Iodine Laser Research Articles

Influence of the magnetic field on the emission of hot electrons and ions from ablative plasma produced from a disc-coil target irradiated by the 3rd harmonic of the PALS iodine laser

Abstract Experimental and theoretical study of plasma processes affected by strong laser generated magnetic fields is reported. The PALS laser system operating at 3ω (438.5 nm) delivered intensities up to 1×1016 W/cm2 on targets. By using a special target system consisting of a Cu foil connected to a sub-mm coil, magnetic fields up to the level of 10 T were generated. This is 1.4 times higher than the field generated with a 1.315 μm (1ω) laser beam at a comparable intensity. We found that these fields were sufficiently strong to modify plasma blow-off from the foil which resulted in the changed expansion dynamics and increased energy of hot electrons by 20-40% compared to the plasma unaffected by the magnetic field. To obtain complementary experimental data, a complex diagnostic system was used enabling the visualization of the plasma expansion process both in visible light (3-frame composite interferometry) and in the soft X-ray region (4-frame pinhole X-ray camera) together with measurements of the hot electron parameters using two-dimensional imaging of the Kα line emission from the Cu target and electron spectroscopy. Experimental data obtained from the angular distribution of electron energy spectra were used for three-dimensional (3D3V) numerical PIC simulations using a modified EPOCH code. By including interactions between ions, protons, hot and thermal electrons in forward and backward propagating particles, the effects of the magnetic field on the flux of hot electrons were visualized and compared with the experiment. The PIC simulation confirmed that the interaction of the hot electron flux with the magnetic field generated by the target-coil system leads to an increased flux energy. However, this increase is accompanied by increased complexity of the spatial structure and heterogeneity of the flux as well as its angular divergence.

Study of radiative shocks using 2D interferometry and XUV spectroscopy

We report new experimental results on radiative shocks obtained in Xenon and Argon in gas cells at two different pressures below 1 bar. These shock waves are generated by the interaction of the PALS iodine laser on a CH–Au foil with a typical velocity in the range of 50–100 km/s depending on the variable laser intensity, pressure, and gas. Attention is paid to the morphology and the dynamics of the radiative precursor over large time scales up to 30 ns, using 2D sub-picosecond visible interferometry, illustrating the complex interplay of hydrodynamic and radiation absorption for different initial conditions. The comparison between 1D and 2D simulations confirms the role played by lateral radiative losses in the ionization wave and the necessity of state-of-the-art integrated opacities. This study is complemented by the first XUV analysis of the shock emission between 5 and 20 nm obtained with a grating spectrometer, with line identification, which is compatible with the ionization stages deduced from interferometry and simulations.

A New Method for Magnetic Gain Modulation of Chemical Oxygen Iodine Laser Based on Flat-Top Pulsed Magnetic Field

A New Method for Magnetic Gain Modulation of Chemical Oxygen Iodine Laser Based on Flat-Top Pulsed Magnetic Field

LINGUAL PHRENECTOMY WITH THE USE OF IODINE LASER IN INFANT PATIENT

Objective: to approach the surgical process better known as frenectomy to solve Ankyloglossia, a condition that restricts the movement of the tongue. This change is characterized as congenital, consisting of fibrous connective tissue, which affects the tip of the tongue to the floor of the mouth. Case report: A 3-year-old female patient attended the Children’s Dental Clinic at the University Center of the State of Pará, presenting the Linguinha Test report proving the ankyloglossia. In the preoperative period, Ibuprofen 50mg / ml was prescribed, 18 drops 1 hour before the surgical procedure and 6/6 hours after surgery for 2 days. However, surgery was performed for the better development of the patient using high intensity iodine laser therapy ((2300mW-0: 00-continuous Surgery-DMC), successfully finishing the procedure. After 24h and 48h, the laser was applied low intensity (66 NM, 100 mW, 2J-DMC) to enhance the benefit of iodine laser. Conclusion: The present case indicates the use of the laser as a safe and effective technique for performing lingual frenectomy in a child patient.

Strongly magnetized plasma produced by interaction of nanosecond kJ-class laser with snail targets

Magnetized plasma studies are necessary for many applied studies, including laser-driven inertial fusion, modeling astrophysically relevant phenomena, and innovative industrial and medical applications. An interesting method of generating highly magnetized plasma can be based on the interaction of a laser with spiral-shaped cavity (snail-like) targets. A target shaped in this way can represent the central area of a spherical pellet that is not irradiated radially, but rather through an entrance hole allowing the laser beam to almost impact its inner surface tangentially (Pisarczyk et al 2018 Sci. Rep. 8 17 895). In the reported experiment, snail targets of various diameters were irradiated by linearly or circularly polarized radiation of a Prague asterix laser system (PALS) iodine laser delivering ∼500 J, 350 ps and 1.315 μm pulses on targets. Three-frame complex interferometry demonstrated that plasma is generated on the entire inside and outside surfaces of the snail target, starting from the very beginning of the laser–target interaction. The time-resolved records of the magnetic field and the electron density distribution inside and outside the snail target characterize the changes in the structure of the magnetized plasma. Inside the target, the magnetic field survives long after the termination of the laser–matter interaction, namely longer than 10 ns. Compared to a circularly polarized laser pulse, the irradiation of targets with a p-polarized beam increases both the emission of hot electrons (HEs) and the intensity of the magnetic field. The emission of HEs is not isotropic, and their energy distribution cannot be characterized by a single temperature.

Singlet Molecular Oxygen: from COIL Lasers to Photodynamic Cancer Therapy.

Translation of experimental techniques from one scientific discipline to another is often difficult but rewarding. Knowledge gained from the new area can lead to long lasting and fruitful collaborations with concomitant development of new ideas and studies. In this Review Article, we describe how early work on the chemically pumped atomic iodine laser (COIL) led to the development of a key diagnostic for a promising cancer treatment known as photodynamic therapy (PDT). The highly metastable excited state of molecular oxygen, a1Δg, also known as singlet oxygen, is the link between these disparate fields. It powers the COIL laser and is the active species that kills cancer cells during PDT. We describe the fundamentals of both COIL and PDT and trace the development path of an ultrasensitive dosimeter for singlet oxygen. The path from COIL lasers to cancer research was relatively long and required medical and engineering expertise from numerous collaborations. As we show below, the knowledge gained in the COIL research, combined with these extensive collaborations, has resulted in our being able to show a strong correlation between cancer cell death and the singlet oxygen measured during PDT treatments of mice. This progress is a key step in the eventual development of a singlet oxygen dosimeter that could be used to guide PDT treatments and improve outcomes.

Open-Path Atmospheric Transmission of Diode-Pumped Alkali Lasers in Maritime and Desert Environments.

A tunable diode laser absorption spectroscopy (TDLAS) device has been developed to study long-path atmospheric transmission near diode pumped alkali laser (DPAL) emission wavelengths. By employing a single aperture and retro reflector in a mono-static configuration, the noise associated with atmospheric and platform jitter were reduced by a factor of ∼30 and the open-air path length was extended to 4.4 km and over a very broad spectral range, up to 120 cm-1. Water vapor absorption lines near the rubidium (Rb) and cesium (Cs) variants of the DPAL near 795 and 894 nm, oxygen lines near the potassium (K) DPAL near 770 nm, and water vapor absorption in the vicinity of the neodymium-doped yttrium aluminum garnet (Nd:YAG) laser 1.064 μm and chemical oxygen iodine laser (COIL) 1.3 μm lines were studied. The detection limit for path absorbance increases from ΔA = 0.0017 at 100 m path length to 0.085 for the 4.4 km path. Comparison with meteorological instruments for maritime and desert environments yields agreement for the 2.032 km path to within 1.5% for temperature, 4.5% for pressure, and 5.1% for concentration, while agreements for the 4.4 km path are within 1.4% for temperature, 7.7% for pressure, and 23.5% for concentration. An intra cavity output spectroscopy (ICOS) device was also used as a spectral reference to verify location of atmospheric lines. Implications of TDLAS collection system design on signal-to-noise (S/N) are discussed as well as the effect of path turbulence on baseline noise and inform the selection of the DPAL variant least affected by molecular absorption.

Uncertainty evaluation of data acquisition and analysis system relevant to infrared flowing medium laser

In flowing medium Chemical Oxygen Iodine Laser (COIL), Singlet oxygen is produced by the exothermic reaction of basic hydrogen peroxide solution and chlorine gas. It pumps the iodine and lasing process takes place by stimulated emission. Laser power is extracted using cavity. Development of customized data acquisition system is essential for measurements and analysis of both fundamental (temperature, pressure, level) as well as derived parameters (lasing medium concentration, flow rates of gases and laser power). The focus of the present paper is to dwell on uncertainty evaluation of a complex gas laser source in terms of ascertaining influences of primary/fundamental variables and corresponding derived parameters along with manner of uncertainty propagation. The study facilitates determining the variables with most significant impact on system performance, critical form point of view from optimal functioning of large-scale systems. This enables prediction of overall system uncertainty potentially extendable to other similar laser systems involving subsystems with mutual interdependencies together being distributed over a significantly large laboratory space. The relative combined uncertainty is computed to be 8.3%. The methodology shows significant potential for true decision-making and control of realistic gas laser source operation using developed 150 channel Data Acquisition and Analysis System (DAAS).

Morphology of Meteorite Surfaces Ablated by High-Power Lasers: Review and Applications

Under controlled laboratory conditions, lasers represent a source of energy with well-defined parameters suitable for mimicking phenomena such as ablation, disintegration, and plasma formation processes that take place during the hypervelocity atmospheric entry of meteoroids. Furthermore, lasers have also been proposed for employment in future space exploration and planetary defense in a wide range of potential applications. This highlights the importance of an experimental investigation of lasers’ interaction with real samples of interplanetary matter: meteorite specimens. We summarize the results of numerous meteorite laser ablation experiments performed by several laser sources—a femtosecond Ti:Sapphire laser, the multislab ceramic Yb:YAG Bivoj laser, and the iodine laser known as PALS (Prague Asterix Laser System). The differences in the ablation spots’ morphology and their dependence on the laser parameters are examined via optical microscopy, scanning electron microscopy, and profilometry in the context of the meteorite properties and the physical characteristics of laser-induced plasma.

Frequency stabilization of a 739 nm laser to an I2 spectrum for trapped ytterbium ions

We report on the frequency stabilization of a 739 nm Ti:sapphire laser to a hyperfine component of the 127 I 2 B(1)-X(11) P(70) transition using acousto-optic modulation transfer spectroscopy. A frequency stability of 3.83 × 10 − 11 around 13 s averaging time is achieved when the laser frequency is stabilized. The observed hyperfine transition of the molecular iodine is an ideal frequency reference for locking the lasers used in experiments with trapped ytterbium ions, since its second-harmonic frequency is the 2 S 1 2 − 2 P 1 2 transition of the ytterbium ion at 369.5 nm. By investigating the line broadening effects due to the iodine vapor pressure and laser power, the locking is optimized to the theoretical signal to noise ratio of this iodine transition.

Phase combining of radiation from a two-channel explosively pumped photodissociation iodine laser with an SBS mirror

A two-channel double-pass iodine explosively pumped photodissociation laser (EPPL) with an explosively pumped master oscillator (MO) and an SBS mirror is studied. The radiation source, determined by an aperture 6 mm in diameter, through which the radiation from MO enters the turbulent surface air path, is located at a distance of 2.5 km from the amplifier unit input. An SBS mirror with a kinoform raster of microlenses is used to compensate for the amplifier and path optical inhomogeneities and to match the phases in the EPPL channels. The energy and spatial characteristics of the EPPL output radiation are studied experimentally and numerically. Good agreement is obtained between the experimental and calculated distribution of the energy density of the output EPPL radiation in the plane of the MO aperture, which is a pattern of interference between the two channels. The maximum energy density in the aperture plane is by more than 4 times greater than in the case of a single-channel EPPL.

Real Time Flow Control System for Precise Gas Feed in COIL

This paper reports development of a real time flow control system for precise, controlled and uniform gas feed to a flowing medium Chemical Oxygen Iodine Laser (COIL). The optimal operation of this prominent laser depends upon the desired supply of gas constituents such as nitrogen (N2), chlorine (Cl2) and iodine (I2) to achieve adequately mixed laser gas. The laser also demands real time variation of flow rates during gas constituent transitions in order to maintain stabilized pressures in critical subsystems. Diluent nitrogen utilized for singlet oxygen transport is termed as primary buffer gas and that for iodine transport is termed as secondary buffer gas (with main and bypass components). Also, nitrogen in precise flows is used for mirror blowing, nozzle curtain, cavity bleed and diffuser startup. A compact hybrid data acquisition system (Hybrid DAS) for precise flow control using LabVIEW 2014 platform has been developed. The supported flow ranges may vary from few mmole.s-1 to few hundred mmole.s-1. The estimated relative uncertainty in the largest gas component i.e. primary buffer gas feed is nearly 0.7%. The implementation of in-operation variation using flow ramp enables swift stabilization of singlet oxygen generator pressures critical for successful COIL operation. The performance of Hybrid DAS is at par with fully wired DAS providing the crucial benefit of remote field operation at distances of nearly 80m in line of sight and 35m with obstacles

Data Acquisition System for Chemical Iodine Generation Suitable for Flowing Medium Chemical Oxygen Iodine Laser

Development of infrared flowing medium lasers needs to be envisaged in a manner that practical aspects such as system compactness, short readiness time, low system size, weight and power are met to make them field deployable. In this context, the critical aspect of in-situ production of lasing species (Iodine) in Chemical Oxygen Iodine Lasers (COIL), one of the most potent flowing medium lasers, has been investigated. The paper dwells on chemical generation of iodine and its precise flow and parameter control by implementing a customised Data Acquisition System (DAS). Iodine is generated in a chemical reaction of Cuprous Iodide (CuI) with chlorine. This is achieved by precisely controlled flow of chlorine diluted with a carrier gas (N2 ) in a ratio of 1:2. DAS includes regulated gas feed, accurate thermal stabilisation, relevant diagnostics and implementation of necessary safety interlocks in a real time operation scenario for establishing the system efficacy and scalability. The studies have demonstrated chemically generated iodine flow rate of ~ 1.2 mmol.s-1 for Cl2 flow rate of ~3 mmol.s-1 all measured in real time using the developed DAS with a conversion efficiency of 80%. Developed I2 supply system has potential to deliver iodine on demand with required flow rates, measurement uncertainty of ~ 4.5 percent and advantages of smaller specific weight and size with reduced system readiness time and electrical power supply using DAS system with adequate safety interlocks.

Three dimensional transient analysis of bubble dynamics in centrifugal bubble singlet oxygen generator for scalable COIL

Chemical Oxygen Iodine Laser (COIL) is the shortest wavelength (1.315 μm) chemical laser employing singlet oxygen molecules as the pumping species and iodine atoms as lasing species. Singlet Oxygen Generator (SOG) is essentially the heart of this laser device which is basically a gas–liquid phase chemical reactor. SOG facilitates the reaction between a basic hydrogen peroxide solution (BHP, H2O2 + KOH) and chlorine gas to produce singlet oxygen molecules. Centrifugal Bubble Single Oxygen Generator (CBSOG) is a potential candidate for an alternative SOG with better operating conditions for high throughput and high power COIL systems. In CBSOG Chlorine gas is bubbled through a layer of BHP solution and the required reaction takes place at the gas–liquid interface of the formed bubbles under high speed rotation of the chamber for gravity independent operation. The performance of this device largely depends on the bubble formation characteristics and their traverse inside the BHP layer. The aim of this paper is to present the numerical analysis of the mechanics of bubble formation, detachment and movement in the BHP layer for different operating parameters as applicable to COIL. The determination of conditions for the transition from bubbling to the jetting regime at different centrifugal accelerations of high magnitude (G ∼ 204 g, 306 g & 387 g) with low liquid column thickness (∼6–8 mm) operating under low pressure (∼100 torr) is another point of focus. The Volume of Fluid (VOF) method has been used for the 3-D transient interface tracking between the phases. This paper also compares the simulation results for various gas flow rates and centrifugal accelerations with select experimental results reported elsewhere showing reasonably good agreement.

Shock dynamics and shock collision in foam layered targets

Abstract We present an experimental study of the dynamics of shocks generated by the interaction of a double-spot laser in different kinds of targets: simple aluminum foils and foam–aluminum layered targets. The experiment was performed using the Prague PALS iodine laser working at 0.44 μm wavelength and irradiance of a few 1015 W/cm2. Shock breakouts for pure Al and for foam-Al targets have been recorded using time-resolved self-emission diagnostics. Experimental results have been compared with numerical simulations. The shocks originating from two spots move forward and expand radially in the targets, finally colliding in the intermediate region and producing a very strong increase in pressure. This is particularly clear for the case of foam layered targets, where we also observed a delay of shock breakout and a spatial redistribution of the pressure. The influence of the foam layer doped with high-Z (Au) nanoparticles on the shock dynamics was also studied.

Development of the Long Duration Chemical Oxygen Iodine Laser

The development of Chemical Oxygen Iodine Laser (COIL) with a long duration is of important for the industry application of COIL. The aim of this research was to achieve a stable and longtime COIL operation. A systemic study of output power stability was performed from three aspects: influencing factors, solutions, and experimental verification. A 100s duration COIL in the power level of 5kW was firstly developed in our laboratory. The fluctuant range of power is about 5%, and the filling factor f (Imin/Imax) is about 0.4.

A Prototype of Electric Discharge Gas-Flow Oxygen–Iodine Laser: 2. Simulation of the Parameters of the Active Medium Formed in a Gas-Flow Slab RF Discharge in O2 : He : CF3I Mixtures

A calculated analysis of the possibility of achieving the generation in a gas-flow electric discharge oxygen–iodine laser when it is excited by a transverse slab RF discharge for various conditions of passing of the CF3I : O2 : He gas mixture components along the gas duct was carried out: in subsonic flow without cooling the channel walls and with cooling of various sections of the channel walls down to 100 K. To do this, reactions involving CF3I iodide and the photon balance equation were added to the model. It was assumed that the active medium was formed in two ways: (i) all components of the gas mixture simultaneously passed through the RF excitation zone; (ii) oxygen and helium passed through the RF discharge zone, and the iodide-containing component (CF3I : He mixture) was introduced through an injector located downstream gas flow from the discharge zone. Calculations have shown that it is possible, in principle to achieve the laser generation mode under conditions implemented on the experimental setup.

Hot electron retention in laser plasma created under terawatt subnanosecond irradiation of Cu targets

Laser plasma created by intense light interaction with matter plays an important role in high-energy density fundamental studies and many prospective applications. Terawatt laser-produced plasma related to the low collisional and relativistic domain may form supersonic flows and is prone to the generation of strong spontaneous magnetic fields. The comprehensive experimental study presented in this work provides a reference point for the theoretical description of laser-plasma interaction, focusing on the hot electron generation. It experimentally quantifies the phenomenon of hot electron retention, which serves as a boundary condition for most plasma expansion models. Hot electrons, being responsible for nonlocal thermal and electric conductivities, are important for a large variety of processes in such plasmas. The multiple-frame complex-interferometric data providing information on time resolved spontaneous magnetic fields and electron density distribution, complemented by particle spectra and x-ray measurements, were obtained under irradiation of the planar massive Cu and plastic-coated targets by the iodine laser pulse with an intensity of above 1016 W cm−2. The data shows that the hot electron emission from the interaction region outside the target is strongly suppressed, while the electron flow inside the target, i.e. in the direction of the incident laser beam, is a dominant process and contains almost the whole hot electron population. The obtained quantitative characterization of this phenomenon is of primary importance for plasma applications spanning from ICF to laser-driven discharge magnetic field generators.

Nonadiabatic Electronic Energy Transfer in the Chemical Oxygen-Iodine Laser: Powered by Derivative Coupling or Spin-Orbit Coupling?

Derivative couplings near a conical intersection and spin-orbit couplings between different spin states are known to facilitate nonadiabatic transitions in molecular systems. Here, we investigate a prototypical electronic energy transfer process, I(2P3/2) + O2(a1Δg) → I(2P1/2) + O2(X3Σg-), which is of great importance for the chemical oxygen-iodine laser. To understand the nonadiabatic dynamics, this multistate process is investigated in full dimensionality with quantum wave packets using diabatic potential energy surfaces coupled by both derivative and spin-orbit couplings, all determined from first principles. A near quantitative agreement with structural, energetic, and kinetic measurements is achieved. Detailed analyses suggest that the nonadiabatic dynamics is largely controlled by derivative coupling near conical intersections, which leads to a small effective barrier and hence a slightly positive temperature dependence of the rate coefficient. The new results should extend our understanding of energy transfer, provide a quantitative basis for numerical simulations of the chemical oxygen-iodine laser, and have important implications in other electronic energy transfer processes.

Hybrid Data Acquisition and Analysis System for Flowing Medium Lasers

The medium gas lasers involves in-situ generation of the lasing medium, hence are associated with several complex processes including mixing of pumping and lasing species, energy exchange between the species, heat generation during reaction and its influence on the flow domain to list a few. Thus, the characterisation of lasing medium, condition of operation of individual critical subsystems and corresponding phenomenon thereof is essential in real time. It is here that a customised data acquisition and analysis system (DAAS) plays a key role. The paper dwells on the realisation of a customised hybrid DAAS with a master-slave architecture, which is portable and provides remote system operation. The noteworthy aspects of the developed DAAS include capability to handle close to 150 channels [64 analog input, 64 digital output, 5 analog output and 17 digital input] simultaneously with varied sampling rates requirement ranging from 100 samples/s to 200 k samples/s, modularity in design enabling scalability. Further, the efficacy of the developed DAAS has been tested by conducting several real time experiments with an existing chemical oxygen iodine laser source with a mass flow rate of 2.3 moles.s-1 both from close ranges and at line of sight remote distances of up to 80 m and nearly 35 m with obstacles.