Superthermal ion and X-ray emission from a CO2 tea laser-produced polyethylene plasma

Experiments with a CO₂ TEA laser were performed in which two beams were focused from opposite directions onto the surfaces of a polyethylene foil. Ion probe and X-ray diagnostics evidenced experimental verification of the shock hydrodynamic phenomenon and core-corona decoupling.     

Fast particle emission from CO2 laser produced plasmas

Spatial distributions and spectra of non thermal particles emitted from CO₂ laser aluminum plasmas have been recorded. With laser fluxes greater than 10¹³ W/cm² ions with MeV maximum kinetic energy have been detected as well as fast electrons in the range of 50 to 500 keV. The results are discussed in terms of resonant absorption as a function of different parameters s such as laser flux and angle of incidence.     

Time resolved X-ray photography of the expansion of nanosecond CO2 laser produced plasmas

Time resolved X-ray photography of intense nanosecond CO₂ laser interaction with a number of different targets illustrates the complex expansion of the critical density region from the target, and the strong influence that superthermal electrons have on the plasma dynamics and the radial expansion of the superthermal coronal about the target.     

Stimulated brillouin scattering from CO2 laser produced plasma

Preliminary observations of stimulated backscatter from CO₂ laser produced plasma are reported. The scattered radiation has been spectrally resolved and the measured shift found to be consistent with that expected from ion acoustic waves. The change in wavelength shift when helium is substituted for hydrogen is in agreement with √m_i, where m_i = ion mass.     

Single mode multiline emission from a hybrid CO2 laser

A simple technique of obtaining single mode multiline emission from a hybrid CO₂ laser is described. This involves operation of its low pressure section below lasing threshold and a judicious positioning of the axial modes with respect to the corresponding rotational line centres. Emission with comparable intensities on up to four rotational lines in the P-branch of the 10 μm band has been achieved.     

Reflectivity measurements from a nanosecond CO2 laser produced plasma

The back-scattered light from a laser produced plasma has been studied using a nanosecond gigawatt CO₂ laser. The spectral shift and width of the reflected light have been determined as a function of the incident laser energy.     

X-ray emission from plasma generated by nanosecond laser irradiating tantalum

A continuum spectrum of X-rays, originating from the interaction of a moderate intensity nanosecond Nd:Yag laser (1064 nm, 9 ns, 30 Hz, 900 mJ, 10¹¹ W/cm²) with metal targets producing plasma, is investigated. The photon emission intensity is particularly high when the plasma expands in a low-pressure gas. The photon energy is measured through selective thin absorber films employed in front of the solid state detector. The temperature of the hot electrons generated from the plasma, responsible for the continuum spectrum emission, is calculated from the fit of the X-ray spectrum with a Maxwellian distribution, and it is about 1–2 keV.     

脉冲CO2激光烧蚀锡靶等离子体的数值研究

使用一维辐射流体力学程序MULTI模拟了脉冲CO2激光烧蚀平面锡靶的过程,研究了脉冲宽度、峰值功率密度、靶材初始密度对锡等离子体电子密度、电子温度的时空分布的影响,并结合统计分析得到最有利于产生13.5 nm 极紫外光的激光脉冲宽度。模拟结果表明,脉冲宽度为100~200 ns的长脉冲激光产生的等离子体有利于实现极紫外输出的最佳条件,通过分析等离子体的电子密度、电子温度的分布对这一结论进行了解释。临界电子密度区域有效吸收了脉冲能量,而低密度的羽辉对激光与极紫外辐射的吸收很少。采用长脉冲激光,使得辐射极紫外等离子体持续时间更长,是提高极紫外辐射效率的有效手段。同时模拟还发现,靶材初始密度对等离子体参数的影响不大。     

Reflectivity measurements of a CO2 laser produced plasma

Reflectivity measurements on a CO₂ laser produced plasma are presented and results are compared with the conflicting results of other recent papers. The results presented here show strong anomalous absorption above an irradiance level of ～4 × 10¹⁰W cm^-2 which is a factor of two lower than is predicted from the theory of the parametric instability.     

Interaction of tea CO2 laser light with plasma

High power double discharge type TEA CO₂ laser was used to study laser plasma interaction on carbon target plasma. The maximum output power was 0.3 GW and full width at half maximum intensity was 100 ns. We measured the reflectivity of the laser light at 10.6 μm in wavelength from the carbon plasma. The reflectivity showed a maximum (≈56%) at the laser power intensity of about 1.1 x 10¹⁰ W/cm², and at above this value, the reflectivity decreased. The absorption was introduced effectively above this intensity. The electron density and temperature were also measured.     

Current CO2 laser surgery

With the development of suitable instrumentation, human-engineered to fulfil the requirements of the clinical surgeon and designed to fit in with the physical conditions prevailing in the operating theatre, laser surgery has advanced rapidly in the past few years. It shows signs of even more rapid progress and general acceptance as its application and advantages in more and more fields of surgery are demonstrated.     

Absolute frequencies of CO2 laser transitions by multiplication of CO2 laser difference frequencies

Frequencies of CO₂ laser transitions have been compared to the Cs standard by a four-step frequency chain using difference-frequencies from five CO₂ isotope lasers. A tungsten-nickel diode generates the differences and their harmonics. Measurement of the 10.71 μm R(6) transition of ¹³C¹⁸O₂ is described. The absolute frequency was found to be 27 979 469.512(65) MHz. Simultaneously, the four other CO₂ frequencies in the chain were also determined.     

Advanced CO2 laser rangefinders

Factors affecting the design of compact heterodyne- and direct-detection systems are contrasted. Recent UK achievements are placed in context: a TEA laser direct-detection rangefinder and a chirp-pulse-comparison rangefinder-velocimeter are described.     

CO2 laser induced compton effect in underdense hydrogen plasma

Recent experimental observation of induced scattering of CO₂ laser radiation by an underdense hydrogen plasma can be explained theoretically by non-linear and Compton scattering from ions in the highly cooperative plasma conditions prevailing (kλ_D? 1).     

Spatial characterization of the laser-induced plasma plumes generated by IR CO2 pulsed laser on carbon targets

We have used ferrocene and paraffin wax as novel precursor and solvent for the growth of iron oxide nanoparticles. The proposed method of growth has several advantages over existing methods of growth using iron pentacarbonyl a precursor. Highly crystalline and monodispersed particles are obtained which assemble in two- and three-dimensional hexagonal closed packed superlattices. Growth kinetics has been studied by varying concentration of the precursor and time of growth. A phenomenological model has been proposed to explain the growth kinetics.     

CO2 laser cutting of slate

Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, being noisy, powdery and unsafe for the worker. Thus, there is a need to introduce new processing methods in order to improve both the working conditions and the quality of the products made of slate.Following the previous work focused on the drilling and cutting of slate tiles using a Nd : YAG laser, we present in this paper the results of the work carried out to explore the possibilities to cut slate plates by using a CO₂ laser. A 1.5 kW CO₂ laser was used to perform different experiments in which, the influence of some processing parameters (average power, assist gas pressure) on the geometry and quality of the cut was studied. The results obtained show that the CO₂ laser is a feasible tool for a successful cutting of slate.     

Pulsed CO2 laser scattering from a hydrogen arc plasma and heterodyne detection

We report the first plasma scattering experiment using a pulsed single frequency hybrid-CO₂ laser, employing heterodyne detection to resolve the spectrum. Waves propagating parallel to the electron current in a magnetically stabilised hydrogen arc plasma are detected.     

Temporal shaping of CO2 laser pulses by controlled plasma switching

Coumarin derivatives, 6, 30, and 102, were excited in a simple dye laser by the output at 427.8 nm from a nitrogen ion laser pumped by charge transfer from He⁺₂. Tuning ranges and stabilities of the dyes are reported.     

Model of a microwave beam coupling to CO2 laser plasma

We have designed a transmission line model of the microwave coupling mechanism for a microwave pumped CO₂ laser. The model is a total loss ridge waveguide transmission line having nonuniform impedance. The laser plasma is modeled as a frequency-dependent lossy dielectric and acts as a distributed resistance in the length of the microwave cavity. The coupling structure of the microwaves is designed not to be resonant at the microwave source frequency of 2.45 GHz at 1 kW and propagating the total microwave field energy to be absorbed without internal reflection. An exact solution to this general transmission line propagation constant for a shunt resistance along length of the guide is found. The measurements and predictions of the parameters of the plasma conductivity as a function of the attenuation constant agree closely.