Solid-state Excitation Research Articles

5 kW transversely excited atmospheric CO2 laser driven by a solid state exciter employing insulated gate bipolar transistors

An average laser output power as high as 5 kW has been produced from a transversely excited atmospheric CO2 laser pumped with a new solid state exciter. The exciter providing a 100 J transfer energy consisted of a high voltage pulse generator and a two stage magnetic pulse compressor. A stack of new high power semiconductor switches, called insulated gate bipolar transistors, was employed for the main switch of the pulse generator. A sophisticated discharge head with the corona preionization behind a perforated anode was designed to realize fast and uniform gas flow in cooperation with acoustic dampers. The maximum average laser power of 4.6 kW was attained at a repetition rate of 550 pps with an overall efficiency as high as 10.5%. The maximum repetition rate achieved was 1.1 kpps, at which the resulting average laser power was 3.4 kW.

A comprehensive generator-line-infinite-bus micromachine model

For almost twenty years, a miniature three-phase electric power system has been used by students at the University of Manitoba, in several courses and for many student hands projects. It features a realistic natural frequency of about one hertz, a realistic exciter/field time constant of about five seconds, a solid state exciter, many short time constant tranducers, a unique synchroscope, and a storage oscilloscope. On the storage oscilloscope power-versus-phase curves can be observed-something seldom seen by practising engineers or students in the usual laboratory situation. Advanced students can construct operational amplifier based stabilizers on a bread-board close to the regulator which is also on a small bread-board. >

Use of Insulated Gate Bipolar Transistors in an All Solid State Exciter for Multikilowatt Average-power, TEA CO2 Lasers.

Using insulated gate bipolar transistors (IGBT), we constructed an efficient, all solid state exciter for high efficiency, high power operation of a transversely excited atmospheric (TEA) CO2 laser. The exciter was composed of a high-voltage pulse generator and a two-stage magnetic pulse compressor. Forty-eight series and two parallel IGBTs were used as the main switch of the pulse generator. The maximum switching voltage as high as 36 kV was achieved with a transfer energy of about 100J. The pulse generator, employing an LC inversion circuit, produced a 65 kV, 7.5μs pulse, which was compressed to 0.5μs by the pulse compressor. The use of an IGBT stack decreased energy waste in a snubber circuit, resulting in a high efficiency of more than 90%. By applying the exciter to a TEA CO2 laser with a discharge volume of 0.5l, an average laser power of 4.6 kW was attained at a repetition rate of 550 pps for a switching energy of 78J. The overall efficiency of the laser was as high as 10.5%. A repetition rate of 1.1 kpps was attained, resulting in an average laser power of 3.4 kW by reducing the switching energy to 42J.

High-Power TEA CO2 Lasers.

Progress of high-power TEA CO2 lasers is reviewed with paticular emphasis on pulse power conditioning by solid-state switching techniques. The use of the solid-state switches is a key technology forhigh-power, long-life operation because the life time of a discharge switch becomes a limiting factor of the operation life of such lasers. Another limiting factor is the degradation of the laser gas mixture. In this review, we summarize the present status of high power TEA CO2 lasers and then discuss on technical problems to be overcome for the development of high-repetition-rated TEA CO2 lasers. We also introduce two types TEA CO2 laser employing a solidstate exciter which is newly desinged and constructed for the demonstration of long-life and high-power operation.

A photoswitched small TEA CO2 laser

A small photoswitched TEA CO2 laser has been developed. This small aperture, low repetition rate laser can produce 69 mJ optical pulses from a discharge volume of 12.5cm3, with an energy efficiency of 11.1%. This energy efficiency is the highest so far reported with such lasers. Corona UV sources driven by a simple inexpensive solid state exciter are used to trigger the discharge. Also demonstrated is the wider input energy loading and enhanced discharge stability provided by overvolting the laser head.

A solid-state switched small TEA CO2 laser

A corona pre-ionized, solid-state switched transverse, electric, atmospheric CO2 laser has been developed. This small aperture, low repetition rate laser can produce 114 mJ optical pulses from a discharge volume of 15.6 cm3, with an energy efficiency of 12.7%. The device is driven by a simple inexpensive solid-state exciter, which uses a series stack of thyristors, to provide an output efficiency similar to that produced by a conventional thyratron circuit.

固体化電源を用いた100W級銅蒸気レーザの開発

固体化電源を用いた100W級銅蒸気レーザの開発

Nonlinear far-infrared spectroscopy of solids

High-power lasers in the FIR allow nonlinearity studies of a range of fundamental solid-state excitations. Some of these excitations, e.g. lattice vibrations or ballistic carrier motion, are specifically probed in the FIR but are not accessible by the more advanced visible nonlinear spectroscopy. This paper reviews the development of FIR nonlinear spectroscopy which took place essentially in the past decade, and gives examples on the one hand of harmonic generation which leads to evaluate nonlinear potentials of lattice ions and mobile carriers, and on the other hand describes laser-induced population changes in electronic states which result in both saturated absorption and saturated photoconductance.

Small solid-state switched pulser-sustainer TEA CO2 laser

A corona preionized pulser-sustainer, transverse, electric, atmospheric CO2 laser has been developed. This small-aperture laser can produce 180 mJ optical pulses of 5 mu s duration from a discharge volume of 15.6 cm2 with an efficiency of 12.4%. The laser was driven by a simple inexpensive solid-state exciter.

Power factor enhancement of induction machines by means of solid-state excitation

A novel concept for power factor correction of induction machines is introduced that employs an auxiliary three-phase stator winding together with a pulse-width-modulated (PWM) inverter to supply excitation power to the machine. When the PWM inverter is modeled as an equivalent capacitor, it is shown that two values of capacitance will yield unity power factor at a given operating condition. The effect of machine parameters on the critical value of capacitance is examined. A control algorithm to ensure unity power factor at the terminals of the main stator windings is presented, and its satisfactory operation is verified by means of a detailed analog computer simulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Solid state room-temperature fluorescence of p-oligophenylenes and of poly(paraphenylene) films prepared electrochemically

Fluorescence excitation and emission spectra of p-terphenyl, p-quaterphenyl and p-quinquephenyl were measured in sodium chloride pressed pellets at room temperature (293 K). Significant red-shifts of fluorescence spectra are found, upon increasing the number of phenyl rings in the oligomer chain. Polyparaphenylene (PPP) films were prepared by a new method of electro-oxidation of p-terphenyl in dichloromethane. Their solid-state fluorescence excitation and emission spectra were determined at room temperature. The excitation wavelength-dependent changes of fluorescence emission bands as well as their highly structured components are attributed to the occurence in the excited singlet state of a variety of planar or nearly planar configurations of PPP films with relatively long chains.

Spectrofluorimetric study of electrosynthesized and chemically prepared poly( N-vinylcarbazole) films

A spectrofluorimetric method is proposed for the study of chemically prepared and electrosynthesized poly( N-vinylcarbazole) (PVCA) films on Pt thin layers. Solid-state fluorescence excitation and emission spectra of PVCA are obtained at room temperature. The effects of electrochemical doping and polymer film growth on fluorescence spectral properties are investigated. ClO − 4 electrochemical doping of PVCA films causes fluorescence quenching. In situ measurements of the changes in fluorescence intensity of PVCA films during electrochemical cycles are described. The sensitivity of the spectrofluorimetric method is very high for the quantitative determination of polymer films, with a detectable minimal mass of about 2.5 × 10 −10 mol cm −2 of PVCA, corresponding approximately to the equivalent of a monolayer.

Theory of relaxation rates of coupled-mode solid-state excitations

Relaxation rates are calculated for the modes formed by coupling an exciton to an acoustic phonon. Derivations for the phonon-like and exciton-like parts of the coupled-mode spectrum are followed by a general expression for the relaxation rate that applies for all coupled-mode frequencies and for arbitrary crystal dilution and temperature. The method is valid for similar coupled-mode excitations such as exciton polaritons.

Effects of Feedback Signals on the Transient Response of a Power System Using a Solid State Excitation System

This paper analyses the effects of feedback signals in a solid state excitation system, in addition to the normal voltage regulator signal, on the transient stability of a power system. It was observed that a suitable combination of speed deviation and torque angle deviation signal reduces the transients most effectively.

Elevated Temperature Vapor Photoelectron Spectroscopy

Abstract In the past decade the investigative technique known as photoelectron spectroscopy has undergone a rapid rise in use. Papers dealing with research work involving the method are now being published at a rate of over 400/year. The procedure involves the irradiation of a gaseous, liquid, or solid sample with monoenergetic photons to liberate photoelectrons. Then, an analysis of the electrons according to their kinetic energies is made. The results are usually presented as photoelectron spectra in the form of electron intensities plotted against their kinetic energies. Peaks in the spectral traces are usually reflections of the liberations of electrons from discrete energy levels of the substances involved, and ionization energies corresponding to these peaks may be readily obtained by subtracting their kinetic energies from the energy of the irradiating photons. The ionization energies so obtained can be related to the electronic energetics of the atoms o r molecules of the irradiated material in, terms of atomic or molecular orbital descriptions. Fine structural detail in the spectra are often meaningful in revealing other energy-loss processes such as vibrational and solid-state excitations.

Dispersion of Solid State Excitations

The addition of an electron spectrometer to an electron microscope extends the capabilities not only of the microscope but also of the electron spectrometer. Operation of the electron microscope in the high angular resolution, small angle scattering mode (see, for example, Wade and Silcox) extends the angular scattering range of the electron spectrometer into an interesting small angle region (&lt;10−4 radians) hitherto inaccessible. The dispersion of many solid state excitations in the energy range leV to 20eV is strongly affected by the light line w = ck where the energy loss ΔE = ђw and the momentum transfer is ђk. These effects can be observed directly by the electron microscope/spectrometer combination at scattering angles &lt;10-4 radians.