X-ray imaging with “edge-on” microchannel plate detector: first experimental results

A novel scanning slit X-ray imaging system based on an “edge-on” microchannel plate detector was developed and tested. Images were acquired at 50 kV(p) X-ray tube voltage with a limiting spatial resolution of 7 lp/mm. The pixel noise was measured to be 0.3 count/pixel/s for a 50×70 μm² pixel size. This photon counting detector can be considered to be virtually noise free.     

A generalized shaping filter method for higher order statistics

The shaping filter method has been a valuable tool for computing the stochastic response of linear dynamical systems to Gaussian stochastic inputs that are not delta-correlated. A straightforward extension of this method to the non-Gaussian case involves determining shaping filters that “match” higher order cumulant functions of the stochastic noise input. However it is easy to find simple examples of input signals for which this will not work because their cumulant functions cannot be realized as cumulant functions of the output of a linear system with delta-correlated input. This paper proposes an alternative shaping filter and it shows that it is applicable to an entire class of input signals for which the original shaping filter method fails.

A further extension of the shaping filter method is suggested, that involves the introduction of the concept of generalized moments that includes as particular cases both the moments and the cumulants.     

Range-to-cone-length relations for light ions in Cr

Curves of “range × cone length” and “diameter × cone length” are calculated for tracks left by low-energy light ions in ³⁹Cr. The calculations cover ions from helium to iron and are performed for 6.25N NaOH at 70°C and a standard etching time but can be easily extended to other etching conditions.     

Performance of the ATLAS electromagnetic calorimeter barrel module 0

The construction and performance of the barrel pre-series module 0 of the future ATLAS electromagnetic calorimeter at the LHC is described. The signal reconstruction and performance of ATLAS-like electronics has been studied. The signal to noise ratio for muons has been found to be 7.11±0.07. An energy resolution of better than (sampling term) has been obtained with electron beams of up to 245 GeV. The uniformity of the response to electrons in an area of Δη×Δφ=1.2×0.075 has been measured to be better than 0.8%.     

Guides “bimorphes” d''ondes ultrasoniques “bimorph” ultrasonic wave guides”

An analysis of the dispersion of elastic waves is presented for two types of long ultrasonics wave-guides that we qualify of “bimorph”: (i) a “three-layer” guide made of two different materials and (ii) a “clad core” guide built up of a rectangular core surrounded by a cladding, the materials of the rod and cladding having different properties. An analytical model is proposed to describe the extensional, flexural and torsional motions in “bimorph” wave guides having two geometrical and material symmetry axes. The asymptotic behaviour of the model allows one to select the material properties which lead to modes guided essentially either in the central layer or in the core of the bimorph guide. Moreover, the dispersive properties of a “bimorph” can be controlled through the choice of geometrical and material parameters.     

Experimental and analytical study of early time material processing, in a collapsing shaped - charge liner, using “softly - recovered” partially - collapsed copper liners

It is not yet clear what detailed deformation mechanisms enable copper shaped charge jets to exhibit the extraordinarily high ductility, which characterizes their dynamic behavior. The study described in this paper seeks to find some of these answers, by stopping the liner collapse process at various intermediate stages, and examining the grain structures in the partially collapsed liners.

Well characterized OFE copper shaped-charge liners, assembled into a cylindrical polycarbonate case, of constant length and volume, were partially collapsed, with reduced-weight cylindrical explosive charges. A series of increasing explosive charge weights were used to obtain progressively greater partial deformations on individual copper liners. The shock waves from the varying length explosive charges were coupled to the copper liners through intermediate water fill, which was in direct contact with the rear of the liners.

The series of partially collapsed copper liner was captured by “soft recovery” in low density polystyrene. Flash radiography prior to liner recovery, confirmed that the unexpected shapes of the recovered partially collapsed liners, actually existed prior to their entering the recovery medium and were not the result of the recovery process itself. This was an early concern when the unusual shapes of the recovered liners were first seen.

These shapes were also independently confirmed by a series of computations at Los Alamos National Laboratory, using MESA 2D.

A comparison of the photomicrographs of undeformed virgin copper liners andd the series of partially collapsed liners, shows regions on the inner apex near the liner axis where plastic flow has occured, with very substantial modifications (refinement and elongation in grain structure even for the small deformations which barely change the overall liner shape.

Time dependent strain and strain rate computations, using LaGrangean tracer markers, indicate very large strain rates, between 3×10⁷/sec. and 4.7×10⁷/sec. in those regions with plastic flow where grain refinement and elongation are seen, even with very small overall deformation.

It is believed likely that this early time material processing and grain refinement, arising from the localized plastic deformation of the liner, plays a key role in preparing the liner material structure, so that it can exhibit the high dynamic ductility, characteristic of copper shaped-charge jets.     

Investigation of the dependence of the contact resistance on the external gold layer in AuNiGeAu/n-GaAs

The contact resistance of an Au/Ni/Ge/Au metallization system on n-GaAs exhibits a drop in contact resistance from 13.3 × 10⁻⁶ ω cm² to 8.6 × 10⁻⁶ ω cm² when the external gold layer is varied from 800 Å to 6000 Å in thickness. Secondary ion mass spectroscopy indicates that the improvement in contact resistance is due to the gold's “regulating” the amount of NiAs formed, leading to an increase in the area fraction covered by the Ni₂GeAs. The result shows that the external gold layer deposited to improve bonding should be optimized in thickness. This role played by the external gold layer of the metal system in affecting the contact resistance has not been previously studied.     

Addition of “Living” Polymers onto C60.

Various “living” polymers were grafted onto C₆₀ The number of arms of the so obtained “star” molecules can be controlled by stoechiometry and/or by varying the reactivity of the carbanion on the “living” chain against a double bond on the C₆₀. Even the oxanion of “living” polyethylenoxide is able to add onto the reactive double bonds on C₆₀. In some conditions, the carbanions present on these alkaline salts of grafted fullerenes becomes able to initiate anionic polymerization of vinyl monomers. Using “living” poly(phenylvinylsulfoxide) as a precursor polymer for PA, polyacetylene chains could be attached to the fullerene.     

On the nature of “dynamic” strength of brittle bodies

The enhanced strength observed for bodies under dynamic loading has been attributed to fracturing duration, i.e. the time interval between the commencement of fracture at the most heavily loaded point of the body and the instant of completion of fracture which is recorded by a sensor. The “dynamic” strength of brittle bodies is shown to be related to the crack formation process.     

Excited-state absorption at 1.57 μm in U:CaF2 and Co:ZnSe saturable absorbers

Appreciable excited-state absorption (ESA) in U²⁺:CaF₂ and Co²⁺:ZnSe saturable absorbers was measured at λ=1.573 μm by optical transmission versus light fluence curves of 30–40 ns long pulses. The ground- and excited-state absorption cross-sections obtained were (9.15±0.3)×10⁻²⁰ and (3.6±0.2)×10⁻²⁰ cm², respectively, for U²⁺:CaF₂, and (57±4)×10⁻²⁰ and (12.5±1)×10⁻²⁰ cm² for Co²⁺:ZnSe. Thus, ESA is not negligible in U²⁺:CaF₂ and Co²⁺:ZnSe, as previously estimated.     

A novel gamma-ray imaging concept using “edge-on” microchannel plate detector

The “edge-on” illuminated microchannel plate (MCP) position-sensitive detector (PSD) is used for gamma-ray imaging for the first time. The superior position resolution of the MCP is combined with high detection efficiency due to the “edge-on” illumination mode. The results of imaging a 15 μCi ¹³⁷Cs source (662 keV quantum energy) are presented.     

An Investigation of the Measurements Systems Analysis “Analytic Method” for Attribute Gages

Three automotive corporations have developed and sanctioned the recently revised reference manual entitled Measurement Systems Analysis. This “standard” contains a procedure, called the “analytic method,” whose purpose is to estimate the gage bias and gage repeatability of an attribute gage. An improved estimation procedure for this standard is presented. The improved estimation procedure yields more accurate estimates than those obtained using the procedures currently presented in the standard. In addition, the improved procedure allows more flexibility in data collection than the current test protocol. A simulation study that evaluates the estimation procedure of the current standard and compares it with the improved estimation procedure is presented. Errors that are contained in the present standard are also noted.     

Cyclic deformation response and dislocation structure of Cu single crystals oriented for double slip

Cyclic deformation behavior of double-slip oriented Cu single crystals with a stress axis in the [034] direction was investigated under plastic strain control mode for a shear strain amplitude range of 1 × 10⁻⁴ to 5 × 10⁻³. Dislocation structures in the tested samples were observed using a transmission electronic microscope. It has been found that the effect of the operation of critical slip in these [034] crystals on cyclic responses and dislocation structures is nearly the same as that of increase in strain amplitude. The nucleation stress and number of cycles for PSB formation at each specific strain amplitude in the double-slip oriented crystals were found to be both considerably lower than those observed in single-slip oriented crystals. This observation is in a good agreement with the Kuhlmann-Wilsdorf and Laird analysis, in that the formation of PSBs is associated with glide behavior on the secondary slip system. A dislocation “cord” structure has also been observed and is believed to be caused by the operation of the cross-slip system during cyclic deformation. Labyrinth wall structures were found to form with increase in strain amplitude by the operation of critical slip and cross-slip systems. However, the formation of labyrinth structure was suppressed by the coplanar slip at high strain amplitudes.     

“In Vitro” Studies on Buccoadhesive Tablet Formulations of Hydrocortisone Hemisuccinate

Different bioadhesive and matrix-forming polymers were evaluated using “in-vitro” tests to identify a potentially convenient “in-vivo” formulation for the sustained delivery of hydrocortisone hemisuccinate to the oral cavity. The selected composition allows an erosion-diffusion mechanism coherent with the low hydrosolubility of the drug and with potential advantages for both the patient and the manufacturer.     

A “Six Sigma”© Case Study: G.E.P. Box's Paper Helicopter Experiment—Part B

This article presents an application of the “Six Sigma” DMAIC model to G.E.P. Box's famous “paper helicopter” experiment. The Improve and Control Phases are presented here. The Define, Measure, and Analyze Phases were presented in an earlier paper. The intent of this article is to present the reader with a case study for structuring a “Six Sigma” project.     

“Low-Tech” Innovations

This paper is about an industrial sector which, according to the usual socio-scientific indicators, is referred to as “low-tech”, respectively as non-research intensive and which mostly comprises “traditional” industries. The interest in this sector is motivated by the contradictory situation that, on the one hand, the debate about the perspectives of modern societies focuses on the rapidly growing importance of technological innovations, knowledge and research-intensive economic sectors while, on the other hand, traditional industries make up a considerable fraction of employment and production, especially also in developed economies. On the basis of the results of extensive empirical research, this contribution tries to find answers to the basic question, whether one can speak of an innovation mode typical of the low-tech sector. The institutional based innovation systems approach forms the categorical basis of the analysis. In order to elucidate the specific features of low-tech innovations, they are, in conclusion, compared to the general characteristics of high-tech-based innovation processes.     

A “Six Sigma”© Black Belt Case Study: G.E.P. Box's Paper Helicopter Experiment Part A

This article presents an application of the “Six Sigma” DMAIC model to G.E.P. Box's famous “paper helicopter” experiment. The define, measure, and analyze phases are presented here, and the improve and control phases are presented in a follow-up article. The intent of this article is to present the reader with a case study for structuring a “Six Sigma” Black Belt project.     

Hydrogen chemisorption on the Si(1 1 1)√3 × √3R30 °-Al, -Ga, -B surfaces: An ab initio HF/DFT molecular orbital modelling using atomic clusters

A comprehensive study of atomic hydrogen chemisorption on the Si(1 1 1) √3 × √3R30 ° -Al, -Ga and -B cluster modelled surfaces is presented using Hartree-Fock/density functional theory methods. Extrapolation of the results to the extended (1 1 1) silicon surface is also discussed. It is found that the chemisorption of hydrogen on the Al and Ga terminated surfaces induces a transition from the √3 × √3 structure to a local 1 × 1: H-like reconstruction with a stable SiAl (or SiGa) sites. The subsurface boron induced √3 × √3 reconstruction is also lifted by hydrogen chemisorption but, in this case, boron adatoms are likely to be segregated on the surface, predominantly as BH or/and BH₂.     

Uniformity control of 3 inch GaN/InGaN layers grown in Planetary Reactors®

We present results obtained from a 2400G3HT reactor with a maximum wafer capacity of 8×3 inch. To achieve uniformity of the growth, we increased the temperature uniformity on each satellite to 0.9°C and that from satellite to satellite to 0.8°C. The optimum reactor geometry has been found by extensive modeling of the reactor design. Thus, an optimization of uniformity and efficiency has been achieved. GaN, InGaN/GaN multi quantum wells, GaN:Si, GaN:Mg and AlGaN were obtained on 5×3 inch substrates by simple scaling of the corresponding process parameters of the 6×2 inch configuration. We demonstrate GaN:Si and GaN:Mg doping uniformity with a standard deviation of less than 5%, with thickness uniformities of less than 1.7% standard deviation without any edge exclusion. InGaN/GaN, quantum well emission at 480 nm shows a standard deviation of 1–2% without rim exclusion. We grew AlGaN with about 10% Al content and less than 2% standard deviation in Al composition across the 3 inch substrate. Simple electroluminescence test structures, consisting of a GaN:Si buffer, followed by a five-period InGaN/GaN quantum well and covered by a GaN:Mg cap with emission wavelengths of about 460 nm show wavelength variations across 3 inch wafers of less than 3 nm. All these results demonstrate that the AIXTRON Planetary Reactor® is a very flexible tool for mass production application, especially with respect to upgrading the system to larger wafer diameters, as is already well known from the standard GaAs and InP applications that are available up to 5×8 inch configurations.