Publications by Riccardo Agnello

Experimental Observation of the Motion of Ions in a Resonantly Driven Plasma Wakefield Accelerator

Patrick Blanchard, Ambrogio Fasoli, Ivo Furno, Yanis Andrebe, Riccardo Agnello, Christine Stollberg

We show experimentally that an effect of motion of ions, observed in a plasma-based accelerator, depends inversely on the plasma ion mass. The effect appears within a single wakefield event and manifests itself as a bunch tail, occurring only when sufficie ...

2025

Technology challenges and integration of the plasma position reflectometer in RFX-mod2

Riccardo Agnello

The integration of the new plasma position reflectometer in the RFX-mod2 experiment (the upgraded version of the previous RFX-mod that operated until 2015) is presented in this contribution. Particular attention has been devoted to the high field side subs ...

Elsevier Science Sa2024

Optical emission spectroscopy and microwave reflectometry for magnetised plasmas: Applications to ion sources and fusion machines

Riccardo Agnello

. - Investigation of magnetised plasmas by advanced diagnostics is a relevant topic in the frame of ion sources for high-performance particle accelerators and in thermonuclear fusion research for energetic purposes. In this paper, we propose two different ...

SOC ITALIANA FISICA2024

Hosing of a Long Relativistic Particle Bunch in Plasma

Patrick Blanchard, Ambrogio Fasoli, Ivo Furno, Yanis Andrebe, Alban Sublet, Sun Hee Kim, Riccardo Agnello, Christine Stollberg, Shuai Liu

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, selfmodulation in the perpendicular plane, at frequencies clo ...

Amer Physical Soc2024

Optimizing the ITER NBI ion source by dedicated RF driver test stand

Riccardo Agnello

The experimental fusion reactor ITER will feature two (or three) heating neutral beam injectors (NBI) capable of delivering 33(or 50) MW of power into the plasma. A NBI consists of a plasma source for production of negative ions (extracted negative ion cur ...

Institute of Physics2024

Filamentation of a relativistic proton bunch in plasma

Patrick Blanchard, Ambrogio Fasoli, Ivo Furno, Yanis Andrebe, Riccardo Agnello, Christine Stollberg

We show in experiments that a long, underdense, relativistic proton bunch propagating in plasma undergoes the oblique instability, which we observe as filamentation. We determine a threshold value for the ratio between the bunch transverse size and plasma ...

2024

Numerical and experimental investigations of a microwave interferometer for the negative ion source SPIDER

Ivo Furno, Rémy Jacquier, Riccardo Agnello

The electron density close to the extraction grids and the co-extracted electrons represent a crucial issue when operating negative ion sources for fusion reactors. An excessive electron density in the plasma expansion region can indeed inhibit the negativ ...

IOP Publishing Ltd2023

Continuous pulse advances in the negative ion source NIO1

Riccardo Agnello

Consorzio RFX and INFN-LNL have designed, built and operated the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1) with the aim of studying the production and acceleration of H- ions. In particular, NIO1 was designed to ke ...

2023

Development of the self-modulation instability of a relativistic proton bunch in plasma

Patrick Blanchard, Ambrogio Fasoli, Ivo Furno, Samuel Rey-Mermet, Yanis Andrebe, Alban Sublet, Sun Hee Kim, Ana Francisca Leal Silva Soares, Riccardo Agnello, Christine Stollberg, Shuai Liu

Self-modulation is a beam-plasma instability that is useful to drive large-amplitude wakefields with bunches much longer than the plasma skin depth. We present experimental results showing that, when increasing the ratio between the initial transverse size ...

2023

A double-ended helicon source to symmetrize RAID plasma

Philippe Frédérique Bruno Guittienne, Alan Howling, Ivo Furno, Rémy Jacquier, Marcelo Baquero Ruiz, Riccardo Agnello, Christine Stollberg

Neutral Beam Injectors (NBI) for post-DEMO-like reactors must achieve a neutralization efficiency (fraction neutrals/ions) above 70%. To reach this, NBIs based on negative ions are necessary and an innovative concept of this type of injector is based on ph ...

2023

Improvement of SPIDER diagnostic systems

Riccardo Agnello, Michele Fadone

2023

Measurement of stripping losses in the negative ion source SPIDER

Riccardo Agnello

The negative ion source SPIDER at Consorzio RFX (Italy) is a crucial experimental step towards the development of the Heating Neutral Beam (HNB) injectors for ITER. The goal of SPIDER is to operate and optimize a full-scale negative ion source in hydrogen ...

ELSEVIER SCIENCE SA2023

Highlights of recent SPIDER results and improvements

Riccardo Agnello

Three years of experiments on SPIDER allowed characterization of the main features of the source plasma and of the negative ion beam, in the original design configuration. For the large dimensions of the source chamber, and of the extraction area, the inve ...

2023

Characterization of cesium and H-/D- density in the negative ion source SPIDER

Riccardo Agnello

The Heating Neutral Beam Injectors (HNBs) for ITER will have to deliver 16.7 MW beams of H/D particles at 1 MeV energy. The beams will be produced from H -/D- ions, generated by a radiofrequency plasma source coupled to an ion acceleration system. A protot ...

2023

Lessons learned after three years of SPIDER operation and the first MITICA integrated tests

Riccardo Agnello

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power p ...

2023

A 1.5D fluid-Monte Carlo model of a hydrogen helicon plasma

Philippe Frédérique Bruno Guittienne, Alan Howling, Ivo Furno, Rémy Jacquier, Riccardo Agnello

Helicon plasma sources operating with hydrogen or deuterium might be attractive for fusion applications due to their higher power efficiency compared to inductive radiofrequency plasma sources. In recent years, the resonant antenna ion device (RAID) has be ...

2022

Characterization of Cs-free negative ion production in the ion source SPIDER by cavity ring-down spectroscopy

Riccardo Agnello

The neutral beam injectors of the ITER experiment will be based on negative ion sources for the generation of beams composed by 1MeV H/D particles. The prototype of these sources is currently under testing in the SPIDER experiment, part of the Neutral Beam ...

2022

First operations with caesium of the negative ion source SPIDER

Riccardo Agnello, Michele Fadone, Alberto Ferro

The negative-ion based neutral beam injector for heating and current drive of the ITER plasma (ITER HNB) is under development, at present focusing on the optimization of the full-scale plasma source in the SPIDER test stand. The production of H- or D- ions ...

IOP Publishing Ltd2022

Study of Negative Ion Beamlets Produced in SPIDER by Beam Emission Spectroscopy

Riccardo Agnello

Among the beam diagnostics routinely employed in source for production of ion of deuterium (SPIDER), beam emission spectroscopy (BES) provides valuable information for beam characterization, thus driving source optimization methods. In particular, this tec ...

2022

The AWAKE Run 2 Programme and Beyond

Patrick Blanchard, Ambrogio Fasoli, Ivo Furno, Yanis Andrebe, Riccardo Agnello, Christine Stollberg

Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. The use of high energy protons to drive wakefields in plasma has been demonstrated during Run 1 of the AWAKE programme at CERN. Protons of energy 400 GeV d ...

2022