{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T13:02:06Z","timestamp":1790600526065,"version":"4.1.0"},"reference-count":29,"publisher":"AIP Publishing","issue":"9","funder":[{"DOI":"10.13039\/100024792","name":"General Atomics","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100024792","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000181","name":"Air Force Office of Scientific Research","doi-asserted-by":"publisher","award":["FA9550-24-1-0053"],"award-info":[{"award-number":["FA9550-24-1-0053"]}],"id":[{"id":"10.13039\/100000181","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["PHY-2206777"],"award-info":[{"award-number":["PHY-2206777"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,9,1]]},"abstract":"<jats:p>High-energy-density science experiments utilizing high-power laser systems increasingly operate at high repetition rates (HRRs), demanding automated and rapid target focusing to maintain data throughput. We present a robust autofocusing framework and a direct experimental validation of its performance. The system utilizes a dichroic mirror to collinearly align a continuous-wave 532\u00a0nm probe laser with the main beam, focusing both via an off-axis parabola to a &amp;lt;10\u00a0\u03bcm spot. A focal spot monitor positioned along the optical path captures back-reflected images of the probe light as a target is scanned through the focal axis. We compare seven distinct image-based focus metrics by correlating their chosen focal position with a direct physics-based performance indicator: the resulting x-ray flux produced when the laser is shot into a 34\u00a0\u03bcm copper flat foil target. Among the metrics tested, the Sobel Tenengrad operator provides the strongest combined high-yield and low-variability performance in the Si-diode measurements. Acceleration is evaluated through two coupled contributions: millisecond-scale metric computation and a dynamic gradient-skip search that reduces the number of acquired images and commanded motor positions relative to a 30-image full focal scan. For Sobel Tenengrad at a patience value of 5, the gradient-skip search retains 96.7% accuracy within \u00b11 image of the full-scan best focus while reducing the mean number of evaluated images from 30 to 22.93. These results support its use in practical HRR feedback loops where both metric reliability and scan efficiency are required.<\/jats:p>","DOI":"10.1063\/5.0342429","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T12:48:37Z","timestamp":1790599717000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Acceleration of autofocusing algorithms for fielding solid targets at high-repetition-rates"],"prefix":"10.1063","volume":"97","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-0273-7403","authenticated-orcid":false,"given":"D.","family":"Dahlke","sequence":"first","affiliation":[{"name":"University of California San Diego 1 , La Jolla, California 92093,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9154-8837","authenticated-orcid":false,"suffix":"IV","given":"G. W.","family":"Collins","sequence":"additional","affiliation":[{"name":"General Atomics 2 , San Diego, California 92121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"N.","family":"Sabouri","sequence":"additional","affiliation":[{"name":"University of California San Diego 1 , La Jolla, California 92093,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-0471-6302","authenticated-orcid":false,"given":"A.","family":"Keller","sequence":"additional","affiliation":[{"name":"General Atomics 2 , San Diego, California 92121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0597-0976","authenticated-orcid":false,"given":"A.","family":"Arefiev","sequence":"additional","affiliation":[{"name":"University of California San Diego 1 , La Jolla, California 92093,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5834-1161","authenticated-orcid":false,"given":"M. J.-E.","family":"Manuel","sequence":"additional","affiliation":[{"name":"General Atomics 2 , San Diego, California 92121,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,9,28]]},"reference":[{"key":"2026092808483442300_c1","doi-asserted-by":"publisher","first-page":"104003","DOI":"10.1088\/1361-6587\/ac1f67","article-title":"Accelerating the rate of discovery: Toward high-repetition-rate HED science","volume":"63","year":"2021","journal-title":"Plasma Phys. Controlled Fusion"},{"key":"2026092808483442300_c2","doi-asserted-by":"publisher","first-page":"4713","DOI":"10.1364\/ao.55.004713","article-title":"Experimental capabilities of 0.4 PW, 1 shot\/min Scarlet laser facility for high energy density science","volume":"55","year":"2016","journal-title":"Appl. Opt."},{"key":"2026092808483442300_c3","doi-asserted-by":"publisher","first-page":"149","DOI":"10.1016\/j.mre.2017.03.003","article-title":"P3: An installation for high-energy density plasma physics and ultra-high intensity laser\u2013matter interaction at ELI-beamlines","volume":"2","year":"2017","journal-title":"Matter Radiat. Extremes"},{"key":"2026092808483442300_c4","doi-asserted-by":"publisher","first-page":"e43","DOI":"10.1017\/hpl.2020.41","article-title":"High-energy hybrid femtosecond laser system demonstrating 2 \u00d7 10 PW capability","volume":"8","year":"2020","journal-title":"High Power Laser Sci. Eng."},{"key":"2026092808483442300_c5","first-page":"JThB2","volume-title":"Conference on Lasers and Electro-Optics","year":"2008"},{"key":"2026092808483442300_c6","doi-asserted-by":"publisher","first-page":"10807","DOI":"10.1364\/oe.20.010807","article-title":"Generation of high-contrast, 30\u00a0fs, 1.5 PW laser pulses from chirped-pulse amplification Ti:sapphire laser","volume":"20","year":"2012","journal-title":"Opt. Express"},{"key":"2026092808483442300_c7","doi-asserted-by":"publisher","first-page":"047106","DOI":"10.1063\/1.4870946","article-title":"Study of 1\u20138\u00a0keV K-\u03b1 x-ray emission from high intensity femtosecond laser produced plasma","volume":"4","year":"2014","journal-title":"AIP Adv."},{"key":"2026092808483442300_c8","doi-asserted-by":"publisher","first-page":"045004","DOI":"10.1103\/physrevlett.100.045004","article-title":"Study of x-ray emission enhancement via a high-contrast femtosecond laser interacting with a solid foil","volume":"100","year":"2008","journal-title":"Phys. Rev. Lett."},{"key":"2026092808483442300_c9","doi-asserted-by":"publisher","first-page":"20765","DOI":"10.1021\/acsomega.0c01135","article-title":"K\u03b1 X-ray emission from nanowire Cu targets driven by femtosecond laser pulses for X-ray conversion and backlight imaging","volume":"5","year":"2020","journal-title":"ACS Omega"},{"key":"2026092808483442300_c10","doi-asserted-by":"publisher","first-page":"986","DOI":"10.1080\/15361055.2025.2521878","article-title":"Advancing high-repetition-rate targeting: Implementation and performance of FRODO at GALADRIEL","volume":"82","year":"2026","journal-title":"Fusion Sci. Technol."},{"key":"2026092808483442300_c11","doi-asserted-by":"publisher","first-page":"921107","DOI":"10.1117\/12.2061803","article-title":"High-rep rate target development for ultra-intense interaction science at the central laser facility","volume":"9211","year":"2014","journal-title":"SPIE Proc."},{"key":"2026092808483442300_c12","doi-asserted-by":"publisher","first-page":"093303","DOI":"10.1063\/5.0158103","article-title":"A versatile control program for positioning and shooting targets in laser\u2013plasma experiments","volume":"94","year":"2023","journal-title":"Rev. Sci. Instrum."},{"key":"2026092808483442300_c13","doi-asserted-by":"publisher","first-page":"107041","DOI":"10.1016\/j.optlaseng.2022.107041","article-title":"Positioning of diffuse metallic target with a point diffractive interferometer","volume":"154","year":"2022","journal-title":"Opt. Lasers Eng."},{"key":"2026092808483442300_c14","doi-asserted-by":"publisher","first-page":"064402","DOI":"10.1063\/5.0065138","article-title":"Characterization and performance of the apollon short-focal-area facility following its commissioning at 1 PW level","volume":"6","year":"2021","journal-title":"Matter Radiat. Extremes"},{"key":"2026092808483442300_c15","doi-asserted-by":"publisher","first-page":"e32","DOI":"10.1017\/hpl.2024.11","article-title":"Metrology for sub-Rayleigh-length target positioning in \u223c1022 W\/cm2 laser\u2013plasma experiments","volume":"12","year":"2024","journal-title":"High Power Laser Sci. Eng."},{"key":"2026092808483442300_c16","doi-asserted-by":"publisher","first-page":"027203","DOI":"10.1063\/5.0247778","article-title":"Currents from relativistic laser\u2013plasma interaction as a novel metrology for the system stability of high-repetition-rate laser secondary sources","volume":"10","year":"2025","journal-title":"Matter Radiat. Extremes"},{"key":"2026092808483442300_c17","doi-asserted-by":"publisher","first-page":"113501","DOI":"10.1063\/5.0220160","article-title":"GALADRIEL: A facility for advancing engineering science relevant to rep-rated high energy density physics and inertial fusion energy experiments","volume":"95","year":"2024","journal-title":"Rev. Sci. Instrum."},{"key":"2026092808483442300_c18","doi-asserted-by":"publisher","first-page":"223","DOI":"10.1007\/bf00127822","article-title":"Focusing","volume":"1","year":"1988","journal-title":"Int. J. Comput. Vis."},{"key":"2026092808483442300_c19","doi-asserted-by":"publisher","first-page":"37","DOI":"10.1155\/2013\/412920","article-title":"Evaluations of auto-focusing methods under a microscopic imaging modality for metaphase chromosome image analysis","volume":"36","year":"2013","journal-title":"Anal. Cell. Pathol."},{"key":"2026092808483442300_c20","doi-asserted-by":"publisher","first-page":"e0304085","DOI":"10.1371\/journal.pone.0304085","article-title":"Development of a low-cost robotized 3D-prototype for automated optical microscopy diagnosis: An open-source system","volume":"19","year":"2024","journal-title":"PLoS One"},{"key":"2026092808483442300_c21","doi-asserted-by":"publisher","first-page":"213","DOI":"10.1002\/cyto.a.22020","article-title":"Comparative evaluation of autofocus algorithms for a real-time system for automatic detection of Mycobacterium tuberculosis","volume":"81A","year":"2012","journal-title":"Cytometry, Part A"},{"key":"2026092808483442300_c22","doi-asserted-by":"publisher","first-page":"100","DOI":"10.1177\/24.1.1254907","article-title":"An automated microscope for cytologic research a preliminary evaluation","volume":"24","year":"1976","journal-title":"J.\u00a0Histochem. Cytochem."},{"key":"2026092808483442300_c23","doi-asserted-by":"publisher","first-page":"8670","DOI":"10.1364\/oe.16.008670","article-title":"Simple and robust image-based autofocusing for digital microscopy","volume":"16","year":"2008","journal-title":"Opt. Express"},{"key":"2026092808483442300_c24","doi-asserted-by":"publisher","first-page":"075016","DOI":"10.1063\/5.0046287","article-title":"Laser spot measurement using simple devices","volume":"11","year":"2021","journal-title":"AIP Adv."},{"key":"2026092808483442300_c25","doi-asserted-by":"publisher","first-page":"181","DOI":"10.1006\/adnd.1993.1013","article-title":"X-ray interactions: Photoabsorption, scattering, transmission, and reflection at E = 50\u201330\u2009000\u00a0eV, Z = 1\u201392","volume":"54","year":"1993","journal-title":"At. Data Nucl. Data Tables"},{"key":"2026092808483442300_c26","doi-asserted-by":"publisher","first-page":"98","DOI":"10.1117\/12.474947","article-title":"White light interferometry","volume":"4737","year":"2002","journal-title":"Proc. SPIE"},{"key":"2026092808483442300_c27","doi-asserted-by":"publisher","first-page":"063505","DOI":"10.1063\/5.0197995","article-title":"High repetition-rate foam targetry for laser\u2013plasma interaction experiments: Concept and preliminary results","volume":"95","year":"2024","journal-title":"Rev. Sci. Instrum."},{"key":"2026092808483442300_c28","doi-asserted-by":"publisher","first-page":"063504","DOI":"10.1063\/5.0053281","article-title":"High-repetition rate solid target delivery system for PW-class laser\u2013matter interaction at ELI beamlines","volume":"92","year":"2021","journal-title":"Rev. Sci. Instrum."},{"key":"2026092808483442300_c29","first-page":"2230","article-title":"Learning to autofocus","year":"2020"}],"container-title":["Review of Scientific Instruments"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.aip.org\/aip\/rsi\/article-pdf\/doi\/10.1063\/5.0342429\/21152882\/093515_1_5.0342429.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.aip.org\/aip\/rsi\/article-pdf\/doi\/10.1063\/5.0342429\/21152882\/093515_1_5.0342429.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T12:48:38Z","timestamp":1790599718000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.aip.org\/rsi\/article\/97\/9\/093515\/3405357\/Acceleration-of-autofocusing-algorithms-for"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,1]]},"references-count":29,"journal-issue":{"issue":"9","published-print":{"date-parts":[[2026,9,1]]}},"URL":"https:\/\/doi.org\/10.1063\/5.0342429","relation":{},"ISSN":["0034-6748","1089-7623"],"issn-type":[{"value":"0034-6748","type":"print"},{"value":"1089-7623","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026,9]]},"published":{"date-parts":[[2026,9,1]]},"article-number":"093515"}}