81 cm Saclay Bubble Chamber
{{Short description|Particle detector built in France, 1960}}
File:81 cm Saclay Bubble Chamber.jpg
File:Last photograph from the Saclay Bubble Chamber.jpg
The 81 cm Saclay Bubble Chamber was a liquid hydrogen bubble chamber built at Saclay, in collaboration with the École Polytechnique (Orsay), to study particle physics.{{cite book |last=Harigel |first=G.G. |last2=Colley |first2=D.C. |last3=Cundy |first3=D.C. |date=July 1994 |title=Bubbles 40: Proceedings of the Conference on the Bubble Chamber and its Contributions to Particle Physics |url=https://cds.cern.ch/record/232652?ln=en |location=Geneva, Switzerland |publisher=North-Holland |page=197 }} The team led by Bernard Gregory completed the construction of the chamber in 1960 and later it was moved to CERN and installed at the Proton Synchrotron (PS).{{cite book |last=Krige |first=Gerhard John |date=1996 |title=History of CERN, v.3 |url=https://cds.cern.ch/record/318964?ln=en |location=Amsterdam |publisher=Elsevier |isbn=978-0444896551}}{{cite magazine |last=Ruhlmann-Kleider |first=Vanina|author1-link= Vanina Ruhlmann-Kleider |last2=Neveu |first2=Monique |last3=Palanque |first3=Serge |last4=DAPNIA |last5=Saclay |date= 1 May 2003 |title=CERN and Saclay: 40 years of co-operation |url=http://cerncourier.com/cws/article/cern/28846 |magazine=CERN Courier |publisher=IOP Publishing |access-date=29 June 2016 }}
A series of experiments began in 1961 which provided data on the properties of hadronic resonances. Firstly, the chamber was irradiated by a beam (rich) of low-energy antiprotons enabling the study of antiproton–proton annihilations at rest. These annihilations generated several bosonic particles and some of them led to the formation of pairs of K mesons.{{cite journal |date=1962 |title=Track Chambers |url=https://cds.cern.ch/record/1479664?ln=en |journal=Annual Report |publisher=CERN |issue=1961 |pages=91–95 |access-date=4 July 2016}} Also, it allowed the study and eventually the discovery of mesonic resonances with emphasis on kaon production. Subsequently, the chamber was exposed to various particles such as π+, π−, K+, K−, and antiprotons, at various momenta up to 10 GeV/c.{{cite report |author=Ella W. D. Steel |date=1976 |title=List of publications covering bubble-chamber experiments carried out at CERN during the period 1960-1974 |url=https://cds.cern.ch/record/185878?ln=en |publisher=CERN |access-date=29 June 2016 }} The experiments with low-energy K− beams resulted in the systematic studies of quasi-elastic reactions on protons directly correlated to strange baryonic resonances. The exposure to higher-energy beams allowed the first evidence of the anti Ξ particle and enabled the discovery and analysis of various mesonic and baryonic resonances.{{cite journal |date=1963 |title=Track Chambers |url=https://cds.cern.ch/record/1479683?ln=en |journal=Annual Report |publisher=CERN |issue=1962 |pages=102–104 |access-date=4 July 2016}} Additionally, in 1963 the chamber started its operation with liquid deuterium, resulting in quasi-elastic reactions of K- on neutrons instead of protons.{{cite journal |date=1964 |title=Track Chambers |url=https://cds.cern.ch/record/1475710?ln=en |journal=Annual Report |publisher=CERN |issue=1963 |pages=74–79 |access-date=4 July 2016|series=Annual Report of the European Organization for Nuclear Research }}
An interesting experiment with a K− beam at rest in hydrogen was also carried out to determine Σ-Λ parity, which turned out to be positive, proving the same nature of these particles. Also, it allowed the study of the leptonic decay of Σ+ and Σ− particles, and confirmed the validity of the ΔQ/ΔS = +1 rule.{{cite journal |last=Montanet |first=Lucien |date=1 June 2003 |title=Charles Peyrou and his impact on physics |url=http://cerncourier.com/cws/article/cern/28868 |journal=CERN Courier |publisher=IOP Publishing |volume=43 |issue=5 |pages=25–28 |access-date=11 July 2016}} It has been assessed that this chamber allowed the identification and study of ten different particles for the first time.{{cite magazine |date=1971 |title=81 cm chamber pensioned off |url=https://cds.cern.ch/record/1729313 |magazine=CERN Courier Volume 11, Number 5 |location=Geneva |publisher=CERN |access-date=30 June 2016 }}
The experiments carried out involved not only most of the CERN member states at the time but also USA, India, Israel, Spain, Czechoslovakia and Poland. Hydrogen liquid filling experiments were: P8, T5, T6, T9, T10, T12, T13, T17, T18, T19, T20, T21, T24, T25, T30, T31, T47, T55, T65, T67, T69, T70, T71, T72, T73, T74, T75, T78, T79, T83, T94, T98, T101, T102, T110, T123, T126, T127, T136, T138, T142, T146, T154, T156, T163, T170, T175, and T206; and using deuterium filling were:T12, T14, T21, T34, T42, T43, T45, T46, T48, T51, T52, T53, T58, T67, T71, T76, T81, T84, T85, T100, T103, T137, T147, T171, and T176.
The chamber operated at CERN on loan from Saclay but in 1966 CERN took full responsibility for the project and a thorough overhaul to the chamber was made.{{cite book |url=https://cds.cern.ch/record/763448?ln=en |title=Assembly of the Saclay Bubble Chamber |date=1966 |publisher=CERN |access-date=29 June 2016 }} After 10 years of magnificent performance the 81 cm Saclay bubble chamber was decommissioned in 1971. It acquired 16.1 million photographs, 5315 km of film, and approximately 150 thousand million bubbles.{{cite journal |date=1972 |title=Introduction by the Director-General of Laboratory I |url=https://cds.cern.ch/record/1479826?ln=en |journal=Annual Report |publisher=CERN |issue=1971 |pages=16 |access-date=4 July 2016}}{{cite book |url=https://cds.cern.ch/record/2010847?ln=en |title=The last photo of the 81 cm hydrogen bubble chamber |date=1971 |publisher=CERN |access-date=29 June 2016 }} It is now situated at the terrace outside Restaurant 1 in CERN.{{cite book |url=https://cds.cern.ch/record/2011260?ln=en |title=Decorating the garden |date=1971 |publisher=CERN |access-date=29 June 2016 }}