Xilong Wang

Status of the ESS cryogenic system

The European Spallation Source (ESS) is a neutron science facility funded by a collaboration of 17 European countries currently under design and construction in Lund, Sweden. The centerpiece of ESS is a 2.5 GeV proton linac utilizing superconducting RF cavities operating at 2 K. In addition to cooling the SRF cavities, cryogenics is also used at ESS in the liquid hydrogen moderators surrounding the target. ESS also uses both liquid helium and liquid nitrogen in a number of the planned neutron instruments. There is also a significant cryogenic installation associated with the site acceptance testing of the ESS cryomodules. The ESS cryogenic system consists of 3 separate helium refrigeration/liquefaction plants supplying the accelerator, target moderators and instruments. An extensive cryogenic distribution system connects the accelerator cryoplant with the cryomodules. This paper describes the preliminary design of the ESS cryogenic system including the expected heat loads. Challenges associated with the required high reliability and turn-down capability will also be discussed. A unique feature of ESS is its commitment to sustainability and energy recovery. A conceptual design for recovering waste heat from the helium compressors for use in the Lund district heating system will also be described.

ESS Cryogenic System Process Design

The European Spallation Source (ESS) is a neutron-scattering facility funded and supported in collaboration with 17 European countries in Lund, Sweden. Cryogenic cooling at ESS is vital particularly for the linear accelerator, the hydrogen target moderators, a test stand for cryomodules, the neutron instruments and their sample environments. The paper will focus on specific process design criteria, design decisions and their motivations for the helium cryoplants and auxiliary equipment. Key issues for all plants and their process concepts are energy efficiency, reliability, smooth turn-down behaviour and flexibility. The accelerator cryoplant (ACCP) and the target moderator cryoplant (TMCP) in particular need to be prepared for a range of refrigeration capacities due to the intrinsic uncertainties regarding heat load definitions. Furthermore the paper addresses questions regarding process arrangement, 2 K cooling methodology, LN2 precooling, helium storage, helium purification and heat recovery.

The cryomodule test stand at the European Spallation Source

The European Spallation Source (ESS) is an intergovernmental project building a multidisciplinary research laboratory based upon the worlds most powerful neutron source to be built in Lund, Sweden. The ESS will use a linear accelerator which will deliver protons with 5 MW of power to the target at 2.5 GeV with a nominal current of 50 mA. The superconducting part of the linac consists of over 150 niobium cavities cooled with superfluid helium at 2 K. A dedicated cryoplant will supply the cryomodules with single phase helium through an external cryogenic transfer line. The elliptical cavity cryomodules will undergo their site acceptance tests at the ESS cryomodule test stand in Lund. This test stand will use a 4.5 K cryoplant and warm sub-atmospheric compression to supply the 2 K helium. We will show the requirements for the test stand, a layout proposal and discuss the factors determining the required cryogenic capacity, test sequence and schedule.

ESS accelerator cryogenic plant

The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration at Lund, Sweden. The ESS accelerator will deliver protons with 5 MW of power to the target at 2.5 GeV, with a nominal current of 50 mA. The superconducting section of the ESS accelerator consists of a total of 208 SRF cavities in cryomodules (CMs) cooled with superfluid helium to 2 K. The CM contains one thermal radiation shield operating from 40 to 50 K. Additionally, 4.5-K gas helium is used to provide forced cooling to the fundamental power couplers for the cavities. The cryogenic cooling for these CMs is provided by one cryogenic plant connected to CMs via a cryogenic distribution line. This article describes the requirements and preliminary design decisions for the ESS accelerator cryoplant. The expected capacity, temperature levels and operating modes are given. Design choices to address important issues of turn-down capability, high availability, and timely restart after plant trips are discussed. Procurement options and schedules are described.

ESS Accelerator Cryoplant Process Design

The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration in Lund, Sweden. The ESS accelerator will deliver protons with 5 MW of power to the target at 2.0 GeV, with a nominal current of 62.5 mA. The superconducting part of the accelerator is about 300 meters long and contains 43 cryomodules. The ESS accelerator cryoplant (ACCP) will provide the cooling for the cryomodules and the cryogenic distribution system that delivers the helium to the cryomodules. The ACCP will cover three cryogenic circuits: Bath cooling for the cavities at 2 K, the thermal shields at around 40 K and the power couplers thermalisation with 4.5 K forced helium cooling. The open competitive bid for the ACCP took place in 2014 with Linde Kryotechnik AG being selected as the vendor. This paper summarizes the progress in the ACCP development and engineering. Current status including final cooling requirements, preliminary process design, system configuration, machine concept and layout, main parameters and features, solution for the acceptance tests, exergy analysis and efficiency is presented.