Thin Gap Research Articles

Upgrade of the ATLAS muon system for the HL-LHC

Abstract The muon spectrometer of the ATLAS detector will be significantly upgraded during the Phase-II upgrade in Long Shutdown 3 in order to cope with the operational conditions at the High-Luminosity LHC in Run 4 and beyond. Most of the electronics for the Resistive Plate Chambers (RPC), Thin Gap Chambers (TGC), and Monitored Drift Tube (MDT) chambers will be replaced to make them compatible with the higher trigger rates and longer latencies necessary for the new level-0 trigger. The MDT chambers will be integrated into the level-0 trigger in order to sharpen the momentum threshold. Additional RPC chambers will be installed in the inner barrel layer to increase the acceptance and robustness of the trigger. Some of the MDT chambers in the inner barrel layer will be replaced with new small-diameter MDTs. New TGC triplet chambers in the barrel–endcap transition region will replace the current TGC doublets to suppress the high trigger rate from random coincidences in this region. The power system for the RPC, TGC, and MDT chambers and electronics will need to be replaced due to component obsolescence, aging, and radiation damage. A high- η tagger is under consideration to extend the angular acceptance for muon identification. The Phase-II upgrade concludes the process of adapting the muon spectrometer to the ever increasing performance of the LHC, which started with the Phase-I upgrade New Small Wheel project that will replace the Cathode Strip Chambers and the MDT chambers of the innermost endcap wheels by Micromegas and small-strip TGCs.

Simulated and experimental analysis of electrodeposited β' Brass composition with DLA morphology

Electrodeposition of two ions like Copper and Zinc in the alloy of β' Brass is done in thin gap 2D geometry. The growth follows a Diffusion Limited Aggregation (DLA) like morphology. It is observed that the ratio of the two ions deposited remains almost constant with the distances from cathode. This ratio also depends on the composition of the cathodes. This has been shown experimentally and using a unique two-ion simulation model developed by us. The compositional analysis by EDX of the electrodeposited layers at different separations of 0.5 cm, 1.0 cm and 1.5 cm from the negative electrode shows a uniform ratio of 2.3087 for the two ions of copper and zinc. A two-ion simulation model made by us with different masses for the ions and for the same composition of cathode shows a uniform ratio of 2.3133 for the two ions systems and therefore, support the experimental observation to a high degree of accuracy. The results obtained have been explained theoretically.

Electric Field Deformation of Protein-Coated Droplets in Thin Channels.

High-strength droplet interfaces are attractive for many applications, specifically in cases where droplets are channeled through fluidic devices and manipulated by electromagnetic fields. Using models and experiments, we study the deformation of droplets and capsules with protein interfaces in an electric field in thin and wide electrode gaps. Proteins are chosen from candidates expected to display qualitatively different interfacial interactions and strengths: a globular protein (bovine serum albumin), a reversible cross-linking peptide (AFD4), and a hydrophobin (cerato ulmin). Dilute protein additives can lead to over 1 order of magnitude stronger oil-water interfaces than those stabilized by small surfactants. We develop small deformation models to evaluate a protein membrane's interfacial elasticity, notably accounting for the electric field perturbation encountered in a gap and a careful treatment of a generalized elastic interface with both surface tension and interfacial elasticity. Results indicate that globular proteins, which typically have comparable surface tension and interfacial elasticity, can be modeled well by this generalized elastic interface. We further find that when in a gap, droplets and capsules migrate toward one electrode, deform asymmetrically, exhibit polar spreading on the electrode, and predictably stretch more than in the infinite gap scenario at constant field strength.

The evolution of morphology during the mechanical ‘plasticisation’ of unfilled vulcanisates of nitrile rubbers*

Optical microscopy was used to investigate features of morphological transformation during the mechanical degradation of unfilled vulcanisates of nitrile butadiene rubbers in a thin mill roll gap and subsequent thermal treatment – revulcanisation without the addition of any components into the degradate. An analytical complex based on a Leica DM-2500 optical microscope, a Leica DFC-420C high-resolution digital colour camera, and a specialised computer desk was used. The influence of the milling time in the 0–40 min range on the morphological parameters and the nature of the fine structure of plasticised specimens was studied. The mechanisms of degradation and structure formation during the plasticisation of vulcanisates were analysed. The formation of an additional three-dimensional skeleton in ‘secondary’ vulcanisates and the build-up of this process with increase in the treatment time of the degradate were found, which may lead to an increase in the mechanical properties to a level exceeding that of the initial vulcanisate. However, increase in compositional inhomogeneity may have an adverse effect on oil resistance.

Development of a capacitive slip sensor using internal air gap

Accurate recognition of an object plays an important role in ensuring safe grasping of robotic hand operation. For this reason, usage of proper tactile sensors are essential for robots to recognize objects. In this paper, we present a wide-range functional tactile sensor that can be used for slippage information collector as well as for a protective cover. This sensor has a thin air gap between the polymer layers, which is to be deformed upon a slip motion. When slip occurs on the surface, relative displacement occurs between the object and the sensor surface. This displacement causes deformation of the sensor, which can detect the slippage by measuring the changing capacitance. Since the slip detection algorithm only exploits the change in capacitance, no complicated signal processing such as frequency analysis is required. Therefore, no large data processing is required to detect the slip, and the time delay can also be minimized. These advantages can greatly help the robot hand to react instantly when preventing the object from slip.

3D simulation of hexagonal current pattern formation in a dc-driven gas discharge gap with a semiconductor cathode

The formation of hexagonal current pattern in a dc-driven thin planar gas discharge gap with a semiconductor cathode is studied on the basis of a 3D drift-diffusion discharge model. The model includes continuity equations for electron and ion densities, the electrostatic equation for electric field and heat conduction equation for gas temperature. Solving these equations by the time-relaxation method, we investigate the genesis of ordered current pattern and its subsequent rearrangement into the hexagonal pattern, starting from initial homogeneous discharge state without any initial perturbations. For the case of the dc discharge with a semiconductor cathode and cryogenic conditions, the 3D calculation has been performed for the first time. The resulting current pattern is in agreement with experiment. The results of the simulation confirm that the discharge instability and the patterns formation are due to an ionization-overheating (thermal) mechanism, as was proposed before in [Raizer Yu P and Mokrov M S 2010 J. Phys. D: Appl. Phys. 43 225204] on the basis of approximate theory.

Separation of particles by size from a suspension using the motion of a confined bubble

When confined in a liquid-filled circular cylinder, a long air bubble moves slightly faster than the bulk liquid as a small fraction of the liquid leaks through a very thin annular gap between the bubble and the internal wall of the cylinder. At low velocities, the thickness of this lubricating film formed around the bubble is set only by the liquid properties and the translational speed of the bubble and thus can be tuned in a simple fashion. Here, we use this setting to filter, based on size, micron-size particles that are originally dispersed in a suspension. Furthermore, we apply this process for separation of particles from a polydisperse solution. The bubble interface is free of particles initially, and particles of different sizes can enter the liquid film region. Particle separation occurs when the thickness of the lubricating liquid film falls between the diameters of the two different particles. While large particles will be collected at the bubble surface, smaller particles can leak through the thin film and reach the fluid region behind the bubble. As a result, the film thickness can be fine-tuned by simply adjusting the speed of a translating confined bubble, so as to achieve separation of particles by size based on the relative particle diameter compared to the film thickness.

Thermionic emission via a nanofluid for direct electrification from low-grade heat energy

Thermionic emission is the thermally induced flow of charge carriers over a surface work function or across an interface potential barrier. Historically this effect is used for energy generation by employing a thin vacuum or (more often) plasma gap between a hot cathode and a colder anode, across which charges are transferred. The magnitude of the charge flow increases with the cathode temperature, however only becomes significant above ∼ 1000 K thus limiting practical uses of thermionic energy generators (TiEG). Here we show that infilling a nanofluid inside the inter-electrode gap raises thermionic emission rate enormously, such that considerable currents can be generated even at room temperature. The nanofluid TiEG's output current density surpassed that of conventional TiEG, predicted by the fundamental Richardson-Dushman law, by factors of 40–60 orders of magnitude across the measured temperature range. This implies an enhanced thermionic emission via the nanofluid other than the conventional TiE, and may open up a novel pathway for thermally induced electrification.

Influence of geometric parameters on flow and temperature characteristics in partitioned thermal convection

An unprecedented heat-transport enhancement of the Rayleigh-Benard convection can be leaded by inserting vertical partitions with thin gaps left open between the partition walls and cooling/heating plates. The more geometric parameters appeared in the partitioned thermal convection. The two-dimensional direct numerical simulations (DNS) were performed for partitioned thermal convection with the various aspect ratio Γ , height of gap d and width of channel b , and the influence of geometric parameters on the flow characteristics is discussed. The flow characteristics are mainly reflected by the average velocity of the gaps and the average velocity of the channels, and the temperature distribution is mainly reflected by TD number that characterizing the magnitude of temperature in the channels. The results show that flow characteristics and temperature distribution of different systems are basically the same when the local height of gap d and width of channel b are the same, and the aspect ratio of the whole system has little effect. By analyzing a great deal of results of numerical simulation, we can estimate that d is the critical geometric parameter that controls the flow and temperature characteristics in the case of b ≥4 d at Ra =108 and Pr =5.3 for the different height of gap d and width of channel b . In addition, the flow in the gaps is two-dimensional Poiseuille flow, and it decouples from the temperature distribution but has function as a transporter of the horizontal heat flow. The height of gap d has little influence on the velocity in the gaps, but affects the flow and temperature characteristics of the whole system.

Diffusion-advection within dynamic biological gaps driven by structural motion.

To study the significance of advection in the transport of solutes, or particles, within thin biological gaps (channels), we examine theoretically the process driven by stochastic fluid flow caused by random thermal structural motion, and we compare it with transport via diffusion. The model geometry chosen resembles the synaptic cleft; this choice is motivated by the cleft's readily modeled structure, which allows for well-defined mechanical and physical features that control the advection process. Our analysis defines a Péclet-like number, A^{D}, that quantifies the ratio of time scales of advection versus diffusion. Another parameter, A^{M}, is also defined by the analysis that quantifies the full potential extent of advection in the absence of diffusion. These parameters provide a clear and compact description of the interplay among the well-defined structural, geometric, and physical properties vis-a[over ̀]-vis the advection versus diffusion process. For example, it is found that A^{D}∼1/R^{2}, where R is the cleft diameter and hence diffusion distance. This curious, and perhaps unexpected, result follows from the dependence of structural motion that drives fluid flow on R. A^{M}, on the other hand, is directly related (essentially proportional to) the energetic input into structural motion, and thereby to fluid flow, as well as to the mechanical stiffness of the cleftlike structure. Our model analysis thus provides unambiguous insight into the prospect of competition of advection versus diffusion within biological gaplike structures. The importance of the random, versus a regular, nature of structural motion and of the resulting transient nature of advection under random motion is made clear in our analysis. Further, by quantifying the effects of geometric and physical properties on the competition between advection and diffusion, our results clearly demonstrate the important role that metabolic energy (ATP) plays in this competitive process.

Simulation method for precision bonding structure with micron scale adhesive layer

In the manufacturing process of precision instruments, many parts are connected by adhesive. Because of the high manufacturing accuracy of precision instrument, the design value of the bonding gap is generally in the scale of microns. This thin gap in the instrument may lead to nonlinear displacement and deformation of instrument under the condition of multi physical field when the precision instrument is working, thus affecting the accuracy and stability of instrument. In this paper, a simulation method for bonding structure with micron scale adhesive layer is established. Through a case of simplified model and a case of mesh method of a precision instrument adhesive structure, the finite element analysis is carried out. The basic principle of geometric model simplification and mesh method in the simulation is obtained. In order to ensure the accuracy of the three-dimensional stress analysis, the adhesive layer with a local thickness which is less than 1/10 of the average thickness is simplified as a hole. The length- width ratio of the meshes should be controlled about 1:10. For stress analysis, second order hexahedron element should be used and the element angle should between 10 degrees to 170 degrees. Under these conditions, the simulation of the bonding structure with micron scale adhesive layer can be carried out with high accuracy and high efficiency.

Efficiency Comparison between Conventional and Modern Port Operation System for Small-Scale Dry Bulk Cargo

Since the launching of Sea Toll Road Program in 2015, the improvement in ports’ operation systems has become Indonesia’s foremost necessity. This improvement commonly leads to equipment modernization, while realistically, modern equipment does not always amount to a productive performance, especially in the context of small-scale ports. Instead, it is prone to creating wasteful capital and maintenance cost as well as making the planning time ineffective. This study compares two options of port operation systems in a small port, which is conventional and technologically-advanced method for dry bulk cargo. It results in thin gaps between each option’s financial assessment variables, which are Internal Rate of Return, Benefit/Cost Ratio and Payback Period, regardless of a stark difference between each option’s equipment cost. This study concludes that with the right approach, the conventional operation system is still the most efficient option compared to its contemporary opposite.

Fixation of the stressed state of glass plates by coating them with thin films using a plasma focus installation

Elastic deformation in transparent mediums is usually studied by the photoelasticity method. For opaque mediums the method of film coating and strain gauge method are used. After the external load was removed, the interference pattern corresponding to elastic deformation of the material disappears. It is found that the elastic deformation state of the thin glass plate under the action of concentrated load can be fixed during the deposition of a thin metal film. Deposition of thin copper films was carried out by passing of plasma through the copper tube installed inside the Plasma Focus installation. After removing of the load, interference pattern on the glass plates was observed in the form of Newton’s rings and isogers in non-monochromatic light on the CCD scanners which uses uorescent lamps with cold cathode. It is supposed that the copper film fixes the relief of the surface of the glass plate at the time of deformation and saves it when the load is removed. In the case of a concentrated load, this relief has the shape of a thin lens of large radius. For this reason, the interference of coherent light rays in a thin air gap between the glass of the scanners atbed and the lens surface has the shape of Newton's rings. In this case, when scanning the back side of the plate, isogyres are observed. The presented method can be used in the analysis of the mechanical stress in a various optical elements.

The Competition between the Noise and Shear Motion Sensitivity of Cochlear Inner Hair Cell Stereocilia

Acoustical excitation of the organ of Corti induces radial fluid flow in the subtectorial space (STS) that excites the hair bundles (HBs) of the sensory inner hair cell of the mammalian cochlea. The inner hair cell HBs are bathed in endolymphatic fluid filling a thin gap in the STS between the tectorial membrane and the reticular lamina. According to the fluctuation dissipation theorem, the fluid viscosity gives rise to mechanical fluctuations that are transduced into current noise. Conversely, the stochastic fluctuations of the mechanically gated channels of the HBs also induce dissipation. We develop an analytic model of the STS complex in a cross section of the gerbil organ of Corti. We predict that the dominant noise at the apex is due to the channel stochasticity whereas viscous effects dominate at the base. The net root mean square fluctuation of the HB motion is estimated to be at least 1.18 nm at the base and 2.72 nm at the apex. By varying the HB height for a fixed STS gap, we find that taller HBs are better sensors with lower thresholds. An integrated active HB model is shown to reduce the hydrodynamic resistance through a cycle-by-cycle power addition through adaptation, reducing the thresholds of hearing, hinting at one potential role for HB activity in mammalian hearing. We determine that a Couette flow approximation in the STS underestimates the dissipation and that modeling the entire STS complex is necessary to correctly predict the low-frequency dissipation in the cochlea. Finally, the difference in the noise budget at the base and the apex of the cochlea indicate that a sensing modality other than the shear motion of the TM that may be used to achieve low-noise acoustic sensing at the apex.

Experimental Characterization of Meso-Micro Fractals from Nanoparticle Seeded Resin in Lifting Plate Hele-Shaw Cell

Various processes are developed to fabricate meso and micro size fractal structures for wide variety of engineering applications. Various types of fluid flows are studied and are deployed to develop meso and micro fractal structures. Lift Plate Hele-Shaw fluid flow also termed as Saffman-Taylor instability is one of the fluid phenomenon’s which can be easily used to fabricate such structures. In this process, fractals are formed by capturing the fluid droplet between thin gaps of two flat parallel plates and moving the upper plate in controlled manner. The formation of the fractal depends on process parameters; viz velocity of plate, fluid property and gap between the plates. This paper presents the exhaustive characterization of fluid composed of photopolymer seeded with the nanopowder in lifting plate Hele-Shaw cell. The prepared resin is mixture of monomer Hexanediol Diacrylate (HDDA) and photoinitiator Benzoyl Ethyl Ether (BEE) seeded with ceramic nanopowder. The fractal growth is observed from the prepared resin under lifting plate Hele Shaw cell through designed of experiments. The parameters; fluid separation velocity and gap between the plates are varied through developed system and effect of viscosity is observed by varying the loading of the ceramic nanopowder. The exhaustive characterization of the process has presented the effect of parameters and its interactions on the formation of the fractal. Further the fractal growth is presented in the dimensionless manner for its generalization. The experimental characterization has given a generalised methodology for the formation of controlled fractals or to mimic various meso and micro fractals available in the nature.

Pattern transition from dense branching morphology to fractal for copper and β′ brass electrodeposition in thin gap geometry

Copper and β′ brass are electrodeposited in thin gap geometry and a clear transition from dense branching to fractal like pattern is observed with the variation of electric potential and concentration. The transition electric potential is 6V – 5V for copper and 25V for β′ brass. The explanation of the pattern transition is done first using the Laplacian growth as in the Di-electric Breakdown Model (DBM) and then on the basis of ion dynamics in terms of viscosity, ionic mobility, drift and thermal velocity. The fractal growth is more likely at higher electric potential as the electric field dominates and more likely to be dense branched at lower electric field when thermal motion dominates. This work inspires for further studies on modification of our model for the two ions electrodeposition and their compositional variation with different deposition parameters.

Performance of Pad Front-End Board for Small-Strip Thin Gap Chamber With Cosmic Ray Muons

We report on the characterization of pad front-end board (pFEB) for small-strip thin gap chamber (sTGC) prototype. The pFEB is based on field programmable gate array (FPGA) and application-specific integrated circuit. It has been built to verify the capabilities of the sTGC detector for the ATLAS Phase-I new small wheel upgrade. The pFEB consists of three VMM2 front-end chips, two Kintex-7 FPGAs used to buffer the VMM2 data, a gigabit ethernet transceiver (GET), and all the required connectors. The VMM2, designed at Brookhaven National Laboratory, is composed of 64 linear front-end channels. Each channel integrates a charge sensitive amplifier, a shaper, a stable band-gap referenced baseline, several analog-to-digital converters, and other functions. The GET works at physical layer of the network. The mini-serial attached SCSI connector accepts three external signals (40-MHz clock, reset, and trigger), which are used for synchronization of several pFEBs. In addition, the pFEB can work in the case of self-trigger mode and external trigger mode. The specific characteristics and implementations are described in detail. Also, the performance of this new type of sTGC detector has been studied with cosmic ray muons.

Performance studies of resistive Micromegas chambers for the upgrade of the ATLAS Muon Spectrometer

The ATLAS collaboration at LHC has endorsed the resistive Micromegas technology (MM), along with the small-strip Thin Gap Chambers (sTGC), for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called New Small Wheel (NSW) project. The NSW requires fully efficient MM chambers, up to a particle rate of ∼ 15 kHz/cm2, with spatial resolution better than 100 μm independent of the track incidence angle and the magnetic field (B ≤ 0.3 T). Along with the precise tracking the MM should be able to provide a trigger signal, complementary to the sTGC, thus a decent timing resolution is required. Several tests have been performed on small (10 × 10 cm2) MM chambers using medium (10 GeV/c) and high (150 GeV/c) momentum hadron beams at CERN. Results on the efficiency and position resolution measured during these tests are presented demonstrating the excellent characteristics of the MM that fulfil the NSW requirements. Exploiting the ability of the MM to work as a Time Projection Chamber a novel method, called the μTPC, has been developed for the case of inclined tracks, allowing for a precise segment reconstruction using a single detection plane. A detailed description of the method along with thorough studies towards refining the method’s performance are shown. Finally, during 2014 the first MM quadruplet (MMSW) following the NSW design scheme, comprising four detection planes in a stereo readout configuration, has been realised at CERN. Test-beam results of this prototype are discussed and compared to theoretical expectations.

Miniature high gain slot-fed rectangular dielectric resonator antenna for IoT RF energy harvesting

Radio-frequency (RF) energy harvesting is a promising candidate for alternative power source that can reduce the dependencies on batteries. However, its power density is very low which makes it crucial to have a high gain antenna to increase the power received by the system. This study presents the design of miniature high gain dielectric resonator antenna for RF energy harvesting application with high figure of merit to increase the power received. Numerical approximation is used to assist the antenna design and modelling. The design focused on three parameters which are the width, length, and height of the dielectric resonator. The performance, electric field density, and the radiation patterns of the dielectric resonator antenna have been observed by varying the design parameters. The effect of air gap to the performance is investigated and it is found that 8.11–13% gain improvement and up to 36% improvement in impedance matching is achieved through incorporating thin air gap between the dielectric resonator. Soda-lime glass with relative permittivity 7.75 is used which allows miniaturization and transparency. Experimental results show reasonable agreement to the simulations. The work shows highest antenna gain with smallest size with high FOM at 5 GHz ISM band compared to previous works.

Fast-response liquid crystal phase modulators for augmented reality displays

We report three new liquid crystal mixtures optimized for the phase modulator of an augmented reality display. The mixtures exhibit a relatively high birefringence (Δn) yet low viscosity, modest dielectric anisotropy (Δe), and acceptable resistivity and UV stability. High Δn enables a thin cell gap (d≈1.7 μm) for achieving 2π phase change with a reflective Liquid-Crystal-on-Silicon (LCoS) device and ~2 ms average phase-to-phase response time at 40°C. The modest Δe helps lower the operation voltage to 5V. To improve the response time of a full-color LCoS, we propose a new driving method by shifting the operation voltage away from the threshold. We also applied such a high Δn LC mixture to LCoS based amplitude modulators and achieved submillisecond response time. Widespread applications of these materials for the emerging augmented reality displays are foreseeable.