The European Spallation Source neutrino super-beam conceptual design report

Abstract

A design study, named $${\text {ESS}}\nu {\text {SB}}$$ ESS ν SB for European Spallation Source neutrino Super Beam, has been carried out during the years 2018–2022 of how the 5 MW proton linear accelerator of the European Spallation Source under construction in Lund, Sweden, can be used to produce the world’s most intense long-baseline neutrino beam. The high beam intensity will allow for measuring the neutrino oscillations near the second oscillation maximum at which the CP violation signal is close to three times higher than at the first maximum, where other experiments measure. This will enable CP violation discovery in the leptonic sector for a wider range of values of the CP violating phase $$\delta _{{\mathrm{CP}}}$$ δ CP and, in particular, a higher precision measurement of $$\delta _{{\mathrm{CP}}}$$ δ CP . The present Conceptual Design Report describes the results of the design study of the required upgrade of the ESS linac, of the accumulator ring used to compress the linac pulses from 2.86 ms to 1.2 μs, and of the target station, where the 5 MW proton beam is used to produce the intense neutrino beam. It also presents the design of the near detector, which is used to monitor the neutrino beam as well as to measure neutrino cross sections, and of the large underground far detector located 360 km from ESS, where the magnitude of the oscillation appearance of $$\nu _{e }$$ ν e from $$\nu _{\mu }$$ ν μ is measured. The physics performance of the $${\text {ESS}}\nu {\text {SB}}$$ ESS ν SB research facility has been evaluated demonstrating that after 10 years of data-taking, leptonic CP violation can be detected with more than 5 standard deviation significance over 70% of the range of values that the CP violation phase angle $$\delta _{{\mathrm{CP}}}$$ δ CP can take and that $$\delta _{{\mathrm{CP}}}$$ δ CP can be measured with a standard error less than 8° irrespective of the measured value of $$\delta _{{\mathrm{CP}}}$$ δ CP . These results demonstrate the uniquely high physics performance of the proposed $${\text {ESS}}\nu {\text {SB}}$$ ESS ν SB research facility.

The ESSnuSB High Intensity Neutrino Super Beam

“…The ESS𝜈SB project has recently published its Conceptual Design Report [5] and proposes a concept of a high intensity neutrino superbeam in Europe which will cover more than 72% of 𝛿 𝐶 𝑃 range and will be able to measure this parameter with 8°precision after 10 years of data taking at 5 MW proton beam power. A new European project called ESS𝜈SB+ has been approved to perform complementary researches on the production of a neutrino superbeam based on muons decay and will offer a broad range of fundamental physics complementary to neutrino physics (proton lifetime, astroparticules,.…”

“…With the publication of the conceptual design report [5], the ESS𝜈SB collaboration has demonstrated the feasibility of a very high intensity neutrino superbeam based on an upgrade of the European Spallation Source Facility. This project has opened a complementary research program to the neutron one and paved the way for future possible interests which could be beyond neutrino physics [6].…”

Future ESS upgrade to Medium Pulse Length – What are the technical challenges for the accelerator and target?

“…It is possible to do modifications in future target wheels as the ESS target will have to be replaced at regular intervals. An alternative target design has been proposed for ESSnuSB [6] using a granular gas cooled target, it will be further studied for application to the ESS target station.…”

“…Figure 2. The ESSnuSB study [6] has looked at possible locations of an accumulation ring on the ESS site. For a medium pulse source, we would strive to find a ring design which is compatible with ESSnuSB.…”

“…H-and H+ bunches can be accelerated in different bunches with e.g. a repetition rate of 28 Hz in the ESS LINAC which is the baseline for ESSnuSB neutrino beam proposal [6]. Separate RF buckets are used for the H-and H+ bunches so beam loading is not an issue.…”