Anna Vnuchenko - Academia.edu (original) (raw)

Papers by Anna Vnuchenko

Research paper thumbnail of High Gradient Issues in S-band RF acceleration structure and Radio Frequency Quadrupoles for hadron therapy accelerators

Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therap... more Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therapy accelerators and Radio Frequency Quadrupoles ha estat realitzada baix la nostra direcció en el Departamento de Física Aplicada y Electromagnetismo de la Universitat de València per Anna Vnuchenko i constitueix la seua Tesi Doctoral. I per a que així conste, firmem el present Certificat. Firmat:Ángeles Faus Golfe Firmat: Benito Gimeno Martínez in the field of accelerators physics. I am sincerely grateful to my supervisor, Dr. Angeles Faus Golfe, for her always encouraging support and leadership despite the distance during these years. And also to my supervisor, Dr. Benito Gimeno Martinez, for his kind advices, support and a positive look at all the difficulties. Thanks to all the CLIC-RF group at CERN for the precious scientific and technical support to the high gradient test program and for letting me participate in this research project. I truly want to thank to Dr. Walter Wuensch for supervising me throughout my time at CERN. I appreciated a lot his guidance, the great ideas, the many useful advices, a lots of discussion and his patience. I would like to thank Dr. Nuria Catalan Lasheras, Dr. Igor Syratchev and Dr. Alexej Grudiev, for the enriching discussions about the preparation, development and analysis of the test. Also to thank Dr. Theodoros Argyropoulos for his first my supervising at CERN and introduction me to RF. And thanks to Gerard McMonagle for constant help with klystron/modulator system and Dr. Benjamin Woolley with LLRF. I am grateful to my Xbox colleagues Benjamin, Stefano, Sam, Jan, Veronica, Thom, Matteo for their help in setting up and running the cavities experiment. Thanks to the ADAM group for their hospitality and letting me participate in the high-power test of the RFQ used at test bench at CERN, and in particular, to Dr. Luis Navarro for the guiding me with measurements and development of the DAQ, Dr. Michele Caldara for the help of current measurement, Dario Soriano Guillen for constant help in the lab, and also Dr. Alberto De Giovanni Alberto and Dr. Yevgeniy Ivanisenko for advice. Further thanks go to the teams with whom I perform my experiments at Linac4.

Research paper thumbnail of Construction and Commissioning of the S-Band High-Gradient RF Laboratory at IFIC

HAL (Le Centre pour la Communication Scientifique Directe), Apr 29, 2018

An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commission... more An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN [1] and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid-2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described.

Research paper thumbnail of Simulation of Beam Formation in the CERN Negative Ion Source for the Linac4 Accelerator

Journal of physics, Apr 1, 2022

Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of t... more Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.

Research paper thumbnail of High-Gradient issues in S-band RF Acceleration Structure for Hadrontherapy accelerators and Radio Frequency Quadrupoles

Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therap... more Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therapy accelerators and Radio Frequency Quadrupoles ha estat realitzada baix la nostra direcció en el Departamento de Física Aplicada y Electromagnetismo de la Universitat de València per Anna Vnuchenko i constitueix la seua Tesi Doctoral. I per a que així conste, firmem el present Certificat. Firmat:Ángeles Faus Golfe Firmat: Benito Gimeno Martínez in the field of accelerators physics. I am sincerely grateful to my supervisor, Dr. Angeles Faus Golfe, for her always encouraging support and leadership despite the distance during these years. And also to my supervisor, Dr. Benito Gimeno Martinez, for his kind advices, support and a positive look at all the difficulties. Thanks to all the CLIC-RF group at CERN for the precious scientific and technical support to the high gradient test program and for letting me participate in this research project. I truly want to thank to Dr. Walter Wuensch for supervising me throughout my time at CERN. I appreciated a lot his guidance, the great ideas, the many useful advices, a lots of discussion and his patience. I would like to thank Dr. Nuria Catalan Lasheras, Dr. Igor Syratchev and Dr. Alexej Grudiev, for the enriching discussions about the preparation, development and analysis of the test. Also to thank Dr. Theodoros Argyropoulos for his first my supervising at CERN and introduction me to RF. And thanks to Gerard McMonagle for constant help with klystron/modulator system and Dr. Benjamin Woolley with LLRF. I am grateful to my Xbox colleagues Benjamin, Stefano, Sam, Jan, Veronica, Thom, Matteo for their help in setting up and running the cavities experiment. Thanks to the ADAM group for their hospitality and letting me participate in the high-power test of the RFQ used at test bench at CERN, and in particular, to Dr. Luis Navarro for the guiding me with measurements and development of the DAQ, Dr. Michele Caldara for the help of current measurement, Dario Soriano Guillen for constant help in the lab, and also Dr. Alberto De Giovanni Alberto and Dr. Yevgeniy Ivanisenko for advice. Further thanks go to the teams with whom I perform my experiments at Linac4.

Research paper thumbnail of H- Beam formation simulation in negative ion source for CERN's Linac4 accelerator

arXiv (Cornell University), Jan 31, 2023

The caesiated surface negative ion (H −) source is the first element of CERN's LINAC4 a linear in... more The caesiated surface negative ion (H −) source is the first element of CERN's LINAC4 a linear injector designed to accelerate negative hydrogen ions to 160 MeV. The IS03 ion source is operated at 35 mA beam intensity and reliably feeds CERN's accelerator chain, H − ions are generated via plasma volume and caesiated molybdenum (Cs-Mo) plasma electrode surface mechanisms. Studying the beam extraction region of this H − ion source is essential for optimizing the H − production. The 3D Particle-in-cell (PIC) Monte Carlo (MC) code ONIX (Orsay Negative Ion eXtraction [1]), written to study H − beam formation processes in neutral injectors for fusion, has been adapted to single aperture accelerator H − sources. The code was modified to match the conditions of the beam formation and extraction regions of the Linac4 H − source [2]. A set of parameters was chosen to characterize the plasma and to match the specific volume and surface production modes. Simulated results of the extraction regions are presented and benchmarked with experimental results obtained at the Linac4 test stand [3].

Research paper thumbnail of Design and Construction of a High-Gradient RF Lab at IFIC-Valencia

HAL (Le Centre pour la Communication Scientifique Directe), May 14, 2017

The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infr... more The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infrastructure for testing HG S-band normal-conducting RF accelerating structures and has been under construction since 2016. The main objective of the facility is to develop HG Sband accelerating structures and to contribute to the study of HG phenomena. A particular focus is RF structures for medical hadron therapy applications. The design of the laboratory has been made through collaboration between the IFIC and the CLIC RF group at CERN. The layout is inspired by the scheme of the Xbox-3 test facility [1, 2] at CERN, and it has been adapted to S-band frequency. In this paper we describe the design and construction status of such a facility.

Research paper thumbnail of CERN's IS03 H- Source Beam Formations Studies

Research paper thumbnail of Correlation of H- beam properties to Cs-coverage

Journal of Instrumentation

A caesiated RF driven source delivers H- ions that, after stripping at the end of the 160 MeV H- ... more A caesiated RF driven source delivers H- ions that, after stripping at the end of the 160 MeV H- linear injector, provides protons to CERN's accelerator complex including LHC, where the protons reached a record energy of 6.8 TeV. In Caesiated RF sources, H- ions are produced via dissociative attachment of electrons onto roto-vibrationally excited H2-molecules (volume) and re-emission as negative ions of protons or hydrogen atoms colliding on a low work function caesiated molybdenum plasma electrode (surface). During initial caesiation, the production mechanism evolves from the initial Cs-free volume production to a predominant surface production mode; the observed stunning reduction of co-extracted electrons is concomitant to an increase of the H- ion current to RF-power yield. This paper describes the evolution of the beam-profile at today's operational beam intensities of 35 mA for various ratios of volume and surface ion-origin. The presence of surface produced ions occur...

Research paper thumbnail of Preliminary Simulation of CERN’s Linac4 H⁻ Source Beam Formation

12th International Particle Accelerator Conference (IPAC'21), Campinas, SP, Brazil, 24-28 May 2021, Aug 1, 2021

Research paper thumbnail of H- Beam formation simulation in negative ion source for CERN's Linac4 accelerator

arXiv (Cornell University), Jan 31, 2023

Research paper thumbnail of High-Power Test of Two Prototype X-Band Accelerating Structures Based on SwissFEL Fabrication Technology

IEEE Transactions on Nuclear Science

This article presents the design, construction, and high-power test of two X-band radio frequency... more This article presents the design, construction, and high-power test of two X-band radio frequency (RF) accelerating structures built as part of a collaboration between CERN and the Paul Scherrer Institute (PSI) for the compact linear collider (CLIC) study. The structures are a modified "tuning-free" variant of an existing CERN design and were assembled using Swiss free electron laser (SwissFEL) production methods. The purpose of the study is twofold. The first objective is to validate the RF properties and high-power performance of the tuning-free, vacuum brazed PSI technology. The second objective is to study the structures' high-gradient behavior to provide insight into the breakdown and conditioning phenomena as they apply to high-field devices in general. Low-power RF measurements showed that the structure field profiles were close to the design values, and both structures were conditioned to accelerating gradients in excess of 100 MV/m in CERN's high-gradient test facility. Measurements performed during the second structure test suggest that the breakdown rate (BDR) scales strongly with the accelerating gradient, with the best fit being a power law relation with an exponent of 31.14. In both cases, the test results indicate that stable, high-gradient operation is possible with tuning-free, vacuum brazed structures of this kind.

Research paper thumbnail of Simulation of Beam Formation in the CERN Negative Ion Source for the Linac4 Accelerator

Journal of Physics: Conference Series

Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of t... more Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.

Research paper thumbnail of CERN's IS03 H- Source Beam Formations Studies

19th International Conference on Ion Sources (ICIS 2021), 2021

Research paper thumbnail of Beam Formation Studies on the CERN IS03b H Source

Journal of Physics: Conference Series

An H- ion source is being operated at the new 160 MeV linear injector (Linac4) of the CERN accele... more An H- ion source is being operated at the new 160 MeV linear injector (Linac4) of the CERN accelerator complex. The source’s plasma is of the Radio Frequency Inductively Coupled Plasma type (RF-ICP), without magnetic cusp and runs with Cs-loss compensation [1]. Vertical downward oriented filter- and electron dump-dipolar magnetic fields expand over the plasma chamber, beam-formation, beam-extraction and electron dump regions and generate horizontal asymmetry and beam angular deflection partially compensated by mechanical alignment of the front-end. The H- beam is generated via volume and caesiated plasma surface modes, the latter inducing a radial asymmetry characterized by an increased current density close to the plasma electrode surface [2]. Asymmetries affecting the meniscus shape, or its current density have to be simulated via 3D Particle In Cell Monte Carlo (PIC-MC) solvers, such as the Orsay Negative Ion eXtraction code (ONIX) [3]. Validation of these simulations require ded...

Research paper thumbnail of Preliminary Simulation of CERN's Linac4 H⁻ Source Beam Formation

Linac4 is the new (H⁻) linear injector of CERN's accelerator complex. This contribution descr... more Linac4 is the new (H⁻) linear injector of CERN's accelerator complex. This contribution describes the modelling activities required to get insight into H⁻ beam formation processes and their impact on beam properties. The simulation region starts from a homogeneous hydrogen plasma, the plasma then expands through the magnetic filter field. H⁻ ions and electrons are electrostatically extracted through the meniscus (line of separation between the plasma and the extracted beam) and eventually accelerated. The physics is simulated via the 3D PIC code ONIX. This code, originally dedicated to ITER's neutral injector sources, has been modified to match single aperture sources. A new type of boundary condition is described, as well as the field distribution and geometry of the standard IS03 and a dedicated proto-type of CERN's Linac4 H⁻ source. A plasma electrode prototype designed to provide metallic boundary conditions was produced and tested. This plasma electrode geometry ena...

Research paper thumbnail of Start-to-End Beam Dynamic Simulations for PRAE

The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multi... more The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multidisciplinary R&D facility in the Orsay campus gathering various scientific communities involved in radiobiology, subatomic physics, instrumentation and particle accelerators around an electron accelerator delivering a high-performance beam with energy up to 70 MeV and later 140 MeV, in order to perform a series of unique measurements and future challenging R&D. In this paper we report the first start-to-end simulations from the RF gun, going through the linac and finally to the different experimental platforms. The beam dynamics simulations have been performed using a concatenation of codes. In particular for the linac the RF-Track code recently developed at CERN will be used and benchmarked. The different working points have been analysed in order to minimise the transverse emittance and the beam energy spread including space charge effects at low electron energies.

Research paper thumbnail of CERN Yellow Reports: Monographs, Vol 2 (2018): The Compact Linear e+e− Collider (CLIC) : 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e−e^+e^−e+e− collider under ... more The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e−e^+e^−e+e− collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively, for a site length ranging from 11 km to 50 km. CLIC uses a two-beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in significant progress in recen...

Research paper thumbnail of High-gradient testing of an S -band, normal-conducting low phase velocity accelerating structure

Physical Review Accelerators and Beams, 2020

A novel high-gradient accelerating structure with low phase velocity, v=c ¼ 0.38, has been design... more A novel high-gradient accelerating structure with low phase velocity, v=c ¼ 0.38, has been designed, manufactured and high-power tested. The structure was designed and built using the methodology and technology developed for CLIC 100 MV=m high-gradient accelerating structures, which have speed of light phase velocity, but adapts them to a structure for nonrelativistic particles. The parameters of the structure were optimized for the compact proton therapy linac project, and specifically to 76 MeV energy protons, but the type of structure opens more generally the possibility of compact low phase velocity linacs. The structure operates in S-band, is backward traveling wave (BTW) with a phase advance of 150 degrees and has an active length of 19 cm. The main objective for designing and testing this structure was to demonstrate that low velocity particles, in particular protons, can be accelerated with high gradients. In addition, the performance of this structure compared to other type of structures provides insights into the factors that limit high gradient operation. The structure was conditioned successfully to high gradient using the same protocol as for CLIC X-band structures. However, after the high power test, data analysis realized that the structure had been installed backwards, that is, the input power had been fed into what is nominally the output end of the structure. This resulted in higher peak fields at the power feed end and a steeply decreasing field profile along the structure, rather than the intended near constant field and gradient profile. A local accelerating gradient of 81 MV=m near the input end was achieved at a pulse length of 1.2 μs and with a breakdown rate (BDR) of 7.2 × 10 −7 1=pulse=m. The reverse configuration was accidental but the operating with this field condition gave very important insights into high-gradient behaviour and a comprehensive analysis has been carried out. A particular attention was paid to the characterization of the distribution of BD positions along the structure and within a cell.

Research paper thumbnail of High-Gradient RF laboratory at IFIC for medical applications

General interest has been shown over the last years for compact and more affordable facilities fo... more General interest has been shown over the last years for compact and more affordable facilities for hadron-therapy. The High-Gradient (HG) know-how and technology for normal-conducting accelerating RF (Radio-Frequency) electron linac (linear accelerator) structures recently developed for projects such as CLIC (CERN), has raised the achievable accelerating gradient from 20-30 MV/m up to 100-120 MV/m. This gain has come through a better understanding of the high-power RF vacuum arcs or breakdowns (BD) phenomena, the development of quantitative HG RF design methods and refinements in fabrication techniques. This can allow for more compact linacs also for protons, which is potentially important in the new trend in hadron-therapy of using linacs able to provide protons of 70-230 MeV or light ions of 100-400 MeV/u. Linacs are of particular interest for medical applications because they can provide a high degree of flexibility for treatment, such as running at 100-400 Hz pulse rate and puls...

Research paper thumbnail of Construction and Commissioning of the S-Band High-Gradient RF Laboratory at IFIC

An S-Band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commission... more An S-Band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN* and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid 2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described.

Research paper thumbnail of High Gradient Issues in S-band RF acceleration structure and Radio Frequency Quadrupoles for hadron therapy accelerators

Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therap... more Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therapy accelerators and Radio Frequency Quadrupoles ha estat realitzada baix la nostra direcció en el Departamento de Física Aplicada y Electromagnetismo de la Universitat de València per Anna Vnuchenko i constitueix la seua Tesi Doctoral. I per a que així conste, firmem el present Certificat. Firmat:Ángeles Faus Golfe Firmat: Benito Gimeno Martínez in the field of accelerators physics. I am sincerely grateful to my supervisor, Dr. Angeles Faus Golfe, for her always encouraging support and leadership despite the distance during these years. And also to my supervisor, Dr. Benito Gimeno Martinez, for his kind advices, support and a positive look at all the difficulties. Thanks to all the CLIC-RF group at CERN for the precious scientific and technical support to the high gradient test program and for letting me participate in this research project. I truly want to thank to Dr. Walter Wuensch for supervising me throughout my time at CERN. I appreciated a lot his guidance, the great ideas, the many useful advices, a lots of discussion and his patience. I would like to thank Dr. Nuria Catalan Lasheras, Dr. Igor Syratchev and Dr. Alexej Grudiev, for the enriching discussions about the preparation, development and analysis of the test. Also to thank Dr. Theodoros Argyropoulos for his first my supervising at CERN and introduction me to RF. And thanks to Gerard McMonagle for constant help with klystron/modulator system and Dr. Benjamin Woolley with LLRF. I am grateful to my Xbox colleagues Benjamin, Stefano, Sam, Jan, Veronica, Thom, Matteo for their help in setting up and running the cavities experiment. Thanks to the ADAM group for their hospitality and letting me participate in the high-power test of the RFQ used at test bench at CERN, and in particular, to Dr. Luis Navarro for the guiding me with measurements and development of the DAQ, Dr. Michele Caldara for the help of current measurement, Dario Soriano Guillen for constant help in the lab, and also Dr. Alberto De Giovanni Alberto and Dr. Yevgeniy Ivanisenko for advice. Further thanks go to the teams with whom I perform my experiments at Linac4.

Research paper thumbnail of Construction and Commissioning of the S-Band High-Gradient RF Laboratory at IFIC

HAL (Le Centre pour la Communication Scientifique Directe), Apr 29, 2018

An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commission... more An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN [1] and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid-2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described.

Research paper thumbnail of Simulation of Beam Formation in the CERN Negative Ion Source for the Linac4 Accelerator

Journal of physics, Apr 1, 2022

Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of t... more Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.

Research paper thumbnail of High-Gradient issues in S-band RF Acceleration Structure for Hadrontherapy accelerators and Radio Frequency Quadrupoles

Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therap... more Que la present memòria High Gradient issues in S-band RF acceleration structure for hadron therapy accelerators and Radio Frequency Quadrupoles ha estat realitzada baix la nostra direcció en el Departamento de Física Aplicada y Electromagnetismo de la Universitat de València per Anna Vnuchenko i constitueix la seua Tesi Doctoral. I per a que així conste, firmem el present Certificat. Firmat:Ángeles Faus Golfe Firmat: Benito Gimeno Martínez in the field of accelerators physics. I am sincerely grateful to my supervisor, Dr. Angeles Faus Golfe, for her always encouraging support and leadership despite the distance during these years. And also to my supervisor, Dr. Benito Gimeno Martinez, for his kind advices, support and a positive look at all the difficulties. Thanks to all the CLIC-RF group at CERN for the precious scientific and technical support to the high gradient test program and for letting me participate in this research project. I truly want to thank to Dr. Walter Wuensch for supervising me throughout my time at CERN. I appreciated a lot his guidance, the great ideas, the many useful advices, a lots of discussion and his patience. I would like to thank Dr. Nuria Catalan Lasheras, Dr. Igor Syratchev and Dr. Alexej Grudiev, for the enriching discussions about the preparation, development and analysis of the test. Also to thank Dr. Theodoros Argyropoulos for his first my supervising at CERN and introduction me to RF. And thanks to Gerard McMonagle for constant help with klystron/modulator system and Dr. Benjamin Woolley with LLRF. I am grateful to my Xbox colleagues Benjamin, Stefano, Sam, Jan, Veronica, Thom, Matteo for their help in setting up and running the cavities experiment. Thanks to the ADAM group for their hospitality and letting me participate in the high-power test of the RFQ used at test bench at CERN, and in particular, to Dr. Luis Navarro for the guiding me with measurements and development of the DAQ, Dr. Michele Caldara for the help of current measurement, Dario Soriano Guillen for constant help in the lab, and also Dr. Alberto De Giovanni Alberto and Dr. Yevgeniy Ivanisenko for advice. Further thanks go to the teams with whom I perform my experiments at Linac4.

Research paper thumbnail of H- Beam formation simulation in negative ion source for CERN's Linac4 accelerator

arXiv (Cornell University), Jan 31, 2023

The caesiated surface negative ion (H −) source is the first element of CERN's LINAC4 a linear in... more The caesiated surface negative ion (H −) source is the first element of CERN's LINAC4 a linear injector designed to accelerate negative hydrogen ions to 160 MeV. The IS03 ion source is operated at 35 mA beam intensity and reliably feeds CERN's accelerator chain, H − ions are generated via plasma volume and caesiated molybdenum (Cs-Mo) plasma electrode surface mechanisms. Studying the beam extraction region of this H − ion source is essential for optimizing the H − production. The 3D Particle-in-cell (PIC) Monte Carlo (MC) code ONIX (Orsay Negative Ion eXtraction [1]), written to study H − beam formation processes in neutral injectors for fusion, has been adapted to single aperture accelerator H − sources. The code was modified to match the conditions of the beam formation and extraction regions of the Linac4 H − source [2]. A set of parameters was chosen to characterize the plasma and to match the specific volume and surface production modes. Simulated results of the extraction regions are presented and benchmarked with experimental results obtained at the Linac4 test stand [3].

Research paper thumbnail of Design and Construction of a High-Gradient RF Lab at IFIC-Valencia

HAL (Le Centre pour la Communication Scientifique Directe), May 14, 2017

The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infr... more The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infrastructure for testing HG S-band normal-conducting RF accelerating structures and has been under construction since 2016. The main objective of the facility is to develop HG Sband accelerating structures and to contribute to the study of HG phenomena. A particular focus is RF structures for medical hadron therapy applications. The design of the laboratory has been made through collaboration between the IFIC and the CLIC RF group at CERN. The layout is inspired by the scheme of the Xbox-3 test facility [1, 2] at CERN, and it has been adapted to S-band frequency. In this paper we describe the design and construction status of such a facility.

Research paper thumbnail of CERN's IS03 H- Source Beam Formations Studies

Research paper thumbnail of Correlation of H- beam properties to Cs-coverage

Journal of Instrumentation

A caesiated RF driven source delivers H- ions that, after stripping at the end of the 160 MeV H- ... more A caesiated RF driven source delivers H- ions that, after stripping at the end of the 160 MeV H- linear injector, provides protons to CERN's accelerator complex including LHC, where the protons reached a record energy of 6.8 TeV. In Caesiated RF sources, H- ions are produced via dissociative attachment of electrons onto roto-vibrationally excited H2-molecules (volume) and re-emission as negative ions of protons or hydrogen atoms colliding on a low work function caesiated molybdenum plasma electrode (surface). During initial caesiation, the production mechanism evolves from the initial Cs-free volume production to a predominant surface production mode; the observed stunning reduction of co-extracted electrons is concomitant to an increase of the H- ion current to RF-power yield. This paper describes the evolution of the beam-profile at today's operational beam intensities of 35 mA for various ratios of volume and surface ion-origin. The presence of surface produced ions occur...

Research paper thumbnail of Preliminary Simulation of CERN’s Linac4 H⁻ Source Beam Formation

12th International Particle Accelerator Conference (IPAC'21), Campinas, SP, Brazil, 24-28 May 2021, Aug 1, 2021

Research paper thumbnail of H- Beam formation simulation in negative ion source for CERN's Linac4 accelerator

arXiv (Cornell University), Jan 31, 2023

Research paper thumbnail of High-Power Test of Two Prototype X-Band Accelerating Structures Based on SwissFEL Fabrication Technology

IEEE Transactions on Nuclear Science

This article presents the design, construction, and high-power test of two X-band radio frequency... more This article presents the design, construction, and high-power test of two X-band radio frequency (RF) accelerating structures built as part of a collaboration between CERN and the Paul Scherrer Institute (PSI) for the compact linear collider (CLIC) study. The structures are a modified "tuning-free" variant of an existing CERN design and were assembled using Swiss free electron laser (SwissFEL) production methods. The purpose of the study is twofold. The first objective is to validate the RF properties and high-power performance of the tuning-free, vacuum brazed PSI technology. The second objective is to study the structures' high-gradient behavior to provide insight into the breakdown and conditioning phenomena as they apply to high-field devices in general. Low-power RF measurements showed that the structure field profiles were close to the design values, and both structures were conditioned to accelerating gradients in excess of 100 MV/m in CERN's high-gradient test facility. Measurements performed during the second structure test suggest that the breakdown rate (BDR) scales strongly with the accelerating gradient, with the best fit being a power law relation with an exponent of 31.14. In both cases, the test results indicate that stable, high-gradient operation is possible with tuning-free, vacuum brazed structures of this kind.

Research paper thumbnail of Simulation of Beam Formation in the CERN Negative Ion Source for the Linac4 Accelerator

Journal of Physics: Conference Series

Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of t... more Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.

Research paper thumbnail of CERN's IS03 H- Source Beam Formations Studies

19th International Conference on Ion Sources (ICIS 2021), 2021

Research paper thumbnail of Beam Formation Studies on the CERN IS03b H Source

Journal of Physics: Conference Series

An H- ion source is being operated at the new 160 MeV linear injector (Linac4) of the CERN accele... more An H- ion source is being operated at the new 160 MeV linear injector (Linac4) of the CERN accelerator complex. The source’s plasma is of the Radio Frequency Inductively Coupled Plasma type (RF-ICP), without magnetic cusp and runs with Cs-loss compensation [1]. Vertical downward oriented filter- and electron dump-dipolar magnetic fields expand over the plasma chamber, beam-formation, beam-extraction and electron dump regions and generate horizontal asymmetry and beam angular deflection partially compensated by mechanical alignment of the front-end. The H- beam is generated via volume and caesiated plasma surface modes, the latter inducing a radial asymmetry characterized by an increased current density close to the plasma electrode surface [2]. Asymmetries affecting the meniscus shape, or its current density have to be simulated via 3D Particle In Cell Monte Carlo (PIC-MC) solvers, such as the Orsay Negative Ion eXtraction code (ONIX) [3]. Validation of these simulations require ded...

Research paper thumbnail of Preliminary Simulation of CERN's Linac4 H⁻ Source Beam Formation

Linac4 is the new (H⁻) linear injector of CERN's accelerator complex. This contribution descr... more Linac4 is the new (H⁻) linear injector of CERN's accelerator complex. This contribution describes the modelling activities required to get insight into H⁻ beam formation processes and their impact on beam properties. The simulation region starts from a homogeneous hydrogen plasma, the plasma then expands through the magnetic filter field. H⁻ ions and electrons are electrostatically extracted through the meniscus (line of separation between the plasma and the extracted beam) and eventually accelerated. The physics is simulated via the 3D PIC code ONIX. This code, originally dedicated to ITER's neutral injector sources, has been modified to match single aperture sources. A new type of boundary condition is described, as well as the field distribution and geometry of the standard IS03 and a dedicated proto-type of CERN's Linac4 H⁻ source. A plasma electrode prototype designed to provide metallic boundary conditions was produced and tested. This plasma electrode geometry ena...

Research paper thumbnail of Start-to-End Beam Dynamic Simulations for PRAE

The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multi... more The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multidisciplinary R&D facility in the Orsay campus gathering various scientific communities involved in radiobiology, subatomic physics, instrumentation and particle accelerators around an electron accelerator delivering a high-performance beam with energy up to 70 MeV and later 140 MeV, in order to perform a series of unique measurements and future challenging R&D. In this paper we report the first start-to-end simulations from the RF gun, going through the linac and finally to the different experimental platforms. The beam dynamics simulations have been performed using a concatenation of codes. In particular for the linac the RF-Track code recently developed at CERN will be used and benchmarked. The different working points have been analysed in order to minimise the transverse emittance and the beam energy spread including space charge effects at low electron energies.

Research paper thumbnail of CERN Yellow Reports: Monographs, Vol 2 (2018): The Compact Linear e+e− Collider (CLIC) : 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e−e^+e^−e+e− collider under ... more The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e−e^+e^−e+e− collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively, for a site length ranging from 11 km to 50 km. CLIC uses a two-beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in significant progress in recen...

Research paper thumbnail of High-gradient testing of an S -band, normal-conducting low phase velocity accelerating structure

Physical Review Accelerators and Beams, 2020

A novel high-gradient accelerating structure with low phase velocity, v=c ¼ 0.38, has been design... more A novel high-gradient accelerating structure with low phase velocity, v=c ¼ 0.38, has been designed, manufactured and high-power tested. The structure was designed and built using the methodology and technology developed for CLIC 100 MV=m high-gradient accelerating structures, which have speed of light phase velocity, but adapts them to a structure for nonrelativistic particles. The parameters of the structure were optimized for the compact proton therapy linac project, and specifically to 76 MeV energy protons, but the type of structure opens more generally the possibility of compact low phase velocity linacs. The structure operates in S-band, is backward traveling wave (BTW) with a phase advance of 150 degrees and has an active length of 19 cm. The main objective for designing and testing this structure was to demonstrate that low velocity particles, in particular protons, can be accelerated with high gradients. In addition, the performance of this structure compared to other type of structures provides insights into the factors that limit high gradient operation. The structure was conditioned successfully to high gradient using the same protocol as for CLIC X-band structures. However, after the high power test, data analysis realized that the structure had been installed backwards, that is, the input power had been fed into what is nominally the output end of the structure. This resulted in higher peak fields at the power feed end and a steeply decreasing field profile along the structure, rather than the intended near constant field and gradient profile. A local accelerating gradient of 81 MV=m near the input end was achieved at a pulse length of 1.2 μs and with a breakdown rate (BDR) of 7.2 × 10 −7 1=pulse=m. The reverse configuration was accidental but the operating with this field condition gave very important insights into high-gradient behaviour and a comprehensive analysis has been carried out. A particular attention was paid to the characterization of the distribution of BD positions along the structure and within a cell.

Research paper thumbnail of High-Gradient RF laboratory at IFIC for medical applications

General interest has been shown over the last years for compact and more affordable facilities fo... more General interest has been shown over the last years for compact and more affordable facilities for hadron-therapy. The High-Gradient (HG) know-how and technology for normal-conducting accelerating RF (Radio-Frequency) electron linac (linear accelerator) structures recently developed for projects such as CLIC (CERN), has raised the achievable accelerating gradient from 20-30 MV/m up to 100-120 MV/m. This gain has come through a better understanding of the high-power RF vacuum arcs or breakdowns (BD) phenomena, the development of quantitative HG RF design methods and refinements in fabrication techniques. This can allow for more compact linacs also for protons, which is potentially important in the new trend in hadron-therapy of using linacs able to provide protons of 70-230 MeV or light ions of 100-400 MeV/u. Linacs are of particular interest for medical applications because they can provide a high degree of flexibility for treatment, such as running at 100-400 Hz pulse rate and puls...

Research paper thumbnail of Construction and Commissioning of the S-Band High-Gradient RF Laboratory at IFIC

An S-Band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commission... more An S-Band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN* and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid 2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described.