Progress on dual harmonic acceleration on the isis synchrotron

The ISIS facility at the Rutherford Appleton Laboratory in the UK is currently the most intense pulsed, spallation, neutron source. The accelerator consists of a 70 MeV H^- linac and an 800 MeV, 50 Hz, rapid cycling proton synchrotron. The synchrotron beam intensity is typically 2.25 times 10¹³ protons per pulse, corresponding to a mean current of 180 muA. The synchrotron beam is accelerated using six, ferrite loaded, RF cavities with harmonic number 2. Four additional, harmonic number 4, cavities have been installed to increase the beam bunching factor with the potential to raise the operating current to 300 muA. The dual harmonic system has now been used operationally for the first time, running reliably throughout the last ISIS user cycle of 2006. This paper reports on the hardware commissioning, beam tests and improved operational results obtained so far with dual harmonic acceleration.