Dean Adams

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.

Injection studies on the isis synchrotron

The ISIS Facility at the Rutherford Appleton Laboratory in the UK produces intense neutron and muon beams for condensed matter research. It is based on a 50 Hz proton synchrotron which, once the commissioning of a new dual harmonic RF system is complete, will accelerate about 3.5 x 1013 protons per pulse from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. The multi-turn charge-exchange injection process strongly affects transverse beam distributions, space charge forces, beam loss and therefore operational intensity. The evolution of longitudinal distributions and subsequent trapping efficiency is also intimately linked with injection. Optimising injection is therefore a key consideration for present and future upgrades. Work is now under way looking at this process in more detail, and relates closely to other transverse space charge studies on the ring. This paper presents work including: space charge simulations of the present machine and comparison with observations; assessment of related loss mechanisms; and study of optimal painting schemes. Plans and preparations for more detailed experimental work are also summarised.

Studies of space charge loss mechanisms on the isis synchrotron

The ISIS Facility is the pulsed neutron and muon source based at the Rutherford Appleton Laboratory in the UK. Operation centres on the 50 Hz synchrotron, which accelerates ~3times1013 protons per pulse from 70 to 800 MeV, providing a mean power of about 0.2 MW. As commissioning of a second harmonic RF system is completed, it is expected that the main loss mechanisms will be related to transverse space charge forces, which are particularly strong during the multi-turn injection and trapping processes. Here, we describe progress in ongoing studies to understand more about what drives loss and thus limits intensity. Results from simulations and application of relevant theory are presented, concentrating on the effects thought most important for the ISIS ring. Progress on work looking at the half integer resonance and image effects in the rectangular vacuum vessels is reported, along with work for experimental studies.

First Results from the use of 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 H-linac H-linac and an 800 MeV, 50 Hz, rapid cycling, proton synchrotron. The synchrotron beam intensity corresponds to a mean current of 200 μA. 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 of raising the operating current to 300 μA. This paper reports on the hardware commissioning and the first beam tests.