Spill-to-spill and daily proton energy consistency with a new accelerator control system

The Loma Linda University proton accelerator has had several upgrades installed including synchrotron dipole power supplies and a system for monitoring the beam energy. The consistency of the energy from spill-to-spill has been tested by measuring the depth ionization at the distal edge as a function of time. These measurements were made with a minimally equipped beamline to reduce interference from confounding factors. The consistency of the energy over several months was measured in a treatment room beamline using an ionization chamber based daily quality assurance device. The results showed that the energy of protons delivered from the accelerator (in terms of water equivalent range) was consistent from spill-to-spill to better than ±0.03 mm at 70, 155, and 250 MeV and that the energy check performed each day in the treatment room over a several month period was within ±0.11 mm (±0.06 MeV) at 149 MeV. These results are within the tolerances required for the energy stacking technique