摘要:

This paper presents a survey of the factors governing the performance and operation of high temperature subsupersonic metal atom beam sources. After an initial statement of the requirements placed on such sources a section is presented which considers the factors determining atomic beam intensities and profiles. The section which considers the materials used in source construction discusses the choice of crucible material, and in so doing presents a table of the most suitable materials, hazard assessments, and other information for all those elements which can be vaporized. Two further parts of this section are devoted to resistive heater materials and ceramics. The review of the sources is divided between resistively heated sources, sources heated by electron bombardment, and inductively heated sources. Finally there is a section which briefly discusses the monitoring of source performance. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145337

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A general formalism is presented for the production, characterization, and use of uniform supersonic flows for the study of structural and collisional molecular properties. These flows make possible the generation of thermally equilibrated gaseous environments at temperatures generally extending from near 10 to above 300 K at pressures between 0.1 and 10 Torr. In addition, the invariance of flow conditions for distances of many nozzle diameters (5–30) beyond the exit makes the flows ideal for collisional or temporal studies. A concise outline for the design of the Laval nozzles necessary to produce specified density and temperature conditions is presented. Pulsed operation of these expansions is demonstrated, and a variety of useful characterization tools providing information on flow uniformity and thermal characteristics is considered. Recent applications of these flows for the study of low‐temperature chemical reactions are reviewed. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145338

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a description of the prototype interferometric gravitational wave detector at Glasgow. The detector, which has been under development for a number of years, consists of two perpendicular 10‐m‐long high finesse Fabry–Perot cavities formed between test masses hung as pendulums and is illuminated with a cw argon ion laser. The differential displacement sensitivity of the detector is ∼7×10−19 m/&sqrt;Hz from 500 Hz → 3 kHz and is close to being limited by photoelectron shot noise in the detected photocurrent. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145339

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the output power, slope efficiency and oscillation threshold of a diode‐pumped Tm:YAG microchip laser by using two different resonator configurations (half‐symmetric and near‐planar) for the development of an eye‐safe remote sensing laser system. The half‐symmetric resonator was superior in output power, slope efficiency and threshold, their values for a crystal temperature of 20 °C being 29 mW, 37%, and 28 mW, respectively. But the near‐planar resonator was superior in producing single mode oscillation, giving an output power of 2 mW at a crystal temperature of −10 °C. Between Tm:YAG and Tm,Ho:YAG microchip lasers, moreover, the latter was found to fall short in slope efficiency and threshold, indicating that the effects of Ho as a dopant on the output power is negative. Possible explanations for the difference are given. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145340

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The construction of a short external cavity (SXC) module based on the flexure mount concept for semiconductor lasers is presented. The SXC system is an inexpensive and simple means to achieve single‐mode operation from normally multimode lasers. The SXC assembly is a flexure mount designed to hold an external cavity mirror and a laser in alignment. The flexure mount permits easy and precise angular positioning of the external mirror. With InGaAsP lasers, side mode suppression ratio as high as 300 can easily be obtained. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145341

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A prototype setup for a low‐noise, high‐resolution, multi‐Gigahertz‐span optical heterodyne spectrum analyzer is presented. The frequencies of the unknown optical spectrum are converted to zero intermediate frequency by heterodyning with the output from a tunable single‐mode local oscillator laser in an optical mixer. The low‐frequency beats are rectified, and their strength is recorded while the spectrum is scanned by tuning the local oscillator. Low‐noise heterodyning requires double balance (or at least single balance) of the optical mixer. Further optimization of the noise performance can be achieved by adjusting the power levels of the light beams. Successful operation of the analyzer has been demonstrated by recording the output spectrum of a mode‐locked dye laser. ©1995 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1145342

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Optical instruments like autocollimator or interferometers have a limited aperture. Here we describe a simple device that effectively enlarges the viewing aperture, based on parallel shifting of the beam in a tilted parallel glass plate. This periscopic action is done with two additional degrees of freedom: variable radial displacement adjusted by the plate tilt angle and azimuthal movement controlled by plate rotation around an axis parallel to the optical axis of the device. For example, a 1.8 refractive index glass plate of 80 mm thickness can be tilted up to 60°, enlarging a 40 mm diameter aperture up to 130 mm effective aperture. A rotatable parallel glass plate periscope was constructed to explore the inside aperture of a ceramic tube, using a 1 mm diameter HeNe laser beam as a probe, obtaining 1 mm accuracy. To ease the plate rotation, the glass plate was chosen to have a trapezoid shape and a balancing weight was designed and constructed to evenly balance the plate weight through the operation range of the device. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145343

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We describe a high‐frequency modulation and detection system capable of measuring absorbance changes &Dgr;Aon the order of 10−6in optical pump‐probe experiments using submilliwatt laser powers from a mode‐locked ultrafast laser. For probe beam powers ≥9 &mgr;W, the system offers nearly shot‐noise‐limited performance. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145344

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A coolable gas cell for the measurement of mid‐infrared spectra of gases at cryogenic temperatures as low as 77 K is described. The design of the cell allows it to be operated in collisional cooling (or diffusive trapping) mode to generate significant nonequilibrium pressures of monomer vapor for gases which would normally have vanishingly small vapor pressure at low temperatures. Fourier transform infrared spectra of carbon dioxide (CO2), nitrogen dioxide (NO2), and methyl silane (CH3SiH3) vapors cooled by collisions with helium gas at 77 K are reported. Sufficiently high concentrations of monomer gas may be produced at low total pressure conditions (<10 h Pa) to allow spectra to be recorded at the Doppler resolution limit. The resulting spectroscopic simplification indicates that efficient collisional cooling of the vibrational, as well as rotational, degrees of freedom occurs. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145345

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Directly water‐cooled silicon crystals with various types of water channels and cooling fins were fabricated and tested at the 27‐pole wiggler beamline BL13 of the Photon Factory. Double‐crystal rocking curves for a Si(111) reflection indicated that the performance of a grooved silicon crystal in cooling efficiency is significantly improved by replacing conventional semicircular water channels and cooling fins with flat ones with optimum dimensions. For this design, the width of a Si(111) rocking curve was independent of a wiggler power within 2/3 of the full power. In this power range, a highly stable monochromatized beam with an energy resolution required in x‐ray absorption near‐edge structure experiments (&Dgr;E/E∼2×10−4) was obtained. ©1995 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1145346

出版商:AIP    

年代:1995

数据来源: AIP