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The AISHa ion source is an Electron Cyclotron Resonance Ion Source designed to generate high brightness multiply charged ion beams with high reliability, easy operations and maintenance for hadrontheraphy applications. The R performed by the INFN-LNS team during the 2019/2020 has allowed the improvement of the AISHa performances up to 20% for some of the extracted beams: both injection and extraction flanges has been improved and a movable electrode has been installed. The low energy beam transport has been equipped of an Emittance Measurement Unit (EMU), working through the beam wire scanners principle, for the measurement of the vertical and horizontal emittance of the beams of interest for hadrontherapy applications. Beam emittance has been characterized as a function of q/m and of the beam intensity to highlight space charge effects. If necessary, the beam wire scanners can be used for the characterization of the beam shape. The perspectives for further developments and plasma diagnostics will be also highlighted., Proceedings of the 24th International Workshop on ECR Ion Sources, ECRIS2020, East Lansing, MI, USA

The plasma chamber and injection system design play a fundamental role in ECRISs with the aim to obtain an optimized electromagnetic field configuration able to generate and sustain a plasma with a high energy content. In this work we present the numerical study and the design of an unconventionally-shaped cavity resonator* that possesses some key advantages with respect to the standard cylindrical cavities, usually adopted in ion sources setups. The cavity geometry, whose design has been completed on January 2020, has been inspired by the typical star-shaped ECR plasma, determined by the magnetic field structure. The chamber has been designed by using the commercial softwares CST and COMSOL, with the aim to maximize the on-axis electric field. Moreover, a radically innovative microwaves injection system, consisting in side-coupled slotted waveguides, has been implemented, allowing a better power coupling and a more symmetric power distribution inside the cavity with respect to the standard rectangular waveguides. This new ’plasma-shaped oriented’ design could relevantly improve the performances of the ECRISs while making more compact the overall setup., Proceedings of the 24th International Workshop on ECR Ion Sources, ECRIS2020, East Lansing, MI, USA

High resolution spatially-resolved X-ray spectroscopy, by means of a X-ray pin-hole camera setup* ** operating in the 0.5-20 keV energy domain, is a very powerful method for ECRIS plasma structure evaluation. We present the setup installed at a 14 GHz ECRIS (ATOMKI, Debrecen), including a multi-layered collimator enabling measurements up to several hundreds of watts of RF pumping power and the achieved spatial and energy resolution (0.5 mm and 300 eV). Results coming by a new algorithm for analyzing Integrated (multi-events detection) and Photon-Counted images (single-event detection) to perform energy-resolved investigation will be described. The analysis permits to investigate High-Dynamic-Range (HDR) and spectrally resolved images, to study the effect of the axial and radial confinement (even separately), the plasma radius, the fluxes of deconfined electrons distinguishing fluorescence lines of the materials of the plasma chamber (Ti, Ta) from plasma (Ar) fluorescence lines. This method allows a detailed characterization of warm electrons, important for ionization, and to quantitatively estimate local plasma density and spectral temperature pixel-by-pixel., Proceedings of the 24th International Workshop on ECR Ion Sources, ECRIS2020, East Lansing, MI, USA

Resonant interaction with microwave radiation in ECRIS plasma leads to a strongly anisotropic electron energy distribution function (EEDF), given as a combination of two to three electron populations, with anisotropy that might trigger kinetic instabilities. At the INFN, further efforts have been paid to improve and update self-consistent 3D numerical codes for plasma electrons kinetics. Progresses have opened several perspectives. It is now possible to derive a space-resolved EEDF, providing local information on electron properties. Also, the code has been updated to provide reaction rates of electromagnetic emissions, including X-ray fluorescence. Estimates of the local ion charge state distribution is potentially possible, and first evaluations are ongoing. Dealing with fast-transient mechanisms, such as electromagnetic emission via the electron-cyclotron MASER instability, the code is now updated for locally evaluating the EEDF anisotropy. We will present the collected results, which we believe to have a relevant impact both on the ECRIS plasma physics and on the INFN’s PANDORA project that plans to use ECR plasmas for fundamental studies in Nuclear and AstroNuclear Physics., Proceedings of the 24th International Workshop on ECR Ion Sources, ECRIS2020, East Lansing, MI, USA

Plasma instabilities limit the ECR Ion Sources performances in terms of flux of the extracted highly charged ions by causing beam ripple and unstable operation conditions. In a 14 GHz ECRIS (Atomki, Debrecen), the effect on the plasma instabilities in an Argon plasma at Two Close Frequencies heating scheme (the frequency gap is smaller than 1 GHz) has been explored. A special multi-diagnostic setup [1, 2] has been designed and implemented consisting of detectors for the simultaneous collection of plasma radio-self-emission and of high spatial resolution X-ray images in the 500 eV - 20 keV energy domain (using an X-ray pin-hole camera setup). We present the comparison of plasma structural changes as observed from X-ray images in single and double-frequency operations. The latter has been particularly correlated to the confinement and velocity anisotropy, also by considering results coming from numerical simulations., Proceedings of the 24th International Workshop on ECR Ion Sources, ECRIS2020, East Lansing, MI, USA

Hollow core dielectric microstructures powered by lasers represent a new and promising area of accelerator research thanks to the higher damage threshold and accelerating gradients with respect to metals at optical wavelengths. In this paper we present the design of a dielectric Electromagnetic Band Gap (EBG) mode converter for high-power coupling of the accelerating mode in Dielectric Laser Accelerators (DLAs). The design is wavelength-independent, and here we propose an implementation operating at 90.505 GHz (wavelength 3.3 mm) based on a silicon woodpile structure. The coupler is composed by two perpendicularly coupled hollow-core waveguides: a TE-like mode waveguide (excited from RF/laser power) and a TM-like mode accelerating waveguide. The structure has been numerically designed and optimized, presenting Insertion Losses (IL) 0.3 dB and an efficient mode conversion in the operating bandwidth. The properties and effectiveness of the confined accelerating mode have been optimized in order to derive the needed accelerating gradient. The simulated electric field has been used as input for Astra beam-dynamics simulations in order to compute the beam properties., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

ECR Ion Sources are deemed to be among the most performing ion sources feeding particle accelerators, cyclotrons in particular. Improvements of their performances strictly depend on the knowledge of plasma physics in compact magnetic traps. The paper will comment on the results obtained by the INFN-LNS team and international collaborators by means of a multi-diagnostics setup able to monitor the evolution in space and time of several plasma parameters, simultaneously with beam extraction and analysis in the LEBT, in single vs. double frequency operations, including the RF power and magnetic field scalings, and exploring regimes dominated by plasma turbulence. The results are relevant for the operations of existing ion sources and for the design of new ones. Compact magnetic traps fashioned in a similar way of ECRISs can be considered as an experimental environment by itself: we are exploring this opportunity relying to the in-plasma measurements of radionuclides lifetimes (in particular, beta-decaying elements): CosmoChronometers or nuclei involved in the s-process nucleosynthesis are among the case studies, opening new perspectives in the nuclear astrophysics field., Proceedings of the 22nd International Conference on Cyclotrons and their Applications, Cyclotrons2019, Cape Town, South Africa

Several experiments have recently demonstrated that plasma instabilities are powerful limiting factors to the flux of highly charged ion beam extracted from ECRIS. One of the methods for damping the instabilities is to feed the plasma in two frequency heating mode. Since the fundamental physical mechanism is still unclear (diffusion in velocity space? additional confinement?), a deeper experimental investigation is necessary, using multi-diagnostics setups. At ATOMKI-Debrecen the effect on the plasma instabilities of an argon plasma in a 'Two Close Frequencies' scheme has been explored. Spectra of radio-emission from the plasma have been collected for different frequency gaps and relative power balances. The measurements show the plasma self-emitted radiation comes out from the internal plasma (i.e. around the lower frequency) but the instability damping can be effective for some specific combinations of frequency-gap and power balance. Radiofrequency spectra have been collected simultaneously to time-resolved X-ray measurements, triggered by RF bursts produced by the instabilities and detected via a microwave diode connected to a plasma-chamber-immersed multi-pin RF probe., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy

The time-resolved characterization of the X-ray emission represents an innovative technique to investigate the heating mechanism of the worm/hot electron component in ECRIS devices. In this paper, the technique has been described and the results of an experimental campaign of measurements in order to characterize the X-rays emission of an axis-symmetric simple mirror trap has been showed. Particular attention has been paid to the ignition and turning off phase. This approach has permitted to estimate confinement time of the warm/hot electron population and put in evidence eventual instability effects during the critical phases. Further developments and perspectives of the technique will be highlighted., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy

The high intensity proton source for the European Spallation Source, designed and commissioned at INFN-LNS, is able to produce a stable total current between 40 and 125 mA through an 8 mm extraction aperture, with a proton fraction up to 87%. The best source condition for PS-ESS requirements has been investigated by means of the Optical Emission Spectroscopy (OES). OES has permitted to evaluate simultaneously the H/H2 relative abundances together with electron density and temperature. Results demonstrated that high intensity proton beams are generated in overdense plasma conditions (around 10¹⁸ m⁻³ electron density measured by OES), while electron temperature shows a decreasing trend with power. The results will be discussed and compared with Faraday-cup and Doppler shift measurements. Further upgrades of OES diagnostics will be highlighted., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy

In the framework of ASIF "ASI Supported Irradiation Facilities" project some beamlines available at Laboratori Nazionali del Sud-INFN (LNS) Catania have been dedicated to irradiation test. These beamlines have been recently upgraded in order to meet the ESA specifications about radiation hardness testing of devices suitable for space applications. The Superconducting Cyclotron K800 installed at LNS can provide protons up to 80 MeV for integrated dose tests and a number of heavy ion beams for Single Event Effect (SEE) studies. The beamlines are equipped with detectors that allow beam diagnostic in term of spatial uniformity, purity and energy measurement, including on-line monitoring of flux and fluence received by the device under test. Upgrades activities are now ongoing, especially to broaden up the number of available beams, both in terms of ion species and energy, to optimize the switching times from one beam to another. The paper will present an overview of the developed facility, which will take benefit of the ongoing SERSE (the superconducting ECR ion source) revamping: the new gas-box system, plasma chamber and controls system are ready to be installed within autumn 2018., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy

The AISHa ion source has been designed to generate high brightness multiply charged ion beams with high reliability, easy operations and maintenance for hadrontheraphy applications. Aisha is a compact ECRIS whose hybrid magnetic system consists of a permanent Halbach-type hexapole magnet and a set of independently energized superconducting He-free coils. The present work shows the results of the ion source commissioning in SFH operational mode (18 GHz) for different ion species. Current status and further improvements will be highlighted., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy