Upgrade Possibility of the ESS Linac for the ESSnuSB Project

The European Spallation Source (ESS), currently under construction in Lund, Sweden, is the world’s most powerful neutron spallation source, with an average power of 5 MW at 2.0 GeV. The linac accelerates a proton beam of 62.5 mA peak current at 4 % duty cycle (2.86 ms at 14 Hz). The ESS neutrino Super Beam Project (ESSnuSB) proposes to utilise this powerful accelerator as a proton driver for a neutrino beam that will be sent to a large underground Cherenkov detector in Garpenberg, mid-Sweden. By adding a second H⁻ beam, interleaved with the proton beam, the duty cycle will be increased to 8 % and the average power to 10 MW. In this paper we discuss the modifications of the ESS linac required to reach an additional 5 MW beam power for neutrino production in parallel to spallation neutron production

On Liouvillian High Power Beam Accumulation

International audienceIt is acknowledged that the injection of high power proton beams into synchrotrons must be done using stripping injection of H⁻ beams which are accelerated by an injector, as done in many facilities worldwide such as ISIS, JPARC, SNS and CERN. However, this technique is not necessarily the only way of accumulation and in some cases might not represent the best choice. For example in the case of the ESSnuSB Accumulator Ring, accelerating the protons injecting them to the ring could represent savings in capital cost, reduced risk of losses in the linac and transfer lines and simplification to the overall project. This work presents the development of a method allowing to optimize the 4D Liouvillian accumulation of high-power proton and heavy ion beams and finishes with a discussion on the pros and cons of proton injection compared to more traditional H⁻ stripping injection method

ESSν\nuSB Linac Design and Beam Dynamics

The ESS neutrino superbeam project is being studied as an upgrade to the European Spallation Source. This would entail the addition of an $\mathrm{H^-}$ source to the existing beamline to send $\mathrm{H^-}$ pulses in between proton pulses, effectively doubling the beam power from five to ten megawatts. An obstacle to smooth operation is the intra-beam stripping of $\mathrm{H^-}$ within bunches; preliminary beam transport simulations are performed to quantify the magnitude of such losses. Recent design work is also reviewed, including the added cavities for increasing beam energy from 2 to 2.5 GeV and favored bunch-pulsing schemes

Evaluation of Klystron Modulator Performance in Interleaved Pulsing Schemes for the ESS Neutrino Super Beam Project

It has been proposed that the relatively low duty cycle of the European Spallation Source (ESS) linac allows acceleration of additional mathbfH^- ion pulses interleaved with the baseline proton pulses, representing a unique opportunity to construct a neutrino super beam (ESSnuSB) facility of unparalleled luminosity. Coupled with a distant Cherenkov detector, it is believed that evidence of CP violations in leptons could be obtained, representing a significant step towards understanding the matter/antimatter asymmetry. In this paper, several such interleaved pulsing schemes are considered from the perspective of the klystron modulators and the RF power system in investigating the possibility to realize the ESSnuSB. Conserving the required output RF energy, these pulsing schemes vary in terms of 1) number of added H- ion pulses per baseline cycle, 2) pulse amplitude and 3) pulse length. Each prospective pulsing scheme offers unique advantages while differently impacting klystron modulator performance. Whereas the ESS linac baseline design requires 33 klystron modulators (rated for pulse amplitude 115kV/4x25A, pulse length 3.5ms and pulse repetition rate 14Hz; each modulator powering 4 parallel klystrons rated 1.6MWpk at 704MHz), the proposed upgrade requires doubling the baseline linac average output power and thus either doubling the capacity of existing modulators or the procurement of additional modulator systems. In order to evaluate and compare the merit of these solutions from a system perspective, a mathematical framework connecting the attributes of the proposed pulsing schemes to the power transfer curves of the klystrons and subsequently to the performance of the klystron modulators is developed. Finally, a preferred solution is selected and the impact on grid-to-RF efficiency, modulator average input power quality, total upgrade cost and required additional system size is assessed

Radiation transport calculations for the European Spallation Source accelerator environment

A central component of the European Spallation Source is the high-power proton accelerator. The accelerator aims in the future to provide 2 GeV protons to a rotating tungsten target for the production of neutrons at 5 MW of average beam power for neutron scattering studies. Extensive shielding surrounds the accelerator, in order to provide sufficient safety for the public and workers against radiation produced along it's length. This largely comprises several meters of soil, called the berm, and concrete structures located around the accelerator tunnel. However, due to the need for access to the accelerator, during maintenance and connections for other utilities, the shielding contains a number of penetrations which leads to weaknesses in localized areas. For these reasons, shielding design of such a facility must take care to address issues related to both the deep-penetration of the radiation through thick shields, while at the same time accounting for the streaming nature of the radiation through ducts and chicanes. In addition, radiation produced from activated components of the accelerator also poses risks for workers and public. For example, activated magnets will need maintenance and workers may need to access areas where activated water circulates. Thus, activation analyses are also needed in combination with the prompt-dose rate estimates for a complete analysis. In this summary, we present the results of a series of such studies carried out on various components around the ESS accelerator.Comment: 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD 2022) meetin

The ESSννSB project

International audienceThe ESSνSB project aims to produce a neutrino beam of unique intensity for a long-baseline oscillation measurement of CP-violation in the leptonic sector. The project, supported within the H2020 framework programme of the European Union, is currently in a conceptual design study phase, and work is ongoing within the project to develop viable solutions for the upgrade of the linear accelerator of the European Spallation Source (ESS), for the associated ring accumulator and the high-power target stations, as well as to establish solutions for the near and far detectors. The unique strength of the project lies in the capability to produce a neutrino beam that is intense enough to place the far detector at the second oscillation maximum. Such a placement will reduce the sensitivity of the experiment to systematic errors, which, due to the recently established value of the neutrino mixing angle θ13, is now known to limit the measurement precision at the first oscillation maximum. In this paper we outline the basic components of the project and discuss the status of the ongoing conceptual design study