Two-Stage Radio Frequency Power Generator-Amplifier Design for a TEM00 CO2 Slab Waveguide Laser
This letter presents the results of the research conducted on the design, construction and test of a two stage ra- dio frequency power generator-amplifier directed adapted to an in-house-built compact CO2 waveguide laser. The main characteristic of this power supply lies in the fact its design is based on MOSFET technology for both the oscillator and the amplifier stages. RF output power is centered at 81MHz frequency signal between 100W to 150W. The two-stage sys- tem device has a minimum electric conversion efficiency of 64%. Consequently, the laser head and RF excitation design must have an electrical termination of 50� impedance and the whole system may include a proper matching circuit. The overall test, for the entire system: RF excitation along with our CO2 laser head, is made with a typical gas mixture of CO2- N2-He with proportion of 1:1:3 correspondingly and at a final pressure of 40Torr. Under these specific conditions, a maximum optical output power of 10.7W was obtained for an input feed RF power of 147W. Regarding the optical qual- ity we measured the transverse mode of propagation TEM00 which indicate the entire system work very near the diffrac- tion limit specifications for similar laser systems.
Recent trends in oscillator design
Two decades ago, oscillators were typically designed by starting with a topology named for its discoverer, such as Colpitts or Pierce, and then analytically or empirically modifying element values to achieve a desired result. Later, the application of linear CAE tools provided more options and opportunity. The use of nonlinear analysis, along with other recent advancements, has contributed to the maturity of the knowledge. However, misunderstanding still abounds. This article briefly reviews classic linear analysis techniques, extends this analysis to closed-loop concepts, reviews a recent contribution by Randall and Hock, and adds nonlinear analysis to develop a thorough but intuitive feel for the oscillation phenomena. Finally, the nature of oscillator startup is illustrated using a new oscillator topology.
VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission
A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of greater than 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights less than 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(sub A) approx. = 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of Omega = 13.45 deg - ((3 deg (sin(exp 2)B)). 5. We find a statistical limb darkening, which can be described by the relation (T(sub B)(alpha))/T(sub B)(0)) = 0.4 + ((0.6(cos(exp 2) alpha)) for sources with T(sub B) greater than 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater than or approximately equal to 0.5 MK), or equivalently, long-lived sources (greater than or approximately equal to 5 days) show a systematic variation of their altitude as function of the center-limb distance.