Nitrogen Laser Research Articles

Cathode configuration influence on low-inductance vacuum spark plasma dynamics

The results of studies of cathode configuration influence on high current low- inductance vacuum spark (HLVS) plasma dynamics are presented in this work. The research was carried out on “PION” installation using shadowgraphy method. Molecular nitrogen laser (λ = 337 nm) was used as a radiation source. It was determined that the HLVS behavior changes with the increase of number of discharges. In a fresh electrode system (less than 200 discharges) the dependence of constriction position on the discharge trigger position is observed during HLVS development. Also, high gradients of plasma density and secondary constrictions are observed. In a previously exploited electrode system (more than 300 discharges) HLVS behavior changes: plasma density gradients become less expressed, secondary constrictions disappear. In electrode systems with highly developed cathode surface plasma density gradient distribution pattern only slightly changes from discharge to discharge, e.g. the discharge becomes more stable.

Tb3+ photoluminescence in mesoporous glasses, terbium nitrate and terbium chloride hexahydrates, and coordination compounds

We have compared the intensity and shape of photoluminescence spectra of Tb3+ ions in mesoporous glasses, inorganic phosphors (terbium nitrate and terbium chloride hexahydrates), and coordination compounds (terbium benzoate, terbium o-phenoxybenzoate, and terbium terephthalate). The excitation sources used were a repetitively pulsed nitrogen laser with an emission wavelength of 337 nm and cw semiconductor light-emitting diodes with wavelengths of 369 and 385 nm. It has been shown that the highest photoluminescence intensity normalized by the percentage of terbium is offered by terbium terephthalate and terbium- doped mesoporous glass. We are thus led to conclude that introducing terbium terephthalate into the pores of mesoporous photonic glass and mesoporous photonic crystals is a promising approach for obtaining efficient laser operation in the green spectral region on the 5 D 4–7 F 5 transition of the terbium ion.

Tl10Hg3Cl16: Single crystal growth, electronic structure and piezoelectric properties

Single crystal of the ternary halide Tl10Hg3Cl16 was grown using Bridgman-Stockbarger method. For the Tl10Hg3Cl16 crystal, we have measured X-ray photoelectron spectra for both pristine and Ar+ ion-bombarded surfaces and additionally investigated photoinduced piezoelectricity. Our data indicate that the Tl10Hg3Cl16 single crystal surface is very sensitive with respect to Ar+ ion-bombardment. In particular, Ar+ ion-bombardment with energy of 3.0keV over 5min at an ion current density of 14μA/cm2 causes significant changes of the elemental stoichiometry of the Tl10Hg3Cl16 surface resulting in an abrupt decrease of the mercury content in the top surface layers of the studied single crystal. As a result of the treatment, the mercury content becomes nil in the top surface layers. In addition, the present XPS measurements allow for concluding about very low hygroscopicity of the Tl10Hg3Cl16 single crystal surface. The property is extremely important for the crystal handling in optoelectronic or nano-electronic devices working at ambient conditions. The photoinduced piezoelectricity has been explored for Tl10Hg3Cl16 depending on nitrogen (λ=371nm) laser power density and temperature.

Changes in luminescent properties of vitrified films of terbium(III) β-diketonate complex upon UV laser irradiation

Structural modifications following long-term UV irradiation with a pulsed nitrogen laser led to a decrease/increase in the luminescence intensities of vitrified films with the thickness of 8/20µm, respectively. The films were prepared from a terbium(III) β-diketonate complex. Optical spectroscopic studies revealed that these features are associated with different structures of the films. The 20µm film includes the aggregates hindering the non-radiative relaxation of the T1 states of ligands. Such a phenomenon is not observed in the 8µm film. A comparative analysis of the luminescent data indicates that the redistribution of the T1 energies of the ligands under UV modification is the predominant reason for the changes of the luminescent properties of the films.

Characteristics of the inductive nitrogen laser generation

The results of the experimental study of energy, temporal, spectral and spatial characteristics of UV inductive laser generation are presented. The study has identified a number of characteristics which demonstrate the differences between electron parameters of inductively coupled plasma and the plasma of longitudinal and transverse electrical discharges. The mechanism of simultaneous occurrence of Lewis-Rayleigh afterglow representing transitions between higher vibrational substates of B3Πg and A3∑u+ states; laser generation at C3Πu→B3Πg transition as well as the absence of IR radiation at 1st positive system typical for electrical discharge nitrogen lasers has been thoroughly researched. The major characteristic is ring shaped laser beam which size and width depend on excitation conditions. Inductive UV nitrogen laser is found to operate in ASE regime, but has a low divergence of 0.4±0.1mrad and high pulse-to-pulse stability (laser pulse deviation amplitude did not exceed 1%).

Photochemical Reactions of Aminonaphthols Caused by Laser Desorption/Ionization.

The formation of monomeric and dimeric ions of seven different aminonaphthols (ANLs) has been studied by using laser desorption/ionization (LDI) with a nitrogen laser. The positive-ion data of all the ANLs merely showed molecular ion M(·+) without protonated molecule [M+H](+), while 1-amino-2-naphthol (1,2-ANL) and 2-amino-1-naphthol (2,1-ANL) showed an intense dimeric ion [2 M-2H2O+H](+). The negative-ion data showed deprotonated molecule [M-H](-) in common, while the spectra of 1,2-ANL, 2,1-ANL and 8-amino-2-naphthol (8,2-ANL) accompanied an intense peak corresponding to negative molecular ion M(·-) and the 8,2-ANL and 4-amino-1-naphthol (4,1-ANL) accompanied dehydrogenated anion [M-2H](·-). The formation of monomeric ions was discussed from the standpoints of thermochemical properties such as ionization energy, gas-phase acidity, electron affinity, and bond dissociation energy. The formation of dimeric ions [2 M-2H2O+H](+) observed in the 1,2-ANL and 2,1-ANL could be explained by the radical combination in the amino groups. An isomer 5-amino-1-naphthol (1-ANL) did not give any dimeric ions in the both positive- and negative-ion spectra. The influence of laser fluence upon the appearance of the monomeric ions such as M(·+), [M+H](+), [M-H](-) and [M-2H](·-) of the 5,1-ANL has been examined.

Effect of ferromagnetic dopants on laser induced optical parameters of bismuth doped CaS phosphors

The effect of ferromagnetic impurities (Fe, Co, and Ni) on the laser induced optical parameters of CaS:Bi phosphors has been studied. The studies were done for the Bismuth concentration of 0.4% in CaS phosphors due to the highest value of oscillator strength as reported earlier. The studies were conducted using nitrogen laser as a excitation source in a pulse excitation mode at room temperature. Appreciable changes in the optical properties have been detected after the addition of ferromagnetic impurities in the CaS phosphor doped with bismuth. The nature of the multiple exponential decays remains the same even after the addition of ferromagnetic impurities in the present case of bismuth-doped phosphors which is in agreement with the earlier work reported on other dopants in sulfide type phosphors. As ferromagnetic impurities enhanced the optical parameters of CaS phosphors appreciably, these studies shows that they can be used to control the transition probability and the corresponding optical parameters.

Influence of La3+ ions on δ-Bi1−xLaxB3O6 powders structure and photo-induced optical properties of their polymer composites

Polycrystalline powder samples of orthorhombic δ-Bi1−xLaxB3O6 (where x=0.025–0.075), synthesized by means of polymeric precursor method, were incorporated into photopolymer polyvinyl alcohol matrix. The composites were fabricated by simultaneous DC-electric field alignment and UV solidification using a 337nm wavelength nitrogen laser. Optically stimulated EO effect in δ-Bi1−xLaxB3O6 was studied under the illumination of 20ns Nd:YAG bicolor laser beams at 1064nm and 532nm wavelengths. The main role of the La3+ ions content in δ-Bi1−xLaxB3O6 on the electrooptical efficiency is here clearly observed. The temperature dependence of the photoinduced EO is also investigated.

Abstract 2011: Feasibility of serum proteomic companion diagnostic (CDx) test development on the microflex LT platform

Abstract Clinical oncology assays using mass spectrometry have exclusively been run on instrument platforms designed for use in research laboratories. Here, we report on the use of a bench-top MALDI-TOF mass spectrometer (MS) to run a serum proteomic Laboratory Developed Test (LDT), VeriStrat®. A number of previous studies have shown that this assay measures a serum proteomic fingerprint using MALDI-TOF MS which, following spectral acquisition and data processing, classifies advanced non-small cell lung cancer (NSCLC) patients into treatment categories. An extension of VeriStrat, BDX004, is currently under development as part of a global, randomized, double-blind Phase 2 clinical study, FOCAL. BDX004 will be used prospectively to select previously untreated, EGFR mutation-positive patients with advanced NSCLC to receive one of two treatments: (1) the combination of ficlatuzumab (a humanized monoclonal antibody against hepatocyte growth factor) and an EGFR tyrosine kinase inhibitor (TKI), or (2) an EGFR TKI with placebo. For the development of BDX004 as a companion diagnostic (CDx), we have included the microflex™ LT (LT), a component of Bruker's MALDI Biotyper CA system, which was granted FDA clearance for the identification of Gram negative bacteria. In the present study, we evaluated the LT platform through comparative studies with other MALDI-TOF instruments (autoflex™ III and autoflex SPEED) utilizing samples from patients previously diagnosed with NSCLC. In summary, we found that under common laboratory procedures the LT produces results equivalent to research grade MALDI-TOF MS instrumentation. In initial studies, the microflex LT showed similar resolution (R > 600 at 6632.1 m/z) and sensitivity (S/N ≥ 50 with 500 fmoles BSA in 100 laser shots) performance parameters as the autoflex series research instruments (R > 800 at 6632.1 m/z and S/N ≥ 50 with 500 fmoles BSA in 250 laser shots). The LT was qualified with several independent sample sets [n = 4 (8 replicates; 2000 spectra/replicate); n = 67 (3 replicates; 2000 spectra/replicate) and n = 20 (3 replicates; 2000 spectra/replicate)]. In these studies, the LT achieved 100%, >97%, and 100% concordance with reference data sets previously acquired on the autoflex platforms. As expected, due to the lower laser repetition rate of the LT's nitrogen laser, the acquisition speed was slower on the LT as compared to the autoflex instruments by a factor of two. However, the slower acquisition speed is partially compensated for with increased sensitivity, which is particularly evident in the reference sample mass spectra which have signal-to-noise ratios ∼1.5 greater than those acquired on the autoflex platform. Based on these results, the microflex LT appears to be suitable for measurement of serum proteomic profiles in NSCLC and suggests that the inclusion of the microflex LT in CDx test development has the potential to expand the utility of MALDI-based testing in the clinic. Citation Format: Nicholas Dupuis, Jamie Chang, Maximillian Steers, Zhigang Weng, Jeno Gyuris, Gary Pestano. Feasibility of serum proteomic companion diagnostic (CDx) test development on the microflex LT platform. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2011. doi:10.1158/1538-7445.AM2015-2011

IGBT-based switching modules for laser applications

This paper presents the design of IGBT-based switching modules for a nitrogen gas laser. First, the CC-topology, which drives the laser, is discussed and simulated. Simple models of the laser tube and the switch are presented. The comparison of the simulation with experimental data shows good accuracy. The results are used to discuss the influence of the parasitic inductance and the capacitances on the laser tube behavior. Cascades with an 11-cell series connection based on different IGBT-chips (1700 V and 1200 V) have been built up and measured. The focus of the design is the high speed synchronous switching of all switching cells. Therefore, the design of a pulse transformer-based gate drive and a symmetrization network is presented. The module equipped with the four parallel 1200 V/35 A-IGBTs per cell produces the highest switching power. Among the variants, the switch peak current is up to 700 A at blocking voltages of up to 13.2 kV in the real environment of the nitrogen laser. The switch current slope reaches up to 30 A/ns and the laser tube current up to 1.8 kA. The variant with 1200 V/35 A-IGBTs produces an output energy which is about 15 % higher compared to the former MCT-based switch. Furthermore, a modified CCtopology for lower blocking voltage is investigated. The IGBT-based switches are able to replace the MCT-switches in this application. Between the different switches a tradeoff has to be done between high output energy and the effort for the assembly.

Synthesis, optical properties, laser activity and DFT studies of (E,E)-2,5-bis[2-(1-methyl-1H-pyrrole-2-yl)-vinyl]pyrazine (BMPVP)

Abstract The optical absorption and emission properties of (E,E)-2,5-bis[2-(1-methyl-1H-pyrrole-2-yl)-vinyl] pyrazine (BMPVP) have been studied in different solvents. The BMPVP dye shows strong solvatochromic emission upon changing the solvent polarity from nonpolar to polar; indicating that the emission state is of intramolecular charge transfer (ICT) character. The solvent effect on the spectral properties such as singlet absorption, molar absorptivity, oscillator strength and fluorescence quantum yield of BMPVP have been studied in detail. The Lippert-Mataga and Reichardt correlations were used to estimate the difference between the excited and ground state dipole moments (Δm). Electronic excited states in different solvents were investigated using TD-DFT. The intramolecular charge transfer was analyzed by the NBO technique. The BMPVP dye is highly photostable in polar protic and polar aprotic solvents, while it displays photodecomposition in chloromethane solvents via formation of a contact ion pair. The photochemical quantum yield depends on the electron affinity of the solvent. A solution of (8 × 10−5 M) BMPVP in THF, dioxane, CH3CN or DMSO gives laser emission when pumped by a nitrogen laser pulse (λex = 337.1 nm) of 800ps duration and 1.48 mJ pulse energy. The BMPVP dye displays fluorescence quenching by colloidal silver nanoparticles (AgNPs) in ethanol with a fluorescence quenching rate constant of 1.40 × 109 M−1. The fluorescence data revealed that the dynamic quenching and the energy transfer play major roles in the fluorescence quenching mechanism.

Backward nitrogen lasing actions induced by femtosecond laser filamentation: influence of duration of gain

We experimentally investigate generation of backward 357 nm N2 laser in a gas mixture of N2/Ar using 800 nm femtosecond laser pulses, and examine the involved gain dynamics based on pump-probe measurements. Our findings show that a minimum duration of gain in the excited N2 molecules is required for generating intense backward nitrogen lasers, which is ∼0.8 ns under our experimental conditions. The results shed new light on the mechanism for generating intense backward lasers from nitrogen molecules, which are highly in demand for high sensitivity remote atmospheric sensing application.

Spectroscopic investigation, photophysical parameters and DFT calculations of 4,4′-(1E,1′E)-2,2′-(pyrazine-2,5-diyl)bis(ethene-2,1-diyl)bis(N,N-dimethylaniline) (PENDA) in different solvents

A comprehensive investigation on the photophysics of a π-conjugated potential push–pull chromophore system 4,4′-(1E,1′E)-2,2′-(Pyrazine-2,5-diyl)bis(ethene-2,1-diyl)bis(N,N-dimethylaniline) (PENDA) has been carried out spectroscopically. The optical absorption and emission properties of this molecule have been studied in different solvents. The molecule PENDA shows strong solvatochromic emission upon changing the solvent polarity from nonpolar to polar; indicating that emission state is of intramolecular charge transfer (ICT) character. The solvent effect on the spectral properties such as singlet absorption, molar absorptivity, oscillator strength, dipole moment and fluorescence quantum yield of PENDA have been studied in detail. Lippert–Mataga and Reichardt correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). Ground and electronic excited states geometric optimizations were performed using density functional theory (DFT) and time-dependent density functional theory (TDDFT), respectively, with the Gaussian 09 package. A solution of (8×10−5M) PENDA in THF, dioxane, CH3CN and CHCl3 gives laser emission when pumped by a nitrogen laser pulse (λex=337.1nm) of 800ps duration and 1.48mJ pulse energy. PENDA dye displays fluorescence quenching by colloidal silver nanoparticles (Ag NPs) in ethanol. The fluorescence data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching mechanism.

Theory of a filament initiated nitrogen laser

We present the theoretical model for a single-pass, discharge-type standoff nitrogen laser initiated by a femtosecond filament in nitrogen gas. The model is based on the numerical solution of the kinetic equation for the electron energy distribution function self-consistently with balance equations for nitrogen species and laser equations. We identify the kinetic mechanisms responsible for a buildup of population inversion in the filament afterglow plasma and determine the dependence of population inversion density and the parameters of nitrogen lasing at a 337 nm wavelength corresponding to the transition between the C3Πu (v = 0) excited and the X1Σg (v = 0) ground electronic states in a nitrogen molecule on the polarization and wavelength of the driver laser pulse used to produce the filament. We show that population inversion is achieved on an ultrafast time scale of ≈10 ps and decays within the time: <100 ps. We derive the low-signal gain 2.2 cm−1 for lasing from a circularly polarized 0.8 μm near-IR filament and 0.16 cm−1 for a linearly polarized 4 μm mid-IR filament. The results of the numerical simulations demonstrate good quantitative agreement with the experimental measurements.

Photophysical, photochemical and laser behavior of some diolefinic laser dyes in sol–gel and methyl methacrylate/2-hydroxyethyl methacrylate copolymer matrices

Abstract The photophysical properties such as singlet absorption, molar absorptivity, fluorescence spectra, dipole moment, fluorescence quantum yields, fluorescence lifetimes and laser activity of 1,4-bis (β-Pyridyl-2-Vinyl) Benzene (P 2 VB), 2,5-distyryl-pyrazine (DSP) and 1,4-bis(2-methylstyryl)benzene(MSB) diolefineic laser dyes have been measured in different restricted hosts. (P 2 VB), (DSP) and (MSB) are embedded in transparent sol–gel glass and a copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) media. The absorption and fluorescence properties of these laser dyes in sol–gel glass matrices are compared with their respective properties in copolymer host. The photostability of these laser dyes in sol–gel glass and (MMA/HEMA) copolymer samples are measured in terms of half-life method (using nitrogen laser 337.1 nm in pumping), as the number of pulses necessary to reduce the dye laser intensity to 50% of its original value. The gel laser materials show improved photostability upon pumping by nitrogen laser compared with those in organic polymeric host matrix.

Design and construction of prototype transversely excited atmospheric (TEA) nitrogen laser energized by a high voltage electrical discharge

The present study reports design and construction, of a prototype of Transversely Excited Atmospheric (TEA) nitrogen laser, and a high voltage power supply to excite N2 gas in air, while air is used as an active lasing medium. A Blumlein line discharge circuit is used for operation of this laser. The high voltage is generated by a fly back transformer based power supply varying from 10kV to 20kV. The wavelength (337.1nm) of TEA nitrogen laser is measured employing a standard commercial spectrometer and the laser output energy of 300μJ is measured from the constructed system. Different parameters such as beam profile, laser output spectrum, laser efficiency, and variation of E/P (Electrical field/Pressure) value with respect to input voltage and electrodes separations are studied in order to optimize the overall operational efficiency of present nitrogen laser. The analysis of the high voltage prototype appeared in this designed source has also been made and described in this paper.

Laser desorption ionization time-of-flight mass spectrometry of Ge-As-Te chalcogenides.

Ge(x)As(y)Te(z) glasses have a broad window of optical transparency and high refractive index which make them promising for applications in the infrared region. The aim of this work is to reveal structural motifs which could be present during the fabrication of Ge-As-Te thin films by plasma deposition techniques; such knowledge is important for the optimization of thin film growth. Mass spectra were acquired using a laser desorption ionization time-of-flight (LDI-TOF) mass spectrometer equipped with a nitrogen laser (337 nm) coupled with a quadrupole ion trap, and recorded in positive and negative ion reflectron modes. XRD, SEM (EDX) and Raman spectroscopy were also used for the characterization of Ge-As-Te bulk or powdered samples. Bulk Ge(x)As(y)Te(z) samples (x = 10-20%, y = 20-60%, z = 30-70%) were synthesized. LDI-MS of Ge-As-Te powders provided evidence for the formation of both positively and negatively charged clusters, whose stoichiometry was determined as Te(n)(+/-) (n = 1-4), Te(5)(+), binary AsTe(n)(+/-) (n = 1-3), GeTe(n)(+/-) (n = 1-3), As(2)Te(+/-), As(2)Te(3)(+), As(3)Te(+), AsTe(4) (+), Ge(2)H(6) (+/-), ternary GeAsTe(+), GeAsTe(2)(+/-), GeAsH5 (+), GeAsH(6)(+), GeAsH(12)(+), and tertiary GeAsTeH(5)(-), GeAsTeH(8)(-), GeAsTe(2)H(3) (+/-). The local structure of Gex Asy Tez materials is at least partly different from that of species identified in plasma by mass spectrometry, as deduced from Raman scattering spectroscopy analysis. However, LDI-TOFMS was found to be a suitable technique for the partial structure characterization of Ge-As-Te bulk samples and especially for the identification of the structural motifs present in the plasma during the preparation of the corresponding thin films.

Modeling of the Inductance of a Blumlein Circuit Spark Gap

In this paper we present an analysis of the time-varying inductance in the spark gap of a Blumlein circuit. We assume several mathematical expressions to describe the inductance and compare theoretical and computational calculations with experimental results. The time-varying inductance is approximated by a constant, a straight line and two parables which differ in their concavity. This is the first time to our knowledge, in which the time-varying ignition inductance of a nitrogen laser is modeled.

The Application of Nitrogen Laser on Extraction of Uranium in The Long Life of High Level Radioactive Liquid Waste Using TBP-Kerosene Solvent

The radionuclide of uranium (U) is major radionuclide contained in the long life of high level radioactive liquid waste (HLLW) generated from reprocessing of spent nuclear fuel. The radioactive waste have to be treated to ready for long term disposal. Separation of the U at high efficiencies greatly lowers the volume of the long life alpha radioactive waste to be disposed and decreases the hazard level of the waste. The technology assessment of selective separation of U was carriedout as alternative and strategy for HLLW management in the future. The selective separation technology of U from fission products at very high efficiencies was developed by the extraction process using TBP-kerosene solvent and increasing the separation by exposure of nitrogen (N2) laser radiation at wavelength 337.1 nm. In the extraction process for simulation waste containing U and Zr in 5 M HNO3 (Zr as one of fission product which difficult to be separated from U) using 30 % TBP-kerosene solvent and by exposure of nitrogen laser radiation shows that increasing of distribution coefficient of U (Kd U) can obtains 135 % and increasing of separation factor of U and Zr (SF(U/Zr)) is 189 %. The increasing of Kd U using N2 laser higher than using CO2 laser (at the wave-number 944 cm-1 ) which increase of Kd U only 100 %. In Indonesia, assessment for adaptation of the separation technology by extraction for separation of U process using 30 % TBP-kerosene solvent should be carried-out as alternative for treatment the HLLW generated from 99Mo radioisotope production and from post irradiation examination of nuclear fuel.

Utilization of Coal Fly Ash as CO Gas Adsorbent

The radionuclide of uranium (U) is major radionuclide contained in the long life of high level radioactive liquid waste (HLLW) generated from reprocessing of spent nuclear fuel. The radioactive waste have to be treated to ready for long term disposal. Separation of the U at high efficiencies greatly lowers the volume of the long life alpha radioactive waste to be disposed and decreases the hazard level of the waste. The technology assessment of selective separation of U was carriedout as alternative and strategy for HLLW management in the future. The selective separation technology of U from fission products at very high efficiencies was developed by the extraction process using TBP-kerosene solvent and increasing the separation by exposure of nitrogen (N2) laser radiation at wavelength 337.1 nm. In the extraction process for simulation waste containing U and Zr in 5 M HNO3 (Zr as one of fission product which difficult to be separated from U) using 30 % TBP-kerosene solvent and by exposure of nitrogen laser radiation shows that increasing of distribution coefficient of U (Kd U) can obtains 135 % and increasing of separation factor of U and Zr (SF(U/Zr)) is 189 %. The increasing of Kd U using N2 laser higher than using CO2 laser (at the wave-number 944 cm-1 ) which increase of Kd U only 100 %. In Indonesia, assessment for adaptation of the separation technology by extraction for separation of U process using 30 % TBP-kerosene solvent should be carried-out as alternative for treatment the HLLW generated from 99Mo radioisotope production and from post irradiation examination of nuclear fuel.