IPAC2014 - List of Authors (Danisi, A.)

Paper	Title	Page
TUPRI054	FEM Analysis of Beam-coupling Impedance and RF Contacts Criticality on the LHC UA9 Piezo Goniometer	1692
	A. Danisi, R. Losito, A. Masi, A. Passarelli, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	The UA9 piezo-goniometer has been designed to guarantee micro-radians-accuracy angular positioning of a silicon crystal for a crystal collimation experiment in the LHC, and to minimize the impact on the LHC beam-coupling impedance. This paper presents a Finite Element Method (FEM) study of the device, in both parking and operational positions, to evaluate its impact on the LHC impedance budget. The study has been a progressive simulation work, started from the simplification of the original detailed design, and aimed at highlighting the effect of single details (e.g. objects in confining chambers) on the longitudinal and transverse components of beam-coupling impedance. In addition, the shielding contribution of the RF gaskets has been carefully evaluated, with the objective to assess the consequences for operation in case of their failure. Sensitivity analyses to simulation parameters are also performed, in order to test the FEM model robustness. A final word is drawn on the overall device impedance criticality.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI054
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TUPRI055	Theoretical Analysis of Metamaterial Insertions for Resistive-wall Beam-coupling Impedance Reduction	1695
	A. Danisi, R. Losito, A. Masi, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	Resistive-wall impedance usually constitutes a significant percentage of the total beam-coupling impedance budget of many accelerator structures (e.g. for LHC, it can be more than 50%). Reduction techniques for resistive-wall components entail high electrical-conductivity coatings. This paper proposes the use of metamaterials, having negative values of magnetic permeability or dielectric permittivity (or both), for sensibly reducing or theoretically nearly cancelling the resistive-wall component of beam-coupling impedance. The proposed approach is developed by means of an equivalent transmission-line model, whose results show the potential reduction of both longitudinal and transverse impedance when using metamaterial insertions. The effects on the real and imaginary part have been singled out. The effectiveness of such materials is discussed both for negative-permittivity and for negative-permeability cases, which actually show different impacts and can be then target of proper engineering. This first-stage study opens the possibility of considering metamaterials for impedance mitigation or for setting up proper experimental setups.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI055
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

FEM Analysis of Beam-coupling Impedance and RF Contacts Criticality on the LHC UA9 Piezo Goniometer

1692

A. Danisi, R. Losito, A. Masi, A. Passarelli, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

The UA9 piezo-goniometer has been designed to guarantee micro-radians-accuracy angular positioning of a silicon crystal for a crystal collimation experiment in the LHC, and to minimize the impact on the LHC beam-coupling impedance. This paper presents a Finite Element Method (FEM) study of the device, in both parking and operational positions, to evaluate its impact on the LHC impedance budget. The study has been a progressive simulation work, started from the simplification of the original detailed design, and aimed at highlighting the effect of single details (e.g. objects in confining chambers) on the longitudinal and transverse components of beam-coupling impedance. In addition, the shielding contribution of the RF gaskets has been carefully evaluated, with the objective to assess the consequences for operation in case of their failure. Sensitivity analyses to simulation parameters are also performed, in order to test the FEM model robustness. A final word is drawn on the overall device impedance criticality.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI054

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPRI055

Theoretical Analysis of Metamaterial Insertions for Resistive-wall Beam-coupling Impedance Reduction

1695

A. Danisi, R. Losito, A. Masi, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

Resistive-wall impedance usually constitutes a significant percentage of the total beam-coupling impedance budget of many accelerator structures (e.g. for LHC, it can be more than 50%). Reduction techniques for resistive-wall components entail high electrical-conductivity coatings. This paper proposes the use of metamaterials, having negative values of magnetic permeability or dielectric permittivity (or both), for sensibly reducing or theoretically nearly cancelling the resistive-wall component of beam-coupling impedance. The proposed approach is developed by means of an equivalent transmission-line model, whose results show the potential reduction of both longitudinal and transverse impedance when using metamaterial insertions. The effects on the real and imaginary part have been singled out. The effectiveness of such materials is discussed both for negative-permittivity and for negative-permeability cases, which actually show different impacts and can be then target of proper engineering. This first-stage study opens the possibility of considering metamaterials for impedance mitigation or for setting up proper experimental setups.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI055

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)