摘要:

An apparatus for the study of the fragmentation of MeV molecular ions is described. The system permits high‐resolution measurement of the joint distribution in energy and angle for fragment ions of selected charge and mass. Two movable detectors allow the study of spatial and temporal correlations among up to three fragments resulting from a single dissociation event. All experimental parameters are monitored, controlled, displayed, and recorded by a computer system that uses a linked network of four processors. Real‐time, computer‐generated color graphics are employed to give a visual rendition of the relation between the detector positions and the trajectories of outgoing fragments.

ISSN:0034-6748    

DOI:10.1063/1.1137433

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

This paper deals with the calculation of the detection efficiency in total cross‐section measurements for two geometries: rectangular beam–rectangular detector of equal (finite) dimensions and circular beam–circular detector. The solutions are given in analytical and graphical form. The use of the term ‘‘angular resolution’’ is discussed and a new definition is proposed.

ISSN:0034-6748    

DOI:10.1063/1.1137434

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The relationship of EerNisse’s technique for measuring small dilatations caused by irradiation with short‐range particles, which utilizes a metallized thin plate mounted as a cantilever below whose free end an electrode is placed (forming a capacitor), to a photoelastic technique and to an interferometric technique are derived. The effects of stray capacitance, the fringing field of the capacitor, the clamping stress on the cantilever plate, the electrical resistance of the metallic coating, the charging of the tank circuit of which the capacitor is an element, the flange bolting stress, and the beam heating are assessed, and examples of the manner in which they contaminate the data are given.

ISSN:0034-6748    

DOI:10.1063/1.1137435

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Irradiating a solid with short‐range particle often induces a net volume change in the range zone which results in a shallow layer of stressed material. Micron‐depth volume dilatations in the part‐per‐million range can be studied using cantilever mounting of a long, thin, metallized specimen, whose stress‐induced bending perturbs the capacitance between the cantilever and a small counterelectrode mounted close to the unirradiated face. This approach has been used successfully by many workers for more than 20 yrs. Elsewhere we have reported the construction of a highly sensitive caltilever/capacitor apparatus and its application in the first accurate measurements of ionization dilatation phenomena in fused silica and grown SiO2at low‐electron energies. In this paper we outline key details of apparatus design and experimental technique for successful cantilever/capacitor work. Many contrasts with the work of Primak and Monahan [Rev. Sci. Instrum.54, 544 (1983) (preceding paper)] are pointed out. We also highlight previous short‐term annealing results which make it clear that the compaction of silica will appear to be significantly less in optical measurements made hours after irradiation than in our cantilever/capacitor measurements made minutes after irradiation.

ISSN:0034-6748    

DOI:10.1063/1.1137436

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A simple two‐crystal spectrometer was constructed using a commercial single‐crystal spectrometer, i.e., the second crystal and the detector were attached on the 2&thgr; arm of a single‐crystal spectrometer. The angle between the second crystal and the detector is preset to an optimum angle for the measurement region of interest. The condition for geometrically ideal analysis can be satisfied by rotating the &thgr; axis and detector arm (2&thgr; arm) at a rotation ratio of 1:3 using an external pair of gears whose ratio is 3:1. The wavelength can be directly read according to Bragg’s diffraction law, like a commercial two‐crystal spectrometer. We measured sulphur‐K&bgr; spectra for several sulphur compounds. We conclude, from several measurements, that the spectra obtained with a high‐resolution can be an important and powerful tool for the study of the valence band and can also be applied to chemical‐state analysis.

ISSN:0034-6748    

DOI:10.1063/1.1137437

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A 10‐Hz coherent anti‐Stokes Raman spectroscopy (CARS) instrument capable of simultaneous thermometry and N2‐concentration measurements in a turbulent flame has been designed and constructed and is described in detail. The instrument employs the doubled output of a pulsed Nd:YAG laser for pumping a broadband dye laser and also for the CARS pump beam. The broadband dye laser is used to excite, during a single pulse, the entireQBranch of N2, the CARS signal of which is recorded by a multichannel analyzer. Special problems which were encounted with the multichannel analyzer include signal retention and limited dynamic range. The former was greatly reduced by employing cleansing scans between laser firings, and the latter was circumvented by employing a multiple beamsplitter arrangement in which the CARS signal was divided into four separate intensity regions, each of which covered a specific temperature range. The 10‐Hz operation of the instrument required the use of a mass storage device such as an 800‐bits‐per‐inch tape. CARS data recorded and digitized by the multichannel analyzer were transferred via machine‐coded instructions to a minicomputer for storage on tape. Analysis of the CARS data consisted of a nonlinear least‐squares fit of the CARS bandshape for thermometry and integration of the CARS signal for N2concentrations. CARS measurements in a near‐stoichiometric premixed propane flame and a turbulent diffusion flame are reported. Results of calibration measurements indicate that uncertainties of 4% in temperature and 6% in concentration are obtainable with this instrument.

ISSN:0034-6748    

DOI:10.1063/1.1137438

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Laser‐induced fluorescence has been employed to obtain two‐dimensional images of the spatial distribution of a vapor in the ground state with nanosecond resolution. The method has a wide range of potential applications, as it can be used to observe any species which has energy levels accessible to tunable laser systems. In the application we describe, aluminum vapor was observed jetting from spark gap electrodes and diffusing throughout the gap volume.

ISSN:0034-6748    

DOI:10.1063/1.1137439

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The construction and performance of a combined reaction cell and sample exchange lock for studies of surface reactions at pressures up to a few atmospheres is described. In combination with a specially designed sample holder this construction allows simple and rapid transfer of the sample betwen the ultrahigh vacuum system and the reaction cell. The reaction cell is a self‐contained unit that can be mounted on, e.g., a 2 3/4 ‐in. Con‐Flat flange (or any other vacuum port with an I.D.≥38 mm). The sample holder can be mounted on any commerical sample manipulator. In both the high‐ and low‐pressure positions the sample can be heated and cooled. Results are presented for the times involved in moving the sample from high‐ to low‐pressure environments, pump‐out times, etc. The use of this equipment in studies of the catalytic activity of Pt for the H2oxidation is briefly described.

ISSN:0034-6748    

DOI:10.1063/1.1137440

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We report a new type of beam splitter capable of producing a division of light in a polarization‐independent manner. Most off‐axis beam splitters have a pronounced polarization dependence. An experimental device with a splitting ratio of about 7 dB varied less than ±0.1 dB as a function of incident linear polarization. The device is fabricated from a thin plate of suitably oriented, uncoated, crystalline quartz.

ISSN:0034-6748    

DOI:10.1063/1.1137441

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A digital scanning polarimeter is described. It measures the local variations of the rotatory power of a thin liquid crystal target. This device is used for thermal imaging purposes. The incident scanning beam is split after traversing the target in two parts and then analyzed with two analyzers and detectors. Taking into account the photon noise, the existence of an optimal angle of the analyzer azimuth is shown. A numerical example is given.

ISSN:0034-6748    

DOI:10.1063/1.1137442

出版商:AIP    

年代:1983

数据来源: AIP