OPERA 3D Code Research Articles

Superconducting Magnet System Concept With Mechanical Energy Transfer in the Magnetic Field

There is an interest in designing superconducting magnet systems working in a persistent current mode. These systems continuously generate magnetic fields with disconnected power sources that work like permanent magnet devices. This paper proposes a magnet-system concept based on direct mechanical energy transfer in the magnetic field. Short circuited superconducting coils do not have current leads and power sources. To pump the mechanical energy in the superconducting coil, a magnetizer is used that is magnetically coupled with the coil. The mechanical removing of the magnetizer from the magnet induces a persistent current in the superconducting coil and generates the magnetic field. The iron-dominated magnet system concept was investigated using OPERA3d code, which confirmed the validity of the proposed approach.

Magnetic cross-talk simulation for Iranian Light Source Facility storage ring

Magnetic cross-talk due to the small free space between the magnets of a machine may result in significant distortions of the magnetic field integration and performance distortion of the machine. This paper presents the preparation done at the Iranian Light Source Facility (ILSF) on integrated magnetic components of three storage ring (SR) magnets with minimum space between the yokes, modeled separately in Opera-3D code and accumulatively as in the lattice design. The results show that the integrated quadrupole component of the BE2 dipole magnet remains nearly the same, while the integrated dipole and sextupole components are reduced by 0.13% and 4.69%, respectively. By the same token, the integrated quadrupole component of the Q11 in the lattice is decreased by 0.07%, and the integrated sextupole component of the S4 sextupole is reduced by 8.14%. The probable deviation on the higher-order integrated multipoles together with harmonic fields along the beam trajectory are discussed, and some studies are introduced to cut down any deficient effects.

H[formula omitted] extraction systems for CERN’s Linac4 H[formula omitted] ion source

Linac4 is a 160MeV linear H− accelerator at CERN. It is an essential part of the beam luminosity upgrade of the Large Hadron Collider (LHC) and will be the primary injector into the chain of circular accelerators. It aims at increasing the beam brightness by a factor of 2, when compared to the currently used 50MeV linear proton accelerator, Linac2.Linac4’s ion source is a cesiated RF-plasma H− ion source. Several beam extraction systems were designed for H− beams of 45keV energy, 50 mA intensity and an electron to H− ratio smaller than 5. The goal was to extract a beam with an rms-emittance of 0.25πmmmrad.One of the main challenges in designing an H− extraction system is dumping of the co-extracted electrons. Separating the electrons from the negative ions as early as possible reduces space-charge induced emittance-growth. However, a strong magnetic field close to the extraction might cause unnecessary strong deflection in a region of low beam energy. For this purpose a novel magnetic configuration was designed using a magnetic shield between the magnetic fields of the source and the electron dump, which conserves the filter field strength to keep the electron to H− ratio low and effectively dumps the co-extracted electrons. Magnetic configuration and beam trajectories were calculated using the TOSCA Opera 3D code and IBSimu, respectively. Three extraction systems will be discussed in terms of electron dumping efficiency, emittance and transport through the extraction system and LEBT to the RFQ and compared to the simulations.An improved emittance conservation through the extraction system and LEBT is predicted and further design improvements are proposed. Measurements show that the novel electron dump successfully traps the co-extracted electrons.

Design of a multi beam electron gun for 352.2 MHz, 100 kW (CW) power klystron

Conventional klystrons using single beam of electrons have several limitations for increasing of beam voltage or current which can be overcome using multiple electron beams. The paper presents the design of a single beam electron gun for a practical 100 kW CW conventional klystron and then translation of the design into a five-beam gun for reducing operating voltage and overall improvement in tube performance. The design parameters of multi beam electron gun have been derived from existing single beam parameters using some scaling laws, and are further optimized through CST Particle Studio. The simulation results of CST have been cross-validated using Opera-3D code. The electron gun is currently under development.

Design of Superconducting Magnets for a Compact Carbon Gantry

For widespread use of rotating gantries for carbon radiotherapy, we designed a new compact gantry. This new gantry consists of three combined-function superconducting magnets having a bending angle of 90°. The dipole field of the superconducting magnets is set to be B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> = 5.02 T, corresponding to a bending radius of 1.32 m for transporting carbon ions having kinetic energy of 430 MeV/u. The superconducting magnet also has three independent superconducting quadrupole coils, which are to be wound inside the dipole coil for beam focusing. The dipole and quadrupole coils are electrically isolated in the magnet and connected to independent power supplies so that each field component can be independently excited. Having used the combined-function superconducting magnets, the size of the rotating gantry would become very compact; the length and radius are 5.1 and 4.0 m, respectively. The magnetic field distributions of the superconducting magnets were calculated with a 3-D electromagnetic field solver, Opera-3d code. With calculated fields, the superconducting coils were designed to obtain uniform field distributions. In this paper, the design of this compact rotating gantry and the superconducting magnets is presented.

The influence of grid positioning on the beam optics in the neutral beam injectors for ITER

Neutral beam injectors are routinely used to increase the ion temperature in magnetically confined plasmas. Typically, the beam is produced by neutralizing a bundle of hundreds of ion beamlets, energized in a multi-grid multi-stage accelerator. Precise aiming of each beamlet is required in order to focus the full beam to the plasma, avoiding any interception with beamline surfaces and with the beam duct. This paper describes the effects of grid in-plane and out-of-plane displacements (mispositioning, thermal expansion, grid tilting, etc…) in the case of the MITICA electrostatic accelerator, which is the full scale prototype of the ITER heating neutral beam injector. Various simulations have been carried out with the OPERA 3D code, by self-consistently simulating the beam charged particles travelling in an externally applied electric and magnetic field. The accelerator grids act like a series of electrostatic lenses, and produce a net deflection of the particles when one or more grids are offset. The numerical simulations were used to evaluate the “steering constant” of each grid and also showed that the linear superposition of effects was applicable, multiple causes of mispositioning are combined and used to quantify the overall effect in terms of beam misalignment

A comparative study of PPM and solenoid focusing in multibeam electron gun

This paper represents the comparison of periodic permanent magnet (PPM) and solenoid focusing for dual anode multi-beam electron gun using OPERA3D code. The electron gun has been operated at 6 kV having 75 mA beam current with 0.45 mm beam waist radius. The design has an additional feature of cathode protection from ion bombardment with the application of extra ion barrier anode.

Design and Simulation of Electron Gun for a Multibeam Klystron

This paper represents the design of multi-beam (sixty-beam) electron gun and focusing system for high power, compact klystron. The beam voltage is 4 kV with a total beam current of 513 (8.55 × 60) mA which is equally divided among sixty-beam. Each beam has a perveance of 0.033 μP making a total gun perveance of 2.02 μP corresponding to a total beam power of more than 2 kW. The cathode radius is7 mm and individual emitter radius is 0.2 mm having current density 6.7 A/cm2. The design has been accomplished using OPERA 3D code. All beamlets have individual anode as well as BFE and a common focusing system. Potential difference between cathode and anode is 4 kV. A magnetic field of 1200 Gauss is applied along the beam axis. A major challenge for the development of multi-beam klystron is design and technology for the focusing of off-axis beamlets because off-axis beams are at various azimuths.

Laser generated Ge ions accelerated by additional electrostatic field for implantation technology

The paper presents research on the optimization of the laser ion implantation method with electrostatic acceleration/deflection including numerical simulations by the means of the Opera 3D code and experimental tests at the IPPLM, Warsaw. To introduce the ablation process an Nd:YAG laser system with repetition rate of 10Hz, pulse duration of 3.5ns and pulse energy of 0.5J has been applied. Ion time of flight diagnostics has been used in situ to characterize concentration and energy distribution in the obtained ion streams while the postmortem analysis of the implanted samples was conducted by the means of XRD, FTIR and Raman Spectroscopy. In the paper the predictions of the Opera 3D code are compared with the results of the ion diagnostics in the real experiment. To give the whole picture of the method, the postmortem results of the XRD, FTIR and Raman characterization techniques are discussed. Experimental results show that it is possible to achieve the development of a micrometer-sized crystalline Ge phase and/or an amorphous one only after a thermal annealing treatment.

Laser produced streams of Ge ions accelerated and optimized in the electric fields for implantation into SiO2 substrates

Ge crystals were prepared by means of laser-induced ion implantation technique. A Nd:YAG pulsed laser (repetition rate: 10 Hz; pulse duration: 3.5 ns; pulse energy: ∼0.5 J) was used both as an ion source and to carry out the ablation processes. The optimization of the laser-generated ion beam parameters in a broad energy and current density range has been obtained controlling the electrostatic field parameters. Numerical simulations of the focusing system, performed adopting an OPERA 3D code, and an investigation of the ion characteristics, using the ion time-of-flight method, have allowed to optimize the preparation parameters. The structural properties of the samples were investigated by means of x-ray photoelectron, micro-Raman spectroscopies, and scanning electron microscopy techniques. Experimental results show that, by appropriately varying the ion implantation parameters and by a post-preparation annealing treatment, it is possible to achieve the development of a micrometer-sized crystalline Ge phase and∕or an amorphous one.

Physics design of a 100 keV acceleration grid system for the diagnostic neutral beam for international tokamak experimental reactor

This paper describes the physics design of a 100 keV, 60 A H(-) accelerator for the diagnostic neutral beam (DNB) for international tokamak experimental reactor (ITER). The accelerator is a three grid system comprising of 1280 apertures, grouped in 16 groups with 80 apertures per beam group. Several computer codes have been used to optimize the design which follows the same philosophy as the ITER Design Description Document (DDD) 5.3 and the 1 MeV heating and current drive beam line [R. Hemsworth, H. Decamps, J. Graceffa, B. Schunke, M. Tanaka, M. Dremel, A. Tanga, H. P. L. De Esch, F. Geli, J. Milnes, T. Inoue, D. Marcuzzi, P. Sonato, and P. Zaccaria, Nucl. Fusion 49, 045006 (2009)]. The aperture shapes, intergrid distances, and the extractor voltage have been optimized to minimize the beamlet divergence. To suppress the acceleration of coextracted electrons, permanent magnets have been incorporated in the extraction grid, downstream of the cooling water channels. The electron power loads on the extractor and the grounded grids have been calculated assuming 1 coextracted electron per ion. The beamlet divergence is calculated to be 4 mrad. At present the design for the filter field of the RF based ion sources for ITER is not fixed, therefore a few configurations of the same have been considered. Their effect on the transmission of the electrons and beams through the accelerator has been studied. The OPERA-3D code has been used to estimate the aperture offset steering constant of the grounded grid and the extraction grid, the space charge interaction between the beamlets and the kerb design required to compensate for this interaction. All beamlets in the DNB must be focused to a single point in the duct, 20.665 m from the grounded grid, and the required geometrical aimings and aperture offsets have been calculated.

An Evaluation of the Helical Winding Method Applied to the Next European Dipole Project

The Next European Dipole (NED) Collaboration is working to develop the technology of high field, dipole magnets for a future luminosity upgrade of the LHC at CERN. The challenge is to design and build a short prototype, large aperture (88 mm), dipole magnet to operate at 15 T using conductors. While the baseline design uses a cosine- winding configuration, a key part of the NED program has been the evaluation of other winding configurations. This paper reports on an evaluation of the helical dipole winding method and its applicability to the high field, large aperture magnets required for NED. The paper describes the development of magnetic models using the OPERA3D code. These models have been used to assess the field homogeneity, peak field performance, forces and conductor efficiency of the helical winding. The parameters developed from this analysis are compared with cosine- models. A conceptual winding geometry is presented and evaluated.

Status report on the development of a tubular electron beam ion source

The theoretical estimations and numerical simulations of tubular electron beams in both beam and reflex mode of source operation as well as the off-axis ion extraction from a tubular electron beam ion source (TEBIS) are presented. Numerical simulations have been done with the use of the IGUN and OPERA-3D codes. Numerical simulations with IGUN code show that the effective electron current can reach more than 100 A with a beam current density of about 300–400 A/cm2 and the electron energy in the region of several KeV with a corresponding increase of the ion output. Off-axis ion extraction from the TEBIS, being the nonaxially symmetric problem, was simulated with OPERA-3D (SCALA) code. The conceptual design and main parameters of new tubular sources which are under consideration at JINR, MSL, and BNL are based on these simulations.

Latest results from the Cadarache 1 MV SINGAP experiment

The SINGle Aperture—SINgle GAP (SINGAP) acceleration concept has been developed as a simplified alternative to the Multi-Aperture, Multi-Grid (MAMuG) acceleration of the ITER Neutral Beam reference design. The objective of the present experiments is to demonstrate reliable multi-second acceleration of a D − beam to 1 MeV (∼100 mA, 200 A/m 2), relevant to the ITER neutral beam injection (NBI) requirements. During the previous studies it has been demonstrated that the SINGAP concept works and good quality 860 keV H − beams (43 mA, 1 s) and 630 keV D − beams (106 mA, 1 s) have been produced. In the present R&D programme another attempt has been made to reach the full beam energy and increase the extracted beam current density with a refurbished 1 MV epoxy insulator/bushing. Refurbishment had become necessary after the top two of the nine epoxy rings making up the insulator had been perforated and carbonised due to high voltage discharges. The best results achieved during the present campaign are 914 keV D − beams (58 mA, 1 s) with a D − current density of 30 A/m 2 and 600 keV D − beams (76 mA, 1 s) with a D − current density of 70 A/m 2. These results are world records. The beam optics is largely as expected from the modelling with the Vector Fields OPERA 3D code.