Design of a helium ion linear accelerator for astatine production

Astatine 211 is one of the most effective theragnostics isotopes for targeted alpha therapy of cancer. Connected to a carrier that links to cancer cells when injected in a patient, this powerful alpha emitter can selectively destroy cancerous cells. Accelerator production of 211At requires sending beams of fully stripped helium ions (alpha particles) on a bismuth target at the energy of 7.1 Me/u. To obtain sufficient doses for hospital production of 211At, currents higher than what provided by cyclotrons are required. For this type of particle and intensities, cyclotrons are limited by the large amount of beam loss and activation in the extraction region, while linacs are virtually loss-free and much better suited for At production. The design of an innovative linac for At production is presented, based on an alpha particle source of new design, a compact Radio Frequency Quadrupole, and a Quasi-Alvarez Drift Tube Linac (QA-DTL) going up to the final energy. Thanks to the QA-DTL low injection energy and compact design, the linac is only 10 meters in length. The overall design is presented, together with detailed RF and beam optics simulations.