Numerical calculation of beam Coupling Impedances in Synchrotron Accelerators
Beams of charged particles are of interest in various fields of research including particle and nuclear physics, material and medical science and many more. In synchrotron accelerators the accelerating section is passed multiple times. A closed loop trajectory is enforced, by increasing the frequency...
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| Format: | Others |
| Language: | en |
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2016
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| Online Access: | https://tuprints.ulb.tu-darmstadt.de/5367/1/2016-7-14_Dissertation_tuprints.pdf Hänichen, Lukas <http://tuprints.ulb.tu-darmstadt.de/view/person/H=E4nichen=3ALukas=3A=3A.html> (2016): Numerical calculation of beam Coupling Impedances in Synchrotron Accelerators.Darmstadt, Technische Universität Darmstadt, [Ph.D. Thesis] |
| Summary: | Beams of charged particles are of interest in various fields of research including particle and nuclear physics, material and medical science and many more. In synchrotron accelerators the accelerating section is passed multiple times. A closed loop trajectory is enforced, by increasing the frequency of the accelerating electric field and the magnitude of the dipolar magnetic guide field synchronously. A synchrotron therefore consists of a circular assembly of various beamline elements which serve the purposes of accelerating and guiding of the particle beam. For the flawless operation of such a machine it has to be assured that the particles perform a controlled motion along predefined trajectories. Amongst others, the fulfillment of the corresponding stability criteria is in close conjuction with the so-called beam coupling impedances which are
an important figure of merit for collective effects in synchrotron accelerators.
This work focuses on analytical and numerical methods for the calculation of beam coupling impedances. One of the primary objectives is to gain a better understanding of charged particle beam electrodynamics, the mathematical description in both time and frequency domain and establish the links between actual physics and numerical modeling. Analytical methods are usually restricted to symmetrical geometry and may solely serve for the approximate determination of the field distribution in real geometries or to validate certain numerical methods. Finally, more accurate prognosis is only possible with 3D numerical simulation models.
Numerical simulation techniques have been established in the second half of the last century accompanying the evolution of many particle accelerators. Classical time domain codes were the prevailing simulation tools where the actual process of the particle
motion sequence is reproduced. For the present case of a heavy ion synchrotron accelerator, particle velocities significantly lower than the speed of light occur and the commonly applied ultra-relativistic limit case may no longer be practicable.
Ferrite-loaded kicker magnets are commonly used to achieve abrupt changes of the beam direction of motion and contribute to the coupling impedance due to hysteresis properties of the ferrite material. These coupling impedance contributions must be determined to assess the feedback action on the traversing particles particles of the beam.
After introducing important mathematical relations and presentation of two calculation methods, a few reference examples are discussed, which can be treated bymeans of the classical electromagnetic field theory. After showing that the simulation results are in accordance with the corresponding analytical results, the focus is put on simulation models that represent actual components of the FAIR SIS100 synchrotron accelerator. |
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