摘要:

The constrained or constant radius magnetic acceleration of a strong non‐neutral proton ring by a modified betatron field is considered. The modified betatron field consists of an azimuthal magnetic fieldB&Vthgr;superimposed on a betatron fieldBzin which the 1 : 2 flux rule is satisfied. An important advantage of the constrained acceleration is that the energy of the nonrelativistic ions increases with the square of the magnetic field. It has been found that the orbits of the gyrating particles are stable when the self‐field indexns{=&ohgr;2p[2&ggr;0&Vthgr;(t) &OHgr;20(t)]−1} is much greater than unity, provided thatns< (B&Vthgr;/2Bz)2at the orbit. ForB&Vthgr;=0, the orbits are stable only ifns<1/2.

ISSN:0021-8979    

DOI:10.1063/1.324322

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Assignments are given for the 13 H12C14N and 4 H12C15N laser transitions that have not yet been identified. Although 10 different vibrational systems give rise to 27 laser transitions for H12C14N and H12C15N combined, all follow the same basic pattern involving a particular Coriolis interaction and a population inversion between stretching and bending vibrational manifolds. The laser transitions involve rotational states up toJ=48, which is higher than has been observed in room‐temperature spectra.

ISSN:0021-8979    

DOI:10.1063/1.324372

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

By use of low‐inductance (0.5 &mgr;H) discharge circuits, pulses of 9.6 mJ were obtained from a double‐pulsed CuCl laser. An oscillator‐amplifier configuration produced a pulse energy of 11 mJ. Scaling studies indicate that additional increases in the laser energy could be obtained by increasing the discharge voltage above 20 kV and/or by increasing the laser‐tube dimensions.

ISSN:0021-8979    

DOI:10.1063/1.324333

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An analysis is given for the compression of linearly chirped optical pulses propagating in dispersive absorbing media. Numerical calculations are reported for frequency‐chirped CO2laser pulses which propagate as phonon polaritons in &agr;‐quartz or as surface phonon polaritons on BeO, including the influence of thin dielectric films on the surface propagation mode. Quantitative evaluation is made of the use of these modes to form dispersive optical pulse delay lines. It is shown that absorption limits both the usable propagation length and the curvature of the dispersion curves. For the materials considered, this approach is restricted to 10‐psec pulses having THz chirp bandwidths, with large accompanying absorption losses.

ISSN:0021-8979    

DOI:10.1063/1.324316

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The optical perturbation of an infrared wave guided in a GaAs epitaxial layer allows us to measure the two‐photon absorption coefficient &bgr; for the wavelength &lgr;=1.06 &mgr;m. The use of optical properties of free carriers induced by the two‐photon effect and of guided optical wave techniques strongly enhances method accuracy. The result (&bgr;=0.06 cm MW−1) is in good agreement with the most recent bulk measurements and the theoretical values.

ISSN:0021-8979    

DOI:10.1063/1.324374

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The temperature dependence of the threshold current, differential quantum efficiency, and internal loss have been measured in the temperature range 10–293 °K. The threshold current increases relatively slowly with temperature above 100 °K and is independent of the impurity concentration. Theoretical calculation shows that this behavior is to be expected for a band‐to‐band transition that follows k selection. The threshold behavior at low temperatures (? 80 °K) depends strongly on the type and concentration of the impurity. The relatively fast decrease in threshold below 100 °K shows saturation for an active layer withn‐type impurities or with high‐concentrationp‐type impurities. The saturation is attributed to the carrier diffusion length becoming smaller than the active‐layer thickness. The internal differential quantum efficiency is near unity and is independent of temperature. The internal loss, however, decreases with temperature due to reduction in free‐carrier absorption.

ISSN:0021-8979    

DOI:10.1063/1.324384

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A helical TEA‐CO2laser was mode locked by inserting a positive germanium plate close to the plane mirror of a hemiconfocal type of resonator. Single pulses of the emitted sequence of nanosecond spikes were recorded with high time resolution. Best fitting the experimental curves to a Gaussian and (cosh)−2time dependence revealed that the temporal pulse shape corresponds with great accuracy to the (cosh)−2behavior as it is predicted in a theoretical treatment of Haus. Since this theory is dealing primarily with steady‐state saturable absorber mode locking, it is also pointed out that it can be applied to the above case.

ISSN:0021-8979    

DOI:10.1063/1.324396

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Barium has been used as the working medium in a discharge‐heated metal‐vapor laser. The laser produced an average power of 12 W, principally at 1.5 &mgr;, with an overall efficiency of 0.54&percent; when operating at a pulsed repetition frequency (PRF) of 8 kHz. A parametric study of laser performance and a rollover in laser power at high barium number density are discussed.

ISSN:0021-8979    

DOI:10.1063/1.324400

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper presents an analysis of the bunching of an electron beam at optical wavelengths by means of the inverse Cerenkov effect. A laser light beam is used to modulate the velocity of the electrons, and this velocity modulation becomes charge‐density modulation after an appropriate drift distance. The effects of energy and angular spread of the electrons are included, as well as the impact of scatterings in the index‐matching medium. Bunching can occur with reasonable parameter values and the drift distance is on the order of several centimeters.

ISSN:0021-8979    

DOI:10.1063/1.324351

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Eight laser dyes emitting in the spectral region from 550 to 915 nm were investigated to determine their power scalability under excitation byQ‐switched frequency‐doubled Nd : YAG lasers possessing up to 480 mJ pulse energy at 10 Hz pulse repetition frequency (PRF). Conversion efficiencies for some dyes begin to be limited at pump‐power densities as low as 14 MW/cm2due to excited‐state absorption of the pumping radiation. The dependence on resonator length of dye spectral emission, conversion efficiency, and temporal modulation are reported. Divergence of the beam emerging from the dye laser was found to be adversely affected by measures taken to avoid output power saturation at high pump‐power densities.

ISSN:0021-8979    

DOI:10.1063/1.324343

出版商:AIP    

年代:1978

数据来源: AIP