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[[File:LEAR_experiment.jpg|thumb|The Low Energy Antiproton Ring (LEAR) at CERN]]
[[File:LEAR_experiment.jpg|thumb|The Low Energy Antiproton Ring (LEAR) at CERN]]
{{Antimatter_facilities}}
{{Antimatter_facilities}}
The '''Low Energy Anti-Proton Ring''' ('''LEAR''') was a particle accelerator at [[CERN]] which operated from 1982 until 1996.<ref name=":0">{{Cite web|title=The Low Energy Antiproton Ring|url=https://home.cern/science/accelerators/low-energy-antiproton-ring|access-date=2021-08-17|website=CERN|language=en}}</ref> The ring was designed to decelerate and store [[antiproton]]s, to study the properties of antimatter and to create atoms of [[antihydrogen]].<ref>{{Cite web|date=2001-02-22|title=The History of Antimatter - The Accelerator Era|url=http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html|access-date=2021-08-17|archive-url=https://web.archive.org/web/20010222023926/http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html|archive-date=2001-02-22}}</ref> Antiprotons for the ring were created by the CERN [[Proton Synchrotron]] via the [[Antiproton Collector]] and the [[Antiproton Accumulator]]. The creation of at least 9 atoms of antihydrogen were confirmed by the [[PS210 experiment]] in 1995.
The '''Low Energy Anti-Proton Ring''' ('''LEAR''') was a particle accelerator at [[CERN]] which operated from 1982 until 1996.<ref name=":0">{{Cite web|title=The Low Energy Antiproton Ring|url=https://home.cern/science/accelerators/low-energy-antiproton-ring|access-date=2021-08-17|website=CERN|language=en}}</ref> The ring was designed to decelerate and store [[antiproton]]s, to study the properties of antimatter and to create atoms of [[antihydrogen]].<ref>{{Cite web|date=2001-02-22|title=The History of Antimatter - The Accelerator Era|url=http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html|access-date=2021-08-17|archive-url=https://web.archive.org/web/20010222023926/http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history02-c.html|archive-date=2001-02-22}}</ref> Antiprotons for the ring were created by the CERN [[Proton Synchrotron]] via the [[Antiproton Collector]] and the [[Antiproton Accumulator]] (AA). The creation of at least nine atoms of antihydrogen were confirmed by the [[PS210 experiment]] in 1995.


== Experimental setup ==
LEAR is a multipurpose storage ring located in the South Hall of the Proton Synchrotron (PS), with a circumference of 78.5 m.<ref name=":1">{{Cite journal |last=Plass |first=Gunther |date=16 May 1980 |title=Design study of a facility for experiments with low energy antiprotons (LEAR) |url=https://cds.cern.ch/record/124681/files/198009172.pdf |journal=CERN/PS/DL 80-7}}</ref><ref name=":2">{{Citation |last=Lefèvre |first=P. |title=The CERN Low Energy Antiproton Ring (LEAR) Project |date=1980 |url=https://doi.org/10.1007/978-3-0348-5540-2_119 |work=11th International Conference on High-Energy Accelerators: Geneva, Switzerland, July 7–11, 1980 |pages=819–824 |editor-last=Newman |editor-first=W. S. |access-date=2023-08-07 |series=Experientia Supplementum |place=Basel |publisher=Birkhäuser |language=en |doi=10.1007/978-3-0348-5540-2_119 |isbn=978-3-0348-5540-2 |last2=Möhl |first2=D. |last3=Plass |first3=G.}}</ref> Four straight sections are alternated with compact 90° bending magnets, along with eight quadrupole doublets. The straight sections each consist of an 8m long section, where equipment such as apparatus for internal beams and electron-cooling can be stored, and two short sections of 1m.<ref name=":2" /> The C-type magnets used are open to the outside of the ring for injection and ejection.<ref name=":3">{{Cite journal |last=Koziol |first=H. |last2=Möhl |first2=D. |date=2004-12-01 |title=The CERN low-energy antiproton programme: the synchrotrons |url=https://www.sciencedirect.com/science/article/pii/S0370157304003618 |journal=Physics Reports |language=en |volume=403-404 |pages=271–280 |doi=10.1016/j.physrep.2004.09.003 |issn=0370-1573}}</ref> The vacuum system used for LEAR is designed for baking at 300°.<ref name=":1" />

Bunches of usually a few 10<sup>9</sup> antiprotons are skimmed off the AA and then decelerated by the PS from 3.5 GeV/c to 0.6 GeV/c.<ref name=":3" /><ref>{{Cite journal |last=Klapisch |first=R |date=1983-01-01 |title=The LEAR Project and Physics with Low Energy Antiprotons at CERN (A Summary) |url=https://iopscience.iop.org/article/10.1088/0031-8949/1983/T5/023 |journal=Physica Scripta |volume=T5 |pages=140–142 |doi=10.1088/0031-8949/1983/T5/023 |issn=0031-8949}}</ref> The bunch was transferred to LEAR where is could be decelerated to a minimum 100 MeV/c or accelerated to generally 1000 MeV/c.<ref name=":3" /> For most experiments, a "beam stretcher mode" was used, where an ultra-slow extraction provided a high-duty (continuous) amount of antiprotons.<ref name=":3" /> Another mode, "internal target", kept a beam circulating for hours, or even days, until most particles were consumed by a gas jet target.<ref>{{Citation |last=Kilian |first=K. |title=Internal Targets for LEAR |date=1984 |url=https://doi.org/10.1007/978-1-4684-8727-5_64 |work=Physics at LEAR with Low-Energy Cooled Antiprotons |pages=677–690 |editor-last=Gastaldi |editor-first=Ugo |access-date=2023-08-07 |series=Ettore Majorana International Science Series |place=Boston, MA |publisher=Springer New York |language=en |doi=10.1007/978-1-4684-8727-5_64 |isbn=978-1-4684-8727-5 |last2=Möhl |first2=D. |last3=Gspann |first3=J. |last4=Poth |first4=H. |editor2-last=Klapisch |editor2-first=Robert}}</ref><ref name=":3" />
[[File:LEAR_magnet.jpg|thumb|LEAR bending magnet quadrant]]
Stochastic cooling is implemented at several stages of the LEAR experimental setup, at different momenta.<ref name=":3" /> The focus of stochastic cooling is to restrict the motion of particles in the beam and control their energies close to a certain value. From 1987, the setup included electron cooling, using the electron cooler from the Initial Cooling Experiment (ICE) to complement the stochastic cooling.<ref>{{Cite journal |last=Poth |first=H. |last2=Schwab |first2=W. |last3=Seligmann |first3=B. |last4=Wörtge |first4=M. |last5=Wolf |first5=A. |last6=Baird |first6=S. |last7=Bosser |first7=J. |last8=Chanel |first8=M. |last9=Haseroth |first9=H. |last10=Hill |first10=C. E. |last11=Ley |first11=R. |last12=Manglunki |first12=D. |last13=Möhl |first13=D. |last14=Tranquille |first14=G. |last15=Vallet |first15=J. L. |date=1990-02-01 |title=Further results and evaluation of electron cooling experiments at LEAR |url=https://www.sciencedirect.com/science/article/pii/016890029091818V |journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment |language=en |volume=287 |issue=1 |pages=328–332 |doi=10.1016/0168-9002(90)91818-V |issn=0168-9002}}</ref><ref>{{Citation |last=Krienen |first=F. |title=Initial Cooling Experiments (ICE) at CERN |date=1980 |url=https://doi.org/10.1007/978-3-0348-5540-2_115 |work=11th International Conference on High-Energy Accelerators: Geneva, Switzerland, July 7–11, 1980 |pages=781–793 |editor-last=Newman |editor-first=W. S. |access-date=2023-08-07 |series=Experientia Supplementum |place=Basel |publisher=Birkhäuser |language=en |doi=10.1007/978-3-0348-5540-2_115 |isbn=978-3-0348-5540-2}}</ref> Using cooling, high quality beams at low energies and low remittances could be produced.<ref name=":3" />

== Conversion to LEIR ==
In 1996, LEAR was converted into the [[Low Energy Ion Ring]], which has since been used in the [[lead]] [[ion]] injection process for the [[Large Hadron Collider]].<ref name=":0" /><ref>{{Cite journal|last=Katarina Anthony|date=2012|title=LEAR: a machine ahead of its time|url=https://cds.cern.ch/record/1454240?ln=en|journal=CERN Bulletin|language=en}}</ref> Low energy antiproton research continues at CERN using the [[Antiproton Decelerator]]. It was built as a successor for LEAR and started operation in 2000.<ref>{{Cite web|title=The Antiproton Decelerator|url=https://home.cern/science/accelerators/antiproton-decelerator|access-date=2021-08-17|website=CERN|language=en}}</ref>
In 1996, LEAR was converted into the [[Low Energy Ion Ring]], which has since been used in the [[lead]] [[ion]] injection process for the [[Large Hadron Collider]].<ref name=":0" /><ref>{{Cite journal|last=Katarina Anthony|date=2012|title=LEAR: a machine ahead of its time|url=https://cds.cern.ch/record/1454240?ln=en|journal=CERN Bulletin|language=en}}</ref> Low energy antiproton research continues at CERN using the [[Antiproton Decelerator]]. It was built as a successor for LEAR and started operation in 2000.<ref>{{Cite web|title=The Antiproton Decelerator|url=https://home.cern/science/accelerators/antiproton-decelerator|access-date=2021-08-17|website=CERN|language=en}}</ref>


Revision as of 13:13, 7 August 2023

"LEAR" redirects here. For the historic Mexican communist organization, see Liga de Escritores y Artistas Revolucionarios.
The Low Energy Antiproton Ring (LEAR) at CERN
Antimatter facilities
Low Energy Antiproton Ring (1982–1996)
Antiproton AccumulatorAntiproton production
Antiproton CollectorDecelerated and stored antiprotons
Antimatter Factory (2000–present)
Antiproton Decelerator (AD)Decelerates antiprotons
Extra Low Energy Antiproton ring (ELENA)Decelerates antiprotons received from AD

The Low Energy Anti-Proton Ring (LEAR) was a particle accelerator at CERN which operated from 1982 until 1996.[1] The ring was designed to decelerate and store antiprotons, to study the properties of antimatter and to create atoms of antihydrogen.[2] Antiprotons for the ring were created by the CERN Proton Synchrotron via the Antiproton Collector and the Antiproton Accumulator (AA). The creation of at least nine atoms of antihydrogen were confirmed by the PS210 experiment in 1995.

Experimental setup

LEAR is a multipurpose storage ring located in the South Hall of the Proton Synchrotron (PS), with a circumference of 78.5 m.[3][4] Four straight sections are alternated with compact 90° bending magnets, along with eight quadrupole doublets. The straight sections each consist of an 8m long section, where equipment such as apparatus for internal beams and electron-cooling can be stored, and two short sections of 1m.[4] The C-type magnets used are open to the outside of the ring for injection and ejection.[5] The vacuum system used for LEAR is designed for baking at 300°.[3]

Bunches of usually a few 109 antiprotons are skimmed off the AA and then decelerated by the PS from 3.5 GeV/c to 0.6 GeV/c.[5][6] The bunch was transferred to LEAR where is could be decelerated to a minimum 100 MeV/c or accelerated to generally 1000 MeV/c.[5] For most experiments, a "beam stretcher mode" was used, where an ultra-slow extraction provided a high-duty (continuous) amount of antiprotons.[5] Another mode, "internal target", kept a beam circulating for hours, or even days, until most particles were consumed by a gas jet target.[7][5]

LEAR bending magnet quadrant

Stochastic cooling is implemented at several stages of the LEAR experimental setup, at different momenta.[5] The focus of stochastic cooling is to restrict the motion of particles in the beam and control their energies close to a certain value. From 1987, the setup included electron cooling, using the electron cooler from the Initial Cooling Experiment (ICE) to complement the stochastic cooling.[8][9] Using cooling, high quality beams at low energies and low remittances could be produced.[5]

Conversion to LEIR

In 1996, LEAR was converted into the Low Energy Ion Ring, which has since been used in the lead ion injection process for the Large Hadron Collider.[1][10] Low energy antiproton research continues at CERN using the Antiproton Decelerator. It was built as a successor for LEAR and started operation in 2000.[11]

References

  1. ^ a b "The Low Energy Antiproton Ring". CERN. Retrieved 2021-08-17.
  2. ^ "The History of Antimatter - The Accelerator Era". 2001-02-22. Archived from the original on 2001-02-22. Retrieved 2021-08-17.
  3. ^ a b Plass, Gunther (16 May 1980). "Design study of a facility for experiments with low energy antiprotons (LEAR)" (PDF). CERN/PS/DL 80-7.
  4. ^ a b Lefèvre, P.; Möhl, D.; Plass, G. (1980), Newman, W. S. (ed.), "The CERN Low Energy Antiproton Ring (LEAR) Project", 11th International Conference on High-Energy Accelerators: Geneva, Switzerland, July 7–11, 1980, Experientia Supplementum, Basel: Birkhäuser, pp. 819–824, doi:10.1007/978-3-0348-5540-2_119, ISBN 978-3-0348-5540-2, retrieved 2023-08-07
  5. ^ a b c d e f g Koziol, H.; Möhl, D. (2004-12-01). "The CERN low-energy antiproton programme: the synchrotrons". Physics Reports. 403–404: 271–280. doi:10.1016/j.physrep.2004.09.003. ISSN 0370-1573.
  6. ^ Klapisch, R (1983-01-01). "The LEAR Project and Physics with Low Energy Antiprotons at CERN (A Summary)". Physica Scripta. T5: 140–142. doi:10.1088/0031-8949/1983/T5/023. ISSN 0031-8949.
  7. ^ Kilian, K.; Möhl, D.; Gspann, J.; Poth, H. (1984), Gastaldi, Ugo; Klapisch, Robert (eds.), "Internal Targets for LEAR", Physics at LEAR with Low-Energy Cooled Antiprotons, Ettore Majorana International Science Series, Boston, MA: Springer New York, pp. 677–690, doi:10.1007/978-1-4684-8727-5_64, ISBN 978-1-4684-8727-5, retrieved 2023-08-07
  8. ^ Poth, H.; Schwab, W.; Seligmann, B.; Wörtge, M.; Wolf, A.; Baird, S.; Bosser, J.; Chanel, M.; Haseroth, H.; Hill, C. E.; Ley, R.; Manglunki, D.; Möhl, D.; Tranquille, G.; Vallet, J. L. (1990-02-01). "Further results and evaluation of electron cooling experiments at LEAR". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 287 (1): 328–332. doi:10.1016/0168-9002(90)91818-V. ISSN 0168-9002.
  9. ^ Krienen, F. (1980), Newman, W. S. (ed.), "Initial Cooling Experiments (ICE) at CERN", 11th International Conference on High-Energy Accelerators: Geneva, Switzerland, July 7–11, 1980, Experientia Supplementum, Basel: Birkhäuser, pp. 781–793, doi:10.1007/978-3-0348-5540-2_115, ISBN 978-3-0348-5540-2, retrieved 2023-08-07
  10. ^ Katarina Anthony (2012). "LEAR: a machine ahead of its time". CERN Bulletin.
  11. ^ "The Antiproton Decelerator". CERN. Retrieved 2021-08-17.


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