Monochromatization

Monochromatization in the context of accelerator physics is a theoretical principle used to increase center-of-mass energy resolution in high-luminosity particle collisions.^[1] The decrease of the collision energy spread can be accomplished without reducing the inherent energy spread of either of the two colliding beams, introducing opposite correlations between spatial position and energy at the interaction point (IP). In beam-optical terms, this can be accomplished through a non-zero dispersion function for both beams of opposite sign at the IP. The dispersion is determined by the respective lattice.^[2]

History

Monochromatization is a technique which has been proposed since a long time for reducing the centre-of-mass energy spread at e⁻e⁺ colliders,^[3] but this has never been used in any operational collider. This technique was first proposed by 1975 by A. Renieri^[3] to improve energy resolution of Italian collider Adone.^[4]

Implementation of a monochromatization scheme has been explored for several past colliders^{[2][3][5][6][7][8][9][10]} such as

• ADONE (National Institute of Nuclear Physics)
• SPEAR (SLAC National Accelerator Laboratory)
• LEP (CERN)

but until now such a scheme has never been applied, or tested, in any operating collider. Nevertheless, studies for the FCC-ee are under development.^[1]

References

1. Valdivia García, M.A; et al. (2016). "Towards A Monochromatization Scheme for Direct Higgs Production at FCC-ee" (PDF). In Petit-Jean-Genaz, C. (ed.). IPAC2016 Proceedings of the 7th International Particle Accelerator. Vol. IPAC2016. doi:10.18429/JACoW-IPAC2016-WEPMW009. ISBN 978-3-95450-147-2.
2. Jowett, J. M. (1994). "Lattice and interaction region design for Tau-Charm factories". Frontiers of Particle Beams: Factories with e⁺e⁻ Rings. Lecture Notes in Physics. Vol. 425. pp. 79–105. Bibcode:1994LNP...425...79J. CiteSeerX 10.1.1.615.8854. doi:10.1007/3540565884_5. ISBN 978-3-540-56588-8.
3. Renieri, A. (1975). "Possibility of Achieving Very High-Energy Resolution in electron-Positron Storage Rings" (PDF). Laboratori Nazionali di Frascati.
4. Bassetti, M.; et al. (1974). "ADONE: Present Status and Experiments" (PDF). In Neal, R. (ed.). Proceedings, 9th International Conference on the High-Energy Accelerators (HEACC 1974) : Stanford, California, May 2-7, 1974. pp. 104–107.
5. Avdienko, A. A.; et al. (1983). "The Project Of Modernization Of The Vepp-4 Storage Ring For Monochromatic Experiments In The Energy Range Of Psi And Upsilon Mesons". In Cole, F. T.; Donaldson, R. (eds.). Proceedings, 12th International Conference on High-Energy Accelerators, HEACC 1983 : Fermilab, Batavia, August 11-16, 1983. pp. 186–189.
6. Wille, K.; Chao, A. W. (1984). "Investigation of a Monochromator Scheme for SPEAR" (PDF). Stanford Linear Accelerator Center.
7. Alexahin, Yu. I.; Dubrovin, A.N.; Zholents, A. A. (1990). "Proposal on a tau charm factory with monochromatization" (PDF). In Mandrillon, P.; Marin, P. (eds.). Proceedings, 2nd European Particle Accelerator Conference (EPAC 90): Nice, France, June 12-16, 1990.
8. Bassetti, M.; Jowett, J. M. (1987). "Improving the Energy Resolution of LEP Experiments" (PDF). In Lindstrom, E. R.; Taylor, L.S. (eds.). Proceedings of the 1987 IEEE Particle Accelerator Conference (PAC1987): Accelerator Engineering and Technology, March 16-19, 1987 Washington, D.C. p. 115.
9. Zholents, A. A. (1992). "Polarized J/ψ mesons at a tau-charm factory with a monochromator scheme" (PDF). European Laboratory for Particle Physics.
10. Faus-Golfe, A.; Le Duff, J. (1996). "Versatile DBA and TBA lattices for a Tau-Charm factory with and without beam monochromatization". Nuclear Instruments and Methods in Physics Research Section A. 372 (1–2): 6–18. Bibcode:1996NIMPA.372....6F. doi:10.1016/0168-9002(95)01275-3.