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1 Jan 1965

Volume 36, Issue 1, pp. 1-336

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Appointment of New Editors

Hugh C. Wolfe

J. Appl. Phys. 36, 1 (1965); http://dx.doi.org/10.1063/1.1713875 (2 pages) | Cited 4 times

Online Publication Date: 14 July 2004

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Abstract Unavailable

Long‐Transient Effects in Lasers with Inserted Liquid Samples

J. P. Gordon, R. C. C. Leite, R. S. Moore, S. P. S. Porto, and J. R. Whinnery

J. Appl. Phys. 36, 3 (1965); http://dx.doi.org/10.1063/1.1713919 (6 pages) | Cited 290 times

Online Publication Date: 14 July 2004

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Buildup and decay transients were observed when polar or nonpolar liquid cells were placed within the resonator of a helium—neon laser operating in the red at 6328 Å. Similar but smaller effects were also observed with two solids. Time constants were the order of a few seconds for all materials, which suggests a thermal phenomenon, but general heating effects were ruled out by the strong localization of the phenomenon. Transverse motion of the cell by about one beam width caused new transients similar to the initial ones.
It is believed that the effects are caused by absorption of the red light in the material, producing a local heating in the vicinity of the beam and a lens effect arising from the transverse gradient of refractive index. Absorptions of 10−3 to 10−4 parts per centimeter are sufficient to produce the effects, and are believed to be reasonable values for the materials studied. One of the most important applications may in fact be for the measurement of small absorbancies.
The experiments are described, and analysis of the lens effect from absorption is given. Alternate explanations which were considered are stated briefly.

Noise Transformation and Cyclotron Waves in Crossed Fields

J. E. Rowe and R. P. Wadhwa

J. Appl. Phys. 36, 9 (1965); http://dx.doi.org/10.1063/1.1713930 (6 pages) | Cited 3 times

Online Publication Date: 14 July 2004

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A transmission‐line analog is developed for crossed‐field space‐charge flows from the simultaneous solution of Maxwell's equations, the Lorentz force equation, and the continuity equation. A thin one‐dimensional injected beam is assumed. The resulting fifth‐degree secular equation is solved for several values of ωc∕ωp. The five system waves consist of a pair of hybrid waves, a pair of near‐cyclotron waves and a near‐synchronous wave. The results indicate that noise transformers may be based on an equivalent piecewise uniform transmission line.

Effect of Cesium Vapor on the Emission Characteristics of Uranium Carbide at Elevated Pressures

Philip W. Kidd

J. Appl. Phys. 36, 14 (1965); http://dx.doi.org/10.1063/1.1713862 (4 pages) | Cited 4 times

Online Publication Date: 14 July 2004

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The saturated emission currents from uranium carbide in cesium vapor were measured for four different bath temperatures T: 167°, 197°, 227°, and 250°C (the cesium arival rates μa, in 1019 atoms∕cm2, were 0.3, 1, 3, and 6, respectively). The measurements were made with a ``plasma anode'' tube at constant temperature. The plot of logμa vs 1000∕T was used to extrapolate the electron emission ``S'' curves to arrival rates that differed by a factor of ten. Since calculations based on the assumption of a homogeneous surface yields unexpectedly high binding energies and surface coverages, it seems likely that some surface patchiness exists.

Radio‐Frequency Breakdown in a dc Parabolic Potential Field

Thomas W. Karras and Erick Lindman

J. Appl. Phys. 36, 18 (1965); http://dx.doi.org/10.1063/1.1713872 (5 pages) | Cited 1 time

Online Publication Date: 14 July 2004

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Electrons that are confined in a Penning discharge geometry by electric and magnetic fields are observed to gain energy from a superimposed rf field. By shaping the electrodes in the form of hyperboloids of revolution the prebreakdown motion can be accurately described by the Mathieu equation. Resonances are predicted when the frequency of the electron in the electrostatic well is a multiple of half the rf frequency. In the pressure range investigated (air at 10−2 to 10−5 Torr), values as low as 40‐V dc and 3‐V rf were observed at the first resonance under conditions where the Penning mechanism alone required over 400‐V dc. Between resonances the Mathieu equation predicts runaway energy gain at considerably higher values of the rf voltage, but breakdown is observed at values much lower than the prediction. The explanation is found in energy gain through collisions with gas atoms. The collision resets the phase of the motion and allows the electron to continually gain energy from the rf field. Breakdown curves are calculated for the regions between resonances and are found to agree with experiment.

Light Modulation Experiments at 16 Gc∕sec

R. A. Myers and P. S. Pershan

J. Appl. Phys. 36, 22 (1965); http://dx.doi.org/10.1063/1.1713882 (7 pages) | Cited 3 times

Online Publication Date: 14 July 2004

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An experimental study of light modulation at 16 Gc∕sec, using the linear electro‐optic (Pockels) effect, has been performed. The principal result has been the demonstration of a new type of traveling‐wave‐like light modulator, which takes advantage of the fact that in crystals which have a 4 axis (such as KDP— potassium dihydrogen phosphate) an electric field parallel to this axis is equivalent to a field in the opposite direction if the crystal is rotated 90° about the axis. The modulator is made of a stack of crystals alternately rotated 90° with respect to one another and of a height such that the electric field changes phase by 180° in the time light takes to pass through one crystal. In this way, the electrically induced birefringence increases with optical path even though the microwave modulating field is a standing wave with no spatial variation in the direction of light propagation. For the experiments to be described, the microwave field is obtained with a multimode solid dielectric cavity efficiently driven in its TE101 mode. Results on simple devices containing two and three crystals are reported, and a discussion of the general properties of this type of device is presented. In addition, the magnitude of the electro‐optic effect in KDP and ADP (ammonium dihydrogen phosphate) has been found to be the same at 16 Gc∕sec, within experimental errors of 25% in ADP and 12% in KDP, as the low‐frequency clamped effect in these materials, in agreement with previous observations at 9 Gc∕sec. Results concerning the variation with optical wavelength of the electro‐optic effect in these materials at 16 Gc∕sec are also reported.

Performance of the He☒Ne Gas Laser as an Interferometer for Measuring Plasma Density

D. E. T. F. Ashby, D. F. Jephcott, A. Malein, and F. A. Raynor

J. Appl. Phys. 36, 29 (1965); http://dx.doi.org/10.1063/1.1713893 (6 pages) | Cited 54 times

Online Publication Date: 14 July 2004

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The characteristics of the He☒Ne gas laser used in a new simple interferometric technique have been studied experimentally and theoretically. The interferometer has two novel features: first, the intensity of the laser itself is used to detect the fringes and second, because the intensities of the 0.63‐μ (red) and 3.39‐μ (infrared) laser beams are coupled, interference in the infrared can be detected by a simple photomultiplier monitoring the red beam.
The system does not respond instantaneously to changes in the optical path length; experimental measurements show that when the red beam is used to follow interference in the infrared, the maximum detectable response is limited to about 3×106 fringes per second. Discussion of the frequency response and the cross‐coupling between the two wavelengths leads to the conclusion that the frequency response is limited by the red channel only.
Experimental details of the interferometer are described, including the application of a multipass system which, with some loss in spatial resolution, increases the sensitivity of the interferometer by at least a factor of 20.

Excitation of Hypersonic Vibrations by Means of Photoelastic Coupling of High‐Intensity Light Waves to Elastic Waves

Norman M. Kroll

J. Appl. Phys. 36, 34 (1965); http://dx.doi.org/10.1063/1.1713918 (10 pages) | Cited 171 times

Online Publication Date: 14 July 2004

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A theory of the excitation of elastic waves arising from photoelastic coupling with light is presented. It is similar in character to the theory of optical parametric amplification in spatially extended media. Special attention is given to the self‐excited transient case. A novel form for the space—time development of the instability appears for the case in which the spatial dimensions of the interaction region are large compared to the distance traveled by an elastic wave during the illumination time. The predicted effects should be readily observable with existing giant pulse lasers.

Potential‐Well Description of Electromagnetic Levitation

Albert J. Hatch

J. Appl. Phys. 36, 44 (1965); http://dx.doi.org/10.1063/1.1713920 (9 pages) | Cited 3 times

Online Publication Date: 14 July 2004

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Levitational forces exerted by spatially nonuniform ac magnetic fields on nonmagnetic conducting spheres are derived as the negative gradient of a potential function. Surfaces representing this potential for a small rigid diamagnetic sphere are used to visualize the levitational properties of several typical fields established by circular coils. Topological characteristics of these surfaces indicate that dipole fields have very shallow potential wells only for vertical and near‐vertical positions of the coil axis, and are only marginally levitational. Helmholtz and mirror fields have similar shallow potential wells. Quadrupole fields, however, have deeper potential wells in the vicinity of the central nodal point for all positions of the coil axis, and are strongly levitational. Higher‐order multipole fields can have potential wells similar to those in quadrupole fields. The description is also applicable to the levitation of nonmagnetic superconducting bodies in nonuniform ac magnetic fields.

Stability of Arcs in Gases

George A. Farrall and James D. Cobine

J. Appl. Phys. 36, 53 (1965); http://dx.doi.org/10.1063/1.1713921 (4 pages) | Cited 6 times

Online Publication Date: 14 July 2004

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A study has been made to determine the average duration of dc arcs in various gases at slightly higher than atmospheric pressure. These arcs were drawn between ¾‐in. copper contacts with power being supplied from a 125‐V dc generator. The experimental vessel, which contained about 1 liter volume, was provided with two liquid‐nitrogen traps through which gas was admitted and withdrawn. The gases studied were hydrogen, helium, argon, nitrogen, oxygen, and sulfur hexafluoride. It was found that in the current range studied (about 1 to 45 A) arc duration was always statistical and finite. This behavior is similar to that observed earlier for metal vapor (vacuum) arcs. For a given current, average arc duration increased for those gases in the order listed above. In the case of the latter two (O2, SF6), arc stability is believed to have been strongly affected by arc reaction products. It was concluded that for each of the gases studied, arc duration was greater than that found for a copper vapor arc at the same current, using the same generator source. It is believed that the gases blanket the cathode surface during the arc and reduce the loss of metal vapor from cathode emission sites below that occurring in the vacuum arc. There has been strong evidence in earlier work that abundant metal vapor at the arc cathode enhances arc stability.

Electron Removal During the Early Oxygen Afterglow

Michael H. Mentzoni

J. Appl. Phys. 36, 57 (1965); http://dx.doi.org/10.1063/1.1713922 (5 pages) | Cited 11 times

Online Publication Date: 14 July 2004

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Microwave diagnosis showed that the early afterglow of an oxygen plasma was controlled by ambipolar diffusion and by recombination (αr), depending upon pressure (from 0.15–4.0 mm Hg), at elevated gas temperatures (up to 900°K). At Tgas=300°K attachment also seemed to be important for higher pressures (p>0.65 mm Hg). For low plasma excitation energy the measurements yielded αr=2.1×10−7 cm3 sec−1 at Tgas=300°K, dropping gradually to 1.4×10−7 cm3 sec−1 at 894°K. The plasma excitation energy had a marked effect on the apparent recombination and attachment rates which tend to indicate that vibrationally excited ions and molecules do affect these rates as has been suggested previously.

Experimental Separation of Collective and Individual Phenomena in Plasmas‐Anomalous Resistance

K. I. Thomassen

J. Appl. Phys. 36, 62 (1965); http://dx.doi.org/10.1063/1.1713923 (4 pages) | Cited 1 time

Online Publication Date: 14 July 2004

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An experimental method for separating collective effects from collision dominated phenomena in plasmas consists of probing the plasma at a frequency between the collision and plasma frequencies that govern the rates of the individual and collective processes. This method is applied to the measurement of anomalous resistance by utilizing a re‐entrant cavity to expose a quiescent plasma to the strong electric fields at this intermediate frequency, thus provoking anomalous resistance. The resistive loading of the cavity is then observed as a function of power level or field strength, giving evidence of an anomalous resistance above power levels which initiate the two‐stream instability.

Self‐Consistent Field Analysis of Multireflector Optical Resonators

Peter O. Clark

J. Appl. Phys. 36, 66 (1965); http://dx.doi.org/10.1063/1.1713924 (7 pages) | Cited 2 times

Online Publication Date: 14 July 2004

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The self‐consistent field approach is used to obtain integral equations for the modes in symmetric and nonsymmetric resonators with arbitrary numbers of mirrors. The resonator fields are considered as TEM clockwise and counterclockwise traveling waves which for passive resonators are uncoupled and which independently satisfy the necessary boundary conditions on reflection from the resonator mirrors. An arbitrarily polarized field is resolved into two linearly polarized components which can be treated separately and identically. The component perpendicular to the plane of the resonator is considered and integral equations are obtained for the spatial distribution of resonator modes just after reflection from any mirror in both the symmetric and nonsymmetric resonators. The integral equation for the symmetric N‐mirror resonator is investigated in detail. Because of the astigmatic focusing of the reflectors there is no situation corresponding to the confocal resonator, however, a ``pseudoconfocal'' resonator with nonspherical mirrors is discussed. The integral equation for the resonator with arbitrary mirror spacing is solved in the limit of infinite Fresnel numbers and the resonator field is described in terms of Hermite‐Gaussian functions. The mirror spacing must satisfy the condition 0≤l∕bcosα≤2. A general resonance condition is obtained and the results of numerical computations of diffraction losses are presented for three‐ and four‐mirror resonators. For minimum diffraction loss the ratio of mirror spacing to mirror curvature is not constant but varies from mode to mode and the amount of variation differs with the number of mirrors.

Giant Pulses from a Laser: Optimum Conditions

M. Menat

J. Appl. Phys. 36, 73 (1965); http://dx.doi.org/10.1063/1.1713925 (4 pages) | Cited 4 times

Online Publication Date: 14 July 2004

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The conditions for maximized peak power extraction from a giant pulse laser are examined. In order to formulate an appropriate mathematical framework relating the various significant magnitudes, some simplifying assumptions and approximations have been used. The critical coupling conditions and the value of the resulting optimum peak power as a function of a characteristic loss factor have been determined. A distinction is made between maximum peak power and maximum energetic yield since the conditions for the achievement of both are slightly different.

High‐Temperature Specific Heats of Ge, Si, and Ge‐Si Alloys

D. Gerlich, B. Abeles, and R. E. Miller

J. Appl. Phys. 36, 76 (1965); http://dx.doi.org/10.1063/1.1713926 (4 pages) | Cited 25 times

Online Publication Date: 14 July 2004

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The specific heats of Ge, Si, and Ge‐Si alloys were determined in the temperature range 300° to 1000°K, by a novel temperature‐modulation technique. The specific heat at constant pressure cp exceeds appreciably the Dulong‐Petit value cDP at high temperature. Above the Debye temperature θD the divergence can be represented by cp/cDP = 0.95+αT/θD where T is the absolute temperature and α=0.081 is a coefficient independent of alloy composition. This result is in disagreement with the current theory of the anharmonic contribution to the specific heat at high temperatures, which predicts α=0.016 for Ge, and α=0.030 for Si.

Magnetic Hysteresis in Superconducting Thin Films

Hollis L. Caswell

J. Appl. Phys. 36, 80 (1965); http://dx.doi.org/10.1063/1.1713927 (5 pages) | Cited 5 times

Online Publication Date: 14 July 2004

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Tin films were deposited from the vapor at various substrate temperatures and their superconducting properties determined as a function of film structure. Magnetic hysteresis in the superconducting state to normal state phase transition of these films increased with increasing grain size. Hysteresis could be attributed solely to supercooling only in the smaller‐grained films deposited at low substrate temperatures. For the larger‐grained films, superheating was also observed. The hysteresis observed experimentally was in agreement with the predictions of the Ginzburg‐Landau theory of superconductivity.

Effect of Cesium Fluoride on a Cesium Vapor Diode

C. H. Skeen

J. Appl. Phys. 36, 84 (1965); http://dx.doi.org/10.1063/1.1713928 (5 pages) | Cited 1 time

Online Publication Date: 14 July 2004

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A cesium vapor diode was operated both before and after cesium fluoride was introduced into the interelectrode space. The electrodes were plane parallel, had a cross‐sectional area of 2 cm2, and were made of molybdenum having a polycrystalline surface. The interelectrode spacing was varied from 0.01 to 10 mm. The cesium fluoride vapor additive caused an increase in the optimized output power density. For a given emitter temperature this enhancement increased with spacing until the spacing reached about 0.89 mm, after which it became uniform. The enhancement decreased with an increase in emitter temperature. The increase averaged about 20% for a combination of these cases. When all parameters were held constant except the cesium fluoride reservoir temperature, an increase in the additive vapor pressure caused the enhancement to decrease. The optimum collector temperatures decreased up to 2% after the cesium fluoride addition. The optimum cesium vapor pressures were decreased by about 15°K after the CsF addition.

Magnetic and Crystallographic Studies of Substituted Gadolinium Iron Garnets

S. Geller, H. J. Williams, R. C. Sherwood, and G. P. Espinosa

J. Appl. Phys. 36, 88 (1965); http://dx.doi.org/10.1063/1.1713929 (13 pages) | Cited 22 times

Online Publication Date: 14 July 2004

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Magnetic data from measurements at moderate to high magnetic fields in the temperature range 1.4° to 300°K, lattice constants, and preparative data are reported for the systems {Gd3}[ScxFe2−x](Fe3)O12, {Gd2Y}[ScxFe2−x](Fe3)O12, {Gd3−xCax}[Fe2] (Fe3−xSix)O12, {Gd3−xCax} Fe5−xGexO12, {Gd3}Fe5−xAlxO12, {Gd3}[MgxFe2−x] (Fe3−xSix)O12, and for the three garnets {Gd2Ca}[ZrFe](Fe3)O12, {Gd0.6Y2.4}[ScFe](Fe3)O12, and {GdCa2}[Zr2](Fe3)O12.
The following model for the general features of the 0°K magnetic structures of the substituted gadolinium iron garnets is proposed. At 0°K, gadolinium iron garnet itself is an ideal Néel ferrimagnet. The moments of the octahedral Fe3+ ions and of the dodecahedral Gd3+ ions are strictly antiparallel to the moments of the tetrahedral Fe3+ ions. Replacement of some of the octahedral Fe3+ ions by nonmagnetic ions such as Sc3+ ions as in {Gd3}[ScxFe2−x](Fe3)O12 causes random canting of the tetrahedral Fe3+ ions. Because the strong interactions of the Gd3+ ion moments are with those of the tetrahedral Fe3+ ion moments, this leads also to random canting of the Gd3+ ion moments thereby reducing the contribution of the dodecahedral sublattice to the net spontaneous moment of the garnet. Replacement of the tetrahedral Fe3+ by nonmagnetic ions as in {Gd3−xCax}[Fe2] (Fe3−xSix)O12 causes random canting of the octahedral Fe3+ ion moments, but this is not expected to affect the alignment of the Gd3+ ion moments. Such substitution appears to have the effect of removing from contribution to the net moment, those Gd3+ ions which are not linked through oxygen atoms to at least one tetrahedral Fe3+ ion.
A comparison of the results on the systems {Gd3}[ScxFe2−x](Fe3)O12 and {Gd2Y}[ScxFe2−x](Fe3)O12 indicates that at or very near 0°K, the interaction in the dodecahedral sublattice appears to have a ferromagnetic component. Also the garnet {GdCa2}[Zr2](Fe3)O12 appears to be a weak ferromagnet.

Switching Properties of Single‐Crystal Ni☒Fe Films

A. Yelon, O. Voegeli, and E. W. Pugh

J. Appl. Phys. 36, 101 (1965); http://dx.doi.org/10.1063/1.1713853 (8 pages) | Cited 9 times

Online Publication Date: 14 July 2004

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Single‐crystal films of Ni☒Fe prepared by vapor deposition onto (100) planes of heated rocksalt substrates exhibit high‐speed and quasistatic magnetization switching behavior which is characteristic of biaxial elements and is not found in uniaxial or isotropic films. The biaxial critical curve for coherent‐rotational switching can be combined with partial switching and labyrinth‐switching concepts, adapted from observations in uniaxial films, to provide a semiquantitative explanation for observations in single‐crystal films. Direct verification of switching models here inferred from electronic measurements, and limited Bitter studies, will require Lorentz microscopy or detailed Bitter studies of walls formed during the switching process.

Heat Capacity of Glycerol Glass Between 1.5° and 4°K. Use of Glycerol as a Heat Exchange Medium in Low‐Temperature Calorimetry

R. S. Craig, C. W. Massena, and R. M. Mallya

J. Appl. Phys. 36, 108 (1965); http://dx.doi.org/10.1063/1.1713854 (5 pages) | Cited 22 times

Online Publication Date: 14 July 2004

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The heat capacity of glycerol glass was measured between 1.5° and 4°K. Below 2°K the heat capacity is in excess of that expected from theoretical considerations for an isotropic solid. The use of glycerol as a heat exchange medium is discussed and described.

High‐Temperature Electrical Resistivity and Allotropic Transformation Temperature of Hafnium

Ray G. Bedford

J. Appl. Phys. 36, 113 (1965); http://dx.doi.org/10.1063/1.1713855 (5 pages) | Cited 3 times

Online Publication Date: 14 July 2004

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The electrical resistivity of a Hf filament containing 4.9 at. % Zr was measured in the temperature interval from 1155° to 2250°K. The resistivity increases from 37 μΩ‐cm at room‐temperature to 187 μΩ‐cm at 2025°K where the alloy undergoes a transition from an hcp to a bcc structure with a corresponding decrease in resistivity to 173 μΩ‐cm. From data in the literature the transition temperature of pure Hf is estimated to be 2030°±30°K. Graphs of total emissivity versus temperature indicate that changes in the surface characteristics of the sample occurred during the measurements. After surface conditions became constant, the total hemispherical emissivity increased linearly with temperature from about 0.26 at 1200°K to 0.31 at 2000°K.

Magnetoelastic Waves in Yttrium Iron Garnet

W. Strauss

J. Appl. Phys. 36, 118 (1965); http://dx.doi.org/10.1063/1.1713856 (6 pages) | Cited 21 times

Online Publication Date: 14 July 2004

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Magnetoeleastic pulses with variable echo time were observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc∕sec with input power in the milliwatt range. At a fixed carrier frequency, pulses were observed for external magnetic fields ranging over several hundred oersted; characteristically the echo time increased with decreasing field. The carrier frequency‐magnetic field‐echo time behavior can be explained in terms of a θ=0 magnetoelastic disturbance traveling along the rod axis. It is launched at the position where ωc=γHi. The disturbance propagates along the rod axis to the nearer end‐face where it is reflected. On arrival back at the launch site, a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence. The experimental results can be understood in terms of a magnetoelastic wave packet with calculated travel time T = ∫ um−1dz ≈ ∫ us−1dz+ ∫ ue−1dz, where the group velocities, u, refer to magnetoelastic, spin, and elastic waves, respectively. Spin‐wave loss has been included and gives improved agreement between theory and experiment.

Temperature Dependence of Paramagnetic Relaxation at Point Defects in Vitreous Silica

J. G. Castle and D. W. Feldman

J. Appl. Phys. 36, 124 (1965); http://dx.doi.org/10.1063/1.1713857 (5 pages) | Cited 19 times

Online Publication Date: 14 July 2004

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Spin relaxation has been measured at 3 kOe and at lattice temperatures from 1.24° to 250°K for the E′ centers generated in one type of vitreous silica by 2‐MeV gamma rays. An unusual temperature dependence was found in which the spin‐lattice relaxation time varies roughly as T−2,5 over most of the range. All of the data are accurately fitted by analytical functions derived from a coupling of the individual defect centers to the vitreous host involving excess local strain due to mechanical resonances of about 4.1×1011 and 6.0×1012 cps at each E′ center. The strength of the coupling and the characteristic frequencies of mechanical resonance are similar to those in crystalline SiO2.

A Protected 100‐kG Superconducting Magnet

H. T. Coffey, J. K. Hulm, W. T. Reynolds, D. K. Fox, and R. E. Span

J. Appl. Phys. 36, 128 (1965); http://dx.doi.org/10.1063/1.1713858 (9 pages) | Cited 6 times

Online Publication Date: 14 July 2004

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Superconducting wire made from heavily cold‐worked ductile niobium‐titanium wire shows much less degradation in solenoids than does the corresponding widely used niobium‐zirconium alloy. The origin of this behavior is discussed in terms of flux jumping and the differences in metallurgical properties of the two alloy systems. The superior niobium‐titanium alloy has been used in the inner sections of a 100 000‐G solenoid which has been driven normal repeatedly without damage. Details of design, construction, and operation of this solenoid are discussed with particular reference to critical rate of excitation under flux creep conditions. The normalization properties of the solenoid are analyzed in terms of the thermal propagation model, and the voltage rise and temperature maximum are estimated from this model.

Dependence of Current Degradation in Superconducting Solenoids on Flux Pinning Energy and Temperature

R. W. Meyerhoff and B. H. Heise

J. Appl. Phys. 36, 137 (1965); http://dx.doi.org/10.1063/1.1713859 (3 pages) | Cited 3 times

Online Publication Date: 14 July 2004

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The cause of the current degradation of superconducting solenoids, a subject of continuing interest, is elucidated further in this work. Two types of measurement are reported here: (1) Flux pinning energies and straight wire critical currents of 0.25‐mm (10‐mil) Nb☒Zr wire are measured as a function of magnetic field. (2) Solenoid critical currents are reported as a function of temperature for the same material. These measurements indicate that high pinning energy causes flux jumping which causes solenoid degradation. They further indicate that pinning energy can be weakened by increasing the temperature; therefore, flux jumping and coil degradation can be suppressed by increasing the temperature
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