IPAC2018 - List of Authors (Migliorati, M.)

Paper	Title	Page
MOPMK012	Electron Cloud Studies in FCC-ee	374
	E. Belli Sapienza University of Rome, Rome, Italy P. Costa Pinto, G. Rumolo, T.F. Sinkovits, M. Taborelli CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy
	Electron cloud effects are one of the most critical aspects for the LHC and the future circular colliders. In the frame of the electron-positron collider FCC-ee, an estimation of the electron cloud build up in the machine will be discussed in this paper. A preliminary evaluation of the heat load in the arc components and interaction region magnets will be presented, together with possible mitigation strategies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK012
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THPAF036	Longitudinal and Quadrupolar Coupling Impedance of an Elliptical Vacuum Chamber With Finite Conductivity in Terms of Mathieu Functions	3040
	M. Migliorati, L. Palumbo Sapienza University of Rome, Rome, Italy N. Biancacci CERN, Geneva, Switzerland M. Migliorati, L. Palumbo INFN-Roma1, Rome, Italy V.G. Vaccaro Naples University Federico II and INFN, Napoli, Italy
	Funding: Work supported by the CERN PS-LIU project The resistive wall impedance of an elliptical vacuum chamber in the classical regime with infinite thickness is known analytically for ultra-relativistic beams by means of the Yokoya form factors. Starting from the longitudinal electric field of a point charge moving at arbitrary speed in an elliptical vacuum chamber, which we express in terms of Mathieu functions, in this paper we take into account the finite conductivity of the beam pipe walls and evaluate the longitudinal and quadrupolar impedance for any beam velocity. We also obtain that the quadrupolar impedance of a circular pipe is different from zero, approaching zero only for ultra-relativistic particles. Even if some of the results, in particular in the ultra-relativistic limit, are already known and expressed in terms of form factors, this approach is the first step towards the calculation of the general problem of a multi-layer vacuum chamber with different conductivities and of elliptic cross section.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF036
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THPAK052	Single Bunch Instabilities in FCC-ee	3336
SUSPF076	use link to see paper's listing under its alternate paper code
	E. Belli Sapienza University of Rome, Rome, Italy G. Castorina, M. Migliorati INFN-Roma1, Rome, Italy G. Rumolo CERN, Geneva, Switzerland B. Spataro, M. Zobov INFN/LNF, Frascati (Roma), Italy
	FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK052
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TUPAF024	Impedance and Instability Studies in LEIR with Xenon	720
	N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral CERN, Geneva, Switzerland M. Migliorati Rome University La Sapienza, Roma, Italy
	In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF024
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THPAK091	Design of the New Proton Synchrotron Booster Absorber Scraper (PSBAS) in the Framework of the Large Hadron Collider Injection Upgrade (LIU) Project	3444
	L. Teofili, M. Migliorati Sapienza University of Rome, Rome, Italy J.A. Briz Monago, M. Calviani, N. Chritin, J.J. Esala, S.S. Gilardoni, I. Lamas Garcia, J. Maestre, T. Polzin, T.L. Rijoff CERN, Geneva, Switzerland T.L. Rijoff TU Darmstadt, Darmstadt, Germany
	The Large Hadron Collider (LHC) Injector Upgrade (LIU)Project at CERN calls for increasing beam intensity for the LHC accelerator chain. Some machine components will not survive the new beam characteristics and need to be rebuilt for the new challenging scenario. This is particularly true for beam intercepting devices (BIDs) such as dumps, collimators, and absorber/scrapers, which are directly exposed to beam impacts. In this context, this work summarizes conceptual design studies on the new Proton Synchrotron Booster (PSB) Absorber/Scraper (PSBAS), a device aimed at cleaning the beam halo at the very early stage of the PSB acceleration. This paper outlines the steps performed to fulfil the component design requirements. It discusses thermo-mechanical effects as a consequence of the beam-matter collisions, simulated with the FLUKA Monte Carlo code and ANSYS finite element software; and the impedance minimization study performed to prevent beam instabilities and to reduce RF-heating on the device.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK091
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THPAK092	Analysis on the Mechanical Effects Induced by Beam Impedance Heating on the HL-LHC Target Dump Injection Segmented (TDIS) Absorber	3448
	L. Teofili, M. Migliorati Sapienza University of Rome, Rome, Italy M. Calviani, D. Carbajo Perez, S.S. Gilardoni, F. Giordano, I. Lamas Garcia, G. Mazzacano, A. Perillo-Marcone CERN, Geneva, Switzerland
	The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In such a scenario, critical accelerator devices need to be redesigned and rebuilt. Impedance is among the design drivers, since its thermo-mechanical effects could lead to premature device failures. In this context, the current work reports the results of a multiphysics study to assess the electromagnetic and thermo-mechanical behaviour of the Target Dump Injection Segmented (TDIS). It first discusses the outcomes of the impedance analysis performed to characterise the resistive wall and the high order resonant modes (HOMs) trapped in the TDIS structures. Then, their RF-heating effects and the related temperature distribution are considered. Finally, mechanical stresses induced by thermal gradients are studied in order to give a final validation on the design quality.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK092
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THPAK093	A Multi-Physics Approach to Simulate the RF Heating 3D Power Map Induced by the Proton Beam in a Beam Intercepting Device	3452
SUSPF075	use link to see paper's listing under its alternate paper code
	L. Teofili, M. Migliorati Sapienza University of Rome, Rome, Italy D. Carbajo Perez, F. Giordano, I. Lamas Garcia, G. Mazzacano CERN, Geneva, Switzerland
	The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK093
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THPAL009	A TM01 Mode Launcher With Quadrupole Field Components Cancellation for High Brightness Applications	3631
	G. Castorina INFN-Roma1, Rome, Italy A.D. Cahill, J.B. Rosenzweig UCLA, Los Angeles, California, USA F. Cardelli, G. Franzini, A. Marcelli, B. Spataro INFN/LNF, Frascati (Roma), Italy L. Celona, S. Gammino, G. Torrisi INFN/LNS, Catania, Italy V.A. Dolgashev SLAC, Menlo Park, California, USA L. Ficcadenti Rome University La Sapienza, Roma, Italy M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy G. Sorbello University of Catania, Catania, Italy
	The R&D of high gradient radiofrequency (RF) devices is aimed to develop innovative accelerating structures based on new manufacturing techniques and materials in order to construct devices operating with the highest accelerating gradient. Recent studies have shown a large increase in the maximum sustained RF surface electric fields in copper structures operating at cryogenic temperatures. These novel approaches allow significant performance improvements of RF photoinjectors. Indeed the operation at high surface fields results in considerable increase of electron beam brilliance. This increased brilliance requires high field quality in the RF photoinjector and specifically in its power coupler. In this work we present a novel power coupler for the RF photoinjector. The coupler is a compact X-band TM01 mode launcher with a fourfold symmetry which minimized both the dipole and the quadrupole RF components.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL009
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THPML027	Longitudinal and Transverse Wakefields Simulations and Studies in Dielectric-Coated Circular Waveguides	4708
	L. Ficcadenti Rome University La Sapienza, Roma, Italy A. Biagioni INFN/LNF, Frascati (Roma), Italy G. Castorina, D. Francescone, M. Marongiu, M. Migliorati, A. Mostacci, L. Palumbo Sapienza University of Rome, Rome, Italy
	In recent years, there has been a growing interest and rapid experimental progress on the use of e.m. fields produced by electron beams passing through dielectric-lined structures and on the effects they might have on the drive and witness bunches. Short ultra-relativistic electron bunches can excite very intense wakefields, which provide an efficient acceleration through the dielectric wakefield accelerators (DWA) scheme with higher gradient than that in the conventional RF LINAC. These beams can also generate high power narrow band THz coherent Cherenkov radiation. These high gradient fields may create strong instabilities on the beam itself causing issues in plasma acceleration experiments (PWFA), plasma lensing experiments and in recent beam diagnostic applications. In this work we report the results of the simulations and studies of the wakefields generated by electron beams at different lengths and charges passing on and off axis in dielectric-coated circular waveguides. We also propose a semi-analytical method to calculate these high gradient fields without resorting to time consuming simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML027
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Paper

Title

Page

Electron Cloud Studies in FCC-ee

374

E. Belli
Sapienza University of Rome, Rome, Italy
P. Costa Pinto, G. Rumolo, T.F. Sinkovits, M. Taborelli
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy

Electron cloud effects are one of the most critical aspects for the LHC and the future circular colliders. In the frame of the electron-positron collider FCC-ee, an estimation of the electron cloud build up in the machine will be discussed in this paper. A preliminary evaluation of the heat load in the arc components and interaction region magnets will be presented, together with possible mitigation strategies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK012

Export •

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

THPAF036

Longitudinal and Quadrupolar Coupling Impedance of an Elliptical Vacuum Chamber With Finite Conductivity in Terms of Mathieu Functions

3040

M. Migliorati, L. Palumbo
Sapienza University of Rome, Rome, Italy
N. Biancacci
CERN, Geneva, Switzerland
M. Migliorati, L. Palumbo
INFN-Roma1, Rome, Italy
V.G. Vaccaro
Naples University Federico II and INFN, Napoli, Italy

Funding: Work supported by the CERN PS-LIU project
The resistive wall impedance of an elliptical vacuum chamber in the classical regime with infinite thickness is known analytically for ultra-relativistic beams by means of the Yokoya form factors. Starting from the longitudinal electric field of a point charge moving at arbitrary speed in an elliptical vacuum chamber, which we express in terms of Mathieu functions, in this paper we take into account the finite conductivity of the beam pipe walls and evaluate the longitudinal and quadrupolar impedance for any beam velocity. We also obtain that the quadrupolar impedance of a circular pipe is different from zero, approaching zero only for ultra-relativistic particles. Even if some of the results, in particular in the ultra-relativistic limit, are already known and expressed in terms of form factors, this approach is the first step towards the calculation of the general problem of a multi-layer vacuum chamber with different conductivities and of elliptic cross section.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF036

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THPAK052

Single Bunch Instabilities in FCC-ee

3336

SUSPF076

use link to see paper's listing under its alternate paper code

E. Belli
Sapienza University of Rome, Rome, Italy
G. Castorina, M. Migliorati
INFN-Roma1, Rome, Italy
G. Rumolo
CERN, Geneva, Switzerland
B. Spataro, M. Zobov
INFN/LNF, Frascati (Roma), Italy

FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK052

Export •

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

TUPAF024

Impedance and Instability Studies in LEIR with Xenon

720

N. Biancacci, H. Bartosik, M. Gąsior, S. Hirlaender, V. Kain, T.E. Levens, E. Métral
CERN, Geneva, Switzerland
M. Migliorati
Rome University La Sapienza, Roma, Italy

In 2017, the LEIR accelerator has been operated with Xe³⁹⁺ beam for fixed target experiments in the SPS North Area. The different ion species, with respect to the usually operated Pb⁵⁴⁺, allowed for additional comparative measurements of tune shift versus intensity at injection energy both in coasting and bunched beams. The fast transverse instability observed for high accumulated intensities has been as well characterized and additional observations relevant to impedance have been collected from longitudinal Schottky signal and BTF measurements. The results of these measurements are summarised and compared to the currently developed machine impedance model.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF024

Export •

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

THPAK091

Design of the New Proton Synchrotron Booster Absorber Scraper (PSBAS) in the Framework of the Large Hadron Collider Injection Upgrade (LIU) Project

3444

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
J.A. Briz Monago, M. Calviani, N. Chritin, J.J. Esala, S.S. Gilardoni, I. Lamas Garcia, J. Maestre, T. Polzin, T.L. Rijoff
CERN, Geneva, Switzerland
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

The Large Hadron Collider (LHC) Injector Upgrade (LIU)Project at CERN calls for increasing beam intensity for the LHC accelerator chain. Some machine components will not survive the new beam characteristics and need to be rebuilt for the new challenging scenario. This is particularly true for beam intercepting devices (BIDs) such as dumps, collimators, and absorber/scrapers, which are directly exposed to beam impacts. In this context, this work summarizes conceptual design studies on the new Proton Synchrotron Booster (PSB) Absorber/Scraper (PSBAS), a device aimed at cleaning the beam halo at the very early stage of the PSB acceleration. This paper outlines the steps performed to fulfil the component design requirements. It discusses thermo-mechanical effects as a consequence of the beam-matter collisions, simulated with the FLUKA Monte Carlo code and ANSYS finite element software; and the impedance minimization study performed to prevent beam instabilities and to reduce RF-heating on the device.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK091

Export •

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

THPAK092

Analysis on the Mechanical Effects Induced by Beam Impedance Heating on the HL-LHC Target Dump Injection Segmented (TDIS) Absorber

3448

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
M. Calviani, D. Carbajo Perez, S.S. Gilardoni, F. Giordano, I. Lamas Garcia, G. Mazzacano, A. Perillo-Marcone
CERN, Geneva, Switzerland

The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In such a scenario, critical accelerator devices need to be redesigned and rebuilt. Impedance is among the design drivers, since its thermo-mechanical effects could lead to premature device failures. In this context, the current work reports the results of a multiphysics study to assess the electromagnetic and thermo-mechanical behaviour of the Target Dump Injection Segmented (TDIS). It first discusses the outcomes of the impedance analysis performed to characterise the resistive wall and the high order resonant modes (HOMs) trapped in the TDIS structures. Then, their RF-heating effects and the related temperature distribution are considered. Finally, mechanical stresses induced by thermal gradients are studied in order to give a final validation on the design quality.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK092

Export •

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

THPAK093

A Multi-Physics Approach to Simulate the RF Heating 3D Power Map Induced by the Proton Beam in a Beam Intercepting Device

3452

SUSPF075

use link to see paper's listing under its alternate paper code

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
D. Carbajo Perez, F. Giordano, I. Lamas Garcia, G. Mazzacano
CERN, Geneva, Switzerland

The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK093

Export •

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

THPAL009

A TM01 Mode Launcher With Quadrupole Field Components Cancellation for High Brightness Applications

3631

G. Castorina
INFN-Roma1, Rome, Italy
A.D. Cahill, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
F. Cardelli, G. Franzini, A. Marcelli, B. Spataro
INFN/LNF, Frascati (Roma), Italy
L. Celona, S. Gammino, G. Torrisi
INFN/LNS, Catania, Italy
V.A. Dolgashev
SLAC, Menlo Park, California, USA
L. Ficcadenti
Rome University La Sapienza, Roma, Italy
M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy
G. Sorbello
University of Catania, Catania, Italy

The R&D of high gradient radiofrequency (RF) devices is aimed to develop innovative accelerating structures based on new manufacturing techniques and materials in order to construct devices operating with the highest accelerating gradient. Recent studies have shown a large increase in the maximum sustained RF surface electric fields in copper structures operating at cryogenic temperatures. These novel approaches allow significant performance improvements of RF photoinjectors. Indeed the operation at high surface fields results in considerable increase of electron beam brilliance. This increased brilliance requires high field quality in the RF photoinjector and specifically in its power coupler. In this work we present a novel power coupler for the RF photoinjector. The coupler is a compact X-band TM01 mode launcher with a fourfold symmetry which minimized both the dipole and the quadrupole RF components.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL009

Export •

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

THPML027

Longitudinal and Transverse Wakefields Simulations and Studies in Dielectric-Coated Circular Waveguides

4708

L. Ficcadenti
Rome University La Sapienza, Roma, Italy
A. Biagioni
INFN/LNF, Frascati (Roma), Italy
G. Castorina, D. Francescone, M. Marongiu, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy

In recent years, there has been a growing interest and rapid experimental progress on the use of e.m. fields produced by electron beams passing through dielectric-lined structures and on the effects they might have on the drive and witness bunches. Short ultra-relativistic electron bunches can excite very intense wakefields, which provide an efficient acceleration through the dielectric wakefield accelerators (DWA) scheme with higher gradient than that in the conventional RF LINAC. These beams can also generate high power narrow band THz coherent Cherenkov radiation. These high gradient fields may create strong instabilities on the beam itself causing issues in plasma acceleration experiments (PWFA), plasma lensing experiments and in recent beam diagnostic applications. In this work we report the results of the simulations and studies of the wakefields generated by electron beams at different lengths and charges passing on and off axis in dielectric-coated circular waveguides. We also propose a semi-analytical method to calculate these high gradient fields without resorting to time consuming simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML027

Export •

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