摘要:

We have developed a circular dichroism spectrometer which will make measurements in the ultraviolet to 1350 Å. It is built primarily from commercially available components and is particularly simple in design. The instrument is linear and has a noise level over most of its range of less than 1×10−5OD units for a 16 Å spectral slitwidth and 10 sec time constant. The absorption and circular dichroism spectra of (+) 3‐methylcyclopentanone to 1350 Å are presented.

ISSN:0034-6748    

DOI:10.1063/1.1685367

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A relatively simple method for determining the delay of many electrical signals with respect to a common trigger (e.g., in capacitor banks) is described. Using the well known principle of time‐to‐pulse‐height conversion, a low leakage polystyrene capacitor is charged to a voltage proportional to the delay. A reed relay is used to disconnect the capacitor from the charging circuit, which permits the charge to be maintained on the capacitor for many seconds. Another reed relay is employed to connect each capacitor to an ADC when it is desired to digitize the charge on the capacitor. A change in delay of less than 1 nsec (with a full scale of 200 nsec) is reliably detected for many hundreds of signals at a parts cost of less than $10 per signal.

ISSN:0034-6748    

DOI:10.1063/1.1685368

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Design and performance of a bakable, stainless steel, ultrahigh vacuum apparatus for Auger electron spectroscopy, photoelectron energy distribution, and work function measurements are described. It is easily built, can be attached as an accessory to any vacuum system with a 6.3 cm i.d. flange, and is especially useful for the investigation of photoemitters.

ISSN:0034-6748    

DOI:10.1063/1.1685369

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The drift in resistance at a fixed temperature of a variety of carbon composition resistance thermometers has been measured in the temperature range 0.03–6 K. It is found that the drift in terms of an apparent &Dgr;T/Tis smaller for resistors having a smaller temperature sensitivity, and that these thermometers therefore have a better reproducibility in the usual meaning of the word. It is also shown that baking a resistor at temperatures of 300 to 400°C produces units essentially identical to unbaked resistors having the same room temperature resistance as the baked unit.

ISSN:0034-6748    

DOI:10.1063/1.1685370

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

We describe a method for measuring intensity correlations of light over times shorter than the resolving time of a photomultiplier. The method is based on sampling techniques and utilizes commercial electronics. The correlation times of photomultipliers are determined with an error smaller than 20 psec. The correlation characteristics of three fast photomultipliers, one C70045 and two XP1210, are measured for different anode voltages.

ISSN:0034-6748    

DOI:10.1063/1.1685371

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A ring of diffracted electrons is focused onto an electron detector by an on‐axis focusing electrode. In this way diffraction pattern data can be interpreted electrically and it is possible to obtain crystallographic data from crystal films while they are being deposited or while they are undergoing morphological changes. The system is insensitive to precise beam energy. In fact, for an on‐axis spherical focusing electrode the determination of crystal structure is essentially independent of the wavelength of the incident electron radiation. We believe this to be a unique result. In practice it is necessary to use a compromise electrode because there is no possible way to support or to apply voltage to an isolated sphere.

ISSN:0034-6748    

DOI:10.1063/1.1685372

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

We describe some novel uses of television for continuous monitoring and adjustment of a pulsed beam plasma experiment. Quantitative information can be obtained giving the position, size, and shape of the light emitting plasma. The absolute light intensity and the profile of the plasma can be separately obtained from a video scan analyzer. Time resolution of events occurring in a time span of ∼10 nsec can be achieved by incorporating a pulsed image intensifier ahead of the television camera tube. These techniques supplant photographic methods and augment information derivable from microwave and magnetic diagnostics. Some suggestions are made for future applications to other types of data analysis in physics and astronomy.

ISSN:0034-6748    

DOI:10.1063/1.1685373

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A slit system is described in which the slit jaws and baseplate are made of materials of different thermal expansion coefficients. By changing the temperature of this slit system the slitwidth can be controlled. The operating range is from 1 &mgr; to approximately 0.1 mm. The system is rugged, bakable, and still extremely precise; thus it is especially useful for uhv systems. It may be controlled remotely without further accessories. A thermally controlled slit system built for use in a mass spectrometer has been constructed and is described.

ISSN:0034-6748    

DOI:10.1063/1.1685374

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Two methods are developed for the measurement of fluid velocity gradients using a laser‐Doppler anemometer. In the first method the velocity gradient is found by a single measurement of the bandwidth of the laser‐Doppler signal spectrum. In the second, velocity gradients very close to a wall are calculated from the amount the signal spectrum shifts in frequency for a small change in the position at which the spectrum is measured. Both methods are examined theoretically and experimentally.

ISSN:0034-6748    

DOI:10.1063/1.1685375

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A semiconductor diode image tube system has been built which has the characteristics of a good photomultiplier tube but which can simultaneously measure light intensity at 38 different positions. Tube dark current is 0.02 count/sec/position. A tube with up to 1000 elements appears feasible.

ISSN:0034-6748    

DOI:10.1063/1.1685376

出版商:AIP    

年代:1971

数据来源: AIP