Beam loading compensation in the NLCTA
In the design of the Next Linear Collider (NLC), multi-bunch operation is employed to improve efficiency at the cost of substantial beam loading. The RF pulse that powers the accelerator structures will be shaped to compensate for the effect of the transient loading along the bunch train. This scheme has been implemented in the Next Linear Collider Test Accelerator (NLCTA), a facility built to test the key accelerator technology of the NLC. In this paper the authors describe the compensation method, the techniques used to measure the energy variation along the bunch train, and results from tests with NLC-like beam currents
Beam loading compensation for the NLC low frequency linacs
The NLC low rf linacs are heavily loaded by a beam of about 130 ns in macropulse length (90 bunches) and a current up to 2.75 Amps. Beam loading voltage generates a large energy spread along the bunch train. This energy spread is critical for lattice design and, if not properly compensated, induces emittance growth and in turn lowers the luminosity of the machine. In this paper, the authors study the ΔF and ΔT beam loading compensation techniques for the NLC low rf linacs. They will apply these methods to the NLC low rf linacs to demonstrate the efficacy of these methods. Finally, they discuss a hybrid ΔT + ΔF method to improve the efficiency of beam loading compensation
Compensation of initial beam loading for electron linacs
Serious initial beam loading effect may generate beam loss in the electron linac of the VSX light source. Because of the large energy spread, it is difficult to compensate the beam loading with ordinary methods, such as the adjustment of injection timing and ECS (Energy Compensation System). We have developed a phase-amplitude (Δφ-A) modulation system using two fast phase shifters, which is put before a klystron and operated at low power level. In this paper, we report the performance of the test system. (author)
Beam Loading Compensation in the Main Linac of CLIC
Schulte, D.; Syratchev, I.
2000-01-01
Compensation of multi-bunch beam loading is of great importance in the main linac of the Compact Linear Collider (CLIC). The bunch-to-bunch energy variation has to stay below 1 part in 1000. In CLIC, the RF power is obtained by decelerating a drive beam which is formed by merging a number of short bunch trains. A promising scheme for tackling beam loading in the main linac is based on varying the lengths of the bunch trains in the drive beam. The scheme and its expected performance are presen...
Beam loading compensation with variable group velocity
Consider a section with linearly variable group velocity and a beam pulse shorter than the section fill time. Choose the current amplitude so that the gradient of the last bunch equals the gradient of the first bunch. For beam pulses less than about 15% of fill time, the voltage deviation during the beam pulse is small, but as the pulse width increases the voltage deviation also increases. We show that by decreasing the output to input group velocity ratio, we can reduce the first order voltage deviation, and that we can remove the remaining second-order voltage deviation by linearly decreasing the section input power by a small amount starting at beam injection time. This way we can increase the beam pulse width to more than half the fill time, and thereby increase the RF to beam energy transfer efficiency and the luminosity without increasing the voltage deviation
First beam test of ΔΦ-A initial beam loading compensation for electron linacs
The initial-beam-loading effect may cause serious beam loss in the electron linac of the Super SOR light source. Because of the large energy spread, it is difficult to compensate the beam loading with ordinary methods, such as the adjustment of injection timing and ECS (Energy Compensation System). A phase-amplitude (ΔΦ-A) modulation system has already been developed and tested. First beam test using this system was carried out at the 125 MeV electron linac of Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Its result shows that our system well corrects the energy spread due to initial beam loading effect. In this paper, we report the results of first beam test. (author)
Multi-harmonic beam loading compensation in the J-PARC RCS
For acceleration of high intensity proton beams in the J-PARC RCS, the beam loading compensation is important. In the wide-band (Q = 2) MA-loaded RF cavity, the wake voltage consists of not only the fundamental accelerating harmonic component (h = 2) but also the higher harmonics. The higher harmonic components cause the RF bucket distortion. We employ the RF feedforward method to compensate the multi-harmonic beam loading. The full-digital feedforward system is developed, which compensates the most important three harmonic components (h = 2, 4, 6) of the wake voltages. We present the results of the beam commissioning with a high intensity proton beam (2.5x1013 ppp). The impedance seen by the beam is greatly reduced. We also report the beneficial effects of the feedforward compensation in the beam operation. (author)
Beam loading and cavity compensation for the Ground Test Accelerator
The Ground Test Accelerator (GTA) will be heavily beam-loaded H- linac with tight tolerances on accelerating field parameters. The methods used in modeling the effects of beam loading in this machine are described. The response of the cavity to both beam and radio-frequency (RF) drive stimulus is derived, including the effects of cavity detuning. This derivation is not restricted to a small-signal approximation. An analytical method for synthesizing a predistortion network that decouples the amplitude and phase responses of the cavity is also outline. Simulation of performance, including beam loading, is achieved through use of a control system analysis software package. A straightforward method is presented for extrapolating this work to model large coupled structures with closely spaced parasitic modes. Results to date have enabled the RF control system designs for GTA to be optimized and have given insight into their operation. 6 refs., 10 figs
Beam loading compensation for acceleration of multi-bunch electron beam train
Liu, Shengguang; Fukuda, Masafumi; Araki, Sakae; Terunuma, Nobuhiro; Urakawa, Junji; Hirano, Koichiro; Sasao, Noboru
2008-01-01
The laser undulator compact X-ray source (LUCX) is a test bench used with the compact, high-brightness X-ray generator at KEK (High Energy Accelerator Research Organization). Our group is conducting experiments with LUCX to demonstrate the possibility of K-edge digital subtraction angiography, based on Compton scattering. One of the challenging problems is to generate high-brightness multi-bunch electron beams to compensate for the energy difference arising from the beam loading effect. In this paper we calculate the transient beam loading voltage and energy gain from the RF field in the gun and accelerating tube for a multi-bunch train. To do so we consider the process by which the RF field builds up in the gun and accelerating tube, and the special shape of the RF pulse. We generate and accelerate 100 bunches with a 50 nC electron bunch train, effectively compensating for the beam loading effect by adjusting the injection timing. Using a beam position monitor (BPM) and optical transition radiation (OTR) system, we measure the electron beam energy bunch by bunch. The average energy of a 100-bunch train is 40.5 MeV and the maximum energy difference from bunch to bunch is 0.26 MeV.
Beam loading compensation for acceleration of multi-bunch electron beam train
The laser undulator compact X-ray source (LUCX) is a test bench used with the compact, high-brightness X-ray generator at KEK (High Energy Accelerator Research Organization). Our group is conducting experiments with LUCX to demonstrate the possibility of K-edge digital subtraction angiography, based on Compton scattering. One of the challenging problems is to generate high-brightness multi-bunch electron beams to compensate for the energy difference arising from the beam loading effect. In this paper we calculate the transient beam loading voltage and energy gain from the RF field in the gun and accelerating tube for a multi-bunch train. To do so we consider the process by which the RF field builds up in the gun and accelerating tube, and the special shape of the RF pulse. We generate and accelerate 100 bunches with a 50 nC electron bunch train, effectively compensating for the beam loading effect by adjusting the injection timing. Using a beam position monitor (BPM) and optical transition radiation (OTR) system, we measure the electron beam energy bunch by bunch. The average energy of a 100-bunch train is 40.5 MeV and the maximum energy difference from bunch to bunch is 0.26 MeV
Beam-Loading Compensation for Super B-Factories
Teytelman, D.; /SLAC
2005-12-14
Super B-factory designs under consideration expect to reach luminosities in the 10{sup 35}-10{sup 36} range. The dramatic luminosity increase relative to the existing B-factories is achieved, in part, by raising the beam currents stored in the electron and positron rings. For such machines to succeed it is necessary to consider in the RF system design not only the gap voltage and beam power, but also the beam loading effects. The main effects are the synchronous phase transients due to the uneven ring filling patterns and the longitudinal coupled-bunch instabilities driven by the fundamental impedance of the RF cavities. A systematic approach to predicting such effects and for optimizing the RF system design will be presented. Existing as well as promising new techniques for reducing the effects of heavy beam loading will be described and illustrated with examples from the PEP-II and the KEKB.
CLIC Main Linac Beam-Loading Compensation by Drive Beam Phase Modulation
Corsini, R; Syratchev, I V
1999-01-01
The CLIC final focus momentum acceptance of ± 0.5 % limits the bunch-to-bunch energy variation in the main beam to less than ± 0.1 %, since the estimated single-bunch contribution is ± 0.4 %. On the other hand, a relatively high beam-loading of the main accelerating structures (about 16 %) is unavoidable in order to optimize the RF-to-beam efficiency. Therefore, a compensation method is needed to reduce the resulting bunch-to-bunch energy spread of the main beam. Up to now, it has been planned to obtain the RF pulse shape needed for compensation by means of a charge ramp in the drive beam pulse. On the other hand, the use of constant-current drive beam pulses would make the design and operation of the drive beam injector considerably simpler. In this paper we present a possible solution adapted to the CLIC two-beam scheme with constant-current pulses, based on phase modulation of the drive beam bunches.
Transient beam loading compensation in traveling wave linear accelerators
For normal conducting linear colliders the transient beam loading in the accelerating structures is typically of the order of 20-30%. This results in a multibunch energy spread of the same magnitude if no remedy is taken into account. On the other hand, in a linear collider the transient energy spread has to be controlled down to a few tenth of a percent. Two possible methods, assuming two different setups, e.g. klystron plus structure and klystron plus SLED cavity plus structure, are investigated. A description of the whole rf system and the resulting energy spread is presented especially for the case of the S-Band linear collider study. (orig.)
A scheme to compensate the transient beam loading in TW electron linacs
A scheme to compensate the transient beam loading of the TW electron linac operated in multi-bunch mode is described. The proposed method is to excite an auxiliary cavity located at the end of the accelerator section with the residual rf power, which comes out of the section after one filling time, with properly adjusted phase and amplitude of the field. The transient energy gain of the electron beam in passing through the cavity will compensate the transient energy loss due to beam loading in the accelerator section. The parameters of ATF of Brookhaven National Laboratory are used for calculation as an example to illustrate the result of computation
Narrowband beam loading compensation in the Fermilab Main Injector accelerating cavities
Joseph E. Dey; John S. Reid and James Steimel
2001-07-12
A narrowband beam loading compensation system was installed for the Main Injector Accelerating Cavities. This feedback operates solely on the fundamental resonant mode of the cavity. This paper describes modifications to the high level Radio Frequency system required to make the system operational. These modifications decreased the effect of steady-state beam loading by a factor of 10 and improved the reliability of paraphasing for coalescing.
Initial-beam-loading compensation system for high-intensity electron linacs
We developed an initial-beam-loading compensation system for electron linacs. This system consists of a ΔΦ-A (phase-to-amplitude) modulator and a fast-phase detector. The ΔΦ-A modulator can modulate the phase and the amplitude of a low-power RF simultaneously. Low-power and high-power tests were successfully carried out at KEK. The result of the high-power tests show that our system can reduce the energy spread from 27 to 0.3% for a 300-mA average current. The system that we developed can be a powerful tool for initial-beam-loading compensation. In addition, a numerical calculation method using the power-flow matrix was formulated to perform a fast beam-energy calculation with a simple algorithm. This method can be used to obtain the target RF waveform for energy-spread compensation
Transient beam-loading model and compensation in Compact Linear Collider main linac
Kononenko, O
2011-01-01
A new model to compensate for the transient beam loading in the CLIC main linac is developed. It takes into account the CLIC specific power generation scheme and the exact 3D geometry of the accelerating structure including couplers. A new method of calculating unloaded and loaded voltages during the transient is proposed and a dedicated optimization scheme of the rf pulse to compensate the transient beam-loading effect is presented. It is demonstrated that the 0.03% limit on the rms relative bunch-to-bunch energy spread in the main beam after acceleration can be reached. The optimization technique has been used to increase the rf to beam efficiency while preserving the CLIC requirements and to compensate for the energy spread caused by the Balakin-Novokhatski-Smirnov damping and transient process in the subharmonic buncher. Effects of charge jitters in the drive and main beams are studied. It is shown that within the 0.1% CLIC specification limit on the rms spread in beams charge the energy spread is not sig...
Study on transient beam loading compensation for China ADS proton linac injector II
Gao, Zheng; Wang, Xian-Wu; Chang, Wei; Zhang, Rui-Feng; Zhu, Zheng-Long; Zhang, Sheng-Hu; Chen, Qi; Powers, Tom
2016-01-01
Significant transient beam loading effects were observed during beam commissioning tests of prototype II of the injector for the Accelerator Driven Sub-critical (ADS) system, which took place at the Institute of Modern Physics, Chinese Academy of Sciences, between October and December 2014. During these tests experiments were performed with CW operation of the cavities with pulsed beam current, and the system was configured to make use of a prototype digital low level radio frequency (LLRF) controller. The system was originally operated in pulsed mode with a simple PID feedback control algorithm, which was not able to maintain the desired gradient regulation during pulsed 10 mA beam operations. A unique simple transient beam loading compensation method which made use of a combination of PI feedback and feedforward control algorithm was implemented in order to significantly reduce the beam induced transient effect in the cavity gradients. The superconducting cavity field variation was reduced to less than 1.7%...
Gamp, Alexander
2013-01-01
We begin by giving a description of the radio-frequency generator-cavity-beam coupled system in terms of basic quantities. Taking beam loading and cavity detuning into account, expressions for the cavity impedance as seen by the generator and as seen by the beam are derived. Subsequently methods of beam-loading compensation by cavity detuning, radio-frequency feedback and feedforward are described. Examples of digital radio-frequency phase and amplitude control for the special case of superconducting cavities are also given. Finally, a dedicated phase loop for damping synchrotron oscillations is discussed.
Numerical investigation of transient beam loading compensation in JLC X-band main linac
Syrachev, I.V. [AN SSSR, Novosibirsk (Russian Federation). Inst. Yadernoj Fiziki; Higo, T.
1996-06-01
In the present paper, two methods, `staggered timing` and `RF modulation`, were studied for the transient beam loading compensation in the JLC X-band main linac. The inter bunch energy spread was found to be easily reduced down to less than {+-}0.06% with 10 sets of injection timings along the linac in the former case while with a simple linear ramping of the input RF voltage in the latter case. For both cases the energy transfer efficiencies from the power source to the beam were exactly the same. The tolerance of the beam intensity jitter was found to be {+-}1% for the multibunch energy spread of {+-}0.1%. (author)
Pulse-by-pulse switching of beam loading compensation in J-PARC Linac LLRF
For the J-PARC linac low level RF system, in order to compensate beam-loading change by pulses in the operation of 25-Hz repetition, a function that switches the feed-forward control parameters in every pulse were installed into the digital accelerating-field control system. The linac provides a 50-mA peak current proton beam to a 3-GeV rapid-cycling synchrotron (RCS). Then the RCS distributes the 3-GeV beam into a following 50-GeV synchrotron (main ring, MR) and the Materials and Life Science Facility (MLF), which is one of the experimental facilities in the J-PARC. The 500-us long macro pulses from the ion source of the linac should be chopped into medium pulses for injection into the RCS. The duty (width or repetition) of the medium pulse depends on which facility the RCS provides the beam to the MR or MLF. Therefore the beam loading compensation needs to be corrected for the change of the medium pulse duty in the 25-Hz operation. (author)
Study on transient beam loading compensation for China ADS proton linac injector II
Gao, Zheng; He, Yuan; Wang, Xian-Wu; Chang, Wei; Zhang, Rui-Feng; Zhu, Zheng-Long; Zhang, Sheng-Hu; Chen, Qi; Powers, Tom
2016-05-01
Significant transient beam loading effects were observed during beam commissioning tests of prototype II of the injector for the accelerator driven sub-critical (ADS) system, which took place at the Institute of Modern Physics, Chinese Academy of Sciences, between October and December 2014. During these tests experiments were performed with continuous wave (CW) operation of the cavities with pulsed beam current, and the system was configured to make use of a prototype digital low level radio frequency (LLRF) controller. The system was originally operated in pulsed mode with a simple proportional plus integral and deviation (PID) feedback control algorithm, which was not able to maintain the desired gradient regulation during pulsed 10 mA beam operations. A unique simple transient beam loading compensation method which made use of a combination of proportional and integral (PI) feedback and feedforward control algorithm was implemented in order to significantly reduce the beam induced transient effect in the cavity gradients. The superconducting cavity field variation was reduced to less than 1.7% after turning on this control algorithm. The design and experimental results of this system are presented in this paper. Supported by National Natural Science Foundation of China (91426303, 11525523)
Numerical investigation of transient beam loading compensation in JLC X-band main linac
In the present paper, two methods, 'staggered timing' and 'RF modulation', were studied for the transient beam loading compensation in the JLC X-band main linac. The inter bunch energy spread was found to be easily reduced down to less than ±0.06% with 10 sets of injection timings along the linac in the former case while with a simple linear ramping of the input RF voltage in the latter case. For both cases the energy transfer efficiencies from the power source to the beam were exactly the same. The tolerance of the beam intensity jitter was found to be ±1% for the multibunch energy spread of ±0.1%. (author)
Beam loading compensation in thermionic RF gun by using RF detuning
A new beam energy compensation method was investigated, which can suppress the beam energy drop in a thermionic RF gun caused by the beam current increase due to the back-bombardment effect. The method is to feed a RF power with slightly higher (detuned) frequency to the gun. The principle of this method is based on that the increment of the beam conductance could be cancelled out by the increment of beam suceptance. As a result of numerical simulation, the increase of current density on the cathode surface from 47 to 176 A/cm2 can be compensated by 550 kHz detuned RF power. Results of experiment showed a good agreement with the simulation, and the effectiveness of this method was demonstrated. (author)
In this paper, a new method of transient beam loading compensation for the next generation of TeV e+e- linear collider with multibunching is presented. The method is based on applications of the π/2 - mode standing wave accelerating structure with the reflected wave used for beam loading compensation. Various compensation methods for transient beam loading for the constant gradient traveling wave and π/2 standing wave structures are compared. It is shown that the proposed method provides an approximately 10% higher efficiency of the RF source energy utilization than that for the traveling wave accelerating structure. (author)
Beam loading compensation of traveling wave linacs through the time dependence of the rf drive
Beam loading in traveling-wave linear accelerating structures leads to unacceptable spread of particle energies across an extended train of bunched particles due to beam-induced field and dispersion. Methods for modulating the rf power driving linacs are effective at reducing energy spread, but for general linacs do not have a clear analytic foundation. We report here methods for calculating how to modulate the rf drive in arbitrarily nonuniform traveling-wave linacs within the convective-transport (power-diffusion) model that results in no additional energy spread due to beam loading (but not dispersion). Varying group velocity, loss factor, and cell quality factor within a structure, and nonzero particle velocity, are handled.
Tamura, Fumihiko; Ohmori, Chihiro; Yamamoto, Masanobu; Yoshii, Masahito; Schnase, Alexander; Nomura, Masahiro; Toda, Makoto; Shimada, Taihei; Hasegawa, Katsushi; Hara, Keigo
2013-05-01
Beam loading compensation is a key for acceleration of a high intensity proton beam in the main ring (MR) of the Japan Proton Accelerator Research Complex (J-PARC). Magnetic alloy loaded rf cavities with a Q value of 22 are used to achieve high accelerating voltages without a tuning bias loop. The cavity is driven by a single harmonic (h=9) rf signal while the cavity frequency response also covers the neighbor harmonics (h=8,10). Therefore the wake voltage induced by the high intensity beam consists of the three harmonics, h=8,9,10. The beam loading of neighbor harmonics is the source of periodic transient effects and a possible source of coupled bunch instabilities. In the article, we analyze the wake voltage induced by the high intensity beam. We employ the rf feedforward method to compensate the beam loading of these three harmonics (h=8,9,10). The full-digital multiharmonic feedforward system was developed for the MR. We describe the system architecture and the commissioning methodology of the feedforward patterns. The commissioning of the feedforward system has been performed by using high intensity beams with 1.0×1014 proteins per pulse. The impedance seen by the beam is successfully reduced and the longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, stable high power beam operation is achieved. We also report the reduction of the momentum loss during the debunching process for the slow extraction by the feedforward.
Kelisani, M. Dayyani; Doebert, S.; Aslaninejad, M.
2016-08-01
The critical process of beam loading compensation in high intensity accelerators brings under control the undesired effect of the beam induced fields to the accelerating structures. A new analytical approach for optimizing standing wave accelerating structures is found which is hugely fast and agrees very well with simulations. A perturbative analysis of cavity and waveguide excitation based on the Bethe theorem and normal mode expansion is developed to compensate the beam loading effect and excite the maximum field gradient in the cavity. The method provides the optimum values for the coupling factor and the cavity detuning. While the approach is very accurate and agrees well with simulation software, it massively shortens the calculation time compared with the simulation software.
Respiratory load compensation in uremia.
Heinzmann, H G; Kassabian, J; Naqui, M N; Lavietes, M H
1981-01-01
The clinical significance of respiratory-system load-compensation is unknown. We have measured the responses to random presentation of single, elastic inspiratory loads in 36 subjects: 8 normal personnel (N), 9 with obesity (O), 10 with chronic renal failure under hemodialysis (H), 5 with pneumonia (P), and 4 with interstitial lung disease (CILD). We have expressed these responses as: (1) the ratio of elastance (or rigidity) of the system during loaded breathing to the elastance without loading (E'RS/ERS); (2) the ratio of tidal volume (VT) achieved when breathing from an inspiratory load to the VT predicted in the absence of load compensation (VTL/VTP); (3) the ratio of inspiratory flow rates during loaded and unloaded breaths; (4) the ratio of inspiratory time of loaded and unloaded breaths. We found E'RS/ERS in the O, H and P groups less than that of either CILD patients or N controls (F = 6.79; p less than 0.001). Passive elastance (ERS) although greater in groups O and H than in N (F = 3.88; p less than 0.025) did not account for the difference i E'RS in all groups. When expressed as VTL/VTP, the response to a 37-cm H2O/l load for groups H, O and P was less than that for N (F = 5.51; p less than 0.05). Diminished inspiratory time was observed in H, O and P patients when inspiring from this load. In contrast, inspiratory flow did not differ from that of normal subjects. Nerve conduction velocity was slightly reduced or normal in the H patients. Respiratory load compensation is deficient in H, O and P patients. The mechanism, which does not involve peripheral neuropathy, is unclear. PMID:7244394
Beam - cavity interaction beam loading
The interaction of a beam with a cavity and a generator in cyclic accelerators or storage rings is investigated. Application of Maxwell's equations together with the nonuniform boundary condition allows one to get an equivalent circuit for a beam-loaded cavity. The general equation for beam loading is obtained on the basis of the equivalent circuit, and the beam admittance is calculated. Formulas for power consumption by a beam-loaded cavity are derived, and the optimal tuning and coupling factor are analyzed. (author)
Improved load-cell compensation
Egger, R. L.
1977-01-01
Improved bridge-compensation circuit saves considerable time in balancing bridge and wiring it for temperature compensation. Large bridge-balance compensation is made before temperature cycling and small adjustments are made with different type of wire.
Development of multi-bunch beam energy compensation method
A method to compensate for beam loading effects in a multi-bunch beam is under development at Accelerator Test Facility (ATF) in KEK. In this paper we describe the rf high power test for ΔT energy compensation by using the SLED cavities. In this ΔT (early injection and amplitude modulation) energy compensation method, the input waveform into accelerating structure is changed by controlling the rf phase and combining the rf-power from two klystrons with a 3 dB hybrid combiner to compensate multi-bunch beam energy for various beam currents. In this test, an arbitrary waveform was generated by changing the rotating speed of the each klystron phase into the opposite direction and the beam test will be done soon. (author)
This paper describes ORNL's development of an environment for the simulation of robotic manipulators. Simulation includes the modeling of kinematics, dynamics, sensors, actuators, control systems, operators, and environments. Models will be used for manipulator design, proposal evaluation, control system design and analysis, graphical preview of proposed motions, safety system development, and training. Of particular interest is the development of models for robotic manipulators having at least one flexible link. As a first application, models have been developed for the Pacific Northwest Laboratory's Flexible Beam Test Bed (PNL FBTB), which is a 1-Degree-of-Freedom, flexible arm with a hydraulic base actuator. ORNL transferred control algorithms developed for the PNL FBTB to controlling IGRIP models. A robust notch filter is running in IGRIP controlling a full dynamics model of the PNL test bed. Model results provide a reasonable match to the experimental results (quantitative results are being determined) and can run on ORNL's Onyx machine in approximately realtime. The flexible beam is modeled as six rigid sections with torsional springs between each segment. The spring constants were adjusted to match the physical response of the flexible beam model to the experimental results. The controller is able to improve performance on the model similar to the improvement seen on the experimental system. Some differences are apparent, most notably because the IGRIP model presently uses a different trajectory planner than the one used by ORNL on the PNL test bed. In the future, the trajectory planner will be modified so that the experiments and models are the same. The successful completion of this work provides the ability to link C code with IGRIP, thus allowing controllers to be developed, tested, and tuned in simulation and then ported directly to hardware systems using the C language
Compensator configurations for load currents' symmetrization
Rusinaru, D.; Manescu, L. G.; Dinu, R. C.
2016-02-01
This paper approaches aspects regarding the mitigation effects of asymmetries in 3-phase 3-wire networks. The measure consisting in connecting of load current symmetrization devices at the load coupling point is presented. A time-variation of compensators parameters is determined as a function of the time-recorded electrical values. The general sizing principle of the load current symmetrization reactive components is based on a simple equivalent model of the unbalanced 3-phase loads. By using these compensators a certain control of the power components transits is ensured in the network. The control is based on the variations laws of the compensators parameters as functions of the recorded electrical values: [B] = [T]·[M]. The link between compensator parameters and measured values is ensured by a transformation matrix [T] for each operation conditions of the supply network. Additional conditions for improving of energy and efficiency performance of the compensator are considered: i.e. reactive power compensation. The compensator sizing algorithm was implemented into a MATLAB environment software, which generate the time-evolution of the parameters of load current symmetrization device. The input data of application takes into account time-recording of the electrical values. By using the compensator sizing software, some results were achieved for the case of a consumer connected at 20 kV busbar of a distribution substation, during 24 hours measurement session. Even the sizing of the compensators aimed some additional network operation aspects (power factor correction) correlated with the total or major load symmetrizations, the harmonics aspects of the network values were neglected.
Digitally compensated beam current transformer
Kesselman, Martin
2005-01-01
The Spallation Neutron Source (SNS) is being built by a collaboration of six laboratories. Beam current monitors (BCMs) will be used to record the current of H-minus and H-plus beams ranging from 15 mA (tune-up in the Front End and Linac) to over 60A fully accumulated in the Ring and dumped to the load as a single pulse in the Ring to Beam Target (RTBT). The time structure of these beams ranges from 645ns "mini" bunches at the 1.05 MHz ring revolution rate, to an overall 1 ms long macro-pulse. The requirements for the BCMs will depend upon their location within the system. The need to measure individual mini-pulses, examine the characteristics of the chopper edge, as well as the longer average current pulse of the macropulse, or long duration pulses during Linac tuning place wide requirements upon the response of current transformers. To obtain the desired accuracy and resolution, current transformers must have less than 1 ns rise time and droops of 0.1 %/ms. This places a significant design burden on the cur...
Load positioning system with gravity compensation
Hollow, R. H.
1984-01-01
A load positioning system with gravity compensation has a servomotor, position sensing feedback potentiometer and velocity sensing tachometer in a conventional closed loop servo arrangement to cause a lead screw and a ball nut to vertically position a load. Gravity compensating components comprise the DC motor, gears, which couple torque from the motor to the lead screw, and constant current power supply. The constant weight of the load applied to the lead screw via the ball nut tend to cause the lead screw to rotate, the constant torque of which is opposed by the constant torque produced by the motor when fed from the constant current source. The constant current is preset as required by the potentiometer to effect equilibration of the load which thereby enables the positioning servomotor to see the load as weightless under both static and dynamic conditions. Positioning acceleration and velocity performance are therefore symmetrical.
Static and transient beam loading of a synchrotron
In a synchrotron, when the beam induced current is comparable to the driver current, the RF cavity is subjected to beam loading perturbation and corrective steps have to be implemented to regain beam stability. In this paper, the static and transient beam loading will be studied. We first discuss the static beam loading, which includes the cavity detuning condition, the stability condition, and the generator power dissipation. The beam current induced beam phase deviation is used as criterion to study the transient beam loading. The upgraded and the old AGS RF system parameters are used as an example to demonstrate how to choose cavity and generator parameters to satisfy the stability requirements under the beam loading. The dynamic models for the beam loading with beam control, and the beam loading with fast power amplifier feedback are presented and analyzed. It is shown that the beam phase and radial feedbacks alone are insufficient for the transient beam loading compensation, but the fast power amplifier feedback can provide effective correction on the beam loading. The limitation of the fast feedback and the beam loading with tuning and AVC loops are also discussed
A NEW HYSTERESIS COMPENSATION METHOD FOR LOAD CELLS
ZhuZijian; ChenRenwen
2002-01-01
A new hysteresis compensation method is presented.After analyzing the characteristics of strain-gage based load cells under loading & unloading conditions, mathe-matical models are established.A solution to compensate the hysteresis of the load cell by the experiments.It is shown that the method is reliable and can effectively re-duce the hysteresis.
Beam transport and space charge compensation strategies (invited)
Meusel, O., E-mail: o.meusel@iap.uni-frankfurt.de; Droba, M.; Noll, D.; Schulte, K.; Schneider, P. P.; Wiesner, C. [IAP, Goethe University Frankfurt, Frankfurt D-60438 (Germany)
2016-02-15
The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed.
Beam transport and space charge compensation strategies (invited).
Meusel, O; Droba, M; Noll, D; Schulte, K; Schneider, P P; Wiesner, C
2016-02-01
The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed. PMID:26932109
Beam transport and space charge compensation strategies (invited)
The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed
Extraneous torque and compensation control on the electric load simulator
Jiao, Zongxia; Li, Chenggong; Ren, Zhiting
2003-09-01
In this paper a novel motor-drive load simulator based on compensation control strategy is proposed and designed. Through analyzing the torque control system consisting of DC torque motor, PWM module and torque sensor, it is shown that performance of the motor-drive load simulator is possible to be as good as that of the electro-hydraulic load simulator in the range of small torque. In the course of loading, the rotation of the actuator would cause a strong disturbance torque through the motor back-EMF, which produces extraneous torque similar as in electro-hydraulic load simulator. This paper analyzes the cause of extraneous torque inside the torque motor in detail and presents an appropriate compensation control with which the extraneous torque can be compensated and the good performance of the torque control system can be obtained. The results of simulation indicate that the compensation is very effective and the track performance is according with the request.
Study on space charge compensation in negative hydrogen ion beam
Zhang, A. L.; Chen, J. E. [University of Chinese Academy of Sciences, Beijing 100049 (China); State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China); Peng, S. X., E-mail: sxpeng@pku.edu.cn; Ren, H. T.; Zhang, T.; Zhang, J. F.; Xu, Y.; Guo, Z. Y. [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China)
2016-02-15
Negative hydrogen ion beam can be compensated by the trapping of ions into the beam potential. When the beam propagates through a neutral gas, these ions arise due to gas ionization by the beam ions. However, the high neutral gas pressure may cause serious negative hydrogen ion beam loss, while low neutral gas pressure may lead to ion-ion instability and decompensation. To better understand the space charge compensation processes within a negative hydrogen beam, experimental study and numerical simulation were carried out at Peking University (PKU). The simulation code for negative hydrogen ion beam is improved from a 2D particle-in-cell-Monte Carlo collision code which has been successfully applied to H{sup +} beam compensated with Ar gas. Impacts among ions, electrons, and neutral gases in negative hydrogen beam compensation processes are carefully treated. The results of the beam simulations were compared with current and emittance measurements of an H{sup −} beam from a 2.45 GHz microwave driven H{sup −} ion source in PKU. Compensation gas was injected directly into the beam transport region to modify the space charge compensation degree. The experimental results were in good agreement with the simulation results.
Study on space charge compensation in negative hydrogen ion beam
Zhang, A. L.; Peng, S. X.; Ren, H. T.; Zhang, T.; Zhang, J. F.; Xu, Y.; Guo, Z. Y.; Chen, J. E.
2016-02-01
Negative hydrogen ion beam can be compensated by the trapping of ions into the beam potential. When the beam propagates through a neutral gas, these ions arise due to gas ionization by the beam ions. However, the high neutral gas pressure may cause serious negative hydrogen ion beam loss, while low neutral gas pressure may lead to ion-ion instability and decompensation. To better understand the space charge compensation processes within a negative hydrogen beam, experimental study and numerical simulation were carried out at Peking University (PKU). The simulation code for negative hydrogen ion beam is improved from a 2D particle-in-cell-Monte Carlo collision code which has been successfully applied to H+ beam compensated with Ar gas. Impacts among ions, electrons, and neutral gases in negative hydrogen beam compensation processes are carefully treated. The results of the beam simulations were compared with current and emittance measurements of an H- beam from a 2.45 GHz microwave driven H- ion source in PKU. Compensation gas was injected directly into the beam transport region to modify the space charge compensation degree. The experimental results were in good agreement with the simulation results.
Study on space charge compensation in negative hydrogen ion beam
Negative hydrogen ion beam can be compensated by the trapping of ions into the beam potential. When the beam propagates through a neutral gas, these ions arise due to gas ionization by the beam ions. However, the high neutral gas pressure may cause serious negative hydrogen ion beam loss, while low neutral gas pressure may lead to ion-ion instability and decompensation. To better understand the space charge compensation processes within a negative hydrogen beam, experimental study and numerical simulation were carried out at Peking University (PKU). The simulation code for negative hydrogen ion beam is improved from a 2D particle-in-cell-Monte Carlo collision code which has been successfully applied to H+ beam compensated with Ar gas. Impacts among ions, electrons, and neutral gases in negative hydrogen beam compensation processes are carefully treated. The results of the beam simulations were compared with current and emittance measurements of an H− beam from a 2.45 GHz microwave driven H− ion source in PKU. Compensation gas was injected directly into the beam transport region to modify the space charge compensation degree. The experimental results were in good agreement with the simulation results
Compensating tune spread induced by space charge in bunched beams
Litvinenko, V.; Wang, G.
2015-05-03
The effects of space charge play a significant role in modern-day accelerators, frequently constraining the beam parameters attainable in an accelerator or in an accelerator chain. They also can limit the luminosity of hadron colliders operating either at low energies or with sub-TeV high-brightness hadron beams. The latter is applied for strongly cooled proton and ion beams in eRHIC – the proposed future electron-ion collider at Brookhaven National Laboratory. Using an appropriate electron beam would compensate both the tune shift and the tune spread in the hadron beam in a coasting beam. But these methods cannot compensate space charge tune spread in a bunched hadron beam. In this paper we propose and evaluate a novel idea of using a co-propagating electron bunch with mismatched longitudinal velocity to compensate the space charge induced tune-shift and tune spread.
MOTION COMPENSATION FOR WIDE BEAM SAR BASED ON FREQUENCY DIVISION
Zheng Xiaoshuang; Yu Weidong; Li Zaoshe
2008-01-01
Aperture-dependent motion compensation is important for wide beam Synthetic Aperture Radar (SAR) data processing. This paper studies a wide beam motion compensation algorithm based on frequency division. It takes blocks along azimuth dimension in frequency domain and applies an-gle-variant motion compensation in time domain. With this frequency division based motion com-pensation approach,the effects of aperture-dependent residual phase errors are corrected precisely. The rationale and procedure of this algorithm are introduced in detail. Point targets and images of a P-band airborne SAR with motion errors are simulated to validate this algorithm. Compared with the wide beam motion compensation algorithms based on time division,the proposed algorithm has better performance,especially in terms of high-frequency motion errors.
Stancari, Giulio
2014-01-01
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for b...
Beam test of multi-bunch energy compensation system in the accelerator test facility at KEK
A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method with the 2856±4.327 HMz accelerating structures in the accelerator test facility (ATF) at KEK. The 1.54 GeV S-band linac of the ATF was designed to accelerate a multi-bunch beam the consists of 20 bunches with 2.8 ns spacing. The multi-bunch beam with 2.0 x 1010 electrons/bunch has an energy deviation of about 8.5% at the end of the linac due to transient beam loading without ECS. The ATF linac is the injector of the ATF damping ring (DR), whose energy acceptance is ±0.5%. The beam loading compensation system is necessary in the ATF linac for the successful injection of multi-bunch into DR. The rf system of the linac consists of 8 regular rf units with the SLED system and 2 ECS rf units without the SLED system. The accelerating structures of the regular units are driven at 2856 MHz and the 2 ECS structures are operated with slightly different rf frequencies of 2856±4.327 MHz. In the beam test, we have succeeded in compressing the multi-bunch energy spread within the energy acceptance of the DR using ΔF ECS. The principle of the beam loading compensation system of KEK-ATF and the experimental results are described in this paper. (author)
A space charge compensation model for positive DC ion beams
In this paper, we revisit and extend a formula to predict the compensation of space charge in positive DC ion beams of non-relativistic energy, as they are for example found in the injector beam lines of heavy ion accelerator facilities.The original formula was presented in 1975 by Igor Gabovich et al. and takes into account the de-compensation through Coulomb collisions of the primary beam ions and the compensating electrons. We extend its usability to arbitrary (positive) charge states of the ions and non-quasineutral beams.The resulting formula compares well with measurements using a retarding field analyzer and a multi-species generalization of it was incorporated into beam transport simulations using the particle-in-cell code WARP
Voltage Unbalance Compensation with Smart Three-phase Loads
Douglass, Philip; Trintis, Ionut; Munk-Nielsen, Stig
2016-01-01
This paper describes the design, proof-of-concept simulations and laboratory test of an algorithm for controlling active front-end rectifiers to reduce voltage unbalance. Using inputs of RMS voltage, the rectifier controller allocates load unevenly on its 3 phases to compensate for voltage unbala...
Lattice design for head-on beam-beam compensation at RHIC
Montag, C.
2011-03-28
Electron lenses for head-on beam-beam compensation will be installed in IP 10 at RHIC. Compensation of the beam-beam effect experienced at IP 8 requires betatron phase advances of {Delta}{psi} = k {center_dot} {pi} between the proton-proton interaction point at IP 8, and the electron lens at IP 10. This paper describes the lattice solutions for both the BLUE and the YELLOW ring to achieve this goal.
A Novel Control algorithm based DSTATCOM for Load Compensation
R, Sreejith; Pindoriya, Naran M.; Srinivasan, Babji
2015-11-01
Distribution Static Compensator (DSTATCOM) has been used as a custom power device for voltage regulation and load compensation in the distribution system. Controlling the switching angle has been the biggest challenge in DSTATCOM. Till date, Proportional Integral (PI) controller is widely used in practice for load compensation due to its simplicity and ability. However, PI Controller fails to perform satisfactorily under parameters variations, nonlinearities, etc. making it very challenging to arrive at best/optimal tuning values for different operating conditions. Fuzzy logic and neural network based controllers require extensive training and perform better under limited perturbations. Model predictive control (MPC) is a powerful control strategy, used in the petrochemical industry and its application has been spread to different fields. MPC can handle various constraints, incorporate system nonlinearities and utilizes the multivariate/univariate model information to provide an optimal control strategy. Though it finds its application extensively in chemical engineering, its utility in power systems is limited due to the high computational effort which is incompatible with the high sampling frequency in these systems. In this paper, we propose a DSTATCOM based on Finite Control Set Model Predictive Control (FCS-MPC) with Instantaneous Symmetrical Component Theory (ISCT) based reference current extraction is proposed for load compensation and Unity Power Factor (UPF) action in current control mode. The proposed controller performance is evaluated for a 3 phase, 3 wire, 415 V, 50 Hz distribution system in MATLAB Simulink which demonstrates its applicability in real life situations.
Vibration compensating beam scanning interferometer for surface measurement
Jiang, Xiang; Martin, Haydn; Wang, Kaiwei
2007-01-01
Light beam scanning using a dispersive element and wavelength tuning is coupled with fibre-optic interferometry to realize a new surface measurement instrument. The instrument is capable of measuring nano-scale surface structures and form deviation. It features active vibration compensation and a small optical probe size that may be placed remotely from the main apparatus. Active vibration compensation is provided by the multiplexing of two interferometers with near common paths. Closed loop ...
Simulation of wire-compensation of long range beam beam interaction in high energy accelerators
Full text: We present weak-strong simulation results for the effect of long-range beam-beam (LRBB) interaction in LHC as well as for proposed wire compensation schemes or wire experiments, respectively. In particular, we discuss details of the simulation model, instability indicators, the effectiveness of compensation, the difference between nominal and PACMAN bunches for the LHC, beam experiments, and wire tolerances. The simulations are performed with the new code BBTrack. (author)
Baudrenghien, P
2005-01-01
The high intensity regime is reached when the voltage induced by the beam in the RF cavities is of an amplitude comparable to the desired accelerating voltage. In steady state this beam loading can be compensated by providing extra RF power. Transient beam loading occurs at injection or in the presence of a beam intensity that is not uniform around the ring. The transients are periodic at the revolution frequency. Without correction transient beam loading can be very harmful: The stable phase and bucket area will not be equal for all bunches. Strong beam loading often goes in pair with longitudinal instabilities because the RF cavities are a large contributor to the total ring impedance. The low level systems that reduce the effect of the transient beam loading will also increase the threshold intensity of the longitudinal instability caused by the cavity impedance at the fundamental RF frequency. Four classic methods are presented here: Feedforward, RF feedback, long delay feedback and bunch by bunch feedbac...
Beam loading effect on rf system in proton synchrotrons
This report describes the stability of an rf system in the presence of beam loading. The analysis is based on the transfer function method given in F. Pedersen (IEEE Trans. Nucl. Sci. NS-22, 1906 (1975)). First, the Routh-Hurwitz criterion is applied to the analysis of the stability of the rf system with a wideband cavity. Then the simplified model in which the loading effect is treated as a reduction in gain of the phase loop is developed. Secondly, the critical damping criteria of the phase loop in the rf system are derived. These criteria give a stability limit appreciably smaller than that given by the Routh-Hurwitz criterion. Finally, we discussed the technique by which the beam loading effect will be compensated. (author)
Contributions to the mini-workshop on beam-beam compensation in the Tevatron
Shiltsev, V.
1998-02-01
The purpose of the Workshop was to assay the current understanding of compensation of the beam-beam effects in the Tevatron with use of low-energy high-current electron beam, relevant accelerator technology, along with other novel techniques of the compensation and previous attempts. About 30 scientists representing seven institutions from four countries--FNAL, SLAC, BNL, Novosibirsk, CERN, and Dubna were in attendance. Twenty one talks were presented. The event gave firm ground for wider collaboration on experimental test of the compensation at the Tevatron collider. This report consists of vugraphs of talks given at the meeting.
Oscillations of end loaded cantilever beams
Macho-Stadler, E.; Elejalde-García, M. J.; Llanos-Vázquez, R.
2015-09-01
This article presents several simple experiments based on changing transverse vibration frequencies in a cantilever beam, when acted on by an external attached mass load at the free end. By using a mechanical wave driver, available in introductory undergraduate laboratories, we provide various experimental results for end loaded cantilever beams that fit reasonably well into a linear equation. The behaviour of the cantilever beam’s weak-damping resonance response is studied for the case of metal resonance strips. As the mass load increases, a more pronounced decrease occurs in the fundamental frequency of beam vibration. It is important to note that cantilever construction is often used in architectural design and engineering construction projects but current analysis also predicts the influence of mass load on the sound generated by musical free reeds with boundary conditions similar to a cantilever beam.
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it has to be considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the bunch by bunch energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1% p-p, while 5% p-p without compensation. In this conference, we will report our multi-bunch electron beam linac system, the details of energy compensation method using the RF amplitude modulation and the results of beam experiment. (author)
Electron Beam Energy Compensation by Controlling RF Pulse Shape
Kii, T; Kusukame, K; Masuda, K; Nakai, Y; Ohgaki, H; Yamazaki, T; Yoshikawa, K; Zen, H
2005-01-01
We have studied on improvement of electron beam macropulse properties from a thermionic RF gun. Though a thermionic RF gun has many salient features, there is a serious problem that back-bombardment effect worsens quality of the beam. To reduce beam energy degradation by this effect, we tried to feed non-flat RF power into the gun. As a result, we successfully obtained about 1.5 times longer macropulse and two times larger total charge per macropulse. On the other hand, we calculated transient evolution of RF power considering non-constant beam loading. The beam loading is evaluated from time evolution of cathode temperature, by use of one dimensional heat conduction model and electron trajectories' calculations by a particle simulation code. Then we found good agreement between the experimental and calculation results. Furthermore, with the same way, we studied the electron beam output dependence on the cathode radius.
Experimental Studies of Compensation of Beam-Beam Effects with Tevatron Electron Lenses
Shiltsev, V.; /Fermilab; Alexahin, Yu.; Bishofberger, Kip; Kamerdzhiev, V.; Parkhomchuk, V.; Reva, V.; Solyak, N.; Wildman, D.; Zhang, X.-L.; Zimmermann, F.; /Fermilab /Los Alamos /Novosibirsk, IYF /CERN
2008-02-01
Applying the space-charge forces of a low-energy electron beam can lead to a significant improvement of the beam-particle lifetime limit arising from the beam-beam interaction in a high-energy collider [1]. In this article we present the results of various beam experiments with 'electron lenses', novel instruments developed for the beam-beam compensation at the Tevatron, which collides 980-GeV proton and antiproton beams. We study the dependencies of the particle betatron tunes on the electron beam current, energy and position; we explore the effects of electron-beam imperfections and noises; and we quantify the improvements of the high-energy beam intensity and the collider luminosity lifetime obtained by the action of the Tevatron Electron Lenses.
Progress with Tevatron Electron Lens Head-On Beam-Beam Compensation
Tevatron electron lenses have been successfully used to mitigate bunch-to-bunch differences caused by longrange beam-beam interactions. For this purpose, the electron beam with uniform transverse density distribution was used. Another planned application of the electron lens is the suppression of tune spread due to head-on beam-beam collisions. For this purpose, the transverse distribution of the E- beam must be matched to that of the antiproton beam. In 2009, the Gaussian profile electron gun was installed in one of the Tevatron electron lenses. We report on the first experiments with non-linear beam-beam compensation. Discussed topics include measurement and control of the betatron tune spread, importance of the beam alignment and stability, and effect of electron lens on the antiproton beam lifetime.
Method for compensating bellows pressure loads while accommodating thermal deformations
Many metal bellows are used on storage ring vacuum chambers. They allow the ring to accommodate deformations associated with alignment, mechanical assembly and thermal expansion. The NSLS has two such electron storage rings, the VUV ring and the X-Ray ring. Both rings utilize a number of welded metal bellows within the ring and at every beam port. There are provisions for 16 beam ports on the VUV and 28 ports of the X-Ray ring. At each of these locations the bellows are acted on by an external pressure of 1 atmosphere, which causes a 520 lb. reaction at the vacuum chamber beam port and at the beamline flange downstream of the bellows. The use of rigid tie rods across the bellows flanges to support the load is troublesome because most storage ring vacuum chambers are baked in situ to achieve high internal vacuum. Significant forces can develop on components if thermal deformation is restrained and damage could occur
Testing Long-Range Beam-Beam Compensation for the LHC Luminosity Upgrade
Rijoff, T L
2012-01-01
The performance of the Large Hadron Collider (LHC) at CERN and its minimum crossing angle are limited by the effect of long-range beam-beam collisions. A wire compensators can mitigate part of the long-range effects and may allow for smaller crossing angles, or higher beam intensity. A prototype long-range wire compensator could be installed in the LHC by 2014/15. Since the originally reserved position for such a wire compensator is not available for this first step, we explore other possible options. Our investigations consider various longitudinal and transverse locations, different wire shapes, different optics configurations and several crossing angles between the two colliding beams. Simulations are carried out with the weak-strong code BBtrack. New postprocessing tools are introduced to analyse tune footprints and particle stability. In particular, a new method for the Lyapunov coefficient calculation is implemented. Submitted as "Tesi di laurea" at the University of Milano, 2012.
Motion compensation with a scanned ion beam: a technical feasibility study
Kraft Gerhard; Haberer Thomas; Bert Christoph; Grözinger Sven; Rietzel Eike
2008-01-01
Abstract Background Intrafractional motion results in local over- and under-dosage in particle therapy with a scanned beam. Scanned beam delivery offers the possibility to compensate target motion by tracking with the treatment beam. Methods Lateral motion components were compensated directly with the beam scanning system by adapting nominal beam positions according to the target motion. Longitudinal motion compensation to mitigate motion induced range changes was performed with a dedicated w...
Stancari, Giulio
2014-01-01
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Hollow electron beam collimation and halo control were studied as an option to complement the collimation system for the upgrades of the Large Hadron Collider (LHC) at CERN; a conceptual design was recently completed. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compens...
Some Features of Transverse Instability of Partly Compensated Proton Beams
Vadim Dudnikov
2001-10-23
suppression of generation and accumulation of secondary particles is a traditional method for suppression the transverse electron-proton instability: improve the vacuum, use a gap in beam for electron removing, use cleaning electrodes, suppressing secondary emission. But opposite solution is also possible. Transverse e-p instability in proton rings can be damped by increasing beam density and the rate of secondary particles generation above a threshold level, with decrease of the unstable wavelength below a transverse beam size. In high current Proton Storage Rings (PSR) such as, the LANSCE PSR it is possible to reach this island of stability by multiturn, concentrated charge exchange injection without painting and by enhanced generation of secondary plasma. This possibility was demonstrated in smaller scale PSR at the INP, Novosibirisk [1]. Damping of the e-p instability allowed to accumulate a coasting, space charge compensated, circulating proton beam with intensity, corresponding to the Laslett tune shift of {Delta}{nu} = 5 in the ring with original tune of {nu} = 0.85. In the other PSR transverse instability of bunched beam was damped by a simple feed back [2,3]. In this article they discuss experimental observations of transverse instability of proton beams in different accelerators and storage rings and consider methods to damp the instability. The presented experimental dates could be useful for verification of computer simulation tools developed for investigation of space charge effects and beam instabilities in realistic conditions [4,5].
Robust Control for Static Loading of Electro-hydraulic Load Simulator with Friction Compensation
YAO Jianyong; JIAO Zongxia; YAO Bin
2012-01-01
Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation.Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems.The tracking performance of the static loading is studied in this paper.Firstly,the nonlinear mathematical models of the hydraulic load simulator are derived,and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance.Considering the effect of the friction,a LuGre model based friction compensation is synthesized,in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded.The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter.Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy.The tracking performance is summarized by a derived theorem.Experimental results are also obtained to verify the high performance nature of the proposed control strategy.
Motion compensation with a scanned ion beam: a technical feasibility study
Intrafractional motion results in local over- and under-dosage in particle therapy with a scanned beam. Scanned beam delivery offers the possibility to compensate target motion by tracking with the treatment beam. Lateral motion components were compensated directly with the beam scanning system by adapting nominal beam positions according to the target motion. Longitudinal motion compensation to mitigate motion induced range changes was performed with a dedicated wedge system that adjusts effective particle energies at isocenter. Lateral compensation performance was better than 1% for a homogeneous dose distribution when comparing irradiations of a stationary radiographic film and a moving film using motion compensation. The accuracy of longitudinal range compensation was well below 1 mm. Motion compensation with scanned particle beams is technically feasible with high precision
Beam-beam compensation studies in the Tevatron with electron lenses
Stancari, Giulio
2013-01-01
At the Fermilab Tevatron collider, we studied the feasibility of suppressing the antiproton head-on beam-beam tune spread using a magnetically confined 5-keV electron beam with Gaussian transverse profile overlapping with the circulating beam. When electron cooling of antiprotons was applied in regular Tevatron operations, the nonlinear head-on beam-beam effect on antiprotons was small. Therefore, we first focused on the operational aspects, such as beam alignment and stability, and on fundamental observations of tune shifts, tune spreads, lifetimes, and emittances. We also attempted two special collider stores with only 3 proton bunches colliding with 3 antiproton bunches, to suppress long-range forces and enhance head-on effects. We present here the results of this study and a comparison between numerical simulations and observations. These results contributed to the application of this compensation concept to RHIC at Brookhaven.
Siebert, Jan; Geimer, Marcus [Hrsg.
2016-01-01
In spite of their high technical maturity, load sensing systems (LS) have system-inherent energy losses that are largely due to the operation of parallel actuators with different loads at the same pressure level. Hereby, the pressure compensators of the system are crucial. So far, excessive hydraulic energy has been throttled at these compensators and been discharged as heat via the oil. The research project “Reduction of System Inherent Pressure Losses at Pressure Compensators of Hydraulic L...
Impact loads on beams on elastic foundations
Quite often, complex structural components are idealised as beams in engineering analysis and design. Also, equations governing the responses of shallow shells are mathematically equivalent to the equations governing the responses of beams on elastic foundations. Hence with possible applications in several technical disciplines, the behaviour of beams on elastic foundations subjected to impact loads is studied in detail in the present investigation both analytically and experimentally. The analytical methods include analysis and energy method. The effect of foundation parameters (stiffness, and damping constants) on the dynamic responses of the beam-foundation system has been analysed. In modal analysis, the free-vibration equation has been solved by replacing the applied impulse by suitable initial conditions and the solution has been obtained as the linear combination of an infinite sequence of discrete eigen-vectors. In the energy method, the beam-foundation system is treated to be under forced vibrations and the forcing function has been obtained using the Hertz's law of impact. In the case of free-free end conditions of the beam, the rigid body modes and the elastic modes have been superposed to obtain the total response. The responses predicted using modal analysis are higher than those obtained using energy method. From the present study it is observed that model analysis is preferable to energy method. (Auth.)
Tsai, Hsiu-Wen; Davenport, Paul W.
2014-01-01
Respiratory load compensation is a sensory-motor reflex generated in the brain stem respiratory neural network. The nucleus of the solitary tract (NTS) is thought to be the primary structure to process the respiratory load-related afferent activity and contribute to the modification of the breathing pattern by sending efferent projections to other structures in the brain stem respiratory neural network. The sensory pathway and motor responses of respiratory load compensation have been studied...
Improvements of the undulator spectral performance by compensating the backing beam deflection
This study thoroughly examines how the backing beam deflection affects the undulator spectral performance. Reduction of the undulator spectral intensity owing to backing beam deflection is analytically evaluated based on plane-wave approximation. The results reveal that the amplitude and the slope of the backing beam deflection affect the undulator spectral performance. Provided is a novel figure-of-merit, rms of the regressed accumulated gap deviation, to determine the backing beam deflection budget. An example of a 3.9 m undulator supporting carriage mounted with 50-mm period length undulator magnet (U5) under a maximum magnetic loading of 5 metric tons at a minimum operating gap of 14 mm, is provided. Its mechanical features are first examined via 3D commercial finite element code ANSYS that concludes the backing beam deflection is influenced heavily by the rigidity of the undulator support frames. Examining the corresponding spectral performance shows that significantly diminishing the undulator spectral degradation by backing beam deflection is attainable by compensating the deflection at the undulator minimum operating gap properly. The numerical results agree well with those deduced from the measured magnetic field of the as-built undulator
Beam loading in magnicon deflection cavities
Hafizi, B. [ICARUS Research, Inc., Bethesda, MD (United States); Gold, S.H. [Naval Research Lab., Washington, DC (United States). Plasma Physics Div.
1997-02-01
The radio frequency (RF) source for the next linear collider (NLC) is required to generate a power of 1/2--1 GW per tube in a 200-ns pulse, or 100--200 J of energy in a pulse of up to a few {micro}s in duration, at a frequency of 10--20 GHz. A variety of RF sources are under investigation at the present time aimed at fulfilling the needs of the NLC. These include the X-band klystron, Gyroklystron, traveling-wave tube, harmonic convertor, chopper-driven traveling-wave tube, and magnicon. Here, analysis of the beam-deflection cavity interaction in a magnicon is presented and compared with experiment. For a driven cavity a dispersion relation is obtained wherein the interaction modifies the cold-cavity factor and the resonance frequency. In terms of a lumped-parameter equivalent circuit the interaction corresponds to a complex-values beam admittance Y{sub b} in parallel with the cavity admittance. The response of the gain cavities is modified by the same admittance. In a magnicon, Y{sub b} is a sensitive function of the solenoidal focusing magnetic field B{sub 0}, thus providing a convenient means of adjusting the cavity properties in experiments. When the relativistic gyrofrequency is twice the drive frequency, ImY{sub b} = 0 and the beam does not load the cavity. Analytical expressions of the variation of the detuning, instantaneous bandwidth (i.e., loaded quality factor) and gain with B{sub 0} are derived. Simulation results are presented to verify the linear analysis with ideal beams and to illustrate the modifications due to finite beam emittance. Results of the magnicon experiment at the Naval Research Laboratory are examined in the light of the analysis.
The damped oscillating propagation of the compensating self-accelerating beams
Liu, Wei-Wei; Yu, Pan-Pan; Wang, Hao-wei; Wang, Zi-qiang; Li, Yin-Mei
2016-01-01
We report a new form of compensating accelerating beam generated by amplitude modulation of the symmetric Airy beam (SAB) caustics with an exponential apodization mask. Our numerical study manifests that the compensating beam is with one main-lobe beam structure and can maintain the mean-intensity invariant both in the free space and loss media. Specially, the beam inherits the beamlets structure from the SAB and owns a novel damped oscillating propagation property. We also conduct a comparative study of its propagation property with that of the Airy beam theoretically. And by altering the signs of 2D masks, the main lobe of the compensating beam can be modulated to orientate in four different quadrants flexibly. The proposed compensating accelerating beam is anticipated to get special applications in particle manipulation or plasmas regions.
Method of beam steering with FWM in ICF. Compensation and generation of a PC beam for a foam target
In beam steering with a phase conjugate (PC) mirror in inertial fusion energy (ICF), the path of the PC beam has to be compensated since the target moves several hundred micrometers during beam propagation. In this paper we show that compensation can be achieved by adjusting the angle between two pump beams in four-wave mixing (FWM) used as a PC mirror. The compensation angle depends on the target position along the optical axis, focal point of the final optics, and angle adjusted with FWM. For the parameter values of GEKKO XII and an accuracy of laser irradiation of ±10 µm, the compensation angle is 4.5 mrad and the margin of error for target injection is ±0.3 mm. We also show that a PC beam can be generated from the beam scattered by a foam target rotating at ∼ 43 m/s is confirmed. (author)
Issues in respiratory motion compensation during external-beam radiotherapy
Purpose: To investigate how respiration influences the motion of lung and pancreas tumors and to relate the observations to treatment procedures intended to improve dose alignment by predicting the moving tumor's position from external breathing indicators. Methods and materials: Breathing characteristics for five healthy subjects were observed by optically tracking the displacement of the chest and abdomen, and by measuring tidal air volume with a spirometer. Fluoroscopic imaging of five radiotherapy patients detected the motion of lung and pancreas tumors synchronously with external breathing indicators. Results: The external and fluoroscopic data showed a wide range of behavior in the normal breathing pattern and its effects on the position of lung and pancreas tumors. This included transient phase shifts between two different external measures of breathing that diminished to zero over a period of minutes, modulated phase shifts between tumor and chest wall motion, and other complex phenomena. Conclusions: Respiratory compensation strategies that infer tumor position from external breathing signals, including methods of beam gating and dynamic beam tracking, require three-dimensional knowledge of the tumor's motion trajectory as well as the ability to detect and adapt to transient and continuously changing characteristics of respiratory motion during treatment
Dynamics of relativistic electron beam space charge compensation in a neutral gas
Kurilko, V.I.; Ognivenko, V.V.
1983-06-01
The dynamics of the space charge compensation of a relativistic electron beam with magnetized electrons as a result of ionization collisions of beam electrons and secondary ions with gas atoms has been studied theoretically. The analysis of calculation data shows that the neutral gas ionization by a relativistic electron beam leads to appearance of secondary ions which oscillate in a potential well of the electron beam space charge. It is shown that the density of ions formed is maximal in the beam center and drops to the beam periphery. As a result, the force compensation is possible only in the vicinity of a fixed coordinate which value grows with time.
Mingchao Xia; Yanhui Mao
2013-01-01
Control strategies of D-STATCOM for unbalanced load compensation under internal and external disturbances were discussed. Linear control strategies do not have a satisfactory dynamic performance and become invalid under internal or external disturbances. To guarantee a good precision and robustness, a control strategy combining input-output feedback linearization technique with integral sliding mode control (ISMC) method was applied to D-STATCOM for unbalanced load compensation. The strategy ...
Duration of Load Effects on Different Sized Timber Beams
Andreasen, Lotte; Hoffmeyer, Preben
1997-01-01
This is the final report submitted to EC in connection with a project on duration of load. The report contains the results of the experimental work on duration of load for beams and notched beams of LVL and of glulam. The report also contains experimental results from duration of load experiments...
Key elements of space charge compensation on a low energy high intensity beam injector.
Peng, Shixiang; Lu, Pengnan; Ren, Haitao; Zhao, Jie; Chen, Jia; Xu, Yuan; Guo, Zhiyu; Chen, Jia'er; Zhao, Hongwei; Sun, Liangting
2013-03-01
Space charge effect (SCE) along the beam line will decrease beam quality. Space charge compensation (SCC) with extra gas injection is a high-efficiency method to reduce SCE. In this paper, we will report the experimental results on the beam profile, potential distribution, beam emittance, and beam transmission efficiency of a 35 keV∕90 mA H(+) beam and a 40 keV∕10 mA He(+) beam compensated by Ar∕Kr. The influence of gas type, gas flow, and injection location will be discussed. Emphasis is laid on the consideration of SCC when designing and commissioning a high intensity ion beam injector. Based on measured data, a new definition of space charge compensation degree is proposed. PMID:23556812
Key elements of space charge compensation on a low energy high intensity beam injector
Peng Shixiang; Lu Pengnan; Ren Haitao; Zhao Jie; Chen Jia; Xu Yuan; Guo Zhiyu; Chen Jia' er [Institution of Nuclear Science and Technology (INST), State Key Laboratory of Nuclear Physics and Technology (KLNPT), Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China); Zhao Hongwei; Sun Liangting [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)
2013-03-15
Space charge effect (SCE) along the beam line will decrease beam quality. Space charge compensation (SCC) with extra gas injection is a high-efficiency method to reduce SCE. In this paper, we will report the experimental results on the beam profile, potential distribution, beam emittance, and beam transmission efficiency of a 35 keV/90 mA H{sup +} beam and a 40 keV/10 mA He{sup +} beam compensated by Ar/Kr. The influence of gas type, gas flow, and injection location will be discussed. Emphasis is laid on the consideration of SCC when designing and commissioning a high intensity ion beam injector. Based on measured data, a new definition of space charge compensation degree is proposed.
Long-Range And Head-On Beam-Beam Compensation Studies in RHIC With Lessons for the LHC
Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G.; /Brookhaven; Dorda, U.; Koutchouk, J.P.; Sterbini, G.; Zimmermann, F.; /CERN; Kim, H.J.; Sen, T.; Shiltsev, V.; Valishev, A.; /Fermilab; Qiang, J.; /LBL, Berkeley; Kabel, A.; /SLAC
2011-11-28
Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
An Alternative High Luminosity LHC with Flat Optics and Long-Range Beam-Beam Compensation
AUTHOR|(CDS)2070952; Valishev, Aleksander; Shatilov, Dmitry
2015-01-01
In the baseline scenario of the High-Luminosity LHC (HL-LHC), the geometric loss of luminosity in the two high luminosity experiments due to collisions with a large crossing angle is recovered by tilting the bunches in the interaction region with the use of crab cavities. A possible backup scenario would rely on a reduced crossing angle together with flat optics (with different horizontal and vertical β∗ values) for the preservation of luminosity performance. However, the reduction of crossing angle coupled with the flat optics significantly enhances the strength of long-range beam-beam interactions. This paper discusses the possibility to mitigate the long-range beam-beam effects by current bearing wire compensators (or e-lens). We develop a new HL-LHC parameter list and analyze it in terms of integrated luminosity performance as compared to the baseline. Further, we evaluate the operational scenarios using numerical simulations of single-particle dynamics with beam-beam effects.
An Alternative High Luminosity LHC with Flat Optics and Long-Range Beam-Beam Compensation
Fartoukh, Stephane [CERN; Valishev, Alexander [Fermilab; Shatilov, Dmitry [BINP, Novosibirsk
2015-06-01
In the baseline scenario of the High-Luminosity LHC (HL-LHC), the geometric loss of luminosity in the two high luminosity experiments due to collisions with a large crossing angle is recovered by tilting the bunches in the interaction region with the use of crab cavities. A possible backup scenario would rely on a reduced crossing angle together with flat optics (with different horizontal and vertical $\\beta^{\\ast}$values) for the preservation of luminosity performance. However, the reduction of crossing angle coupled with the flat optics significantly enhances the strength of long-range beam-beam interactions. This paper discusses the possibility to mitigate the long-range beam-beam effects by current bearing wire compensators (or e-lens). We develop a new HL-LHC parameter list and analyze it in terms of integrated luminosity performance as compared to the baseline. Further, we evaluate the operational scenarios using numerical simulations of single-particle dynamics with beam-beam effects.
Fartoukh, Stéphane; Valishev, Alexander; Papaphilippou, Yannis; Shatilov, Dmitry
2015-12-01
Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of β* and type of optics (flat or round), and possible compensation or additive effects between several low-β insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the long-range beam-beam effects [J. P. Koutchouk, CERN Report No. LHC-Project-Note 223, 2000], therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the final focus quadrupoles. In this paper, a semianalytical approach is developed for the compensation of the long-range beam-beam interactions with current wires. This reveals the possibility of achieving optimal correction through a careful adjustment of the aspect ratio of the β functions at the wire position. We consider the baseline luminosity upgrade plan of the Large Hadron Collider (HL-LHC project), and compare it to alternative scenarios, or so-called "configurations," where modifications are applied to optics, crossing angle, or orientation of the crossing plane in the two low-β insertions of the ring. For all these configurations, the beneficial impact of beam-beam compensation devices is then demonstrated on the tune footprint, the dynamical aperture, and/or the frequency map analysis of the nonlinear beam dynamics as the main figures of merit.
Impact load mitigation in sandwich beams using local resonators
Sharma, B.; Sun, C.T.
2015-01-01
Dynamic response of sandwich beams with resonators embedded in the cores subjected to impact loads is studied. Using finite element models the effectiveness of various local resonator frequencies under a given impact load is compared to the behavior of an equivalent mass beam. It is shown that addition of appropriately chosen local resonators into the sandwich beam is an effective method of improving its flexural bending behavior under impact loads. The effect of a given local resonance frequ...
Accuracy of a 3D online motion compensation system for tumor therapy with scanned ion beams
An integrated three-dimensional online motion compensation (3DOMC) system is being developed at GSI to treat tumors in moving organs with scanned ion beams. Target motion is detected by a laser distance sensor, and the motion compensation parameters are calculated in a dedicated module of the treatment control system (TCS). The lateral compensation parameters are sent to the TCS controller of the scanning magnets to adapt the beam laterally. The longitudinal compensation parameters are sent to a range shifter which consists of two sets of PMMA wedges mounted on linear motors. The wedges are placed symmetrically to form a double wedge with a homogeneous thickness in the overlapped area. By moving the wedges apart or together with the linear motors the range of the traversing ion beams can be modulated. The system response time has been optimized to ∼1ms for lateral compensation and to ∼25 ms for 5 mm water equivalent depth compensation. In experiments with a position detector deviations of 0.3 mm RMS were measured for lateral motion compensation by comparing measured and nominal beam positions. For longitudinal compensation an accuracy of 0.2(2) mm was obtained by comparing stationary depth dose profiles to those with motion compensation
Manipulation of orbital angular momentum beams based on space diffraction compensation.
Zhou, Hailong; Dong, Jianji; Yan, Siqi; Zhou, Yifeng; Shi, Lei; Zhang, Xinliang
2014-07-28
We put forward a technique to manipulate the size of orbital angular momentum (OAM) beams based on space diffraction compensation. Paraxial Fresnel diffraction which carries a negative spatial quadratic phase distribution can be regarded as a negative diffractive effect. To compensate the negative diffraction, we employ a 4f Fourier lens system containing a phase mask to generate an inverse quadratic phase. The size of OAM beams can be easily controlled by designing the phase mask profile without changing the OAM. The applications of space diffraction compensation in OAM demultiplexing, ring fiber coupling for OAM beams and optical manipulation of micro particles are also discussed. PMID:25089395
Analysis and Control of STATCOM/SMES Compensator in a Load Variation Conditions
Mahmoud Reza Shakarami
2014-01-01
Full Text Available The utilization of Flexible AC Transmission System (FACTS devices in a power system can potentially overcome limitations of the present mechanically controlled transmission system. Also, the advanced technology makes it possible to include new energy storage devices in the electrical power system. The integration of Superconducting Magnetic Energy Storage (SMES into Static Synchronous Compensator (STATCOM can lead to increase their flexibility to improve power system dynamic behavior by exchanging both active and reactive powers with power grids. This paper describes structure and behavior of STATCOM/SMES compensator in power systems. A control strategy based on direct Lyapanov method for compensator is used. Moreover, the performance of the STATCOM/SMES compensator in a load variation condition is evaluated by PSCAD/EMTDC software in test system. Also, SMES capacity effects on integrated compensator are investigated.
Coupling Dynamics Interlip Coordination in Lower Lip Load Compensation
van Lieshout, Pascal; Neufeld, Chris
2014-01-01
Purpose: To study the effects of lower lip loading on lower and upper lip movements and their coordination to test predictions on coupling dynamics derived from studies in limb control. Method: Movement data were acquired using electromagnetic midsagittal articulography under 4 conditions: (a) without restrictions, serving as a baseline; (b) with…
Compensation for Adolescents’ School Mental Load by Physical Activity on Weekend Days
Michal Kudláček
2016-03-01
Full Text Available Introduction and objective: Increasing mental load and inadequate stress management significantly affect the efficiency, success and safety of the educational/working process in adolescents. The objective of this study is to determine the extent that adolescents compensate for their school mental load by physical activity (PA on weekend days and, thus, to contribute to the objective measurement of mental load in natural working conditions. Methods: A cross-sectional study was conducted between September 2013 and April 2014. A set of different methods was employed—self-administered questionnaire (IPAQ-long questionnaire, objective measurements—pedometers, and accelerometers (ActiTrainers. They was distributed to 548 students from 17 high schools. Participants’ mental load was assessed based on the difference between PA intensity and/or physical inactivity and heart rate range. Results: The participants with the highest mental load during school lessons do not compensate for this load by PA on weekend days. Conclusions: Adolescents need to be encouraged to be aware of their subjective mental load and to intentionally compensate for this load by PA on weekend days. It is necessary to support the process of adopting habits by sufficient physical literacy of students, as well as teachers, and by changes in the school program.
Ion-optically driven depth compensation for ion beam tracking
The beam delivery system for scanned carbon ion beam radiotherapy at GSI has been extended in research mode to irradiate moving targets. For beam tracking, the ion beam is adapted laterally as well as in range corresponding to the target's three dimensional (3D) motion. A beam tracking system with a motorized double wedge system for fast and accurate range adaptation has been developed. In addition to the current range adaptation system a much faster method for online energy modulation is being investigated where a fine focused ion beam is dynamically positioned, controlled by fast dipole magnets, on a small static wedge shaped absorber within the beam line. Experiments were performed at the therapy beam line to study the beam shift from central axis by the first dipole magnet up to the maximum limit where the beam can be deflected back to central axis by the second dipole magnet. Beam profiles were measured at different locations of the beam delivery system. The particle transmission was measured as well at the target position. Experiments were supported by Monte Carlo simulations for energy variation studies and for assessing the influence on beam profiles using MOCADI code
Studies of beam injection with a compensated bump and uncompensated bump in a synchrotron
Synchrotron radiation sources Indus-1 and Indus-2 have a synchrotron as the common injector. A three kicker compensated bump injection scheme was employed for beam injection into this synchrotron. The stored beam current in the synchrotron is higher, when all the three kickers are operated at the same current than when kickers are operated at currents required to generate compensated bump. Beam dynamics studies have been done to understand why this happens. Theoretical studies indicate that higher stored current in the later case is attributed to smaller residual oscillations of injected beam. These studies also reveal that if the angle of the injected beam during beam injection is kept varying, the performance could be further improved. This is experimentally confirmed by injecting the beam on rising part of the injection septum magnet current pulse
Studies of beam injection with a compensated bump and uncompensated bump in a synchrotron
Akbar Fakhri, Ali; Prajapati, S. K.; Ghodke, A. D.; Singh, Gurnam [Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)
2013-08-15
Synchrotron radiation sources Indus-1 and Indus-2 have a synchrotron as the common injector. A three kicker compensated bump injection scheme was employed for beam injection into this synchrotron. The stored beam current in the synchrotron is higher, when all the three kickers are operated at the same current than when kickers are operated at currents required to generate compensated bump. Beam dynamics studies have been done to understand why this happens. Theoretical studies indicate that higher stored current in the later case is attributed to smaller residual oscillations of injected beam. These studies also reveal that if the angle of the injected beam during beam injection is kept varying, the performance could be further improved. This is experimentally confirmed by injecting the beam on rising part of the injection septum magnet current pulse.
Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions
Valerio-Lizarraga, Cristhian A., E-mail: cristhian.alfonso.valerio.lizarraga@cern.ch [CERN, Geneva (Switzerland); Departamento de Investigación en Física, Universidad de Sonora, Hermosillo (Mexico); Lallement, Jean-Baptiste; Lettry, Jacques; Scrivens, Richard [CERN, Geneva (Switzerland); Leon-Monzon, Ildefonso [Facultad de Ciencias Fisico-Matematicas, Universidad Autónoma de Sinaloa, Culiacan (Mexico); Midttun, Øystein [CERN, Geneva (Switzerland); University of Oslo, Oslo (Norway)
2014-02-15
The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H{sup −} beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.
Transient beam loading in the SLC Damping Rings
Effects arising from heavy beam loading in the Stanford Linear Collider (SLC) Damping Rings are described. The stability of the rf system and particle beam is studied using a numerical model of the beam cavity interaction with multiple feedback loops. Nonlinearities of the power source are also considered. The effects of beam-induced transients and intensity jitter on the rf system are analyzed and used to determine stability tolerances for both high current and low current pulses
On compensating tune spread induced by space charge in bunched beams
Litvinenko V. N.; Wang, G.
2014-05-09
Space charge effects play significant role in modern-day accelerators. These effects frequently constrain attainable beam parameters in an accelerator, or, in an accelerator chain. They also could limit the luminosity of hadron colliders operating either at low energies or with a sub-TeV high brightness hadron beams. The latter is applied for strongly cooled proton and ion beams in eRHIC – the proposed future electron-ion collider at Brookhaven National Laboratory. A number of schemes for compensating space charge effects in a coasting (e.g. continuous) hadron beam were proposed and some of them had been tested. Using a proper transverse profile of the electron beam (or plasma column) for a coasting beam would compensate both the tune shift and the tune spread in the hadron beam. But all of these methods do not address the issue of tune spread compensation of a bunched hadron beam, e.g. the tune shift dependence on the longitudinal position inside the bunch. In this paper we propose and evaluate a novel idea of using a co-propagating electron bunch with miss-matched longitudinal velocity to compensate the space charge induced tune-shift and tune spread. We present a number of practical examples of such system.
de Rooij, Michael Andrew; Steigerwald, Robert Louis; Delgado, Eladio Clemente
2008-12-16
Photovoltaic power converter system including a controller configured to reduce load harmonics is provided. The system comprises a photovoltaic array and an inverter electrically coupled to the array to generate an output current for energizing a load connected to the inverter and to a mains grid supply voltage. The system further comprises a controller including a first circuit coupled to receive a load current to measure a harmonic current in the load current. The controller includes a second circuit to generate a fundamental reference drawn by the load. The controller further includes a third circuit for combining the measured harmonic current and the fundamental reference to generate a command output signal for generating the output current for energizing the load connected to the inverter. The photovoltaic system may be configured to compensate harmonic currents that may be drawn by the load.
Application of Load Compensation in Voltage Controllers of Large Generators in the Polish Power Grid
Bogdan Sobczak
2014-03-01
Full Text Available The Automatic Voltage Regulator normally controls the generator stator terminal voltage. Load compensation is used to control the voltage which is representative of the voltage at a point either within or external to the generator. In the Polish Power Grid (PPG compensation is ready to use in every AVR of a large generator, but it is utilized only in the case of generators operating at the same medium voltage buses. It is similar as in most European Power Grids. The compensator regulating the voltage at a point beyond the machine terminals has significant advantages in comparison to the slower secondary Voltage and Reactive Power Control System (ARNE1. The compensation stiffens the EHV grid, which leads to improved voltage quality in the distribution grid. This effect may be particularly important in the context of the dynamic development of wind and solar energy.
Mingchao Xia
2013-01-01
Full Text Available Control strategies of D-STATCOM for unbalanced load compensation under internal and external disturbances were discussed. Linear control strategies do not have a satisfactory dynamic performance and become invalid under internal or external disturbances. To guarantee a good precision and robustness, a control strategy combining input-output feedback linearization technique with integral sliding mode control (ISMC method was applied to D-STATCOM for unbalanced load compensation. The strategy has features of simple structure and is easy to implement. A 10 MVar/10 kV D-STATCOM simulation system was built in PSCAD/EMTDC to verify the effectiveness and robustness of the control strategy proposed. Simulation results show that the control strategy can compensate reactive power and eliminate unbalance simultaneously under various disturbances.
On Linear Power Factor Compensation, Power Equalization and Cyclo–dissipativity of Nonlinear Loads
Puerto-Flores, Dunstano del; Scherpen, Jacquelien M.A.; Ortega, Romeo
2010-01-01
The main contribution of this paper is an extension of the recently introduced result that recasts the problem of power factor compensation for nonlinear loads with non-sinusoidal source voltage in terms of the property of cyclo–dissipativity. Using the cyclo–dissipativity framework the classical ca
Lettl, J.; Šimek, Petr; Valouch, Viktor
Prague: Electromagnetics Academy, 2015, s. 2500-2505. ISSN 1559-9450. [Progress In Electromagnetics Research Symposium Proceedings. Prague (CZ), 06.07.2015-09.07.2015] Institutional support: RVO:61388998 Keywords : disturbed load * GNP (Generalized Non-active Power) * parallel compensation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering www.piers.org
Partial loss compensation in dielectric-loaded plasmonic waveguides at near infra-red wavelengths
Garcia, Cesar; Coello, Victor; Han, Zhanghua;
2012-01-01
We report on the fabrication and characterization of straight dielectric-loaded surface plasmon polaritons waveguides doped with lead-sulfide quantum dots as a near infra-red gain medium. A loss compensation of ~33% (an optical gain of ~143 cm^−1) was observed in the guided mode. The mode propaga...
Lightweight Aggregate Concrete Beams. Load-bearing Capacity
Larsen, Henning; Goltermann, Per; Ingholt, N.U.
1997-01-01
This paper deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents formulas for the moment capacity as well as the shear force capacity.......This paper deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents formulas for the moment capacity as well as the shear force capacity....
Impact load mitigation in sandwich beams using local resonators
Sharma, B
2015-01-01
Dynamic response of sandwich beams with resonators embedded in the cores subjected to impact loads is studied. Using finite element models the effectiveness of various local resonator frequencies under a given impact load is compared to the behavior of an equivalent mass beam. It is shown that addition of appropriately chosen local resonators into the sandwich beam is an effective method of improving its flexural bending behavior under impact loads. The effect of a given local resonance frequency under different impact load durations is also studied. It is demonstrated that the choice of appropriate local resonance frequency depends on the impact duration. Further, by performing transverse impact experiments, the finite element models are verified and the advantage of using internal resonators under impact loading conditions is demonstrated.
Tada, M; Mitani, Yasunori; K. Tsuji
1995-01-01
This paper describes a load change compensation by a superconducting magnetic energy storage (SMES) which is assumed to be installed in a power system for power system stabilization. A simultaneous control strategy of SMES for load change compensation as well as for power system stabilization in a longitudinally interconnected power system is derived. Several numerical examples demonstrate the significant effectiveness of the SMES
Rf beam loading in the Brookhaven AGS with booster injection
Multi-batch bunched beam loading during injection from the Booster to the AGS will be discussed. The full intensity beam injection to the upgraded AGS rf system with beam phase and radial feedbacks will be studied. It is shown that a beam phase feedback is necessary in order to guarantee a predictable hewn behavior after the first batch injection, otherwise the initial phase deviation for the following batch injections cannot be controlled. However, the effectiveness of the phase feedback control of the transient beam loading may be limited by an emittance blow up in the process. It is shown that a fast power amplifier feedback with a moderate gain can significantly reduce the transient effect of the bunched beam injection
A Novel Hybrid Dstatcom Topology for Load Compensation with Non-Stiff Source
M Guru Dasthagiri Reddy
2014-09-01
Full Text Available The distribution static compensator (DSTATCOM is a shunt active filter, which injects currents into the point of common coupling (PCC (the common point where load, source, and DSTATCOM are connected such that the harmonic filtering, power factor correction, and load balancing can be achieved. The distribution static compensator (DSTATCOM is used for load compensation in power distribution network. A new topology for DSTATCOM applications with non-stiff source is proposed. The proposed topology enables DSTATCOM to have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the average switching frequency of the insulated gate bipolar transistor switches of the D-STATCOM is also reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out using MATLAB environment and the results analyzed.
Load Torque Compensator for Model Predictive Direct Current Control in High Power PMSM Drive Systems
Preindl, Matthias; Schaltz, Erik
2011-01-01
The widely used cascade speed and torque controllers have a limited control performance in most high power applications due to the low switching frequency of power electronic converters and the convenience to avoid speed overshoots and oscillations for lifetime considerations. Model Predictive...... further improve dynamic behavior. It compensates the load torque influence on the speed control setting a feed forward torque reference value. The benefits are twice; the speed controller reaches the speed reference value without offsets which would need to be compensated by an integrator and a better...
Load Torque Compensator for Model Predictive Direct Current Control in High Power PMSM Drive Systems
Preindl, Matthias; Schaltz, Erik
2010-01-01
In drive systems the most used control structure is the cascade control with an inner torque, i.e. current and an outer speed control loop. The fairly small converter switching frequency in high power applications, e.g. wind turbines lead to modest speed control performance. An improvement bring...... dynamic behaviour. It compensates the load torque influence on the speed control setting a feed forward torque value, i.e. current reference value. The benefits are twice. The speed controller reaches immediately the speed reference value avoiding offsets which must be compensated by the weak integrator...
Energy recuperation of intense proton beam compensated by slow electrons
Experimental studies of direct transformation (recuperation) of intense ion beam energy are described. In a recuperator low-energy electrons of a beam are separated by a grid unit and ions are detected by one of the three types of collectors: plane, ''Faraday cylinder'' with a grid in the input hole and without it. The transformation of proton beam energy with current density up to 150 mA/cm2 at current pulse duration of 300 μ and power of ∼ 0.5 kW is realized with the efficiency of 70%, at power up to 30 kW - with the efficiency of about 50%. The investigation results can be used for the development of recuperation systems in thermonuclear facilities
Effect of ion compensation of the beam space charge on gyrotron operation
In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations
Effect of ion compensation of the beam space charge on gyrotron operation
Fokin, A. P.; Glyavin, M. Yu.; Nusinovich, G. S.
2015-04-01
In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.
Effect of ion compensation of the beam space charge on gyrotron operation
Fokin, A. P.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Nusinovich, G. S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)
2015-04-15
In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.
A statistical approach to motion compensated cone-beam
Lyksborg, Mark; Hansen, Mads Fogtmann; Larsen, Rasmus
One of the problems arising in radiotherapy planning is the quality of CT planning data. In the following attention is giving to the cone-beam scanning geometry where reconstruction of a 3D volume based on 2D projections, using the classic Feldkamp-Davis-Kress (FDK) algorithm requires a large...
A Statistical Approach to Motion Compensated Cone Beam Reconstruction
Lyksborg, Mark; Hansen, Mads Fogtmann; Larsen, Rasmus
One of the problems arising in radiotherapy planning is the quality of CT planning data. In the following attention is giving to the cone-beam scanning geometry where reconstruction of a 3D volume based on 2D projections, using the classic Feldkamp-Davis-Kress (FDK) algorithm requires a large...
Fu, Shiyao; Zhang, Shikun; Wang, Tonglu; Gao, Chunqing
2016-07-15
We propose a scheme that uses a probe Gaussian beam and the Gerchberg-Saxton (GS) algorithm to realize the pre-turbulence compensation of beams carrying orbital angular momentum (OAM). In the experiment, spatial light modulators are utilized to simulate the turbulent atmosphere and upload the retrieval holograms. A probe Gaussian beam is used to detect the turbulence. Then, the retrieval holograms, which can correct the phase distortion of the OAM beams, are obtained by the GS algorithm. The experimental results show that single or multiplexed OAM beams can be compensated well. The compensation performances under different iterations are also analyzed. PMID:27420491
Emittance growth and space-charge compensation in the transport of intense ion beams
The aim of the GSI transport experiment was the study of the periodic beam transport at space-charge dominated and at partially compensated ion beams. For this purpose a periodic transport channel was constructed which consisted of 6 periods with each two alternatingly poled magnetic quadrupoles. Faraday cups and beam transformers were available for current measurements. At the entrance and the end of the channel the emittances were measured in both transverse planes. The measurements were performed with Ar1+ ions and an energy of 190 keV. The ion currents lied between some μA and 5 mA. The quantity of the rms emittance could be varied from 0.5 mm.mrad to 15 mm.mrad. In agreement with the theoretical considerations the measurement results show that the compensation of the space charge of an ion beam sets on successively. (orig./HSI)
CHANG Min; PENG Dan; XU Ke-xin
2007-01-01
A double beam near-infrared spectrometer is developed to compensate the water absorption and instrumental drift in intensity. The spectrometer maybe used for both single and double beam measurements, and the two operation modes are compared. The results show that the double beam technique eliminates instrumental drift in the single beam measurement and therefore the stability of the system increases by more than 20%. The compensation of the double beam system on water absorption is verified by the measurement of fat content in milk. The results show that the spectrum data based on double beam mode get better calibration model and lower prediction error than traditional single beam mode.
Mechatronic FEM model of an electromagnetic-force-compensated load cell
Weis, Hanna; Hilbrunner, Falko; Fröhlich, Thomas; Jäger, Gerd
2012-07-01
In this paper, a mechatronic model for an electromagnetic-force-compensated (EMC) load cell is presented. Designed in ANSYS Mechanical APDL®, the model consists of two modules: the mechanical behaviour of the load cell is represented by a FEM model. The electronic and the electromagnetic parts, consisting of a position indicator, controller and electromagnetic actuator, are implemented into the model as a set of differential equations via ANSYS Parametric Design Language (APDL). Optimization of the mechanical, electromagnetic and controller components can be performed using this model, as well as experiments to determine the sensitivity of the complete system to changes of environmental properties, e.g., the stiffness of the support.
Mechatronic FEM model of an electromagnetic-force-compensated load cell
In this paper, a mechatronic model for an electromagnetic-force-compensated (EMC) load cell is presented. Designed in ANSYS Mechanical APDL®, the model consists of two modules: the mechanical behaviour of the load cell is represented by a FEM model. The electronic and the electromagnetic parts, consisting of a position indicator, controller and electromagnetic actuator, are implemented into the model as a set of differential equations via ANSYS Parametric Design Language (APDL). Optimization of the mechanical, electromagnetic and controller components can be performed using this model, as well as experiments to determine the sensitivity of the complete system to changes of environmental properties, e.g., the stiffness of the support. (paper)
Roy, Surajit; Ladpli, Purim; Chang, Fu-Kuo
2015-09-01
Accurate interpretation of in-situ piezoelectric sensor signals is a challenging task. This paper presents the development of a numerical compensation model based on physical insight to address the influence of structural loads on piezo-sensor signals. The model requires knowledge of in-situ strain and temperature distribution in a structure while acquiring piezoelectric sensor signals. The parameters of the numerical model are obtained using experiments on flat aluminum plate under uniaxial tensile loading. It is shown that the model parameters obtained experimentally can be used for different structures, and sensor layout. Furthermore, the combined effects of load and temperature on the piezo-sensor response are also investigated and it is observed that both of these factors have a coupled effect on the sensor signals. It is proposed to obtain compensation model parameters under a range of operating temperatures to address this coupling effect. An important outcome of this study is a new load monitoring concept using in-situ piezoelectric sensor signals to track changes in the load paths in a structure.
Alekseev, G. A.; Apokin, V. D.; Buyanov, O. V.
The results on measuring the basic characteristics of a compensated lead calorimeter (NEPTUN experiment) in a hadron and electron beam are presented. A prototype consisting of 30 modulus was used in the measurements. The energy resolution follows the dependence approximately = 57%/sq. root of E, the detector uniformity is (+-)5%, the measured e/h ratio is close to unity.
Online compensation for target motion with scanned particle beams: simulation environment
Target motion is one of the major limitations of each high precision radiation therapy. Using advanced active beam delivery techniques, such as the magnetic raster scanning system for particle irradiation, the interplay between time-dependent beam and target position heavily distorts the applied dose distribution. This paper presents a simulation environment in which the time-dependent effect of target motion on heavy-ion irradiation can be calculated with dynamically scanned ion beams. In an extension of the existing treatment planning software for ion irradiation of static targets (TRiP) at GSI, the expected dose distribution is calculated as the sum of several sub-distributions for single target motion states. To investigate active compensation for target motion by adapting the position of the therapeutic beam during irradiation, the planned beam positions can be altered during the calculation. Applying realistic parameters to the planned motion-compensation methods at GSI, the effect of target motion on the expected dose uniformity can be simulated for different target configurations and motion conditions. For the dynamic dose calculation, experimentally measured profiles of the beam extraction in time were used. Initial simulations show the feasibility and consistency of an active motion compensation with the magnetic scanning system and reveal some strategies to improve the dose homogeneity inside the moving target. The simulation environment presented here provides an effective means for evaluating the dose distribution for a moving target volume with and without motion compensation. It contributes a substantial basis for the experimental research on the irradiation of moving target volumes with scanned ion beams at GSI which will be presented in upcoming papers
Beam loading effects in linacs with resonant loaded rf-power upgrade system
The RF power upgrade systems with microwave energy compression are using for accelerating wave power increase. The energy compression systems (ECS) with a resonant loading present the certain interest for practical use because of their specific properties. They are capable to increase an accelerating wave power up to 50... 100 times (up to 20 dB) and keeps this wave in accelerating structure for a longer time then conventional ECS. The resonant load is an essential part of the system and renders influence significantly on its parameters. The system consists of two connected resonators, one of which is using as a storing element and the second - as a load. Load may be a standing or a traveling wave resonator (TWR) formed by accelerating structure. Beam loading effects would change the properties of RF field in the load resonator. ECS characteristics and the accelerated beam parameters are discussed. (author)
Timber beams subjected to long - term loading
Sógel, K.
2010-09-01
Wood is a significant structural material, which is often used for timber bearing structures. Elements of timber structures must especially satisfy safety requirements, which are expressed by the ultimate limit states in the established standards. The structure must also satisfy the serviceability limit states. Local and global deformations make it impossible for the structure to serve the purpose it was designed for. It is important to take the deflections and their possible increase into account in the design to provide a structure which can be used during the whole period of service. Based on earlier examinations, it is known that a timber element over the course of long-term loading shows creep behavior. The structure of wood is able to adapt to the conditions of the surrounding environment. The properties of wood are especially affected by the relative humidity of the air and then by the type, intensity and duration of the loading. The most important factors affecting the serviceability of timber structures are volume changes caused by humidity and additional deflections caused by the effects of long-term loading. These phenomena emphasize the importance of serviceability limit states for timber structures. The paper deals with a long-term experimental investigation of timber girders that are currently often used. The aim was to obtain the deflection curves and mark the time dependence and the final deflections. The paper will also define the approximations for simulating the time-dependent deflections and obtain the creep coefficients for calculating the final deflections of the girders investigated.
AUTHOR|(SzGeCERN)390904; Papaphilippou, Yannis; Shatilov, Dmitry
2015-01-01
Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of β* and type of optics (flat or round), and possible compensation or additive effects between several low-β insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the longrange beam-beam effects, therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the fi...
RF broad-beam low-energy ion source with electron compensation
Zykov A. V.
2010-03-01
Full Text Available Characteristics of single-grid RF ion source with 250 mm beam diameter and 1A beam current have been studied. Energy distribution functions of electrons and ions emitted by the source have been measured. It is shown that the emitted electron current is sufficient for full ion beam current compensation. The technique of ion to electron current ratio control allowing to change this ratio in wide range is proposed. Using the ICP in the source allows to rich high current density in the low ion energy range with the possibility of independent control of ion energy and current density.
On the basis of the exact nonlinear theory relativistic TWT and BWO on irregular hollow waveguides with cathode filters-modulators with the account as propagating, and beyond cut-off waves, with the account of losses in walls of a waveguide and inhomogeneity directing an electronic beam magnetostatic fields finds out influence of dynamic stratification influence on efficiency of the generator. Possibility of almost fill compensation the electronic beam dynamic stratification influence on efficiency by optimization of an electronic beam arrangement in inhomogeneous high frequency and magnetic fields and characteristics of the irregular corrugated waveguide is shown. (author)
On Compensating Tune Spread Induced by Space Charge in Bunched Beams
Litvinenko, Vladimir N.; Wang, Gang
2014-01-01
Space charge effects play significant role in modern-day accelerators. These effects frequently constrain attainable beam parameters in an accelerator - or - in an accelerator chain. They also could limit the luminosity of hadron colliders operating either at low energies or with a sub-TeV high brightness hadron beams. A number of schemes for compensating space charge effects in a coasting (e.g. continuous) hadron beam were proposed and some of them had been tested. But all of these methods d...
Transient Beam Loading in the ALS Harmonic RF System
We report on the commissioning of a higher harmonic radiofrequency system at the Advanced Light Source, designed to improve the beam lifetime. We have achieved an increase above a factor of two in our best results up to now. Transient beam loading of the harmonic cavities, due to the unequal fill patterns, creates the greatest limitations on lifetime improvement. We also describe several interesting effects on the operation of the longitudinal and transverse multibunch feedback systems
Adaptive optical beam shaping for compensating projection-induced focus deformation
Pütsch, Oliver; Stollenwerk, Jochen; Loosen, Peter
2016-02-01
Scanner-based applications are already widely used for the processing of surfaces, as they allow for highly dynamic deflection of the laser beam. Particularly, the processing of three-dimensional surfaces with laser radiation initiates the development of highly innovative manufacturing techniques. Unfortunately, the focused laser beam suffers from deformation caused by the involved projection mechanisms. The degree of deformation is field variant and depends on both the surface geometry and the working position of the laser beam. Depending on the process sensitivity, the deformation affects the process quality, which motivates a method of compensation. Current approaches are based on a local adaption of the laser power to maintain constant intensity within the interaction zone. For advanced manufacturing, this approach is insufficient, as the residual deformation of the initial circular laser spot is not taken into account. In this paper, an alternative approach is discussed. Additional beam-shaping devices are integrated between the laser source and the scanner, and allow for an in situ compensation to ensure a field-invariant circular focus spot within the interaction zone. Beyond the optical design, the approach is challenging with respect to the control theory's point of view, as both the beam deflection and the compensation have to be synchronized.
Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Normand, Stéphane; Méchin, Laurence; Hamel, Matthieu
2016-05-01
Gadolinium-covered modified plastic scintillators show a high potential for the deployment of cost-effective neutron detectors. Taking advantage of the low-energy photon and electron signature of thermal neutron captures in gadolinium-155 and gadolinium-157 however requires a background correction. In order to display a trustable rate, dual compensation schemes appear as an alternative to Pulse Shape Discrimination. This paper presents the application of such a compensation scheme to a two-bismuth loaded plastic scintillator system. A detection scintillator interacts with incident photon and fast neutron radiations and is covered with a gadolinium converter to become thermal neutron-sensitive as well. In the meantime, an identical compensation scintillator, covered with terbium, solely interacts with the photon and fast neutron part of incident radiations. After the acquisition and the treatment of the counting signals from both sensors, a hypothesis test determines whether the resulting count rate after subtraction falls into statistical fluctuations or provides a robust image of neutron activity. A laboratory prototype is tested under both photon and neutron radiations, allowing us to investigate the performance of the overall compensation system. The study reveals satisfactory results in terms of robustness to a cesium-137 background and in terms of sensitivity in presence of a californium-252 source.
Loskutov А.B.; Altunin B.Iu.; Karnavsky I.А.
2011-01-01
This article presents trends of development and research in the region of increase of the electric energy quality and electromagnetic compatibility of middle big power load with rectifier type. It is developed the simulation model of compensator unit. There are presented results of simulation of the inactive power compensator which is based on the multimode cascade inverter.
Applications of heat pipes for high thermal load beam lines
The high flux beam produced by insertion devices often requires special heat removal techniques. For the optical elements used in such high thermal load beam lines the required precision demands a highly accurate design. Heat pipe cooling of critical elements of the x-1 beam line at the National Synchrotron Light Source is described. This method reduces vibrations caused by water cooling systems and simplifies the design. In some of these designs, deposited heat must be transferred through unbonded contact interfaces. A pinhole assembly and a beam position monitor designed for the x-1 beam line both transfer heat through such interfaces in an ultrahigh vacuum environment. The fundamental design objective is that of removing the heat with minimal interface thermal resistance. We present our test method and results for measuring the thermal resistance across metallic interfaces as a function of contact pressure. The design of some devices which utilize both heat pipes and thermal contact interfaces will also be described. (orig.)
Shiltsev, V.; Alexahin, Y.; Kamerdzhiev, V.; Kuznetsov, G.; Zhang, X.L.; /Fermilab; Bishofberger, K.; /Los Alamos
2007-06-01
Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams are significant sources of beam loss and lifetime limitations in the Tevatron Collider Run II (2001-present). We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in high energy physics (HEP) operation, predict the performance for planned luminosity upgrades and discuss ways to improve it.
A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz1/2, which was mainly dominated by the noise of the magnetic shield
Load beam unit replaceable inserts for dry coal extrusion pumps
Saunders, Timothy; Brady, John D.
2012-11-13
A track assembly for a particulate material extrusion pump according to an exemplary aspect of the present disclosure includes a link assembly with a roller bearing. An insert mounted to a load beam located such that the roller bearing contacts the insert.
Space charge compensation on the low energy beam transport of Linac4
AUTHOR|(SzGeCERN)733270; Scrivens, Richard; Jesus Castillo, Santos
Part of the upgrade program in the injector chains of the CERN accelerator complex is the replacement of the the proton accelerator Linac2 for the brand new Linac4 which will accelerate H$^-$ and its main goal is to increase the beam intensity in the next sections of the LHC accelerator chain. The Linac4 is now under commissioning and will use several ion sources to produce high intensity unbunched H$^-$ beams with different properties, and the low energy beam transport (LEBT) is the system in charge of match all these different beams to the Radio frequency quadrupole (RFQ). The space charge forces that spread the beam ions apart of each other and cause emittance growth limits the maximum intensity that can be transported in the LEBT, but the space charge of intense unbunched ion beams can be compensated by the generated ions by the impact ionization of the residual gas, which creates a source of secondary particles inside the beam pipe. For negative ion beams, the effect of the beam electric field is to ex...
Liu, Wei; Li, Chao; Sun, Zhao-Yang; Zhao, Yu; Wu, Shi-You; Fang, Guang-You
2016-08-01
In the terahertz (THz) band, the inherent shake of the human body may strongly impair the image quality of a beam scanning single frequency holography system for personnel screening. To realize accurate shake compensation in imaging processing, it is quite necessary to develop a high-precision measure system. However, in many cases, different parts of a human body may shake to different extents, resulting in greatly increasing the difficulty in conducting a reasonable measurement of body shake errors for image reconstruction. In this paper, a body shake error compensation algorithm based on the raw data is proposed. To analyze the effect of the body shake on the raw data, a model of echoed signal is rebuilt with considering both the beam scanning mode and the body shake. According to the rebuilt signal model, we derive the body shake error estimated method to compensate for the phase error. Simulation on the reconstruction of point targets with shake errors and proof-of-principle experiments on the human body in the 0.2-THz band are both performed to confirm the effectiveness of the body shake compensation algorithm proposed. Project supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. YYYJ-1123).
Prediction of Load Carrying Capacity of Corroded Reinforced Concrete Beam
范颖芳; 周晶; 冯新
2004-01-01
A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were conducted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic information of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory results are achieved.
Development of low energy ion beam system for space charge compensation experiments
A low energy ion beam system for space charge compensation (SCC) experiments was developed and evaluated. This system was designed for observation of SCC of a positive ion beam with an electron beam. The system consisted of the ion source chamber and the SCC experiment chamber. The ion source chamber was equipped with the compact microwave ion source for low voltage extraction. Ion current at initial position of the analysis chamber was 84 μA at extraction voltage of 500 V, and satisfied a condition to observe the SCC effect clearly. In order to evaluate the SCC, we measured the arrival ion current by supplying thermionic electrons, which were extracted from a tungsten filament driven by ac voltage. As the electron supply, the arrival ion current increased from 40 to 68 μA at the potential of filament of +3 eV which produced the thermionic electron with extremely low energy extracted by space charge of the ion beam
A method to compensate the energy loss of a continuous stacked beam with a large momentum spread
A system of rectangular drift tube loaded cavities resonating in the TE 101 mode combined with a cyclic scaling guide field can be used to accelerate an unbunched beam of charged particles. The system is superior to phase displacement because the cavities are driven at a fixed frequency with certain phase differences between each other. The range of particle momenta is limited by rf-knock out. Rf-induced betatron oscillations and phase dependent momentum changes can be compensated by means of sixteen cavities on the circumference of the accelerator. The amplitude of the betatron oscillations and the energy gain were calculated numerically for storage devices consisting of a spiral-sector FFAG guide field and one or sixteen cavities, respectively, using measured rf-feld data. The systems seem to be practical only for electrons with an energy up to 100 MeV. The rf-system works within an energy width of several MeV. (Auth.)
Stud Reinforcement in Beam-Column Joints under Seismic Loads
Ibrahim, Hatem Hassan Ali
Current codes recommend large amounts of shear reinforcement for reinforced concrete beam-column joints causing significant congestion. This research aims at investigating experimentally and numerically the efficiency of using studs with a head at each end in lieu of conventional closed hoops in reinforced concrete beam-column joints. The proposed reinforcement reduces congestion and ensures easier assembly of the reinforcing cage, saving labour cost and enhancing performance of the joint. Based on this research, a recommended arrangement and detailing of headed studs and their design for exterior beam-column joint are presented. The experimental investigation consisted of testing ten full-scale beam-column joint specimens under quasi-static cyclic loading. The specimens represented an exterior beam-column joint subassembly isolated at the points of contra-flexure from a typical multi-storey, multi-bay reinforced concrete frame. A test setup was developed to simulate the lateral inter-storey drift. The test parameters included: the type, arrangement and amount of shear reinforcement, the load history and rate of loading, and the amount of reinforcement for out-of-plane confinement of the joint. Envelopes of the hysteretic behaviour of the specimens and the joint deformation under shear stress are presented. The stiffness degradation, the strain levels in the joint reinforcement, the contribution of joint, beam, and column to the inter-storey drift, and the energy dissipation were compared. All the test specimens reinforced with headed studs in the joint achieved considerable enhancement in their behaviour under cyclic loads and exhibited a performance close to that of a joint reinforced with closed hoops and cross ties according to the code. All the specimens with adequate out-of-plane confinement had an equivalent behaviour compared with the code-based specimen and achieved a desirable mode of failure. Use of double-headed studs proved to be a viable option for
Frequency-temperature compensated sapphire loaded cavity for compact hydrogen masers
We report some theoretical and experimental results about a frequency-temperature compensated sapphire loaded cavity for compact hydrogen maser atomic clocks. Based on theoretical calculations, the frequency-temperature coefficients in the TE011 mode of a sapphire cavity associated with two small rings of SrTiO3 can be reduced. For instance, at 50 C, when the thickness of the SrTiO3 ring is 5 mm, the frequency-temperature coefficient can be reduced by about five times, and in the meantime, the quality factor can be kept at above 40 000 synchronously. A sapphire loaded cavity and eight small compensated chips of SrTiO3 were prepared and a combined cavity of sapphire with SrTiO3 chips was simulated by the finite element method and measured by experiments. The simulation and the related experimental results agree well. In addition, the frequency-temperature coefficients in two different configurations of eight SrTiO3 chips were also measured and compared. (authors)
Compensations of beam-beam resonances using crabbing schemes at large Piwinski crossing angles
We study combined effects of the crab crossing and of the crab waist lattice options on the luminosity performance of a collider where the crossing angle collisions are used. We have found that for collisions at large Piwinski angle a proper combination of the crab crossing and of the crab waist lattice insertions results in exact cancellation of all synchro-betatron as well as of all betatron coupling beam-beam resonances of odd orders. The beam-beam limitations on the luminosity for such a collider with the crossing angle collisions will be the same like that for a collider with head-on collisions of short bunches.
Chen, Junchi; Peng, Yujie; Su, Hongpeng; Leng, Yuxin
2016-06-01
To compensate for the gain saturation effect in the high-energy laser amplifier, a modified polarization beam combination (PBC) method is introduced to reshape temporal waveform of the injected laser pulse to obtain a controlled high-energy laser pulse shape after amplification. One linearly polarized beam is divided into two orthogonal polarized beams, which spatially recombine together collinearly after propagating different optical paths with relative time delay in PBC structure. The obtained beam with polarization direction being rotated by the following half wave plate is divided and combined again to reform a new beam in another modified polarization beam structure. The reformed beam is injected into three cascaded laser amplifiers. The amplified pulse shape can be controlled by the incident pulse shape and amplifier gain, which is agreeable to the simulation by the Frank-Nodvik equations. Based on the simple method, the various temporal waveform of output pulse with tunable 7 to 20 ns pulse duration can be obtained without interferometric fringes.
Elasticity solution of laminated beams subjected to thermo-loads
钱海; 周叮; 刘伟庆; 方海
2015-01-01
According to the two-dimensional (2-D) thermo-elasticity theory, the exact elasticity solution of the simply supported laminated beams subjected to thermo-loads was studied. An analytical method was presented to obtain the temperature, displacement and stress fields in the beam. Firstly, the general solutions of temperature, displacements and stresses for a single-layered simply supported beam were obtained by solving the 2-D heat conduction equation and the 2-D elasticity equations, respectively. Then, based on the continuity of temperature, heat flux, displacements and stresses on the interface of two adjacent layers, the formulae of temperature, displacements and stresses between the lowest layer and the top layer of the beam were derived out in a recurrent manner. Finally, the unknown coefficients in the solutions were determined by the use of the upper surface and lower surface conditions of the beam. The distributions of temperature, displacement and stress in the beam were obtained by substituting these coefficients back to the recurrence formulae and the solutions. The excellent convergence of the present method has been demonstrated and the results obtained by the present method agree well with those from the finite element method. The effects of surface temperatures, thickness, layer number and material properties of the plate on the temperature distribution were discussed in detail. Numerical results reveal that the displacements and stresses monotonically increase with the increase of surface temperatures. In particular, the horizontal stresses are discontinuous at the interface.
Barrier Buckets and Transient Beam Loading in the SPS
Bohl, T; Garoby, R; Linnecar, Trevor Paul R; Shaposhnikova, Elena; Tückmantel, Joachim
2003-01-01
Using long bunches held in place by barrier buckets to overcome the limitations associated with peak density in high intensity bunched beams could be a promising scheme for increasing the luminosity of LHC. In the SPS at CERN an initial barrier bucket machine development(MD) study was done in 1999 to check the capabilities of 200 MHz thick barriers generated by the travelling wave system. A second experiment took place on 5th of August 2003 to examine high intensity effects. In this experiment a flat and stable long bunch of @ 3 µs bunch length was obtained and kept for more than 80 minutes without developing a significant line density modulation. However, strong beam loading effects were observed during the injection process, causing a coherent, non-negligible energy transfer from the beam to the RF cavities, and significant fraction of the injected beam was lost to a coasting beam background. The beam intensity that could be confined in between the barriers suffered emittance increase and was not high enou...
Fuse, H., E-mail: fuseh@ipu.ac.jp [Department of Radiological Sciences, Ibaraki Prefectural University of Health Science, Amimachi, Inashiki-gun, Ibaraki (Japan); Suzuki, K.; Shida, K.; Takahashi, H.; Kobayashi, D.; Seki, M. [Department of Radiology, University of Tsukuba Hospital, Tsukuba city, Ibaraki (Japan); Mori, Y.; Sakae, T. [Proton Medical Research Center, University of Tsukuba, Tsukuba city, Ibaraki (Japan); Isobe, T. [Department of Radiation Oncology, University of Tsukuba, Tsukuba city, Ibaraki (Japan); Okumura, T.; Sakurai, H. [Proton Medical Research Center, University of Tsukuba, Tsukuba city, Ibaraki (Japan); Department of Radiation Oncology, University of Tsukuba, Tsukuba city, Ibaraki (Japan)
2014-06-15
Total skin electron beam is a specialized technique that involves irradiating the entire skin from the skin surface to only a few millimetres in depth. In the Stanford technique, the patient is in a standing position and six different directional positions are used during treatment. Our technique uses large electron beams in six directions with an inclinable couch on motorized table and a compensating filter was also used to spread the electron beam and move its intensity peak. Dose uniformity measurements were performed using Gafchromic films which indicated that the surface dose was 2.04 ± 0.05 Gy. This technique can ensure the dose reproducibility because the patient is fixed in place using an inclinable couch on a motorized table.
High Resolution Beam Orbit Measurement Electronics based on Compensated Diode Detectors
Gasior, M
2010-01-01
A high resolution beam position monitor (BPM) electronics based on diode peak detectors has been developed at CERN. The circuit processes the BPM electrode signals independently, converting the short beam pulses into slowly varying signals which can be digitized with high resolution ADCs operating in the kHz range or even measured with a DC voltmeter. For signals with peak amplitudes larger than some hundred mV the non-linear forward voltage of the diodes is compensated by a simple network using signals from two peak detectors, one with a single and the second with two diodes in series. This contribution presents results obtained with the first prototype in the laboratory and with the CERN-SPS beam. Ongoing development and possible future applications of the technique are also discussed.
Study of the transient effects of the space charge compensation on the dynamics of an intense beam
A main interest in the design of ion accelerators is the control of the dynamics of intense beams at low energy. This dynamics is dominated by nonlinear effects of the Space Charge (SC) field. This SC field induces a halo formation which can induce losses along the transport. Once ionized by the beam, the residual gas, diffused by the source and produced by the desorption of the vacuum chamber of the accelerator, contributes to the production of electrons and ions. According to their sign of charge compared to the beam, these particles will be repelled or confined. The accumulation of particles in the beam contributes to the compensation of the SC field. However, this neutralization induces other non linearity which are dependent on time. This thesis presents an experimental and theoretical work of the SC compensation for ion beams (H+ and H-). The dynamics of these beams is modelled by a new PIC code, CARTAGO, ensuring the coupling between the created plasma and the studied beams. A single-particle study introduces the dynamics of the plasma in presence of the SC field and of an external magnetic field. The modeling of the compensation with the 1D version of CARTAGO code gave the establishment times and the compensation degrees for several cases of beams and various gas pressures. The compensation of a protons beam was studied more particularly in the low-energy line of the Injector of Protons of High Intensity (IPHI) at Saclay. Simulations show an over-compensation of the space charge inside the focusing solenoid and outside the compensation is only partial. Experimental confrontations of the 2D(r,z) modeling results in a part of this line are also detailed. (author)
Improvements of the undulator spectral performance by compensating the backing beam deflection
Wang, C; Chang, L H; Chang, C H; Fan, T C; Bach, H; Blomqvist, I
2002-01-01
This study thoroughly examines how the backing beam deflection affects the undulator spectral performance. Reduction of the undulator spectral intensity owing to backing beam deflection is analytically evaluated based on plane-wave approximation. The results reveal that the amplitude and the slope of the backing beam deflection affect the undulator spectral performance. Provided is a novel figure-of-merit, rms of the regressed accumulated gap deviation, to determine the backing beam deflection budget. An example of a 3.9 m undulator supporting carriage mounted with 50-mm period length undulator magnet (U5) under a maximum magnetic loading of 5 metric tons at a minimum operating gap of 14 mm, is provided. Its mechanical features are first examined via 3D commercial finite element code ANSYS that concludes the backing beam deflection is influenced heavily by the rigidity of the undulator support frames. Examining the corresponding spectral performance shows that significantly diminishing the undulator spectral ...
Simulation of space charge compensation in a multibeamlet negative ion beam
Sartori, E.; Maceina, T. J.; Veltri, P.; Cavenago, M.; Serianni, G.
2016-02-01
Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H- ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H- beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H2+ ions) or by stripping of the beam ions (electrons, H, and H+). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions.
Simulation of space charge compensation in a multibeamlet negative ion beam
Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H− ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H− beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H2+ ions) or by stripping of the beam ions (electrons, H, and H+). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions
Simulation of space charge compensation in a multibeamlet negative ion beam.
Sartori, E; Maceina, T J; Veltri, P; Cavenago, M; Serianni, G
2016-02-01
Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H(-) ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H(-) beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H2 (+) ions) or by stripping of the beam ions (electrons, H, and H(+)). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions. PMID:26932089
Simulation of space charge compensation in a multibeamlet negative ion beam
Sartori, E., E-mail: emanuele.sartori@igi.cnr.it; Veltri, P.; Serianni, G. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); Maceina, T. J. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); Università degli Studi di Padova, Padova (Italy); Cavenago, M. [INFN-LNL, Viale dell’Università n. 2, 35020 Legnaro (Italy)
2016-02-15
Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H{sup −} ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H{sup −} beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H{sub 2}{sup +} ions) or by stripping of the beam ions (electrons, H, and H{sup +}). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 μs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions.
Ultimate Experiment of Ruptured Concrete Beams Strengthened Using GFRP-Sheet After Fatigue Loads
Tata, Arbain; Parung, Herman; Tjaronge, Wihardi; Djamaluddin, Rudy
2014-01-01
An experimental study has been carried out to investigate the structural behavior of beam which was strengthened by glass fiber reinforced polymer (GFRP-S). The Experimental was carried out to determine the effect of fatigue loads on flexural capacity of reinforced concrete beams. Each specimen was 6 m long with 300x500 mm rectangular cross section. Each specimen was treated with different loads. In this study using two different loads applied to the beam was static loads and fatigue loads. S...
Applications of heat pipes for high thermal load beam lines
The high flux beam produced by insertion devices often requires special heat removal techniques. For the optical elements used in such high thermal load beam lines, the required precision demands a highly accurate design. Heat pipe cooling of critical elements of the X-1 beam line at the National Synchrotron Light Source is described. This method reduces vibrations caused by water cooling systems and simplifies the design. In some of these designs, deposited heat must be transferred through unbonded contact interfaces. A pinhole assembly and a beam position monitor designed for the X-1 beam line both transfer heat through such interfaces in an ultrahigh vacuum environment. The fundamental design objective is that of removing the heat with minimal interface thermal resistance. We present our test method and results for measuring the thermal resistance across metallic interfaces as a function of contact pressure. The design of some devices which utilize both heat pipes and thermal contact interfaces will also be described. 12 refs., 8 figs
An alternative approach to compensators design for photon beams used in radiotherapy
Jurkovic, S. [University Hospital, Department of Radiotherapy, Physics Division, Kresimirova 42, 51000 Rijeka (Croatia); Zauhar, G. [School of Medicine, Department of Physics, Brace Branchetta 20, 51000 Rijeka (Croatia)], E-mail: gordz@medri.hr; Bistrovic, M. [Hospital for Tumors, Radiotherapy Department, Ilica 272, 10000 Zagreb (Croatia); Faj, D. [University Hospital, Department of Radiotherapy and Oncology, J. Huttlera 4, 31000 Osijek (Croatia); Kaliman, Z. [Faculty of Sciences and Arts, Department of Physics, Omladinska 14, 51000 Rijeka (Croatia); Smilovic Radojcic, D. [University Hospital, Department of Radiotherapy, Physics Division, Kresimirova 42, 51000 Rijeka (Croatia)
2007-09-21
The use of compensators in order to achieve desired dose distribution has a long history and is a well-established technique in radiation therapy planning. There are several different calculation methods for determining a compensator's thickness. An alternative method that is based on the Cunningham's modification of Clarkson's method to calculate scattered radiation in beams with an inhomogeneous cross-section is proposed. It is well known that the total dose distribution of radiotherapy photon beam consists of the contributions of the primary beam, attenuated by the tissue layer, and the scattered radiation generated by the primary radiation in single and multiple photon scatter events. The scattered component can be represented as a function of the primary radiation. The central point of our method is the numerical estimation of the primary distribution required to achieve the desired total distribution. Now using the calculated primary distribution, the shape of the modulator could be determined. In this way the contribution of the scattered component is validated in a more accurate way than using effective attenuation coefficients, which is a common practice. The method is verified in various clinical situations and compared with the standard method. The accuracy, although dependent on geometry, was improved by at least 2%. With more complex geometries there is an even higher gain in accuracy with our method when compared to the standard method.
Kong, Xiangdong; Ba, Kaixian; Yu, Bin; Cao, Yuan; Zhu, Qixin; Zhao, Hualong
2016-05-01
Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit (HDU), and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this
Image-Based Motion Compensation for High-Resolution Extremities Cone-Beam CT
Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.
2016-01-01
Purpose Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1–4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10–15% improvement in SSIM was attained for 2–4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials.
Image-based motion compensation for high-resolution extremities cone-beam CT
Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.
2016-03-01
Purpose: Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods: Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1-4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results: Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10-15% improvement in SSIM was attained for 2-4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion: The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials.
New diagnostic technique for Zeeman-compensated atomic beam slowing: technique and results
Molenaar, P.A.; Van Der Straten, P.; Heideman, H.G.M.; Metcalf, H.
2001-01-01
We have developed a new diagnostic tool for the study of Zeeman-compensated slowing of an alkali atomic beam. Our time-of-flight technique measures the longitudinal veloc- ity distribution of the slowed atoms with a resolution below the Doppler limit of 30 cm/s. Furthermore, it can map the position and velocity distribution of atoms in either ground hyperfine level inside the solenoid without any devices inside the solenoid. The technique reveals the optical pumping ef- fects, and shows in de...
Exact fan-beam compensated reconstruction formula for time-dependent affine deformations
This work is dedicated to the reduction of reconstruction artefacts due to motions occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensated algorithms, where the model of motion is included in the reconstruction formula. The questions that have to be answered in this approach are: first what conditions the deformation has to verify to allow the reconstruction of the object from the projections acquired sequentially during the deformation? and second how can we reconstruct the object in that case? Here we solve these questions in the particular case of general time-dependent affine deformations. We treat the problem of admissibility conditions on the deformation in the parallel-beam and in the fan-beam cases. Then we propose for both geometries exact reconstruction methods based on re-binning or sequential FBP formulae. (author)
On the beam loading of induction voltage modulator
Effects of beam loading on the induction voltage modulator have been experimentally evaluated using a FET (field effect transistor) based driving pulser and a resistive secondary circuit. The core materials used in this study, are made of a nano-crystalline alloy (Finemet) and a Co-amorphous alloy. The voltage modulation is evaluated as a function of magnetization rate dB/dt, magnetization level of the magnetic material and the current rise-rate of the secondary loop (dI/dt). Experimental results indicate that the voltage modification depend not only on the magnetization rate but also on the initial state of the magnetic materials and also flux swing B from it. These results indicate that the response of the modulator against the loading depends on the transient magnetic-domain motion in the core materials
Diethold, Christian; Hilbrunner, Falko
2012-07-01
This paper discusses the force measurement of small forces in combination with high dead loads. The measurement force acts perpendicular to gravity, while the dead load is orientated in the direction of gravity. Furthermore, the influence of the dead load on the metrological properties is described. The application is the flow rate measurement of conducting fluids by Lorentz force (Thess et al 2006 Phys. Rev. Lett. 96 164501). The aim is to measure forces with a resolution of FM = 10-6 N. The dead load is mainly due to the mass of the magnet system. It is of the order of magnitude of FG = 10 N. The force measurement system works with the principle of electromagnetic force compensation. The applied force is compensated by a Lorentz force induced by a current in a voice coil and a magnetic field of a permanent magnet. The current is proportional to the applied force.
This paper discusses the force measurement of small forces in combination with high dead loads. The measurement force acts perpendicular to gravity, while the dead load is orientated in the direction of gravity. Furthermore, the influence of the dead load on the metrological properties is described. The application is the flow rate measurement of conducting fluids by Lorentz force (Thess et al 2006 Phys. Rev. Lett. 96 164501). The aim is to measure forces with a resolution of FM = 10−6 N. The dead load is mainly due to the mass of the magnet system. It is of the order of magnitude of FG = 10 N. The force measurement system works with the principle of electromagnetic force compensation. The applied force is compensated by a Lorentz force induced by a current in a voice coil and a magnetic field of a permanent magnet. The current is proportional to the applied force. (paper)
Springback Prediction and Compensation for a High Strength Steel Side Impact Beam
Prediction of formability for sheet metal pressings has advanced to a high state of confidence in recent years. The major challenge is now to predict springback and, moreover, to assist in the design of tooling to correctly compensate for springback. This is particularly the case for materials now being routinely considered for automotive production, such as aluminium and ultra high strength steels, which are prone to greater degrees of springback than traditional mild steels. This paper presents a case study based on the tool design for an ultra high strength steel side impact beam. The forming and springback simulations, carried out using eta/DYNAFORM (based on the LS-DYNA solver), are reported and compared to measurements from the prototype panels. The analysis parameters used in the simulation are presented, and the sensitivity of the results to variation in physical properties is also reviewed. The process of compensating the tools based on the analysis prediction is described; finally, an automated springback compensation method is also applied and the results compared with the final tool design
A motion-compensated cone-beam CT using electrical impedance tomography imaging
Cone-beam CT (CBCT) is an imaging technique used in conjunction with radiation therapy. For example CBCT is used to verify the position of lung cancer tumours just prior to radiation treatment. The accuracy of the radiation treatment of thoracic and upper abdominal structures is heavily affected by respiratory movement. Such movement typically blurs the CBCT reconstruction and ideally should be removed. Hence motion-compensated CBCT has recently been researched for correcting image artefacts due to breathing motion. This paper presents a new dual-modality approach where CBCT is aided by using electrical impedance tomography (EIT) for motion compensation. EIT can generate images of contrasts in electrical properties. The main advantage of using EIT is its high temporal resolution. In this paper motion information is extracted from EIT images and incorporated directly in the CBCT reconstruction. In this study synthetic moving data are generated using simulated and experimental phantoms. The paper demonstrates that image blur, created as a result of motion, can be reduced through motion compensation with EIT
Власенко, Руслан Володимирович; Бялобржеський, Олексій Володимирович
2016-01-01
Electricity quality improving is extremely relevant nowadays. With such industrial loads as induction motors, induction furnaces, welding machines, controlled or uncontrolled rectifiers, frequency converters and others reactive power, harmonics and unbalance are generated in power grid. Reactive power, higher harmonic currents and asymmetry loads influence the functioning of electric devices and electrical mains. An effective technical solution is the use of new compensating devices, that is ...
Investigation of ion beam space charge compensation with a 4-grid analyzer
Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system of the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown
Investigation of ion beam space charge compensation with a 4-grid analyzer
Ullmann, C.; Adonin, A.; Berezov, R.; Chauvin, N.; Delferrière, O.; Fils, J.; Hollinger, R.; Kester, O.; Senée, F.; Tuske, O.
2016-02-01
Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system of the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.
Investigation of ion beam space charge compensation with a 4-grid analyzer
Ullmann, C., E-mail: c.ullmann@gsi.de; Adonin, A.; Berezov, R.; Fils, J.; Hollinger, R.; Kester, O. [GSI, Darmstadt (Germany); Chauvin, N.; Delferrière, O.; Senée, F.; Tuske, O. [CEA, Saclay (France)
2016-02-15
Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system of the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.
Beam pattern improvement by compensating array nonuniformities in a guided wave phased array
This paper presents a simple data processing algorithm which can improve the performance of a uniform circular array based on guided wave transducers. The algorithm, being intended to be used with the delay-and-sum beamformer, effectively eliminates the effects of nonuniformities that can significantly degrade the beam pattern. Nonuniformities can arise intrinsically from the array geometry when the circular array is transformed to a linear array for beam steering and extrinsically from unequal conditions of transducers such as element-to-element variations of sensitivity and directivity. The effects of nonuniformities are compensated by appropriately imposing weight factors on the elements in the projected linear array. Different cases are simulated, where the improvements of the beam pattern, especially the level of the highest sidelobe, are clearly seen, and related issues are discussed. An experiment is performed which uses A0 mode Lamb waves in a steel plate, to demonstrate the usefulness of the proposed method. The discrepancy between theoretical and experimental beam patterns is explained by accounting for near-field effects. (paper)
Simulation Study on the Emittance Compensation of Off-axis Emitted Beam in RF Photoinjector
Huang, Rui-Xuan; Jia, Qi-Ka; Papadopoulos, Christos; Sannibale, Fernando
2016-01-01
To make full use of photocathode material and improve its quantum efficiency lifetime, it can be necessary to operate laser away from the cathode center in photoinjectors. In RF guns, the off-axis emitted beam will see a time-dependent RF effect, which would generate a significant growth in transverse emittance. It has been demonstrated that such an emittance growth can be almost completely compensated by orienting the beam on a proper orbit in the downstream RF cavities along the injector. In this paper we analyze in detail the simulation techniques used in reference[1] and the issues associated with them. The optimization of photoinjector systems involving off-axis beams is a challenging problem. To solve this problem, one needs advanced simulation tools including both genetic algorithms and an efficient algorithm for 3D space charge. In this paper, we report on simulation studies where the two codes ASTRA and IMPACT-T are used jointly to overcome these challenges, in order to optimize a system designed to ...
Vibration Analysis of a Simply Supported Beam Traversed by Uniform Distributed Moving Load
Yu YANG; Nian-guan TENG; Yian-feng TENG
2004-01-01
Considering the engineering background of some transportation system like maglev, vertical vibration of the simply supported beam is investigated. The length of the vehicle is assumed to be longer than the beam span. The model of moving distributed load with constant speed is established .The beam can be taken as Euler-Bernoulli beam model and the right side of the control equation is simplified by using a moving status function. Duhamel integral and mode superposition method is used to solve the dynamic behavior of the beam. In this aspect deflection and acceleration are included. The results of different parameters such as the span of beam, velocity of load and ratio vehicle-Beam masses are compared. All results show that the dynamic response of the beam is tied up with these factors: the frequency of the beam, the moving frequency of the load and the ratio of vehicle-beam mass.
Markou, Helen; Andersen, Peter Bjørn; Larsen, Gunner Chr.
2011-01-01
methods that typically focus on either load or power prediction. As a consequence, the wake affected inflow field generated by the DWM formulation opens for control strategies for the individual turbine. Two different control approaches for load reduction on the individual turbines are implemented in the...... multi-body aero-servo-elastic tool HAWC2, developed at Risø-DTU in Denmark, and their potential load reduction capabilities compared: (1) full-blade ‘individual-pitch controllers’ acting as wake compensators and (2) controllers using trailing-edge flaps. Information on the wake inflow conditions...... for the loading conditions of the individual turbines in the farm. The dynamic wake meandering model (DWM) is believed to capture the essential physics of the wake problem, and thus, both load and production aspects can be predicted, which is contrary to the traditional engineering wake prediction...
Experimental Study of RC Beams Strengthened with CFRP Sheets Under Sustaining Loads
WANG Wenwei; LI Guo
2006-01-01
Seven reinforced concrete (RC) beams strengthened in flexure using carbon fiber reinforced polymer (CFRP) sheets subjected to different sustaining loads were tested. The effects of initial load and load history on the ultimate strength of strengthened RC beams were examined by externally bonded CFRP sheets. The main experimental parameters included different levels of sustaining load at the time of strengthening, and load history. Experimental results show that sustaining load levels at the time of strengthening have important influences on the ultimate strength of strengthened RC beams. If the initial load is the same, the ultimate strength of RC beams strengthened with CFRP sheets is almost the same regardless of load history at the time of strengthening.
Harpreet Singh; Durga Sharma
2015-01-01
Abstract Reactive power compensation capability of a fixed capacitor thyristor controlled reactor type static VAr compensator is being investigated in this paper. The TCR has the power transfer controlling capability only in the lagging power factor range. The range of TCR can be extended by connecting a fixed capacitor in shunt with the TCR. The compensated reactive power can be selectively controlled by appropriately changing the firing angle of the TCR circuit in lagging as well as the lea...
Ding, Lan; Zhu, Hong-Ping; Wu, Li
2016-07-01
The propagation and attenuation properties of waves in ordered and disordered periodic composite Timoshenko beams, which consider the effects of axial static load and structural damping, resting on elastic foundations are studied when the system is subjected to moving loads of constant amplitude with a constant velocity. The transfer matrix methodology is adopted to formulate the model in a reference coordinate system moving with the load. The localization factor is calculated to determine the wave velocity pass bands and stop bands. The interactions between the static axial load and moving load, structural damping and disorder on the bands are analyzed.
A large negative ion source for JT-60U produces high current ion beam from a wide extraction area of 45 cm x 110 cm. On the other hand, a cross-sectional area of the negative ion based neutral beam (NNB) injection port on JT-60U is narrow, about 50 cm x 60 cm. In order to inject the neutral beam at a high geometric efficiency, i.e. to suppress beam loss in the beamline, it is necessary to steer the beam for both compensation of undesirable beam deflection in extractor and focusing of the beam. For the JT-60U, two methods are provided for the required beam steering. Among them the results of beam steering experiment by aperture displacement and the design study are summarized in the present report. The experiment was carried out with 400 keV negative ion source, which has the three stage accelerator of similar structure as the JT-60U ion source, at Negative Ion Acceleration Test Stand (NIAS). High energy negative ion beams of the same perveance as that of 500 keV full power operation of the JT-60U ion source were steered with displacement of electron suppression grid and grounded grid for the beam deflection compensation and the focusing. The experimental results of the high energy beam steering are discussed based on the thin lens theory. Then the aperture arrangement of electron suppression grid and grounded grid are designed for the large negative ion source of JT-60U NNB injector. (author)
Inoue, Takashi [Department of ITER Project, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka, Ibaraki (Japan); Miyamoto, Kenji; Okumura, Yoshikazu; Watanabe, Kazuhiro [Department of Nuclear Fusion Engineering, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka, Ibaraki (Japan); Nagase, Akihito [Hitachi Ltd., Tokyo (Japan)
2000-03-01
A large negative ion source for JT-60U produces high current ion beam from a wide extraction area of 45 cm x 110 cm. On the other hand, a cross-sectional area of the negative ion based neutral beam (NNB) injection port on JT-60U is narrow, about 50 cm x 60 cm. In order to inject the neutral beam at a high geometric efficiency, i.e. to suppress beam loss in the beamline, it is necessary to steer the beam for both compensation of undesirable beam deflection in extractor and focusing of the beam. For the JT-60U, two methods are provided for the required beam steering. Among them the results of beam steering experiment by aperture displacement and the design study are summarized in the present report. The experiment was carried out with 400 keV negative ion source, which has the three stage accelerator of similar structure as the JT-60U ion source, at Negative Ion Acceleration Test Stand (NIAS). High energy negative ion beams of the same perveance as that of 500 keV full power operation of the JT-60U ion source were steered with displacement of electron suppression grid and grounded grid for the beam deflection compensation and the focusing. The experimental results of the high energy beam steering are discussed based on the thin lens theory. Then the aperture arrangement of electron suppression grid and grounded grid are designed for the large negative ion source of JT-60U NNB injector. (author)
Fatigue strength in polymer-reinforced concrete beams under cyclic loading
Kwak, K.H. [Won Kwang University, City of Iri (Korea, Republic of); Kim, J.J. [Iri Regional Construction M.O.C, Cholla-Buk-Do 570-102, City of Iri (Korea, Republic of)
1995-06-01
This research focuses on producing an inexpensive polymer, and also on experiments for producing various colors of the high strength polymer concrete in concrete structures. At present, only a few tests on the shear behavior of polymer-reinforced concrete (PRC) beams have been reported. Even fewer experiments on fatigue loading have been carried out to date. In the current experiments, reinforced concrete beams with a polymer fraction are investigated. The beams in this study are reinforced with conventional stirrups at appropriate intervals, and are designed to take static and fatigue loads. The strength of the beams is measured and the behavior of the beams under each loading are observed to determine the advantages of adding a polymer to reinforced concrete beams. Since the shear-fatigue behavior of PRC beams is not well understood, the appropriate limit state model of PRC beams subjected to shear-fatigue loading is developed in this research by incorporating the uncertainties which are assessed based on fatigue test results. Using specimens of reinforced concrete or PRC beams with and without stirrups, compression and split cylinder tests, as well as fatigue tests, were performed. The static test data consist of load, displacement and strain measurements at specified reinforcement locations. In this study, mean regression S-N curves are obtained to investigate the shear-fatigue characteristics that the test results are distributed over a wide fatigue life range at the same fatigue load level but, in general, the mean shear-fatigue strength of PRC beams with stirrups is higher than for PRC beams without stirrups. In the static tests, it has been observed that the beams have the same fracture modes as those of reinforced concrete. In the fatigue tests, the PRC beams were observed to perform rather poorly with regard to impact load, but it can be said that the increase in strength and excellent repair performance of the beams were verified. (orig.).
Fatigue strength in polymer-reinforced concrete beams under cyclic loading
This research focuses on producing an inexpensive polymer, and also on experiments for producing various colors of the high strength polymer concrete in concrete structures. At present, only a few tests on the shear behavior of polymer-reinforced concrete (PRC) beams have been reported. Even fewer experiments on fatigue loading have been carried out to date. In the current experiments, reinforced concrete beams with a polymer fraction are investigated. The beams in this study are reinforced with conventional stirrups at appropriate intervals, and are designed to take static and fatigue loads. The strength of the beams is measured and the behavior of the beams under each loading are observed to determine the advantages of adding a polymer to reinforced concrete beams. Since the shear-fatigue behavior of PRC beams is not well understood, the appropriate limit state model of PRC beams subjected to shear-fatigue loading is developed in this research by incorporating the uncertainties which are assessed based on fatigue test results. Using specimens of reinforced concrete or PRC beams with and without stirrups, compression and split cylinder tests, as well as fatigue tests, were performed. The static test data consist of load, displacement and strain measurements at specified reinforcement locations. In this study, mean regression S-N curves are obtained to investigate the shear-fatigue characteristics that the test results are distributed over a wide fatigue life range at the same fatigue load level but, in general, the mean shear-fatigue strength of PRC beams with stirrups is higher than for PRC beams without stirrups. In the static tests, it has been observed that the beams have the same fracture modes as those of reinforced concrete. In the fatigue tests, the PRC beams were observed to perform rather poorly with regard to impact load, but it can be said that the increase in strength and excellent repair performance of the beams were verified. (orig.)
Reza Sedaghati
2013-09-01
Full Text Available In this paper, the structure of Hybrid Power Flow Controller (HPFC is proposed in order to improve static voltage stability characteristics. HPFC forms a hybrid controller using IPFC series converters as a hybrid with existing parallel and passive compensator (SVC in power system. Utilization of hybrid structures makes it possible to use converters for improving performance of both old and existing compensators in power networks. In this study, the power injection model (PIM is used to model the hybrid power flow controller in Newton load flow. The aforementioned model is simulated in MATLAB software. The P-V curves of PQ buses of a typical system are evaluated by a continuous power flow (CPF method to analyses the effect of this controller on static voltage stability characteristics. Meanwhile, SVC as existing devices in the system and UPFC and IPFC as state-of-the-art compensator devices are compared with the proposed hybrid structure. The amount of active and reactive power loss and improvement of loading limit of the system are used as main parameters in our comparison.
Design of the overhead bridge crane beam and strenght analysis for given loads
Armán Morales, Sergio
2012-01-01
The main aim of the project is: for given loads, analyse and design (analytically and with Catia software) different beams for an overhead crane. For this purpose, it will be study the theory of cranes and structures calculation and from this theory I will design an algorithm that allows finding the necessary beam from de European standard metallic beam list. After obtaining the analytical and the software (Catia) results for each beam, it will be compare the results between them and presente...
Beam loading in a laser-plasma accelerator using a near-hollow plasma channel
Schroeder, Carl
2014-01-01
Beam loading in laser-plasma accelerators using a near-hollow plasma channel is examined in the linear wake regime. It is shown that, by properly shaping and phasing the witness particle beam, high-gradient acceleration can be achieved with high-efficiency, and without induced energy spread or emittance growth. Both electron and positron beams can be accelerated in this plasma channel geometry. Matched propagation of electron beams can be achieved by the focusing force provided by the chan...
Load history-based model for prestressed concrete beam damage evaluation
Yuan Jianli; Wang Yi; Qian Zhonghui
2007-01-01
The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening.An experimental study on the hysteretic characteristics of prestressed concrete frame beams under different loading histories was performed to explore the influence of load history on energy dissipation and failure characteristics of the member.Based on the test results,the failure of the beam is defined,and the relationship between the failure moment under cyclic load and from the skeleton curve is formulated.Finally,based on displacement and energy dissipation,a model for prestressed concrete beam damage-failure evaluation is developed.In this model,the effect of deformation level,cumulative dissipated energy,and loading history on prestressed concrete beam damage-failure is incorporated,thus it is applicable to stochastic earthquake forces.
Numerical analysis of prestressed reinforced concrete beam subjected to blast loading
Highlights: • Numerical study of prestressed RC beam against blast loadings by using LS-DYNA. • Numerical model is calibrated with testing results available. • The prestress is pre-applied on the RC beam in an analytical approach. • Parametric studies on prestress, concrete compressive strength and blast load. • Blast resistance performance of prestressed beam is identified. - Abstract: Prestressing technique has been widely used in civilian and military constructions. The prestressed reinforced concrete (RC) structural components such as beams and columns usually outperform the non-prestressed RC components because prestressing not only increases the structural stiffness and load carrying capacity, but also has higher crack resistance than non-prestressed component. As a result, it usually leads to light structures. The investigation of non-prestressed RC components subjected to blast loadings has been reported in the literature. However, the study on the blast-resistant capacity of prestressed RC components is very limited. In this study, the dynamic response of a simply-supported prestressed RC beam with rectangular section under blast loadings is numerically investigated by using finite element codes LS-DYNA. The prestress is pre-applied on the RC beam in an analytical approach. The reliability of the numerical model is calibrated with testing results available in the literature. With the calibrated model, numerical simulations on four groups of prestressed RC beams to blast loadings are carried out to investigate the influences of prestressing level and concreted compressive strength on beam blast loading resistance capacity. The structural responses such as mid-span maximum deflection, residual deflection, cracking, stress of rebars and shear stress of concrete near the supports are extracted from the numerical results. The effectiveness of prestressing on blast-resistant capacity of RC beam is demonstrated through comparing the results with the
A model for the calculation of the elastic-plastic behaviour of beams loaded with impact loads in the longitudinal and the transverse direction is developed. The description of the thrust and bending deformation due to dynamic material stresses is done using Timoshenko's beam model. The basic equations lead to systems of hyperbolic partial differential equations, which are quasi-linear in the case of plastic deformation. They describe the spread of normal, bending and thrust waves in the beam. In order to solve the partial differential equations, a numerical process is built up using the characteristic method, which permits the calculation of the dynamic behaviour of general structures consisting of various beams. (orig./HP)
Kanematsu, Nobuyuki; Ogata, Risa
2012-01-01
Purpose: Beam range control is the essence of radiotherapy with heavy charged particles. In conventional broad-beam delivery, fine range adjustment is achieved by insertion of range shifting and compensating materials. Ideally, such material should be water equivalent as well as that for dosimetry. In this study, we evaluated dosimetric water equivalency of four common plastics, HDPE, PMMA, PET, and POM, by uniformity of effective densities for carbon-ion-beam interactions. Methods: Using the Bethe formula for stopping, the Gottschalk formula for multiple scattering, and the Sihver formula for nuclear interactions, we calculated the effective densities of the plastics for these interactions. We tested HDPE, PMMA, and POM in carbon-ion-beam experiment and measured attenuations of carbon ions, which were compared with empirical linear-attenuation-model calculations. Results: The theoretical calculations resulted in reduced multiple scattering and increased nuclear interactions for HDPE compared to water, which ...
RC beam strengthened with pre-stressed CFP under the secondary load
LONG Bang-yun; YUAN Guang-lin; ZHU Dan-yu
2008-01-01
Feasibility of using pre-stressed carbon fiber plates to strengthen reinforced concrete beams was studied. Based on the characteristics of carbon fiber plates, we developed a pre-stress clamp and a device for applying the pre-stress. Contrast tests were conducted between ordinary carbon fiber plates and a pre-stressed carbon fiber plate and between secondary loaded carbon fiber plates and a concrete beam strengthened with a secondary loaded carbon fiber plate. On this basis, we analyzed the failure pattern,the width of cracks and their distribution, the cracking load, the yield load, the limit load and the relation between load and deflection. The results indicate that using pre-stressed carbon fiber plates to strengthen concrete beams is feasible and effective.
Research on crack width evolution of RC beams strengthened with CFL under cyclic loads
Zhao, Chen; Huang, Peiyan; Guo, Xinyan
2008-11-01
Using carbon fiber laminate (CFL) invented by our group, we take the lead in studying the fatigue behaviors of the beams strengthened with FRP under the cyclic loads. The maximum crack width of the RC beams strengthened with CFL conforms to the law of three-stages, and the main factors which affect the fatigue crack propagation behavior was analyzed. Theoretical analyses are performed for the evolvement rule of maximum crack width of the strengthened RC beams under constant amplitude and random fatigue loads. Then, a method for calculating the propagation rule of maximum flexural crack width under fatigue loads is proposed, based on the initial crack width under static loads and the coefficient of the strain of CFL. This method can be used not only for crack width determination under constant amplitude cyclic load but also the random fatigue load. Using the method, permissive fatigue life can be estimated.
Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers
Neumann, Axel
2008-07-21
In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10{sup -4} in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)
Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers
In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10-4 in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)
Application of sinusoidal load-change operation in order to compensate daily power demand variations
In order to balance the daily variations of electric power demand a method for choosing optimal load management of nuclear power plants with PWR type reactors is presented. It is based on an approximate harmonic analysis of the daily load distribution
Ultimate load analysis of pretensioned inverted T-beams with circular web openings
Hock Tian CHENG; Bashar S. MOHAMMED; Kamal Nasharuddin MUSTAPHA
2009-01-01
The provision of transverse openings in floor beams to facilitate the passage of utility pipes and service ducts not only results in a more systematic layout of pipes and ducts, it also translates into substantial economic savings in the construction of a multi-storey building. In this paper, ultimate load analysis of statically loaded simply supported pretensioned inverted T-beams with circular web openings is presented. Major findings relevant to ultimate load analysis of pretensioned beams with circular web openings are summarized. An attempt has been made to answer the frequently asked questions related to ultimate load analysis on multiple circular web open-ings. It has been shown that the analysis method for pretensioned beams with multiple large circular web openings can be further simplified without sacrificing rationality.
Sauppe, Sebastian; Hahn, Andreas; Brehm, Marcus; Paysan, Pascal; Seghers, Dieter; Kachelrieß, Marc
2016-03-01
We propose an adapted method of our previously published five-dimensional (5D) motion compensation (MoCo) algorithm1, developed for micro-CT imaging of small animals, to provide for the first time motion artifact-free 5D cone-beam CT (CBCT) images from a conventional flat detector-based CBCT scan of clinical patients. Image quality of retrospectively respiratory- and cardiac-gated volumes from flat detector CBCT scans is deteriorated by severe sparse projection artifacts. These artifacts further complicate motion estimation, as it is required for MoCo image reconstruction. For high quality 5D CBCT images at the same x-ray dose and the same number of projections as todays 3D CBCT we developed a double MoCo approach based on motion vector fields (MVFs) for respiratory and cardiac motion. In a first step our already published four-dimensional (4D) artifact-specific cyclic motion-compensation (acMoCo) approach is applied to compensate for the respiratory patient motion. With this information a cyclic phase-gated deformable heart registration algorithm is applied to the respiratory motion-compensated 4D CBCT data, thus resulting in cardiac MVFs. We apply these MVFs on double-gated images and thereby respiratory and cardiac motion-compensated 5D CBCT images are obtained. Our 5D MoCo approach processing patient data acquired with the TrueBeam 4D CBCT system (Varian Medical Systems). Our double MoCo approach turned out to be very efficient and removed nearly all streak artifacts due to making use of 100% of the projection data for each reconstructed frame. The 5D MoCo patient data show fine details and no motion blurring, even in regions close to the heart where motion is fastest.
Vasilyan, Suren; Rivero, Michel; Schleichert, Jan; Halbedel, Bernd; Fröhlich, Thomas
2016-04-01
In this paper, we present an application for realizing high-precision horizontally directed force measurements in the order of several tens of nN in combination with high dead loads of about 10 N. The set-up is developed on the basis of two identical state-of-the-art electromagnetic force compensation (EMFC) high precision balances. The measurement resolution of horizontally directed single-axis quasi-dynamic forces is 20 nN over the working range of ±100 μN. The set-up operates in two different measurement modes: in the open-loop mode the mechanical deflection of the proportional lever is an indication of the acting force, whereas in the closed-loop mode it is the applied electric current to the coil inside the EMFC balance that compensates deflection of the lever to the offset zero position. The estimated loading frequency (cutoff frequency) of the set-up in the open-loop mode is about 0.18 Hz, in the closed-loop mode it is 0.7 Hz. One of the practical applications that the set-up is suitable for is the flow rate measurements of low electrically conducting electrolytes by applying the contactless technique of Lorentz force velocimetry. Based on a previously developed set-up which uses a single EMFC balance, experimental, theoretical and numerical analyses of the thermo-mechanical properties of the supporting structure are presented.
Large deflection response of restrained steel beams under fire and explosion loads
Xi, Feng
2016-01-01
A numerical study on the response of steel beams to fire and explosion is presented in this paper. First, a unified computing model, which can be used to simulate the behaviour of beams under four loading scenarios that involve fire and explosion or impact, is constructed. The proposed technique allows complete transparency of the influence of the various parameters on the structural behaviour. Second, the effects of load level on critical temperature are analyzed for various static and explo...
Performance of composite I-beams under axial compression and bending load modes
Khalid, Y.A.; Ali, F.A.; Sahari, B.B.; Saad, E.M.A
2005-04-15
An experimental and finite-element analyses for glass/epoxy composite I-beams have been carried out. Four, six, eight and 10 layers of woven fabric glass/epoxy composite I-beams were fabricated by a hand lay-up (molding) process. Quasi-static axial crushing and bending loading modes were used for this investigation. The load-displacement response was obtained and the energy absorption values were calculated for all the composite I-beams. Three tests were done for each composite I-beams type and each loading case for the results conformation. The second part of this study includes the elastic behavior of composite I-beams of the same dimensions and materials using finite-element analysis. The woven fabric glass/epoxy composite I-beams mechanical properties have been obtained from tensile tests. Results from this investigation show that the load required and the specific energy absorption for composite I-beams under axial compression load were higher than those for three and four point bending. On the other hand, the loads required for composite I-beams under four point bending were higher than those for three point bending, while the specific energy absorption for composite I-beams under three point bending were higher than those for four point bending. The first crushing loads difference between the experimental and finite-element results fell in the 3.6-10.92% range for axial compression tests, while fell in the 1.44-12.99% and 4.94-22.0% range for three and four point bending, respectively.
顾文娟; 刘涛; 朱战霞; 孙力
2013-01-01
Through the servo loading system and the position synchronization afterburner compensate for load analysis,the proportion of a position to follow the force compensation loading system,and its MATLAB / SIMULINK modeling and simulation are presented.Finally,the position proportional follow the force compensating loading system simulation results,the results indicate that the system can effectively improve the system band.%通过对力伺服加载系统和位置同步加力补偿加载系统的分析,提出了一种位置比例跟随力补偿加载系统；并对其进行MATLAB/SIMULINK建模仿真.最后,对位置比例跟随力补偿加载系统的仿真结果进行了分析,结果说明该系统能够有效提高系统频带.
Lu Sun; Feiquan Luo; Tung-Huei Chen
2005-01-01
Beam responses under an impact NDT load are studied using the Fourier and Laplace transforms. Numerical computation is performed for a parametric study of beam and load parameters. It is shown that under an impact load, the time duration for displacement to vanish is ten times longer than that for velocity and acceleration. The maximum response is achieved first in acceleration, followed by velocity, and finally displacement, all of which occur before the impact load is removed. At the moment that the impact load is removed from the beam, there is a discontinuity in the velocity and acceleration responses, but not in displacement response. The effect of K and ph on beam response is much less significant than that of EI and C, which have similar effect on beam response. As EI increases, peak values of displacement, velocity and acceleration response decrease. The effect of K on beam response only becomes appreciable after the impact load is removed.While the peak of displacement remain almost unchanged as K increases, the displacement response decays to zero faster for large K values than for small K values.
Cyclic loadings on steel and lightweight concrete composite beams
Valente, Isabel; Cruz, Paulo J. S.
2006-01-01
This communication describes the experimental cyclic tests performed on steel and high strength lightweight concrete composite beams, at Universidade do Minho, Portugal. The experimental study involves tests on simply supported beams, all with the same geometrical disposition, supports and materials. Headed studs are used to provide the connection between the steel profile and the lightweight concrete slab. The parameters in study are the stud disposition and the number and range of the...
Beam heat load measurements in the cold bore superconductive undulator in ANKA
Casalbuoni, S; Hagelstein, M; Zimmermann, F; Rossmanith, Robert; Kostka, Barbara; Mashkina, Elena; Steffens, Erhard; Bernhard, Axel; Wollmann, Daniel; Baumbach, Tilo
2007-01-01
Measurements of the beam-induced heat load in the ANKA cold-bore superconductive undulator are summarized. The strength of the two dominating effects, resistive wall heating and heating by electron bombardment, depends on the beam parameters and the gap width.
Hanhijärvi, A.; Galimard, P.; Hoffmeyer, Preben
1998-01-01
The paper is the second in a series which sums up the results of an extensive project to quantify the duration-of-load (DOL) effect on different sized timber beams in different climates. The paper deals with straight (unnotched) beams. The results of various DOL-tests of stepwise and constant ben...
Birefringence compensation in single solid-state rods
Various methods for compensating birefringence depolarization in solid-state rods are theoretically and experimentally analyzed and compared. Gaussian and flat top beam profiles are investigated. The efficiency in depolarization loss reduction using different techniques is discussed in terms of beam profile, rod fill factor, and thermal heat load. In Nd:yttrium-aluminum-garnet, the depolarization loss can be efficiently reduced below 5% with a compensating quarter-waveplate, up to 20 W heat load for a flat top beam and up to 70 W for a gaussian beam. (c) 2000 American Institute of Physics
Semina Yuliya Anatol'evna
2015-09-01
Full Text Available The behavior of reinforced concrete elements under some types of cyclic loads is described in the paper. The main aim of the investigations is research of the stress-strain state and strength of the inclined sections of reinforced concrete beam elements in conditions of systemic impact of constructive factors and the factor of external influence. To spotlight the problem of cyclic loadings three series of tests were conducted by the author. Firstly, the analysis of the tests showed that especially cyclic alternating loading reduces the bearing capacity of reinforced concrete beams and their crack resistance by 20 % due to the fatigue of concrete and reinforcement. Thus the change of load sign creates serious changes of stress-strain state of reinforced concrete beam elements. Low cycle loads of constant sign effect the behavior of the constructions not so adversely. Secondly, based on the experimental data mathematical models of elements’ strength were obtained. These models allow evaluating the impact of each factor on the output parameter not only separately, but also in interaction with each other. Furthermore, the material spotlighted by the author describes stress-strain state of the investigated elements, cracking mechanism, changes of deflection values, the influence of mode cyclic loading during the tests. Since the data on the subject are useful and important to building practice, the ultimate aim of the tests will be working out for improvement of nonlinear calculation models of span reinforced concrete constructions taking into account the impact of these loads, and also there will be the development of engineering calculation techniques of their strength, crack resistance and deformability.
A Technique for Temperature and Ultimate Load Calculations of Thin Targets in a Pulsed Electron Beam
Hansen, Jørgen-Walther; Lundsager, Per
1979-01-01
A technique is presented for the calculation of transient temperature distributions and ultimate load of rotationally symmetric thin membranes with uniform lateral load and exposed to a pulsed electron beam from a linear accelerator. Heat transfer by conduction is considered the only transfer...... mechanism. The ultimate load is calculated on the basis of large plastic strain analysis. Analysis of one aluminum and one titanium membrane is shown....
Hong, C. U.; Gozu, S.; Okayasu, J.; Koyano, M.; Katayama, S.; Hori, H.; Yamada, S.
1998-06-01
We have investigated GaAs films epitaxially grown by molecular beam epitaxy (MBE) using a valved As-cracker source. When the cracking temperature ( Tc) of the As-valved cracker cell is raised, which means the dominant As species changes from As 4 to As 2, the conduction type of the films changed from p - to n -. In order to clarify the origins of the change of compensation mechanism of those GaAs films, estimations were made using electrical (Hall effect) and optical (photoluminescence and far-infrared) measurements. Impurity incorporation behaviors suggested by these estimations are found to give a reasonable explanation for the change of conduction type, that is, the change of compensation mechanism.
A method for compensating bellows pressure loads while accommodating thermal deformations
Many metal bellows are used on storage ring vacuum chambers. They allow the ring to accomodate deformations associated with alignment, mechanical assembly and thermal expansion. The NSLS has two such electron storage rings, the VUV ring and the X-Ray ring. Both rings utilize a number of welded metal bellows within the ring and at every beam port
Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions
Highlights: ► Effects of wider range of loading rates on dynamic shear behavior of RC deep beams. ► Experimental investigation of RC deep beam with and without shear reinforcements. ► Verification of experimental results with truss model and FE simulation results. ► Empirical equations are proposed to predict the dynamic increase factor of maximum resistance. -- Abstract: Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading
Madheswaran, C. K.; Ambily, P. S.; Dattatreya, J. K.; Ramesh, G.
2015-06-01
This work describes the experimental investigation on behaviour of reinforced GPC beams subjected to monotonic static loading. The overall dimensions of the GPC beams are 250 mm × 300 mm × 2200 mm. The effective span of beam is 1600 mm. The beams have been designed to be critical in shear as per IS:456 provisions. The specimens were produced from a mix incorporating fly ash and ground granulated blast furnace slag, which was designed for a compressive strength of 40 MPa at 28 days. The reinforced concrete specimens are subjected to curing at ambient temperature under wet burlap. The parameters being investigated include shear span to depth ratio (a/d = 1.5 and 2.0). Experiments are conducted on 12 GPC beams and four OPCC control beams. All the beams are tested using 2000 kN servo-controlled hydraulic actuator. This paper presents the results of experimental studies.
Numerical prediction of wave impact loads on multiple rectangular beams
Mayer, Stefan; Nielsen, Kristian Bendix; Hansen, E.A.
2005-01-01
Wave impact on one and two structural beams with rectangular cross section is simulated with a two-dimensional finite volume method, solving the unsteady Euler equations and employing a VOF-type method for the description of the free surface. Four different test series are carried out, each...
Flexural models of reinforced concrete beams under blast load
Stochino, Flavio
2013-01-01
Nowadays, the issue of structural safety under blast loading has become a dramatic problem. The tragic news of the terrorist attacks of recent years (9/11/2001, New York; 7/7/2005, London; 7/23/2005, Sharm El Sheik; 1/24/2011, Moscow; etc), raise important, urgent questions regarding the real safety and reliability of our buildings. Extreme loads such as impacts, explosions, etc., can occur in everyday life with unexpectedly high frequency. Actually, the problem of terrorist attacks, so...
Experimental Study on Impact Load Resistance of RC Beam with Corroded Reinforcement
Kuwahara Isao
2016-01-01
Full Text Available In Japan, many concrete bridges along the coastline have suffered corrosion due to the chloride attack from seawater and airborne salt. Therefore, now, several researches on corroded RC structures have been ongoing around the world. Especially, as a basic research, many researchers have studied on the numerical and experimental method to evaluate static load resistant capacity of RC beams with corroded reinforcements. However, there has been almost no research to evaluate impact load resistant capacity. Of course, it is important that impact load resistant capacity is clarified, if the possibility of acting of impact load including in natural disaster on corroded RC structures is dealt with. With a background like this, this paper describes an experimental investigation of the structural behavior of corroded RC beams. To be precise, in this study, RC beams with corroded reinforcement by using electrolytic corrosion method were made, and both of static loading test and repeated impact test for those RC beams were conducted in order to clarify the static and impact load resistant capacity of them. As a result, we could get some findings. At first, through repeated impact tests (which has 1.0m/s impact velocity and a 100kg steel weight, the number of impacts to the failure of corroded RC beams were less than half of healthy RC beams. It was also found that fracture pattern was completely different due to some axial cracks by corrosion. In addition, even though the corrosion rate is same level, the impact load resistant capacity reduce greatly compared to the static load resistant capacity because of the existence and pattern of cracks due to corrosion.
On the dynamic stability of shear deformable beams under a tensile load
Caddemi, S.; Caliò, I.; Cannizzaro, F.
2016-07-01
Loss of stability of beams in a linear static context due to the action of tensile loads has been disclosed only recently in the scientific literature. However, tensile instability in the dynamic regime has been only marginally covered. Several aspects concerning the role of shear deformation on the tensile dynamic instability on continuous and discontinuous beams are still to be addressed. It may appear as a paradox, but also for the case of the universally studied Timoshenko beam model, despite its old origin, frequency-axial load diagrams in the range of negative values of the load (i.e. tensile load) has never been brought to light. In this paper, for the first time, the influence of a conservative tensile axial loads on the dynamic behaviour of the Timoshenko model, according to the Haringx theory, is assessed. It is shown that, under increasing tensile loads, regions of positive/negative fundamental frequency variations can be distinguished. In addition, the beam undergoes eigen-mode changes, from symmetric to anti-symmetric shapes, until tensile instability of divergence type is reached. As a further original contribution on the subject, taking advantage of a new closed form solution, it is shown that the same peculiarities are recovered for an axially loaded Euler-Bernoulli vibrating beam with multiple elastic sliders. This latter model can be considered as the discrete counterpart of the Timoshenko beam-column in which the internal sliders concentrate the shear deformation that in the Timoshenko model is continuously distributed. Original aspects regarding the evolution of the vibration frequencies and the relevant mode shapes with the tensile load value are highlighted.
STEADY-STATE RESPONSE OF A TIMOSHENKO BEAM ON AN ELASTIC HALF-SPACE UNDER A MOVING LOAD
Chen Yunmin; Wang Changjing
2006-01-01
By introducing the equivalent stiffness of an elastic half-space interacting with a Timoshenko beam, the displacement solution of the beam resting on an elastic half-space subjected to a moving load is presented. Based on the relative relation of wave velocities of the half-space and the beam, four cases with the combination of different parameters of the half-space and the beam, the system of soft beam and hard half-space, the system of sub-soft beam and hard halfspace, the system of sub-hard beam and soft half-space, and the system of hard beam and soft half-space are considered. The critical velocities of the moving load are studied using dispersion curves. It is found that critical velocities of the moving load on the Timoshenko beam depend on the relative relation of wave velocities of the half-space and the beam. The Rayleigh wave velocity in the half-space is always a critical velocity and the response of the system will be infinite when the load velocity reaches it. For the system of soft beam and hard half-space, wave velocities of the beam are also critical velocities. Besides the shear wave velocity of the beam, there is an additional minimum critical velocity for the system of sub-soft beam and hard half-space. While for systems of (sub-) hard beams and soft half-space, wave velocities of the beam are no longer critical ones.Comparison with the Euler-Bernoulli beam shows that the critical velocities and response of the two types of beams are much different for the system of (sub-) soft beam and hard half-space but are similar to each other for the system of (sub-) hard beam and soft half space. The largest displacement of the beam is almost at the location of the load and the displacement along the beam is almost symmetrical if the load velocity is smaller than the minimum critical velocity (the shear wave velocity of the beam for the system of soft beam and hard half-space). The largest displacement of the beam shifts behind the load and the asymmetry
This study introduces a new CFRC-strengthened RC beam model which can both strengthen and monitor the large-scale RC element used in concrete infrastructures. An experiment of testing four-point bending beams is proceeded in order to analyze mechanical behavior and electrical property of the designed beam under monotonic loading as well as the relationship between electrical property and fatigue damage under cyclic flexural loading. The analytical results indicate that this innovative CFRC-strengthened beam has better flexural performance due to the improved cracking resistance capacity of the CFRC layer. Besides, the change in electrical resistance of the beam is detected under monotonic loading. It is found that the thicker the CFRC layer, the larger the electrical resistance increases, and while electrical resistance irreversibly increases as load cycling progresses, the greater the stress amplitude, the greater the fatigue damage, and the larger the residual resistance increases. Based on this discovery, a new technique to monitor the damage of the designed CFRC-strengthened RC beam is produced by means of resistance measurement
Iida, Naoko; Kikuchi, Mitsuo; Mimashi, Toshihiro; Nakayama, Hisayoshi; Sakamoto, Yutaka; Satoh, Kotaro; Takasaki, Seiji; Tawada, Masafumi
2013-03-01
The KEKB collider achieved a maximum peak luminosity of 2.1×1034 cm-2 s-1 and an integrated luminosity of 1 ab-1 in its ten-year operation. Behind these glorious records there have been uncountable improvements in every subsystem. This paper describes the improvements in the beam transport line, injection kickers, septum magnets, the beam-abort system, and a newly developed pulsed-quadrupole system in detail.
An exact dynamic stiffness matrix for axially loaded double-beam systems
Li Xiaobin; Xu Shuangxi; Wu Weiguo; Li Jun
2014-06-01
An exact dynamic stiffness method is presented in this paper to determine the natural frequencies and mode shapes of the axially loaded double-beam systems,which consist of two homogeneous and prismatic beams with a distributed spring in parallel between them.The effects of the axial force, shear deformation and rotary inertia are considered, as shown in the theoretical formulation. The dynamic stiffness influence coefficients are formulated from the governing differential equations of the axially loaded double-beam system in free vibration by using the Laplace transform method. An example is given to demonstrate the effectiveness of this method, in which ten boundary conditions are investigated and the effect of the axial force on the natural frequencies and mode shapes of the double-beam system are further discussed.
THE CRITICAL LOAD PARAMETER OF A TIMOSHENKO BEAM WITH ONE-STEP CHANGE IN CROSS SECTION
Goran Janevski
2014-12-01
Full Text Available The paper analyzes the transverse vibration of a Timoshenko beam with one-step change in cross-section when subjected to an axial force. The axial force is equal in both of the beam portions. Three types of beam which occur commonly in engineering application are considered. The frequency equation of the Timoshenko beam with one-step change in cross-section is expressed as the fourth order determinant equated to zero. The critical compressive axial force is expressed as a function of the critical load parameter which is tabulated for four classical boundary conditions. Apart from the results presented in Tables, the paper also provides calculated values of the critical load parameter for other values of system parameters along with the graphic representation of their dependence on the step position parameter.
The knowledge about degradation processes caused by Edge Localised Modes (ELMs) on plasma facing materials (PFMs) in future confinement experiments is essential to allow lifetime estimations for first wall and divertor components. Electron beam simulations of the occurring heat loads have the advantage to be able to work at higher frequencies compared to other experiments (e.g. plasma streams), allowing a large number of ELM-like heat pulses. This paper deals with the electron beam guidance method used in the JUDITH 2 facility in Forschungszentrum Juelich (Germany). As the beam is described well by a Gaussian profile with a variable FWHM, depending on several parameters, e.g. vacuum pressure, the guidance is of special interest in order to achieve an approximately homogeneous (ELM-like) loading. A circular pattern turned out to provide advantages, in particular related to an increased stability against beam width fluctuations.
Bending vibration of axially loaded Timoshenko beams with locally distributed Kelvin-Voigt damping
Chen, Wei-Ren
2011-06-01
Utilizing the Timoshenko beam theory and applying Hamilton's principle, the bending vibration equations of an axially loaded beam with locally distributed internal damping of the Kelvin-Voigt type are established. The partial differential equations of motion are then discretized into linear second-order ordinary differential equations based on a finite element method. A quadratic eigenvalue problem of a damped system is formed to determine the eigenfrequencies of the damped beams. The effects of the internal damping, sizes and locations of damped segment, axial load and restraint types on the damping and oscillating parts of the damped natural frequency are investigated. It is believed that the present study is valuable for better understanding the influence of various parameters of the damped beam on its vibration characteristics.
Pease, Bradley Justin; Geiker, Mette Rica; Stang, Henrik; Weiss, Jason
2006-01-01
Reinforced concrete structures are known to crack due to restrained shrinkage, temperature gradients, application of load, and expansive reactions. Cracks provide paths for rapid ingress of moisture, chlorides, and other aggressive substances, which may affect the long-term durability of the...... structure. For example, concrete cracks located at the reinforcing steel may contribute to a rapid corrosion initiation and propagation. Previous research has shown that cracked reinforced concrete under static flexural loading may have an increased ingress of chloride ions along the reinforcement/concrete...... interface. The aim of this paper is to provide a detailed description of the development of cracks in reinforced concrete under flexural load. Cracking at both realistic service load levels (1.0-1.8 times estimated cracking load) and unrealistically high service load levels (> 0.5 times beam capacity) has...
Eigenvalues of an axially loaded cantilever beam with an eccentric end rigid body
Lajimi, S Amir Mousavi
2014-01-01
An analytical form of the characteristic equation for a vertically mounted cantilever beam with an end rigid body is obtained and solved for the eigenvalues of the structure. The effect of the weight of the structure is taken into consideration by estimating the load as a function of the length of the beam. The mass, rotary inertia and eccentricity of the end rigid body are demonstrated to considerably affect the eigenvalues of the structure.
Veerman, R.P.; Koenders, E.A.B.
2014-01-01
Structural Health Monitoring (SHM) systems are frequently used in civil infrastructures. One important durability property in reinforced concrete (RC) structures is the level of steel bar corrosion. In a dynamic four-point-bending test, two beams are loaded simultaneously, in which corrosion is accelerated in one of them. Since geophones are commonly used in SHM systems to monitor vertical deformations and to calculate modal properties, the first natural frequency of both beams are analysed i...
Fangping Liu; Jianting Zhou
2016-01-01
Concrete fatigue strain evolution plays a very important role in the evaluation of the material properties of concrete. To study fatigue strain and fatigue damage of concrete in reinforced concrete beams under constant amplitude bending fatigue loading, constant amplitude bending fatigue experiments with reinforced concrete beams with rectangular sections were first carried out in the laboratory. Then, by analyzing the shortcomings and limitations of existing fatigue strain evolution equation...
Analysis of DESY-Flash LLRF Measurements for the ILC Heavy Beam Loading Test
Cancelo, Gustavo; Chase, Brian; Davidsaver, Michael; /Fermilab; Carwardine, J.; /Argonne; Simrock, Stefan; Ayvazyan, Valeri; Grecki, Mariusz; /DESY; Matsumoto, Toshihiro; Michizono, Shinichiro; /KEK, Tsukuba
2009-06-01
In September 2008 the DESY-FLASH accelerator was run with up to 550, 3 nano-coulomb bunches at 5 Hz repetition rate. This test is part of a longer-term study aimed at validating ILC parameters by operation as close as possible to ILC beam currents and RF gradients. The present paper reports on the analysis that has been done in order to understand the RF control system performance during this test. Actual klystron power requirements and beam stability are evaluated with heavy beam loading conditions. Results include suggested improvements for upcoming tests in 2009.
Analysis of DESY-Flash LLRF Measurements for the ILC Heavy Beam Loading Test
In September 2008 the DESY-FLASH accelerator was run with up to 550, 3 nano-coulomb bunches at 5 Hz repetition rate. This test is part of a longer-term study aimed at validating ILC parameters by operation as close as possible to ILC beam currents and RF gradients. The present paper reports on the analysis that has been done in order to understand the RF control system performance during this test. Actual klystron power requirements and beam stability are evaluated with heavy beam loading conditions. Results include suggested improvements for upcoming tests in 2009.
Hanhijärvi, A.; Galimard, P.; Hoffmeyer, Preben
1998-01-01
The paper is the second in a series which sums up the results of an extensive project to quantify the duration-of-load (DOL) effect on different sized timber beams in different climates. The paper deals with straight (unnotched) beams. The results of various DOL-tests of stepwise and constant...... bending of LVL and glulam beams are reported and results of modelling outlined. It is concluded that in cyclically varying climate large cross-sections are less affected by the DOL-effect than smaller ones. The results do not show marked difference between LVL and glulam in susceptibility to the DOL-effect...
Changguo Wang; Huifeng Tan; Xingwen Du
2009-01-01
This paper extends Le van's work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a pre-stressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko's beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our pro-posed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the load-carrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.
A cyclic loading model for beam-to-column web connection
LIU Hong-bo; XIE li-li; SHAO Yong-song
2008-01-01
A finite element analysis of the beam-to-column web connection with H-shaped columns was performed using the ANSYS computer program.Based on the finite element analysis and theoretical analysis,a simplified model was developed to describe the cyclic loading behavior of beam-to-columns web connection in steel moment resisting frames,considering both bending and shear deformation modes of the beam flange plate.Several issues appearing to merit further researches were identified in the process of developing this model,such as the effect of beam flange plate on beam-to-column web connection stiffness and strength.A reasonable agreement was achieved between model predictions and finite element data,which verified the feasibihty of the proposed model.
Balance Component Decomposition and Compensation Method for Unbalanced Load%不平衡负载的平衡分量法分解及补偿方法
胡应宏; 王建赜; 任佳佳; 纪延超
2012-01-01
In order to make a better compensation for the three-phase unbalanced load, the unbalanced load was analyzed and a method of reactive compensation admittance calculation based on balance component method was proposed. Any neutral non-grounded three-phase load can be decomposed into a group of balanced load and single line load, and the load compensation admittance can be obtained by the decomposition of the three-phase unbalance load. The load compensation admittance calculation can be divided into three parts, the power factor compensation for the balanced load and the single line load together with the balanced compensation for the single line resistive load. Then, the ideal Steinmetz compensation network algorithm was amended under the condition of asymmetric voltage. A freedom degree existed in this case, and the asymmetry voltage compensation admittance can be accurately calculated according to the control objectives and the revised ideal compensation network calculation method. The rationality and validity of the method was verified using example and simulation. Compared with existing methods, the proposed method has easy calculation and convenient realization.%为了更好地对三相不平衡负荷进行平衡化补偿,对不平衡负载进行详细分析,提出一种新的基于平衡分量法的无功补偿导纳计算方法.首先,将任何中性点不接地的三相负载分解为平衡负载和一个线间负载之和,通过将三相负载进行分解,可以得到负载所需要补偿的导纳值.补偿导纳的计算可分为平衡负载功率因数补偿、线间负载功率因数补偿以及线间线阻性负载平衡化补偿3部分.然后,对系统电压不对称时的Steinmetz.理想补偿网络算法进行修正,根据控制目标和修正后的理想补偿网络算法,计算出系统电压不对称时所需的补偿导纳值.通过算例、仿真分析及实验验证,证明了所提无功补偿导纳计算方法的合理性和正确性,该方
PREDICTION OF FATIGUE LIVES OF RC BEAMS STRENGTHENED WITH CFL UNDER RANDOM LOADING
Rongwei Lin; Peiyan Huang; Chen Zhao; Xinyan Guo; Xiaohong Zheng
2008-01-01
The investigation on fatigue lives of reinforced concrete (RC) structures strength ened with fiber laminate under random loading is important for the repairing or the strengthening of bridges and the safety of the traffic.In this paper,two methods are developed for predicting the fatigue lives of RC structures strengthened with carbon fiber laminate (CFL) under random loading based on a residual life and a residual strength model.To discuss the efficiency of the model,12 RC beams strengthened with CFL are tested under random loading by the MTS810 testing system.The predicted residual strength approximately agrees with test results.
Large deflection analysis of cantilever beam under end point and distributed load
Kimiaeifar, Amin; Tolou, N; Barari, Amin;
2014-01-01
distributed loads. Direct nonlinear solution by use of homotopy analysis method was implemented to drive the semi-exact solution of trajectory position of any point along the beam length. For the purpose of comparison, the deflections were calculated and compared to those of finite element method which was...
Large deflection response of restrained steel beams under fire and explosion loads.
Xi, Feng
2016-01-01
A numerical study on the response of steel beams to fire and explosion is presented in this paper. First, a unified computing model, which can be used to simulate the behaviour of beams under four loading scenarios that involve fire and explosion or impact, is constructed. The proposed technique allows complete transparency of the influence of the various parameters on the structural behaviour. Second, the effects of load level on critical temperature are analyzed for various static and explosion load ratios. Two cases of explosion and fire loading sequences are compared, it is shown that the critical temperature of the beam subjected to fire followed by an explosion is lower than that of the beam subjected to an explosion followed by fire. The influence of temperature on the p-i diagram is investigated, an iso-damage surface is introduced to distinguish safe and unsafe regions. Third, the limiting temperature criteria are further examined. That is, the first and second limiting temperatures can be determined when the dimensional catenary force is equal to zero or to one, which corresponds to the bending or stretching plastic hinge, respectively. PMID:27386235
Design of pulsed heat load removal system for JT-60 neutral beam injectors
Restrictions imposed on the heat removal system for JT-60 Neutral Beam Injectors are very severe. Since it handles a large amount of pulsed heat load, the system tends to be very large, if it is designed based on a conventional method. Such a design would be unreasonable, if we consider about construction fee as well as space allowed for it. In the present report, we have taken into account the transient state of pulsed heat load and have tried to design the heat load removal system suffering pulsed heat load to be very compact. As a result of the design, it turned out that the system can be made in a scale which is less than 1/10 of the conventional design. This design is also applied to heat load removal system for the prototype-NBI for JT-60. (author)
Tests and calculations of reinforced concrete beams subject to dynamic reversed loads
This study presents the tests of a reinforced concrete beam conducted by the Department of Mechanical and Thermal Studies at the Centre d'Etudes Nucleaires, Saclay, France. The actual behavior of nuclear power plant buildings submitted to seismic loads is generally non linear even for moderate seismic levels. The non linearity is specially important for reinforced concrete beams type buildings. To estimate the safety factors when the building is designed by standard methods, accurate non linear calculations are necessary. For such calculations one of the most difficult point is to define a correct model for the behavior of a reinforced beam subject to reversed loads. For that purpose, static and dynamic experimental tests on a shaking table have been carried out and a model reasonably accurate has been established and checked on the tests results
Neutron spectra at two beam ports of a TRIGA Mark III reactor loaded with HEU fuel
The neutron spectra have been measured in two beam ports, one radial and another tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research in Mexico. Measurements were carried out with the reactor core loaded with high enriched uranium fuel. Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a 6LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter high-density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code. For each spectrum total flux, mean energy and ambient dose equivalent were determined. Measured spectra show fission, epithermal and thermal neutrons, being harder in the radial beam port. - Highlights: • Neutron spectra of a TRIGA reactor were measured. • The reactor core is loaded with HEU. • The spectra were measured at two reactor beam ports. • Measurements were carried out at 5 and 10 W
Researches on Fuzzy Creep Compensation of Load Cell%称重传感器蠕变的模糊补偿方法研究
朱子健; 陈仁文
2002-01-01
本文介绍了对传感器蠕变进行补偿的新方法,首次引入模糊识别的方法来确定载荷的变化情况,该方法可实现蠕变实时精确补偿,简便易行,避免了繁琐的传感器蠕变模型的建立和实现过程.实验证明这种方法精度很好.%Creep is a critical specification of load cell. Based on the analysis of creep, a new compensation technique, fuzzy creep compensation, is presented in this paper. It firstly introduces the fuzzy recognition to determine loading situations. Compared to the other compensation methods, fuzzy creep compensation can avoid the complicated modeling of creep performance, and it is also proved to be an efficient and simple approach to improve the accuracy of load cell by experiments.
Zhu, Fan; Tan, Xinran; Tan, Jiubin; Fan, Zhigang
2016-08-01
An autocollimation (AC) setup with ultra-high resolution and stability for micro-angle measurement is presented. The telephoto objective, which is characterized in long focal length at a compact structure size, and the optical enlargement unit, which can magnify the image displacement to improve its measurement resolution and accuracy, are used to obtain an ultra-high measurement resolution of the AC. The common-path beam drift compensation is used to suppress the drift of measurement results, which is evident in the high-resolution AC, thus to obtain a high measurement stability. Experimental results indicate that an effective resolution of better than 0.0005 arc sec (2.42 nrad) over a measurement range of ±30 arc sec and a 2-h stability of 0.0061 arc sec (29.57 nrad) can be achieved. PMID:27587181
范瑞祥; 吴素农; 孙旻; 宋强
2011-01-01
A relocatable cascade distribution static synchronous compensator (D-STATCOM) is presented to meet the power quality requirement of distribution network when impulse loads connecting. Operating with switching capacitor branch, the compensator realizes the synchronous compensation of reactive power. As the example of the application in Jiangxi power grid, the compensation requirement of electric arc furnace which is typical impulse load was analyzed. With field wave recording data and distribution system parameter, simulation model was built. By using frequency dividing coordination control method, the active power compensator can work with switching capacitor branch perfectly. It reduced the dynamic capacity requirement of the compensating system effectively. The active power compensator realized moveable by accepting the cascade main circuit and modularization design. The field application plan of the equipment was put forward. The system parameter configuration method and principle were also given in detail. The operation effect shows that with the fast responding speed and working stability, the equipment can meet the compensation requirement of Var shock in distribution network.%针对冲击性负荷接入配电网后带来的电能质量问题,提出一种基于链式结构的静止同步补偿器(D-STATCOM)的移动型并联有源补偿装置,与固定电容补偿装置形成良好配合,实现了无功的实时动态补偿.以江西电网实例应用为基础,分析以电弧炉为代表的典型冲击性负荷补偿的具体需求,结合现场录波数据和配电系统参数建立仿真模型,应用分频协调控制策略与固定补偿支路形成良好配合,降低了动态容量需求,采用链式主电路和模块化设计实现了有源型补偿装置D-STATCOM的移动化.提出了装置的现场应用方案,给出了基本工程参数的配置方法与原则.投运效果表明,装置响应迅速,运行稳定,能够满足配电网动态无功冲击补偿的要求.
Extrinsic Influence of Environment-Induced Degradation on Load Carrying Capacity of Steel Beams
Gowda, Sunil; Patnaik, A.; Payer, J.; Srivatsan, T. S.
2015-11-01
In this paper, the results of a study aimed at evaluating the strength of wide-flanged beams subjected to corrosion-induced damage, modeled using a standard finite element program (ABAQUS) is presented and discussed. Typical beams in consideration were subjected to different cases of corrosion-induced damage, such as non-uniform and varying degree of material loss that simulates pitting corrosion. Many variables, such as (a) shape of pitting damage, (b) location of pits along the length of the beam, (c) number of pits, and (d) depth of pits, were considered to facilitate a better understanding of the load carrying capacity of steel I-beams having damage quite similar to pitting damage to the web. The results are compared with an "as-new" beam for purpose of evaluation of the reduction in strength due to environment-induced deterioration. A "corrosion strength reduction factor (CSRF)" is introduced to help identify the reduction in load carrying capacity as a consequence of both height and depth of the damage due to corrosion. The results are presented in charts for purpose of practical beam design.
Electron beam excitation of a CSRR loaded waveguide for Cherenkov radiation
Sharples, Emmy; Letizia, Rosa
2015-09-01
A novel metamaterial structure is presented for applications as a backward propagating Cherenkov source or Cherenkov detector. The structure comprises of a complementary split ring resonator (CSRR) metasurface loaded waveguide, which exhibits left handed behaviour between 5-6 GHz. When the left handed, TM-like mode couples with an incident electron beam, backward propagating Cherenkov radiation is observed. The structure is suitable for beam-based applications, exhibiting strong beam coupling parameters and significant excitation of longitudinal wakefields. Three dimensional particle in cell simulations are performed to identify a suitable beam for operation. High and low energy beams, with different bunch dimensions from the literature, are considered and compared to investigate the nature of the beam-wave interaction this structure can support, and to identify any required modification before beam tests can be performed. This structure can lead to new solutions for non-destructive beam diagnostics, wakefield acceleration and backward wave oscillators which can potentially be scaled to higher frequency ranges.
Temperature error compensation for load cell based on RBFNN*%基于RBFNN的称重传感器温度误差补偿
杨进宝; 倪芳英; 张建军
2011-01-01
Load cell has nonlinear error because of different ambient temperature in work, and it is necessary to compensate. The principle of temperature error of load cell is illustrated, and a method for compensating this error based on radial basis function neural network (RBFNN) is proposed. The training algorithm of RBFNN is described. Using this proposed temperature error compensation method and the load cell which the weighing range is 100 kg,the experiments are implemented under 0 ～60℃. The results show that temperature errors of load cell are decreased, and its weighing accuracy is increased.%称重传感器存在因环境温度不同导致的非线性误差,需要进行补偿.阐述了称重传感器的温度误差机理,提出了一种基于径向基函数神经网络(RBFNN)的称重传感器温度误差补偿方法,并给出了训练算法.采用该方法,利用量程为100kg的称重传感器,在0～60℃范围内进行温度误差补偿实验.实验表明:采用这种方法补偿后,称重传感器温度误差大大减少,提高了称重准确度.