摘要:

A simple method for the simultaneous measurement of attenuation and phase‐velocity changes of surface acoustic waves, based on the use of a surface‐acoustic‐wave oscillator, is described. The application of the method is illustrated in the case of surface acoustic waves interacting with charge carriers in thin gold fims vapor deposited on the lithium niobate substrate supporting the surface waves. Good agreement is obtained between experimental results and theory. It is shown that the product of carrier mobility and Fermi energy can be determined with good accuracy independently from three different relations involving attenuation, phase velocity, and resistivity data.

ISSN:0003-6951    

DOI:10.1063/1.90259

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The attenuation coefficients &kgr; and wave speedsvshave been measured for SAW (surface acoustic waves) ∼5 MHz propagating on several polished flat polycrystalline metal surfaces. Laser interferometry techniques were used to measure standing‐wave coefficients in such a way as to relate conveniently to a determination of both &kgr; andvs.

ISSN:0003-6951    

DOI:10.1063/1.90260

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We consider a simple model in which a small fraction of runaway electrons produce the often‐observed x‐ray emission in pinches. We show the turbulent collision frequency scales asv−3, from fairly general arguments. Simple scalings result, linking the number of runaways with their energy. Fitting to a recent experiment gives a pinch field exceeding the applied field by ∼400. Future experiments can check the scaling without knowing the pinch electric field.

ISSN:0003-6951    

DOI:10.1063/1.90261

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A low‐&bgr; plasma column a few mm in diameter by 22 cm in length is heated by an axially directed CO2laser to a high‐&bgr; state in a fast rising solenoidal field. Successful heating depends on proper timing between the laser pulse and rising field. Typical conditions attained are a line energy density of 6 J/cm, T¯≈40 eV, andne≈3×1017e−/cm3, with conditions quite uniform along the length. The heating suppresses instabilities which appear under certain conditions in the non‐laser‐heated case.

ISSN:0003-6951    

DOI:10.1063/1.90262

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An anemometric method to measure the velocity of fluid flow in the vicinity of a cation‐selective membrane is described. It is shown that the turbulent phenomenon which develops on the depletion side of the membrane, beyond the critical current density point, is confined to a space region of ≃130 &mgr;m from the membrane surface; this turbulence is strongly coupled to the dissipation process of electric energy in the depletion region.

ISSN:0003-6951    

DOI:10.1063/1.90263

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Fluctuations of semiconductor laser outputs such as transient relaxation oscillations, external‐mirror‐induced fluctuations, or degradation‐induced self‐sustained pulsations are suppressed by placing a mirror close to a laser facet. The mirror‐to‐laser distances are 0.3–2.0 cm for effectively suppressing the fluctuations.

ISSN:0003-6951    

DOI:10.1063/1.90264

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We have observed growth‐ and processing‐related defects and optically induced degradation in In1−xGaxAsyP1−ydouble‐heterostructure material intended for 1.2–1.3‐&mgr;m laser diodes. Threshold for the degradation observed decreases with increasing layer thickness, suggesting a relation to strain arising from compositional variation during growth.

ISSN:0003-6951    

DOI:10.1063/1.90265

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

ac electroluminescence from thin films of Mn‐doped ZnSe, sandwiched between two insulating films, shows a hysteresis in light output versus applied voltage, similar to that observed in ZnS : Mn. We also find that the threshold voltage for light emission is approximately a factor of 2 smaller for ZnSe structures than for similarly prepared ZnS structures of identical dimensions.

ISSN:0003-6951    

DOI:10.1063/1.90266

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A simple process is presented for fabricating channel waveguides by a thallium‐ion diffusion technique. The thallium diffusion coefficient is estimated to be 2×10−12cm2/sec at 400 °C. Effective mode index measurements show a complementary error function index profile in the waveguide. Waveguide losses are measured to be −0.60 dB/cm. A passive component of optical communications systems, a star coupler, is fabricated using the thallium‐ion exchange process.

ISSN:0003-6951    

DOI:10.1063/1.90267

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The absolute photon yield expressed as the number of photons emitted at a particular wavelength per sputtered atom has been measured for 34 elements in NBS standard glass targets bombarded by 20‐keV Ar+ions. The yield values lie in the range 10−2–10−6. The detection limits for these elements in parts per million by weight have also been estimated for given bombardment conditions.

ISSN:0003-6951    

DOI:10.1063/1.90268

出版商:AIP    

年代:1978

数据来源: AIP