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International audience; The European Spallation Source (ESS) is one of Europe's largest research infrastructures, tobring new insights to the grand challenges of science and innovation in fields as diverse as material and life sciences, energy, environmental technology, cultural heritage,solid-state and fundamental physics by the end of the decade. The collaborative project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden.A 5 MW, long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms and the repetition frequency is 14 Hz (4% duty cycle). The choice of SRF technology is a key element in the development of the ESS linear accelerator (linac).The superconducting linacis composed of one section of spoke cavity cryomodules(352.21 MHz) and two sections of elliptical cavity cryomodules (704.42 MHz). These cryomodules contain niobium SRF cavities operating at 2 K, cooled by the accelerator cryoplantthrough the cryogenic distribution system.This paper presents the superconducting RF cavity and cryomodule cryogenic processes, which are developed for the technology demonstrators and to be ultimately integrated for the ESS tunnel operation.

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 pla...

International audience; The European Spallation Source project aims at being the most powerful neutron source feeding multidisplinary researches. Based on superconducting radiofrequency technologies, the linear accelerator will operate for the first time a 56 meter long section of niobium double Spoke cavities. Paired in 13 cryomodules, each cavity will generate an accelerating pulsed field of 9MV/m. A prototype cryomodule housing two superconducting Spoke cavities and their RF power couplers is now being fabricated and assembled. It provides the cryogenic environment for their operation in a 2K saturated superfluid helium bath: a 50 K thermal shield, a cold magnetic shield, and integrates all the interfaces necessary to be operational within the linac machine. This prototype will be tested in 2016 at IPNO site and then at Uppsala university FREIA facilities. A valve box was designed to take into account the specific features of this prototype cryomodule and of both test sites. This valve box is also considered as a prototype of the cryogenic distribution of the linac Spoke section. This element will then be used for the tests of the series cryomodules.

The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. This paper introduces the thermo-mechanical design and expected operation of the ESS spoke cavity cryomodules. These cryomodules contain two double spoke bulk Niobium cavities operating at 2 K and at a frequency of 352.21 MHz. The superconducting section of the Spoke Linac accelerates the beam from 90 MeV to 220 MeV. A Spoke Cavity Cryomodule Technology Demonstrator will be built and tested in order to validate the ESS series production.

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.

The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. The superconducting section of the Linac accelerates the beam from 80 MeV to 2.0 GeV. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. These cryomodules contain four elliptical Niobium cavities operating at 2 K and at a frequency of 704.42 MHz. This paper introduces the thermo-mechanical design, the prototyping and the expected operation of the ESS elliptical cavity cryomodules. An Elliptical Cavity Cryomodule Technology Demonstrator (ECCTD) will be built and tested in order to validate the ESS series production.

The cryogenic system at the Meson Detector Building (MDB) has now supported over four years of testing of fully assembled SRF cavities. The Horizontal Test Stand (HTS) has tested single, fully dressed 1.3 GHz and 3.9 GHz cavities at 2 K as final qualification prior to their installation into accelerator-ready cryomodules. The MDB cryogenic system has been expanded to support an additional cavity test area, the Spoke Resonator Test (SRT) area, for 325 MHz single-spoke resonators. The SRT area currently supports 4.5 K operations for research and development of the spoke cavities with tuner and coupler. The test area addition required the design and installation of a new cryogenic transfer line extension to reach this second test area and to allow for independent operations of either cavity test system. The cryogenic performance and operational experiences of both cavity test areas, operating individually or simultaneously, will be discussed. The general reliability of operating the closed, subatmospheric helium system free of contaminants will be discussed. Future plans for the MDB test area include lowering the SRT temperature to 2 K and adding an additional Horizontal Test Stand (HTS-2).

Superfluid helium Transport phenomena can be described using the two-fluid Landau-Khalatnikov model and the Gorter-Mellink mutual friction. We have continued our previous work devoted to the formulation of a system of equations to describe the heat and mass transport in superfluid helium, and its numerical solution. The main advantage of the approach proposed is that it yields explicitly pressure and temperature as system variables, which can be used to stabilize the numerical solution. In the paper we describe the numerical implementation of the method proposed, and first results on simple test cases that prove the stability and convergence of the procedure.

MuCool Test Area (MTA) is a complex of buildings at Fermi National Accelerator Laboratory, which are dedicated to operate components of a cooling cell to be used for Muon Collider and Neutrino Factory R&D. The long-term goal of this facility is to test ionization cooling principles by operating a 25-liter liquid hydrogen (LH{sub 2}) absorber embedded in a 5 Tesla superconducting solenoid magnet. The MTA solenoid magnet will be used with RF cavities exposed to a high intensity beam. Cryogens used at the MTA include LHe, LN{sub 2} and LH{sub 2}. The latter dictates stringent system design for hazardous locations. The cryogenic plant is a modified Tevatron refrigerator based on the Claude cycle. The implementation of an in-house refrigerator system and two 300 kilowatt screw compressors is under development. The helium refrigeration capacity is 500 W at 14 K. In addition the MTA solenoid magnet will be batch-filled with LHe every 2 days using the same cryo-plant. This paper reviews cryogenic systems used to support the Muon Collider and Neutrino Factory R&D programs and emphasizes the feasibility of handling cryogenic equipment at MTA in a safe manner.

We describe the status of our effort to realize a first neutrino factory and the progress made in understanding the problems associated with the collection and cooling of muons towards that end. We summarize the physics that can be done with neutrino factories as well as with intense cold beams of muons. The physics potential of muon colliders is reviewed, both as Higgs Factories and compact high energy lepton colliders. The status and timescale of our research and development effort is reviewed as well as the latest designs in cooling channels including the promise of ring coolers in achieving longitudinal and transverse cooling simultaneously. We detail the efforts being made to mount an international cooling experiment to demonstrate the ionization cooling of muons., Comment: 112 pages, Large report

A stored-muon-beam neutrino factory may require transverse ionization cooling of the muon beam. We describe recent progress in research and development on energy absorbers for muon-beam cooling carried out by a collaboration of university and laboratory groups., Comment: 7 pages, 1 figure, presented at the 3rd International Workshop on Neutrino Factory Based on Muon Storage Rings (NuFACT'01), May 24-30, 2001, Tsukuba, Japan