Papers by Christine Darve
Fundamental physics and accelerator science in developing countries
Bulletin of the American Physical Society, Mar 4, 2020
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 2008
Transport phenomena in superfluid helium can be described using the two-fluid Landau-Khalatnikov ... more Transport phenomena in superfluid helium can be described using the two-fluid Landau-Khalatnikov model and the Gorter-Mellink mutual friction. Here we discuss a mathematical formulation of the two-fluid model that uses macroscopic conservation balances of mass, momentum and energy of each species, and assumes local thermodynamic equilibrium. A particularity of this model is that it describes the state of He II as well as that of each of the two-fluid components in terms of pressure p and temperature T, which is convenient for stable numerical solution. The equations of the model form a system of partial differential equations (PDE) that can be written in matrix form for convenience. On this base, a three-dimensional numerical model using a complete and consistent, while still practical, system of PDEs was developed. In the form described, the PDE can be solved using threedimensional Lagrangian finite element in space supplemented by a Beam-Warming time-2 marching algorithm. Once validated, this solver will allow to simulate He II thermal counterflow applied to arbitrary geometry.
arXiv (Cornell University), Aug 17, 2001
A program is underway to develop liquid-hydrogen energy absorbers for ionization cooling of muon-... more A program is underway to develop liquid-hydrogen energy absorbers for ionization cooling of muon-beam transverse emittance. Minimization of multiple-scatteringinduced beam heating requires thin windows. The first window prototype has been destructively tested, validating the finite-element-analysis model and the design approach.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 1, 2010
The low- magnet systems are located in the LHC insertion regions around the four interaction poi... more The low- magnet systems are located in the LHC insertion regions around the four interaction points. They are the key elements in the beams focusing/defocusing process and will allow proton collisions at a luminosity of up to 10 34 cm -2 s -1 . Large radiation dose deposited at the proximity of the beam collisions dictate stringent requirements for the design and operation of the systems. The hardware commissioning phase of the LHC was completed in the winter of 2010 and permitted to validate this system safe operation. This paper presents the analysis used to qualify and quantify the safe operation of the low- magnet systems in the Large Hadron Collider (LHC) for the first years of operation.
IEEE Transactions on Applied Superconductivity, Jun 1, 2009
Convection-type LH2 absorber R&D for muon ionization cooling
Nuclear Instruments and Methods in Physics Research, May 1, 2003
A feasibility study on liquid hydrogen (LH2) absorbers for muon ionization cooling is reported. I... more A feasibility study on liquid hydrogen (LH2) absorbers for muon ionization cooling is reported. In muon ionization cooling, an LH2 absorber is required to have a high cooling power greater than 100W to cool heat deposited by muons passing through. That heat in LH2 can be removed at either external or internal heat exchangers, which are cooled by cold helium
arXiv (Cornell University), Feb 27, 2023
The African School of Fundamental Physics and Applications, also known as the African School of P... more The African School of Fundamental Physics and Applications, also known as the African School of Physics (ASP), was initiated in 2010, as a three-week biennial event, to offer additional training in fundamental and applied physics to African students with a minimum of three-year university education. Since its inception, ASP has grown to be much more than a school. ASP has become a series of activities and events with directed ethos towards physics as an engine for development in Africa. We report on the seven African School of Physics, ASP2022, organized at Nelson Mandela University, on November 28 to December 8, 2022. ASP2022 included programs for university students, high school teachers and high school pupils.
arXiv (Cornell University), Apr 4, 2022
The African School of Fundamental Physics and Applications, also known as the African School of P... more The African School of Fundamental Physics and Applications, also known as the African School of Physics (ASP), was initiated in 2010, as a three-week biennial event, to offer additional training in fundamental and applied physics to African students with a minimum of three-year university education. Since its inception, ASP has grown to be much more than a school. ASP has become a series of activities and events with directed ethos towards physics as an engine for development in Africa. One such activity of ASP is the African Conference on Fundamental and Applied Physics (ACP). The first edition of ACP took place during the 2018 edition of ASP at the University of Namibia in Windhoek. In this paper, we report on the second edition of ACP, organized on March 7-11, 2022, as a virtual event.
The European Spallation Source, ESS, is under construction in Lund since 2014. While the installa... more The European Spallation Source, ESS, is under construction in Lund since 2014. While the installation of the source and the normal conducting part will start in this autumn, the production and testing of cryomodules and cavities for the superconducting accelerator is in full swing at the partner laboratories. The spoke cavities and cryomodules will be provided by IPN Orsay and the testing of those modules will take place at Uppsala University. Prototyping and assembly of the elliptical cryomodules series is occurring at CEA Saclay, and the modules will be tested at a new test stand at ESS. The fabrication and test of the medium beta cavities is provided by INFN Milan and STFC Daresbury for the high beta cavities respectively. An overview of the current activities and test results will be presented in this talk.
The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and... more The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy of 2 GeV. The last Linac optimization, called Optimus+ [1], has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium beta elliptical cavity prototypes. We describe the cavity preparation procedure from buffer chemical polishing to vertical test. Finally, magnetic probes (Fluxgate) were installed on the cavity to determine magnetic field background during vertical test. The latest vertical test results showed that the cavity design performance is beyond requirements. (Less)
The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at ... more The first ESS prototype cryomodule with medium beta cavities named M-ECCTD is being assembled at CEA Saclay. The Q curves of the 4 cavities mounted inside the cryomodule are presented, and the four power couplers have been conditioned at high power before their assembly onto the cavity string. Completion of the M-ECCTD assembly outside clean room is in progress as well as the finalization of the RF power test stand preparation. RF power tests of the M-ECCTD will be performed during summer 2017. CEA is preparing the production of the ESS medium and high beta cryomodules of the series before the test of the M-ECCTD and the contracts for the procurement of the most critical components have already been signed
In the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a ... more In the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a superconducting section is being developed. This accelerator owns two kinds of cavities called “medium beta cavity” (β=0.67) and “high beta cavity” (β= 0.86). These cavities are equipped with RF power couplers whose main characteristics are: fundamental frequency: 704.42MHz, peak RF power: 1.1MW, repetition rate: 14Hz, RF pulse width>3.1ms. These couplers are common to the two cavities. The CEA Saclay is responsible for the design, the manufacture, the preparation and the conditioning of the couplers used for the Elliptical Cavities Cryomodule Technological Demonstrators (ECCTD). This work is performed in collaboration with ESS and the IPNO. This paper describes the coupler architecture, its different components, the main characteristics and the specific features of its elements (RF performance, dissipated power, cooling, coupler box test for the conditioning). The status of the manuf...
The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and... more The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+[1], has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively [2]. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.
The sixth edition of the African School of Fundamental and Applied Physics (ASP) was planned for ... more The sixth edition of the African School of Fundamental and Applied Physics (ASP) was planned for Morocco in July 2020 and was referred to as ASP2020. Preparations were at an advanced stage when ASP2020 was postponed because of the COVID-19 pandemic. The three-week event was restructured into two activities in 2021 -- an online event on July 19-30, 2021 and a hybrid event on December 12-18, 2021 -- and was renamed ASP2021. At the beginning of the COVID-19 pandemic, an online lecture series was integrated into the ASP activities. The ASP mentorship program, which consists of online engagements between lecturers and assigned mentees, continued in this way. ASP alumni studied one year of COVID-19 data of ten African countries to offer insights into pandemic containment measures. In this note, we report on ASP activities since the last in-person edition of ASP in 2018 in Namibia.
Progress in the Elliptical Cavities and Cryomodule Demonstrators for the ESS LINAC
The European Spallation Source (ESS) accelerator is a large superconducting linac under construct... more The European Spallation Source (ESS) accelerator is a large superconducting linac under construction in Lund, Sweden. A collaboration between CEA Saclay, IPN Orsay and ESS-AB is established to design the elliptical cavities cryomodule of the linac. It is foreseen to build and test two cryomodule demonstrators within the next two years. We present the design evolution and the fabrication status of the cryomodule components housing four cavities. The latest test results of two prototype cavities are shown. The cryomodule assembly process and the ongoing testing infrastructures at CEA Saclay are also described.
Journal of Physics: Conference Series, Sep 1, 2018
The TIARA (Test Infrastructure and Accelerator Research Area) project funded by the European Unio... more The TIARA (Test Infrastructure and Accelerator Research Area) project funded by the European Union 7th framework programme made a survey of provision of education and training in accelerator science in Europe. This survey highlighted the need for more training opportunities targeting undergraduate-level students. This need is now being addressed by the European Union H2020 project ARIES (Accelerator Research and Innovation for European Science and Society) via the preparation of a Massive Open Online Course (MOOC) on particle accelerator science and engineering. We present here the current status of this project, the main elements of the syllabus, how it will be delivered, and the schedule for providing the course.
Journal of Instrumentation, 2017
This paper describes the design and construction of the MicroBooNE liquid argon time projection c... more This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported.
AIP Conference Proceedings, 2004
As part of Fermilab's study of a Very Large Hadron Collider (VLHC), a water-cooled photon stop wa... more As part of Fermilab's study of a Very Large Hadron Collider (VLHC), a water-cooled photon stop was proposed as a device to intercept the synchrotron radiation emitted by the high-energy proton beams in the high-field superconducting magnets with minimal plugcooling power. Photon stops are radiation absorbers operating at room temperature that protrude into the beam tube at the end of each bending magnet to scrape the synchrotron light emitted by the beam one magnet up-stream. Among the technological challenges regarding photon stops is their cryo-design. The photon stop is water-cooled and operates in a cryogenic environment. A careful cryo-design is therefore essential to enable operation at minimum heat transfer between the room temperature sections and the cryogenic parts. A photon stop cryo-design was developed and a prototype was built. This paper presents the results of the cryogenic experiments conducted on the first VLHC photon-stop prototype.
AIP Conference Proceedings, 2010
The Large Hadron Collider (LHC) now under commissioning at CERN is a 26.7 km collider based on se... more The Large Hadron Collider (LHC) now under commissioning at CERN is a 26.7 km collider based on several thousand high-field superconducting magnets, the majority of which operating in superfluid helium below 2 K and some isolated magnets operating in normal helium at 4.5 K. Four superconducting links (DSLs) of about 76 m in length and one of about 517 m in length, were designed, constructed and installed over a three year period. Their purpose is to transport current over long distances whenever underground LHC space constraints prevents to put power converters, current feed boxes and magnets in each others' proximity. The four 76 m long DSLs transport current between current feed boxes and several of the isolated magnets, whereas the 517 m long DSL transports current between two current feed boxes. The links are comprised of cryogenic, vacuum-insulated, transfer lines housing one or more superconducting cables. The operating temperatures are about 5 K for the DSL part that houses the cable and about 60 K for the heat shield. Their commissioning and performance results at first operational experience in the beginning of 2008 are discussed.
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Papers by Christine Darve