LINAC2022 - List of Authors (Ramberger, S.)

Paper	Title	Page
MO1PA03	First Years of Linac4 RF Operation	25
	S. Ramberger, R. Wegner CERN, Meyrin, Switzerland
	Following the construction, commissioning, run-in, and connection, in 2021 Linac4 at CERN saw its successful start-up to full operation. Being composed primarily of RF systems, occupying most of the tunnel and the equipment hall, a coordinated effort has been put in place by 4 RF teams providing cavities, amplifier chains, low-level RF and general control systems. While all parts came together with impressive performance from day one, many details required a considerable debugging effort to achieve the requested availability of at least 95% from first operation in the synchrotron complex. This talk will focus on issues in equipment reliability, radiation to electronics, thermal stability, systems interaction, as well as a few aspects of complex low-level RF setup. It will also discuss decisions taken with respect to spare policies and upgrades for the coming years.
	Slides MO1PA03 [3.992 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MO1PA03
About •	Received ※ 14 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 02 September 2022 — Issue date ※ 11 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOPA06	Microscopy Investigation on Different Materials After Pulsed High Field Conditioning and Low Energy H-Irradiation	422
SUPCJO06	use link to see paper's listing under its alternate paper code
	C.F. Da Palma Serafim, G. Bellodi, S. Calatroni, A. Grudiev, A.M. Lombardi, R.C. Peacock, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch CERN, Meyrin, Switzerland F. Djurabekova HIP, University of Helsinki, Finland
	During operation the LINAC4 RFQ (Radio-Frequency-Quadrupole) is exposed to high electric fields which can lead to vacuum breakdown. It is also subject to beam loss that can cause surface modification, including blistering, which can result in reduced electric field handling and an increased breakdown rate. An experimental study has been made to identify materials with high electric field capability and robustness to low-energy irradiation. In this paper we briefly discuss the selection criteria and we analyze these materials investigating their metallurgical properties using advanced microscopic techniques such as Scanning Electron Microscope, Electron Back Scattered Diffraction, Energy-dispersive X-ray Spectroscopy and conventional optical microscopy. These allow to observe and characterize the different materials on aμand a nano-scale, allowing us to compare results before and after irradiation and breakdown testing.
	Poster TUPOPA06 [2.771 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA06
About •	Received ※ 14 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 31 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOPA13	Pulsed DC High Field Measurements of Irradiated and Non-Irradiated Electrodes of Different Materials	441
SUPCJO07	use link to see paper's listing under its alternate paper code
	R.C. Peacock, G. Burt Lancaster University, Lancaster, United Kingdom G. Bellodi, S. Calatroni, C.F. Da Palma Serafim, A. Grudiev, A.M. Lombardi, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch CERN, Meyrin, Switzerland
	Beam loss occurs in Radio Frequency Quadrupoles (RFQ), and has been observed in the H⁻ linear accelerator Linac4 (L4) at CERN. To determine if beam loss can induce breakdowns, and to compare the robustness of different materials, tests have been done using pulsed high-voltage DC systems. Electrical breakdown phenomena and conditioning processes have been studied using these systems. Cathodes of different materials were irradiated with 1.2x10¹⁹ H⁻ p/cm², the estimated beam loss of the L4 RFQ over 10 days. The irradiated electrodes were installed in a system to observe if the irradiated area coincided with the breakdown locations, with pulsing parameters similar to the RFQ. Tests of irradiated and non-irradiated electrodes of the same material were done for comparison. The main difference observed was an increase in the number of breakdowns during the initial conditioning that returned to non-irradiated sample values with further running. Visual observations after irradiation show the beam centre and a halo the same diameter of the beam pipe. Breakdown clusters occur in the centre and halo regions, suggesting irradiation is not the only factor determining the breakdown probability.
	Poster TUPOPA13 [3.845 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA13
About •	Received ※ 23 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 07 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

First Years of Linac4 RF Operation

25

S. Ramberger, R. Wegner
CERN, Meyrin, Switzerland

Following the construction, commissioning, run-in, and connection, in 2021 Linac4 at CERN saw its successful start-up to full operation. Being composed primarily of RF systems, occupying most of the tunnel and the equipment hall, a coordinated effort has been put in place by 4 RF teams providing cavities, amplifier chains, low-level RF and general control systems. While all parts came together with impressive performance from day one, many details required a considerable debugging effort to achieve the requested availability of at least 95% from first operation in the synchrotron complex. This talk will focus on issues in equipment reliability, radiation to electronics, thermal stability, systems interaction, as well as a few aspects of complex low-level RF setup. It will also discuss decisions taken with respect to spare policies and upgrades for the coming years.

Slides MO1PA03 [3.992 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MO1PA03

About •

Received ※ 14 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 02 September 2022 — Issue date ※ 11 September 2022

Cite •

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

TUPOPA06

Microscopy Investigation on Different Materials After Pulsed High Field Conditioning and Low Energy H-Irradiation

422

SUPCJO06

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

C.F. Da Palma Serafim, G. Bellodi, S. Calatroni, A. Grudiev, A.M. Lombardi, R.C. Peacock, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch
CERN, Meyrin, Switzerland
F. Djurabekova
HIP, University of Helsinki, Finland

During operation the LINAC4 RFQ (Radio-Frequency-Quadrupole) is exposed to high electric fields which can lead to vacuum breakdown. It is also subject to beam loss that can cause surface modification, including blistering, which can result in reduced electric field handling and an increased breakdown rate. An experimental study has been made to identify materials with high electric field capability and robustness to low-energy irradiation. In this paper we briefly discuss the selection criteria and we analyze these materials investigating their metallurgical properties using advanced microscopic techniques such as Scanning Electron Microscope, Electron Back Scattered Diffraction, Energy-dispersive X-ray Spectroscopy and conventional optical microscopy. These allow to observe and characterize the different materials on aμand a nano-scale, allowing us to compare results before and after irradiation and breakdown testing.

Poster TUPOPA06 [2.771 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA06

About •

Received ※ 14 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 31 August 2022

Cite •

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

TUPOPA13

Pulsed DC High Field Measurements of Irradiated and Non-Irradiated Electrodes of Different Materials

441

SUPCJO07

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

R.C. Peacock, G. Burt
Lancaster University, Lancaster, United Kingdom
G. Bellodi, S. Calatroni, C.F. Da Palma Serafim, A. Grudiev, A.M. Lombardi, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch
CERN, Meyrin, Switzerland

Beam loss occurs in Radio Frequency Quadrupoles (RFQ), and has been observed in the H⁻ linear accelerator Linac4 (L4) at CERN. To determine if beam loss can induce breakdowns, and to compare the robustness of different materials, tests have been done using pulsed high-voltage DC systems. Electrical breakdown phenomena and conditioning processes have been studied using these systems. Cathodes of different materials were irradiated with 1.2x10¹⁹ H⁻ p/cm², the estimated beam loss of the L4 RFQ over 10 days. The irradiated electrodes were installed in a system to observe if the irradiated area coincided with the breakdown locations, with pulsing parameters similar to the RFQ. Tests of irradiated and non-irradiated electrodes of the same material were done for comparison. The main difference observed was an increase in the number of breakdowns during the initial conditioning that returned to non-irradiated sample values with further running. Visual observations after irradiation show the beam centre and a halo the same diameter of the beam pipe. Breakdown clusters occur in the centre and halo regions, suggesting irradiation is not the only factor determining the breakdown probability.

Poster TUPOPA13 [3.845 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA13

About •

Received ※ 23 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 07 September 2022

Cite •

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