Designing high temperature superconductor magnets

Quasi-permanent magnets made of melt textured yttrium barium copper oxide (YBCO) superconductor can now trap multi-Tesla fields and retain that field semi-indefinitely. Because the fields so trapped achieve near zero creepage decay, they can be used as replacements of permanent magnets. This paper investigates the fields expected from these magnets, their prediction, and design expectations when they are incorporated into large scale arrays     

Magnetic field spatial Fourier analysis: A new opportunity for high resolution current localization

Magnetic microscopy has proven its usefulness throughout the years. It allows current localization with a certain degree of precision by using an inversion algorithm to invert the Biot–Savart law. The goal is to obtain the current distribution once the magnetic field is given. However, in order to obtain a stable solution, the magnetic data is severely low-pass filtered in the spatial Fourier domain, and some important information is lost. In this paper, the contribution given by the different spatial frequencies was studied: it was demonstrated how this information can be used to obtain additional information regarding the position of the currents. A comparative study between the theoretical approach and the application to the measurements is also shown.     

Current injection for field decay compensation in NMR spectrometer magnets

Current injection is a method to compensate for field drift in persistent nuclear magnetic resonance spectrometer magnets by the direct introduction of incremental current into the magnet through leads attached across a portion of the windings. An applied current ramp will distribute among the sections of the windings defined by the placement of the leads according to the inductance of the circuit. As a result, a current ramp trough leads placed across an inner coil will flow primarily in that coil. The field created by the injection current may be used to cancel a quasi-persistent field decay. The injection current required for the field decay compensation is determined as a function of magnet parameters and decay rate. The drift in field uniformity that results with current injection is found to be proportional to the field decay that is compensated, the drift and the decay being related by a quantity termed the dynamic uniformity; The field uniformity drift is quantified for an example magnet design; showing that the drift in field uniformity can be significant in the context of high resolution spectroscopy. Methods that facilitate shimming, such as gradient shimming, are identified as a natural compliment to current injection.     

一种新型高压Triple RESURF SOI LDMOS

提出了一种新型Triple RESURF SOI LDMOS结构,该结构有一个Ｐ型埋层。首先,耗尽层能够在Ｐ型埋层的上下同时扩展与Triple RESURF机理相同,使得漂移区浓度提高,导通电阻降低。其次,当漂移区浓度较高时,Ｐ型埋层起到了降低体内电场的作用,并能够提高漏端纵向电场使得其电场分布更加均匀从而耐压增加。Triple RESURF结构在SOI LDMOS中首次提出。在６微米厚的SOI层以及２微米厚的埋氧层中获得了耐压300V的Triple RESURF SOI LDMOS,其导通电阻从Double RESURF SOI LDMOS的17.2mΩ.cm2降低到13.8mΩ.cm2。当外延层厚度增加时, Triple RESURF结构的效果更加明显,在相同耐压下,相对于Double RESURF,该结构能够在400V和550V的SOI LDMOS中分别降低29%和38%的导通电阻。     

A new high voltage SOI LDMOS with triple RESURF structure

A novel triple RESURF（T-resurf） SOI LDMOS structure is proposed.This structure has a P-type buried layer.Firstly,the depletion layer can extend on both sides of the P-buried layer,serving as a triple RESURF and leading to a high drift doping and a low on-resistance.Secondly,at a high doping concentration of the drift region, the P-layer can reduce high bulk electric field in the drift region and enhance the vertical electric field at the drain side,which results in uniform bulk electric field distributions and an enhanced BV.The proposed structure is used in SOI devices for the first time.The T-resurf SOI LDMOS with BV = 315 V is obtained by simulation on a 6μm-thick SOI layer over a 2μm-thick buried oxide layer,and its R_sp is reduced from 16.5 to 13.8 mΩ·cm² in comparison with the double RESURF（D-resurf） SOI LDMOS.When the thickness of the SOI layer increases, T-resurf SOI LDMOS displays a more obvious effect on the enhancement of BV²/R_on.It reduces R_sp by 25%in 400 V SOI LDMOS and by 38%in 550 V SOI LDMOS compared with the D-resurf structure.     

A new high speed I/SUP 2/L structure

A new improved I/SUP 2/L structure is discussed which has been shown to operate at high speeds with large fan-out capabilities while retaining low power operation. The new `up-diffused' structure is fabricated in such a fashion that Schottky diodes can be readily incorporated. With the addition of Schottky clamps between the collector and base of the n-p-n switching transistor, gate delays as low as 2.5 ns have been achieved.     

A new field dependent mobility model for high frequency channel thermal noise of deep submicron RFCMOS

In this paper, a new field dependent effective mobility model including the drain-induced vertical field effect (DIVF) is presented to calculate the channel thermal noise of short channel MOSFETs operating at high frequencies. Based on the new channel thermal noise model, the simulated channel thermal noise spectral densities have been compared to the channel thermal noise directly extracted from noise measurements on devices fabricated using GLOBALFOUNDRIES’ 0.13 μm RFCMOS technology. The comparison has been done across different channel length, finger width and number of finger for different frequencies, gate biases and drain biases. Excellent agreement between simulated and extracted noise data has shown that the proposed model is scalable over different dimensions and operating conditions. The proposed model is simple and can be easily implemented in a circuit simulation environment.     

Application of a new high field quantum magneto-transport theory for polar semiconductors

High field quantum magnetotransport theory based on Feynman's Path Integral method has been derived. The first approximation gives implicite relations between applied field and drift velocity of electrons in magnetic field. Calculations for InSb at 77 K explain measured low field longitudinal magnetoresistance, low and high field transversal mobility data and warm electron coefficient for different magnetic field and predict high field longitudinal properties. The validity of our approximation in frame of the general quantum theory of transport phenomena is discussed. Extension of our calculations for intermediate and strong coupling cases, initiated by recent measurements on Silver Halides, is in progress.     

Evaluation new corner stress relief structure layout for high robust metallization

For a high robust metallization it is necessary to solve different problems related to migration mechanisms and thermo-mechanical stress in the material. Extended operating conditions and challenging assembling processes influence stress behaviour in chip corners. Typically the corner area of the chip is excluded for use. For higher stress load the forbidden area increases. But effort for demanding mission profiles of a product should not cumulative in increasing chip size. Simulation can help to a better understanding of mechanical stress in the chip corner and chip-package interaction.Corner stress relief structures lower the influence of high thermo-mechanical stress. A high functional corner stress relief structure allows a more efficient chip design. In this work of corner stress relief structure is presented and an evaluation structure is shown which allows to prove the effectiveness of the stress relief.     

A new structure for adaptive broad-band beamforming

The performance characteristics of adaptive array systems with derivative constraints have been investigated by several authors. As a result of the derivative constraints, the array beamwidth in the look direction could be made as broad as desired; however, this increased beamwidth was achieved at the price of reducing array gain. A structure is proposed for an adaptive broadband beamforming system in a manner that can produce a broader beamwidth in the look direction without any derivative constraints imposed on the adaptive processor. Compared to the conventional Frost beamformer with derivative constraints, the computer simulations illustrate the effectiveness of the proposed structure, which broadens the beamwidth in the look direction with only slight sacrifice of array gain     

一种新的隔离结构表面平坦化技术

为克服目前隔离结构平坦化技术在工艺控制、平坦化质量等方面存在的问题,提出了一种新的隔离结构表面平坦化工艺,即利用稠光刻胶做掩膜,结合反应离子刻蚀技术与湿法腐蚀技术,实现不同厚度隔离结构的平坦化.结果表明隔离结构边缘陡峭,硅表面平坦均匀.     

A process for high yield and high performance carbon nanotube field effect transistors

Carbon nanotube field effect transistors (CNTFETs) have been considered as one of the potential candidates for nanoelectronics beyond Si CMOS. However, it is not easy to have high performance CNTFETs with high yield currently. In this work, we proposed a local bottom-gate (LBG) CNTFETs combined with a novel device concept and optimized process technologies. High performance of CNTFET with low subthreshold swing of 139 mV/dec, high transconductance of 1.27 μS, and high I_on/I_off ratio of 10⁶ can be easily obtained with Ti source/drain contact after a post annealing process. Record high yield of 74% has been demonstrated. On the basis of the proposed process, lots of high performance CNTFETs can be obtained easily for advanced study on the electrical characteristics of CNTFETs in the future.     

Magnetic field characteristics of the low-beta quadrupole magnets, MQXA, for LHC

As a part of the collaboration program between CERN and KEK for the LHC, KEK has developed a superconducting low-beta quadrupole magnet, MQXA. KEK will supply 18 MQXA magnets, and 16 magnets will be installed in total in the four interaction regions. The cold tests of 13 magnets have been completed. Systematic field measurements were performed on these magnets, and these 13 magnets had satisfactory field quality for the requirement of beam optics. This paper describes the magnetic field behavior of the 13 MQXA magnets from the viewpoint of accelerator operation.     

A new high-voltage electric field instrument for studying sprites

The high-voltage (HV) electric field detector is a new high-voltage, high-impedance, double Langmuir probe instrument designed for stratospheric electric field measurements. In the Sprite Balloon Campaign 2002-2003, this HV instrument was used to measure electric fields between 100 and 200 V/m associated with lightning discharges, which is nearly an order of magnitude higher than previously reported above 30 km in altitude. This increased range is made possible by the availability of new low-leakage HV operational amplifiers. This is a critical instrument, since a large quasi-DC electric field associated with positive cloud-to-ground lightning is a primary component of most sprite generation mechanisms. The difficulty that exists when making electric field measurements in the high-resistance environment of the stratosphere is presented, and how this difficulty is remedied is described. The HV detector is compared to another electric field instrument, the low-voltage detector, used simultaneously on the Sprite Balloon Campaign to verify the accuracy of the HV probes. Finally, a large field perturbation (E/sub z//spl ap/-101 V/m and E/sub x//spl ap/79 V/m) measured by the HV detector during Flight 1, correlated with nearby +15-kA and +53-kA cloud-to-ground strokes, is presented.     

A new structure for a fingertip force sensor

Presents a structural design for force/torque fingertip sensors to sense planar forces. Not only can the resolution be increased by reducing the condition number of the calibration matrix, but also the accuracy can be enhanced by a precise and simple calibration method. Moreover, the theoretical analysis and design procedure of the proposed structure are included in this paper, and experimental results demonstrate the proposed design     

A new damascene structure for submicrometer interconnect wiring

A damascene structure for forming high-density interconnect wiring is presented. The structure results in improved open and short yields, lower sheet resistances, and comparable contact/via resistances, and it shows excellent filling of high-aspect-ratio long lines with high copper content. The key aspect of this technique is the ability to combine soft, low-resistance metal (Al alloy, Cu alloy, etc.) deposited by physical vapor deposition (PVD) with a hard metal (W) deposited by chemical vapor deposition (CVD) with high wear resistance. As a result a structure with a good polish stop, better alloying capability, and high yields can be fabricated while maintaining planarity at all levels. This structure is applied to a dense 512 K SRAM design with 0.5 μm minimum ground rules, resulting in improved yield of partially functional chips at second-level metal compared to the conventional reactive ion etching (RIE) structure     

A new technology for slow wave structure welding

The capability of heat conduction of the slow wave structure is one of the main obstacles to the development of the high-frequency high-power helix TWTs. A simple but reliable technological method for obtaining high heat conduction capability and low rf loss is suggested. The method of measurement of the heat conduction capability and the results of this measurement are also given.     

A NEW ADAPTIVE EQUALIZER STRUCTURE FOR NONLINEAR CHANNELS

Based on the analysis of nonlinear channel models,a new connectionist model ofadaptive equalizer is constructed.Comparing with the connectionist model using the Volterraseries to extend the input vector space,the number of weights with the new structure is reducedsignificantly.It is shown by simulations that the weight values of the new scheme converge to theoptimal values closely for non-minimum phase channels as well minimum phase channels,if thechannel noise is small enough.Testing results of the BER(Bit Error Rate)tell us that the newadaptive equalizer for nonlinear channels is superior to the conventional linear equalizers in theequalization performances.     

A new hypersphere support vector machine algorithm

The hypersphere support vector machine is a new algorithm in pattern recognition. By studying three kinds ofhypersphere support vector machines, it is found that their solutions are identical and the margin between two classes of samples is zero or is not unique. In this letter, a new kind ofhypersphere support vector machine is proposed. By introducing a parameter n（n〉1）, a unique solution of the margin can be obtained.Theoretical analysis and experimental results show that the proposed algorithm can achieve better generalization performance.     

R & D for accelerator magnets with react and wind high temperature superconductors

High temperature superconductors (HTS) have the potential to change the design and operation of future particle accelerators beginning with the design of high performance interaction regions. HTS offers two distinct advantages over conventional low temperature superconductors (LTS)-they retain a large fraction of their current carrying capacity (a) at high fields and (b) at elevated temperatures. The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has embarked on a new R & D program for developing technology needed for building accelerator magnets with HTS. We have adopted a "React and Wind" approach to deal with the challenges associated with the demanding requirements of the reaction process. We have developed several "conductor friendly" designs to deal with the challenges associated with the brittle nature of HTS. We have instituted a rapid turn around program to understand and to develop this new technology in an experimental fashion. Several R & D coils and magnets with HTS tapes and "Rutherford" cables have been built and tested. We have recently performed field quality measurements to investigate issues related to the persistent currents. In this paper, we report the results to date and plans and possibilities for the future.