Editing Fermilab (section)

==Accelerators==
===Tevatron===
Prior to the startup in 2008 of the [[Large Hadron Collider]] (LHC) near Geneva, Switzerland, the [[Tevatron]] was the most powerful particle accelerator in the world, accelerating protons and antiprotons to energies of 980&nbsp;[[GeV]], and producing proton-antiproton collisions with energies of up to 1.96&nbsp;[[TeV]], the first accelerator to reach one "tera-electron-volt" energy.<ref>{{cite arXiv |last1=Shiltsev |first1=Vladimir |title=Achievements and Lessons from Tevatron |year=2012 |class=physics.acc-ph |eprint=1205.0536}}</ref>  At {{convert|3.9|mi|km}}, it was the world's fourth-largest particle accelerator in circumference.  One of its most important achievements was the 1995 discovery of the [[top quark]], announced by research teams using the Tevatron's [[Collider Detector at Fermilab|CDF]] and [[DØ experiment|DØ]] detectors.<ref>{{cite journal |last1=Bandurin, Dmitry |display-authors=etal |title=Review of physics results from the Tevatron |journal=International Journal of Modern Physics A |year=2015 |volume=30 |issue=6 |doi=10.1142/S0217751X15410018 |arxiv=1409.4861|bibcode=2015IJMPA..3041001B |s2cid=118699490 }}</ref> It was shut down in 2011.

===Fermilab Accelerator Complex===
Since 2013, the first stage in the acceleration process (pre-accelerator injector) in the Fermilab chain of accelerators<ref>{{cite web |title=Animation of Fermilab's Accelerator Complex |url=https://www.youtube.com/watch?v=vElqxVUoKSE&feature=youtu.be | archive-url=https://ghostarchive.org/varchive/youtube/20211211/vElqxVUoKSE| archive-date=December 11, 2021 | url-status=live|website=YouTube | date=March 21, 2018 |publisher=Fermilab |access-date=February 25, 2021}}{{cbignore}}</ref> takes place in two [[ion source]]s which ionize [[hydrogen]] gas. The gas is introduced into a container lined with molybdenum electrodes, each a matchbox-sized, oval-shaped cathode and a surrounding anode, separated by 1&nbsp;mm and held in place by glass ceramic insulators. A [[magnetron|cavity magnetron]] generates a plasma to form the ions near the metal surface. The ions are accelerated by the source to 35&nbsp;[[keV]] and matched by low energy beam transport (LEBT) into the [[radio-frequency quadrupole]] (RFQ) which applies a 750&nbsp;[[keV]] electrostatic field giving the ions their second acceleration. At the exit of RFQ, the beam is matched by medium energy beam transport (MEBT) into the entrance of the [[linear accelerator]] (linac).<ref>{{cite conference |first1=J.P. |last1=Carneiro |first2=F.G. |last2=Garcia |first3=J.-F. |last3=Ostiguy |first4=A. |last4=Saini |first5=R. |last5=Zwaska |title=Transmission efficiency measurement at the FNAL 4-rod RFQ (FERMILAB-CONF-14-452-APC) |journal=27th International Linear Accelerator Conference (LINAC14) |date=November 13, 2014 |url=https://www-ad.fnal.gov/proton/PIP/Communicate/Calendar/Repository/2014/MOPP050_Linac2014_Carneiro.pdf |access-date=August 12, 2015 |arxiv=1411.3614 |isbn=978-3-95450-142-7 |pages=168–170 |bibcode=2014arXiv1411.3614C |url-status=live |archive-url=https://web.archive.org/web/20160423174912/https://www-ad.fnal.gov/proton/PIP/Communicate/Calendar/Repository/2014/MOPP050_Linac2014_Carneiro.pdf |archive-date=April 23, 2016 }}</ref>

The next stage of acceleration is a linear particle accelerator (linac). This stage consists of two segments. The first segment has five drift tube cavities, operating at 201&nbsp;MHz. The second stage has seven&nbsp;side-coupled cavities, operating at 805&nbsp;MHz. At the end of linac, the particles are accelerated to 400&nbsp;[[MeV]], or about 70% of the [[speed of light]].<ref name=slideshow>{{cite web |title=Fermilab Linac Slide Show Description |url=http://www-ad.fnal.gov/proton/NewProtonWWW/NewLinacWWW/images/stamps/slideShow.html |website=Fermilab |access-date=August 12, 2015 |url-status=live |archive-url=https://web.archive.org/web/20160418203333/http://www-ad.fnal.gov/proton/NewProtonWWW/NewLinacWWW/images/stamps/slideShow.html |archive-date=April 18, 2016}}</ref><ref>{{cite book |last1=Kubik |first1=Donna |title=Fermilab |date=2005 |url=http://home.fnal.gov/~kubik/Accelerators/Fermilab.pdf |access-date=August 12, 2015 |url-status=live |archive-url=https://web.archive.org/web/20160422151506/http://home.fnal.gov/~kubik/Accelerators/Fermilab.pdf |archive-date=April 22, 2016}}</ref> Immediately before entering the next accelerator, the H<sup>−</sup> ions pass through a carbon foil, becoming H<sup>+</sup> ions ([[proton]]s).<ref name=accelerator>{{cite web |title=Accelerator |url=http://www.fnal.gov/pub/tevatron/tevatron-accelerator.html |website=Fermilab |access-date=August 12, 2015 |url-status=live |archive-url=https://web.archive.org/web/20150804144005/http://www.fnal.gov/pub/tevatron/tevatron-accelerator.html |archive-date=August 4, 2015}}</ref>

The resulting protons then enter the booster ring, a {{cvt|468|m|ft}} circumference circular accelerator whose magnets bend beams of protons around a circular path. The protons travel around the Booster about 20,000&nbsp;times in 33&nbsp;milliseconds, adding energy with each revolution until they leave the Booster accelerated to 8&nbsp;[[GeV]].<ref name=accelerator/> In 2021, the lab announced that its latest superconducting [[Yttrium barium copper oxide|YBCO]] magnet could increase field strength at a rate of 290 [[Tesla (unit)|tesla]] per second, reaching a peak magnetic field strength of around 0.5 tesla.<ref>{{Cite web|last=Lavars|first=Nick|date=December 2, 2021|title=Next-gen particle accelerator magnet ramps up at record speed|url=https://newatlas.com/technology/next-generation-particle-accelerator-magnet-record-speed/|access-date=December 2, 2021|website=New Atlas|language=en-US}}</ref>

The final acceleration is applied by the Main Injector [circumference {{cvt|3319.4|m|ft}}], which is the smaller of the two rings in the last picture below (foreground). Completed in 1999, it has become Fermilab's "particle switchyard"<ref>{{cite web |title=Switchyard |url=https://www.fnal.gov/pub/news03/definitions/switchyard.html |website=Operation Terminology |publisher=Fermilab |access-date=1 October 2024}}</ref> in that it can route protons to any of the experiments installed along the beam lines after accelerating them to 120&nbsp;GeV. Until 2011, the Main Injector provided protons to the [[antiproton]] ring [circumference {{cvt|6283.2|m|ft}}] and the [[Tevatron]] for further acceleration but now provides the last push before the particles reach the beam line experiments.

<gallery mode="packed" class="center">
Two ion sources at Fermilab.jpg|Two ion sources at the center with two high-voltage electronics cabinets next to them<ref name=35years>{{cite web |title=35&nbsp;years of H<sup>−</sup> ions at Fermilab |url=http://www-ad.fnal.gov/proton/PIP/Communicate/Calendar/Repository/2014/35%20years%20of%20H-%20ions%20at%20Fermilab.pdf |website=Fermilab |access-date=12 August 2015 |url-status=live |archive-url=https://web.archive.org/web/20151018080322/http://www-ad.fnal.gov/proton/PIP/Communicate/Calendar/Repository/2014/35%20years%20of%20H-%20ions%20at%20Fermilab.pdf |archive-date=18 October 2015}}</ref>
RFQ MEBT and linac at Fermilab.jpg|Beam direction right to left: RFQ (silver), MEBT (green), first drift tube linac (blue)<ref name=35years/>
The 7835 power amplifiers at Fermilab.JPG|A 7835 power amplifier that is used at the first stage of linac<ref name=slideshow/>
A 12 MW klystron at Fermilab.jpg|A 12&nbsp;MW [[klystron]] used at the second stage of linac<ref name=slideshow/>
The 805 MHz side-couple cavities.jpg|A cutaway view of the 805&nbsp;MHz side-couple cavities<ref>{{cite conference |last1=May |first1=Michael P. |last2=Fritz |first2=James R. |last3=Jurgens |first3=Thomas G. |last4=Miller |first4=Harold W. |last5=Olson |first5=James |last6=Snee |first6=Daniel |title=Mechanical construction of the 805&nbsp;MHz side couple cavities for the Fermilab Linac upgrade |conference=Linear Accelerator Conference |date=1990 |journal=Proceedings of the 1990 Linear Accelerator Conference |url=https://accelconf.web.cern.ch/accelconf/l90/papers/mo423.pdf |access-date=13 August 2015 |location=Albuquerque, New Mexico, USA |url-status=live |archive-url=https://web.archive.org/web/20150707145718/http://accelconf.web.cern.ch/AccelConf/l90/papers/mo423.pdf |archive-date=7 July 2015}}</ref>
Booster ring at Fermilab.jpg|Booster ring<ref>{{cite web |title=Wilson Hall & vicinity |url=https://www.fnal.gov/pub/visiting/map/wilson.html |website=Fermilab |access-date=12 August 2015 |url-status=live |archive-url=https://web.archive.org/web/20150917055551/http://www.fnal.gov/pub/visiting/map/wilson.html |archive-date=17 September 2015}}</ref>
Fermilab.jpg|Fermilab's accelerator rings. The main injector is in the foreground, and the [[antiproton]] ring and [[Tevatron]] (inactive since 2011) are in the background.
Fermilab g-2 (E989) ring.jpg| The E989 storage-ring magnet at Fermilab
</gallery>

===Proton improvement plan===
Recognizing higher demands of proton beams to support new experiments, Fermilab began to improve their accelerators in 2011. Expected to continue for many years,<ref name=pip/> the project has two phases: Proton Improvement Plan (PIP) and Proton Improvement Plan-II (PIP-II).<ref name=mwproton>{{cite report |last1=Holmes |first1=Steve |title=MegaWatt Proton Beams for Particle Physics at Fermilab |date=December 16, 2013 |publisher=Fermilab |url=https://pip2.fnal.gov/files/P5_SDH_v5.pdf |access-date=August 15, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150905210745/http://pip2.fnal.gov/files/P5_SDH_v5.pdf |archive-date=September 5, 2015 }}</ref>

;PIP (2011–2018)
The overall goals of PIP are to increase the repetition rate of the Booster beam from 7&nbsp;Hz to 15&nbsp;Hz and replace old hardware to increase reliability of the operation.<ref name=mwproton/> Before the start of the PIP project, a replacement of the pre-accelerator injector was underway. The replacement of almost 40&nbsp;year-old [[Cockcroft–Walton generator]]s to RFQ started in 2009 and completed in 2012. At the Linac stage, the analog beam position monitor (BPM) modules were replaced with digital boards in 2013. A replacement of Linac vacuum pumps and related hardware is expected to be completed in 2015. A study on the replacement of 201&nbsp;MHz drift tubes is still ongoing. At the boosting stage, a major component of the PIP is to upgrade the Booster ring to 15&nbsp;Hz operation. The Booster has 19&nbsp;radio frequency stations. Originally, the Booster stations were operating without [[Solid-state electronics|solid-state]] drive system which was acceptable for 7&nbsp;Hz but not 15&nbsp;Hz operation. A demonstration project in 2004 converted one of the stations to solid state drive before the PIP project. As part of the project, the remaining stations were converted to solid state in 2013. Another major part of the PIP project is to refurbish and replace 40&nbsp;year-old Booster cavities. Many cavities have been refurbished and tested to operate at 15&nbsp;Hz. The completion of cavity refurbishment is expected in 2015, after which the repetition rate can be gradually increased to 15&nbsp;Hz operation. A longer term upgrade is to replace the Booster cavities with a new design. The research and development of the new cavities is underway, with replacement expected in 2018.<ref name=pip>{{cite conference |title=Proceedings of IPAC2014 |year=2014 |place=Dresden, Germany |isbn=978-3-95450-132-8 |pages=3409–3411 |conference=5th International Particle Accelerator Conference |conference-url=http://accelconf.web.cern.ch/AccelConf/IPAC2014 |chapter-url=http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/thpme075.pdf |access-date=August 15, 2015 |chapter=FNAL – The Proton Improvement Plan (PIP) |url-status=live |archive-url=https://web.archive.org/web/20150626175507/http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/thpme075.pdf |archive-date=June 26, 2015 }}</ref>

;PIP-II
[[File:Two AES 5-cells cavities.jpg|thumb|Prototypes of [[superconducting radio frequency|SRF]] cavities to be used in the last segment of PIP-II Linac<ref>{{cite conference |conference=27th Linear Accelerator Conference (LINAC2014) |conference-url=http://linac14.org/ |location=Geneva, Switzerland |date=September 2014 |isbn=978-3-95450-142-7 |pages=171–173 |title=Development of 5&nbsp;Cell Beta=0.9&thinsp;650&nbsp;MHz Cavities for Project&nbsp;X |url=http://accelconf.web.cern.ch/AccelConf/LINAC2014/papers/mopp052.pdf |access-date=August 16, 2015 |first1=M.H. |last1=Awida |first2=M. |last2=Foley |first3=I. |last3=Gonin |first4=A. |last4=Grassellino |first5=C. |last5=Grimm |first6=T. |last6=Khabiboulline |first7=A. |last7=Lunin |first8=A. |last8=Rowe |first9=V. |last9=Yakovlev |url-status=live |archive-url=https://web.archive.org/web/20150702020105/http://accelconf.web.cern.ch/AccelConf/LINAC2014/papers/mopp052.pdf |archive-date=July 2, 2015}}</ref>]]

The goals of PIP-II include a plan to delivery 1.2&nbsp;MW of proton beam power from the Main Injector to the [[Deep Underground Neutrino Experiment]] target at 120&nbsp;GeV and the power near 1&nbsp;MW at 60&nbsp;GeV with a possibility to extend the power to 2&nbsp;MW in the future. The plan should also support the current 8&nbsp;GeV experiments including Mu2e, Muon g−2, and other short-baseline neutrino experiments. These require an upgrade to the Linac to inject to the Booster with 800&nbsp;MeV. The first option considered was to add 400&nbsp;MeV "afterburner" superconducting Linac at the tail end of the existing 400&nbsp;MeV. This would have required moving the existing Linac up {{Convert|50|m}}. However, there were many technical issues with this approach. Instead, Fermilab is building a new 800&nbsp;MeV superconducting Linac to inject to the Booster ring.

Construction of the first building for the PIP-II accelerator began in 2020.<ref name="auto"/> The new Linac site will be located on top of a small portion of [[Tevatron]] near the Booster ring in order to take advantage of existing electrical and water, and cryogenic infrastructure. The PIP-II Linac will have low energy beam transport line (LEBT), radio frequency quadrupole (RFQ), and medium energy beam transport line (MEBT) operated at the room temperature at with a 162.5&nbsp;MHz and energy increasing from 0.03&nbsp;MeV. The first segment of Linac will be operated at 162.5&nbsp;MHz and energy increased up to 11&nbsp;MeV. The second segment of Linac will be operated at 325&nbsp;MHz and energy increased up to 177&nbsp;MeV. The last segment of linac will be operated at 650&nbsp;MHz and will have the final energy level of 800&nbsp;MeV.<ref>{{cite report |title=Proton Improvement Plan&nbsp;II |date=December 12, 2013 |publisher=Fermilab |url=http://projectx-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=1232&filename=1.2%20MW%20Report_Rev5.pdf&version=3 |access-date=August 15, 2015 |url-status=live |archive-url=https://web.archive.org/web/20160422155048/http://projectx-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=1232&filename=1.2%20MW%20Report_Rev5.pdf&version=3 |archive-date=April 22, 2016}}</ref>

As of 2022, the estimated PIP-II accelerator start date for the accelerator is 2028.<ref name=enddate>{{cite news| title=PIP-II: An international effort breaking new ground in particle physics| url=https://www.innovationnewsnetwork.com/pip-ii-enhancements-fermilab-accelerator-complex/18907/|date=March 4, 2022|work=Innovation News Network}}</ref> The project was approved for construction in April 2022 with an expected cost to the Department of Energy of $978M and with an additional $330M in contributions from international partners.<ref>{{cite news |last1=Thomas |first1=Will |title=Fermilab Accelerator Upgrade Moves Into Construction Phase |url=https://www.aip.org/fyi/fyi-this-week/week-april-25-2022 |publisher=FYI: American Institute of Physics |date=April 25, 2022}}</ref>