摘要:

Angular responses have been measured for x‐ray collimators with half‐widths ranging from minutes of arc down to 10 arcsec. In the seconds‐of‐arc range, diffraction peaks at off‐axis angles can masquerade as side lobes of the collimator angular response. Measurements and qualitative physical arguments lead to a rule of thumb for collimator design; namely, the angle of first minimum in the Fraunhofer single‐slit diffraction pattern should be less than one‐fourth of the collimator geometrical full‐width at half‐maximum intensity.

ISSN:0034-6748    

DOI:10.1063/1.1134787

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The practical aspects of asymmetric crystal topography are described. In this technique, asymmetric Bragg diffraction is utilized to obtain a monochromatic and well collimated x‐ray beam large enough to cover the entire area of sample crystals. Thus, the recording of diffracted beams from a sample crystal provides topographic images of the entire sample crystal. Advantages of this technique are simplicity (no scanning device), excellent sensitivity to crystal imperfections (strain fields), and versatility. Information is given on the general alignment of the camera, magnification of the x‐ray beam width, preparation of the first crystal, and divergence of the beam due to the first crystal. The practical aspects of this topographic system are demonstrated using thick Cu and Ni crystals of various degrees of perfection. An inexpensive image intensifier is also described, which is used routinely to aid in the alignment of sample crystals.

ISSN:0034-6748    

DOI:10.1063/1.1134788

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A fast‐reading Pirani manometer with an electronically linearized response for gas pressures between 3×10−4and 0.5 Torr is described. The time constant of the manometer is 20 msec. Two NTC resistors are used, one for the sensor in the vacuum system and one for the reference at constant pressure. The pressure in the vacuum system is measured by analog computation of the power needed to stabilize the two resistors to equal temperature. By a relatively simple compensation circuit, changes in room temperature within ±10 °C can be eliminated to less than 1 per mille per degree. The manometer is built from inexpensive standard electronic components.

ISSN:0034-6748    

DOI:10.1063/1.1134789

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A 10‐&mgr;m detection system based on up‐conversion in proustite has been developed for the measurement of subnanosecond pulses of CO2laser radiation. This has involved the development of a ’’stretched‐pulse’’ Q‐switched Nd:YAG oscillator which can be synchronized with the output of a transverse discharge CO2laser. The 1.06‐&mgr;m radiation generated by this oscillator and the incoming 10‐&mgr;m radiation pass collinearly through a 0.6‐cm‐long proustite crystal which is oriented for type II phase matching. An investigation of the bandwidth of the up‐conversion process has shown that it should be possible to resolve 10‐&mgr;m pulses with durations of ∼5 psec. Using an image converter streak camera to record the 0.96‐&mgr;m sum frequency, the overall performance of the system has been investigated with the aid of a mode‐locked CO2laser operating at a pressure of 12 atm. The results have demonstrated that mode‐locked CO2pulses as short as ∼75 psec can be generated and that the temporal resolution of the complete detection system corresponds to that of the streak camera.

ISSN:0034-6748    

DOI:10.1063/1.1134790

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An interface using a simple calculator is described. The calculator display is encoded in BCD and drives the input of a programmable power supply, thus providing a versatile control. This gives the capability of producing a variable step ramp controlled by external clock pulses.

ISSN:0034-6748    

DOI:10.1063/1.1134772

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A study of the thin‐film detector (TFD) was made in which various light guide and scintillator film support configurations were tested for efficiency of light coupling. Masking of selected portions of the photomultiplier (PM) tube face revealed the extent to which emitted light was received at the exposed PM surfaces. By blocking off selected areas of the scintillator film surface from direct view of the PM tube faces, a measure of the light‐guiding efficiency of the film and its support could be estimated. The picture that emerges is that, as the light which is initially trapped in the thin film spreads radially outward from the ion entrance/exit point, it is scattered out of the film by minute imperfections. Optimum signals were obtained by a configuration in which the thin scintillator film was supported on a thin rectangular Celluloid frame inserted within a highly polished metal cylindrical sleeve.

ISSN:0034-6748    

DOI:10.1063/1.1134773

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A system combining polarization modulation with digital synchronous detection has been adapted for Raman spectroscopy. The apparatus permits an accurate determination of the polarization of scattered light and offers a number of other advantages over conventional measurements of Raman spectra. Brief derivations of formulas useful for analyzing data are given. The resolution of this apparatus is 87% of the theoretical maximum. The utility of the system is demonstrated by presenting the modulation Raman spectrum of sodium chlorate.

ISSN:0034-6748    

DOI:10.1063/1.1134774

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A modification to a commercial sputtering apparatus to provide real‐time monitoring of the optical thickness of sputtered films is described. The design utilizes a small vacuum window in the center of the targets, permitting the passage of a helium–neon laser beam. Modulation of the beam reflectance by the growing sputtered layer permitsinsituthickness measurement.

ISSN:0034-6748    

DOI:10.1063/1.1134775

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The combination of a weak rf discharge and a plasma current multiplier constitutes an effective dc power cathode which operates without electron emission, elevated materials temperature, or wall bombardment, etc. Such power cathodes may find application wherever filament cathode operation poses difficulties, as with reactive gases, or where filament replacement is undesirable.

ISSN:0034-6748    

DOI:10.1063/1.1134776

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Torque signals from a metal single crystal in a rotating magnetic field and the corresponding angular position of the rotating magnet, for both directions of rotation, were digitally recorded on magnetic tape at equal time intervals, with a maximum recording frequency of 18.8 data pairs per degree of rotation. The signals included induced, background, and de Haas–van Alphen effect torques. Only the induced torque is an odd function of rotation direction, and enhancement of the induced torque signals is achieved by subtracting the data obtained for one rotation direction from that for the other rotation direction. Computer analysis of recorded data yielded enhancement only if prior correction of each angular reading was performed to take into account the finite compliance of the torque magnetometer. The resulting enhanced rotation diagrams were plotted on a Calcomp plotter. The technique is also useful for continuous recording of anisotropy torque data from weakly magnetic samples, since the induced‐torque signals can be cancelled by adding the data from one rotation direction to those obtained from the other direction.

ISSN:0034-6748    

DOI:10.1063/1.1134777

出版商:AIP    

年代:1976

数据来源: AIP