Beam Power Loss Research Articles

Estimated heat load and proposed cooling system in the FCC-ee interaction region

We discuss the beam power loss related to the heating of the beam pipe walls of the FCC-ee interaction region. We analyse the excitation of trapped modes, which can accumulate electromagnetic energy and determine the locations of these modes. We study the unavoidable resistive-wall wake field, which is responsible for the direct beam pipe walls heating. We show the distribution of the heat load along the central part of the interaction region. We also present the cooling system design and results for temperature distribution in interaction region in the operational mode.

Optimization-based mode selection scheme for OAM millimeter wave system in the off-axis misalignment case

Millimeter-wave transmission combined with Orbital Angular Momentum (OAM) has the advantage of reducing the loss of beam power and increasing the system capacity. However, to fulfill this advantage, the antennas at the transmitter and receiver must be parallel and coaxial; otherwise, the accuracy of mode detection at the receiver can be seriously influenced. In this paper, we design an OAM millimeter-wave communication system for overcoming the above limitation. Specifically, the first contribution is that the power distribution between different OAM modes and the capacity of the system with different mode sets are analytically derived for performance analysis. The second contribution lies in that a novel mode selection scheme is proposed to reduce the total interference between different modes. Numerical results show that system performance is less affected by the offset when the mode set with smaller modes or larger intervals is selected.

Beam dynamics challenges in linear colliders based on laser-plasma accelerators

In this paper we discuss design considerations and beam dynamics challenges associated with laser-driven plasma-based accelerators as applied to multi-TeV-scale linear colliders. Plasma accelerators provide ultra-high gradients and ultra-short bunches, offering the potential for compact linacs and reduced power requirements. We show that stable, efficient acceleration with beam quality preservation is possible in the nonlinear bubble regime of laser-plasma accelerators using beam shaping. Ion motion, naturally occuring for dense beams (i.e., low emittance and high energy) severely damps transverse beam instabilities. Coulomb scattering by the background ions is considered and it is shown that the strong focusing in the plasma strongly suppresses scattering-induced emittance growth. Betatron radiation emission from the transverse motion of the beam in the plasma will result in beam power loss and energy spread growth; however for sub-100 nm emittances, the beam power loss and energy spread growth will be sub-percent for multi-TeV-class plasma linacs.

Simulating the impact of charge exchange on beam ions in MAST-U

A model for simulating charge exchange (CX) of fast ions with background atoms in magnetically confined fusion plasmas has been implemented in the ASCOT orbit-following code. The model was verified by comparing simulated reaction mean free paths to analytical values across a range of fusion-relevant parameters. ASCOT was used to simulate beam ions slowing down in the presence of CX reactions in a MAST-U target scenario. ASCOT predicts the CX-induced loss of beam power to be , which agrees to within with the TRANSP prediction. Due to CX, plasma heating and current drive by beam ions are strongly reduced towards the edge. However, an overall lower but noticeable increase of up to in current drive is predicted closer to the core. The simulated deposition of fast CX atoms on the wall is concentrated around the outer midplane, with estimated peak power loads of 70–80 kW m−2 on the central poloidal field coils (P5) and the vacuum vessel wall between them. This analysis demonstrates that ASCOT can be used to simulate fast ions in fusion plasmas where CX reactions play a significant role, e.g. in spherical tokamaks and stellarators.

Beamforming Performance Analysis of Millimeter-Wave 5G Wireless Networks

With the rapid growth in the number of mobile devices and user connectivity, the demand for higher system capacity and improved quality-of-service is required. As the demand for high-speed wireless communication grows, numerous modulation techniques in the frequency, temporal, and spatial domains, such as orthogonal frequency division multiplexing (OFDM), time division multiple access (TDMA), space division multiple access (SDMA), and multiple-input multiple-output (MIMO), are being developed. Along with those approaches, electromagnetic waves’ orbital angular momentum (OAM) is attracting attention because it has the potential to boost the wireless communication capacity. Antenna electromagnetic radiation can be described by a sum of Eigen functions with unique eigenvalues, as is well known. In order to address such issues, the millimeter-wave (mmWave) communication is proposed which is considered as one of the potential technology for 5G wireless networks. The intrinsic feature of all electromagnetic waves is OAM. The OAM beams’ unique qualities have led to a slew of new uses. Broadband OAM generators, on the other hand, have gotten very little attention, especially in the mmWave frequency band. The use of OAM in conjunction with mmWave can reduce the beam power loss, enhance the received signal quality, and hence increase the system capacity. The transmitter and receiver antennas must be coaxial and parallel to achieve precise mode detection. The proposed mmWave integrated with OAM system model is discussed in this study. The channel model is created using the channel transition characteristics. The simulation results demonstrate that the proposed system model is a good way to boost the system capacity.

Optimization of Atomic Beam Power Loss in the Beamline of the TUMAN-3M Tokamak

Optimization of Atomic Beam Power Loss in the Beamline of the TUMAN-3M Tokamak

Beam dynamics design and error study of BISOL deuteron driver linac

The high intensity deuteron linac, one of the drivers of BISOL, aims to accelerate a continuous wave (cw) deuteron beam up to 40 MeV with a beam current of 20 mA, which can also be operated independently as the Multi-Aimed Intense Neutron Source (MAINS). As the high beam power and beam current, high reliability and strict beam loss are demand for the deuteron driver linac. The beam dynamics design of the driver linac, including the radio frequency quadrupole (RFQ), medium energy beam transport line (MEBT) and superconducting rf (SRF) linac, has been designed and optimized to meet the required requirements. In order to prevent halo formation and achieve strict beam losses, beam halo matching is implemented in our design. The simulation results predict a transmission efficiency of above 99% and the beam power losses meet requirements of less than l W/m in the SRF linac. Detailed error studies are performed to evaluate the sensitivity of the bean dynamics design at last. The general design considerations and the overall beam dynamics of the driver linac are presented in this paper.

Evaluation of detection ability of regional radar network in complex terrain based on digital elevation model: a sample study of Fujian province in China

Many countries employ weather radar networks to provide data for weather forecasting offices and research institutes, but most of the stations are located in mountainous regions, where terrain obstacles cause beam blockage. The authors propose a method for evaluating the detection ability of weather radars by combining radar range charts with iso-beam heights and maps of beam exposure intensity. First, methods of drawing radar range charts with iso-beam heights and maps of beam exposure intensity are introduced. Subsequently, the detection ability of the regional weather radar network in Fujian Province, China is evaluated by selecting data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM). During the evaluation, the radar coverage ratio, height–area index, and beam power loss ratio are chosen as indicators. These three parameters describe the radar coverage of Fujian Province from many aspects in detail. The main conclusions of this study are that radar range charts with iso-beam heights, and maps of beam exposure intensity can accurately indicate the detection ability of weather radars and that echo reflectivity needs to be corrected according to the beam exposure intensity rather than the degree of beam blockage caused by terrain obstacles.

Beam extraction characteristics of a low-energy, high-current pulsed ion source of a versatile experiment spherical torus neutral beam injector

A neutral beam (NB) ion source aimed to inject a 0.5-MW NB has been developed for Versatile Experiment Spherical Torus (VEST) plasma heating. Beam energy is generally limited to less than ∼20 keV to reduce particle orbit loss and beam shine-through. To meet this power demand, high-current ion beam extraction is important to achieve the required performance of the ion source. In this study, a 0.7-MW ion source was designed, fabricated, assembled, and optimized at the NB test stand in Korea Atomic Energy Research Institute (KAERI) considering the beam power losses in the beamline components. The ion source comprises a multicusped-bucket-type plasma generator and a multislot-triode-type ion accelerator with an extraction area of 12 cm × 46 cm. The characteristics of arc discharge and beam extraction were investigated using hydrogen gas to obtain the optimum operating parameters of the arc power, filament voltage, gas pressure, extraction voltage, and suppression voltage. The ion source was then conditioned and performance tests were primarily completed. Results of the experiments show that the ion source can extract sufficient ion beam power that is than 0.75 MW (50 A/15 keV) with 100-kW arc power. The arc efficiency and beam perveance were estimated to be 0.6 A/kW and 20–25 μP, respectively. Moreover, the design goal of delivering a 0.5-MW NB into the VEST plasma will be achievable based on the optimum operating conditions. This ion source has been installed in the VEST NB injection system at Seoul National University and its commissioning is ongoing.

Development of a 750-mm-long stripline kicker for HEPS

The superfast kickers are required for the HEPS storage ring on-axis injection system due to its very small dynamic aperture. A 750-mm-long stripline pair type of kicker prototype was researched and developed to demonstrate achieved performance of bandwidth, impedance, kicker strength, field uniformity and beam power loss. The cross sections of the kicker main body and the end of taper part are optimized for a good impedance matching and field uniformity. 3D simulation further optimizes the taper part to minimize the beam power loss and maintain a lower reflection. The high-voltage feedthrough is also designed and optimized by 3D CST. RF and high-voltage measurements are taken to verify the design of kicker assembly. The testing transmission odd-mode impedance is 50 ± 0.5 Ω, the even-mode impedance is 60 ± 0.5 Ω, and return loss is less than − 13 dB. The peak voltage and the rise time of pulse width inserting kicker assembly just decrease 3% of 20 kV and slow down 80 ps, respectively. RF testing results agree well with the simulation ones, which meet the design specification. The kicker assembly works well at ± 20 kV pulse.

High-accuracy diagnostic tool for electron cloud observation in the LHC based on synchronous phase measurements

Electron cloud effects, which include heat load in the cryogenic system, pressure rise, and beam instabilities, are among the main intensity limitations for the LHC operation with 25 ns spaced bunches. A new observation tool was proposed and developed to monitor the e-cloud activity and it has already been used successfully during the LHC run 1 (2010-2012) and it is being intensively used in operation during the start of the LHC run 2 (2015-2018). It is based on the fact that the power loss of each bunch due to e-cloud can be estimated using bunch-by-bunch measurement of the synchronous phase. The measurements were done using the existing beam phase module of the low-level rf control system. In order to achieve the very high accuracy required, corrections for reflection in the cables and for systematic errors need to be applied followed by a post-processing of the measurements. Results clearly show the e-cloud buildup along the bunch trains and its time evolution during each LHC fill as well as from fill to fill. Measurements during the 2012 LHC scrubbing run reveal a progressive reduction in the e-cloud activity and therefore a decrease in the secondary electron yield. The total beam power loss can be computed as a sum of the contributions from all bunches and compared with the heat load deposited in the cryogenic system.

Modification to the accelerator of the NBI-1B ion source for improving the injection efficiency.

Minimizing power loss of a neutral beam imposes modification of the accelerator of the ion source for further improvement of the beam optics. The beam optics can be improved by focusing beamlets. The injection efficiencies by the steering of ion beamlets are investigated numerically to find the optimum modification of the accelerator design of the NBI-1B ion source. The beam power loss was reduced by aperture displacement of three edge beamlets arrays considering power loadings on the beamline components. Successful testing and operation of the ion source at 60 keV/84% of injection efficiency led to the possibility of enhancing the system capability to a 2.4 MW power level at 100 keV/1.9 μP.

The effects of resonant magnetic perturbations on fast ion confinement in the Mega Amp Spherical Tokamak

The effects of resonant magnetic perturbations (RMPs) on the confinement of energetic (neutral beam) ions in the Mega Amp Spherical Tokamak (MAST) are assessed experimentally using measurements of neutrons, fusion protons and fast ion Dα (FIDA) light emission. In single null-diverted (SND) MAST pulses with relatively low plasma current (400 kA), the total neutron emission dropped by approximately a factor of two when RMPs with toroidal mode number n = 3 were applied. The measured neutron rate during RMPs was much lower than that calculated using the TRANSP plasma simulation code, even when non-classical (but axisymmetric) ad hoc fast ion transport was taken into account in the latter. Sharp drops in spatially-resolved neutron rates, fusion proton rates and FIDA emission were also observed. First principles-based simulations of RMP-induced fast ion transport in MAST, using the F3D-OFMC code, show similar losses for two alternative representations of the MAST first wall, with and without full orbit effects taken into account; for n = 6 RMPs in a 600 kA plasma, the additional loss of beam power due to the RMPs was found in the simulations to be approximately 11%.

Research on Near Space Optical Communication Transmitting and Receiving Technology

In near space optical communication, the laser beam energy affects communication link distance directly, also laser beam quality affects the laser energy density, modulation efficiency, bit error rate (BER) of communication and other parameters. In this paper we have presented an experiment system of space optical communication, of which the transmitting power is 1w, modulation rate is 500 Mbps and link distance is 8 to 10 kilometers. Then the effects of optical fiber collimator, electro-optic modulator, optical antenna and other units on beam power loss, beam diameter, divergence angle and other parameters are analyzed. Last we put forward the way of increasing the laser transmitting distance and the optimization measure of system key unit.

Beam shaping characteristics of an unstable-waveguide hybrid resonator.

The unstable-waveguide hybrid resonator emits a rectangular, simple astigmatic beam with a large number of high-spatial-frequency oscillations in the unstable direction. To equalize the beam quality, in this paper, a beam shaping system with a spatial filter for the hybrid resonator was investigated by numerical simulation and experimental method. The high-frequency components and fundamental mode of the output beam of the hybrid resonator in the unstable direction are separated by a focus lens. The high-frequency components of the beam are eliminated by the following spatial filter. A nearly Gaussian-shaped beam with approximately equal beam propagation factor M² in the two orthogonal directions was obtained. The effects of the width of the spatial filter on the beam quality, power loss, and intensity distribution of the shaped beam were investigated. The M² factor in the unstable direction is changed from 1.6 to 1.1 by optimum design. The power loss is only 9.5%. The simulation results are in good agreement with the experimental results.

Predictive Calculation of Neutral Beam Heating Plasmas in EAST Tokamak by NUBEAM Code for Certain Parameter Ranges

A predictive calculation is carried out for neutral beam heating of fusion plasmas in EAST by using NUBEAM code under certain plasma conditions. Results calculated are analyzed for different plasma parameters. Relations between major plasma parameters, such as density and temperature, are obtained and key physical processes in the neutral beam heating, including beam power deposition, trapped fraction, heating efficiency, and power loss, are simulated. Other physical processes, such as current-drive, toroidal rotation and neutron emission, are also discussed.

On trapped modes in the LHC recombination chambers: numerical and experimental results

The recombination chamber in Large Hadron Collider allows the separated proton beams to merge into a common vacuum chamber surrounding the interaction points. It has been subject of thorough studies concerning its interaction with the circulating beam. In this paper, we present the numerical and experimental results of our investigation on an approximated geometry. We show that in the smooth transitions between pipes of different diameters a trapped mode may exist, both in the real and in the approximated geometry. In the real structure, the mode is weak and not harmful both for the beam stability and power loss.

DAΦNE accumulator ring coupling impedance measurements

We discuss the results of the bunch lengthening and synchronous phase shift measurements performed during the commissioning of the DAΦNE accumulator ring and aimed to estimate the machine longitudinal coupling impedance. The dependence of the bunch length on the average current measured experimentally is in a good agreement with that predicted numerically. The low frequency machine impedance is estimated to be 3.55 Ω. It was also found that the parasitic beam power losses and the bunch shape distortion depend strongly on the actual RF cavity Higher Order Mode (HOM) positions with respect to the beam power spectrum lines. In particular, we observed that the effect of the HOMs can be minimized by raising the cavity temperature to 37°C.

Propagation characteristics of coherent array beams from carbon dioxide waveguide lasers

The characteristics of coherent array beams generated by waveguide carbon dioxide laser structures have been investigated, with particular emphasis on their propagation and transformation properties. Methods of array beam generation are presented, and measurements of array beam quality are given through the use of the M/sup 2/ parameter. Efficient transformation of an array beam from the antisymmetric to symmetric pattern is achieved through the use of a binary phase plate, and spatial filtering is shown to improve the beam quality at the expense of only a moderate loss of total beam power. Coherence effects in the near-field propagation of array beams are also explored.

Application of the Moyer method to transverse shielding of a linear bremsstrahlung source.

The Moyer method is applied to the design of transverse shielding for an electron linear accelerator, assuming uniform beam power loss along the accelerator structure. The limitations of the method with respect to primary beam energy are discussed. Only the component of the radiation field due to bremsstrahlung is considered in this paper. Parameters for this application are given and sample calculations are shown. For a beam power loss uniformly distributed with distance along a straight line of 0.5 W m-1, it is predicted that 1.2 m of concrete are needed to reduce the dose equivalent rate to 50 muSv h-1 (1.39 x 10(-8) Sv s-1), at a transverse distance of 3.5 m from the source.