Masabumi Miyabe

Japan Atomic Energy Agency | JAEA · Collaborative Laboratories for Advanced Decommissioning Science (CLADS)

Using three-step resonance ionization spectroscopy, over 200 even-parity autoionizing (AI) levels of atomic uranium, including Rydberg series converging to the second lowest ionic level (6L 11/2o), were observed in the 49 930–51 200 cm−1 energy range. Total angular momenta (J values) of these levels were determined by a polarization combination met...

The dynamic behavior of an ablation plume in ambient gas has been investigated by laser-induced fluorescence imaging spectroscopy. The second harmonic beam from an Nd:YAG laser (0.5–6 J/cm2) was focused on a sintered oxide pellet or a metal chip of gadolinium. The produced plume was subsequently intersected with a sheet-shaped UV beam from a dye la...

Spectroscopic properties of atomic species of plutonium were investigated by combining laser ablation and resonance absorption techniques for the analysis of a plutonium oxide sample. For 17 transitions of Pu atoms and ions, the absorbance, isotope shift, and hyperfine splitting were determined via Voigt profile fitting of the recorded absorption s...

We observed Doppler-free fluorescence spectra using ablation plumes. From the lineshape analyses the detailed collisional process in the ablation plume was revealed and the isotopic analysis for nuclides with small isotope shifts was demonstrated.

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm2. The temporal evolution of the ablation plume was investigated in vacuum and helium environments. In vacuum, the flow velocity perpen...

Characterization of kW class quasi-continuous wave (a pulse duration of 10 ms) laser interaction with metal targets and those with metal oxide targets are presented in respect to the laser induced breakdown and the successive laser induced melting and evaporation coupled with a mechanical response followed by ejection of various kinds of particles...

Triple resonance excitation to the autoionizing Rydberg state of atomic strontium was studied for the isotope-selective photoionization of strontium-90 (90Sr). We investigated a new resonance ionization scheme, namely, 689.4 nm–472.4 nm–404.2 nm that is less affected by the multiphoton ionization induced by the first (689.4 nm) laser compared to th...

Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels wi...

Rydberg levels in atomic calcium are of interest due to their use in highly isotope selective multiple-step resonance ionisation spectrometry, and also for nuclear physics investigations, but gaps remain in the data for higher lying levels in calcium isotopes other than ${}^{40}\text{Ca}$ . We report novel isotope shift data on four isotopes of cal...

An experimental characterization is presented on fine particles, droplets, and fragments produced at the interaction region between a 2.7 kW quasicontinuous wave (repetitive pulsed operation with a 10 ms pulse duration) fiber laser and stainless steel, alumina, and heavy concrete samples. In the samples, the recoil pressure induced by vaporization...

Three-step resonance excitation to autoionization states is a promising isotope-selective ionization technique for atomic strontium (Sr). We measured for the first time the DC Stark shifts of ten Rydberg levels (neff∼36−39, 50−55) of 88Sr converging to the 4d 2D3/2 limit using the 5s21S0 → 5s5p 1P1∘ → 5p21D2 → (4d 2D3/2 Rydberg series) transition p...

Study on the excitation process of magnesium atom has been conducted in microwave-assisted laser plasma. Experimentally, an Nd:YAG laser (532 nm, 5 mJ) was directed into the magnesium oxide (MgO) sample in various gases of helium, argon, and air at a reduced pressure to induce a luminous plasma. The plasma emission was significantly enhanced when a...

Strontium-90 (90Sr, half-life of 28.8 years) is one of the major fission products released in the Fukushima Daiichi Nuclear Power Plant accident in Japan. Due to the high concentrations of Sr stable isotopes in marine products, an upper limit for 90Sr isotopic abundance in them is of the order of 1 ppb or less. Resonance ionization technique using...

Nuclear accidents (e.g., at the Chernobyl and Fukushima Daiichi nuclear power plants) release considerable amounts of radioactive pollutants into the environment. Radioactive particles in dust and soil can range from a few microns to several microns in size. Detection of these micron-sized particles requires a fast and effective analytical method....

In atomic physics experiments, external cavity diode lasers (ECDLs) are often coupled with tapered amplifiers (TPAs) to provide a highly tunable laser source that also has relatively high output power. Usually these systems are mounted on separate baseplates in separate housings, and when the coupling optics are taken into account, the entire syste...

Resonant laser sputtered neutral mass spectrometry can greatly enhance the ionization efficiency of specific neutral sputtered atoms through resonant excitation using tunable laser(s). However, the laser beam cannot irradiate the entire volume where sputtered particles are moving, because the laser beam is focused. In contrast, for an extremely low...

Two-color resonant laser ionization sputtered neutral mass spectrometry offers high elemental selectivity. In this study, two-color resonance ionization in sputtered neutral Sr was confirmed by combining a grating type Ti:sapphire laser system and a time-of-flight secondary ion mass spectrometry (TOF-SIMS) system. The authors compared the ionizatio...

Using a semiconductor microwave source and a coaxial cable for microwave transmission, a compact microwave-assisted, laser-induced breakdown spectroscopy system without a microwave cavity or waveguide was developed. Several types of electrode heads were tested, so that the emission intensity was 50 times larger than without microwave. The limit of...

Laser Induced Breakdown Spectroscopy (LIBS) method is an attractive technique because real-time, in-situ and remote elemental analysis is possible without any sample preparation. The LIBS technique can be applied for analyzing elemental composition of samples under severe environments such as the estimation of impurities in the next generation nucl...

The dynamic behavior of an ablation plume in low pressure rare gas ambient was investigated with laser-induced fluorescence imaging spectroscopy for three refractory metals, i.e. titanium, zirconium and hafnium. A comparison of the plume expansion behaviors for the species of these elements revealed an atomic weight effect on the plume structure fo...

A frequency tunable external-cavity diode laser (ECDL) using a narrow bandwidth (∼0.3 nm) interference filter has been developed for resonance ionization spectroscopy of strontium (Sr) with high isotopic selectivity. Improved wavelength and single mode stabilities of this interference-filter-type ECDL (IF-ECDL) over a commonly used (also home-made)...

Resonant ionization laser spattered neutral mass spectrometry (R-SNMS) is a method of surface analysis. Since the sputtered neutral particles emitted having certain angular distribution, the wavelength (Doppler) shift will be occurred. Therefore, angularly spread particles cannot be ionized by the resonant laser due to the Doppler shift. In this st...

We investigated a promising three-step resonance ionization scheme of strontium (Sr) 5s ²¹ S 0 ⟶ 5s5p ³P1° ⟶ 5s5d ³ D 2 ⟶ 4dnp (or 4dnf, n = 39) using the first-step intercombination transition for the enhancement of isotope selectivity. The power broadening observed in the 2 nd transition indicates that laser power of less than 0.2 mW is sufficien...

We have developed an apparatus integrating resonance-ionization, ion-trap, and laser-cooling techniques for an ultratrace radioactive isotope Sr90 analysis. Trapped Sr+90 isotope ions were laser cooled, and their 4dD3/22→5pP1/22 transition isotope shift was experimentally measured to be −281(17) MHz by comparing individual spectra of Sr+88 and Sr+9...

We are developing an analytical method using laser ablation absorption spectroscopy (LAAS) to analyze radioactive waste mixed with zirconium (Zr), uranium (U), fission-products, transuranium and so on. It is of great importance to evaluate the characteristics of the plume formed by the objective particles for LAAS analysis. In this study, therefore...

Trapping and cooling of Sr⁺ isotope ions by an all-diode-laser system has been demonstrated in order to develop a novel mass spectrometric technique in combination with ion trap-laser cooling. First, we constructed external cavity diode lasers and associated stabilization apparatus for laser cooling of Sr⁺ ions. The transition frequencies confirmed...

To perform quantitative analysis of nuclear fuel materials by using laser-induced breakdown spectroscopy (LIBS), emission spectral lines of atoms should be clearly identified, which is far from other atomic and molecular disturbances, low background emission, and optimum emission intensity. To this end, intensified microwaves were introduced into t...

To study the dynamics of luminous plasma induced by a pulse laser and microwaves (MWs), time resolved imaging of microwave-assisted laser-induced plasma was carried out. In this study, a luminous plasma was induced by a second harmonic Nd:YAG laser (532 nm, 8 ns, 5 J) on calcium oxide (Ca2O3) pellet at low pressure (5 Torr) of Ar gas. The luminous...

The effect of ambient gas on measurements with microwave-assisted laser-induced plasma in microwave-assisted laser-induced breakdown spectroscopy (MA-LIBS) was studied with relevance for the analysis of nuclear fuel. A pelletized gadolinium oxide (Gd2O3) sample, which was used as a simulated nuclear fuel, was irradiated by a pulsed Nd:YAG laser (53...

We studied experimentally the effect of microwaves (MWs) on the enhancement of plasma emission achieved by laser-induced breakdown spectroscopy (LIBS). A laser plasma was generated on a calcium oxide pellet by a Nd:YAG laser (5 mJ, 532 nm, 8 ns) in reduced-pressure argon surrounding gas. A MW radiation (400 W) was injected into the laser plasma via...

We used laser-induced fluorescence imaging with a varying beam focal point to observe ablation plumes from metal and oxide samples of gadolinium. The plumes expand vertically when the focal point is far from the sample surface. In contrast, the plume becomes hemispherical when the focal point is on the sample surface. In addition, the internal plum...

For the remote analysis of the next generation nuclear fuel material containing minor actinide (MA), Laser Induced Breakdown Spectroscopy (LIBS) was applied to uranium oxide (U$$_{3}$$O$$_{8}$$) including a small amount of neodymium oxide (Nd$$_{2}$$O$$_{3}$$) as a simulated sample of MA. By using deconvolution technique for the spectra of Nd in U,...

An enhancement of emission intensity from a laser ablation plume, obtained by coupling a pulsed microwave using a simple wire antenna, is demonstrated to compensate the sensitivity reduction of a high resolution spectrometer that is required for nuclear fuel analysis. A gadolinium oxide sample was irradiated with 2.45 GHz, 250 W microwave pulse, an...

Intensified microwave coupled by a loop antenna (diameter of 3 mm) has been employed to enhance the laser-induced breakdown spectroscopy (LIBS) emission. In this method, a laser plasma was induced on Gd₂O₃ sample at a reduced pressure by focusing a pulsed Nd:YAG laser (532 nm, 10 ns, 5 mJ) at a local point, at which electromag...

We used nanosecond (ns) and femtosecond (fs) laser pulses to ablate gadolinium oxide samples and measured the ablated volume as a function of the laser pulse focal position. The effect of defocusing on the ablated volume, which decreases as the ablation pulse focal position approaches the sample surface, was observed for both ns and fs pulses. (C)...

To determine experimental conditions suitable for isotope analysis, we studied the plume dynamics of uranium. A uranium oxide sample was ablated by 2nd harmonic radiation from a Nd:YAG laser at a fluence of 0.5 J/cm2. The temporal evolution of the ablation plume was investigated in 800 Pa helium environment. It was found that the observation at 3–5...

The temporal evolution of the ablation plume of cerium was investigated by absorption spectroscopy. Cerium oxide pellets were ablated in a helium atmosphere by second-harmonic radiation (532 nm) from a Nd:YAG laser at a fluence of 0.5 J/cm2. The lateral velocity (expansion velocity horizontal to the sample surface) of the plume was determined from...

Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse...

For the remote analysis of low DF TRU (Decontamination Factor Transuranic) fuel, Laser Induced Breakdown Spectroscopy (LIBS) was applied to uranium oxide including a small amount of calcium oxide (3306ppm(weight)) as a sample, and the spectrum emitted from laser-breakdown plasma was examined. The characteristics, such as spectrum intensity and plas...

Emission characteristics of gadolinium plasma in the double-pulse LIBS using a femtosecond laser as an ablation source have been studied to achieve high sensitivity for analyzing next generation nuclear fuel in a future. In experiment, effects of the ablation laser focusing lens position and relative position of two plasmas were studied. The optimu...

A cerium oxide sample was ablated by 2nd harmonic radiation of Nd:YAG laser at a power density of 0.1GW/cm2. Time evolution of the ablation plume was investigated by laser absorption time-of-flight (TOF) measurement. It was found that the ablated ionic plume in vacuum consisted of two components having different velocities whereas the ablated neutr...

For the remote analysis of low DF TRU (Decontamination Factor Transuranic) fuel, Laser Breakdown Spectroscopy (LIBS) was applied to uranium oxide including a small amount of calcium oxide. The characteristics, such as spectrum intensity and plasma excitation temperature, were measured using time-resolved spectroscopy. As a result, in order to obtai...

We have investigated propagation characteristics of the laser ablation plume produced from CeO2 sample to optimize experimental conditions for isotope analysis for low-decontaminated TRU fuel. Vertical flow velocity and horizontal expansion velocity of the plume were evaluated with optical TOF measurement and Doppler splitting measurement. These me...

For applying Laser Induced Breakdown Spectroscopy (LIBS) to the analysis of nuclear fuel materials, it is very important to identify the emission spectrum and its intensity on impurities intermingled within complex emission spectra of matrix elements such as uranium (U) and plutonium (Pu). Then, the spectra of natural uranium are measured using LIB...

For remote isotope analysis of low-decontaminated trans-uranium (TRU) fuel, absorption spectroscopy has been applied to a laser-ablated plume of lanthanide elements. To improve isotopic selectivity and detection sensitivity of the ablated species, various experimental conditions were optimized. Isotope-selective absorption spectra were measured by...

For applying LIBS to the analysis of nuclear fuel materials, it is very important to investigate the analytical method to identify the emission spectrum and its intensity on impurities intermingled within complex emission spectra of matrix elements such as uranium and plutonium. Experiments using gadolinium as simulated sample, in which several 100...

For remote isotope analysis of low-decontaminated TRU fuel, we are developing an analytical technique on the basis of the resonance absorption spectroscopy for the laser-ablation plume. To improve isotopic selectivity and detection sensitivity of this technique, we measured absorption spectra of Gd atom with various conditions. As a result, high re...

We developed a frequency-stabilized diode laser using magnetically induced circular dichroism. From a spectroscopic study of the Rb-D2 line, the most stable Doppler-broadened and Doppler-free lines were found to be the transitions from the Fg=2 ground state of 85Rb and the crossover resonance from the Fg=3 ground state to the Fe=3 and 4 excited sta...

We have developed a frequency stabilized laser system for RIMS analysis of a long-lived radionuclide of calcium (41 Ca) in concrete waste materials. A stable reference laser has been developed using magnetically induced circular dichroism of atomic rubidium. The frequency stability was estimated to be 50 kHz over 8-h period from beat frequency meas...

We have developed a frequency stabilized laser system for RIMS analysis of a long-lived radionuclide of calcium (⁴¹ Ca) in concrete waste materials. A stable reference laser has been developed using magnetically induced circular dichroism of atomic rubidium. The frequency stability was estimated to be 50 kHz over 8-h period from beat frequency meas...

High-resolution resonance ionization spectroscopy has been utilized to determine a precise ionization potential of Ca. Three-step resonance excitation with single-mode extended-cavity diode lasers populates long and unperturbed Rydberg series of 4snp (1P1) and 4snf (1F3) states in the range of n=20--150. Using an extended Ritz formula for quantum d...

Laser-induced fluorescence spectroscopy has been employed to characterize the plume produced in nanosecond laser ablation of metallic neodymium. The kinetic-energy distributions of the neutral and ionized atoms in the plume under both vacuum and gas environments have been investigated. The population distribution of metastable levels in the ablate...

Multi-step resonance ionization spectrometry for long-lived nuclei in nuclear waste materials requires laser sources having high frequency stability and tunability. In this study we have developed a novel frequency control system consisting of digital circuitry and computer to improve the frequency tunability of the developed laser stabilization sy...

High precision resonance ionization spectroscopy has been applied to determination of an accurate ionization potential of 40Ca. Three-step resonant excitation with single-mode extended cavity diode lasers populates a series of 4snp (1P1) and 4snf (1F3) Rydberg states in the rage of n=20-150. By using an extended Ritz formula for quantum defect, the...

Laser-induced fluorescence spectroscopy has been employed to characterize a plume produced in nanosecond laser ablation of metallic neodymium. Kinetic energy distributions of ions and neutrals in the plume were investigated as functions of processing parameters such as laser fluence and ambient gas pressure. Population distributions of metastable l...

In nuclear waste materials there are various radionuclides to which standard analytical techniques are difficult to be applied. We are developing an analytical technique where such nuclides are ionized and mass-analyzed using diode laser based multi-step RIMS technique. The diode laser, however, has one drawback, i.e. its oscillation wavelength is...

In nuclear waste materials there are various radionuclides to which standard analytical techniques are difficult to be applied. We are developing an analytical technique where such nuclides are analyzed using multi-step resonance ionization mass spectrometry. In this study, we have developed an external cavity diode laser applicable to the analysis...

Clearance system, in which low-level radioactive wastes generated from decommission of nuclear facility and the contaminated level is lower than the clearance level can be treated as non-radioactive wastes, will be started in Japan in near future. In this paper, we will overview the possibility of collinear fluorescence spectroscopy and resonance i...

The isotope shifts and hyperfine-structure-splitting constants of the 6s2 1S0-5d6p 3D1 (λ=538.2 nm) and 5d2 3P2-5d6p 1D2 (λ=548.4 nm) transitions of La II have been measured by collinear laser-ion-beam spectroscopy for the accelerator-produced isotopes 135La and 137La, and for the naturally occurring isotopes 138La and 139La. The magnetic moments o...

The isotope shifts and hyperfine-structure-splitting constants of the 6s21S0-5d6p 3D1 (λ=538.2 nm) and 5d23P2-5d6p 1D2 (λ=548.4 nm) transitions of La II have been measured by collinear laser-ion-beam spectroscopy for the accelerator-produced isotopes 135La and 137La, and for the naturally occurring isotopes 138La and 139La. The magnetic moments of...

The laser induced fluorescence method using atomic beam combined with Doppler-free two-photon absorption technique was applied for the measurement of isotope shifts and hyperfine structures of atomic uranium including 234U, 235U, 236U and 238U isotopes. The isotope shifts between 238U-234U, 238U-235U, 238U-236U, and the hyperfine structure of 235U...

The introduction of resonance ionization using continuous wave narrowband lasers into mass spectrometry has lead to the successful development of an efficient technique for ultra trace atom determination with outstanding specifications regarding isobaric and isotopic selectivity. Due to these features this compact laser-based method is just becomin...

Employing three-step resonance ionization mass spectrometry, isotope shift measurements of atomic uranium have been performed in the 32000 36000 cm-1 and 49950 50500 cm-1 regions. On the basis of the measured isotope shifts of several autoionizing Rydberg levels, isotopic difference in the ionization potential has been determined to be +445 mK (mK=...

The fine structure intervals and isotope shift of the high 32D levels of atomic lithium were measured by two-step excitation fluorescence spectroscopy using an external cavity laser diode for the first-step excitation, using various scanning ranges over the first-step transition structure. Second-step spectra of the specific isotope pairs and fine...

An extensive energy level survey of atomic uranium was performed in the 31 300-36 400 cm-1 region using a two- or three-colour RIMS scheme; over 450 odd-parity levels, including about 150 new ones, were revealed. The J-value assignment was also performed by the method based on the J-momentum selection rule.