摘要:

A stabilized laser interferometer is proposed with two beams as the light source. The fringe shift for a 0.63 &mgr;m beam of a He–Ne laser is used to stabilize the interferometer against the effect of mechanical vibrations via a feedback controlled speaker coil, while another beam of 3.39 &mgr;m, for which consequently the effect of the mechanical vibrations is excluded, is used to measure the plasma density. A stability of ∼1/500 of one fringe for 0.63 &mgr;m is obtained during a long period for frequencies lower than a few Hz. The stability for higher frequencies is limited to ∼1/30 of one fringe for 0.63 &mgr;m, which correspondes to ∼1/200 of one fringe for 3.39 &mgr;m, by the acoustic noise picked up by the speaker coil. Furthermore, the total accuracy is limited by the detector noise to ∼1/60 of one fringe for 3.39 &mgr;m, which corresponds to a line electron density of ∼5×1014cm−2. The detector noise may be reduced by cooling the detector. The advantage of this technique over the single‐laser technique is that the frequency response of the interferometer extends down to zero frequency. The interferometer is tested with the measurement of a plasma in a dynamic magnetic arcjet. Since the effect of the neutral gas background is reduced in the present interferometer, the application has an advantage for the diagnostics of plasmas produced in high pressure gases.

ISSN:0034-6748    

DOI:10.1063/1.1136142

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An actively mode‐locked,Q‐controlled ruby laser has been developed which produces high‐intensity (1.5 GW/cm2) 35 ps pulses synchronized to better than 100 ps with an event produced by another mode‐locked laser.

ISSN:0034-6748    

DOI:10.1063/1.1136143

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A simple, inexpensive yet reliable power monitoring device for power levels of 1–10 W in the infrared is described. The monitor uses a thin foil of refractory material to convert the infrared radiation to visible radiation, where the power may be determined by a conventional visible light photometric device.

ISSN:0034-6748    

DOI:10.1063/1.1136144

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A doppler velocimeter utilizing a spectrograph and a short‐pulse laser probe is described which provides good spatial (20 &mgr;m) and subnanosecond temporal resolution. This system has been used to measure the velocity profiles of targets ablatively accelerated to very high velocities by a high‐power laser beam. In comparison to systems employing interferometric techniques, this velocimeter significantly relaxes requirements on the target surface being examined and the time resolution needed to measure velocities of rapidly accelerating surfaces.

ISSN:0034-6748    

DOI:10.1063/1.1136145

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We have designed and constructed a feedback system that will maintain the angle between two x‐ray diffracting crystals. The system was designed for use in conjunction with a double crystal synchrotron radiation monochromator at CHESS and will preserve the relative angle between crystals during energy scans and as a function of time for a fixed wavelength. A voltage proportional to the slope of the rocking curve is used as the feedback signal. This signal is normalized in such a way that the time dependence of the incident beam intensity is removed. The feedback system allows one to sit not only at the peak of the rocking curve, but also on the flanks, an aspect crucial when utilizing the harmonic rejection properties of the double crystal monochromator.

ISSN:0034-6748    

DOI:10.1063/1.1136146

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A linear position sensitive small‐angle x‐ray detector has been developed which utilizes a directly exposed self‐scanning photodiode array cooled to liquid nitrogen temperature to reduce fixed pattern noise. Direct exposure of the array improves the overall sensitivity to 8 keV photons by an order of magnitude over photoconversion techniques. With this improvement in sensitivity, the photodiode array has been effectively used to detect x rays from weakly scattering biological molecules in solution. The slit‐like geometry of the photodector elements ideally matches that of a Kratky collimator employed with a low‐flux x‐ray source to enhance greatly the data collection rate. The detective quantum efficiency and stability of the detector have been determined while taking small‐angle scattering measurements of proteins and the results are quantitatively applied to characterize the performance of the instrument.

ISSN:0034-6748    

DOI:10.1063/1.1136147

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We have developed a versatile tool for generating planar shock waves. This system, which we call the electric gun, is capable of projecting thin flyer plates with velocities in the range 1–20 km/s. It is presently being used in high‐explosives‐initiation experiments and is being developed for equation‐of‐state measurements in the 1–5 TPa range. We describe the electric gun facilities that are operational at Lawerence Livermore Laboratory and discuss applications of electric gun technology to problems of interest to shock‐wave researchers.

ISSN:0034-6748    

DOI:10.1063/1.1136155

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A novel Na vapor cell has been constructed for use at temperatures up to 500 °C. High‐vacuum sapphire‐to‐metal seals have been made without brazing by use of copper gaskets placed between the sapphire windows and kovar compression rings. Careful design of cell dimensions allows for matched thermal expansion rates and thus the vacuum seal maintains its integrity over a very large temperature range (0°–750 °C).

ISSN:0034-6748    

DOI:10.1063/1.1136156

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A high‐performance research‐oriented secondary ion mass spectrometer (SIMS), based on a double‐focusing mass spectrometer, has been designed, constructed, and evaluated. This instrument is relatively free of some of the instrumental limitations associated with conventional molecular SIMS instrumentation such as energy and mass discrimination. Theoretical design considerations and its construction are discussed. Its performance has been evaluated in various operational modes using a variety of samples and some important instrumental parameters are reported. Finally, the novel and outstanding high‐mass capability of this SIMS instrument is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1136157

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

This paper describes a chemical lathe for the efficient preparation of high‐quality surfaces on samples for low‐cycle fatigue testing. The chemically machined gage lengths of samples prepared by this unit are of metallographic quality and free of machining marks and residual stresses. This paper discusses the theory of operation, design, construction, and setup of the chemical lathe. The basic concept of this unit may be readily applied to a variety of specimen geometries employed in other mechanical tests.

ISSN:0034-6748    

DOI:10.1063/1.1136138

出版商:AIP    

年代:1980

数据来源: AIP