Development program to produce mullite fiber insulation

Processing methods were utilized to form a mullite fiber-Kaowool felt. The formation of a blended felt using the Rotoformer wet-laying method was successful. Felt products were evaluated for tensile strength, thermal stability, thermal conductivity and structural integrity at 1259 C and 1371 C. Textile processing methods failed in an attempt to form a yarn from staple and multifilament mullite fiber due to fiber damage through mechanical handling. The refractoriness of pure Kaowool ceramic fiber is improved with additions of 30% or greater mullite fiber

Development of fine diameter mullite fiber

Results are presented of a program to develop and evaluate mullite fiber with a mean diameter under two microns. The two micron fiber is produced by a blowing process at room temperature from a low viscosity (10-25 poise) solution. The blown fiber was evaluated for dimensional stability in thermal cycling to 1371 C, and was equivalent to the 5 micron spun B and W mullite fiber. An additive study was conducted to evaluate substitutes for the boron. Three levels of chromium, lithium fluoride, and magnesium were added to the standard composition in place of boron and the fiber produced was evaluated for chemical and dimensional stability in thermal cycling to 1371 C. The magnesium was the most chemically stable, but the chrome additive imparted the best dimensional stability

A New Linear Inductive Voltage Adder Driver for the Saturn Accelerator

Saturn is a dual-purpose accelerator. It can be operated as a large-area flash x-ray source for simulation testing or as a Z-pinch driver especially for K-line x-ray production. In the first mode, the accelerator is fitted with three concentric-ring 2-MV electron diodes, while in the Z-pinch mode the current of all the modules is combined via a post-hole convolute arrangement and driven through a cylindrical array of very fine wires. We present here a point design for a new Saturn class driver based on a number of linear inductive voltage adders connected in parallel. A technology recently implemented at the Institute of High Current Electronics in Tomsk (Russia) is being utilized[1]. In the present design we eliminate Marx generators and pulse-forming networks. Each inductive voltage adder cavity is directly fed by a number of fast 100-kV small-size capacitors arranged in a circular array around each accelerating gap. The number of capacitors connected in parallel to each cavity defines the total maximum current. By selecting low inductance switches, voltage pulses as short as 30-50-ns FWHM can be directly achieved.Comment: 3 pages, 4 figures. This paper is submitted for the 20th Linear Accelerator Conference LINAC2000, Monterey, C

Single and Many Particle Correlation Functions and Uniform Phase Bases for Strongly Correlated Systems

The need for suitable many or infinite fermion correlation functions to describe some low dimensional strongly correlated systems is discussed. This is linked to the need for a correlated basis, in which the ground state may be postive definite, and in which single particle correlations may suffice. A particular trial basis is proposed, and applied to a certain quasi-1D model. The model is a strip of the 2D square lattice wrapped around a cylinder, and is related to the ladder geometries, but with periodic instead of open boundary conditions along the edges. Analysis involves a novel mean-field approach and exact diagonalisation. The model has a paramagnetic region and a Nagaoka ferromagnetic region. The proposed basis is well suited to the model, and single particle correlations in it have power law decay for the paramagnet, where the charge motion is qualitatively hard core bosonic. The mean field also leads to a BCS-type model with single particle long range order.Comment: 23 pages, in plain tex, 12 Postscript figures included. Accepted for publication in J.Physics : Condensed Matte

Evolution of Nuclear Shell Structure due to the Pion Exchange Potential

The evolution of nuclear shell structure is investigated for the first time within density-dependent relativistic Hartree-Fock theory and the role of $\pi$-exchange potential is studied in detail. The energy differences between the neutron orbits \Lrb{\nu1h_{9/2},\nu 1i_{13/2}} in the N=82 isotones and between the proton ones \Lrb{\pi1g_{7/2},\pi1h_{11/2}} in the Z=50 isotopes are extracted as a function of neutron excess $N-Z$. A kink around $Z = 58$ for the N=82 isotones is found as an effect resulting from pion correlations. It is shown that the inclusion of $\pi$-coupling plays a central role to provide realistic isospin dependence of the energy differences. In particular, the tensor part of the $\pi$-coupling has an important effect on the characteristic isospin dependence observed in recent experiments.Comment: 4 pages and 4 figure

Relativistic Effects in Nuclear Matter and Nuclei

The status of relativistic nuclear many-body calculations of nuclear systems to be built up in terms of protons and neutrons is reviewed. In detail, relativistic effects on several aspects of nuclear matter such as the effective mass, saturation mechanism, and the symmetry energy are considered. This review will especially focus on isospin asymmetric issues, since these aspects are of high interest in astrophysical and nuclear structure studies. Furthermore, from the experimental side these aspects are experiencing an additional boost from a new generation of radioactive beam facilities, e.g. the future GSI facility FAIR in Germany or SPIRAL2 at GANIL/France. Finally, the prospects of studying finite nuclei in microscopic calculations which are based on realistic $NN$ interactions by including relativistic effects in calculations of low momentum interactions are discussed.Comment: 57 pages, 16 figure

Exact Quantum Search by Parallel Unitary Discrimination Schemes

We study the unsorted database search problem with items $N$ from the viewpoint of unitary discrimination. Instead of considering the famous $O(\sqrt{N})$ Grover's the bounded-error algorithm for the original problem, we seek for the results about the exact algorithms, i.e. the ones succeed with certainty. Under the standard oracle model $\sum_j (-1)^{\delta_{\tau j}}|j>< j|$, we demonstrate a tight lower bound ${2/3}N+o(N)$ of the number of queries for any parallel scheme with unentangled input states. With the assistance of entanglement, we obtain a general lower bound ${1/2}(N-\sqrt{N})$. We provide concrete examples to illustrate our results. In particular, we show that the case of N=6 can be solved exactly with only two queries by using a bipartite entangled input state. Our results indicate that in the standard oracle model the complexity of exact quantum search with one unique solution can be strictly less than that of the calculation of OR function.Comment: 8 pages (revtex4), 6 figures. Revised version with some typo error corrections and some clearer statement. Accepted by Phys.Rev.A .Comments are welcome

High-Pressure Induced Structural Phase Transition in CaCrO4: Evidence from Raman Scattering Studies

Raman spectroscopic studies have been carried out on CaCrO4 under pressure up to 26GPa at ambient temperature. The Raman spectra showed CaCrO4 experienced a continuous structural phase transition started at near 6GPa, and finished at about 10GPa. It is found that the high-pressure phase could be quenched to ambient conditions. Pressure dependence of the Raman peaks suggested there existed four pressure regions related to different structural characters. We discussed these characters and inferred that the nonreversible structural transition in CaCrO4, most likely was from a zircon-type (I41/amd) ambient phase to a scheelite-type high pressure structure (I41/a).Comment: submitte