摘要:

A technique for obtaining positional information using a Ronchi grating is described. By employing the grating as a diffraction element, modulation of the phase of a coherent light beam is accomplished. The phase contains information as to the position of the beam on the grating surface. The use of an interference technique allows one to monitor the light phase, and therefore the beam’s position. Using a single grating, directional as well as positional information is obtained in two dimensions. Advantages and other system characteristics are described.

ISSN:0034-6748    

DOI:10.1063/1.1134502

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A glass‐sealed Langmuir probe was developed to get accurate information on the ionospheric plasma. An electrode sealed in a glass tube is first baked in low pressure and tipped off the pumping system to keep the electrode surface clean. An essential advantage of the glass‐sealed Langmuir probe is that it will not require the rapid sweeping of a probe voltage for reliable data acquisition. It is noted that the glass‐sealed Langmuir probe is strongly recommended for the measurement of energy distribution of thermal electrons by the second harmonic method.

ISSN:0034-6748    

DOI:10.1063/1.1134476

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A circuit is described which will adapt a laser Doppler velocimeter using real‐time spectrum analysis for automatic velocity tracking. The circuit provides an analog voltage which is proportional to velocity by tracking the position of crossing of a selected intensity level on the spectrum analyzer output. Examples of applications to the study of protoplasmic streaming and simulated hemodynamics are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134477

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A simple mesh wall ionization chamber (representing a ’’wall‐less’’ ionization chamber) is described for air dose measurement. The effects of insulators and air circulation in the vicinity of the chamber were studied. An outer shield mesh placed around the collecting chamber eliminates the adverse effects of air circulation and electrostatic disturbances around the detector. The detector can be used effectively to measure that component of dose due to low energy electrons or x rays which are normally stopped by the walls of conventional dose measuring instruments. The mesh ion chamber is particularly useful in measuring dose distribution in and around a radiation field. This chamber approximates a free air ion chamber that can be used at low, as well as high, energies once electron equilibrium is achieved. The chamber was tested using137Cs gamma radiations and gives good agreement with a model 570 Victoreen R meter.

ISSN:0034-6748    

DOI:10.1063/1.1134478

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Two sample holders for operation at liquid helium temperatures are described that provide rotation through large angles about two orthogonal axes, in addition to a possible rotation about the long axis of the cryostat. The basic motion is derived from a thread or wire rather than from gears.

ISSN:0034-6748    

DOI:10.1063/1.1134479

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An apparatus for the measurement of optically detected magnetic resonance (ODMR) in zero magnetic field at 4.2 K using commercially available parts is described. A simple electronic analogue device is used to obtain kinetic data from ODMR transients in a fast and reliable way. From these data decay rates of the three spin levels of the lowest molecular triplet state can be obtained, whereas populating rates can be determined within defined limits. Since the apparatus is suited for unguarded operation during long periods of time, signal averaging of weak signals, e.g., from biological molecules, is particularly easy. Kinetic data have been obtained for dihydroporphin, which can be considered as the structural basis for chlorophyll:k1= 121±12 sec−1;k2=277±28 sec−1;k3=22±2 sec−1; 0.28<P1<0.43;P2=1;P3<0.08, wherekiandPiare the decay and populating rates of theith spin level.

ISSN:0034-6748    

DOI:10.1063/1.1134480

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A polarization modulated birefringence scheme allowing continuous measurements on single domains at phase transitions has been developed. Measurements on the 184 K transition in KMnF3clearly revealed the initial first order nature of the transition and yielded improved values for the critical exponent and transition parameters.

ISSN:0034-6748    

DOI:10.1063/1.1134481

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The sapphire cylindrical resonator with H112wave directly coupled to the waveguide is the most advantageous of those hitherto investigated operating in the X band. It has a Q factor of 2500 and a very weak, linear pressure dependence of the resonance frequency with a coefficient of 6.5×10−4kilobar−1.

ISSN:0034-6748    

DOI:10.1063/1.1134459

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A diamond anvil cell has been adapted for determination of the strain ellipsoid in a polycrystalline sample. An x‐ray beam (MoK&agr;) is directed through the sample perpendicular to the loading axis. Since the diamond anvils are transparent to MoK&agr; radiation, a complete cone of diffraction is available from each set of crystallographic planes (hkl). These cones produce rings on a flat film placed in front reflection geometry. From the ellipticity of these rings it is possible to calculate directly the strain ellipsoid. Material strengths as a function of pressure can then be calculated.

ISSN:0034-6748    

DOI:10.1063/1.1134460

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An easily constructed circuit for a nuclear quadrupole resonance spectrometer suitable for searching for resonances in solids is given. The oscillator of the spectrometer is operated in the self‐quenching mode, and incorporates a simple ratemeter for the manifestation of detection. Graphs of signal intensity for differing quench frequencies, as the radio frequency is scanned through resonance, are given for paradichlorobenzene and sodium chlorate polycrystalline samples at room temperature. The dependence of the detection signal upon the quench frequency is quite noticeable in the graphs.

ISSN:0034-6748    

DOI:10.1063/1.1134461

出版商:AIP    

年代:1976

数据来源: AIP