摘要:

In this paper we discuss passive vibration isolation systems for ultralow temperature gravitational radiation detectors, using a detector at Stanford University as the primary example. We review the basic theory of such isolation systems and describe methods of analysis for one‐degree‐of‐freedom isolators. With these methods we derive fundamental constraints on the performance of gravitationally loaded isolators. Next we discuss general design considerations, optimization, and detailed analysis of six‐degree‐of‐freedom isolators. We conclude with experimental data from isolators designed for the Stanford gravitational radiation detector.

ISSN:0034-6748    

DOI:10.1063/1.1143277

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A novel electron analyzer for rapid x‐ray photoelectron spectroscopy (XPS) spectra acquisition and operation at 10−5Torr pressure was modeled, constructed, and tested. The electron energy analyzer uses spherical retarding grids in conjunction with a post‐monochromator to achieve bandpass operation, while maintaining the large transmission of a conventional retarding grid analyzer. The goal of modeling was to investigate the interaction between the retarding grids and the post‐monochromator on the analyzer transmission and resolution. Both electron scattering at the retarding grids and fringe electric fields were found to be key factors in the overall analyzer performance. Based on the modeling results, an electron energy analyzer was constructed and tested using both gold samples and thin polystyrene films. 20‐eV‐wide scans could be obtained in 100–200 s with analyzer resolution of 1.0 eV. Monitoring of the polystyrene surfaces during and after exposure to molecular and atomic fluorine, indicated that the analyzer is useful for the collection of rapid, medium resolution XPS scans during the exposure of surfaces to reactive beams at background pressures as high as 10−5Torr.

ISSN:0034-6748    

DOI:10.1063/1.1143278

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An ultrahigh vacuum chamber has been developed for structural analysis of adsorbed films and single‐crystal surfaces using synchrotron x‐ray diffraction. It is particularly well suited for investigations of physisorbed and other weakly bound films. The chamber is small enough to transport and mount directly on a standard four‐axis diffractometer and can also be used independently of the x‐ray diffractometer. A low‐current, pulse‐counting, low‐energy electron diffraction/Auger spectroscopy system with a position‐sensitive detector enablesinsitucharacterization of the film and substrate while the sample is located at the x‐ray scattering position. A closed‐cycle He refrigerator and electron bombardment heater provide controlled substrate temperatures from 30 to 1300 K. The chamber is also equipped with an ion sputter gun, a quadrupole mass spectrometer, and a gas handling system. Details of the design and operation of the instrument are described. To demonstrate the performance of the instrument, we present some preliminary results of a study of Xe physisorbed on the Ag(111) surface.

ISSN:0034-6748    

DOI:10.1063/1.1143279

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Submonolayer sensitivity to thin‐film nucleation and growth in real time on the millisecond scale has been achieved with a unique rotating polarizer multichannel ellipsometer. Continuous spectra in the ellipsometry angles {&psgr;(hv),&Dgr;(hv)} consisting of ∼50 points fromhv=1.5 to 4.3 eV have been obtained with acquisition and repetition times as short as 16 and 32 ms, respectively. As an example of the instrument capabilities, we present results for hydrogenated amorphous silicon (a‐Si:H) growth onc‐Si by plasma‐enhanced chemical vapor deposition at a rate of 400 A˚/min. In this example, the acquisition and repetition times are both 64 ms, and at this speed a precision in (&psgr;,&Dgr;) of ∼0.02–0.03° is obtained under optimum conditions. We observea‐Si:H nucleation in the first 2 s of deposition, and detect relaxation of nucleation‐induced surface roughness with submonolayer sensitivity.

ISSN:0034-6748    

DOI:10.1063/1.1143280

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A novel small‐period wiggler constructed of edgy‐wound bifilar‐helical conducting sheets with ferromagnetic cores, intended for free‐electron lasers (FELs), is presented, and the performance characteristics of the wiggler prototype with 10‐mm period are measured. A field as high as 500–1000 G has been obtained. It is feasible to make a Raman FELs with this type of wiggler operating in the wavelength range of millimeters and submillimeters with a low electron energy (<500 keV) beam.

ISSN:0034-6748    

DOI:10.1063/1.1143281

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this article we discuss how pseudorandom sequences are generated for use in cross‐correlation modulation experiments and present means for generating all pseudorandom sequences (modulo‐two) that have a maximum length ofN=2n−1, withn=2–12. We explain the criteria that the pseudorandom sequences must satisfy, and find the set of recursion coefficients which are used to generate the pseudorandom sequences. These sets of recursion coefficients were calculated forn=2–16, withn=2–12 being explicitly presented in this article. We also explain how each set of recursion coefficients can be used to generate maximum length pseudorandom sequences of length sufficient for use in cross‐correlation chopping.

ISSN:0034-6748    

DOI:10.1063/1.1143282

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A compact interferometer using a grating beamsplitter is reported. The phase of the interference signal was adjusted by using the moire effect of the gratings, so that a small optical path difference was compensated precisely by the magnified displacement of the grating. The optical system was analyzed theoretically on the basis of the Fourier optics. For the interferometric measurement in the microscopic region, a compact optical system was assembled from the microscopic objective and the 25‐&mgr;m gratings. The characteristics of the proposed interferometer were investigated in the measurements of film thickness, piezoelectric vibration, and photoacoustic effect.

ISSN:0034-6748    

DOI:10.1063/1.1143283

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Interferometric thermometry is a promising noncontact technique for measuring the temperature of transparent substrates (with polished front and back surfaces) from thermally induced changes in sample thickness and refractive index. However, for substrates of uniform thickness, the technique is not sensitive to thedirectionof temperature change, thus restricting its use to situations in which the temperature variation is monotonic. In this paper, we present some new schemes for interferometric thermometry based on the wavelength modulation capabilities of the distributed feedback laser diode. These schemes allowboththe magnitude and direction of temperature change to be determined. One scheme utilized to measure temperature changes in a silicon wafer during thermal cycling is described in detail. In addition, the calibration factors required to convert the thermally induced reflectance oscillations (‘‘fringes’’) of known‐thickness samples into temperature change are provided for Si and GaAs at wavelengths near 1.5 &mgr;m.

ISSN:0034-6748    

DOI:10.1063/1.1143284

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A fiber‐optic sensor for continuous temperature measurement from room temperature to ≳700 °C is presented. The device is based upon the excitation of the synthetic crystal alexandrite with light from a diode laser operating at 670 nm and the measurement of its fluorescence lifetime. A simple low cost optical configuration is described together with the introduction of a new effective signal processing scheme for fluorescence lifetime measurement, and a high sensitivity and repeatability are observed, at best ±1 °C.

ISSN:0034-6748    

DOI:10.1063/1.1143285

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

4He+and D2+have been separated with a conventional quadrupole mass spectrometer by using the second stability zone in the Mathieu diagram. The minimum resolving power needed for the separation of4He+and D2+is 161. A resolution of 320 defined by the full width at half maximum was attained at an ion energy of 14.6 eV in the experiment.

ISSN:0034-6748    

DOI:10.1063/1.1143286

出版商:AIP    

年代:1992

数据来源: AIP