68 kbit capacity 16 µm-period magnetic bubble memory chip design with 2 µm minimum features

A bubble propagating structure that operates well on a 14 μm to 18 μm propagate period with a nominal 2 μm minimum feature size has been designed. The structure consists of only 1 discrete permalloy feature per circuit period. Sixty-eight kbit-capacity memory chips based on such structures have been designed, built, characterized, packaged and the packages have been characterized. The chip is organized as a set of minor (storage) loops with separate write and read major lines. The bubble manipulating functions, of which the replicate and transfer gates are the most critical, have also been designed with 2 μm minimum features. The design is adequate to provide a 14 Oe bias field margin range with drive fields of about 35 Oe, using a bubble garnet material with approximately 170 Oe free bubble collapse field. Sixty-eight kbit single loop shift register type chips designed using similar propagating structures, however, provide over 20 Oe bias field margin ranges with drive fields of about 35 Oe.     

Liquid phase epitaxy and magneto-optical properties at 1.152 µm and 1.064 µm of garnet films on GdGaG

Several ferrimagnetic garnet compositions have been studied in view of their use in integrated optics. Films of (Sc,Ga):YIG, (Gd,Ga):YIG, (Pr,Ga):YbIG and (Pr,Bi,Ga):YbIG have been grown by liquid phase epitaxy on <111> GdGaG and fully characterized by classical and guided waves experiments at 1.152 and 1.064μm wavelengthes.     

Design, development and experiment of a 1.5 T MgB2 superconducting test magnet

Superconducting magnets using MgB₂ tapes are potentially applicable in many areas, such as medical magnetic resonance imaging and fault current limiting. Under conduction cooling environments, the magnets can work at 15-20 K. In this work, a solenoid structured magnet with ∅ 100 mm bore is designed, built and tested. The maximum field at its center is up to 1.5 T. The field homogeneity, the thermal stability and the quench characteristics in the magnet are also investigated.     

The high field superferric magnet Design and test of a new dipole magnet for future hadron colliders

The Texas Accelerator Center has successfully tested a 6 T superferric dipole magnet of a design appropriate for future hadron colliders. The magnet surpassed the design field (90% of the short sample limit) on its first quench without training. The measured field quality is in excellent agreement with design calculations and meets collider requirements. The magnetic field design was developed at Rice University and is the subject of a Master's thesis. The features of the design include simple construction, efficient use of superconductor, and adequate containment of magnetic forces. A straightforward extension of the design to an 8 T dipole is under development. The high-field superferric magnet constitutes a significant improvement in magnet performance and cost for future accelerators.     

Operation of a 100-bit, 2.6 µm bubble shift register

Complete circuit operation for a small 100-bit serial shift register memory with a 10.6 μm period fabricated on a garnet wafer using electron beam lithography and single level all-permalloy technology is reported. Overall circuit operation including generation, propagation, and detection was achieved with a 6 Oe bias margin using a 1 kHz rotating field. Although the circuit design and fabrication techniques were not optimized, we believe that this is the first published report of complete circuit operation for a single level device with bubbles as small as 2.6 μm. The performance of two different types of chevron expander detectors and two different generators was evaluated and circuits combining disk generators with herringbone detectors were found to provide the best overall operating margin. At low speeds (∼5 Hz) high-bias failures were caused by failure of the domains to strip out fully in the detector while the low bias limit was determined by the introduction of spurious bubbles into the track near the generator.     

Thermal processes and stability of a superconductive dipole magnet with pulsed heating of the winding

Results of an experimental and numerical study of thermal processes occurring upon pulsed heating of the superconductive winding of a dipole magnet are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 301–305, February, 1985.     

Design and magnetic results on a 3 Tesla, 10 Weber spectrometer magnet at Saclay

A big spectrometer magnet, three hundred tons, has been successfully designed and measured at Saclay. Its main features are a fixed working induction of 3 Tesla and a total flux of 10 Weber. The coils are conventional and for the yoke we use a scrapped cyclotron. The spectrometer is of an Elbek type and its optic characteristics are a momentum analysis range from 0.6 to 1.4 GeV/c, with a 5.10^-4resolution. The angular analysis lies between -5° and 65° around the target. The magnetic study and optimisation of the magnet has been done with Poisson, bidimensional code and Ledi which is a simplified three dimensional code developed for fully saturated iron magnets.     

Optimal cool-down time of a 4 K superconducting magnet cooled by a two-stage cryocooler

A cool-down time is one of the major factors in many cryocooler applications, especially for the design of conduction-cooled superconducting devices. Cool-down time means a time cooling a thermal mass from a room-temperature to cryogenic-temperature within a stipulated amount of time. The estimation of cool-down time seeks the elapsed time to cool the thermal object by a cryocooler during initial cool-down process. This procedure includes the dimension and properties of thermal object, heat transfer analysis for cryogenic load, thermal interface between cold mass and cryocooler, and available refrigeration capacity of cryocooler. The proposed method is applied to the specific cooling system for 3 T superconducting magnet cooled by a two-stage GM cryocooler. The result is compared with that of experiment, showing that proposed method has a good agreement with experiment. In addition, the initial cool-down time can be shortened by employing thermal link between the cold mass and first-stage of cryocooler. Through a rigorous modeling and analysis taking into account the effect of thermal link size, it is concluded that there exists an optimal cool-down time during initial cooling in conduction-cooled superconducting magnet system.     

Petri Net modelling approach for analysing the behaviour of Wnt/ β ‐catenin and Wnt/ Ca2+ signalling pathways in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease that may result in arrhythmia, heart failure and sudden death. The hallmark pathological findings are progressive myocyte loss and fibro fatty replacement, with a predilection for the right ventricle. This study focuses on the adipose tissue formation in cardiomyocyte by considering the signal transduction pathways including Wnt/ β ‐catenin and Wnt/Ca²⁺ regulation system. These pathways are modelled and analysed using stochastic petri nets (SPN) in order to increase our comprehension of ARVC and in turn its treatment regimen. The Wnt/ β ‐catenin model predicts that the dysregulation or absence of Wnt signalling, inhibition of dishevelled and elevation of glycogen synthase kinase 3 along with casein kinase I are key cytotoxic events resulting in apoptosis. Moreover, the Wnt/Ca²⁺ SPN model demonstrates that the Bcl2 gene inhibited by c‐Jun N‐terminal kinase protein in the event of endoplasmic reticulum stress due to action potential and increased amount of intracellular Ca²⁺ which recovers the Ca²⁺ homeostasis by phospholipase C, this event positively regulates the Bcl2 to suppress the mitochondrial apoptosis which causes ARVC.Inspec keywords: molecular biophysics, enzymes, cancer, muscle, Petri nets, cellular biophysics, bioelectric potentials, biomembranes, tumours, cardiology, genetics, biochemistry, calciumOther keywords: heart failure, sudden death, hallmark pathological findings, progressive myocyte loss, fibro fatty replacement, adipose tissue formation, signal transduction pathways, Ca²⁺ regulation system, stochastic petri nets, ARVC, $β‐catenin model, Wnt signalling, glycogen synthase kinase 3, Bcl2 gene, c‐Jun N‐terminal kinase protein, petri Net modelling approach, Ca²⁺ signalling pathways, arrhythmogenic right ventricular cardiomyopathy, inherited heart muscle disease, Ca²⁺ SPN model, Ca     

Design analysis of a solid nitrogen cooled “permanent” high-temperature superconducting magnet system

Potential performance advantages of a solid nitrogen cooled “permanent” high-temperature superconducting (SN2/HTS) magnet system over a liquid helium cooled low-temperature superconducting (LHe/LTS) system are explored. The SN2/HTS system design includes a second solid heat capacitor that cools a radiation shield. Recooling of the heat capacitors is performed with a demountable cryocooler. The SN2/HTS system offers both enhanced stability and improved portability over a LHe/LTS system.Design codes are constructed to compare the SN2/HTS system design with a LHe/LTS design for a general permanent superconducting magnet system employing a room temperature bore. The codes predict the system volume and mass that should be expected for a given set of design requirements, i.e. field strength and bore size, and a given set of conductor properties. The results indicate that present HTS conductor critical current and index are not yet sufficient for producing SN2/HTS systems of a size that is comparable with that expected for a LHe/LTS system; however, the conductor properties of Bi2223/Ag have been consistently improving, and new HTS conductors are expected to be developed in the near future. The codes are used to determine the minimum Bi2223/Ag conductor performance required for a SN2/HTS system to be competitive with a LHe/LTS system.     

Design,modification and test of the conduction cooled high-current current leads for the superconducting magnet

Conduction cooled current leads, which bring the current from the room temperature terminal down to the cryogenic environment, were used in common recently in large scale superconducting accelerators for its low cost, sample design and low heat load. In practice, the current lead is designed contained in a stainless steel tube. The heat load can be incepted in steps by thermal anchors, where one end is attached to the stainless steel tube, while the other end is connected with the cold shield of the cryomodule. Since the limitation of the welding technique, a thicker stainless steel tube needs to be used, and hence the thermal anchors cannot provide enough pressure to deform the tube enough to be in direct contact with the current lead, which may lead to temperature instability and bring extra heat load to the cryogenic system. An excellent option of epoxy filled current lead can realize the fully contact and reduce the heat load effectively. This paper will present the process of the current lead design, optimization, numerical simulation and cryogenic test, the test results show that the current lead can keep in a stable operation and low heat load.     

Design and optimization of the 12.5 T EFDA dipole magnet

The aim of this paper is to provide an overview of a recent study carried out—within the framework of the European Fusion Program—to design a 12.5 T superconducting dipole. By focusing on the CICC based design option, the overall design procedure is presented. In particular, the 2D optimization of the dipole cross section is described including the magneto-static analysis of the winding and iron yoke, the mechanical analysis of the conductor jacket, insulation and outer cylinder, the conductor hot spot analysis, etc. As far as the thermo-hydraulic design is concerned, simulations of nominal as well as offset operating conditions (e.g., magnet quench) are presented with emphasis on their role played in the overall magnet design. For example, diagrams reporting the helium heat removal capabilities, pressure drop, mass flow, etc. are shown and their usefulness as guidance for the magnet designer described.     

An investigation of the uncertainty in reproducing the units of pulsed electric and magnetic field strengths in a standard system for producing very-short electromagnetic pulses with a rise time of 20 psec

A method of reproducing the units of pulsed electric and magnetic field strength in a standard system with a pulse rise time of less than 20 psec, constructed using a “cone over a plane” field-generating system is considered. The components of the uncertainty in reproducing the units are analyzed. The extended uncertainty is not greater than 6.5%.     

A standard system for producing very-short electromagnetic pulses with a rise time of 20 psec

The results of the development and construction of a standard set of units of electric and magnetic field pulse strengths with a pulse length of down to 1 nsec and a rise time of less than 20 psec, using a “cone over a plane” field-generating system are presented. Investigations were made of its amplitude-time characteristics using broadband measuring converters and couplers, included in the measuring system.     

Design and characterisation of a pulsed neutron interrogation facility

The Joint Research Centre recently obtained a license to operate a new experimental device intended for research in the field of nuclear safeguards. The research projects currently being planned for the new device includes mass determination of fissile materials in matrices and detection of contraband non-nuclear materials. The device incorporates a commercial pulsed neutron generator and a large graphite mantle surrounding the sample cavity. In this configuration, a relatively high thermal neutron flux with a long lifetime is achieved inside the sample cavity. By pulsing the neutron generator, a sample may be interrogated by a pure thermal neutron flux during repeated time periods. The paper reports on the design of the new device and the pulsed fast and thermal neutron source. The thermal neutron flux caused by the neutron generator and the graphite structure has been characterised by foil activation, fission chamber and (3)He proportional counter measurements.     

Effects of noise and time delay on E2F's expression level in a bistable Rb‐E2F gene’s regulatory network

The bistable Rb‐E2F gene regulatory network plays a central role in regulating cellular proliferation‐quiescence transition. Based on Gillespie''s chemical Langevin method, the stochastic bistable Rb‐E2F gene’s regulatory network with time delays is proposed. It is found that under the moderate intensity of internal noise, delay in the Cyclin E synthesis rate can greatly increase the average concentration value of E2F. When the delay is considered in both E2F‐related positive feedback loops, within a specific range of delay (3‐13)hr, the average expression of E2F is significantly increased. Also, this range is in the scope with that experimentally given by Dong et al. [65]. By analysing the quasi‐potential curves at different delay times, simulation results show that delay regulates the dynamic behaviour of the system in the following way: small delay stabilises the bistable system; the medium delay is conducive to a high steady‐state, making the system fluctuate near the high steady‐state; large delay induces approximately periodic transitions between high and low steady‐state. Therefore, by regulating noise and time delay, the cell itself can control the expression level of E2F to respond to different situations. These findings may provide an explanation of some experimental result intricacies related to the cell cycle.     

Design,analysis and fabrication of a linear permanent magnet synchronous machine

This paper deals with the design, analysis and fabrication of a 320 W, 5 m/s, 4-pole permanent-magnet-based linear synchronous machine (LPMSM). The design deals with conventional hand calculations followed by design fine-tuning and analysis using standard FEM packages. Fabrication of the machine has been also done at the works of a local small machine manufacturer after procurement of imported permanent magnets (PMs). The work presented here focuses on design and fabrication of LPMSM linor stampings with fixed dimensions and standard available PM tablets with a view to providing simple design guidelines. This prototype forms part of a variable speed linear motor drive that is being developed. The approach presented here might provide new ideas to those researchers who may not have the capability to bear cost of fabrication of lamination and PMs from scratch but would like to manufacture LPMSMs from available stampings and tablet PMs. Additionally, it may serve as a base document for the R&D personnel in this area.     

Radiation and cryogenic test results with a monolithic GaAs preamplifier in C-HFET technology

We report test results with a monolithic GaAs preamplifier fabricated in industrial C-HFET technology irradiated with a total dose of 10¹⁴ neutrons/cm² and 100 Mrad γ radiation and operated under cryogenic conditions. The measured gate current of the input transistor of a few nA increases by < 10% after irradiation. For a 330 μm input FET width, the equivalent noise charge (ENC) is typically 145 electrons per pF total input capacitance at a shaping time of 25 ns (bipolar) before irradiation and changes approximately by 10% after irradiation. Under cryogenic operation the corresponding input referred noise decreases by roughly a factor of two.     

Influence of microstructure of (α+β) Ti-6.2.4.6 alloy on high-cycle fatigue and tensile test behaviour

Tensile and gigacyclic fatigue behaviour of Ti–6Al–2Sn–4Zr–6Mo alloy were investigated as a function of lamellar primary α- and β-transformed microstructures. Three thermomechanical processes (TP1, TP2, TP3) were selected to produce different combinations of microstructural features on two slightly different compositions of the alloy (A and B). Ultrasonic fatigue tests were performed in air and liquid nitrogen at a frequency of 20 kHz ( R = −1, T  = 300 and 77 K), giving fatigue tests up to 10⁹ cycles. Microstructural features and the fracture initiation dependence on the primary α lamellar phase were observed by SEM and/or characterized by quantitative image analysis. It has been found that the microstructure of alloy B produced by TP1 represents a better compromise between resistance to initiation and resistance to microcrack growth. Quicker initiation occurs in coarser α-platelets (TP2, alloy B), and the continuous partially transformed β matrix appears to effectively decrease the tensile and HCF resistance. The bimodal structure (TP3, alloy B) has the best resistance at room temperature, but the presence of a coarse globular phase decreases this fatigue resistance at low temperature.