Commissioning of the Cryogenic control system for Cryomodules at ESS SRF Linac

Abstract The Cryomodules are critical components in the European Spallation Source (ESS) accelerator, playing a crucial role in connecting spoke cavities to high-beta elliptical cavities in the SRF Linac. These Cryomodules provide the necessary environment for operating, Spoke (Spk) cavities, Medium-Beta (MBL) and High-Beta (HBL) elliptical cavities, which are responsible for accelerating protons from 90 MeV to 2.0 GeV. The Cryomodule houses two double-spoke cavities per Spoke cryomodule and four elliptical cavity packages for MBL and HBL cryomodule, which need to be cooled to 2K to become superconductive and accelerate the beam. There are 13 SPK, 9 MBL and 21 HBL cryomodules to be installed and commissioned on the ESS accelerator for its full scope at 5 MW [1]. The facility will start its first operation in late 2024 with up to the 5 th HBL cryomodule, with an energy reach of 870 MeV and 2 MW of beam power capability. Later installation campaigns, from 2027, will deliver the full scope of 5 MW potential of the facility [2]. An automation control system was developed to control and operate the cryogenic circuits, consisting of temperature, pressure, level, and flow sensors, heaters, and automatic valves connected to a control system based on a Programmable Logic Controller (PLC) integrated into EPICS through the Controls Network [3]. The commissioning of the cryogenic control system involves checking all sensors, actuators, and closed-looping based logic, including temperature curve validation, pressure sensor calibration, and valve initialization, to certify the proper functioning of all components and all special automatic functions including Operator Panel Interface (OPI) connection and deployment. The preparation to operation started in spring of 2023 with SPK-110 and MBL-020. Subsequently, the rest of the cryomodules have been installed and commissioned from August 2023, leading up to a total of 27 units (13 SPK, 9 MBL and 5 HBL), in preparation for the first beam operations scheduled for December 2024. The CM installation campaign for the 2 MW phase ended in July 2024, with an average progress of 2 cryomodules per month. The involved teams devoted to the installation and development of the cryogenic control system coordinated tightly during the installation campaign in order to make equipment available as soon as possible for integration tests after installation [4]. This paper describes the development and commissioning activities involving the control system deployment for starting operations. Future activities will encompass the discussion of integrating this control system with the CMDS master control system, overseeing the simultaneous operation of all cryomodules and the distribution system. Additionally, plans for integrated testing with various other SRF Linac components will be addressed.