摘要:

A technique is described for the simultaneous measurement of the time‐of‐flight and energy of positive ions produced in the decay of excited molecules. The technique permits the separation and determination of the energy spectra of ion species with different mass to charge ratios. Data from the bombardment of CO by 1‐MeV He+are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134557

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Rare‐earth screens (Rarex types B and BG) were calibrated against Kodak No‐Screen x‐ray film using pulsed x radiation. Type B screen, which contains only an yttrium compound, is over 50 times more sensitive than No‐Screen film in the energy range above 17 keV and is the preferred screen, of the two tested, in the energy range below 50 keV. Type BG screen, which contains yttrium and gadolinium compounds, is 1.5 times less sensitive than type B below 50 keV (the Gd absorption edge) but 3.5 times more sensitive above 50 keV. All of the calibrations were accomplished with monochromatic x rays from secondary fluorescers. The results should be accurate for pulses of shorter duration than 1 msec, which is the decay time of the screens.

ISSN:0034-6748    

DOI:10.1063/1.1134558

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A lightweight balloon‐borne grab‐sampling system for determining mixing ratios <10−9of chlorocarbons and other minor constituents in the stratosphere is described. The all‐metal system consists of five sampling spheres and associated valves, which are opened and closed at selected altitudes by on‐board electronics during a parachute descent. The construction features, operating techniques, and experimental tests are given. In the latter, particular attention has been given to the problem of surface adsorption in ambient‐pressureinsitusampling of trace stratospheric constituents at these low mixing ratios.

ISSN:0034-6748    

DOI:10.1063/1.1134559

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

First we discuss a method of tuning NMR probe circuits and matching impedances which employs a variable length transmission line as one of the tuning elements. This method is useful for high voltage circuits where, due to space considerations, suitable tuning elements may not be placed adjacent to the rf field‐producing coil. Second, we describe the design of a single coil double resonance probe which uses &lgr;/4 transmission lines as filters as well as tuning elements. This double resonance probe is useful when the two frequencies of interest are widely separated.

ISSN:0034-6748    

DOI:10.1063/1.1134560

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An intense pulsed beam of energetic metal ions has been produced by electrically accelerating ions extracted from a laser‐produced plasma. A pulsed laser focused on a metal surface in a vacuum provides the expanding metal plasma. The plasma is intercepted by a pair of shaped grids located at a distance where the plasma cloud has become collisionless. An electric field between the grids accelerates and focuses the ions. Electrons from a heated filament are introduced into the ion stream in an effort to neutralize the space charge spreading of the ion beam (plasma). Ion beams were produced with energies from 1 to 10 keV. Ion fluences per pulse in the fast beam have reached 1013cm−2, and 1012ions per pulse have been injected through a cylindrical channel 0.8 cm diam×2.0 cm long. The beam pulse lengths were typically less than 20 &mgr;sec. Aluminum has been used principally but the method should be applicable to a wide range of materials.

ISSN:0034-6748    

DOI:10.1063/1.1134561

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An automatic viscometer and sampling system suitable for monitoring changes in the molecular weight of polymers in solution is described. Automation provides significant increases in precision and accuracy. The instrument can be used to follow degradation or polymerization reactions induced by radiation, heat, or chemical reaction. Examples are given of its application to the study of photolytic and chemical degradation of polymers.

ISSN:0034-6748    

DOI:10.1063/1.1134562

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A radio‐frequency receiver–amplifier for pulsed nuclear magnetic resonance applications is described. This amplifier has a voltage gain of 2000 and a bandwidth of 5–115 MHz and consists of three identical stages having nonsaturating overload characteristics. Each individual stage recovers within a time of 1 nsec following a 20 dBm overload. The blocking effect of capacitive interstage coupling following rf pulses has been essentially eliminated using series‐tuned broad bandwidth resonant circuits between stages. Measured receiver recovery times range from 250 nsec for short (400 nsec) transmitter pulses to 2.0 &mgr;sec for long (75 &mgr;sec) pulses. The effective receiver input noise voltage measured following phase‐sensitive detection and at the output of a video amplifier having a bandwidth of 320 kHz was 1.2 &mgr;V.

ISSN:0034-6748    

DOI:10.1063/1.1134563

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A system making use of matrix isolation techniques in the elucidation of the sputtering process has been developed and is described. A stable beam of positive ions produced with a commercially available sputter ion gun impinges on a target. The matrix‐isolated back‐sputtered products are collected on a cryogenically cooled optical plate for spectroscopic observation. The system can be used to identify atomic and molecular sputtered products and to measure sputtering yields. For demonstration purposes, the spectra of sputtered gold atoms in a deuterium matrix and sputtered molybdenum atoms in an argon matrix are shown.

ISSN:0034-6748    

DOI:10.1063/1.1134564

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An atomic beam spectrometer for the study of the interactions of neutral rare gas atoms with solid surfaces is described. These atoms, preferably neon atoms, have a very low kinetic energy, in the order of only a few meV, so that energy gains or energy losses by surface phonon processes can be detected. The change of the momentum of these particles is given by the preset scattering angle.

ISSN:0034-6748    

DOI:10.1063/1.1134565

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

This report describes a flexural analog of the torsion pendulum for measuring Young’s modulus and the internal friction Q factor on brittle materials. The design provides features to minimize fracture or chipping of the sample and reduces apparatus background damping so that a sample Q of ≳103can be reliably measured. Other features include strain amplitudes as low as 10−7, small size for use in an environmental chamber, and zero static stress.

ISSN:0034-6748    

DOI:10.1063/1.1134566

出版商:AIP    

年代:1976

数据来源: AIP