Beam Loss Research Articles

Radiation Pattern Synthesis and Mutual Coupling Compensation in Spherical Conformal Array Antennas

This paper presents a novel technique based on Hybrid Spatial Distance Reduction Algorithm (HSDRA), to compensate the effects of deformity and mutual coupling occurred due to surface change in conformal arrays. This antenna surface deformation shifts the position of null points and loss of the main beam resulting in reduced antenna gain along with substantial undesirable effects on the antenna performance. The proposed algorithm, which cumulatively incorporates the Linearly Constraint Least Square Optimization (LCLSO) and Quadratically Constraint Least Square Optimization (QCLSO) techniques, is formulated to minimize/reduce the absolute distance between the actual (simulated/measured) radiation pattern and the desired radiation pattern while keeping the direction of main beam and nulls position under control. In particular, a 4x4 conformal microstrip phased array from planar surface is deformed to prescribe spherical-shape surface with various radii of curvature, is validated. For the enhancement of Gain of the conformal array antenna, Gain Maximization Algorithm is also proposed, the simulated results of which is compared to the traditional Phase compensation technique and unconstraint least squares optimization. The analytical results for both planar and spherical deformed configurations are first evaluated in MATLAB and then validated through Computer Simulation Technology (CST).

Ridge resonators: impact of excitation beam and resonator losses.

Photonic resonators based on bound states in the continuum are attractive for sensing and telecommunication applications, as they have the potential to achieve ultra-high Q-factor resonators in a compact footprint. Recently, ridge resonators - leaky mode resonators based on a bound state in the continuum - have been demonstrated on a scalable photonic integrated circuit platform. However, high Q-factor ridge resonators have thus far not been achieved. In this contribution, we investigate the influence of excitation beam width and optical losses on the spectral response of ridge resonators. We show that for practical applications, the space required of the excitation beam is the limiting factor on the highest achievable Q-factor.

Development and Testing of a Cherenkov Beam Loss Monitor in CLEAR Facility

Development and Testing of a Cherenkov Beam Loss Monitor in CLEAR Facility

Fast ion bunch compression by barrier pulse control

We report a novel scheme for fast ion bunch compression by barrier pulse control in an induction synchrotron in which an effective acceleration voltage pulse with a pseudo-linear slope is generated by temporal handling of rectangular induction acceleration pulses. With beam handling, a head-to-tail momentum gradient is yielded to the beam in a desired manner and the beam is gradually compressed over 30 turns. In the proof-of-principle experiment, which used a 75 μA He1+ beam at 50 keV per nucleon, the root mean square bunch length was reduced to 0.44 μs by a factor of 3.5 in 30 turns with no appreciable beam loss due to the beam compression scheme. This scheme is useful for various beam applications including ion beam heating.

Optical Beam Loss Monitor Based on Fibres for Beam Loss Monitoring and RF Breakdown Detection

Optical Beam Loss Monitor Based on Fibres for Beam Loss Monitoring and RF Breakdown Detection

Beam Loss Study for the Implementation of Dechirper at the European XFEL

Beam Loss Study for the Implementation of Dechirper at the European XFEL

Beam Loss Simulations During Beam Dumping in Heps

Beam Loss Simulations During Beam Dumping in Heps

Heat load in IR from synchrotron radiation and beam loss for CEPC double ring scheme

With the discovery of the Higgs boson at around 125 GeV, a circular Higgs factory design with high luminosity ([Formula: see text]) is becoming more popular in the accelerator world. The CEPC project in China is one of them. Machine Detector Interface (MDI) is the key research area in electron–positron colliders, especially in CEPC, since the synchrotron radiation (SR) photons can contribute to the heat load of the beam pipe and radiation dose may damage the components. And the heat load can cause the temperature rise in some part, and if the temperature rise is too high, the beryllium pipe in the interaction region will melt and the superconducting magnet may quench. Thus, the heat load distribution from synchrotron radiation and beam loss in the interaction region are analyzed carefully and results are given in this paper.

Stripping mechanisms and remediation for H− beams

Negative hydrogen ions are often used for injecting protons from linacs to storage rings via charge-exchange injection. In this process, the two electrons are stripped by a foil or laser to produce protons which can be merged with an existing beam without significantly affecting its dynamics, allowing high intensities of protons to be accumulated. However, this capability comes with the drawback that the outer electron of an H$^-$ ion has a low binding energy and can easily be stripped away prior to injection. This paper addresses the following stripping mechanisms: interactions with residual gas in the beam pipe, blackbody radiation from accelerator components, and electromagnetic fields from accelerator optics (Lorentz-force stripping) and particles within the bunch itself (intrabeam stripping); with a discussion on how to avoid excessive activation from stripped H$^0$ particles and protons. We also demonstrate that the proportion of stripped H$^0$ colliding with a nearby beam pipe or machine-element walls presents only roughly 10\% of those lost in stripping; the remaining stripped particles traverse to the end of a linac or local straight section, which may relax the limits for allowable stripping-based beam loss in H$^-$ accelerators.

Design and beam dynamics of CEPC damping ring system

A damping ring system which includes a small 1.1 GeV ring and two transport lines is introduced in CEPC linac in order to reduce the transverse emittance of positron beam at the end of linac and hence reduce the beam loss in the booster. This paper introduces the parameter choice and optics study of damping ring. The corresponding instability effect and IBS effect are also checked to make sure the design current and design emittance can be realized. Except for damping ring, two transport lines are needed to match the parameters between linac and damping ring. Both designs for energy compressor and bunch compressor including beam simulations are discussed in this paper.

Compensation scheme for non-linear beam defocusing inside planar undulator

The Delhi Light Source (DLS), is a compact THz facility based on the principle of pre-bunched FEL, which is at the commissioning stage at Inter University Accelerator Centre (IUAC), New Delhi. The facility will produce relativistic electron beam in the energy range 4 to 8 MeV to generate THz radiation in the range 0.18–3.0 THz. To study the effect of the undulator U48 on this low energy range of the electron beam, a 3D field map of U48 was generated with the help of measured magnetic field data. Beam tracking simulations were performed with the generated field map at the minimum gap of U48. Simulations showed that the quadrupole component of the transverse field roll-off, which is the dominant component within the width of the vacuum chamber can introduce a substantial growth of the beam size in the wiggling plane and result in severe beam loss while propagating through the vacuum chamber inside the undulator. To compensate the dynamic quadrupolar field, an extended quadrupole field correction coil was implemented in the simulation by superimposing its field on the magnetic field of U48. Such a correction scheme showed a remarkable improvement to contain the beam transverse growth.

Physical design of a compact 2 MeV deuteron radio-frequency quadrupole

This paper describes the physical design of a radio-frequency quadrupole (RFQ) accelerator for a compact accelerator-driven neutron source. The 325-MHz RFQ accelerates a 30-mA deuteron beam from 50 keV to 2 MeV, which is directly matched to the drift-tube linac (DTL) without a separate beam matching section. The objective of this design is to obtain a short RFQ with a tolerable transmission and power consumption. Using a modified four-section procedure, the inter-vane voltage is ramped with RFQ longitudinal position to obtain the required short length, and the focusing strength is varied to suppress beam loss. The RFQ has a length of 193.2 cm, with a peak power consumption of 186 kW, and a beam transmission of 94.1%.

Proton irradiation effects in Molybdenum-Carbide-Graphite composites

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) has prompted the investigation of novel materials for beam-intercepting devices, and in particular for the collimators responsible for protecting the machine from beam losses. The HL-LHC collimation system will inevitably experience increased levels of radiation damage and undergo changes in their crucial physio-mechanical properties. Graphite-matrix composite materials containing molybdenum carbide particles, along with small amounts of titanium carbide, were developed with the objective of enhanced in-beam performance and tested under proton irradiation. The physical degradation observed in early grades of molybdenum carbide compounds, even after modest proton fluences, has prompted the development of advanced compounds. In this work, we examine the effects of proton irradiation on the microstructural and thermophysical properties of new grades of Molybdenum-carbide-graphite compounds up to fluences of ~2 × 10 20 p/cm 2 . We employ a combination of precision dilatometry and high-energy X-ray diffraction to quantify the dimensional stability and crystallographic phase evolution both pre- and post-irradiation. Our results reveal that these new compounds exhibit superior resilience to radiation damage than their predecessors.

An overview of the shielding optimization studies for the TRIUMF-ARIEL facility

The Advanced Rare IsotopE Laboratory (ARIEL) facility, dedicated to Radioactive Ion Beam (RIB) production via the Isotope Separation On-Line (ISOL) technique, is currently under construction at TRIUMF. The facility is to host dual target stations that will operate simultaneously, including a 500 MeV proton beam from the main TRIUMF cyclotron and a 50 MeV electron beam from an Electron Linear Accelerator (e-linac). The proton target station will operate a symbiotic medical target in series with the ISOL target.The ARIEL facility features a compact shielding envelope and as a result its optimization relied extensively on simulations generated using the Monte Carlo particle transport and interaction code FLUKA. Dose rate maps were produced of prompt radiation associated with beam losses and expected normal operations. Maps of transient fields were also generated considering radiation sources requiring transport within the facility which include radioactive waste generated in the course of normal operations. Activation studies were also conducted to estimate the amount of residual radioactivity contained in shielding materials at the time of decommissioning. Simulation results are primarily used to inform the ongoing design and construction of ARIEL; at present, the entirety of the proposed facility shielding has been validated by FLUKA simulation data. The specification of shielding geometry and the selection of materials relied extensively on engineering support through verification of CAD models and material sampling to optimize solutions for design simplicity and economy. Normal operation and failure scenarios were both evaluated, with optimized shielding materials and thicknesses selected considering the nature of the radiation fields present and their impact on room occupancy. Finally, a decommissioning plan has been defined based on the anticipated ARIEL lifetime, the characterization of structural activation, and a general disposal strategy.While ARIEL is still under construction and significant progress has been made, the ongoing radiation modelling has enabled validation of the current shielding design for nominal operation. Moreover, the systematic studies performed were paramount in defining the optimal strategies to adopt from target storage to that for decommissioning of the facility.

Study on the anti-correlated painting injection scheme for the Rapid Cycling Synchrotron of the China Spallation Neutron Source

In the rapid cycling synchrotron of the China Spallation Neutron Source, the anti-correlated painting was adopted for the design scheme of the injection system. In the beam commissioning, with the optimization of the anti-correlated painting, the injection beam loss has been well controlled and the injection efficiency has exceeded 99%. Combined with other aspects of adjustments, the beam power on the target has reached 50 kW. In this paper, we have studied the injection optimization in the beam commissioning. Compared to the simulation results of the design scheme, the transverse beam distribution, transverse coupling effect and beam loss of the anti-correlated painting in the beam commissioning are somewhat different. Through the machine studies, we have carefully analyzed these differences and studied their reasons.

Time-dependent analysis of simply supported and continuous unbonded prestressed concrete beams

An equation to estimate the prestress loss in continuous unbonded prestressed concrete beams is proposed in this paper. The equation accounts for the creep and shrinkage of the concrete and the relaxation of the prestressing steel. In addition, a numerical model is developed based on the finite element method for the time-dependent analysis of these types of concrete beams. The approach also accounts for the presence of non-prestressed steel reinforcement and the friction between the tendons and their ducts. Furthermore, a well-justified integral-form equation is proposed to compute the strain at each section of the unbonded prestressing steel accounting for the friction between the tendons and their ducts. This equation is based on the equation for frictional loss accepted by different standards. The strain at each section of the unbonded prestressing is calculated from the strain in the concrete at the level of the prestressed tendon along the whole beam. Numerical and experimental results are compared to validate the proposed equation and the finite element approach and the good performance of both in modelling the behaviour of this type of prestressed concrete member over time is shown.

Characterization of the beam scraping system of the CERN Super Proton Synchrotron

The Super Proton Synchrotron at CERN is equipped with a scraping system for halo cleaning at beam transfer to the Large Hadron Collider. The system is composed of movable graphite blades mechanically swept through the beam to remove tails immediately before beam transfer. Due to the mechanical movement, beam particles are intercepted by a small volume of material with consequent concentration of energy deposition and high thermal loads. The blades were tested with beam to verify their resistance to the most extreme scraping conditions. Even though the beam was prematurely dumped by the beam loss monitoring system, the microstructural analysis of the blades following the test found signs of material sublimation. The test setup was reproduced in simulation to reconstruct the levels of energy deposition actually reached in the blades during the test; values are compatible with local material sublimation, in agreement with the microstructural analysis. Simulations were carried out by coupling the sixtrack tracking code, used for single particle beam dynamics in circular accelerators for high energy physics, to the fluka Monte Carlo code, for particle-matter interactions. The time evolution of the beam intensity measured during scraping and the distribution of losses around the ring were used for an extensive benchmark of the simulation tool against measurements taken during the test. This work presents the endurance test together with simulation results and the benchmark of the simulation tool. The quantitative agreement between simulations and measurements proves the quality of the analyses and the maturity of the simulation tool, which can be reliably used to predict the performance of cleaning systems in circular accelerators.

High-intensity beam profile measurement using a gas sheet monitor by beam induced fluorescence detection

A transverse beam profile monitor that visualizes a two-dimensional beam-induced fluorescent image was developed. The monitor employs a sheet-shaped gas flow formed by a technique of rarefied gas dynamics. A simplified analysis method was developed to reconstruct the beam intensity profile from the obtained image. The developed profile monitor and the analysis method were applied to measure the J-PARC 3 MeV ${\mathrm{H}}^{\ensuremath{-}}$ beam profile. The root mean square values of the profiles were consistent with the ones obtained by a wire-scanning-type beam profile monitor. The beam loss due to the gas sheet injection was measured as a beam-current reduction. The amount of the beam current decreased in proportion to the gas sheet flux and the reduction ranged from 0.004 to 2.5%. The assembled system was capable of reconstructing a beam profile from a single shot beam pulse ($1.7\ifmmode\times\else\texttimes\fi{}{10}^{13}$ protons in $50\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$).

Research of beam matching on RFQ for CADS proton linac

For a high-power Radio Frequency quadrupole (RFQ) accelerator, it is often necessary to design a large acceptance to decrease the beam loss inside the RFQ cavity. This could allow a mismatched beam to transmit to downstream cavities, which causes beam loss along the downstream linac. Finding the matching condition of beam and RFQ is of great significance. The matching point of RFQ can be confirmed by measuring the emittance at the upstream and downstream of RFQ, which takes a long time, so the transmission efficiency scanning method is supposed to find. This paper compares the relationship among emittance, transmission efficiency, and matching point on CADS[Formula: see text] RFQ. The results show that the weighted average point of high transmission efficiency could be regarded as the matching point of RFQ. This conclusion can be widely used in beam commissioning, and the Transmission Efficiency Scanning-matching (TESM) code has been developed on other RFQs.

Impact of betatron collimation losses in the High-Energy Large Hadron Collider

In response to recommendations in the 2013 update of the European Strategy for Particle Physics, a conceptual design effort for an energy upgrade of the Large Hadron Collider (LHC) at CERN, the so-called high-energy LHC (HE-LHC), was launched as part of the Future Circular Collider study. The HE-LHC machine, which is meant to use 16 T magnet technologies in the existing LHC tunnel, would provide proton collisions at a center-of-mass energy of 27 TeV ($\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}\mathrm{LHC}$) with a total stored energy of 1.34 GJ ($\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}\mathrm{LHC}$) per beam. By adapting the LHC collimation system, a first layout of the HE-LHC's betatron cleaning insertion was conceived, with the requirement to sustain---for at least 10 seconds---the impact of about 1.86 MW, corresponding to a beam lifetime of 12 minutes, without inducing any magnet quench nor any damage to other accelerator components. In this article, we evaluate the power deposition on the collimation insertion for proton beam operation in the HE-LHC machine at top energy, by means of particle tracking and interaction calculations. The beam loss effects on the warm elements as well as on the superconducting dispersion suppressor magnets are assessed through a three-step simulation approach. In particular, for the proposed future high-energy LHC, we demonstrate the necessity of adding local collimators in the dispersion suppressor, and we uncover the harmful consequences of a potential removal of the beam line ``dogleg'' in the collimation insertion.