摘要:

We have designed, calibrated, and deployed an electron spectrograph to measure the effect of the free‐electron laser interaction on the relativistic electron beam in an FEL. The spectrograph spans a wide energy range (&Dgr;E/E∼1) and is designed for electron energies from 2 to 4 MeV. Calibration was achieved using a 2–6‐keV proton beam, and the measured dispersion is in good agreement with the value predicted from ray tracing. The spectrograph has been used to estimate the extraction efficiency, and the results agree within 25% with the observed microwave power levels.

ISSN:0034-6748    

DOI:10.1063/1.1139590

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A block slit collimation system of the Kratky design concept has been modified and adapted for synchrotron radiation. The building block small‐angle x‐ray diffractometer (SAXD) not only retains the essential advantages of the Kratky camera, i.e., accessibility at small values ofq[=(4&pgr;/&lgr;)sin(&thgr;/2) with &lgr; and &thgr; being the x‐ray wavelength and the scattering angle, respectively] and ease of alignment, but also provides portability and low construction cost. With our SAXD operating at the SUNY X21A beamline of the National Synchrotron Light Source, we were able to reach &thgr;∼1 mrad corresponding toq∼0.04 nm−1(or a Bragg spacing of 150 nm) using an incident slit width (d) of 0.5 mm and &lgr;=0.15 nm. Atd=0.5 mm, ∼10% of the monochromatic synchrotron x‐ray radiation passed through the block collimation system and a parasitic intensity to main beam intensity ratio of ∼10−5at &thgr;=1 mrad was achieved. Withd∼0.1 mm, it is anticipated thatq∼0.01 nm−1can be accessible. By changing the vacuum tube length between the sample chamber and the beam stop from ∼1400 to ∼200 mm, we could reach an intermediateqrange of ∼0.04≲q≲10 nm−1using a 5‐cm‐long linear position‐sensitive detector with a resolution of ∼100 &mgr;m/channel. A description of the SAXD and its operation is presented.

ISSN:0034-6748    

DOI:10.1063/1.1139591

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An electron‐optical system and hemispherical electrostatic energy dispersing element for quantitative electron spectroscopy over a wide range of kinetic energies is described. The electron optics were modeled using several calculational techniques, in order to determine the theoretical conditions under which a fixed linear magnification could be obtained. By designing an optical system with a plane of reflection symmetry, fixed magnification focus was possible over a calculated range of retard ratios from 1/40 to 40/1. The optics can be run in two different modes, one with and one without a retarding field grid to achieve the energy retardation. Comparisons between the predictions made using the various computational methods are reported, as well as experimental verification of the actual performance of the electron optics and energy analyzer. A method is described by which the angular acceptance of the electron optics can be varied by changing the excitation potentials on the lenses. The completed system allows for the simple installation of single‐channel, multichannel, and spin‐polarization detectors without modification of the analyzer.

ISSN:0034-6748    

DOI:10.1063/1.1139592

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A crystal mount has been developed which permits adjustment of the radius of curvature of the diffracting crystal in a curved crystal spectrometer without changing the crystal’s orientation with respect to the instrument. This mount simplifies x‐ray spectrometer design permitting a fixed crystal‐to‐detector distance. The scale of the instrument is readily changed by changing only this parameter.

ISSN:0034-6748    

DOI:10.1063/1.1139593

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The study of phase decomposition and crystallization of amorphous alloys by small‐angle x‐ray scattering requiresinsitumeasurements during heating to avoid statistical errors due to variation in sample thickness and irradiated volume. The early stages of structural changes and phase transformations are best followed by dynamic measurements using high‐intensity x‐rays as obtained from synchrotron radiation. In this paper we present a new heating apparatus designed and constructed for dynamic small‐angle x‐ray scattering measurements on amorphous alloys during heating. Measurements are conducted on wide ribbons of amorphous alloys self‐heated by joule heating. The arrangement is particularly appropriate for such measurements due to the very high electrical resistivity of such amorphous tapes.

ISSN:0034-6748    

DOI:10.1063/1.1139594

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We describe a scanning Michelson interferometer and utilization of fast Fourier transformation in laser wavelength determination. The Fourier transformation method is demonstrated to be particularly powerful in cw multimode (diode) laser investigations and in cw single‐mode laser long‐term frequency stability measurements. An uncertainty less than 10−7can be concluded from comparisons of a two‐mode polarization stabilized 543‐nm He–Ne laser with an iodine stabilized 633‐nm He–Ne laser.

ISSN:0034-6748    

DOI:10.1063/1.1139435

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An externally heated copper vapor laser using a carbon tubular heater is described. A recrystallized alumina tube of 20‐mm inner diameter is used as the laser tube, which is located inside the tubular heater. When the heating power of the carbon heater is 3 kW, the temperature of the laser tube is 1600 °C. The average laser output power is measured to be 1.2 W at a laser tube temperature of 1500 °C when the charging voltage to the energy storage capacitor is 5 kV, the pulse repetition rate is 5 kHz, and the Ne gas fill pressure is 10 Torr.

ISSN:0034-6748    

DOI:10.1063/1.1139436

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A simple design for a stable, general‐purpose optics mount is described, with independent, self‐locking angular adjustments about two orthogonal axes. Requiring only simple machining and readily available parts, the design allows unrestricted access for incident and transmitted beams.

ISSN:0034-6748    

DOI:10.1063/1.1139437

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Three similar but geometrically distinct electrode designs for an electrodynamic balance or quadrupole particle levitation cell have been compared in terms of the minimum periodic motion, or ‘‘null point’’ motion of single, suspended glass spheres of either 30 or 11 &mgr;m in diameter. The three electrode surface designs included the ideal hyperbolic shape, similar but spherical surfaces, and spherical surfaces in which the center ring electrode was split. The motion of the glass spheres was determined by forming an interferometer from scattered laser light and a reference beam using a single frequency He–Ne laser. A heterodyne signal was generated by shifting the frequency of the reference beam an arbitrary but known amount. No significant distinctions in terms of small amplitude motion were observed among the different cell designs. All three cells were able to suspend and stabilize a 30‐&mgr;m sphere to an rms amplitude of motion of less than 0.14 &mgr;m. For each of these designs, dependence of the particle motion on the dc balancing voltage was measured, and the effect of other operating parameters determined. Also, previously unreported sensitivity with regard to the vertical tilt of the cell axis was observed.

ISSN:0034-6748    

DOI:10.1063/1.1139438

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An eight‐shot pneumatic pellet injection system has been developed for plasma fueling of the tokamak fusion test reactor (TFTR). The active cryogenic mechanisms consist of a solid hydrogen extruder and a rotating pellet wheel that are cooled by flowing liquid‐helium refrigerant. The extruder provides solid hydrogen for stepwise loading of eight holes located circumferentially around the pellet wheel. This design allows for three different pellet diameters: 3.0 mm (three pellets), 3.5 mm (three pellets), and 4.0 mm (two pellets) in the present configuration. Each of the eight pellets can be shot independently. Deuterium pellets are accelerated in 1.0‐m‐long gun barrels with compressed hydrogen gas (at pressures from 70 to 105 bar) to velocities in the range 1.0–1.5 km/s. The pellets are transported to the plasma in an injection line that incorporates two stages of guide tubes with intermediate vacuum pumping stations. A remote, stand‐alone control and data‐acquisition system is used for injector and vacuum system operation. The eight‐shot injection system has been installed and operated on TFTR. The design features, operation, and performance characteristics of the system are described.

ISSN:0034-6748    

DOI:10.1063/1.1139439

出版商:AIP    

年代:1987

数据来源: AIP