Volume 77, Issue 1, January 2006
Index of content:
- OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS
77(2006); http://dx.doi.org/10.1063/1.2162752View Description Hide Description
We have developed a compact retarding-type Mott spin polarimeter with a large collection angle at the Hiroshima Synchrotron Radiation Center and obtained a reliable value of the effective Sherman function by a self-calibration method. The spin polarization of secondary electrons was evaluated by extrapolation of the left-right scattering asymmetry at the zero energy-loss limit, which enabled us to obtain the effective Sherman function and the figure of merit of our polarimeter at different operating conditions.
77(2006); http://dx.doi.org/10.1063/1.2162448View Description Hide Description
We report on a compact, inexpensive, and durable extended-cavity diode laser (ECDL) of an original mechanical concept. The independent temperature control of a laser diode and an extended cavity provides a low-frequency drift. The linewidth of a few hundred kilohertz was measured by taking a beating of two identical ECDLs. The continuous tuning range of about is achieved by the synchronous scan of two piezotransducers translating and rotating an external diffraction grating. The laser has been used in high-resolution spectroscopy, atom cooling, metrology, and precise interferometry.
77(2006); http://dx.doi.org/10.1063/1.2150823View Description Hide Description
An active control system is described for the automatic alignment of the mirrors in a two-beam interferometer. From an initial unaligned position the active control system determines the degree of misalignment and adjusts the relative mirror positions accordingly. An embodiment of the system is described for a Michelson interferometer in which one of the mirrors is mounted upon three piezoelectric transducers(PZT) arranged so that they can both tilt and retard the mirror. Laser sources and corresponding photodetectors are also incorporated such that a control system can use the PZT actuators to produce a series of mirror movements relative to the fixed mirror and give a set of two-dimensional diffraction patterns—one for each of the laser photodetectors. Amplitude and phase information is extracted from these patterns which enables the control system to align the mirrors such that the diffraction pattern maxima is at the center of the instrument central photodetector. In a further stage of the control algorithm, the alignment accuracy is refined using information from the laser photodetectors during retardation of the mirror. In this manner, the initial mirror alignment, maintaining that alignment during retardation and diagnosis of possible misalignment, become part of a single active control technology for instrument alignment.
Development of high temporally and spatially (three-dimensional) resolved formaldehyde measurements in combustion environments77(2006); http://dx.doi.org/10.1063/1.2165569View Description Hide Description
In the present article a multi-YAG laser cluster and a framing camera have been applied for ultrahigh framing rate and three-dimensional measurements of formaldehyde distribution in flames and engines. The measurement technique utilizes a laser/detection system which has been adopted for the generation of eight laser pulses at 355 nm. By combining these lasers with a framing camera, short movies showing the formaldehyde distributions in combustion phenomena can be recorded, by means of planar laser-induced fluorescence. The technique is successfully demonstrated in a laboratory flame as well as in an engine. In addition to the temporally resolved experiments also three-dimensional measurements are performed by sweeping the eight generated laser sheets across the flame by the use of a fast scanning mirror. By proper triggering of the laser sweep and the detector a three-dimensional image showing the formaldehyde distribution in the flame can be created, which is also demonstrated.