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Review of Scientific Instruments

Issue 1 • Date Jan 1966

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Displaying Results 1 - 25 of 41
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Measuring the Submicrosecond Response of Shock Loaded Materials

    Page(s): 1 - 7
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    Methods for high precision transient measurements using simple techniques for instrumentation and target alignment are described. Techniques are discussed in terms of application to a gas gun used to study the response of materials to dynamic loading. Results indicate that tilts of about 0.01° between impacting surfaces, projectile velocity measurements to about 0.1%, and time correlations to within 0.01 μsec are readily obtainable. View full abstract»

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  • Magnetic Field Measurement in an Electromagnetic Shock Tube Using Large Area Probes

    Page(s): 7 - 11
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    We examine the problem of measuring with a probe the magnetic field in a plasma which is moving with respect to the probe. It is shown that integration with respect to time is, in general, not proper and we develop correct expressions for the case of a current conducting plasma produced by a strong ionizing shock wave in an electromagnetically driven shock tube. Use of the correct expressions is described for large area magnetic field probes employed in a coaxial electromagnetic shock tube. The results demonstrate the need for careful interpretation of data obtained from magnetic field probes used to measure magnetic fields in moving media. View full abstract»

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  • Design and Adjustment of a 20 cm Mach‐Zehnder Interferometer

    Page(s): 12 - 15
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    The design of a large Mach‐Zehnder interferometer which uses fused silica flats in aluminum mounts and piezo‐electric crystals for remote fine adjustment is discussed. In addition, an expedient method of alignment is given which allows the adjustment to fringes and to the white light fringe condition to be more conveniently and quickly accomplished. View full abstract»

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  • Large Gas Filled Čerenkov Counter

    Page(s): 15 - 18
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    A large pressurized gas Čerenkov counter is described. The counter is designed to assist triggering on electrons in high energy counter‐spark chamber experiments. The requirement of large solid angle resulted in a counter of large dimensions and heavy construction. The results of tests made on the counter are presented. The tests indicate that the counter rejects pions very well and is roughly 50% efficient to electrons in the Λ° beta‐decay spectrum (0–200 MeV). View full abstract»

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  • High Speed Microwave Phase Shifters Using Varactor Diodes

    Page(s): 19 - 22
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    A reflection type microwave phase shifter is described which is similar to the units developed by Hardin, Downey, and Munushian. It employs the voltage‐variable capacitance of varactor diodes as the adjustable element. The ``pill type'' diodes tune their associated circuit through a resonance to produce phase shifts of over 90°. With proper adjustment of the tuning—a simple procedure—the output amplitude is made essentially constant. The use of two series diodes mounted back‐to‐back permits higher power operation, although the unit is essentially a low power device. View full abstract»

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  • Null Method of Measuring Microwave Phase Shifts

    Page(s): 23 - 28
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    A companion paper by Gardner and Hawke described a microwave phase shifter, with constant output, capable of rapid phase control by the bias voltage applied to varactor diodes. This paper describes the application of this device to measure phase shifts in a cw microwave system by a null method. If phase and amplitude variations are not too fast, standard oscilloscope components can provide most of the required circuitry. Examples are given, including the measurement of 0.003° phase shift at 9 Gc in a plasma experiment. View full abstract»

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  • Diamagnetic Levitation Using Pyrolytic Graphite

    Page(s): 29 - 35
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    Stable diamagnetic levitation of masses in excess of one gram has been accomplished in entirely passive systems using pyrolytic graphite and permanent magnets. Analytical and experimental data are given on two vertical thrust bearing assemblies. Extremely low frictional losses were determined from the rate of rotor deceleration in vacuum. Dissipation in a 4 cm diam rotor at 100 rpm was in the nanowatt range. Parametric studies are presented and possible applications discussed. View full abstract»

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  • General Monte Carlo Multivertex Event Generator

    Page(s): 36 - 43
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    A self‐contained easily expanded Monte Carlo program for the study of interactions in high energy physics is described. The program is capable of generating events and plotting results for a very wide class of reactions, including those governed by Lorentz invariant phase space and, also, those exhibiting resonances or other non‐trivial matrix elements. The performance of the basic program and the method of extending its scope are demonstrated in two examples showing the required input and resulting output. View full abstract»

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  • Instrumentation for Fermi Surface Measurements Using Ultrasonics

    Page(s): 44 - 51
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    Three methods are described for enhancing specific oscillatory components of the magnetic field dependent attenuation coefficient of sound found in pure metals at liquid He temperatures. These oscillations are related to Fermi surface properties. Instrumentation suitable for these methods is described in detail. Some data taken with these techniques are shown. In addition, a description of the ultrasonic technique used is included. View full abstract»

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  • Density Balance for Low Temperatures and Elevated Pressures

    Page(s): 51 - 54
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    An electromagnetic balance for the measurement of fluid density at low temperature and elevated pressure is described. The balance is operated by balancing the changes in gravitational forces due to the buoyancy of a sphere immersed in the fluid against the electromagnetic force between a current carrying coil and a permanent magnet. The apparatus, which requires a relatively small amount of fluid, is capable of high precision and can be operated at any temperature below ambient and at pressures up to 80 atm. View full abstract»

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  • Radiation Damage in Mylar Exposed to Minimum Ionizing Protons

    Page(s): 55 - 58
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    Mylar D strips have been exposed to 1016 protons in the circulating beam of the Cosmotron and the deterioration of their mechanical properties as a function of the dose is presented. The breaking strength has a threshold decrease at 1.0×1015 and falls to half value at 3.0×1015 protons/cm2. An estimate of the radiation dose has been made. View full abstract»

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  • Resistance Heated Crystal Puller for Operation at 2000°C

    Page(s): 59 - 61
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    A resistance heated crystal puller has been used to grow crystals of NbO, Ti2O3, and Al2O3, which have melting points of 1945, 2000, and 2050°C, respectively. The puller incorporates a modified version of a tantalum tube furnace described previously, which is capable of operating in oxidizing, neutral, and reducing atmospheres up to 2400°C. The seed holder is water‐cooled. View full abstract»

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  • Design of Slotted Disk Velocity Selectors

    Page(s): 61 - 64
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    Some design principles for slotted disk velocity selectors for molecular beams are set forth. Systematic methods are described for finding a set of disk spacings so that the minimum number of disks is required for sideband elimination. The resulting design permits operation of the velocity selector in several modes having different resolution and transmission properties. View full abstract»

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  • ARGUS—A Simple Device for Simultaneous Measurement of Breakdown Times of Many Spark Gaps

    Page(s): 65 - 68
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    A simple device, which enables one to observe on a single oscilloscope trace the individual breakdown times of many spark gaps in parallel, is described. It employs signals from magnetic probes placed near each spark gap. For illustration the signals of typical breakdown conditions are shown and briefly discussed on the basis of some qualitative remarks on the behavior of a fast discharge capacitor bank. View full abstract»

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  • Apparatus for NMR Studies at High Pressure

    Page(s): 68 - 72
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    An apparatus has been developed which permits NMR measurements at somewhat higher pressures than was previously possible. It makes use of supported taper pistons of chrome oxide with pyrophyllite or boron nitride as the supporting material. With a sample 2 mm thick, pressures of 40 kbar are obtainable; with a sample 0.9–1.0 mm thick, pressures as high as 80–90 kbar may be possible. Data of line width vs pressure are presented for Teflon and polyethylene, and the effect of pressure on the structure of these materials is briefly discussed. View full abstract»

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  • Apparatus for Measurement of Magnetic Anisotropy

    Page(s): 73 - 77
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    An apparatus is described for the measurement of magnetic anisotropies of single crystals by the maximum torque method. It has an accuracy of 0.5%. The apparatus features a rugged design and provision for working in a controlled atmosphere. Two methods of calibration are discussed and experimental procedures are described. The diamagnetic anisotropy (χ12) of naphthalene is reported to be 90.6±0.05×10-6 cgs units per mole. View full abstract»

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  • Machine for Uniaxial Tensile Straining in the X‐Ray Diffractometer

    Page(s): 77 - 79
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    The design and operation of a straining rig to achieve uniform tensile stress in specimens properly aligned within an x‐ray diffractometer with vertical axis are presented. Experimental results are shown which indicate the suitability of the instrument for determinations of x‐ray stress constants or studies of lattice strain by diffraction. View full abstract»

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  • Ionization Discrimination Properties of Spark Chambers

    Page(s): 80 - 82
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    Spark chamber behavior with respect to heavy and minimum ionizing particles is investigated in an attempt to find suitable gases and modes of operation that would permit ionization discrimination. Chambers having a gap of 10±0.05 mm and fillings of pure helium, pure argon, and helium‐argon mixtures were analyzed. It was found that for the given modes of operation only argon‐filled chambers show useful ionization discrimination properties, while chambers with pure helium fillings have practically none. The results obtained for helium‐argon mixtures are better than those for pure helium but inferior to those obtained for pure argon fillings. Curves showing the chamber responses with respect to 210Po alpha and minimum ionizing particles are presented for helium and for argon filled chambers. The effect of gas contamination is discussed and some data are given. View full abstract»

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  • Performance of a High Sensitivity Near Infrared Detection System

    Page(s): 83 - 86
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    The performance of a synchronous detection system using a cooled phototube (type S1 cathode) is described. Detailed measurements including those using an ultralinear semiconductor photosource indicate that the system responds linearly within 1% per decade of incident flux variation. A tunnel diode discriminator increases the signal‐to‐noise ratio by a factor of up to 5. The over‐all sensitivity obtained is ∼3×103 photons/sec or 5×10-16 W at 0.8 μ wavelength (phototube temperature -78°C). A field effect transistor amplifier with a relatively fast (390 cps) chopping rate is employed. In a spectrometer application in which the detection system is used in conjunction with a conventional monochromator (0.35 transmission, f/8 optics, and 0.005 μ/mm dispersion), a system sensitivity threshold of 4×10-12 W/cm2 μ sr is obtained at 0.8 μ wavelength. View full abstract»

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  • Continuous Measurement of Solid Propellant Burning Rates

    Page(s): 86 - 92
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    An experimental system is presented for the direct and continuous measurement of the burning rates of solid rocket propellants under conditions closely approximating those of a solid rocket motor. The system involves a positioning type servomechanism which moves a sample of solid propellant within a two dimensional rocket motor such that the receding burning surface of the sample is maintained at a fixed position with respect to the motor. Since the burning surface remains fixed, the direct measurement of the velocity of the propellant feed mechanism for adjusting the position of the propellant sample yields the burning rate. The servomechanism incorporated a 50 m Ci 137Cs source of gamma rays coupled with a scintillation probe for detecting the position of the burning propellant surface. The output of the probe was converted into a voltage by a ratemeter. It was then amplified and compared to a standard voltage which was proportional to a desired propellant surface position. The resulting difference was amplified for the purpose of driving a 0.6 hp servomotor which positioned the burning surface of the propellant sample. The size of the sample was approximately 2.5 cm square by 10 cm long. The experimental data were obtained with the above servomechanism for two composite propellant formulations. The data were obtained for a range of pressures from 8.8 to 35.5 kg/cm2, and for burning rates ranging from 0.40 to 0.8 cm/sec. The data correlated well with previously published data. A theoretical analysis of the servomechanism was performed to determine system stability and performance. An optimization analysis of the servomechanism system yielded optimum operating parameters. View full abstract»

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  • Application of Fourier Transform Spectroscopy to Magnetic Resonance

    Page(s): 93 - 102
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    The application of a new Fourier transform technique to magnetic resonance spectroscopy is explored. The method consists of applying a sequence of short rf pulses to the sample to be investigated and Fourier‐transforming the response of the system. The main advantages of this technique compared with the usual spectral sweep method are the much shorter time required to record a spectrum and the higher inherent sensitivity. It is shown theoretically and experimentally that it is possible to enhance the sensitivity of high resolution proton magnetic resonance spectroscopy in a restricted time up to a factor of ten or more. The time necessary to achieve the same sensitivity is a factor of 100 shorter than with conventional methods. The enhancement of the sensitivity is essentially given by the square root of the ratio of line width to total width of the spectrum. The method is of particular advantage for complicated high resolution spectra with much fine structure. View full abstract»

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  • Ultrasonic Treatment of Specimens in the Electron Microscope

    Page(s): 103 - 106
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    A method and technical details are described for direct observation of effects of high amplitude ultrasonic stress waves on dislocations in metal crystals. The technique combines, for the first time, ultrasonic treatment at high acoustic energy densities (up to 109 ergs/cm3 at frequencies between 30 and 100 kc), observation of damping of stress waves, and electron microscopy. Results from this in situ technique allow fundamental refinement of present theories on ultrasonic activation of dislocation mechanisms. View full abstract»

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  • Method for Studying Low Energy Ion‐Molecule Reactions Using Monoenergetic Ions

    Page(s): 107 - 110
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    An experimental technique is described for the study of ion‐molecule reactions permitting the investigation of ions with kinetic energies in the range 0–3 eV which introduces negligible spread in ion energy. A 20 nsec ionizing pulse is used to produce ions in the reaction chamber to which a steady dc electric field is applied. Because of the short time interval for ionization all ions have essentially the same energy and move as a ``bunch'' under the influence of the applied field. Thus the energy of the ions at any subsequent time may be readily calculated, and the energy dependence of ion‐molecular interactions may be studied. Practical considerations, determined by source dimensions, limited the maximum energy to 1.3 eV in the present study for the reaction CH4++CH4 → CH5++CH3. View full abstract»

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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Editor
Albert T. Macrander
Argonne National Laboratory