ESS Spoke Insertable Beam Stop

The commissioning of the proton accelerator for the European Spallation Source (ESS) is in progress in Lund (Sweden). This document deals with a key component for the commissioning of the superconducting section of the ESS linac: the Insertable Beam Stop (IBS) in the first Spoke (SPK) section. The IBS will stop the high power proton beam and avoid beam losses in the superconducting cavities during commissioning and tuning of the ESS proton accelerator in 2024, while allowing hands-on maintenance of the linac components. The proton beam energy is the [40, 100] MeV range, the maximum proton current is 65 mA and the maximum proton pulse duration is 50E-6 s. The device will be moved in and out of the beam pipe by means of a pneumatic actuator. The device is water cooled. The temperature on the entrance surface will be monitor with thermocouples. In general, the materials are subject to the guidelines by the ESS Vacuum team; cleanliness is a must to ensure an UHV integrity as well as to minimize gas loads. ISO5 cleanliness must be demonstrated [1]. The retracted device occupies a cylindrical envelope with diameter = 23 cm and height = 100 cm. The weight of the device is approximately 50 kg. The recommended stroke distance is 150 mm, with adjustable mechanical endstops and a rod-locking mechanism as e.g. the ESS DTL2 Faraday cup [2].