摘要:

An optical parametric source using angle‐tuned type II potassium dihydrogen phosphate (KDP) as the nonlinear medium and pumped with 35‐ps, 355‐nm pulses from an active–passive mode‐locked Nd:YAG laser, is described. With a 1.35‐mJ pump pulse, conversion efficiencies ranging from 1%–40% in the spectral range 450–650 and 800–1600 nm have been achieved. The &Dgr;&ngr;&Dgr;tproducts can approach the transform limit, although 15–30 times transform limited is more typical. The merits of the combination of pump wavelength and phase match used here are discussed with respect to the tuning range, spectral width, and ease of operation. Automated scanning was achieved by placing the crystals on stepper‐motor controlled rotation stages. A convenient, easily reproducible high peak power source rapidly tunable over much of the visible and near infrared is obtained.

ISSN:0034-6748    

DOI:10.1063/1.1139462

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Ellipsoidal mirrors are used to collect the emitted light from fluorophores in fluorescence detected circular dichroic (FDCD) measurements and to deliver this light to a photomultiplier tube (PMT) at 90° to the excitation beam. These mirrors collect light over a symmetrical 71% of the emission sphere centered on the sample cell, and thereby eliminate most of the nonuniformity in detected emission resulting from the anisotropy of photoselection. Furthermore, even with reflectance and path length losses, the amount of fluorescent emission reaching the PMT is increased by a factor of approximately 18. Elimination of photoselection artifacts in UV FDCD spectra is demonstrated by comparing spectra of L‐tryptophan in glycerol with its spectra in water. Validity of the values measured is verified through calibration with a d10 camphorsulfonic acid (d10 CSA) standard.

ISSN:0034-6748    

DOI:10.1063/1.1139463

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Laser measurements at 23.13 cm−1of collision‐induced absorption are described using absorption cells over 1500 cm in length and a liquid‐helium‐cooled bolometer. Also reported are a number of improvements over a previously described system operating at different laser frequencies. The improvements are related to the method of data collection and operation of the system which result in an increased accuracy of determination of the absorption coefficients of nonpolar condensed gases. Typical results are given for the cells used in the temperature range from 126 to 410 K at pressures up to 1500 psi.

ISSN:0034-6748    

DOI:10.1063/1.1139464

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The design of an improved infrared reflection–absorption cell which facilitates the study of redox‐active chemical species is described. The modifications to existing cell designs permit (i) the sample to be cooled to temperatures limited by the characteristics of the solvent, (ii) the sample to be maintained under an inert atmosphere, (iii) the study of small (1–2‐cm3) volumes of solution, and (iv) the entire optical path to be maintained under vacuum. These features of the cell design facilitate the study of small quantities of compounds which are unstable with respect to reaction with oxygen, moisture, and redox partners. The study of tris‐maleonitriledithiolato complexes of chromium in formal oxidation statesiv,v, andvidemonstrates the advantages of the cell.

ISSN:0034-6748    

DOI:10.1063/1.1139465

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A nonintrusive diagnostic system is described which permits simultaneous measurement of temperature, nitrogen number density, and oxygen number density in hostile combustion environments. This system is pumped by a 10‐Hz neodymium YAG laser, and signals are detected with an intensified photodiode array and dual photomultipliers. The system utilizes a folded BOXCARS beam arrangement, two probe dye lasers, dynamic range expansion, polarization rejection of nonresonant background, and multiplexing of the signal beams.

ISSN:0034-6748    

DOI:10.1063/1.1139466

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An original technique, with a special design of liquid cell, is proposed for third‐harmonic generation in liquids. The technique is based on a principle of harmonic generation in an infinite medium by focused laser beam applied for liquid cell windows and uses a thin wedge‐shaped liquid compartment. The measurements can be performed in air, and a high precision in cubic susceptibility and refractive index dispersion determination can be obtained. The technique also allows measurements to be made on liquids absorbing at harmonic and fundamental frequencies and in function of external parameters like temperature, pressure, and electric or magnetic fields. Some results for organic solvents are presented and compared with those obtained by other methods.

ISSN:0034-6748    

DOI:10.1063/1.1139467

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Density fluctuations in magnetically confined plasmas have been measured from the phase scintillations impressed onto a 10.6‐&mgr;m wavelength laser beam probe, using a Mach–Zender interferometer operating in the optical near field. By careful design, the effects of vibration and air‐borne sound waves, which limit the instrument’s sensitivity, have been reduced to a level such that the minimum detectable signal is 10−6rad in the frequency range 10 kHz–1 MHz, corresponding to a plasma density fluctuation level (&dgr;N/N) of 10−4.

ISSN:0034-6748    

DOI:10.1063/1.1139468

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Compact electrostatic charge exchange analyzers (18×18×13 cm) have been constructed for installation in areas of high magnetic fields and restricted access near tokamak fusion devices. The analyzers employed carbon stripping foils, and have been calibrated for proton and deuteron energies between 1 and 70 keV. They have been successfully used to study charge exchange losses in auxiliary‐heated tokamak plasmas and were found to be ideally suited to supplement the larger and more complex gas‐cell analyzers by providing additional spatial and temporal information at a modest effort and cost.

ISSN:0034-6748    

DOI:10.1063/1.1139469

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new diagnostic tool has been developed that can discriminate between ions in a multispecies plasma of intermediate densities (107<ni<1012cm−3) and temperatures (0<kTi<100 eV) and measure their local densities (to within 5%) and temperatures (to within 1 eV) using time‐of‐flight techniques. The probe consists of an exciter in line with a movable retarding‐grid ion energy analyzer (detector), and has a spatial and temporal resolution of ∼0.4×4 cm and ∼200 ns, respectively. The exciter structure is composed of three mesh grids, an accelerator, and two shields (diameter 4 cm, separation 2 mm). A+80 V fast rising pulse (30‐ns rise time, 2‐&mgr;s width) is applied to the center grid which excites ion bursts that are detected by the ion energy analyzer. The charge‐to‐mass ratio of Ar+, Ar++, Ne+, He+, H+is determined to within 10%, and the relative densities and temperatures of Ar+, Ne+, and H+are measured.

ISSN:0034-6748    

DOI:10.1063/1.1139470

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Described here is the scaling of a repetitively pulsed, flash x‐ray source to yield 140‐mW average power in 15‐ns pulses of radiation near 1 A˚. Interchangeability of discharge anodes has provided for a significant fraction of the output to be extracted in theKlines of Cu, Mo, Nb, and Ag. In less than 1 min of experimental time, a peak spectral density is radiated that exceeds 1×1018keV/keV. For some applications this device can offer a tabletop alternative to laser plasma x rays and to synchrotron radiation.

ISSN:0034-6748    

DOI:10.1063/1.1139471

出版商:AIP    

年代:1987

数据来源: AIP