摘要:

Following a few years after the invention of the charge-coupled device (CCD) in 1970, the discovery of charmed particles established the need for very high precision (few &mgr;m) detectors for tracking high energy charged particles. This review describes the work which has evolved over the past 20 years from these disconnected events, both as regards the application of increasingly refined CCDs to particle tracking (in particular as vertex detectors for identifying heavy flavor quarks and tau leptons), and also the advances in CCD detector design stimulated by these requirements. The lessons learned in this work should provide guidance for the construction of large arrays of CCDs or active pixel devices in the future in a number of areas of science and technology. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148870

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method for light polarization modulation is described. It allows us to independently modulate, at a high frequency, the four components of the Stokes vector of light using a single phase modulator. It works in a double-pass configuration: the polarization of light is modulated a first time by the phase modulator, and is then modified by a coupling object before being modulated a second time by the same modulator. The coupling object consists of multiple glass plates, oriented at the Brewster angle, acting as a partial polarizer and in a right angle prism acting as a phase shifter and back reflector. Its polarimetric properties are obtained from refractive index contrast effects, which provides optimized and constant properties over a wide spectral range. The phase modulator can be either an electro-optic modulator providing a very high-frequency capability (up to 100 MHz) or a photoelastic modulator providing a wide spectral range capability. It is robust because there is no moving part and simple to implement because of the presence of one modulation. It displays a high level of sensitivity because all the components are high-frequency modulated. Two applications using this modulator in a polarimeter or in a polarization states generator are described. The four modulations, having the same fundamental frequency, are easily demodulated by numerical data processing. Optimized demodulation processing, adapted to the different kind of phase modulator is described. Its adaptation taking into account the bandwidth limitation and the variation of the sampling phase, are finally presented in the case of a photoelastic modulator. ©1998 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1148811

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An intense, monochromatic, extreme ultraviolet (121.6 nm) light source has been constructed for testing extreme ultraviolet light rejecting filters. The source and detection system operates at atmospheric pressure, is physically compact, and is relatively inexpensive to build. A calibrated neutral density filter with a transmission of1×10−6is used as a reference. The light source has been used to measure transmissions as small as9×10−6quickly (in less than 1 min) with negligible background levels. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148812

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The laser interferometry is a frequently used diagnostics for plasma density measurements. The measurements in plasmas with no density gradients allow direct correspondence of the fringe shift and plasma density along the laser line of sight. The change of the interferometer contrast due to scene beam deflection in plasmas with density gradients reduces the fidelity of interferometer measurements due to the change in the contrast of the fringe. The analytic expression for the maximum acceptable deflection angle is derived, analyzed, and compared to the experiment. Ways to improve the accuracy of interferometer measurements are proposed. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148868

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Scatter plate interferometers provide a precise method to test the quality of concave mirrors. In this article we describe a method to integrate a scatter plate and a projection lens into a single binary micro-optical element, which is a crucial part of the scatter plate interferometer. We have designed an integrated element with the aid of a computer and fabricated it using thee-beam lithography method. We present experimental verification and some computer simulation results. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148813

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Holograms are thermally fixed in photorefractive lithium niobate crystals, i.e., they are recorded at temperatures between 130 and 180 °C. The setup is actively stabilized during recording against movements or vibrations of the interference pattern which especially occur during long-period writing at enhanced temperatures. Two different techniques are investigated: (1) Interference of the recording beams using one crystal surface as a beamsplitter yields a signal for stabilization. (2) Alternatively, one of the beams is periodically phase modulated and the beam-coupling signal is used for stabilization. Reproducible refractive index changes of thermally fixed holograms up to7.5×10−4are obtained with both stabilization techniques. However, the second method is advantageous for multiplexing experiments, because no readjustment of the beam-coupling stabilization system is required if the angles of the recording beams are changed. ©1998 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1148814

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe a digital cross-correlation instrument that employs a radio-frequency mixer and a radionuclide-scintillation light source to measure fluorescence lifetimes. The digital approach provides single-photon sensitivity and accurate lifetime analysis even at low sample concentrations. The unique characteristics of the scintillation excitation source, coupled with the simplicity of mixer-based signal processing, give this approach particular appeal over traditional instrumentation used for excited-state decay measurements. We discuss the system design and evaluate its performance using two optical configurations. The close-packed configuration provides an indication of the general fluorescence detection limits which can be expected from measurements made with scintillation-based light sources. After applying a procedure to correct for systematic error caused by the mixer diode-bias potential, the results from the digital system demonstrate lifetime accuracy over a range of sample concentrations (nM–mM). Finally, we develop a modified detection sensitivity parameter and calculate its value to be1×10−3 s photon−1 pathlength−1for our experiments. This new parameter can assist in the design of other scintillation-based lifetime measuring devices. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148815

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This article describes in detail a new method of data acquisition using an intensified charge coupled device (CCD) camera coupled with a monochromator as a time-resolved absorption spectrometer. The method is based on a full image transfer taking full advantage of the dynamic range of the CCD. The accumulation of several lines of the matrix is then limited by the 32-bit range of the computer calculation. The absorbance characteristics are a good signal-to-noise ratio and a large linearity domain (absorbances between 0.05 and 0.6) in the visible range (350–700 nm) with temporal gates less than 100 ns. The time-resolved absorption spectra obtained for two transient species in aqueous solution [CO3−and(SCN)2−] are presented and are in good agreement with those considered as reference and obtained with a multistep method with a classical monochromator-photomultiplier device. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148816

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

PoLIFEMo (Polarized Light Improved Flux Efficiency Monochromator) is the name of a spherical grating monochromator designed with the purpose of maximizing the photon intensity on a sample. The device is mainly conceived to improve performances of an x-ray emission spectrometer, whose limiting factor is often the counting rate. By keeping the exit slit fixed, it is possible to get a small spot size (∼35 &mgr;mvertically) on a sample placed just near the exit slit, without the need of postgrating refocusing optics. No entrance slit is used because of the low beam divergence, allowing the use of a virtual source in a converging beam geometry. The tuning of the output energy is done by translating and pitching the spherical grating. The resolving power is higher than 1000 over the whole energy range (500–1500 eV). A detailed analysis of the optical performances is given, mostly in comparison with the Dragon-type monochromator. The actual realization of the device is described, together with the specific motivations and the experimental performances. PoLIFEMo has been installed on beam line ID12B at the European Synchrotron Radiation Facility since July 1996. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148817

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Many experiments have been made in anin situminiature chamber for x-ray experiments using synchrotron radiation beam during sputtering. We have designed and fabricated a 2 in. circular magnetron sputtering gun for anin situreflectivity experiment. The head diameter of the gun is 6.4 cm, the height is 4.5 cm, and the length of the vacuum tight neck is 11 cm. The permanent magnet is isolated from water for prevention of corrosion. Only one O-ring is used for both insulation and vacuum seal. Therefore, its frame is simple and lightweight, with a volume about 1/5 compared to commercial units. The target holder is not fixed so it can be adjusted for the target thickness. In multi-target sputtering, the distance between target and substrate is closer than commercial equipment so deposition rate and uniformity of the deposited film can be increased. In order to check the performance of the newly sputtering gun,SnO2film on sapphire(0001) is grown, which turns out to be of the epitaxial single domain. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149019

出版商:AIP    

年代:1998

数据来源: AIP