Papers by Julien Branlard
… , USA, pp719-721, 2006
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Physical review accelerators and beams, Jan 4, 2023
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Frontiers in Physics, Jun 21, 2023
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15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems (ICALEPCS'15), Melbourne, Australia, 17-23 October 2015, Dec 1, 2015
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12th International Particle Accelerator Conference (IPAC'21), Campinas, SP, Brazil, 24-28 May 2021, Aug 1, 2021
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29\textsuperscript{th} Linear Accelerator Conf. (LINAC'18), Beijing, China, 16-21 September 2018, Mar 9, 2019
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29\textsuperscript{th} Linear Accelerator Conf. (LINAC'18), Beijing, China, 16-21 September 2018, 2019
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This document presents a compact module of an RF frequency divider, working with 1.3 GHz input si... more This document presents a compact module of an RF frequency divider, working with 1.3 GHz input signal, producing 216 MHz and 10 MHz output signals, designed for use in RF phase reference distribution system in European XFEL facility. Presented module is small, relatively simple in production and easy to use, including simple synchronization with other devices. For the European XFEL more than 70 modules have been manufactured, tested and installed in the accelerator, and their robustness and quality proved. In this article principle of operation, block diagram, module photos and test results are presented.
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IEEE Transactions on Nuclear Science, Jun 1, 2017
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IEEE Transactions on Nuclear Science, Jun 1, 2015
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arXiv (Cornell University), Sep 28, 2022
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OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 26, 2011
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After the initial commissioning of the available 25 radio frequency (RF) stations of the European... more After the initial commissioning of the available 25 radio frequency (RF) stations of the European XFEL (RF gun, A1, AH1 and stations A2 through A23) a maximum electron beam energy of 14.5 GeV was achieved, 3 GeV short of the design energy of 17.5 GeV. In order to tackle this problem, the Maximum Gradient Task Force (MGTF) was formed. In the scope of the work of the MGTF, RF stations A6 through A25 (linac L3) were systematically investigated and voltage-limiting factors of the SRF accelerating modules and their RF distribution system were identified and improved. As a result, the design electron beam energy was exceeded at 17.6 GeV on the 18.7.2018. Beside this an overview over the regular RF operation at the European XFEL is given.
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In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile... more In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 10⁻⁴ amplitude precision. Advances are through improved field detection methods and massive usage of digital signal procession on very powerful field programmable gate arrays (FPGAs). The question rise, what can be achieved in the next 10 years? In this talk, a review is given of existing systems and strategies, current stability limitations of RF control system and new technologies with the potential to achieve attosecond resolutions.
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The European X-ray free electron laser requires a high-precision control of accelerating fields t... more The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.
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Nature Photonics, 2020
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2014 19th IEEE-NPSS Real Time Conference, 2014
The paper describes achievements in LLRF based tests preparation for superconducting cryo-modules... more The paper describes achievements in LLRF based tests preparation for superconducting cryo-modules evaluation for European X-ray Free Electron Laser. The software for automatic cryo-modules characterization at the Accelerator Module Test Facility (AMTF) will be presented. In order to identify fundamental working parameters of the eight TESLA cavities cryomodules the scenario of several tests sequence has been proposed and implemented in AMTF. Main parameters like: cavities quenching levels verification, cavities Pi modes identification, slow and fast frequency tuners performance, fundamental power coupler performance, etc are evaluated. Basing on achieved data the decision about module acceptance for work in the linac is done. In this solution the MTCA.4 based LLRF system is used to control and verify cryo-string performance. Middle layer client servers implemented in this environment are responsible for providing tests initial conditions, testing and results archiving in the dedicated data base. Results of described tests are not only vital for module acceptance but are also important for future LLRF system set-up and configuration concerning module work in the accelerator tunnel.
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In summer 2011, we performed the first test of continuous wave and long pulse operation of the XF... more In summer 2011, we performed the first test of continuous wave and long pulse operation of the XFEL prototype cryomodule [1], which originally has been designed for a short pulse operation. In April and June 2012, the second test took place, with the next prototype. For that test, cooling in the cryomodule was improved and new LLRF system has been implemented. In this contribution we discuss results of the second test of these new types of operation, which can in the future extend flexibility in the time structure of the electron and photon beams of the European XFEL facility.
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Papers by Julien Branlard