摘要:

The design of a new ion spectrograph is described. Using magnetic deflection, analysis can be made of the velocity spectrum of the ions. For a given entrance angle to the magnetic field the foci lie on a straight line and second order focusing can be obtained. Application of an electric field parallel to the magnetic field causes displacement of the focal line to an extent determined by the charge‐to‐mass ratio of the ion. The image on the focal plane is thus a set of lines one for each ion species, the velocity distribution being displayed along each line.

ISSN:0034-6748    

DOI:10.1063/1.1684335

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A current profile monitor for the scanning electron beam from the accelerator is described. It utilizes the fact that the electrons scattered through large angles by the exit window of the scanner show a profile similar to that of the main beam at the irradiation site. The scattered electrons are collected by small probes arranged in a linear array parallel to the scanning direction, and the beam profile in this direction is displayed by a storage oscilloscope or an X‐Y recorder. This device has been used for electrons of energies 4–16 MeV from a linear accelerator and proved to be useful for continual monitoring with negligible disturbance to the irradiation in progress.

ISSN:0034-6748    

DOI:10.1063/1.1684336

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

To measure the fission cross section of233U as a function of neutron energy, instrumentation with fast pulse rise‐time and short resolving time characteristics is required. The efficient detection of fission‐fragment pulses in the presence of a high alpha background requires these characteristics. A fission detector with an electron collection time of 25 nsec and containing 1 g of233U, and an amplifier with a risetime of 7 nsec and an over‐all gain of 1000 were developed for this measurement. This system, detecting the fast rising current pulse from a parallel plate ionization chamber, is an integral part of the instrumentation used by a group at ORNL engaged in the measurement of the neutron fission and capture cross sections as a function of neutron energy. With this system, the fission cross section of233U was successfully measured over a neutron energy range from 0.4 to 2000 eV.

ISSN:0034-6748    

DOI:10.1063/1.1684337

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A self‐adjusting positioner has been developed for allowing a sensor to measure instantaneous flow properties at a fixed distance from a moving water surface. It thus permits measuring the flow field in the troughs of progressive wind waves, which is essential information for understanding air‐water interaction. With the aid of a special statistical technique to sample and average simultaneous recordings of water surface displacements and instantaneous flow properties, such as velocity, pressure, temperature, and humidity, a more complete description of both air and water flows near the interface can be obtained. The probe positioner works on the principle of the classical position servosystem. A capacitance gauge provides the actuating signal which is proportional to the depth of the water below the probe. The dynamic characteristics of the system, as expressed by its transfer function, indicate its applicability for wind waves generated both in laboratories and oceans.

ISSN:0034-6748    

DOI:10.1063/1.1684338

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A convenient method has been developed for producing thin foils of metals with relatively large transparent areas for transmission electron microscopy. A thin plate with the desired orientation is cut from a single crystal and an accurately oriented plane surface is produced on one side by successive chemical and electrolytic polishing. The specimen is mounted with this side in contact with a glass support and polished in the same way to give a plane parallel plate, about 0.01 mm in thickness. Rings with an external diameter of 3.2 mm and an internal diameter of 1.6 mm are next cemented to the plate. Disks are then cut out, detached, and thinned electrolytically by a micro‐window method to give a strip of uniform thickness across a diameter of the rim. The specimen can be transferred to the electron microscope holder without damage and large areas are available for examination.

ISSN:0034-6748    

DOI:10.1063/1.1684339

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

We describe a method for measuring the shape of a toroidal magnetic field (such as in a stellarator) to demonstrate the existence and nature of magnetic surfaces. We detect the successive circuits of a pulse of low energy, phase stabilized electrons injected parallel to the field and stored for many thousands of circuits. We find that the cumulative effect of various field perturbations alters the parameters of the surfaces significantly, but does not destroy them. In certain special cases, there is excellent agreement between the measured and computed field shapes for our specific device. These results and methods are of immediate application to a broad class of magnetic (or other area preserving) mappings. The same experimental technique can also be used for the long term storage of low energy ions.

ISSN:0034-6748    

DOI:10.1063/1.1684340

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

This study is concerned with the interpretation of the ionization gauge detector signal in a molecular beam experiment as a particular functional of the reflected molecule distribution function, called the nominal value of the detector signal. The detector configurations examined are those used to measure number density and time‐of‐flight velocity distributions. Expressions for the actual detector signals are established on the basis of the apparatus geometry; the nominal expressions are derived as approximations to the actual signal. Differences between these actual and nominal functionals are examined quantitatively using the Nocilla reflection model. It is found that in the density case the significant apparatus parameter is the solid angle subtended at the detector by the illuminated target area. If this solid angle is large, the error introduced by assuming the detector signal to be represented by the nominal expression becomes significant when the reflection is highly anisotropic. In the velocity distribution measurement, the significant factor is the shutter function. For slow shutter speeds, differences between the actual and nominal expressions for the detector signal increase rapidly as the error in the time the shutter is open increases.

ISSN:0034-6748    

DOI:10.1063/1.1684341

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

We have measured the mobility of ions in air. The method of measuring the mobility is a time‐of‐flight method. The time of flight of the ions is measured between two grids G1and G2, as in Bradbury's method. We have improved the resolution of the apparatus, using a rectangular cyclic voltage, and we have eliminated harmonic peaks. Results with radioactive ions of ThC″ and ions created in air by the &bgr; rays of a tritium source are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1684342

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A miniature centrifugal pump designed to circulate helium in a flow loop is described. It is designed to operate in the liquid helium temperature range under ambient pressures up to 100 atm (107N/m2), producing a maximum flow rate of 50 cm3/sec and a maximum pressure rise of 3400 N/m2. The operating characteristics obtained from preliminary tests with cold nitrogen gas and an analysis of the performance are included.

ISSN:0034-6748    

DOI:10.1063/1.1684343

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A substitution method for highly accurate determination of the static dielectric constant of solids is presented along with techniques for refining capacitance measurements. The results for some alkaline earth fluorides are CaF2, 6.799; SrF2, 6.466; and BaF2, 7.359; and an alkali halide KCl is 4.818.

ISSN:0034-6748    

DOI:10.1063/1.1684344

出版商:AIP    

年代:1970

数据来源: AIP