Magnetically focused 70 MeV proton minibeams for preclinical experiments combining a tandem accelerator and a 3 GHz...

Area of Science:

• Medical physics
• Particle accelerator technology
• Radiation oncology

Background:

• Radiotherapy is crucial for cancer treatment but causes side effects in healthy tissues.
• Proton minibeam radiotherapy (pMBRT) offers a wider therapeutic window with reduced toxicity.
• Existing accelerators can be modified for pMBRT, potentially avoiding costly new injectors.

Purpose of the Study:

• To develop a preclinical small animal irradiation facility using proton minibeams.
• To adapt a tandem Van de Graaff accelerator and a linear accelerator (linac) for pMBRT.
• To achieve focused 70 MeV proton minibeams (0.1 mm) without an RFQ injector.

Main Methods:

• A 16 MeV proton beam from a tandem accelerator is boosted to 70 MeV by a 3 GHz linear post-accelerator (SCDTL and CCL structures).
• A buncher and quadrupole lenses optimize beam transmission, with a triplet lens focusing the beam to 0.1x0.1 mm².
• Beam dynamics were simulated using TRACE 3D and particle tracking with TRAVEL.

Main Results:

• 49% of protons from the tandem accelerator successfully transmitted through the post-accelerator.
• A mean beam current of up to 19 nA is achievable at the 0.1x0.1 mm² beam focus.
• The study validates the accelerator concept for preclinical pMBRT.

Conclusions:

• Extending existing tandem accelerators with 3 GHz linac structures effectively produces proton minibeams for preclinical irradiation.
• This modular approach meets pMBRT requirements, comparable to commercial injector-RFQ-linac systems.
• The facility's design allows for future upgrades to clinically relevant proton energies (>200 MeV).