摘要:

We present the design, construction, and demonstration of a device to produce short, high‐frequency bursts of ultrashort optical pulses. Specifically, we use a folded delay line structure called the optical rattler to produce a 600‐GHz burst of 400‐fs pulses.

ISSN:0034-6748    

DOI:10.1063/1.1143217

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A computerized setup for optical polarization measurements is described. The heart of this setup is a photoelastic modulator (PEM) whose retardation phase can be kept constant when the wavelength of modulated light is scanned in a wide range, and a dual‐channel gated photon counter which has the capability of compensating the variation of excitation intensity with time and wavelength. Unlike conventional analog setups, where the difference of two perpendicularly polarized light components (I+−I−) and the average of these components 1/2(I++I−) are extracted electronically and the ratio 2(I+−I−)/(I++I−) is recorded as degree of polarization, this spectropolarimeter directly records theI+andI−components (for circular polarization) orI∥andI⊥components (for linear polarization) of the analyzed light signal. Once the spectra of the two components are stored as a numerical file in the computer, they can be processed to extract the degree of polarization as a function of wavelength, temperature, etc. The curvature and asymmetry of the modulator response are taken into account exactly in data processing. The spectropolarimeter has proved to be very accurate due to the capability of compensating the fluctuation in excitation source and of electronically tracking the modulation wavelength.

ISSN:0034-6748    

DOI:10.1063/1.1143218

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

6‐in.‐diam multilayer mirrors were fabricated for a double mirror monochromator designed to select photon energies between 830 and 1240 eV (0.5–1.5 nm). Coatings with 50 and 40 Mo/C bilayers with a bilayerdspacing of 4.1 and 4.6 nm, respectively, and a division parameter of &Ggr;=0.44, were deposited by the triode sputtering method on 6‐in.‐diam silicon with 5%duniformity. Similar coatings were also deposited on 2 in. silicon wafers. Peak reflectivity and integrated reflectivities were measured at several wavelengths between 0.5 and 1.5 nm using monochromatized synchrotron radiation. Measurements were performed along a 4 in. diameter for the large area coatings. The resolving power as measured in the center of the six inch mirrors was found to be 41 and 46 at 826 and 1240 eV, respectively, which compares well with the corresponding theoretical values of 43 and 40. The performance of a matched pair of multilayer mirrors with the smaller areas in the double mirror configuration was experimentally investigated as well. Reflectivity values for the two mirror configuration scheme were calculated from the experimental data for the individual mirrors. Possible applications of such monochromator in lithography research are briefly described.

ISSN:0034-6748    

DOI:10.1063/1.1143219

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We present the details of a new type of spectrometer which allows the recording of molecular emission signals in the microwave and millimeter wave region with subsequent Fourier transformation. First experiments up to 49 GHz have been carried out, but we claim that the biphase modulator used to 49 GHz will allow broadbanded spectroscopy up to the 100‐GHz region.

ISSN:0034-6748    

DOI:10.1063/1.1143220

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The transfer matrix up to the second‐order aberrations has been formulated for an electron optical systems of a monochromator and an energy analyzer. Both of these instruments have two magnetic round lenses and a retarding Wien filter. The filter consists of a deceleration lens, a Wien filter, and an acceleration lens. The optimum excitation of the round lens is found to be that which provides parallel exit of electrons from the acceleration lens. The excitation of the Wien filter must be adjusted to focus the beam on the slit. The computed results are useful for finding the optimum operating conditions and for explaining experimental results of the high‐resolution electron energy loss spectrometer.  

ISSN:0034-6748    

DOI:10.1063/1.1143221

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Experiments of microwave spectroscopy of gases at low pressures are performed with some advantages using dielectric waveguide cells. The construction of an improved version of a dielectric waveguide spectrometer is described. Details on the experimental methods utilized for gas handling and for the observation of some absorption lines of HNO3, O3, and H2O in the 18–26.5‐GHz frequency band, and of the CS radical at 49 GHz are given.

ISSN:0034-6748    

DOI:10.1063/1.1143222

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A Bonse–Hart ultrasmall angle x‐ray scattering (USAXS) instrument employing both synchrotron and conventional x‐ray sources was constructed. The instrument could be used to determine the structure of systems with inhomogeneity sizes on the order of ∼1000 nm. The characteristics of the instrument by using synchrotron and conventional x‐ray sources were compared. The use of synchrotron radiation showed much improved features not only in scattered intensity, but also in angular resolution. The scattered intensity was increased by a factor of about 20. Therefore weaker scattering systems could be investigated. By using the synchrotron radiation, the deficiency of the Bonse–Hart camera could be compensated. An angular scan containing ∼30 data points in the scattering angle region smaller than ∼2 mrad with reasonable signal‐to‐noise ratio could be completed within 5–10 min for samples with reasonable scattering power. Therefore, kinetic studies could be possible if the half time of structural development in a system is of the order of hours. For static experiments, a conventional x‐ray source could be used more conveniently to obtain a scattering curve with similar quality as that by means of synchrotron radiation partially because the channel‐cut crystals were not optimized for the synchrotron beam divergence and partially because alignments could be accomplished at a more leisurely pace using the conventional x‐ray source.

ISSN:0034-6748    

DOI:10.1063/1.1143223

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new method has been developed which results in a major improvement in count rate of Bragg–Brentano‐type diffractometers. The method uses a focusing exit beam monochromator and a multichannel detector to achieve this improvement. The method is very efficient in eliminating background and can have very high resolution. Existing diffractometers can be easily modified to take advantage of this technique.

ISSN:0034-6748    

DOI:10.1063/1.1143224

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A molecular beam mass spectrometer system has been designed and constructed for the specific purpose of measuring the gaseous composition of the vapor environment during chemical vapor deposition of diamond. By the intrinsic nature of mass analysis, this type of design is adaptable to a broad range of other applications that rely either on thermal‐ or plasma‐induced chemical kinetics. When gas is sampled at a relatively high process pressure (∼2700 Pa for our case), supersonic gas expansion at the sampling orifice can cause the detected signals to have a complicated dependence on the operating conditions. A comprehensive discussion is given on the effect of gas expansion on mass discrimination and signal scaling with sampling pressure and temperature, and how these obstacles can be overcome. This paper demonstrates that radical species can be detected with a sensitivity better than 10 ppm by the use of threshold ionization. A detailed procedure is described whereby one can achieve quantitative analysis of the detected species with an accuracy of ±20%. This paper ends with an example on the detection of H, H2, CH3, CH4, and C2H2during diamond growth.

ISSN:0034-6748    

DOI:10.1063/1.1143225

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A high‐flux atomic oxygen source has been developed for the deposition ofinsitusuperconducting highTcfilms under conditions that require low chamber pressures (≤10−4Torr). The source uses a remote microwave plasma to generate the atomic species and is capable of producing an atomic oxygen flux greater than 2×1016cm−2 s−1. The O2dissociation efficiency of the atomic oxygen source is measured to be approximately 25%–30% for an O2flow of 5 sccm. This high efficiency is achieved by the combined effects of a boric acid surface treatment to minimize recombination on the quartz tube and the addition of N2to the oxygen plasma to increase the atomic oxygen yield. We have developed a treatment for the quartz surface that gives reproducible atomic oxygen flux with no degradation of the surface coating with repeated usage.

ISSN:0034-6748    

DOI:10.1063/1.1143226

出版商:AIP    

年代:1992

数据来源: AIP