摘要:

A compact, dual‐beam laser deflection system was built, mainly from commercially available parts. While the detector and electronics yielded noise levels at the theoretical level for the detector, pointing instability of the laser led to an increase in noise by a factor of about 103. The dual‐beam arrangement gave only a factor of about 4 improvement over the single‐beam mode due to alignment and drift problems. Further improvement requires a feedback system to minimize signal arising from common‐mode beam displacements.

ISSN:0034-6748    

DOI:10.1063/1.1138135

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We have developed a Pockels driver, based on field‐effect transistors and a microwave tube. This system, capable of generating double voltage steps, operates reliably at repetition rates as high as 10 kHz.

ISSN:0034-6748    

DOI:10.1063/1.1138086

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An ellipsometer with two photodetectors and no other optical elements is described. In general, each detector has a partially specularly obliquely reflecting surface and generates an electrical signal proportional to the fraction of radiation it absorbs. It is not essential (but desirable) that the two detectors absorb all of the incident radiation. The output signals of the two detectors, with parallel or nonparallel surfaces, are enough to determine the degree of linear polarizationPof incident light with respect to one set of transverse orthogonal axes. If the assembly of two parallel detectors is rotated around the light beam by an angle (of 45°), a new degree of linear polarizationP’is measured. FromPandP’the (generally elliptic) polarization state of incident totally polarized light can be completely determined, except for handedness. A calibration procedure for this two‐detector ellipsometer (TDE) is given.

ISSN:0034-6748    

DOI:10.1063/1.1138087

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A combination of a 32×32‐element silicon‐diode matrix and an Apple II computer is used to record and analyze Fabry–Perot interference ring patterns. The main advantage over conventional methods consists in the possibility of selecting the spectral resolution after registration and in the absence of alignment problems. Application of an image converter tube with VUV transmitting window in front of the matrix extends the applicability of the device to UV and VUV spectra.

ISSN:0034-6748    

DOI:10.1063/1.1138088

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The time‐resolution capabilities of two 28‐mm‐diam side‐on photomultiplier tubes, Hamamatsu R928 and RCA 931‐A, were studied by point illumination of the photocathode surface with the attenuated beam of a synchronously pumped dye laser (10‐ps pulse width). Using the time‐correlated single photon counting technique, an apparatus response of 112 ps FWHM was obtained. Contour maps giving the time shift and the width of the response were constructed as a function of the point of illumination of the photocathode surface. These data permit selection of the optimized photocathode region to be illuminated during fluorescence decay measurements.

ISSN:0034-6748    

DOI:10.1063/1.1138089

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We present the experimental set up of a microwave Fourier‐transform spectrometer for the entireKband from 18 to 26.4 GHz. It is hereby shown that this type of spectroscopy is achieved above 18 GHz. Advantages and disadvantages are discussed. The performance is illustrated by the recordings of rotational transitions of various molecules.

ISSN:0034-6748    

DOI:10.1063/1.1138090

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We describe the design, schematics, and performances of a low‐noise preamplifier for pulsed nuclear‐magnetic‐resonance (NMR) experiments in the range 0.1–1 MHz with a noiseless (cooled below liquid‐helium temperature) pickup coil. This preamplifier operates at room temperature and exhibits an order‐of‐magnitude improvement in noise power per unit bandwidth over previously used preamplifiers. All significant contributions to the noise are carefully identified and a detailed analysis of the noise performance of a cascode differential pair of JFETs is given. Application to very‐low‐temperature thermometry by NMR in pure platinum powder is discussed as a practical example.

ISSN:0034-6748    

DOI:10.1063/1.1138091

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

When a Si(Li) solid‐state energy dispersive detector is used to collect x‐ray photons with energies below 2 keV the characteristic peaks in the spectrum show significant deviations from the ideal Gaussian shape observed for higher energy photons. This effect is due to incomplete collection of the charge deposited by the incident photon in the diode. The magnitude of this effect, and the resultant distortion of the spectrum, can be computed by means of a Monte Carlo simulation which models the detector in terms of the three parameters which characterize it, junction depth, diffusion length, and surface recombination velocity. For values of these parameters typical of commercial detectors it is found that the incomplete charge correction can be as high as 30% for a line such as NK&agr;at 400 eV. By matching simulated and experimental spectral shapes, quantitative corrections for each x‐ray line of interest can be computed. The results suggest that alternative design strategies for detectors might permit a higher quality of performance to be achieved at low energies.

ISSN:0034-6748    

DOI:10.1063/1.1138092

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A two‐color pyrometer has been designed, constructed, and used to measure the ignition temperatures of metals and metal alloys. Cylindrical metal and metal alloy specimens were ignited by a focused cw CO2laser beam in a cool, static, pure oxygen environment. The pyrometer operates in the near‐infrared at two narrow spectral regions, with a nominal bandwidth of 10 nm centered at 0.9051 and 1.06 &mgr;m, and has a temperature range from 1000 to 4000 K. In the present design the temperature of a spot, ∼0.5 mm in diameter, can be recorded with a maximum time resolution of 25 &mgr;s and with an accuracy of a few percent. Results of CO2laser ignition of cylindrical specimens of 6061 aluminum alloy and 302 SS in a pure oxygen environment were obtained from the two‐color pyrometer and were compared with those obtained from a thermocouple placed inside the specimen near the laser‐irradiated surface.

ISSN:0034-6748    

DOI:10.1063/1.1138093

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The principle of the change in the ‘‘decay time’’ of the fluorescence of a small sample of neodymium in a glass matrix, excited by infrared radiation from a high‐power light emitting diode has been used in the construction of a fiber‐optic temperature sensor. Such a device is an inexpensive transducer and has demonstrated a fiber‐optic sensor not requiring referencing to the intensity of the exciting radiation.

ISSN:0034-6748    

DOI:10.1063/1.1138094

出版商:AIP    

年代:1985

数据来源: AIP