摘要:

The wedged‐pole concept is introduced as a means for enhancing the field strength and field quality of the rare‐earth permanent magnet hybrid undulator. The wedged‐pole configuration results in higher on‐axis field strength since it causes the magnet surface which faces the gap to be driven to the full magnet coercivity,Hc. Pole tip saturation is avoided by angular wedging of the poles and magnets to provide larger pole tip area without sacrificing magnet volume. The advantages of the wedged‐pole concept are investigated for an example case with a gap to wavelength ratio of 0.22 and SmCo5magnets. It is found that the field strength in the fundamental can be improved by as much as 15%. Alternatively, the field quality can be enhanced by operation of the poles far from saturation without loss of field strength. An additional benefit is reduction of the harmonic content in the field distribution.

ISSN:0034-6748    

DOI:10.1063/1.1139284

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The construction of a polarization spectrophotometer coupled with a microcomputer is described. The new spectrophotometer enables the continuous recording of a polarized emission spectrum of luminescent molecules as well as a polarized excitation spectrum. The instrument’s optics were designed to separately detect each polarized component of the emission utilizing an optical fiber bundle composed of two blanches. The use of the optical bundle, along with phase‐sensitive detectors, permits precise polarization measurements at low signal‐to‐noise ratios and, at the same time, affords a high degree of immunity from artifacts arising from the measurement of the polarized spectrum of emission. Data acquisition and various manipulations, such as instrument response and polarization calculations, were performed by a Fujitsu Micro 8 microcomputer equipped with an 8‐bit analog‐to‐digital converter. Several examples of the instrument’s performance are provided including a polarized phosphorescence emission spectrum of 0.05 mM indole in ethylene glycol–water (v/v=1) at 77 K.

ISSN:0034-6748    

DOI:10.1063/1.1139285

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The microprocessor of an 8‐bit PC system is used as a central control unit for the acquisition and evaluation of data from quasi‐elastic light scattering experiments. Data are sampled with a width of 8 bits under control of the CPU. This limits the minimum sample time to 20 &mgr;s. Shorter sample times would need a direct memory access channel. The 8‐bit CPU can address a 64‐kbyte RAM without additional paging. Up to 49 000 sample points can be measured without interruption. After storage, a correlation function or a power spectrum can be calculated from such a primary data set. Furthermore access is provided to the primary data for stability control, statistical tests, and for comparison of different evaluation methods for the same experiment. A detailed analysis of the signal (histogram) and of the effect of overflows is possible and shows that the number of pulses but not the number of overflows determines the error in the result. The correlation function can be computed with reasonable accuracy from data with a mean pulse rate greater than one, the power spectrum needs a three times higher pulse rate for convergence. The statistical accuracy of the results from 49 000 sample points is of the order of a few percent. Additional averages are necessary to improve their quality. The hardware extensions for the PC system are inexpensive. The main disadvantage of the present system is the high minimum sampling time of 20 &mgr;s and the fact that the correlogram or the power spectrum cannot be computed on‐line as it can be done with hardware correlators or spectrum analyzers. These shortcomings and the storage size restrictions can be removed with a faster 16/32‐bit CPU.

ISSN:0034-6748    

DOI:10.1063/1.1139286

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new method for the measurement of absorption coefficients of IR transparent materials is described. The method does not require thermal insulation and the measurement is made with the sample at room temperature. A heat pump removes the heat generated by absorption and keeps the sample temperature constant. The amount of heat removed is estimated from a calibration graph. The new method was used to measure the absorption coefficient of optical germanium.

ISSN:0034-6748    

DOI:10.1063/1.1139287

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report on an analyzer for elliptically polarized Lyman‐&agr; radiation (&lgr;=121.6 nm) which has a high transmission (14%) and can be used in ultrahigh vacuum. The analyzer consists of a pile of four MgF2plates and a MgF2quarter‐wave plate for Lyman‐&agr; light. We discuss examples for the application of this device by measurements of polarized Lyman‐&agr; light emitted after ion‐atom and ion‐surface collisions.

ISSN:0034-6748    

DOI:10.1063/1.1139288

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A setup for pulse radiolysis experiments is described consisting of the following main components: an array of 15 photomultipliers attached to a spectrograph (allowing 4032 spectra to be recorded with a time resolution of 500 ns per spectrum), self‐regulating high‐voltage supply for the photomultipliers, computer‐controlled solution mixing and dispensing system, and provisions for continuous dose variation of the FEBETRON‐accelerator electron beam. The general performance of the system is discussed and construction or electronic details are given for special components.

ISSN:0034-6748    

DOI:10.1063/1.1139289

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The design and construction of an axial flow gas transport system for a coaxial CO2laser discharge is described. The system features a novel annular flow geometry, which yields a compact, cylindrical package. Flow velocities of up to 50 m/s have been obtained in the device. Measurements of active medium working temperature and gain profiles are also presented.

ISSN:0034-6748    

DOI:10.1063/1.1139290

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A laboratory x‐ray spectrometer designed for routine analysis in the 15–60‐keV spectral range is described. It consists of a 40‐cm bent‐crystal transmission spectrometer in the Cauchois geometry, controlled by a microcomputer. The choice of the crystal analyzer and of the detection system is discussed. The instrument is well suited for large spectral range x‐ray absorption and emission spectroscopy (XAS, XES) and x‐ray source diagnostics.

ISSN:0034-6748    

DOI:10.1063/1.1139291

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

AK‐band receiver using cooled high‐electron mobility‐transistor (HEMT) amplifiers was developed at the Nobeyama Radio Observatory (NRO). Remarkable reduction of receiver noise temperatureTrecwas obtained when it was cooled down to cryogenic temperature. The lowestTrecof 75 K was obtained at 23.4 GHz. This low noise characteristic reveals that the cooled HEMT amplifier is promising as a sensitive receiver for radio astronomical observations.

ISSN:0034-6748    

DOI:10.1063/1.1139292

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An ion beam apparatus for the absolute measurement of collision cross sections in singly and multiply charged ions is described. An inclined electron and ion beams arrangement is used. Emitted photons from the decay of collision produced excited states are collected by a mirror and imaged onto a photomultiplier. Absolute measurements of the electron impact excitation of the 2s–2ptransition in C3+were used to demonstrate the reliability of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1139293

出版商:AIP    

年代:1987

数据来源: AIP