (BMBF) under contract number 02NUK044B and 02NUK075B, as well as from the European Union’s Horizon 2020 project EURAD (WP FUTuRE), EC Grant agreement no. 847593, is acknowledged.
References
[1] The Repository Site Selection Act (Standortauswahlgesetz - StandAG) (2017)
[2] Mazurek, M., Gimmi,T., Zwahlen, C., Aschwanden L., Gaucher, E.C., Kiczka, M., Rufer, D., Wersin, P., Marques Fernandes, M., Glaus, M.A., Van Loon, L.R., Traber, D., Schnellmann M. and Vietor, T. (2023). Swiss deep drilling campaign 2019–2022: Geological overview and rock properties with focus on porosity and pore-space architecture. Appl. Geochem. 159: 105839
[3] Montavon, G., Ribet, S., Hassan Loni, Y., Maia, F., Bailly, C., David K., Lerouge, C., Madé, B., Robinet, J.C. and Grambow, B. (2022). Uranium retention in a Callovo-Oxfordian clay rock formation: From laboratory-based models to in natura conditions. Chemosphere 299: 134307
[4] Gens, R., Lalieux, P., De Preter, P., Dierckx, A., Bel, J., Boyazis, J.-P. and Cool, W (2003). The Second Safety Assessment and Feasibility Interim Report (SAFIR 2 Report) on HLW Disposal in Boom Clay: Overview of the Belgian Programme. MRS Online Proceedings Library 807, 469–474
[5] Amayri, S., Fröhlich, D.R., Kaplan, U., Trautmann, N. and Reich, T. (2016). Distribution coefficients for the sorption of Th, U, Np, Pu, and Am on Opalinus Clay. Radiochim. Acta 104(1): 33-40
[6] Kaplan, U., Amayri, S., Drebert, J., Rossberg, A., Grolimund, D. and Reich, T. (2017). Geochemical Interactions of Plutonium with Opalinus Clay Studied by Spatially Resolved Synchrotron Radiation Techniques. Environ. Sci. Technol. 51: 7892-7902
[7] Wieland, E. and Van Loon, L. R. Cementitious Near-Field Sorption Data Base for Performance Assessment of an ILW Repository in Opalinus Clay. PSI Bericht Nr. 03-06, Nagra NTB 02-20
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The Ural Mountains are a very interesting region for climate research on Earth. This mountain range runs north-south more than 2500 km from the Arctic Ocean to the Eurasian Steppe belt. Being the conventional boundary between Europe and Asia, the Urals are also the endpoint of climatic effects, caused by the Atlantic or Siberian air masses. Since Ancient times the region is world-known for its natural resources, mineral production, gold and gem mines, earned the «treasure box» fame. Today the biggest titanium and uranium production capacities are located here too. However, the large number of industrial facilities left their imprint on the regional ecology, with the Kyshtym disaster (1957) as the worse highlight, led to the formation of the East Ural Natural Reserve – the exclusion zone due to the radioactive contamination.
Anthropogenic aerosols are one of the main objects for ecological studies. Emitted by an industrial facility, they can be spread over a long distance, presenting a danger to the environment and to the population. To obtain the most realistic assessment of the associated health risks, it is promising to investigate the distribution of chemical composition over the surface and in the volume of aerosol particles. The new setup for laser resonance ionization secondary neutral mass spectrometry (rL-SNMS) at the Ural Federal University can be used for this purpose, and moreover, to compile an atlas of aerosol microparticles related to a specific regional production facility. To define a particular fingerprint of the aerosol origin, it is intended to focus on the content of rare-earth elements (REE) and their location in the structure of microparticles. For instance, the concentration ratio of light to heavy REEs is a good marker for anthropogenic sources, but, due to the trace amount of REEs in aerosol samples, this topic remains scarcely investigated. The resent developments in resonance ionization mass spectrometry can overcome this issue, providing a high sensitivity even to ultra-trace concentration of REEs. The status of the rL-SNMS machine in Yekaterinburg as well as the concept of the aerosol research program is going to be presented.
Micron sized fragments of nuclear fuel, so called “hot particles” have been released during the Chornobyl nuclear accident in 1986 into the exclusion zone (CEZ). The combination of flotation with high-density-solutions, electron microscopy and a micromanipulator allow the isolation of single hot particles from soil samples of the CEZ [1]. Non-destructive mass spectrometry is performed on individual particles to characterize them. The RIMS-setup at the University of Hannover combines the spatial resolution of a commercially available IONTOF TOF.SIMS 5 with the elemental selectivity of resonant laser ionisation. The isotopic fingerprint of these particles allows to links them to the nuclear accident as well as identifying particles with unusual isotope ratios.
After the determination of the isotope ratios for different actinides, sequential leaching can be applied to the particles. Combined with non-destructive x-ray absorption spectroscopy at different beamlines the results of the sequential leaching give an insight on the chemical structure of the particles. Furthermore, a method to cut the particles in half was developed in cooperation with the Forschungszentrum Jülich. With that, it is possible to have a sample in reserve and study the inner core of the particle.
[1] DOI:10.1039/9781837670758-00001
Masato Morita - Development of Practical Resonance Laser SNMS System for Decommissioning of Fukushima Daiichi Nuclear Power Plant
Ziva Shulaker - Multielement Measurements Without Isobaric Interferences in Stardust Grains with application to Nuclear Fuel Analysis
Michael Savina - A new laser for ultra-trace RIMS
Micrometer-sized particles condense in the atmosphere of exploding stars and their isotopic composition records the nucleosynthesis processes in the star. These particles, called stardust or presolar grains, formed before the formation of our sun and solar system. These stardust grains were ultimately incorporated in the cloud of matter that our solar system formed from. Because isotopic systems in stardust grains represent the ground truth values as inputs for nucleosynthesis models, studying isotopic systems in stardust is important for understanding the formation of p- and s-process nuclei. After separating stardust grains from their meteorite matrix, these grains are the only material older than the solar system that can be analyzed in a laboratory setting. However, stardust grains are difficult to analyze because the average grain size is ~1 μm diameter and analytes of interest (e.g., Ti, Sr, Zr, Mo, Ru, Ba, W) are atom limited. Resonance ionization mass spectrometry (RIMS) is ideal for analyzing stardust grains because of the high spatial resolution and sensitivity, low sample utilization, and the ability of RIMS to discriminate against isobaric interferences by selectively ionizing only the elements of interest. We present data from ~100 stardust (silicon carbide and graphite grains) using newly developed RIMS methods for simultaneously collecting multielement measurements (up to 19 isotopes of 3 elements, such as Zr, Mo, Ru) on the LION instrument at Lawrence Livermore National Laboratory. To achieve this, ionization lasers of elements with isobaric interferences (e.g., Mo, Zr) are offset by 200 ns to discriminate isobaric interferences. Ultimately, this method allows for elemental analysis, regardless of isobaric interferences, of micron-sized particles for isotopes without performing chemical separation. We apply these multielement analyses of stardust grains to analyzing spent fuel and intentionally tagged fuel elements.
For taking out nuclear fuel debris safely, there is a strong need for analysis methods of debris precisely. The most important thing in the debris analysis is isotope ratio of a certain elements, because the ratio is closely related to both the accident progress and the state of debris. Secondary ion mass spectrometry (SIMS) is a candidate for the analysis. However, isobaric interferences often make it difficult to analyze precise isotope ratio analysis. We has been developed a resonance laser sputtered neutral mass spectrometer (R-SNMS) for element-selective ionization and detection by using a set of newly developed tunable Ti:Sapphire lasers. In R-SNMS, synchronization (alignment) between the SIMS device and the Ti:Sapphire laser requires specialist skill. By automation and remote, the R-SNMS improved to a practical and safe device.
This work was supported by JAEA Nuclear Energy S&T and Human Resource Development Project through concentrating wisdom Grant Number JPJA21P21465814.
One of the strengths of Resonance Ionization Mass Spectrometry (RIMS) is its selectivity, that is the ability to ionize only one element in a sample containing many different elements and thereby eliminating the need for chemical purification prior to analysis. However, in cases where backgrounds are unavoidable, such as ultra-trace analysis or when overwhelming excesses of isobaric atoms are present, RIMS has the unique ability to quantitatively measure backgrounds by tuning the laser(s) off-resonance. The resonance signal of the analyte element disappears, leaving behind ions produced by other processes such as secondary ionization due to sputtering, off-resonance ionization of atoms and molecules, and photodissociation of molecules into fragments isobaric with the analyte. RIMS spectra generally take from several to several tens of minutes to collect. Provided that the sample does not change over that time under the influence of the ion beam or laser used to atomize it, off-resonance spectra collected later can be quantitatively subtracted to produce background-free results. However, ion sputtering during analysis can change the ratio of atoms to molecules in the sputtered flux over time, and hence change the contribution of non-resonant background ions caused by photodissociation. Further, in the case of ultra-trace analysis in which lasers are used to desorb material, the elemental composition of the sample changes over time as the more volatile components are preferentially removed in the early stages of the analysis. In these cases the off-resonance spectrum collected many minutes later is not a true representation of the background present in the resonance spectrum which was, in effect, collected on a different sample.
To address this issue we have developed a RIMS method known as blinking, in which the resonance signal is extinguished (or “blinked”) by switching one of the lasers between on- and off-resonance every other (or every third, or fourth, etc.) pulse. In this way, perfect background subtraction is possible, since the on- and off-resonance spectra are interleaved rather than sequential, and both therefore sample the same time-dependent changes in the analyte. We first demonstrated this technique by alternating on- and off-resonance pulses from two lasers and achieved success in measuring 238Pu accurately at concentrations less than 1 ppb in a soil matrix containing a large (~30,000:1) excess of 238U. We later developed a Ti:Sappire laser capable of self-blinking, such that a second laser is not needed, and measured 238Pu against an excess of 238U of ~50,000:1. The new laser has no moving parts, so there is no settling time after switching wavelengths, and can therefore blink at an arbitrary rate (we currently use 1500 Hz). In this talk, we demonstrate this laser for trace analysis of 238Pu, as well direct analysis of ultra-trace fission products in irradiated uranium. LLNL-ABS-858820
Linus Holtmann - Imaging the plant uptake of radionuclides on the single-cell scale using resonant laser ionization mass spectrometry
Aaron Lehnert - Production and characterisation of synthetic homogenous multi-element actinides samples via sol-gel as standards for mass spectrometry
Paul Hanemann - Spatially resolved trace analysis of radionuclides with laser ionization mass spectrometry
The RIMS-setup at the University of Hannover uses multiple grating-tuned Ti:Sa lasers to access a range of resonant ionization schemes. Combined with mass spectrometry, the method can detect actinides in single radioactive particles from the environment, down to 107 atoms of a single isotope [1]. In micron-sized particles from the Chornobyl exclusion zone, the relative 238Pu content can be determined by suppressing the dominant 238U in spent fuel. This is achieved quasi non-destructively without chemical preparation of the sample. The current capabilities of the RIMS-system are presented in this poster, with an outlook on further developments of the method and application to ultra-trace analysis.
[1] DOI:10.1126/sciabv.abj1175
In radioecological studies, the plant uptake and distribution of radionuclides are of major interest for risk assessment. In the present work, the elemental distribution within the tissue of plants is imaged by resonant laser secondary neutral mass spectrometry (rL-SNMS). This technique combines a commercially available time-of-flight secondary ion mass spectrometry (IONTOF TOF.SIMS 5) with a laser system for ionization of sputtered neutrals. Due to the excellent suppression of molecular isobaric interferences by rL-SNMS, about 10^10 atoms of technetium suffice to image the Tc-99 distribution inside plant cells with a spatial resolution of approximately 300 nm. The distribution of technetium in the two plant species Daucus carota and Pisum sativum was determined. For reasons of radiation protection, the plants were labelled with Tc-99 at a concentration of 0.1 mM. Such a low concentration renders measurements by conventional SIMS impossible. [1]
[1] DOI: 10.1016/j.jhazmat.2021.127143
MetroPOEM [1] is committed to developing SI-traceable mixed element reference materials for the calibration of mass spectrometric devices. In nuclear forensics, elemental selectivity and precise spatially resolved mass spectrometry is essential for ultra-trace analysis of environmental samples. Resonant laser secondary neutral mass spectrometry (rL-SNMS) combines both element selective isotope ratio measurements and spatial resolution on the micrometre scale. Multi-element reference materials are needed to investigate different ionisation efficiencies for the elements important for environmental analytics.
In this work we present a production method of mixed actinide samples such as U, Pu and Am via sol-gel. These samples consist exclusively of the respective metal and fulfil the conditions for homogeneity confirmed by EDX and SIMS. The spatially resolved element distribution was determined using rL-SNMS. ICP-MS is also used to determine the element composition.
[1] MetroPOEM is a collaboration of 22 partners from 13 countries throughout Europe funded by EURAMET under grant number 21GRD09 https://www.npl.co.uk/euramet/metropoem