摘要:

Studies are reported on frequency drifts in extended-cavity diode lasers caused by external effects, such as changes in temperature and air pressure. A laser system operating at 780 nm has been constructed utilizing low expansion materials and such mechanical structures that compensate for the external effects. By placing the laser system in a pressure-proof and temperature-controlled housing, a relative frequency stability of better than 10−10(40 kHz) is obtained for integration times of 10 &mgr;s to 10 s. The drift of the laser frequency caused by spectral aging of the diode laser is about 3 MHz/h. As a consequence of high passive stability, the variations of the laser intensity are also greatly reduced to a relative drift value of 4×10−5/h. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147810

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article, a 1 ns excimer laser pulse was obtained successfully from an ultraviolet preionized XeCl laser using a direct wave-clipping technique with some improvements over the conventional scheme in consideration of obtaining more suitable discharge and steeper front edge of original light pulse. The effects of laser operation stability and optical setup of the experiment scheme on output characteristics are discussed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147753

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A Fresnel phase zone plate for hard x ray was fabricated by physical vapor deposition alternating transparent and opaque layers onto a fine gold wire core 47 &mgr;m in diameter. The zone plate, which is comprised of 25 pairs of alternating Ag and C layers, is designed to operate with a focal length of 124 mm for a parallel beam at 8.1 keV. The thickness of the zone plate is less than 10 &mgr;m and is capable of operating as a phase zone plate. Using the brilliant monochromatized x-ray beam from the TRISTAN Main Ring, with an undulator, the minimum focal spot size attained for the first order focal beam was 0.5 &mgr;m&fgr;. The light collecting efficiency was determined to be near 11&percent;. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147851

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The article demonstrates the feasibility of quantized positioning and moving scanning x-ray interferometers by feedback of traveling fringes. Two new features, feedback and equilibrium quantization, combine to yield accurate positioning and movement by successive transitions between equilibrium positions. In contrast with feedforward positioning and movement, piezoelectric linearity and stability are not subjected to strict conditions. In preliminary experiments, the performances of an x-ray interferometer were greatly improved and servo-movements up to 0.4 &mgr;m were achieved and tracked with picometer resolution. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147805

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A primary problem in collecting and analyzing x-ray absorption fine structure (XAFS) from crystalline samples, including thin films grown on crystalline substrates, is the contamination of the x-ray absorption spectrum by diffraction events. To address this limitation, a total electron-yield detector equipped with a spinning stage was developed. Samples of (MnZn)Fe2O4, grown on single crystal (100) MgO substrates, were used to illustrate its effectiveness as an electron-yield detector and in eliminating diffraction-related contamination from the XAFS. The design and performance characteristics of this detector are presented and discussed.

ISSN:0034-6748    

DOI:10.1063/1.1147815

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The development of a novel static Fourier-transform spectrometer based on two Wollaston prisms, two polarizers, and a compact two-dimensional detector array is described. The wavelength calibration is fixed by the geometry of the prisms and the detector array and is therefore inherently stable. The Wollaston prisms are fabricated from materials with opposite sign of birefringence which gives a significantly increased field of view compared with existing Wollaston prism based Fourier-transform spectrometers. The spectrometer operates in the visible region of the spectrum, has a resolution of350 cm−1, an aperture of6×4.6 mm, and a field of view of±10°. The optical assembly is interfaced to a laptop computer resulting in a rugged, portable instrument with no moving parts. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147857

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Detecting the ultraviolet scintillation light of the liquefied rare gases, in particular liquid xenon, requires the use of photomultiplier tubes (PMTs) in a temperature range where their operation is not ensured by manufacturers. Simultaneously, monitoring of the PMTs should be done in the visible for technical reasons. Bialkali photocathodes, that present high quantum efficiency and low dark noise, exhibit a very strong increase of electrical resistivity upon cooling that, apart from other reasons, can lead to operation failure at low temperature. Photomultiplier tubes with bialkali photocathodes and quartz windows (two EMI 9750Q and one Philips XP 2020Q) and another with S11-type photocathode and glass window (FEU 85A) were tested down to −160 °C with a pulsed light source, both in the visible region and at the xenon scintillation wavelength in the vacuum ultraviolet. For the visible range, the results obtained with bialkali photomultipliers display a sharp drop of response at about −100 °C, depending on the count rate, regardless of the wavelength, and a shift of the spectral sensitivity curve towards shorter wavelengths. Concerning the vacuum ultraviolet region, a significant increase of the response was observed between room temperature and that of the efficiency drop. For some photomultiplier tubes, the response as a function of temperature was observed to depend on their past history, probably due to mechanical effects arising in the multiplier system upon cooling. It is concluded that photomultipliers with bialkali photocathode can, in principle, be used for the detection of liquid xenon scintillation, although they have to be carefully monitored while in operation. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147866

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have measured the absolute quantum yield for alkali halides and the spectral transmission for alkaline earth fluoride windows to find an optimized bandpass combination for a solid state ultraviolet (UV) photon detector for inverse photoemission. The best resolution achieved is 0.33 eV (full width at half-maximum), being obtained with the NaCl photocathode–BaF2window combination. This, however, leads to a rather low quantum efficiency of 0.3&percent;. The combination NaCl–SrF2chosen for our detector offers a resolution of 0.42 eV (full width at half-maximum) with a maximum quantum efficiency of 2.5&percent; at 9.50 eV photon energy. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147844

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Three variations of charge coupled device (CCD) based x-ray detectors have been constructed and evaluated, two of which are used for routine data collection on small angle x-ray diffraction beamlines at Princeton. The first detector consists of a commercially available CCD camera system lens coupled to the output of a four-stage magnetically focused image intensifier. The second system, assembled to gather test data, consists of a CCD fiber-optically coupled to an x-ray conversion phosphor via a 5:1 reduction fiber-optic taper. The final detector configuration was comprised of this fiber-optic taper system with the addition of a single stage proximity-focused image intensifier. Rationale is given for choosing components to be used in the assembly of CCD-based detectors. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147611

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

For the first time, to the best of our knowledge, the electron-hole pairs generated in a material by a single photon ionization event have been detected using a microwave technique. The detection mechanism is based on the attenuation of a resonant electromagnetic wave and, unlike conventional particle detectors, does not rely on charge or scintillation light collection. The current technique has an inherent fast response (microwave frequency of 9 GHz) and is not affected by the problems associated with charge sweeping and/or light measurements. Experimental results for single high energy x-ray photons absorbed in high purityp-germanium are presented. The results demonstrate the potential for a new class of gamma/particle detectors and a useful method to study the kinetics of particle interactions in materials. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147653

出版商:AIP    

年代:1997

数据来源: AIP