In this post, we present a CASE of technological success from CNPEM (National Center for Research in Energy and Materials) on the Sirius project, an advanced 4th generation particle accelerator located in Brazil. The author, Vitor Pereira Soares, is a member of the Magnets group at CNPEM, and describes the magnetic modeling used in the design of a superend with permanent magnet technology, using Siemens' Simcenter MAGNET software. The superbend plays a crucial role in the Sirius accelerator, allowing electron guidance and synchronous light emission. The use of this innovative technology demonstrates CNPEM's commitment to adopting and developing cutting-edge technologies. Below you will find all the details of this project and how Simcenter MAGNET contributed to its success.
Magnetic design for superbend magnets
Using simcenter MAGNET to optimize magnetic flux and critical energy in Brazilian particle accelerator
CNPEM's Project Sirius is a 4th generation particle accelerator, featuring one of the most advanced synchronous light sources globally. The Sirius superbend plays a crucial role in guiding electrons within the accelerator and enabling light emission. To design the superbend, CNPEM has taken an innovative approach, utilizing permanent magnet technology and optimizing it using Siemens' Simcenter MAGNET software. The result is a magnetic dipole capable of generating stronger magnetic fields, showcasing CNPEM's commitment to adopting and developing cutting-edge technology.
Author: Vitor Pereira Soares
Title: Technology Development Analyst, CNPEM
Introduction
Project Sirius is a milestone on Brazilian scientific research, opening new perspectives for the research in areas such as materials science, nanotechnology, physics, and many others.
Brazilian Center for Research in Energy and Materials (CNPEM)
In the late 1980s, Brazilian researchers built the first synchrotron light source in the southern hemisphere at the Brazilian Synchrotron Light Laboratory (LNLS). This particle accelerator aimed to advance critical technological fields in Brazil. After decades of accumulated knowledge, Project Sirius was developed as an incredibly sophisticated successor to the original accelerator, with worldwide competitiveness. Sirius is expected to facilitate hundreds of academic and industrial research projects annually, involving thousands of researchers, and contribute to solving significant scientific and technological challenges such as developing new drugs and treatments for diseases, creating new fertilizers, cultivating more resilient and adaptable plant species, and innovating technologies for agriculture, renewable energy sources, and many other potential applications with significant economic and social impacts.
To construct this fourth-generation particle accelerator, Simcenter MAGNET was employed in the design of the accelerator's magnets and ondulators.
Project Sirius
Sirius is one of the biggest and most powerful machines of its kind in the world. It has a 3 billion electron-volt energy beam, and its set of magnets, such as the superbend and the delta ondulator, developed with the Simcenter MAGNET software, allows it to provide a hard X-rays in a critical energy of 19keV, allowing more reliable aplication and opening new experimentation horizons.
How Sirius works
The electron beam is generated by heating of a metallic alloy, exciting the material’s electrons, which are sent to an acceleration structure and to a storage ring. The electrons travel in vacuum tubes at near light speed, and their trajectories are guided by magnetic fields, provided by multipole magnets along the way, such as the superbend dipole; the magnetic net of Sirius is composed of more than a thousand magnets.
Sirius’ magnetic net and its magnets composition: dipole, quadrupoles and sextupoles; in the bottom right is the insertion device
Synchrotron light
Sirius is a machine that accelerate electrons to produce the so called “synchrotron light”, used to study the atomic structures of matter. Synchrotron light is a kind of electromagnetic radiation, composed by frequencies that range from infrared to X-rays. The insertion devices, magnetic structures composed of several alternating dipole fields, such as the Delta Undulators (also using permanent magnetic technology) under development, allows for a million times brighter light than that of its predecessor accelerator (UVX), and expands its reach to the hard X-rays that allow it to penetrate even thicker materials.
Benefits of synchrotron light
Allows the study of atomic and molecular structures;
The synchrotron light’s broad spectrum allows for a wide range of analysis;
The high brightness makes for very quick results and material investigation;
Allows the project of new materials with specific properties.
The Magnetic superbend
A new model for Sirius dipoles takes the form of a superbend: a room temperature permanent magnet dipole, able to provide hard X-ray with a critical energy of 19 keV. Siemens software MAGNET was used to design and study the behavior of the magnetic flux in the dipoles.
This is the first dipole of this kind to use permanent magnets. The experience with permanent magnets dates back to 2005, with the project of an elliptically polarizing undulator to produce radiation. Through the years the knowledge has been matured and a high field dipole was proposed with the technology, a 2T permanent magnet dipole able to achieve a critical of 12 keV on light production. After some project reviews, the superbend designed with MAGNET expanded that capability to a 3.18 T maximum magnetic field and 19keV synchrotron light production.
Dipole main parameters | |
|---|---|
Number of Dipoles | 20 |
Magnetic Material | NdFeB |
Remanent Field (T) | 1.36 |
Intrinsic Coercive Force (Hcj) (kA/m) | >1590 |
High Field Pole Material | Iron-Cobalt |
Low Field Pole and Core Material | 1006 Carbon Steel |
Maximum Field (T) | 3.18 |
Critical Photon Energy (keV) | 19 |
Angular Deflection (°) | 4.3 |
Integrated Field (T·m) | -0.7504 |
Integrated Gradient (T) | 62.511 |
Length (mm) | 913 |
High Field Sector Mean Gap (mm) | 11 |
Low Field Sector Mean Gap (mm) | 31 |
The higher “brightness” allows the study of denser materials. The superbend project upgrade, besides increasing the light critical energy, increases by a factor of 40 the photon flux at high energies; the enhancement makes the generated light able to penetrate deeper and with a resolution higher than the former dipoles.
The C shape eases the access for measurements and maintenance, and the return flux blocks on the side of the magnet can be moved to change the air gap between them. This control gap can be adjusted even after the installation of the magnets in the lattice and will be used in case of demagnetization of the permanent magnet blocks.
Magnetic design of Sirius superbend
A special NdFeB magnet grade with higher coercivity, coated with NICUNI + Epoxy, with mechanical tolerance of ±0.05 mm for the block’s dimensions and magnetization tolerances of 1° in direction and 0.1% in amplitude, is used in the magnet to allow high precision assembly and integrated field repeatability for all magnets.
Magnetic design
Several designs were evaluated for the central dipole of the Sirius lattice. Due to the interaction between the magnets, it was decided to use a shared core for three dipoles, forming a single dipole referred to as BC.
The BC high field sector is formed by an Iron-Cobalt pole surrounded by NdFeB permanent magnet blocks. Due to the saturation of the pole, it is possible to obtain values of magnetic flux density larger than the remanent magnetization of the blocks. The IronCobalt was chosen for presenting higher saturation magnetization than the carbon steel. In addition, the union of the three dipoles in a single magnet saved space and allowed the placement of permanent magnet blocks in the space between the high and low field sectors to help increasing the flux in the IronCobalt pole. These changes caused the maximum magnetic flux density of the high field sector to increase from 2 T to 3.18 T, which increased the critical energy of the photons from 12 keV to 19 keV.
The MAGNET’s addon for design optimization make it possible to use advanced algorithms that can find optimal values for different design variables within the constraints specified. The resource was used to model the permanent magnets’ geometry not only in the superbend’s BC, but also in the other magnets in the system, such as regular dipoles, quadrupoles and the sextupoles.
Simcenter MAGNET Suite
MAGNET is a powerful electromagnetic field simulation tool for accurately predicting the performance of any component with permanent magnets or coils. Its advanced material modeling takes into account nonlinearities, temperature dependencies, demagnetization of permanent magnets, hysteresis loss, and anisotropic effects. This feature enables the analysis of various effects, such as the demagnetization of permanent magnets, verifying their service life, analyzing frequency-dependent losses in thin parts while reducing solution time, and accounting for all losses for an accurate energy balance. Additionally, MAGNET offers a userfriendly and intuitive interface, allowing users to conduct detailed analysis, optimize their designs, and obtain precise results efficiently
Flux density analysis in simcenter MAGNET
Magnetic simulations were performed using Simcenter MAGNET software.
The simulation investigates the longitudinal profile of the magnetic flux density of the dipole. With the longitudinal gradient obtained with this new version it was possible to reduce the beam emittance by approximately 10%. The table below summarizes the simulation results for the variation of the integrated dipole and quadrupole components of the magnetic field with the shift of the low field and floating poles. As seen, the transverse displacement of the low field poles can be used to adjust the magnet integrated field. Although this displacement also affects the quadrupolar gradient, this component can be further corrected with the rotation of the floating poles.
With the closure of the control gap, whose nominal value is of 3.2 mm, it is possible to obtain an increase of .1% in both the integrated dipole and quadrupole field components.
Densidade de fluxo magnético vertical simulada na posição transversal central da superbend.
Conclusion
The use of permanent magnets in the new accelerator trend of higher fields and small bore radius is a feasible option. Several permanent magnets design were proposed and prototyped and the superbend dipole is installed at the Sirius lattice. The magnetic and mechanical model were carefully planned assuming high challenges in assembly and measurements, as well as the possible effects of temperature variation. Radiation damage was also taken into account, and SmCo was an option, but NdFeB delivers higher field and is being used in insertion devices for a very long time. It was also important to consider some flexibilities in the model to compensate for possible variations in materials permeability, magnetization of the permanent magnets’ blocks, temperature and mechanical errors. The project was a success and Sirius is operating with the 3.2 T superbends for more than two years.
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The magnetic Superbend | Difference between the measured and simulated vertical magnetic flux |
About the author
Vitor Pereira Soares holds a bachelor's degree in physics from UNICAMP and is also a mechatronics technician. He joined CNPEM in 2011, having participated in several scientific instrumentation R&D projects. He is currently a member of the Magnets group, where he works on the development of insertion devices and magnetic characterization systems.
References:
J. Citadini, L. N. P. Vilela, R. Basilio and M. Potye, "Sirius-Details of the New 3.2 T Permanent Magnet Superbend," in IEEE Transactions on Applied Superconductivity, vol. 28, no. 3, pp. 1-4, April 2018, Art no. 4101104, doi: 10.1109/TASC.2017.2786270.
L. N. P. Vilela et al., "Status Report of Sirius Delta Undulator," in IEEE Transactions on Applied Superconductivity, vol. 32, no. 6, pp. 1-5, Sept. 2022, Art no. 4101305, doi: 10.1109/TASC.2022.3160941.
Download this case in PDF (English)
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