摘要:

Spin angular momentum conservation in chemiionization reactions involving optically oriented He(23S) atoms in a flowing helium afterglow has been exploited to yield a source of spin‐polarized electrons. Either transversely or longitudinally polarized electrons can be extracted. Polarized electron beam currents of ∼2 &mgr;A have been realized at 40% polarization. The beam has an effective emittance of ∼2 mrad/cm over the energy range 100–400 eV, an energy spread of ≲0.15 eV, and the polarization is readily reversible. The source is relatively inexpensive and appears suitable for the majority of low‐energy spin‐dependent scattering experiments proposed to date.

ISSN:0034-6748    

DOI:10.1063/1.1135659

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A novel Mott polarization analysis system is described. This system is much simpler than earlier designs and offers improved rejection of electrons inelastically scattered from the gold target foil. In addition the analyzer is capable of ’’in‐line’’ polarization measurements.

ISSN:0034-6748    

DOI:10.1063/1.1135670

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A Q‐controlled Nd:glass ring laser system has been developed which is actively mode‐locked by means of either KD*P or LiNbO3electro‐optic modulators and is capable of producing 1.5 mJ, 100 ps, 1.06 &mgr;m pulses synchronized to better than 400 ps to an external event. By using prelase methods or saturable absorbers shorter pulses from 37 to 15 ps duration can be generated with poorer synchronization.

ISSN:0034-6748    

DOI:10.1063/1.1135644

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An inexpensive, expandable, continuously pumped, all‐metal flash x‐ray tube (FXT) was developed. It was coaxialy integrated at the end of a 70‐&OHgr; flexible coaxial transmission line. The tube, which has a small, 0.5‐mm, x‐ray source size when operated at 200 kV, produces a dose rate of 5×107R/s (at exit port). The produced x‐ray pulse has a duration of 20 ns, thus permitting the radiography of high‐speed transient phenomena.

ISSN:0034-6748    

DOI:10.1063/1.1135658

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The absorption of infrared energy is used to infer internal interfacial displacements. The probe consists of an infrared emitting diode, operated in a pulsed mode, which projects a collimated beam of radiation across a fluid interface onto a silicon photodiode detector. The output of the diode feeds an amplifier and a sample‐and‐hold circuit. Through multiplexing, the electronics are capable of handling up to eight probes. The infrared sensor has a sensitivity of about 1 V/cm, and it may easily be used to resolve wave motions as small as 0.01 mm.

ISSN:0034-6748    

DOI:10.1063/1.1135660

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The temperature inhomogeneity in the glass mixing chamber of a3He/4He dilution refrigerator has been studied. The inhomogeneity is reduced to 10 mK by inserting a cylindrical spacer in the mixing chamber.

ISSN:0034-6748    

DOI:10.1063/1.1135661

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A method for the magnification of x‐ray radiographic images is described and demonstrated. This magnifier employs two successive asymmetric diffractions of an x‐ray beam from highly perfect silicon crystals. The two diffractions magnify the beam in two perpendicular directions. A device with a magnification of 25× is demonstrated for CuK&agr;radiation. This device preserves and sometimes improves the resolution inherent in the radiographic technique. The x‐ray magnifier is particularly useful in circumventing the relatively poor spatial resolution of electro‐optical imaging systems needed for real‐time observations. Basic limits on magnification and resolution using this method are described.

ISSN:0034-6748    

DOI:10.1063/1.1135662

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 &mgr;m from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane–electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.

ISSN:0034-6748    

DOI:10.1063/1.1135663

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This publication describes a constituent analyzer which uses a concave holographic grating for high‐energy throughput, a conjugate cam drive to allow up to ten spectral scans per second, a microprocessor for data gathering and system control, and a minicomputer for the complex statistical computations required in the interpretation of the spectral data gathered. The instrument was specifically developed for quantitative measurement of food constituents in food processing and quality control. However, as a general state‐of‐the‐art spectrophotometer it was found to be a valuable tool in other disciplines such as industrial, clinical, and medical applications.

ISSN:0034-6748    

DOI:10.1063/1.1135664

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new method of plotting the impurity profile is described. It makes efficient use of the advantage of an operational amplifier and the nonlinearity of the junction capacitance in a semiconductor. When two small ac signals are applied to the inverting input terminal of the operational amplifier, intermodulation arises due to the nonlinearity of the junction capacitance inserted in the feedback loop, at the time the reverse bias voltage to the junction can be supplied from the noninverting input terminal; then the signals concerning both the depletion layer widthxand the impurity concentrationN(x) arise at the output terminal of the operational amplifier. By detecting each of the amplified input signals and the difference‐frequency ones corresponding toxandN(x), respectively, the relation ofx−N(x) can be plotted easily, at the same time, in a short time, and at a low cost.

ISSN:0034-6748    

DOI:10.1063/1.1135665

出版商:AIP    

年代:1979

数据来源: AIP