Excessive Beam Research Articles

Whole-Cell Analysis of Low-Density Lipoprotein Uptake by Macrophages Using STEM Tomography

Nanoparticles of heavy materials such as gold can be used as markers in quantitative electron microscopic studies of protein distributions in cells with nanometer spatial resolution. Studying nanoparticles within the context of cells is also relevant for nanotoxicological research. Here, we report a method to quantify the locations and the number of nanoparticles, and of clusters of nanoparticles inside whole eukaryotic cells in three dimensions using scanning transmission electron microscopy (STEM) tomography. Whole-mount fixed cellular samples were prepared, avoiding sectioning or slicing. The level of membrane staining was kept much lower than is common practice in transmission electron microscopy (TEM), such that the nanoparticles could be detected throughout the entire cellular thickness. Tilt-series were recorded with a limited tilt-range of 80° thereby preventing excessive beam broadening occurring at higher tilt angles. The 3D locations of the nanoparticles were nevertheless determined with high precision using computation. The obtained information differed from that obtained with conventional TEM tomography data since the nanoparticles were highlighted while only faint contrast was obtained on the cellular material. Similar as in fluorescence microscopy, a particular set of labels can be studied. This method was applied to study the fate of sequentially up-taken low-density lipoprotein (LDL) conjugated to gold nanoparticles in macrophages. Analysis of a 3D reconstruction revealed that newly up-taken LDL-gold was delivered to lysosomes containing previously up-taken LDL-gold thereby forming onion-like clusters.

Developing a New Design for Adaptive Tuned Dynamic Vibration Absorber (ATDVA) Based on Smart Slider-Crank Mechanism to Control of Undesirable Vibrations

Nowadays, in every industrial field, one of the most important key item to be research is to eliminate or control of system’s vibrations. In spite of this fact that the destructive and undesirable vibrations, will have a detrimental effect on the main system, it will also have negative impact on all machinery equipments in any complex. In this paper, we attempt to present a new design for Adaptive Tuned Dynamic Vibration Absorber (ATDVA), Based on Smart Slider-Crank Mechanism. This research will also investigate a practical scheme which is applied to reduce the excessive beam vibration to an acceptable range by adding an absorber to a vibratory resonant beam, especially as an alternative to active vibration control.

고분해능 장애물 탐지를 위한 중첩 초음파 센서 링의 최적 설계

This paper presents the optimal design of an overlapped ultrasonic sensor ring for high resolution obstacle detection of an autonomous mobile robot. It is assumed that a set of low directivity ultrasonic sensors of the same type are arranged along a circle of nonzero radius at a regular spacing with their beams overlapped. First, taking into account the dead angle region, the entire range of obstacle detection is determined with reference to the center of an overlapped ultrasonic sensor ring. Second, the optimal design index of an overlapped ultrasonic sensor ring is defined as the area closeness of three sensing subzones resulting from beam overlap. Third, the lower and upper bounds on the number of ultrasonic sensors are derived, which can guarantee minimal beam overlap and also avoid excessive beam overlap among adjacent ultrasonic sensors. Fourth, employing a commercial low directivity ultrasonic sensor, an optimal design example of an overlapped ultrasonic sensor ring is given along with the ultrasonic sensor ring prototype mounted on top of a mobile robot. Finally, some experimental results using our prototype ultrasonic sensor ring are given to demonstrate the validity and performance of an optimally overlapped ultrasonic sensor ring for high resolution obstacle detection.

EXPERIMENTAL STUDY ON IMPROVED PRECAST UNBONDED POST-TENSIONED BEAM-COLUMN JOINT SYSTEM

The aim of this study is to investigate the seismic behavior of improved unbonded post-tensioned precast concrete beam-column connections with and without shear bracket. Three specimens of precast unbonded post-tensioned exterior beam-column connection were designed and tested. The test results of the specimen without shear bracket showed excessive beam slip and large residual deformation. The specimens with shear bracket expressed very satisfied performance with small residual deformation, almost no slip, fully developed strength, minor damage to the beam and column elements, and easy to disassemble. It is concluded that satisfied seismic performance can be expected from well-designed connection with shear bracket.

TH‐D‐BRB‐08: The Effect of Transverse Magnetic Fields on a Simulated In‐Line 6 MV Linac

Purpose: The linac waveguide is subjected to large magnetic fringe fields in a linac‐MR hybrid system. An investigation is performed to determine the effect of transverse magnetic fields on a simulated in‐line 6 MV medical linac. Method and Materials: The program PARMELA was used calculate the electron beam loss per cavity with the linac waveguide subjected to external transverse fields. BEAMnrc and DOSXYZnrc were used to calculate the effect on 40×40 and 20×20 cm2 field dose profiles and depth dose curves with the linac submersed in a transverse magnetic field. DOSRZnrc was used to determine the heating per cavity as a result of the beam loss and COMSOL was used to determine the resulting cavity resonant frequency changes due to cavity heating. Lastly a calculation of leakage radiation caused by the excessive beam loss was performed using BEAMnrc. Results: The beam loss was calculated to be 5±1 22±1 and 49±1% over nominal for 2 4 and 6 G magnetic fields respectively. The transverse magnetic fields caused a shifting of the electron spatial distribution at the target which resulted in a lateral shift of the dose profiles making 14.4% of all points fail a 1%/1mm acceptance criterion at a 6 G field. Through asymmetric jaw positions the lateral shift in the dose profiles was reduced such that only 0.5% of all points failed. The frequency of the accelerating mode changed by 0.03 Hz due to heating and a total leakage radiation of 0.007% of the radiation field was calculated. Conclusion: The 6 MV linac investigated showed sufficient tolerance to be used in transverse magnetic fields larger than earth's field. The shifts observed in the dose profiles were reduced through asymmetric jaw positions such that only 0.5 % of the points failed a 1 %/ 1 mm criterion at 6 G.

Commissioning and first operation of the pCVD diamond ATLAS beam conditions monitor

The Beam Conditions Monitor (BCM) [1,5] of the ATLAS experiment protects the Inner Detector silicon trackers from high radiation doses caused by LHC beam incidents. It uses 161×1cm2500μm thick polycrystalline chemical vapor deposition (pCVD) diamond sensors arranged in 8 positions around the interaction point. Time difference measurements with 2.56GHz sampling are performed to distinguish between collision and background. In case of excessive beam background due to beam incidents, the BCM can trigger a beam abort. A FPGA based readout system performs the online data analysis and interfaces the results to ATLAS and the beam abort system. The diamond sensors, the detector modules and their readout system are described. Results of the operation with the first LHC beams are reported. Results of commissioning and timing measurements with cosmic muons in preparation for first LHC collisions are summarized.

Short bunch effect on tabletop THz FEL amplification

A tabletop THz free-electron laser (FEL) amplifier, which consists of a photocathode radio-frequency gun and an undulator, has been studied at the Institute of Advanced Energy, Kyoto University. The concepts of the THz amplifier are (1) a high peak power of about 1 MW, (2) a whole length of less than 4 m, and (3) a spectral range of 150–300 μm. For the feasibility study for the conceptual design, a start-to-end simulation was conducted by using Parmela and GENESIS 1.3. The slippage effect and the diffraction loss were taken into account in the FEL simulation. An output power of about 350 kW is expected from the present design scheme. The calculation shows that the short bunch electron beam has an advantage toward obtaining a higher FEL gain because of its small energy spread. Since the slippage effect becomes dominant, however, the FEL gain drops with the excessive short bunch beam.

Seismic performance of mechanically coupled reinforcing bars

Seismic performance verification of a spiral thread mechanical reinforcement connection system for use in reinforced concrete structures was investigated by conducting both in-air component tests and structural subassembly tests. Current performance verification criteria listed in NZS 3101:2006 were found to be outdated and, following a review of various international protocols for testing mechanical connection systems, it was concluded that DIS 15835 protocols should instead be considered for adoption. Two external beam–column joint subassemblies having spiral thread mechanical reinforcement couplers installed at the column–joint interface were subjected to simulated seismic cyclic loading. It was found that bar curvature and the development of a non-uniform stress distribution around the perimeter of the reinforcement–coupler connection led to coupler slippage. However, the measured pinched hysteretic response owing to coupler slippage closely matched the response of companion tests where strength degradation was instead a result of excessive beam shear deformations. It was concluded that uniaxial tensile tests are unable accurately to demonstrate probable coupler performance in plastic hinge zones and that such tests should therefore not be used to predict likely ductile response in potential plastic hinge zones of reinforced concrete members.

Post-Northridge connection with modified beam end configuration to enhance strength and ductility

In order to enhance the strength and ductility of post-Northridge connections with beam depths varying from 450 mm to 912 mm, two parallel horizontal long voids were opened on their beams web. Results showed that the proposed beam end configuration (BEC) is effective in moving the plastic hinge away from the column face. Adding web stiffeners and two tubes at the center of voids were effective in preventing excessive beam flange/web buckling. Based on the analytical results a step by step design procedure is proposed to determine the most suitable geometry for the BEC to achieve adequate connection strength and ductility.

Scaling laws for energetic ions from the commissioning of the new Los Alamos National Laboratory 200 TW Trident laser

The recent Los Alamos National Laboratory Trident laser enhanced from 30 to 200 TW in power allows more than 100 J to be delivered on target in 500 fs with a spot size smaller than 12 microm at full width at half maximum. 15 microm flat-foil targets have been observed to produce proton beams in excess of 50 MeV at an intensity of only approximately 4x10(19) W/cm(2) with efficiencies approaching 5%. The Trident laser beam characteristics are presented along with the data compared to published scaling laws for proton acceleration.

Ultrasonic beam propagation in highly anisotropic materials simulated by multi-Gaussian beams

The necessity of nondestructively inspecting fiber-reinforced composites, austenitic steels, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface play a key role in the beam models based on the paraxial approximation. In this paper, we apply a modular muiti-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal (qL) beam propagates in the symmetry plane of a transversely isotropic gr/ep composite. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.

Technical Note: Use of a beam width probe in an Aerosol Mass Spectrometer to monitor particle collection efficiency in the field

Abstract. Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico City, during the Mexico City Metropolitan Area field study (MCMA-2003) from 29 March–4 May 2003 to investigate particle concentrations, sources, and processes. We report the use of a particle beam width probe (BWP) in the field to quantify potential losses of particles due to beam broadening inside the AMS caused by particle shape (nonsphericity) and particle size. Data from this probe show that no significant mass of particles was lost due to excessive beam broadening; i.e. the shape- and size-related collection efficiency (Es) of the AMS during this campaign was approximately one. Comparison of the BWP data from MCMA-2003 with other campaigns shows that the same conclusion holds for several other urban, rural and remotes sites. This means that the aerodynamic lens in the AMS is capable of efficiently focusing ambient particles into a well defined beam and onto the AMS vaporizer for particles sampled in a wide variety of environments. All the species measured by the AMS during MCMA-2003 have similar attenuation profiles which suggests that the particles that dominate the mass concentration were internally mixed most of the time. Only for the smaller particles (especially below 300 nm), organic and inorganic species show different attenuation versus particle size which is likely due to partial external mixing of these components. Changes observed in the focusing of the particle beam in time can be attributed, in part, to changes in particle shape (i.e. due to relative humidity) and size of the particles sampled. However, the relationships between composition, atmospheric conditions, and particle shape and size appear to be very complex and are not yet completely understood.

Hysteresis behavior of semi-rigid double web angle steel connections

Abstract This study presents the cyclic behavior of two types of semi-rigid double web angle connections: bolted-bolted (angles bolted to the beam web and column flange) and welded-bolted (angles welded to beam web and bolted to column flange), with their bolts pretensioned to the proof load. Twenty test specimens were prepared and cyclic load was applied to each test specimen using load control at the beginning cycles, which was converted to displacement control in subsequent cycles upon yielding of angles or bolts materials. The moment–rotation hysteresis loops and the failure modes for all the test cases are presented. The failure modes for bolted-bolted test specimens, depending on angle thickness, were either excessive rotation or beam web bearing, and for the welded-bolted specimens were excessive rotation or bolt fracture. The stiffness, strength, and ductility of the tested connections are compared to those of flush end-plate moment connections reported in literature.

The radiation measurement applied to beam lifetime study on the synchrotron radiation facilities

To collect beam loss information from an accelerator radiation field is helpful to machine study and operation. For a synchrotron radiation storage ring, shower electrons give a distinct clue to loss location and a BLM-XS model detector is suitable to detect them. Recently, we set up a new beam loss monitoring system by this method for National Synchrotron Radiation Laboratory (NSRL) storage ring. It does not interfere with the vacuum chamber and machine operation. Different from other systems, the detectors are used in pairs, fixed on opposite sides of the chamber separately. Some interesting phenomena about beam lifetime were observed. We located exactly where an excessive beam loss took place during ramping process and solved the problem. It was proved that gas accumulated at the front ends of photo-beam lines strongly impacted the electron beam and led to beam lifetime decreases. The cause of beam lifetime decrease because of superconducting wiggler is discussed.

Investigation of the alignment phenomena using a-C:H thin films for liquid crystal alignment materials

A high pretilt angle is generated by hydrogenated amorphous carbon (a-C:H) thin films treated with an ion beam method. a-C:H thin films are deposited by remote plasma enhanced chemical vapor deposition and are modified by an Ar ion beam at an incidence angle of 45° using an Kaufman ion gun. Ion beam irradiation results in the decrease of the thickness of a-C:H thin films and the increase of the sp 2 fraction. The optical transmittance of the ion beam irradiated a-C:H is more affected by thickness than sp 2 fraction. An excessive ion beam irradiation, 5 min Ar ion beam, results in the increase of the surface roughness of the a-C:H thin films and the pretilt angle has very low value. The pretilt angle is controlled by the thickness, sp 2 fraction and the surface roughness.

Smith–Purcell experiment utilizing a field-emitter array cathode: measurements of radiation

Smith–Purcell (SP) radiation at wavelengths of 350–750 nm was produced in a tabletop experiment using a field-emitter array (FEA) cathode. The electron gun was 5 cm long, and a 25 mm×25 mm holographic replica grating was placed behind the slit provided in the anode. A regulated DC power supply accelerated electron beams in excess of 10 μA up to 45 keV, while a small Van de Graaff generator accelerated smaller currents to higher energies. The grating had a 0.556 μm period, 30° blaze and a 0.2 μm thick aluminum coating. Spectral characteristics of the radiation were measured both manually and automatically; in the latter case, the spectrometer was driven by a stepping motor to scan the wavelength, and AD-converted signals from a photomultiplier tube were processed by a personal computer. The measurement, made at 80° relative to the electron beam, showed good agreement with theoretical wavelengths of the SP radiation. Diffraction orders were −2 and −3 for beam energies higher than 45 keV, −3 to −5 at 15–25 keV, and −2 to −4 in between. The experiment has thus provided evidence for the practical applicability of FEAs to compact radiation sources.

Improvement of JT-60U negative ion source performance

The several hundred keV neutral beamline which is now operating on JT-60U marks the first usage of negative ion sources to produce high power neutral beams. Because this was such a large advance in the state of the art with respect to all system parameters, many new physical processes appeared during the earlier phases of the beam injection experiments. The physical mechanisms responsible for these processes have been explored, and solutions have been implemented for some of them, in particular excessive beam stripping, the secular dependence of the arc and beam parameters, and the non-uniformity of the plasma illuminating the beam extraction grid. This has reduced the percentage of beam heat loading on the downstream grids by roughly a third and has permitted longer beam pulses at higher powers. Progress is being made in improving the negative ion current density and in coping with the sensitivity of the caesium in the ion sources to oxidation by tiny air or water leaks, and the cathode operation is being altered.

The influence of mask substrate thickness on exposure and development times for the LIGA process

Optimizing mask substrate thickness is an important practical concern in the X-ray exposure of PMMA resists for LIGA. An overly thick substrate necessitates long exposure times due to excessive beam filtering, while a substrate too thin leads to long development times due to low absorbed doses at the PMMA bottom surface. To assist in this optimization, we have developed numerical models describing both the exposure and development of a PMMA resist. These exposure and development models are coupled in a single interactive code, permitting automated adjustment of mask substrate thickness to yield the minimum of a prescribed cost object function that depends on both the exposure and development times. Results are presented for several synchrotron sources and over a wide range of the PMMA thickness.

Matching the injected ion beam into an rf Linac for a high-energy, high-current ion implanter

Over the last several years, high-energy (in the MeV range) ion implantation has become an integral part of mainstream semiconductor device manufacturing. The rapid growth in the use of the high-energy ion implanters has been driven by device engineering process requirements. At Eaton, we have developed an rf Linac based high-energy implanter, NV-GSD/VHE, capable of delivering 1.7 MeV B+ beam in excess of 1 mA. However, as high-dose buried layers and 300 mm substrates emerge for mainstream integrated circuit processing, a need for a significantly higher B+ beams up to 2 MeV is on the horizon. To maximize the beam transmission, optimizing the match between the injected ion beam and the Linac acceptance is essential. A pepper-pot emittance measurement apparatus is used to measure the beam emittance down stream of the ion source extraction optics. The ion source beam emittance requirement, its measured and theoretical values for our ion source will be discussed.

Status and new developments of the high intensity electron cyclotron resonance source light ion continuous wave, and pulsed mode (invited)

The high intensity light ion source (SILHI) is the electron cyclotron resonance (ECR) source constructed and tested at CEA-Saclay. The first aim is to produce up to 100 mA cw proton beams at 95 keV for the proton injection high intensity (IPHI) beams [5 MeV radio frequency quadrupole (RFQ) and 10 MeV drift tube linac (DTL)]. This prototype is developed by a CEA–CNRS-IN2P3 collaboration for applications such as accelerator driven systems for nuclear waste transmutation, production of radioactive ion beams or secondary particles. SILHI is also used to study the production of deuteron and H− beams for the International Fusion Material Irradiation Facility and European spallation source projects, respectively. The present status of SILHI and the experiments planned for the near future in both cw and pulsed modes are presented in this article. 80 mA cw proton beams are now currently produced at 95 keV with a high availability (∼1 spark/day). The proton fraction is around 90% and the typical r–r′ rms normalized emittance after transport through a single solenoid low energy beam transport (LEBT) without beam losses is 0.3 πmm mrad. The best beam characteristics are obtained when an ECR zone is created at the frontier between the plasma chamber and the rf ridged transition. Extensive emittance measurements performed with different gas injection in the LEBT have shown a factor of three emittance reduction. Space charge compensation measurements in cw mode will be undertaken with a four-grid analyzer to understand this behavior. Time resolved space charge compensation measurements in pulsed mode are also discussed. The highest total beam current of 120 mA (240 mA/cm2) can be extracted with two ECR zones located at the plasma chamber extremities. Nevertheless a new electrode design must be done for this configuration to avoid excessive beam losses in the extraction system.