[en] Radio wave absorption caused by ionospheric irregularities is discussed. Saturation of the decay instability in the presence of a magnetic field is considered. (U.S.)

[en] Short communication

[en] The concentration profiles of arsenic implanted in chemical vapor deposited tungsten silicides on p-type Si substrate are described. As ions were implanted directly in tungsten silicide layers at energies of 40, 100, and 160 keV with a dose of 1 x 10¹⁶ cm^-2. The As concentration profiles were obtained by means of 1.5 MeV He⁺ Rutherford backscattering measurements. Projected ranges R/sub p/ and projected stragglings ΔR/sub p/ for As implantation in W, WSi/sub 2.0/, and WSi/sub 2.6/ layers were calculated by an interpolation program as function of acceleration voltage and give theoretical As concentration profiles. The observed profiles agree well with theoretical profiles and show that R/sub p/ and ΔR/sub p/ values are useful for design of self-aligned implantation process in tungsten silicide gates

[en] The possibility of phase locking of relativistic magnetrons using low power injection signals is studied. The initial long pulse (0.2-1 μs) experiment showed the importance of voltage regulation for single-mode and stable frequency operation, the excitation of modes other than the dominating mode due to excessive voltage variation was observed with in one pulse as well as on shot-to-shot bases. It is found that voltage ripples on the order of 5% directly affect the output power stability. In addition, the experiment also indicated the possibility of using velvet as the cathode material for achieving long microwave pulses. Preliminary results of a long pulse, high repetition rate (1 μs, 4 pps) highly stable magnetron system (700 kV, 770 A) are presented

[en] This report contains a technical progress summary of the research conducted under the auspices of DOE Grant No. DE-AC02-91-ER40648, ''Experimental and Theoretical Investigations of High Gradient Acceleration''. This grant supports three research tasks: Task A consists of the design, fabrication and testing of a 17GHz RF photocathode gun, which can produce 2ps electron pulses with up to 1nC of charge at 2MeV energy and at a 1OHz repetition rate. Task B supports the testing of high gradient acceleration at 33GHz structure, and Task C comprises theoretical investigations, both in support of the experimental tasks and on critical physics issues for the development of high energy linear colliders

[en] The MIT Lincoln Laboratory is investigating the possibility of building a free electron laser (FEL) operating at an average power of about 7 kW at wavelengths of 500--600 nm. Additional specifications for the FEL include a bandwidth of less than 0.1 cm^-1 and a micropulse separation of less than 10 ns. The design study has investigated the basic design parameters of the FEL including an analysis of the electron accelerator, beam line, wiggler and optical cavity. A nonlinear model of the FEL has been used to calculate the FEL gain and efficiency. The required output power appears achievable from an FEL operating at more than 1% efficiency with a conventional RF accelerator. Details of the FEL design are presented in this report which represent the final report for the year from September 1, 1989 to August 31, 1990. 28 refs., 13 figs., 5 tabs

[en] NiCuZn ferrite nanoparticles with composition of Ni_xCu_yZn_1-x-yFe₂O₄ (where x=0.15-0.5 and y=0-0.35) were prepared by the chemical co-precipitation method at various reaction temperatures with a final pH value of 12. From the analysis of X-ray diffraction patterns, the nanocrystalline NiCuZn ferrite particles could be obtained at pH=12 and reaction temperature between 30 and 90 deg. C with the reaction time of 6 h. The particle size ranges from 2 to 60 nm by observation of transmission electron microscopy. Uniform size of cubic crystalline particles with particle size of about 30 nm were obtained at reaction temperature of 70 deg. C. The ferrite powders were compressed and sintered at various temperatures between 800 and 1000 deg. C for 2 h. According to experimental results, the NiCuZn ferrite powders with high Cu content could be sintered at about 800 deg. C. The density of the sintered Ni_0.18Cu_0.31Zn_0.51Fe₂O₄ ferrite was 5.01 g/cm³ after sintering at 900 deg. C. The initial permeability μ of this sintered sample is about 390 at frequency of 1 MHz. Its H_c value is about 0.7 Oe and B_s congruent with 3100 G. We found that Cu substitution for Ni in NiZn ferrite would enhance the densification of the ferrite and subsequently increases the μ value as well as B_s value, and decreases the H_c value of the sintered ferrite

[en] The anodic dissolution of Be was studied in Cl^- and ClO₄^-solutions of methanol, ethanol and N,N-dimethylformamide with water contents < 0.1 g/l at 25⁰C. The apparent valence of Be ions going into solution ranged from 0.37 to 1.8. The lower values were obtained in alcohol solutions with Cl^-. Considerable gas evolution was noted from the Be surface. The low and anomalous valences are attributed mainly to a chemical dissolution of the metal by reaction with the solution. This reaction is reported to be catalysed by Cl^-. The effect of the low water content is to hinder the reforming of an oxide or hydroxide film that protects the Be from chemical attack. The numerical value of the valence is mainly dependent on the rate that the Be will chemically react with the media once a current flows that disrupts the surface film. (author)

[en] Highly reliable ultrathin low-pressure chemical-vapor-deposited (LPCVD) tantalum pentoxide (Ta₂O₅) capacitors were fabricated by using high-density plasma (HDP) annealing in N₂O at 400 deg. C after film deposition. It was found that HDP annealing in N₂O could significantly reduce the leakage current of Ta₂O₅ capacitors so as to produce better time-dependent dielectric breakdown characteristics than either conventional oxygen-plasma annealing or high-density plasma annealing in O₂. It was also found that HDP annealing in N₂O will not significantly increase the thickness of interface layer between Ta₂O₅ and the underlying silicon bottom electrode. Therefore, highly reliable ultrathin Ta₂O₅ capacitors can be fabricated by using HDP annealing in N₂O. The leakage current mechanism was also investigated. It was found that Poole-Frenkel emission and Fowler Nordheim (FN) tunneling was the main leakage mechanism in low and high electric field, respectively, as for the deposited Ta₂O₅ films. For the N₂O HDP-annealed Ta₂O₅ films, it was found that, the main leakage mechanism was Schottky emission in low electric field and Poole-Frenkel emission in high electric field

[en] An analysis of the internal strain degrees of freedom in zircon-structure crystals RMO₄ is given. These are related to local distortions in the neighbourhood of the R^3- ions, and hence to the orbit-lattice coupling coefficients. The corresponding spin-lattice coupling coefficients are obtained for distortions involved in Jahn-Teller phase transitions and comparisons with experimental values are made for TmVO₄ and DyVO₄. (author)