Editing Free-electron laser (section)

===Infrared and terahertz FELs===
The [[Fritz Haber Institute of the Max Planck Society|Fritz Haber Institute]] in Berlin completed a mid-infrared and [[Terahertz spectroscopy and technology|terahertz]] FEL in 2013.<ref>{{Cite journal|last1=Schöllkopf|first1=Wieland|last2=Gewinner|first2=Sandy|last3=Junkes|first3=Heinz|last4=Paarmann|first4=Alexander|last5=von Helden|first5=Gert|last6=Bluem|first6=Hans P.|last7=Todd|first7=Alan M. M.|editor1-first=Sandra G|editor1-last=Biedron|date=201|title=The new IR and THz FEL facility at the Fritz Haber Institute in Berlin|journal=Advances in X-ray Free-Electron Lasers Instrumentation III|publisher=International Society for Optics and Photonics|volume=9512|pages=95121L|doi=10.1117/12.2182284|bibcode=2015SPIE.9512E..1LS|hdl=11858/00-001M-0000-0027-13DB-1|s2cid=55435812|hdl-access=free}}</ref><ref>{{Cite web|title=The FHI free-electron laser (FEL) facility|url=https://www.fhi.mpg.de/230029/FEL|website=Fritz Haber Institute of the Max Planck Society|language=en|access-date=2020-05-04}}</ref>

At [[Helmholtz-Zentrum Dresden-Rossendorf|Helmholtz-Zentrum Dresden - Rossendorf]] two terahertz and mid-infrared FEL-based sources are in operation. FELBE is an FEL equipped with a cavity with continuous pulsing with a repetition rate of 13 MHz, pulsing with 1 kHz by applying a pulse picker, and macrobunch operation with bunch length > 100 μs and macrobunch repetition rates ≤ 25 Hz. Pulse duration and pulse energy vary with wavelength and lie in the range from 1 - 25 ps and 100 nJ - few μJ, respectively. <ref>{{Cite web |title=FELBE |url=https://www.fels-of-europe.eu/fel_facilities/ir_facilities/felbe/ |access-date=2025-01-07 |website=www.fels-of-europe.eu}}</ref> The TELBE facility is based on a [[Superradiant emission|superradiant]] undulator offering THz pulses ranging from 0.1 THz to 2.5 THz at repetition rates up to 500 kHz.<ref>{{Cite web |title=TELBE - Helmholtz-Zentrum Dresden-Rossendorf, HZDR |url=https://www.hzdr.de/db/Cms?pOid=34100&pNid=2609 |access-date=2025-01-07 |website=www.hzdr.de |language=en}}</ref>