摘要:

A technique is proposed for obtaining high‐resolution space‐time‐density images in an inhomogeneous gas sample. The method utilizes overlapping pulses of laser and/or microwave radiation such that avalanche breakdown occurs only where the density is a preselected value and when the pulses overlap. The breakdown produces local plasma regions of high luminosity that can be detected easily, even in the presence of high chemiluminescent or incandescent background.

ISSN:0021-8979    

DOI:10.1063/1.327897

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A scheme is proposed and discussed for obtaining soft and ultrasoft x ray spectrums by photoelectron analysis. It is shown that by combining a grating or crystal spectrometer with a photoelectron spectrometer, the x ray spectrum can be obtained unambiguously over a wide range of wavelengths.

ISSN:0021-8979    

DOI:10.1063/1.327898

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Experiments are described pertaining to the development of very high‐current pulsed linear ion accelerators utilizing electron neutralization. A novel magnetically insulated gap using radial magnetic fields has been tested. It provides stable electron cloud confinement over microsecond time scales with no detectable leakage current. The gap can act as an ion injector when used in conjunction with a plasma source. Control of the electron cloud dynamics allows the injector to operate in an enhanced current density mode (10–50 times the Child‐Langmuir limit) with high efficiency and with plasma source control of the current flow. Currents up to 20 kA at 100 kV applied voltage resulted when using a light‐ion flashboard plasma source. Carbon beams were produced by extraction from a flowing plasma from a gun array. A 3‐kA beam with equal fractions of C+and C++was extracted over a microsecond time scale with little proton contamination. The use of active plasma injection into the high‐intensity magnetically insulated diode had the advantages of ion species control, reduction of gap damage, operation at constant impedance, elimination of plasma closure effects, and a demonstrated ability to control the extracted beam optics. Observations were also made of beam propagation and compared to fast neutralization models. Agreement was good, and an upper limit of 0.2% was calculated for the imbalance of ion and electron space charge. When using the carbon injector, two‐thirds of the beam reached a second magnetically insulated gap where it was postaccelerated. The second gap had an applied voltage in the range 150 –200 kV with beam currents typically 2 kA. Observations were made of electrostatic focusing in the postacceleration gap. These were in good agreement with theory based on the concept of virtual electrodes determined by the neutralizing electron dynamics.

ISSN:0021-8979    

DOI:10.1063/1.327899

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electron energy distribution in a magnetic multipole ion source has been measured utilizing a retarding potential energy analyzer. The observed distribution of the primary electrons is spread out from the thermal population to energies 30% above the discharge energy. Implications on the theory of ionization efficiency are discussed.

ISSN:0021-8979    

DOI:10.1063/1.327900

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We studied the pressure‐dependent peak intensity and time history of the 388.9‐nm radiation emitted from the 33P→23Stransition of helium at pressures ranging from 10−2to 55 Torr, following excitation with a short (15 nsec) and intense (25 kA) burst of high‐energy (500 keV) electrons. From the decay of radiation we determined the short‐lived and long‐lived decay components and the values of the effective direct‐excitation cross section of the 33Plevel at several gas pressures. At low pressures ( p?4 Torr) we also determined the quenching cross section of the 33Plevel by ground‐state helium collisions.

ISSN:0021-8979    

DOI:10.1063/1.327901

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An analysis is given for the energy exchange between a focused laser beam and free relativistic electrons in a circular orbit in a uniform magnetic field. Curves are presented to illustrate the dependence of this coupling on the various system parameters. Applications for inverse synchrotron interaction include electron acceleration and amplification of electromagnetic radiation.

ISSN:0021-8979    

DOI:10.1063/1.327902

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

This paper presents a detailed study of the cw propeties of a modified‐strip buried‐heterostructure (MSBH) laser. Included are studies of the electrical, electro‐optical, and optical beam properties, together with spectral characteristics, and temperature dependence of thresholds. A variation of this type of laser, a passive‐mirror modified‐strip buried heterostructure is also described. The MSBH laser possesses many desirable properties including excellent linearity of the lasing emission consistent with a second‐harmonic content more than 40 dB below the fundamental, constant proportionality between the light emitted from the two mirror facets, ’’kink‐free’’ emission to the maximum cw power levels measured (35 mW/mirror facet), nearly round near‐field intensity distribution with an ellipicity of 1.3 : 1, lasing emission in the lowest‐order transverse mode, full angle half‐power perpendicular to the junction plane of 27.3° (significantly smaller than any other practical cw DH laser structure), and narrow cw spectra (emission is typically in only a few longitudinal modes). MSBH lasers are nonastigmatic signal sources so that diffraction‐limited spherical optics can be used. Pulsations are not observed if the active stripe is free of absorbing defects. cw operation of 10 mW/mirror facet was obtained at ambient temperatures to 90 °C with aT0of 126 °K. For 380‐&mgr;m‐long lasers pulsed threshold currents of 78 mA dc, slope efficiencies of 63%, forward resistances of 2 &OHgr;, and zero‐biased capacitances of 15 pF have been measured. At the operating power of 3 mW/mirror facet, the optical power density at the mirror facet is low (?104W/cm2) which may have positive reliability implications. The passive‐mirror form of the MSBH laser (PM‐MSBH laser), with the potential for avoiding surface effects which have been implicated as a cause of pulsations and laser degradation, have been measured with thresholds of 104 mA dc and slope efficiencies of 31%.

ISSN:0021-8979    

DOI:10.1063/1.327903

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A computer model of a semiconductor laser has shown that deep‐level electron traps with realistic physical parameters can cause a device to emit light in very short (20 ps) pulses, with high peak power (0.5 W) and a few nanoseconds repetition rate. The pulses appear suddenly as threshold current is reached causing the average output power to suddenly jump to a few milliwatts. A single optical pulse can be triggered by a longer current pulse containing fewer electrons than the number of photons omitted. These triggerable semiconductor lasers can shorten and amplify a detected light pulse making possible a number of lightwave‐logic applications.

ISSN:0021-8979    

DOI:10.1063/1.327904

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The idea of using a multi‐Z(e.g., carbon, oxygen) thin plasma column as a medium for soft x‐ray lasing action is presented. A plasma confined by a strong magnetic field is first heated by a CO2laser, and then cools rapidly by radiation losses. This leads to a level population inversion of hydrogen‐like carbon or oxygen ions. Two computational models are presented. One uses given electron temperatureTe(t) evolutions. The other usesTe(t) calculated from an energy balance equation with CO2laser beam power as a parameter. According to calculations, a total gain ofG≳100 is expected for 3→2 andG≳10 for 4→2 transitions (&lgr;=182 A˚ and &lgr;=135 A˚, respectively) for C VI ions using a CO2laser beam with power ∼5×1010W for plasma column heating.

ISSN:0021-8979    

DOI:10.1063/1.327905

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Extrapolation of the conventional diode equation into the oscillating region gives formal expressions for the internal and external efficiencies in terms of waveguide parameters, threshold current, and the voltage derivative of laser power. The latter, which depends on band and laser theory, is examined for two models. Linear perturbation theory gives qualitative conclusions which are of little utility for actual devices. Combination of diode analysis with the band theory of Stern and theP* theory of North gives a comprehensive theory of the current dependence of the static properties of the laser. The assumptions of the extrapolation are discussed, and experimental examples are presented to illustrate the utility of the new diode analysis. The comprehensive theory is used to interpret various known properties of devices such as linearity of power with current, change of internal efficiency with waveguide thickness, change of junction resistance at threshold, and several scaling laws. The types of experiments to test the theory are discussed and, in particular, the properties peculiar to theP* interaction. Many studies of the latter have shown its rather general applicability, but its utility for ’’pure mode’’ lasers with narrow spectra has not yet been thoroughly studied.

ISSN:0021-8979    

DOI:10.1063/1.327906

出版商:AIP    

年代:1980

数据来源: AIP