The ISIS synchrotron at the Rutherford Appleton Laboratory in the UK is currently undergoing an RF upgrade. Four h=4, or second harmonic (2RF), cavities have been installed in addition to the existing six h=2, fundamental frequency (1RF), cavities and should be capable of increasing the operating current from 200 to 300µA. Two of the four cavities have been in operation for the last 2 user cycles of 2007 improving trapping losses and increasing operating currents beyond 200µA. The remaining two cavities were commissioned in the spring of 2008. This paper reports on hardware commissioning, beam tests and beam simulation results.
To prevent the electromagnetic (EM) wakefields excitation, protect detectors from damage at a range of installations and facilities including particle accelerators the EM field control is required. Conductive foils or wires providing EM protection and required thermal and mechanical properties are normally used. We suggest novel composite materials with uniquely designed frequency selective conductivity enabling them to overcome the properties of the conventional materials, protect from EM fields and supress undesirable phenomena. Theoretical and experimental investigations are carried out and the conductivity of designed and composite (dual-layer) aluminium/graphene metamaterials as well as graphene and aluminium foils is studied. The EM properties of these materials are compared, and conditions of full and partial electromagnetic transparency are discussed. Results observed allow engineering materials capable of EM field control, instability suppression including those observed in high-intensity particle accelerators and enabling control of an EM field generating media including relativistic charge particle beams.
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 3.5x10 13 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.
The ISIS spallation neutron source has been running successfully for more than 15 years and at 160 kW remains the most powerful source of its kind in the world. With machines due to operate at or near the megawatt level under construction in the United States and Japan and expected to come on line within the next decade, advances in Europe have not progressed at the same rate. A positive decision on the European Spallation Source (ESS) looks unlikely and one is led to consider the feasibility of alternative options. An ISIS upgrade is one such possibility. The current installation of a radio frequency quadrupole (RFQ) in the linac and a dual harmonic RF system in the synchrotron should lead to an increase in intensity of up to 50%, but plans are also under way to increase the beam power to 1 MW with the possibility of going to 4-5 MW in the longer term. The 1 MW option is based on an increase in energy to 3 GeV by means of a second synchrotron using ISIS as a booster. Details of the new ring and studies of the accelerating system are given in this paper. The ring also has the option of accelerating to 8 GeV at reduced frequency and this could be used as a test bed for the nanosecond bunch compression needed for the proton driver for a neutrino factory (NF). The cost of these proposals is relatively modest compared with a completely new facility. In the longer term, a combination of two such rings with a new synchrotron booster (replacing the existing ISIS) would give several options, for example: 4 MW for neutrons, or 2 MW for neutrons plus 2 MW for neutrino/muon studies, or 4 MW for a neutrino facility.
The status of a study for a European Spallation Source (ESS) is reported along with a description of the reference design. The design of the 5 MW, 1.334 GeV machine is dominated by the need to keep beam loss at a low enough level to allow hands on maintenance for most areas. All accelerator sections are designed to be far away from space charge limits. The design allows scraping of the H -Linac beam in all three phase planes (horizontal, vertical and momentum) prior to injection into the two accumulators. Key elements of the R & D programme that will validate the design are identified.
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