Industrialisation of the insulation vacuum barrier for the large hadron collider (LHC) magnet cryostats

The insulation vacuum (<10⁻⁴ Pa) of the large hadron collider magnet cryostats, thermally protecting the superconducting magnets which operate at 1.9 K in superfluid helium, is divided in to 214 m long segments separated by means of insulation vacuum barriers.The insulation vacuum barrier is a leak-tight stainless steel welded structure, composed of two concentric corrugated cylinders and one internal bellows linked together by a 6 mm thick central plate. As the vacuum barrier mechanically links the cryostat vacuum vessel operating at ambient temperature and the 1.9 K superconducting magnets, it is designed to have minimum heat conductivity. Conduction heat in-leak is intercepted at 65 K by a high-purity copper ring brazed onto the stainless steel central plate and thermally linked to a cryogenic line by a copper-aluminium soldering. The thermal performance has been experimentally validated by cryogenic testing.This paper presents the results obtained after industrialisation, manufacture and testing of prototypes and series units. Qualification of leak-tight welds in thin-sheet stainless steel (thickness 0.15-1.3 mm) has been carried out. Ultrasonic testing is performed on all brazing and soldering. Helium leak testing is performed, using dedicated tooling, to ensure a leak-tightness to a rate better than 10⁻⁹ Pa m³ s⁻¹.     

A study on the applicability of solid state, real-time dosimeters to the CMS experiment at the large hadron collider

MOSFET dosimeters have been exposed to a large range of radiation fields: 192 MeV positive pions, 500 MeV electrons, 23 GeV protons and a wide energy-spectrum of neutrons. This is the first time that pion dosimetry with MOSFETs is presented. The response curves of the devices are given, together with an evaluation of their dynamic range, showing that these dosimeters can be successfully used to monitor radiation fields up to very high doses and fluences. In the 500 MeV electron beam, an irradiation of p⁺/n/n⁺ diodes together with MOSFETs was also performed. The results of this irradiation show that both types of dosimeters can be used in CMS to monitor in real time the radiation environment.     

Beam loss by single coulomb scattering in collider rings

The ultimate cause of beam loss in a collider ring is given by particles scattered outside the ring acceptance by single Coulomb scattering. Even though small, this effect is not negligible, above all in super-cooled low energy machines, with a vertical betatron function which takes up a minimum value, at the interaction region, comparable to the average performed around the ring.     

A large liquid argon photon/hadron calorimeter for FNAL

This paper describes a new liguid argon photon/hadron detector currently under construction for Experiment E706 at the Fermi National Accelerator Laboratory.     

The physics of very large landslides

Summary In 1881 the alpine village of Elm, Switzerland, was nearly wiped out by an enormous rockslide that flowed 2 km down the valley. This disaster made geologists and engineers aware that large masses of rock debris may sometimes behave like a fluid with a low internal resistance to deformation. Since 1881 many other instances of fluidized rockslides have been found, both contemporary and prehistoric. The discovery of such rockslide deposits on Mars and the Moon make it clear that neither air nor water play an essential role in the fluidization process, although they may enhance it.The fluid-like flow of large rock debris masses, evenin vacuo, may be explained by the presence of strong acoustic waves or noise within the slide mass. Acoustic waves, generated by the shear flow, diffuse though the strongly-scattering rock debris. Because rocks in the slide remain largely in contact during flow, these waves may transmit large pressure fluctuations elastically without simultaneously transporting large amounts of energy. The pressure fluctuations allow the dry rock debris to yield under a differential stress much smaller than the average overburden. The overburden is briefly relieved by any unusually large pressure fluctuation and a local slippage may take place in the debris mass. If such local slippages are frequent enough, the debris may creep forward under an anomalously small mean shear stress.The theoretical prediction, that rock debris may be fluidized by strong acoustic waves, was tested experimentally in sand subjected to strong ultrasonic shaking. Preliminary observations are consistent with the theory. As predicted, the flow is highly non-Newtonian for weak acoustic fields (strain rate is proportional to the eighth power of the stress), but approaches Newtonian flow as the acoustic intensity increases.Rockslides involve so much strain that the acoustic energy produced during the initial fall cannot last long enough to keep the mass fluidized during the last stages of motion. Acoustic fluidization can account for the mobility of large masses of rock debris only if the acoustic energy is regenerated during flow. It is plausible that shear flows may generate large amounts of acoustic energy and thus regenerate the field, but the efficiency of the process is still uncertain. Theoretical studies suggest that regeneration is adequate to acount for the principal features of large rockslides, but more experimental work is required.Despite these uncertainties, fluidization by sound is the only theory that accounts for the major features of the large rockslides orSturzstrom that have occured on earth and the other planets of our solar system. This theory also accounts for the collapse of large impact craters, the formation of central peaks, and the formation of the multiple ring systems that characterize impact basins.     

An equation solver of very large capacity

A very simple equation solver of very large capacity is developed. The method described here does not require a very large in-core memory; however, a fast random access device like a magnetic disk drive is required.     

Copper metallization for current very large scale integration

As silicon technology scaling progresses to the 32 nm node or even further, the design on the propagation of electromagnetic signals becomes increasingly appealing due to their unyielding constraints on interconnect delay. Because of its high conductivity and electromigration resistance, Cu is now the interconnect materials in current VLSI. To ensure the signal propagation via the Cu interconnects upon the increasingly reduction in the interconnect width, related issues on Cu interconnects, such as electron scattering at surfaces and grain boundaries, electromigration failure and surface oxidation, still need to be further understood and addressed. Besides this, the performance of low-k dielectrics and reliable barrier structures, which are also much important among the device parts, are required to be further improved to minimize the signal delay and to prevent penetration of different materials, respectively. On the basis of the paper published at Recent Patent on Nanotechnology 2007; 1: 193-209, this review will focus on recent patents and some studies on Cu metallization including Cu interconnect wires, low-k dielectrics and related barrier materials as well as manufacturing techniques in VLSI, which are one of the most essential concerns in microelectronic industry and decide further development of VLSI. This review will benefit for the design of the Cu metallization in the current VLSI.     

环形正负电子对撞机大型探测器超导磁体虹吸实验初步研究

对环形正负电子对撞机大型探测器超导磁体拟采用的低温虹吸实验进行了研究,通过液氮虹吸实验发现了倾斜角度对虹吸换热效果的影响。热虹吸管在15°时换热效果最佳(最大换热温差在4 K内),倾角增大,热虹吸管冷热端温差逐渐增大。对液氦虹吸实验装置进行设计和搭建,并进行了初步探索,研究发现蒸发侧热负荷为0.5 W时,管路换热温差为1.2 K,且装置本体漏热为0.5 W。     

超大型浮式储油船的水弹性响应预报

海上石油储备基地的主要结构—超大型浮式储油船属于超大型浮式结构物（VLFS）,对其水弹性响应分析是研究设计中的一个重要环节。采用正弦振型函数,将结构运动产生的辐射势及水弹性响应根据模态形式进行展开叠加,然后通过对边界积分方程应用三维势流理论中的格林函数法,其中由于结构的对称性,只建立储油船的1/4数值模型,求出速度势及流体压力,最后将其代入结构水弹性运动方程。探讨了广义水动力参数随水深和相对波长的变化规律,进一步计算不同水深及波长时储油船的水弹性响应、底板变形及其内部弯矩,为今后的研究提供理论依据和方法。     

Dependability analysis of a very large volume neutrino telescope

This work considers a first order approximation to the dependability analysis of complex large scale installations. The dependability criterion used here is quantitative unavailability, and an appropriate unavailability model is presented. The model assumes that the system is symmetrical, has various levels of hierarchy, and components found in the same level are similar and function independently.The application example comes from very large volume neutrino telescopes installed under water or ice, consisting of several thousands of optical modules. The readout architecture of the detector has several levels of multiplexing including optical detection towers, branches and tower sectors. The paper presents results for various alternative detector layouts and distances of the detector from the onshore facilities. It also develops dependability requirements for major components and/or subsystems consistent with an overall system performance target. The results depict the dependence of the system unavailability on the number of optical modules and the alternative deep sea infrastructure configurations for transferring the measured signals.     

超大Fibonacci数的快速迭代算法

Fibonacci序列在信息隐藏、密码学等领域具有广泛的应用,现提出一种能计算超大Fibonacci整数的快速算法,最大可以精确地计算第30万个Fibonacci整数,可以完全满足信息隐藏和密码学领域实时计算的需要.     

Prediction of very large values of magnetoresistance in a graphene nanoribbon device

Graphene has emerged as a versatile material with outstanding electronic properties that could prove useful in many device applications. Recently, the demonstration of spin injection into graphene and the observation of long spin relaxation times and lengths have suggested that graphene could play a role in 'spintronic' devices that manipulate electron spin rather than charge. In particular it has been found that zigzag graphene nanoribbons have magnetic (or spin) states at their edges, and that these states can be either antiparallel or parallel. Here we report the results of first-principles simulations that predict that spin-valve devices based on graphene nanoribbons will exhibit magnetoresistance values that are thousands of times higher than previously reported experimental values. These remarkable values can be linked to the unique symmetry of the band structure in the nanoribbons. We also show that it is possible to manipulate the band structure of the nanoribbons to generate highly spin-polarized currents.     

Design and operation of a very large ring laser gyroscope

The design and initial operation of a vertical square He-Ne ring laser G0 with a perimeter of 14 m is discussed. This builds on earlier demonstrations of the feasibility of large ring lasers (perimeter approximately 4 m) for single-mode gyroscope operation and with lesser pulling than navigation gyroscopes. With servoing of the rf excitation to yield single-mode operation, G0 gave a quality factor 1 x 10(12) and a Sagnac line with a frequency of 287.8 +/- 1.0 Hz induced by Earth rotation Omega(E). This has confirmed some vital questions over the feasibility of very large gyroscopes for geodetic measurements at the level of 10(-9) Omega(E).     

The effects and consequences of very large explosive volcanic eruptions

Every now and again Earth experiences tremendous explosive volcanic eruptions, considerably bigger than the largest witnessed in historic times. Those yielding more than 450km3 of magma have been called super-eruptions. The record of such eruptions is incomplete; the most recent known example occurred 26000 years ago. It is more likely that the Earth will next experience a super-eruption than an impact from a large meteorite greater than 1km in diameter. Depending on where the volcano is located, the effects will be felt globally or at least by a whole hemisphere. Large areas will be devastated by pyroclastic flow deposits, and the more widely dispersed ash falls will be laid down over continent-sized areas. The most widespread effects will be derived from volcanic gases, sulphur gases being particularly important. This gas is converted into sulphuric acid aerosols in the stratosphere and layers of aerosol can cover the global atmosphere within a few weeks to months. These remain for several years and affect atmospheric circulation causing surface temperature to fall in many regions. Effects include temporary reductions in light levels and severe and unseasonable weather (including cool summers and colder-than-normal winters). Some aspects of the understanding and prediction of super-eruptions are problematic because they are well outside modern experience. Our global society is now very different to that affected by past, modest-sized volcanic activity and is highly vulnerable to catastrophic damage of infrastructure by natural disasters. Major disruption of services that society depends upon can be expected for periods of months to, perhaps, years after the next very large explosive eruption and the cost to global financial markets will be high and sustained.     

Solid state microdosimetry in hadron therapy

A report of recent developments in silicon microdosimetry is presented. SOI based microdosemeters have shown promise as a viable alternative to traditional tissue-equivalent proportional counters. The application of these silicon microdosemeters to such radiation therapy modalities as boron neutron capture therapy (BNCT), boron neutron capture synovectomy (BNCS), proton therapy (PT), and fast neutron therapy (FNT) has been performed. Several shortcomings of the current silicon microdosemeter were identified and will be taken into account in the design of a second-generation device.     

Novel transmit aperture for very large depth of focus in medical ultrasound B-scan

Obtaining high quality ultrasound images at high frame rates has great medical importance, especially in applications in which tissue motion is significant (e.g., the beating heart). Dynamic focus and dynamic aperture can improve image quality significantly, and they have been implemented on the receive beam in state-of-the-art medical ultrasound systems. However, implementing dynamic focus and dynamic aperture on the transmit beam compromises frame rate. We introduce a novel sinc squared-argument transmit aperture that is obtained by coherently integrating the quadratic phase change over a continuum of focal points. Thus uniform sensitivity and uniform point spread function can be achieved over a very large depth without reducing the frame rate. Numerical simulations validate our theoretical analysis and demonstrate significant promises of the new technique.     

Natural convection from a vertical cylinder at very large Prandtl numbers

Summary The natural convection from a vertical cylinder, is determined in the limiting case of very large Prandtl number, the Grashof number remaining finite.