About
The optimisation of device coupling impedance is a key aspect in the design of accelerator components, directly impacting beam stability, high intensity limitations as well as the overall machine performance. This lecture presents a comprehensive approach to impedance characterisation and optimisation by means of numerical simulations and bench measurement techniques.
On the experimental side, the coaxial wire method is discussed as a versatile tool for impedance measurements of various device under test configurations, including resistive beam pipes, collimators, beam pipe cross-section transitions, and magnetic kickers. The coaxial wire method allows to excite in the device under test a field similar to the one generated by an ultra-relativistic point charge. It is a well-known technique and we discuss the basics as well as some recent relevant advances. In addition, resonant and non-resonant bead-pull techniques are presented for the characterisation of accelerating and deflecting RF structures.
From the numerical perspective, the direct simulation of bunch-induced wake potentials is introduced as a powerful method to derive wake functions and coupling impedance. The connection between the electromagnetic properties of a device and its modal structure (i.e. the field patterns supported by the geometry) is emphasised, highlighting their role in determining the impedance spectrum.
Particular attention is devoted to the estimation of measurement artefacts through dedicated simulations of the bench setup, enabling a consistent interpretation of experimental data. Finally, the potential of emerging multi-physics simulation tools is discussed, especially in view of increasingly complex devices where electromagnetic, thermal, and mechanical effects are strongly coupled.
The lecture aims to provide a coherent framework linking measurements, simulations, and physical interpretation for the effective optimisation of accelerator components.
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The talk
Credits and licence
- Institution
- CERN
- Department
- CAS - CERN Accelerator School
- Speaker
- Andrea Mostacci
- Year
- 2025
- Level
- Graduate
- Language
- English
- Subjects
- Physics
- Source
- CERN
- Licence
- CERN, as CERN states it. CERN's terms
- Attribution
- © CERN. CERN provides its audiovisual media free of charge for educational and informational use, credited to CERN; this lecture is shown in CERN's own player.
- Who can watch
- CERN gives no rating. Invisible Network shows it to Tweens profiles and older, judged from what the source says about it. How courses are placed