Experimental characterization of gaseous ion beams produced with the advanced ion source for hadrontherapy (AISHa) at 18 GHz.

The Advanced Ion Source for Hadrontherapy (AISHa) is an electron cyclotron resonance ion source operating at 18 GHz, developed at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, with the aim of producing high intensity and low emittance highly charged ion beams for hadrontherapy purposes. Moreover, thanks to its unique peculiarities, AISHa is a suitable choice for industrial and scientific applications. In the framework of the INSpIRIT and IRPT projects, in collaboration with the Centro Nazionale di Adroterapia Oncologica, new candidates for cancer treatment are being developed. In particular, the paper presents the results of the commissioning of four ion beams of interest for hadrontherapy: H+, C4+, He2+, and O6+. Their charge state distribution in the best experimental conditions, their emittance, and brightness will be critically discussed, along with the role of ion source tuning and space charge effects in beam transport. Perspectives for further developments will also be presented.

Experimental characterization of the AISHa ion source.

The Advanced Ion Source for Hadrontherapy (AISHa) has been designed to generate high brightness multiply charged ion beams for hadron therapy applications. AISHa is a compact electron cyclotron resonance ion source whose hybrid magnetic system consists of a permanent Halbach-type hexapole magnet and a set of independently energized superconducting coils. This has allowed us to achieve high performances in a cost effective way. During the commissioning phase, a few criticalities have been observed and fixed in 2018/19; the improvements will be briefly described and the results of the operations with a single 18 GHz generator will be presented. Particular relevance will be given to the production of high intensity beams of oxygen, argon, and carbon, the latter having huge importance for hadron therapy applications. Perspectives for further improvements, including double frequency heating, will also be highlighted.

The first measurement of plasma density in an ECRIS-like device by means of a frequency-sweep microwave interferometer.

The note presents the first plasma density measurements collected by a novel microwave interferometer in a compact Electron Cyclotron Resonance Ion Sources (ECRIS). The developed K-band (18.5 ÷ 26.5 GHz) microwave interferometry, based on the Frequency-Modulated Continuous-Wave method, has been able to discriminate the plasma signal from the spurious components due to the reflections at the plasma chamber walls, when working in the extreme unfavorable condition λp ≃ Lp ≃ Lc (λp, Lp, and Lc being the probing signal wavelength, the plasma dimension and the plasma chamber length, respectively). The note describes the experimental procedure when probing a high density plasma (ne > 1 ⋅ 1018 cm-3) produced by an ECRIS prototype operating at 3.75 GHz.

A new H2 (+) source: Conceptual study and experimental test of an upgraded version of the VIS-Versatile ion source.

The versatile ion source is an off-resonance microwave discharge ion source which produces a slightly overdense plasma at 2.45 GHz of pumping wave frequency extracting more than 60 mA proton beams and 50 mA He(+) beams. DAEδALUS and IsoDAR experiments require high intensities for H2 (+) beams to be accelerated by high power cyclotrons for neutrinos generation. In order to fulfill the new requirements, a new plasma chamber and injection system has been designed and manufactured for increasing the H2 (+) beam intensity. In this paper the studies for the increasing of the H2 (+)/p ratio and for the design of the new plasma chamber and injection system will be shown and discussed together with the experimental tests carried out at Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) and at Best Cyclotron Systems test-bench in Vancouver, Canada.

Experimental investigation of non-linear wave to plasma interaction in a quasi-flat magnetostatic field.

A characterization of wave-to-plasma interaction in a quasi-flat magnetostatic field at 3.75 GHz has been carried out by using a small-wire movable RF antenna, connected to a spectrum analyzer. The coupling between electromagnetic and electrostatic waves leads to a characteristic spectral emission in low frequency range and around the pumping wave frequency. The most relevant results consist in the broadening of the pumping wave spectrum above critical RF power thresholds and in the generation of sidebands of the pumping frequency, with corresponding components in low frequency domain. The non-linearities are accompanied by the generation of overdense plasmas and intense fluxes of X-rays.