- Coordinator: Mamad Eshraqi (ESS, Sweden)
- Co-coordinator: Roger Ruber (University of Uppsala, Sweden)
- Team members:
Providing a proton beam of 5 MW with short pulses to the neutrino target requires the ESS linac, Figure 1, to be upgraded to deliver a total of 10 MW average beam power. The additional 5 MW of beam power has H⁻ as the accelerated species to enhance the injection into the accumulator ring using charge exchange injection scheme.
The main deliverable of this Work Package is the CDR chapters for the ESS linac modifications, including the cost and safety issues and, most importantly, the interactions with the generation of spallation neutrons which is the main purpose of the ESS. This WP will study the integration, installation and operation of an H– ion source, Figure 2, and the acceleration of H– in the linac to the higher energy of 2.5 GeV.
Increasing the linac energy to 2.5 GeV from the 2.0 GeV requires adding 8 additional cryomodules of the High beta type downstream of the high beta linac, Figure 3. Increases energy of the H- beam reduces the space charge tune shift in the accumulator ring, and reduces the average current in the linac.
Amongst the items to be studied for the H⁻ beam transport, this work-package looks in particular on the effects of beam losses, and of the requirements on the RF power sources and the upgrade of the cooling system to handle the increase of the RF power of the linac by injecting and accelerating H– pulses between the ordinary H+ pulses, thereby increasing the pulse frequency to 28 Hz, Figure 4.
Other pulse train sequences are being considered that could raise the frequency to 70 Hz by inserting 4 lower power H– pulses between successive H+ pulses. During the course of the Design Study the ESS linac will be built up. The study will have, as an early priority task, the identification of minor modifications that can be made during the construction phase of the linac that will minimise the disturbance and cost of the later upgrade of the power and the enabling of H– acceleration in extra pulses. Costing aspects will also be addressed.