AISHa: the LNS Ion Source for the Hadron Therapy facility

The Advanced Ion Source for Hadrontherapy, AISHa, is an Ion Source designed with the typical requirements of hospital facilities where the minimization of the mean time between failures and the fast maintenance operations are key issues together with the low ripple, high stability, and high reproducibility of the ion beams produced. For these peculiarities and for the ability to produce high brightness multiply charged ion beams, the Aisha source is a suitable solution to feed accelerators as cyclotrons.
The features included in the design of the AISHa source exploit all the knowledge acquired from INFN-LNS in the last decades in the ion source design and realization.

The core of the source

The core of the AISHa source is hybrid magnetic system consists of a 36 segment permanent Halbach-type hexapole magnet and a set of 4 superconducting coils. The coils are enclosed in a compact cryostat equipped with two double-stage cryocoolers that allow us to reach in 40h, in Liquid Helium free, operation the operating conditions. The plasma chamber is placed at high voltage and insulated to the ground by a glass/carbon fiber tube surrounding the hexapole, in order to keep the superconducting magnets and the yoke at ground potential, allowing reliable operation up to 40 kV.
The microwave injection system was designed to operate in both single and double frequency mode through two high-power klystron amplifier able to delivering up to 1.5 kW around 18 and 21 GHz respectively. The microwave amplifiers are located at ground and they are insulated from the plasma chamber by two ad hoc electromagnetic passive device acting as a DC-break, designed and developed entirely at the LNS. The three electrodes movable extraction system was designed to pull out a particle beam avoiding that the electrons transported by the ion beam are accelerated again backwards. The source is followed by a beamline consisting of a focusing solenoid placed downstream of the extraction, a 90° bending dipole for ion selection and two diagnostic boxes. Each diagnostics box consists of a Faraday Cup, two beam wire scanners and four slits forming an Allison scanner to measure the transverse emittance and allowing a complete characterization of the beam.

The last commissioning

The following table shows the commissioning results at 18 GHz with related emittance values:

Due to its characteristics and ability to produce medium/high charged ion beams, the AISHa source was chosen as the new source of the INSpIRIT project.

INSpIRIT is an expansion project of the National Centre for Oncological Hadrontherapy (CNAO) which foresees as well as the revamping of critical components of the Synchrotron, the introduction of a new source, named AISHA-CNAO, to provide Helium, Oxygen, Lithium and Iron beams. The new source will allow to develop new clinical protocols for the treatment of inoperable or radioresistant tumors where it is essential to minimize the dose absorbed by healthy tissues and it will open new scenarios for nuclear-physics and material experiments.

The new AISHA source inside the CNAO synchrotron room during assembly phase

References

[2022] O. Leonardi at al., An improved AISHa ion source for new clinical protocols, nuclear-physics and material experiments, 108° Congresso Nazionale SIF, https://2022.congresso.sif.it/talk/142
[2021] G. Castro et al., The AISHa ion source at INFN-LNS, 19th International Conference on Ion Sources, IOP Publishing doi:10.1088/1742-6596/2244/1/012025
[2018] O. Leonardi et al., A compact DC-break for ECR ion source @ 18 GHZ, Microw Opt Technol Lett. 2018;60:30263029. https://doi.org/10.1002/mop.31421
[2018] L. Celona et al., Commissioning of the AISHa Ion Source at INFN-LNS, AIP Conference Proceedings 2011, 040023 (2018); https://doi.org/10.1063/1.5053297
[2016] L. Celona et al., Design, construction and commissioning of the new superconducting ion source AISHa, in Proc. ECRIS/16, Busan, Korea, Aug. 2016
[2016] F. Noto et al., Mechanical Simulation with Electrical and Dimensional Tests for AISHa Containment Chamber, World Academy of Science, Engineering and Technology International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering Vol:10, No:5.
[2015] Celona et al., A compact multiply charged ion source for hadron therapy facility, 6th International Particle Accelerator Conference IPAC2015, Richmond, VA, USA - JACoW Publishing ISBN: 978-3-95450-168-7 doi:10.18429/JACoW-IPAC2015-WEPWA031
[2015] F. Noto et al., Structural Mechanics Optimization of the AISHa Ion Source, ICCM2015, 14-17th July, Auckland, NZ
[2012] L. Celona et al., Design of the AISHa Ion source for hadrontherapy facilities, Proceedings of ECRIS2012, Sydney, Australia