Beam Profile Monitor for PAL-XFEL

Beam Profile Monitor for PAL-XFEL | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Beam Profile Monitor for PAL-XFEL Gyu Jin Kim, Bongi Oh, Haeryong Yang, Heung-Sik Kang, In Soo Ko, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8711528/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract A beam profile monitor was developed for measuring the PAL-XFEL beam size. Due to the high energy of the electron beam, precise alignment of optical transition radiation (OTR) is crucial. Thus, a new design of the beam profile monitor was introduced to enable prealignment of the optics before installation. Additionally, the target holder was specially designed to remove coherent optical transition radiation (COTR) caused by the ultra-short bunch length of the hard X-ray FEL, similar to the beam profile monitor in SwissFEL. Moreover, the layout of the target holder was modified to reduce the size of the vacuum chamber, and the distance between the mirror and the beam path was increased to prevent diffraction radiation from the bypassing electron beam. The measurement results showed that the COTR problem was effectively eliminated, and no diffraction radiation was observed from the beam image. PACS numbers: 41.60.Cr, 41.60.Dk, 41.85.-p, 42.15.Eq Beam Profile Monitor Hard X-ray Free Electron Laser Coherent Optical Transition Radiation Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 08 Feb, 2026 Reviews received at journal 08 Feb, 2026 Reviewers agreed at journal 03 Feb, 2026 Reviews received at journal 03 Feb, 2026 Reviewers agreed at journal 28 Jan, 2026 Reviewers invited by journal 28 Jan, 2026 Editor assigned by journal 28 Jan, 2026 Submission checks completed at journal 28 Jan, 2026 First submitted to journal 27 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8711528","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":582142234,"identity":"6db139e4-2295-4aeb-89a7-16e42de7228b","order_by":0,"name":"Gyu Jin Kim","email":"","orcid":"","institution":"Pohang University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Gyu","middleName":"Jin","lastName":"Kim","suffix":""},{"id":582142235,"identity":"08c917d5-05a5-4fef-8694-732679acf287","order_by":1,"name":"Bongi Oh","email":"","orcid":"","institution":"Pohang University of Science and 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Due to the high energy of the electron beam, precise alignment of optical transition radiation (OTR) is crucial. Thus, a new design of the beam profile monitor was introduced to enable prealignment of the optics before installation. Additionally, the target holder was specially designed to remove coherent optical transition radiation (COTR) caused by the ultra-short bunch length of the hard X-ray FEL, similar to the beam profile monitor in SwissFEL. Moreover, the layout of the target holder was modified to reduce the size of the vacuum chamber, and the distance between the mirror and the beam path was increased to prevent diffraction radiation from the bypassing electron beam. 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