Antiproton Accumulator - Revision history

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	*[[Super Proton–Antiproton Synchrotron]]		*[[Super Proton–Antiproton Synchrotron]]

			For more information, see [[wikipedia:Antiproton Accumulator\|Wikipedia]].
	== References ==		== References ==
	{{reflist}}		{{reflist}}
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	[[Category:Accelerator physics]]		[[Category:Accelerator physics]]
	[[Category:Decommissioned CERN particle accelerators]]		[[Category:Decommissioned CERN particle accelerators]]
			[[Category:Pages linking to Wikipedia]]

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	{{CERN}}		{{CERN}}
	[[Category:Accelerator physics]]		[[Category:Accelerator physics]]
			[[Category:Decommissioned CERN particle accelerators]]

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	{{CERN}}		{{CERN}}
	[[Category:Accelerator physics]]		[[Category:Accelerator physics]]
	~~[[Category:Decommissioned CERN accelerators]]~~

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	{{~~Short description~~\|~~Part~~ of the CERN ~~proton~~-antiproton collider}}{{~~sppbarS~~}}		The '''Antiproton Accumulator''' ('''AA''') was an infrastructure connected to the [[Proton–Antiproton Collider]] (Sp{{overline\|p}}S) – a modification of the [[Super Proton Synchrotron]] (SPS) – at [[CERN]].<ref name="BillingeCrowley-Milling1979">{{cite journal\|last1=Billinge\|first1=R.\|last2=Crowley-Milling\|first2=M. C.\|author-link2=Michael Crowley-Milling \|title=The CERN Proton-Antiproton Colliding Beam Facilities\|journal=IEEE Transactions on Nuclear Science\|volume=26\|issue=3\|year=1979\|pages=2974–2977\|issn=0018-9499\|doi=10.1109/TNS.1979.4329913\|url = https://cds.cern.ch/record/133244/files/cer-000043825.pdf\|bibcode = 1979ITNS...26.2974B \|s2cid=33805929 }}</ref><ref name="Brianti1983">{{cite journal\|url = https://cds.cern.ch/record/149018/files/cer-000060237.pdf\|last1=Brianti\|first1=G.\|title=Experience with the CERN ppbar complex\|journal=IEEE Transactions on Nuclear Science\|volume=30\|issue=4\|year=1983\|pages=1950–1956\|issn=0018-9499\|doi=10.1109/TNS.1983.4332685\|bibcode = 1983ITNS...30.1950B \|s2cid=39013232 }}</ref> The AA was built in 1979 and 1980, for the production and accumulation of antiprotons.<ref name="KoziolMöhl2004">{{cite journal\|url = https://cds.cern.ch/record/806277/files/ab-2004-097.pdf\|last1=Koziol\|first1=H.\|last2=Möhl\|first2=D.\|title=The CERN antiproton collider programme: accelerators and accumulation rings\|journal=Physics Reports\|volume=403-404\|year=2004\|pages=91–106\|issn=0370-1573\|doi=10.1016/j.physrep.2004.09.001\|bibcode = 2004PhR...403...91K }}</ref><ref name="EvansJones1989">{{cite book\|last1=Evans\|first1=Lyndon\|author-link1 = Lyn Evans\|last2=Jones\|first2=Eifionydd\|last3=Koziol\|first3=Heribert\|editor1-last=Di Lella\|editor1-first=Luigi\|editor2-last=Altarelli \|editor2-first=Guido\| editor2-link=Guido Altarelli\|title=Proton-antiproton collider physics\|volume=4\|year=1989\|pages=1–44\|doi=10.1142/9789814503242_0001\|chapter=The CERN ppbar collider \|publisher = World Scientific\|isbn=9789971505622 }}</ref> In the Sp{{overline\|p}}S the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV (later raised to 630 GeV and finally, in a pulsed mode, to 900 GeV). Several experiments recorded data from the collisions, most notably the [[UA1]] and [[UA2\|UA2 experiment]], where the W and Z bosons were discovered in 1983.

	The '''Antiproton Accumulator''' ('''AA''') was an infrastructure connected to the [[Proton–Antiproton Collider]] (Sp{{overline\|p}}S) – a modification of the [[Super Proton Synchrotron]] (SPS) – at [[CERN]].<ref name="BillingeCrowley-Milling1979">{{cite journal\|last1=Billinge\|first1=R.\|last2=Crowley-Milling\|first2=M. C.\|author-link2=Michael Crowley-Milling \|title=The CERN Proton-Antiproton Colliding Beam Facilities\|journal=IEEE Transactions on Nuclear Science\|volume=26\|issue=3\|year=1979\|pages=2974–2977\|issn=0018-9499\|doi=10.1109/TNS.1979.4329913\|url = https://cds.cern.ch/record/133244/files/cer-000043825.pdf\|bibcode = 1979ITNS...26.2974B \|s2cid=33805929 }}</ref><ref name="Brianti1983">{{cite journal\|url = https://cds.cern.ch/record/149018/files/cer-000060237.pdf\|last1=Brianti\|first1=G.\|title=Experience with the CERN ppbar complex\|journal=IEEE Transactions on Nuclear Science\|volume=30\|issue=4\|year=1983\|pages=1950–1956\|issn=0018-9499\|doi=10.1109/TNS.1983.4332685\|bibcode = 1983ITNS...30.1950B \|s2cid=39013232 }}</ref> The AA was built in 1979 and 1980, for the production and accumulation of [[antiproton]]s.<ref name="KoziolMöhl2004">{{cite journal\|url = https://cds.cern.ch/record/806277/files/ab-2004-097.pdf\|last1=Koziol\|first1=H.\|last2=Möhl\|first2=D.\|title=The CERN antiproton collider programme: accelerators and accumulation rings\|journal=Physics Reports\|volume=403-404\|year=2004\|pages=91–106\|issn=0370-1573\|doi=10.1016/j.physrep.2004.09.001\|bibcode = 2004PhR...403...91K }}</ref><ref name="EvansJones1989">{{cite book\|last1=Evans\|first1=Lyndon\|author-link1 = Lyn Evans\|last2=Jones\|first2=Eifionydd\|last3=Koziol\|first3=Heribert\|editor1-last=Di Lella\|editor1-first=Luigi\|editor2-last=Altarelli \|editor2-first=Guido\| editor2-link=Guido Altarelli\|title=Proton-antiproton collider physics\|volume=4\|year=1989\|pages=1–44\|doi=10.1142/9789814503242_0001\|chapter=The CERN ppbar collider \|publisher = World Scientific\|isbn=9789971505622 }}</ref> In the Sp{{overline\|p}}S the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV (later raised to 630 GeV and finally, in a pulsed mode, to 900 GeV). Several experiments recorded data from the collisions, most notably the [[UA1 experiment\|UA1]] and [[UA2 experiment]], where the [[W and Z bosons]] were discovered in 1983.		The concept of the project was developed and promoted by [[Carlo Rubbia\|C. Rubbia]], for which he received the Nobel prize in 1984.<ref>{{cite web \|url=http://www.nobelprize.org/nobel_prizes/physics/laureates/1984/press.html \|title=Press Release: The 1984 Nobel Prize in Physics \|author=<!--Not stated--> \|date=17 October 1984 \|website=Nobelprize.org \|access-date=24 July 2017 }}</ref> He shared the prize with [[Simon van der Meer]], whose invention of the method of stochastic cooling made large scale production of antiprotons possible for the first time.

	The concept of the project was developed and promoted by [[Carlo Rubbia\|C. Rubbia]], for which he received the ~~[[List of Nobel laureates in Physics\|~~Nobel prize in 1984]].<ref>{{cite web \|url=http://www.nobelprize.org/nobel_prizes/physics/laureates/1984/press.html \|title=Press Release: The 1984 Nobel Prize in Physics \|author=<!--Not stated--> \|date=17 October 1984 \|website=Nobelprize.org \|access-date=24 July 2017 }}</ref> He shared the prize with [[Simon van der Meer]], whose invention of the method of [[stochastic cooling]] made large scale production of antiprotons possible for the first time.

	== Operation ==		== Operation ==
	~~[[File:Overview of the Antiproton Accumulator (AA) at CERN.jpg\|thumb\|Overview of the Antiproton Accumulator (AA) at [[CERN]]\|263x263px]]~~		Antiprotons were produced by directing an intense proton beam at a momentum of 26 GeV/c from the [[Proton Synchrotron]] (PS) onto a target for production. The emerging burst of antiprotons had a momentum of 3.5 GeV/c, and was selected via a spectrometer, and injected into the AA.<ref name="van der Meer1981">{{cite journal\|url=http://accelconf.web.cern.ch/AccelConf/p81/PDF/PAC1981_1994.PDF\|last1=van der Meer\|first1=S.\|author-link1 = Simon van der Meer\|title=Stochastic Cooling in the CERN Antiproton Accumulator\|journal=IEEE Transactions on Nuclear Science\|volume=28\|issue=3\|year=1981\|pages=1994–1998\|issn=0018-9499\|doi=10.1109/TNS.1981.4331574\|bibcode = 1981ITNS...28.1994V }}</ref> The produced antiprotons would have a substantial momentum spread, which was decreased during a 2 s orbit around the AA, using Simon van der Meers method of stochastic cooling. The antiprotons were then trapped using a radiofrequency system, and moved inwards in the orbit to a stacking region.<ref name=Evans>{{cite book \|last1=Evans \|first1=Lyndon \|last2=Jones \|first2=Eifionydd \|last3=Koziol \|first3=Heribert \|year=1989 \|chapter=The CERN ppbar Collider \|editor1-last=Altarelli \|editor1-first=G. \|editor2-last=Di Lella \|editor2-first=Luigi \|title=Proton-Antiproton Collider Physics \|series=Advanced Series on Directions in High Energy Physics \|volume=4 \|publisher=World Scientific Publishing}}</ref> A next burst of antiprotons arrived 2.4 s (the PS cycle time) after the preceding one. This process was repeated during the whole accumulation period, which took about a day. The most intense stack, obtained after many days, would typically contain 5.2·10<sup>11</sup> antiprotons.<ref name=Evans />

	Antiprotons were produced by directing an intense proton beam at a momentum of 26 GeV/c from the [[Proton Synchrotron]] (PS) onto a target for production. The emerging burst of antiprotons had a momentum of 3.5 GeV/c, and was selected via a [[spectrometer]], and injected into the AA.<ref name="van der Meer1981">{{cite journal\|url=http://accelconf.web.cern.ch/AccelConf/p81/PDF/PAC1981_1994.PDF\|last1=van der Meer\|first1=S.\|author-link1 = Simon van der Meer\|title=Stochastic Cooling in the CERN Antiproton Accumulator\|journal=IEEE Transactions on Nuclear Science\|volume=28\|issue=3\|year=1981\|pages=1994–1998\|issn=0018-9499\|doi=10.1109/TNS.1981.4331574\|bibcode = 1981ITNS...28.1994V }}</ref> The produced antiprotons would have a substantial momentum spread, which was decreased during a 2 s orbit around the AA, using [[Simon van der ~~Meer]]s~~ method of [[stochastic cooling]]. The antiprotons were then trapped using a [[radiofrequency]] system, and moved inwards in the orbit to a stacking region.<ref name=Evans>{{cite book \|last1=Evans \|first1=Lyndon \|last2=Jones \|first2=Eifionydd \|last3=Koziol \|first3=Heribert \|year=1989 \|chapter=The CERN ppbar Collider \|editor1-last=Altarelli \|editor1-first=G. \|editor2-last=Di Lella \|editor2-first=Luigi \|title=Proton-Antiproton Collider Physics \|series=Advanced Series on Directions in High Energy Physics \|volume=4 \|publisher=World Scientific Publishing}}</ref> A next burst of antiprotons arrived 2.4 s (the PS cycle time) after the preceding one. This process was repeated during the whole accumulation period, which took about a day. The most intense stack, obtained after many days, would typically contain 5.2·10<sup>11</sup> antiprotons.<ref name=Evans />

	The dense core of antiprotons was then ejected from the AA, and accelerated to 26 GeV/c, using the PS. Three antiproton bunches were consecutively transferred to the Sp{{overline\|p}}S, every 2.4 s.<ref name=Evans /> Just before the antiproton transfer, the PS would already have accelerated and transferred three proton bunches circulating the opposite direction to the antiprotons. When three bunches of antiprotons and three bunches of protons have filled the Sp{{overline\|p}}S, the bunches were accelerated to 315 GeV, and the beams were circulated for hours. During this time the AA continued to accumulate, to be ready for the next day's transfer.<ref name=Evans />		The dense core of antiprotons was then ejected from the AA, and accelerated to 26 GeV/c, using the PS. Three antiproton bunches were consecutively transferred to the Sp{{overline\|p}}S, every 2.4 s.<ref name=Evans /> Just before the antiproton transfer, the PS would already have accelerated and transferred three proton bunches circulating the opposite direction to the antiprotons. When three bunches of antiprotons and three bunches of protons have filled the Sp{{overline\|p}}S, the bunches were accelerated to 315 GeV, and the beams were circulated for hours. During this time the AA continued to accumulate, to be ready for the next day's transfer.<ref name=Evans />

	== Antimatter experiments ==		== Antimatter experiments ==
	~~{{Antimatter facilities}}[[File:Simon van der Meer in the AA Control Room.jpg\|thumb\|[[Simon van der Meer]] in the Antiproton Accumulator Control Room, 1984\|262x262px]]~~From the beginning of the project, the potential of physics with low-energy antiprotons was recognized. A [[Low Energy Antiproton Ring]] (LEAR) was built and received antiprotons from the AA from 1983 on, for deceleration to as low as 100 MeV/c.<ref name="Koziol2Möhl2004">{{cite journal\|url=https://cds.cern.ch/record/806278/files/ab-2004-098.pdf\|last1=Koziol\|first1=H.\|last2=Möhl\|first2=D.\|title=The CERN low-energy antiproton programme: the synchrotrons\|journal=Physics Reports\|volume=403-404\|year=2004\|pages=271–280\|issn=0370-1573\|doi=10.1016/j.physrep.2004.09.003\|bibcode = 2004PhR...403..271K }}</ref> The first artificially created [[antimatter]], in the form of ~~[[Antihydrogen\|~~anti-Hydrogen]], was created in a trapping experiment at [[Low Energy Antiproton Ring\|LEAR]] in 1995. However, the first client for antiprotons from the AA had been the [[Intersecting Storage Rings]] (ISR), where proton-antiproton collisions were achieved early in 1981.		From the beginning of the project, the potential of physics with low-energy antiprotons was recognized. A [[Low Energy Antiproton Ring]] (LEAR) was built and received antiprotons from the AA from 1983 on, for deceleration to as low as 100 MeV/c.<ref name="Koziol2Möhl2004">{{cite journal\|url=https://cds.cern.ch/record/806278/files/ab-2004-098.pdf\|last1=Koziol\|first1=H.\|last2=Möhl\|first2=D.\|title=The CERN low-energy antiproton programme: the synchrotrons\|journal=Physics Reports\|volume=403-404\|year=2004\|pages=271–280\|issn=0370-1573\|doi=10.1016/j.physrep.2004.09.003\|bibcode = 2004PhR...403..271K }}</ref> The first artificially created antimatter, in the form of anti-Hydrogen, was created in a trapping experiment at [[Low Energy Antiproton Ring\|LEAR]] in 1995. However, the first client for antiprotons from the AA had been the [[Intersecting Storage Rings]] (ISR), where proton-antiproton collisions were achieved early in 1981.

	== Upgrade of the Antiproton Accumulation system ==		== Upgrade of the Antiproton Accumulation system ==
	To satisfy the need for more antiprotons, the ACOL (Antiproton COLlector) project was conceived in 1983<ref name="Wilson83">{{cite book\|url = https://cds.cern.ch/record/148148/files/CERN-83-10.pdf\|editor-last1= Wilson\|editor-first1=Edmund J. N.\|title=Design study of an antiproton collector for the antiproton accumulator (ACOL)\|issue = CERN-83-10\|year=1983\|publisher = CERN }}</ref> and implemented in 1986 and 1987. The antiproton production (target and target area) was upgraded; the [[Antiproton Collector]] (AC), with an acceptance in transverse and longitudinal ~~[[Phase space\|~~phase-space]] much larger than that of the AA, was built tightly around the AA; and the AA was consequently modified. The AA accumulation rate, previously typically 10<sup>11</sup> antiprotons per day, was thus raised by an order of magnitude, to typically 10<sup>12</sup>.		To satisfy the need for more antiprotons, the ACOL (Antiproton COLlector) project was conceived in 1983<ref name="Wilson83">{{cite book\|url = https://cds.cern.ch/record/148148/files/CERN-83-10.pdf\|editor-last1= Wilson\|editor-first1=Edmund J. N.\|title=Design study of an antiproton collector for the antiproton accumulator (ACOL)\|issue = CERN-83-10\|year=1983\|publisher = CERN }}</ref> and implemented in 1986 and 1987. The antiproton production (target and target area) was upgraded; the [[Antiproton Collector]] (AC), with an acceptance in transverse and longitudinal phase-space much larger than that of the AA, was built tightly around the AA; and the AA was consequently modified. The AA accumulation rate, previously typically 10<sup>11</sup> antiprotons per day, was thus raised by an order of magnitude, to typically 10<sup>12</sup>.

	AC and AA together were referred to as the '''Antiproton Accumulation Complex''' ('''AAC''').<ref name="Jones1986">{{cite book \|chapter=ACOL, CERN's upgrade of the antiproton accelerator complex \|chapter-url = https://cds.cern.ch/record/173156/files/CM-P00064509.pdf\|last1=Jones\|first1=Eifionydd\|editor-last1=Eggert\|editor-first1=Karsten\|editor-last2= Faissner\|editor-first2=Helmut\|editor-last3= Radermacher\|editor-first3=E.\|title=6th Topical Workshop on Proton-Antiproton Collider Physics\|year=1986\|pages=691–704 }}</ref><ref name="Carron1999">{{cite book\|chapter-url = https://cds.cern.ch/record/240246/files/CM-P00058053.pdf\|last1=Carron\|first1=G.\|editor-last1=Rossbach\|editor-first1=J.\|title=15th International Conference on High-Energy Accelerators\|year=1993\|pages=106–108\|chapter=The CERN antiproton accumulator complex (AAC) : current status and operation for the nineties\|publisher = World Scientific \|display-authors=etal}}</ref> The AAC was one of the most highly automated complex of accelerators of its time.<ref name="Chohanvan der Meer1990">{{cite journal\|last1=Chohan\|first1=V.\|author-link1 = Vinod Chohan\|last2=van der Meer\|first2=S.\|author-link2 = Simon van der Meer\|title=Aspects of automation and applications in the CERN antiproton source\|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment\|volume=293\|issue=1–2\|year=1990\|pages=98–102\|issn=0168-9002\|doi=10.1016/0168-9002(90)91408-4\|url = https://cds.cern.ch/record/204708/files/cer-000116409.pdf\|bibcode = 1990NIMPA.293...98C }}</ref>		AC and AA together were referred to as the '''Antiproton Accumulation Complex''' ('''AAC''').<ref name="Jones1986">{{cite book \|chapter=ACOL, CERN's upgrade of the antiproton accelerator complex \|chapter-url = https://cds.cern.ch/record/173156/files/CM-P00064509.pdf\|last1=Jones\|first1=Eifionydd\|editor-last1=Eggert\|editor-first1=Karsten\|editor-last2= Faissner\|editor-first2=Helmut\|editor-last3= Radermacher\|editor-first3=E.\|title=6th Topical Workshop on Proton-Antiproton Collider Physics\|year=1986\|pages=691–704 }}</ref><ref name="Carron1999">{{cite book\|chapter-url = https://cds.cern.ch/record/240246/files/CM-P00058053.pdf\|last1=Carron\|first1=G.\|editor-last1=Rossbach\|editor-first1=J.\|title=15th International Conference on High-Energy Accelerators\|year=1993\|pages=106–108\|chapter=The CERN antiproton accumulator complex (AAC) : current status and operation for the nineties\|publisher = World Scientific \|display-authors=etal}}</ref> The AAC was one of the most highly automated complex of accelerators of its time.<ref name="Chohanvan der Meer1990">{{cite journal\|last1=Chohan\|first1=V.\|author-link1 = Vinod Chohan\|last2=van der Meer\|first2=S.\|author-link2 = Simon van der Meer\|title=Aspects of automation and applications in the CERN antiproton source\|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment\|volume=293\|issue=1–2\|year=1990\|pages=98–102\|issn=0168-9002\|doi=10.1016/0168-9002(90)91408-4\|url = https://cds.cern.ch/record/204708/files/cer-000116409.pdf\|bibcode = 1990NIMPA.293...98C }}</ref>
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	== See also ==		== See also ==
	*[[UA1 experiment]]		*[[UA1\|UA1 experiment]]
	*[[UA2 experiment]]		*[[UA2\|UA2 experiment]]
	*[[Stochastic cooling]]		*[[Stochastic cooling]]
	*[[W and Z bosons]]		*[[W and Z bosons]]
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	{{CERN}}		{{CERN}}

	~~[[Category:CERN accelerators]]~~
	~~[[Category:Particle accelerators]]~~
	[[Category:Accelerator physics]]		[[Category:Accelerator physics]]
	[[Category:~~Particle physics facilities]]~~		[[Category:Decommissioned CERN accelerators]]
	~~[[Category:~~CERN ~~facilities~~]]

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{{Short description|Part of the CERN proton-antiproton collider}}{{sppbarS}}

The '''Antiproton Accumulator''' ('''AA''') was an infrastructure connected to the [[Proton–Antiproton Collider]] (Sp{{overline|p}}S) – a modification of the [[Super Proton Synchrotron]] (SPS) – at [[CERN]].<ref name="BillingeCrowley-Milling1979">{{cite journal|last1=Billinge|first1=R.|last2=Crowley-Milling|first2=M. C.|author-link2=Michael Crowley-Milling |title=The CERN Proton-Antiproton Colliding Beam Facilities|journal=IEEE Transactions on Nuclear Science|volume=26|issue=3|year=1979|pages=2974–2977|issn=0018-9499|doi=10.1109/TNS.1979.4329913|url = https://cds.cern.ch/record/133244/files/cer-000043825.pdf|bibcode = 1979ITNS...26.2974B |s2cid=33805929 }}</ref><ref name="Brianti1983">{{cite journal|url = https://cds.cern.ch/record/149018/files/cer-000060237.pdf|last1=Brianti|first1=G.|title=Experience with the CERN ppbar complex|journal=IEEE Transactions on Nuclear Science|volume=30|issue=4|year=1983|pages=1950–1956|issn=0018-9499|doi=10.1109/TNS.1983.4332685|bibcode = 1983ITNS...30.1950B |s2cid=39013232 }}</ref> The AA was built in 1979 and 1980, for the production and accumulation of [[antiproton]]s.<ref name="KoziolMöhl2004">{{cite journal|url = https://cds.cern.ch/record/806277/files/ab-2004-097.pdf|last1=Koziol|first1=H.|last2=Möhl|first2=D.|title=The CERN antiproton collider programme: accelerators and accumulation rings|journal=Physics Reports|volume=403-404|year=2004|pages=91–106|issn=0370-1573|doi=10.1016/j.physrep.2004.09.001|bibcode = 2004PhR...403...91K }}</ref><ref name="EvansJones1989">{{cite book|last1=Evans|first1=Lyndon|author-link1 = Lyn Evans|last2=Jones|first2=Eifionydd|last3=Koziol|first3=Heribert|editor1-last=Di Lella|editor1-first=Luigi|editor2-last=Altarelli |editor2-first=Guido| editor2-link=Guido Altarelli|title=Proton-antiproton collider physics|volume=4|year=1989|pages=1–44|doi=10.1142/9789814503242_0001|chapter=The CERN ppbar collider |publisher = World Scientific|isbn=9789971505622 }}</ref> In the Sp{{overline|p}}S the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV (later raised to 630 GeV and finally, in a pulsed mode, to 900 GeV). Several experiments recorded data from the collisions, most notably the [[UA1 experiment|UA1]] and [[UA2 experiment]], where the [[W and Z bosons]] were discovered in 1983.

The concept of the project was developed and promoted by [[Carlo Rubbia|C. Rubbia]], for which he received the [[List of Nobel laureates in Physics|Nobel prize in 1984]].<ref>{{cite web |url=http://www.nobelprize.org/nobel_prizes/physics/laureates/1984/press.html |title=Press Release: The 1984 Nobel Prize in Physics |author= |date=17 October 1984 |website=Nobelprize.org |access-date=24 July 2017 }}</ref> He shared the prize with [[Simon van der Meer]], whose invention of the method of [[stochastic cooling]] made large scale production of antiprotons possible for the first time.

== Operation ==
[[File:Overview of the Antiproton Accumulator (AA) at CERN.jpg|thumb|Overview of the Antiproton Accumulator (AA) at [[CERN]]|263x263px]]

Antiprotons were produced by directing an intense proton beam at a momentum of 26 GeV/c from the [[Proton Synchrotron]] (PS) onto a target for production. The emerging burst of antiprotons had a momentum of 3.5 GeV/c, and was selected via a [[spectrometer]], and injected into the AA.<ref name="van der Meer1981">{{cite journal|url=http://accelconf.web.cern.ch/AccelConf/p81/PDF/PAC1981_1994.PDF|last1=van der Meer|first1=S.|author-link1 = Simon van der Meer|title=Stochastic Cooling in the CERN Antiproton Accumulator|journal=IEEE Transactions on Nuclear Science|volume=28|issue=3|year=1981|pages=1994–1998|issn=0018-9499|doi=10.1109/TNS.1981.4331574|bibcode = 1981ITNS...28.1994V }}</ref> The produced antiprotons would have a substantial momentum spread, which was decreased during a 2 s orbit around the AA, using [[Simon van der Meer]]s method of [[stochastic cooling]]. The antiprotons were then trapped using a [[radiofrequency]] system, and moved inwards in the orbit to a stacking region.<ref name=Evans>{{cite book |last1=Evans |first1=Lyndon |last2=Jones |first2=Eifionydd |last3=Koziol |first3=Heribert |year=1989 |chapter=The CERN ppbar Collider |editor1-last=Altarelli |editor1-first=G. |editor2-last=Di Lella |editor2-first=Luigi |title=Proton-Antiproton Collider Physics |series=Advanced Series on Directions in High Energy Physics |volume=4 |publisher=World Scientific Publishing}}</ref> A next burst of antiprotons arrived 2.4 s (the PS cycle time) after the preceding one. This process was repeated during the whole accumulation period, which took about a day. The most intense stack, obtained after many days, would typically contain 5.2·1011 antiprotons.<ref name=Evans />

The dense core of antiprotons was then ejected from the AA, and accelerated to 26 GeV/c, using the PS. Three antiproton bunches were consecutively transferred to the Sp{{overline|p}}S, every 2.4 s.<ref name=Evans /> Just before the antiproton transfer, the PS would already have accelerated and transferred three proton bunches circulating the opposite direction to the antiprotons. When three bunches of antiprotons and three bunches of protons have filled the Sp{{overline|p}}S, the bunches were accelerated to 315 GeV, and the beams were circulated for hours. During this time the AA continued to accumulate, to be ready for the next day's transfer.<ref name=Evans />

== Antimatter experiments ==
{{Antimatter facilities}}[[File:Simon van der Meer in the AA Control Room.jpg|thumb|[[Simon van der Meer]] in the Antiproton Accumulator Control Room, 1984|262x262px]]From the beginning of the project, the potential of physics with low-energy antiprotons was recognized. A [[Low Energy Antiproton Ring]] (LEAR) was built and received antiprotons from the AA from 1983 on, for deceleration to as low as 100 MeV/c.<ref name="Koziol2Möhl2004">{{cite journal|url=https://cds.cern.ch/record/806278/files/ab-2004-098.pdf|last1=Koziol|first1=H.|last2=Möhl|first2=D.|title=The CERN low-energy antiproton programme: the synchrotrons|journal=Physics Reports|volume=403-404|year=2004|pages=271–280|issn=0370-1573|doi=10.1016/j.physrep.2004.09.003|bibcode = 2004PhR...403..271K }}</ref> The first artificially created [[antimatter]], in the form of [[Antihydrogen|anti-Hydrogen]], was created in a trapping experiment at [[Low Energy Antiproton Ring|LEAR]] in 1995. However, the first client for antiprotons from the AA had been the [[Intersecting Storage Rings]] (ISR), where proton-antiproton collisions were achieved early in 1981.

== Upgrade of the Antiproton Accumulation system ==
To satisfy the need for more antiprotons, the ACOL (Antiproton COLlector) project was conceived in 1983<ref name="Wilson83">{{cite book|url = https://cds.cern.ch/record/148148/files/CERN-83-10.pdf|editor-last1= Wilson|editor-first1=Edmund J. N.|title=Design study of an antiproton collector for the antiproton accumulator (ACOL)|issue = CERN-83-10|year=1983|publisher = CERN }}</ref> and implemented in 1986 and 1987. The antiproton production (target and target area) was upgraded; the [[Antiproton Collector]] (AC), with an acceptance in transverse and longitudinal [[Phase space|phase-space]] much larger than that of the AA, was built tightly around the AA; and the AA was consequently modified. The AA accumulation rate, previously typically 1011 antiprotons per day, was thus raised by an order of magnitude, to typically 1012.

AC and AA together were referred to as the '''Antiproton Accumulation Complex''' ('''AAC''').<ref name="Jones1986">{{cite book |chapter=ACOL, CERN's upgrade of the antiproton accelerator complex |chapter-url = https://cds.cern.ch/record/173156/files/CM-P00064509.pdf|last1=Jones|first1=Eifionydd|editor-last1=Eggert|editor-first1=Karsten|editor-last2= Faissner|editor-first2=Helmut|editor-last3= Radermacher|editor-first3=E.|title=6th Topical Workshop on Proton-Antiproton Collider Physics|year=1986|pages=691–704 }}</ref><ref name="Carron1999">{{cite book|chapter-url = https://cds.cern.ch/record/240246/files/CM-P00058053.pdf|last1=Carron|first1=G.|editor-last1=Rossbach|editor-first1=J.|title=15th International Conference on High-Energy Accelerators|year=1993|pages=106–108|chapter=The CERN antiproton accumulator complex (AAC) : current status and operation for the nineties|publisher = World Scientific |display-authors=etal}}</ref> The AAC was one of the most highly automated complex of accelerators of its time.<ref name="Chohanvan der Meer1990">{{cite journal|last1=Chohan|first1=V.|author-link1 = Vinod Chohan|last2=van der Meer|first2=S.|author-link2 = Simon van der Meer|title=Aspects of automation and applications in the CERN antiproton source|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume=293|issue=1–2|year=1990|pages=98–102|issn=0168-9002|doi=10.1016/0168-9002(90)91408-4|url = https://cds.cern.ch/record/204708/files/cer-000116409.pdf|bibcode = 1990NIMPA.293...98C }}</ref>

After the last run of the Sp{{overline|p}}S, in 1991, [[Low Energy Antiproton Ring|LEAR]] remained the sole client of the AAC, and a simpler way to serve low-energy physics was sought. LEAR was converted to become the [[Low Energy Ion Ring]] (LEIR), the AA was dismantled, and the [[Antiproton Collector|AC]] was converted to become the [[Antiproton Decelerator]] (AD).

== See also ==
*[[UA1 experiment]]
*[[UA2 experiment]]
*[[Stochastic cooling]]
*[[W and Z bosons]]
*[[Antiproton Collector]]
*[[Super Proton–Antiproton Synchrotron]]

== References ==
{{reflist}}

{{CERN}}

[[Category:CERN accelerators]]
[[Category:Particle accelerators]]
[[Category:Accelerator physics]]
[[Category:Particle physics facilities]]
[[Category:CERN facilities]]