SuperKEKB operation using crab waist collision scheme

Ohnishi, Y.; Abe, T.; Akai, K.; Arimoto, Y.; Egawa, K.; Enomoto, S.; Fukuma, H.; Funakoshi, Y.; Furukawa, K.; Iida, N.; Ikeda, H.; Ishibashi, Takuya; Iwabuchi, Sho; Kaji, Hiroshi; Kamitani, T.; Kimura, Takashi; Kikuchi, M.; Kobayashi, T.; Kodama, Koya; Koiso, H.; Masuzawa, M.; Mimashi, T.; Mitsuka, G.; Miyahara, F.; Miyajima, Tsukasa; Mori, Takashi; Morita, Akio; Nakamura, Shu; Nakamura, Tatsuro; Nakanishi, Koichi; Nishiwaki, Michiru; Ogasawara, Sadao; Ohmi, K.; Ohuchi, N.; Oide, K.; Oki, Toshiyuki; Rehman, Muhammad Abdul; Seimiya, Yuji; Shibata, K.; Suetsugu, Y.; Sugimoto, Hiroshi; Sugimura, Hitoshi; Tawada, M.; Terui, Shinji; Tobiyama, M.; Ueki, Ryuichi; Wang, X.; Watanabe, K.; Yang, R. X.; Yoshimoto, S.; Yoshimoto, Takashi; Zhou, Demin; Zhou, Xiangyu; Zong, Zhaowen

doi:10.1140/epjp/s13360-021-01979-8

“…As already discussed in detail in [15], the beam-beam interaction in FCC-ee contains a combination of several extreme beam parameters, such as very small emittances, small beta functions in the interaction points, a large Piwinski angle combined with the crab waist collision scheme [33,34], and very high intensity, that give rise to several new important effects, such as beamstrahlung [10], coherent X-Z instability [11] and 3D flip-flop [12]. In turn, since the luminosity and both vertical and horizontal beam-beam tune shifts depend on the bunch length, taking into account the longitudinal impedance makes the beam dynamics in FCC-ee even more complicated [13,15,35,36].…”

Section: Beam-beam With 4 Ipsmentioning

confidence: 99%

Impedance modelling and collective effects in the Future Circular e+e− Collider with 4 IPs

Migliorati

¹

,

Antuono

²

,

Carideo

³

et al. 2022

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The FCC-ee impedance model is being constantly updated closely following the vacuum chamber design and parameters evolution. In particular, at present, a thicker NEG coating of 150 nm (instead of previous 100 nm) has been suggested by the vacuum experts, and a more realistic impedance model of the bellows has been investigated. Moreover, also the transverse impedance has been updated by considering the same sources as for the longitudinal case. Therefore, the FCC-ee impedance database is getting more complete and the impedance model is being refined. In this paper we describe the presently available machine coupling impedance in both longitudinal and transverse planes, and study the impedance-driven single bunch instabilities (with and without beam-beam interaction) for the new FCC-ee parameter set with 4 interaction points (IPs). The results are compared with the previously obtained ones and a further possible mitigation of the beam-beam head-tail instability (X-Z instability) is proposed.

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“…As already discussed in detail in [15], the beam-beam interaction in FCC-ee contains a combination of several extreme beam parameters, such as very small emittances, small beta functions in the interaction points, a large Piwinski angle combined with the crab waist collision scheme [33], [34], and very high intensity, that give rise to several new important effects, such as beamstrahlung [10], coherent X-Z instability [11] and 3D flip-flop [12]. In turn, since the luminosity and both vertical and horizontal beam-beam tune shifts depend on the bunch length, taking into account the longitudinal impedance makes the beam dynamics in FCC-ee even more complicated [15], [13], [35], [36].…”

Section: Beam-beam With 4 Ipsmentioning

confidence: 99%

Impedance modelling and collective effects in the Future Circular e$^+$e$^-$ Collider with 4 IPs

Migliorati¹,

Antuono²,

Carideo³

et al. 2022

Preprint

0

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The FCC-ee impedance model is being constantly updated closely following the vacuum chamber design and parameters evolution. In particular, at present, a thicker NEG coating of 150 nm (instead of previous 100 nm) has been suggested by the vacuum experts, and a more realistic impedance model of the bellows has been investigated. Moreover, also the transverse impedance has been updated by considering the same sources as for the longitudinal case. Therefore, the FCC-ee impedance database is getting more complete and the impedance model is being refined. In this paper we describe the presently available machine coupling impedance in both longitudinal and transverse planes, and study the impedance-driven single bunch instabilities (with and without beam-beam interaction) for the new FCC-ee parameter set with 4 interaction points (IPs). The results are compared with the previously obtained ones and a further possible mitigation of the beam-beam head-tail instability (X-Z instability) is proposed.

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“…A brief summary is presented in section 4. The CW collision scheme [5,6] was implemented in both the LER and the HER in 2020 to suppress beam-beam blowup and beam-tail generation [7]. The CW scheme is realized by applying fields of various strength to sextupole magnets (SLYs) used in the vertical local chromaticity correction (Y-LCC), as shown in figure 1.…”

Section: Introductionmentioning

confidence: 99%

Beam optics distortion caused by orbit deviation at strong sextupole magnets in SuperKEKB

Sugimoto,

Ohnishi,

Morita

et al. 2024

J. Inst.

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0

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The SuperKEKB is an electron-positron double-ring asymmetric-energy collider at the High Energy Accelerator Research Organization (KEK) in Japan. It uses a novel collision method referred to as the nano-beam scheme to avoid the so-called hourglass effect. The highest peak luminosity achieved thus far is 4.65 × 1034 cm-2s-1, which was reached on June 8th, 2022. Although the SuperKEKB holds the record for the world's highest instantaneous luminosity, several unresolved issues prevent a further increase in luminosity. One of the major issues is inadequate stability and reproducibility of the beam orbit and optics. This paper discusses optics distortion caused by orbit deviation near strong sextupole magnets. Numerical estimations indicate that a horizontal orbit deviation of a few tens of micrometers induces a sizable distortion of the optical functions at the interaction point. Analyses of the amount of betatron tune feedback and orbit at sextupole magnets used for crab waist and vertical local chromaticity correction indicate that the beam-current dependence of the vertical tune shift is attributable to the change of the beam orbit at the sextupoles. The orbit fluctuation at the sextupoles causes beta-beating and makes stable operation at high beam currents more difficult. The results show that orbit tuning at the sextupoles improves both the injection efficiency and the detector background level. Optics deterioration within a few days is another urgent issue in high-beam-current operation. A vertical orbit change of a few tens of microns at sextupole magnets installed in arc cells is a matter of concern according to numerical estimations.

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SuperKEKB operation using crab waist collision scheme

Cited by 9 publications

References 11 publications

Impedance modelling and collective effects in the Future Circular e+e− Collider with 4 IPs

Impedance modelling and collective effects in the Future Circular e+e− Collider with 4 IPs

Impedance modelling and collective effects in the Future Circular e$^+$e$^-$ Collider with 4 IPs

Beam optics distortion caused by orbit deviation at strong sextupole magnets in SuperKEKB

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