View source for Physics:Intersecting Storage Rings

{{Short description|Particle accelerator at CERN, Switzerland}}
[[File:ISR Surface.jpg|thumb|Some of the buildings associated with the ISR at CERN, Geneva.  The accelerator itself is beneath the curved, tree-covered hill that runs around the ''outside'' of the road.]]
[[File:Intersecting Storage Rings 01.png|thumb|304x304px|Intersecting Storage Rings]]
The '''ISR''' (standing for "'''Intersecting Storage Rings'''") was a [[Physics:Particle accelerator|particle accelerator]] at [[Organization:CERN|CERN]].  It was the world's first [[Physics:Hadron|hadron]] [[Physics:Collider|collider]], and ran from 1971 to 1984, with a maximum [[Physics:Center of mass|center of mass]] [[Physics:Energy|energy]] of 62 GeV.  From its initial startup, the collider itself had the capability to produce particles like the J/ψ and the upsilon, as well as observable jet structure; however, the [[Physics:Particle detector|particle detector]] experiments were not configured to observe events with large [[Physics:Momentum|momentum]] transverse to the [[Physics:Beamline|beamline]], leaving these discoveries to be made at other experiments in the mid-1970s.  Nevertheless, the construction of the ISR involved many advances in [[Physics:Accelerator physics|accelerator physics]], including the first use of [[Physics:Stochastic cooling|stochastic cooling]], and it held the record for [[Physics:Luminosity (scattering theory)|luminosity]] at a hadron collider until surpassed by the [[Physics:Tevatron|Tevatron]] in 2004.<ref name=":1">{{Cite arXiv|last=Hubner|first=Kurt|title=Design and construction of the ISR|year=2012|class=physics.acc-ph|eprint=1206.3948}}</ref><ref name=":2">{{Cite book|last1=Hübner|first1=Kurt|last2=Darriulat|first2=Pierre|last3=Amaldi|first3=Ugo|last4=Bryant|first4=Philip John|date=2012|title=40th Anniversary of the First Proton-Proton Collisions in the CERN Intersecting Storage Rings (ISR)|series=CERN Yellow Reports: Conference Proceedings|url=https://cds.cern.ch/record/1456765|language=en|arxiv=1206.4876|doi=10.5170/CERN-2012-004|isbn=9789290833758}}</ref>

== History ==
The ISR was proposed in 1964 for conducting the head-on proton-proton collisions at a beam energy of 28 GeV; to the study of the new particles created in such collisions.&nbsp; The project was approved within a year. 
[[File:ISR33.jpg|left|thumb|274x274px|A memorial of Werner Heisenberg and of ISR inauguration<ref>{{Cite book|url=https://cds.cern.ch/record/2764883|title=Views of the I4 intersection at the ISR, which is going to host the Split Field Magnet|date=1970}}</ref>]]
The idea of colliding beams was first conceived by a group at [[Organization:Midwestern Universities Research Association|Midwestern Universities Research Association]] (MURA) in the {{wipe|United States}}, as a way to have collisions at an increased [[Physics:Center of mass|center of mass energy]]. The MURA group also invented [[Engineering:Radio frequency|radiofrequency]] (RF) stacking technique to accumulate the proton beams of sufficient intensity.<ref name=":1" />  CERN Council looked into this novel idea in 1957, and an Accelerator Research (AR) group was established to look into the possibilities of having such a facility. AR studied the two-way [[Physics:Fixed-field alternating gradient accelerator|fixed-field alternating gradient]] (FFAG) accelerator for [[Physics:Plasma acceleration|plasma acceleration]] and for an electron collider. In 1960 when the construction of the [[Physics:Proton Synchrotron|Proton Synchrotron]] was completed, the AR group focussed on a proton-proton collider. To check the feasibility and yield of the RF stacking method, the CERN Electron Storage and Accumulation Ring (CESAR) on a smaller scale compared to ISR, was proposed in 1960 and successfully tested by 1964; followed by the official proposal of ISR in the same year, when the AR group presented the technical design report.<ref name=":1" /><ref name=":2" /><ref>{{Cite journal|last=Hübner|first=Kurt|date=March 2012|title=The CERN intersecting storage rings (ISR)|url=http://link.springer.com/10.1140/epjh/e2011-20058-8|journal=The European Physical Journal H|language=en|volume=36|issue=4|pages=509–522|doi=10.1140/epjh/e2011-20058-8|bibcode=2012EPJH...36..509H|s2cid=120690134|issn=2102-6459}}</ref>

In 1971 itself, detectors were set up by 12 experimental teams at five intersecting points of ISR.<ref name=":0">{{Citation|last1=Fabjan|first1=Christian|chapter=The Intersecting Storage Rings (ISR): The First Hadron Collider|date=2015-11-20|chapter-url=https://www.worldscientific.com/doi/10.1142/9789814749145_0004|title=Technology Meets Research|volume=27|pages=87–133|series=Advanced Series on Directions in High Energy Physics|publisher=World Scientific|doi=10.1142/9789814749145_0004|isbn=978-981-4749-13-8|access-date=2021-06-08|last2=Hübner|first2=Kurt|s2cid=125175402 |url=https://cds.cern.ch/record/2312567}}</ref> 

The combination of the CERN Proton Synchrotron (CPS) and ISR also enabled the study of collisions using particles other than the proton, such as the [[Physics:Deuteron|deuteron]], [[Physics:Alpha particle|alpha particles]], and [[Physics:Antiproton|antiprotons]]. <ref>{{Cite journal|last=Hübner|first=Kurt|date=2012-03-01|title=The CERN intersecting storage rings (ISR)|url=https://doi.org/10.1140/epjh/e2011-20058-8|journal=The European Physical Journal H|language=en|volume=36|issue=4|pages=509–522|doi=10.1140/epjh/e2011-20058-8|bibcode=2012EPJH...36..509H|s2cid=120690134|issn=2102-6467}}</ref>

The initial goal and motivation for ISR was the following.

# Finding the proton-proton cross-section for 23–54 GeV energy in the center of mass frame.
# Study of the elastic proton-proton scattering.
# Obtaining production spectra of particles like [[Physics:Pion|pions]] and [[Physics:Kaon|kaons]]. 
# Search for new particles. 

During the end stages of ISR, the beam energies were hiked up to a maximum value of 31.4 GeV.<ref>{{Cite journal|date=1984-12-01|title=Experimental with alpha particles at the CERN intersecting storage rings|url=https://www.sciencedirect.com/science/article/abs/pii/0370157384900115|journal=Physics Reports|language=en|volume=115|issue=1–2|pages=1–91|doi=10.1016/0370-1573(84)90011-5|issn=0370-1573|last1=Faessler|first1=M.|bibcode=1984PhR...115....1F}}</ref><ref>{{Cite journal|date=2004-12-01|title=Physics at the CERN Intersecting Storage Rings (ISR) 1978–1983|url=https://www.sciencedirect.com/science/article/abs/pii/S0370157304003308|journal=Physics Reports|language=en|volume=403–404|pages=165–175|doi=10.1016/j.physrep.2004.08.018|issn=0370-1573|last1=Fabjan|first1=Christian W.|last2=McCubbin|first2=Norman|bibcode=2004PhR...403..165F}}</ref>

== Accelerator ==
[[File:ISR11.jpg|thumb|301x301px|The I4 intersection point at the ISR, which hosted the Split Field Magnet Detector<ref>{{Cite book|url=https://cds.cern.ch/record/2764883|title=Views of the I4 intersection at the ISR, which is going to host the Split Field Magnet|date=1970}}</ref>]]
The accelerator was made up of two magnetic rings (located in France), each with a circumference of 942m. The rings interlaced together such that they would meet at eight intersecting regions for colliding proton beams. The 28 GeV proton beams would come from the CERN Proton Synchrotron (CPS) located about 200 meters away (In Switzerland)<ref name=":0" />

=== Major leaps in accelerator technology ===

==== RF stacking ====
CERN Electron Storage and Accumulation Ring (CESAR) and later ISR were among the first colliders to utilize the RF beam stacking method to increase intensity. In the previous years, the construction of hadron colliders was avoided as it appeared to be unfruitful due to the unavailability of any stacking method. Since ISR, every other collider has utilized the RF stacking method.<ref name=":1" />
[[File:ISR22.jpg|thumb|378x378px]]

==== Schottky noise and stochastic beam cooling ====
[[Shot noise|Schottky noise]] is a signal generated by a finite number of randomly distributed particles in a beam. In 1972 Wolfgang Schnell found the longitudinal and transverse Schottky noise signals at ISR. This made it evident that [[Stochastic|stochastic]] beam damping was possible. And brought up a new window for non-invasive beam diagnostics and the need to have an active cooling system for reducing the size and momentum spread of the beam.<ref name=":3">{{Cite arXiv|eprint=1206.3950|last1=Bryant|first1=P. J.|title=The impact of the ISR on accelerator physics and technology|year=2012|class=physics.acc-ph}}</ref> 
The Schottky signals gave a precise description of how the density of the beam stack varied with betatron frequency. After demonstrating the damping of betatron oscillations, [[Physics:Stochastic cooling|stochastic cooling]] of the antiprotons beams was widely used to enhance [[Physics:Luminosity (scattering theory)|luminosities]] in proton-antiproton collisions. After ISR, the [[Physics:Super Proton–Antiproton Synchrotron|proton-antiproton collider]] at [[Physics:Super Proton Synchrotron|Super Proton Synchrotron]] employed the same technique for increasing luminosities, so did the other colliders such as [[Physics:Tevatron|Tevatron]].<ref name=":3" />

==== Thin-walled vacuum chambers ====
ISR group designed and set-up very large thin-walled [[Engineering:Vacuum chamber|vacuum chambers]] at the intersecting points where detectors were set up. These were made up of [[Chemistry:Tin|tin]] and [[Chemistry:Titanium|titanium]] and inspired the future vacuum chambers.<ref name=":3" />

==== Detector magnets ====
The superconducting solenoid installed at Intersection-1, the Open Axial Field Magnet installed at Intersection-8 and an Air-cored Toroid at Intersection-6, were state-of-the-art magnetic detector systems developed by ISR teams. Almost all collider detectors are now based on larger and improved versions of basic principles of [[Engineering:Magnetic detector|magnetic detectors]] put forth by ISR.<ref name=":3" /> 

==See also==
* [[Physics:Timeline of particle discoveries|Timeline of particle discoveries]]
*[[Physics:Roman pot|Roman pot]]

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20120301105812/http://www.particlephysics.ac.uk/news/picture-of-the-week/picture-archive/cern-s-colliding-beam-pioneers.html ISR startup]
* [http://www.cerncourier.com/main/article/43/5/23 Early history of the ISR]
* [http://cdsweb.cern.ch/record/722481 Picture of the ISR from above] – The large earthen ring with circular roads inside and outside.
{{Hadron colliders}}
{{CERN}}

{{Coord|46|14|05|N|6|02|35|E|region:CH-GE_type:landmark_source:kolossus-dewiki|display=title}}
[[Category:CERN accelerators]]
[[Category:Particle physics facilities]]


{{Sourceattribution|Intersecting Storage Rings}}