IPAC2021 - Classification: MC1: Circular and Linear Colliders / A02 Lepton Colliders

Paper	Title	Page
MOXC01	Combined Effect of Beam-Beam Interaction and Beam Coupling Impedance in Future Circular Colliders	25
	Y. Zhang, N. Wang IHEP, Beijing, People’s Republic of China E. Carideo CERN, Geneva, Switzerland M. Migliorati SBAI, Roma, Italy M. Zobov INFN/LNF, Frascati, Italy
	Funding: This work is supported by National Key Programme for S&T Research and Development, China (Grant No. 2016YFA0400400), National Natural Science Foundation of China (No. 11775238, No. 11775239). The future large scale electron-positron colliders, such as FCC-ee in Europe and CEPC in China, will rely on the crab waist collision scheme with a large Piwinski angle. Differently from the past generation colliders both luminosity and beam-beam tune shifts depend on the bunch length in such a collision scheme. In addition, for the future circular colliders with extreme beam parameters in collision several new effects become important such as beamstrahlung, coherent X-Z instability and 3D flip-flop. For all these effects the longitudinal beam dynamics plays an essential role and should be taken into account for the collider luminosity optimization. In this paper we discuss an impact of the longitudinal beam coupling impedance on the collider performance.
	Slides MOXC01 [2.269 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXC01
About •	paper received ※ 17 May 2021 paper accepted ※ 27 July 2021 issue date ※ 17 August 2021
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MOPAB030	Research and Development Progress of CEPC RF Shield Bellows	142
	J.M. Liu, Y.H. Guan, S.M. Liu, B. Tan, P.C. Wang DNSC, Dongguan, People’s Republic of China H. Dong, Y. Ma IHEP, Beijing, People’s Republic of China H.Y. He, T. Huang IHEP CSNS, Guangdong Province, People’s Republic of China
	The circular electron positron collider (CEPC) is a candidate for the next-generation electron positron collider, which can be used to accurately measure the Higgs and electroweak bosons. The RF shield bellow is a vacuum component necessary for the construction of CEPC. Therefore, a RF shield bellow model machine with an elliptical cross-section was designed and processed for technical verification. Based on the traditional interdigital structure, a special contact force testing device was also designed to reduce measurement errors. The on-off status of the circuit was used by the device to determine whether the spring finger was pulled up, thus reducing the influences of human factors in the measurement process. It can be known from the measurement results of the model machine that the contact force of the spring finger is between 120g and 130g, which can satisfy the technical requirements.
	Poster MOPAB030 [1.467 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB030
About •	paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 13 August 2021
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MOPAB032	Estimates of Collective Effects for the FCC-e⁺e⁻ Pre-Booster Ring	148
	O. Etisken, F. Antoniou, K. Oide, Y. Papaphilippou, F. Zimmermann CERN, Geneva, Switzerland A.K. Çiftçi Izmir University of Economics, Balçova/Izmir, Turkey
	The FCC-e⁺e⁻ injector complex needs to produce and to transport high-intensity e⁺ and e^- beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB032
About •	paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021
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MOPAB033	Monochromatization of e⁺e⁻ Colliders with a Large Crossing Angle	152
	V.I. Telnov BINP SB RAS, Novosibirsk, Russia
	The relative center-of-mass energy spread at e⁺e⁻ colliders is much larger than the widths of narrow resonances, which greatly lowers the resonance production rates of J/Psi, Psi-prime, Upsililon(nS), n=1-3. Thus, a significant reduction of the center-of-mass energy spread would open up great opportunities in the search for new physics in rare decays of narrow resonances, the search for new narrow states with small partial e⁺e⁻ width. The existing monochromatization scheme is only suitable for head-on collisions, while e⁺e⁻ colliders with crossing angles (the so-called Crab Waist collision scheme) can provide much higher luminosity. In this report, a new monochromatization method for colliders with a large crossing angle is discussed. The contribution of the beam energy spread to the spread of the center-of-mass energy is canceled by introducing an appropriate energy-angle correlation at the interaction point; the relative RMS mass spread of about (3-5)10^-6 seems possible. Limitations of the proposed method are also considered. This monochromatization scheme is very attractive for the Upsilon-meson region and below. V.I.Telnov, Monochromatization of e⁺e⁻ colliders with a large crossing angle, arXiv:2008.13668
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB033
About •	paper received ※ 22 May 2021 paper accepted ※ 26 May 2021 issue date ※ 31 August 2021
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MOPAB034	VEPP-4M Collider Operation at High Energy	155
	P.A. Piminov, G.N. Baranov, A.V. Bogomyagkov, V.M. Borin, V.L. Dorokhov, S.E. Karnaev, K.Yu. Karyukina, V.A. Kiselev, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, I.A. Morozov, I.N. Okunev, E.A. Simonov, S.V. Sinyatkin, E.V. Starostina, A.N. Zhuravlev BINP SB RAS, Novosibirsk, Russia
	VEPP-4M is an electron positron collider equipped with the universal KEDR detector for HEP experiments in the beam energy range from 1 GeV to 6 GeV. A unique feature of VEPP-4M is the high precision beam energy calibration by resonant polarization technique which allows conducting of interesting experiments despite the low luminosity of the collider. Recently we have started new luminosity acquisition run above 2 GeV. The hadron cross section was measured from 2.3 GeV to 3.5 GeV has been done. The luminosity run for gamma-gamma physics has been started. The luminosity at ψ(1S)-meson has been obtained. For the beam energy calibration the laser polarimeter is used. The paper discusses recent results from VEPP-4M collider.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB034
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021
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TUPAB001	DAΦNE Commissioning for SIDDHARTA-2 Experiment	1322
	C. Milardi, D. Alesini, O.R. Blanco-García, M. Boscolo, B. Buonomo, S. Cantarella, A. D’Uffizi, A. De Santis, C. Di Giulio, G. Di Pirro, A. Drago, L.G. Foggetta, G. Franzini, A. Gallo, S. Incremona, A. Michelotti, L. Pellegrino, L. Piersanti, R. Ricci, U. Rotundo, L. Sabbatini, A. Stecchi, A. Stella, A. Vannozzi, M. Zobov INFN/LNF, Frascati, Italy J. Chavanne, G. Le Bec, P. Raimondi ESRF, Grenoble, France
	DAΦNE, the Frascati lepton collider, has completed the preparatory phase in order to deliver luminosity to the SIDDHARTA-2 detector. DAΦNE colliding rings rely on a new interaction region, which implements the well-established Crab-Waist collision scheme, and includes a low-beta section equipped with newly designed permanent magnet quadrupoles, and vacuum components. Diagnostics tools have been improved, especially the ones used to keep under control the beam-beam interaction. The horizontal feedback in the positron ring has been potentiated in order to achieve a higher positron current. Luminosity diagnostics have been also updated so to be compatible with the new detector design. The commissioning was initially focused on recovering the optimal dynamical vacuum conditions, outlining alignment errors, and optimizing ring optics. For this reason, a detuned optics, featured by relaxed low-b condition at the interaction point and Crab-Waist Sestupoles off, has been applied. In a second stage a low-b optics has been implemented to test collisions with a preliminary setup of the experiment detector. Machine preparation and the first luminosity results are presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB001
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021
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TUPAB002	Round Colliding Beams: Successful Operation Experience	1326
	D.B. Shwartz, O.V. Belikov, D.E. Berkaev, D.B. Burenkov, V.S. Denisov, A.S. Kasaev, A.N. Kirpotin, S.A. Kladov, I. Koop, A.A. Krasnov, A.V. Kupurzhanov, G.Y. Kurkin, M.A. Lyalin, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, Yu.A. Rogovsky, A.M. Semenov, A.I. Senchenko, L.E. Serdakov, D.N. Shatilov, P.Yu. Shatunov, Y.M. Shatunov, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov BINP SB RAS, Novosibirsk, Russia S.A. Kladov, I. Koop, A.A. Krasnov, M.A. Lyalin, E. Perevedentsev, Yu.A. Rogovsky, Y.M. Shatunov, D.B. Shwartz NSU, Novosibirsk, Russia
	VEPP-2000 electron-positron collider operating in the beam energy range of 150-1000 MeV is the only machine originally designed for and successfully exploiting Round Beams Concept. After injection chain upgrade including link to the new BINP injection complex VEPP-2000 proceeded with data taking since 2017 with luminosity limited only by beam-beam effects. At the low energies (300-600 MeV/beam) the novel technique of effective emittance controlled increase by weak coherent beam shaking allowed to suppress the limiting flip-flop effect and resulted in additional luminosity gain factor of 4. The averaged delivered luminosity at the omega-meson production energy (2391 MeV) achieved L = 210³¹cm^-2s⁻¹/IP. At the top energies above nucleon-antinucleon production threshold the stable operation with luminosity of L = 5*10³¹cm^-2s⁻¹/IP resulted in high average data taking rate of 2 pb^-1/day in 2020.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB002
About •	paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 31 August 2021
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TUPAB004	Comparison of Accelerator Codes for Simulation of Lepton Colliders	1334
	L. van Riesen-Haupt, H. Burkhardt, T.H.B. Persson, R. Tomás García CERN, Meyrin, Switzerland
	This paper compares simulation results obtained with SAD, MAD-X and the PTC implementation in MADX for the design studies of the FCC-ee. On-momentum and off-momentum optics are explored for the various programs. Particle tracking with and without synchrotron radiation are used to compare amplitude detuning and emittance. Finally, this paper outlines how well-established SAD features such as tapering have recently been integrated into MADX.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB004
About •	paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 26 August 2021
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TUPAB005	Emittance Estimates for the Future Circular Collider	1338
	L. van Riesen-Haupt, T.K. Charles, R. Tomás García, F. Zimmermann CERN, Meyrin, Switzerland T.K. Charles The University of Liverpool, Liverpool, United Kingdom
	The alignment strategy of the FCC-ee has a large impact on its luminosity. Larger alignment tolerances result in increased coupling and a subsequently higher vertical emittance. At the same time, tighter alignment tolerances around the 100 km ring are a major cost driver. This paper applies analytical emittance estimate methods to the FCC-ee and compares their predictions to data from simulations with different alignment tolerances. These methods can be used to help understand the impact of misalignments of certain magnet groups and to come up with an efficient alignment strategy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB005
About •	paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 26 August 2021
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TUPAB007	A Correction Scheme for the Magnet Imperfection on the CEPC Collider Ring	1346
	B. Wang, Y. Wang, Y. Wei, C.H. Yu, Y. Zhang IHEP, Beijing, People’s Republic of China
	This paper describes the error correction scheme for the CEPC CDR lattice in Higgs mode, which has a small beta function at the interaction point. The low emittance optics has an enhanced sensitivity to the magnet misalignments and field errors, especially for the final focus quadrupole misalignment. The magnet imperfection will cause the closed orbit distortion and optics distortion. The correction scheme for these magnet imperfections includes the closed orbit correction, the dispersion correction, the beta function correction and the betatron coupling correction. The resulting performance and the dynamic aperture for the corrected lattice are studied.
	Poster TUPAB007 [1.075 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB007
About •	paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021
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TUPAB009	SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data	1352
	J. Keintzel, R. Tomás García CERN, Geneva, Switzerland H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang KEK, Ibaraki, Japan
	SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021
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TUPAB010	Impact of Bunch Current on Optics Measurements in SuperKEKB	1356
	J. Keintzel, R. Tomás García, F. Zimmermann CERN, Geneva, Switzerland T. Ishibashi, H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, S. Terui, M. Tobiyama, R.J. Yang, D. Zhou KEK, Ibaraki, Japan
	SuperKEKB has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} and aims at reaching a target luminosity of about 6 × 10³⁵ \si{cm^-2s^-1}. To accomplish this goal it is planned to increase beam currents up to §I{3.6}{A} and §I{2.6}{A} for the positron and the electron ring, respectively. Increasing the beam currents and, in particular, the number of leptons per bunch, can impact the optics parameters obtained by turn-by-turn measurements, such as the betatron tune or phase advance. Optics measurements performed at various bunch currents can give first indications of possible intensity dependent effects. In this paper, the effect of varying bunch current on optics measurements at SuperKEKB is explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010
About •	paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 30 August 2021
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WEXA03	Physics and Technology Challenges in Generating High Intensity Positron Beams
	I. Chaikovska Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	Positron sources are essential to the current and future lepton collider projects (ILC, CLIC, SuperKEKB, FCC-ee, etc.) with challenging critical requirements of high-beam intensity and low emittance necessary to achieve high luminosity. In the conventional positron-generation system, a possible scheme to increase the positron intensity is to increase the incident electron beam power (intensity and/or energy). However, the allowable heat load as well as the thermo-mechanical stresses in the target severely limit the allowable beam power of the incident electrons. The positron source community should consolidate the effort and explore different methods of positron production, both classical techniques and especially novel ones, primarily for future high-energy physics applications requiring orders of magnitude higher intensity than what was demonstrated up to now, and for considering future hadronic applications (including the EIC) requiring both polarization and intensity. The studies should be focused on different source types, targets, capture approaches including the existing limitations and potential for polarized positron production identifying the main axes for future R&D.
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WEXA07	Beam Background Measurements at SuperKEKB/Belle-II in 2020	2532
	H.N. Nakayama, T. Koga KEK, Ibaraki, Japan K. Kojima Nagoya University, Nagoya, Japan A. Natochii, S. Vahsen University of Hawaii, Honolulu,, USA
	The SuperKEKB electron-positron collider began collision operation in 2018 and achieved the world-record luminosity of 2.4x10³⁴~cm^-2s^-1 in June 2020. We pursue higher luminosity by squeezing beam sizes and increasing beam currents. Beam backgrounds induced by stray particles will also increase and might cause severe radiation damage to Belle II detector components and worsen the quality of collected physics data. To mitigate these backgrounds, we have carefully designed our interaction region and installed movable collimators in the machine. We present recent measurements of beam background at SuperKEKB. We have performed dedicated machine studies to measure each background component separately and found that beam-gas scattering and Touschek scattering in the positron ring are the dominant sources of background rates in Belle II. We also present the latest observations of injection background, which determines the timing of a required Belle II data acquisition trigger veto and therefore affects the integrated luminosity. We show the beam background extrapolation toward the expected higher-luminosity operation and our plans for further background mitigation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA07
About •	paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 13 August 2021
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WEPAB029	Challenges for the Interaction Region Design of the Future Circular Collider FCC-ee	2668
	M. Boscolo, A. Ciarma, F. Fransesini, L. Pellegrino INFN/LNF, Frascati, Italy N. Bacchetta INFN- Sez. di Padova, Padova, Italy M. Benedikt, H. Burkhardt, M.A. Jones, R. Kersevan, M. Lueckhof, E. Montbarbon, K. Oide, L. Watrelot, F. Zimmermann CERN, Meyrin, Switzerland L. Brunetti, M. Serluca IN2P3-LAPP, Annecy-le-Vieux, France M. Dam NBI, København, Denmark M. Koratzinos MIT, Cambridge, Massachusetts, USA M. Migliorati INFN-Roma1, Rome, Italy A. Novokhatski, M.K. Sullivan SLAC, Menlo Park, California, USA F. Poirier CNRS - DR17, RENNES, France
	Funding: This work was partially supported by the EC HORIZON 2020 project FCC-IS, grant agreement n.951754, and by the U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-76SF-00515. The FCC-ee is a proposed future high-energy, high-intensity and high precision lepton collider. Here, we present the latest developments for the FCC-ee interaction regions, which shall ensure optimum conditions for the particle physics experiments. We discuss measures of background reduction and a revised interaction region layout including a low impedance compact beam chamber design. We also discuss the possible impact of the radiation generated in the interaction region including beamstrahlung.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB029
About •	paper received ※ 11 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021
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THPAB012	The Magnetic Compensation Scheme of the FCC-ee Detectors	3773
	M. Koratzinos, K. Oide CERN, Meyrin, Switzerland
	A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the beam due to the presence of a large and powerful detector magnet. Indeed, the emittance blow-up of the few meters around the interaction point (IP) at lower energies is comparable to the emittance introduced by the rest of the 100 km ring. Vertical emittance is the single most important factor in achieving high performance (luminosity, in this case) in a modern e⁺ e⁻ storage ring such as the FCC-ee. The design adopted is the simplest possible arrangement that can nevertheless deliver high performance: two additional coils per IP side. The performance achieved is such that vertical emittance blow-up will not be a limiting performance factor even in the case of a ring with four experiments, and even in the most demanding energy regime, that of the Z running (about 45 GeV beam energy).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB012
About •	paper received ※ 10 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021
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THPAB021	Status of VEPP-5 Injection Complex	3796
	F.A. Emanov, A.V. Andrianov, K.V. Astrelina, V.V. Balakin, A.M. Barnyakov, A.M. Batrakov, O.V. Belikov, D.E. Berkaev, Y.M. Boimelshtain, D. Bolkhovityanov, A. Butakov, A.R. Frolov, G.V. Karpov, A.S. Kasaev, A.A. Kondakov, N.Kh. Kot, E.S. Kotov, G.Y. Kurkin, R.M. Lapik, N.N. Lebedev, A.E. Levichev, Yu.I. Maltseva, P.V. Martyshkin, S.V. Motygin, A.A. Murasev, V. Muslivets, D.A. Nikiforov, A.V. Pavlenko, A.M. Pilan, Yu.A. Rogovsky, S.L. Samoylov, A.G. Tribendis, S. Vasiliev, V.D. Yudin BINP SB RAS, Novosibirsk, Russia
	VEPP-5 injection complex is being put into operation as beam source of VEPP-2000 and VEPP-4 colliders at the end of 2016. Since then injection complex demonstrated maximum positron storage rate 1.7·10¹⁰ e+/s and stable operation at the energy of 430 MeV. Latest operation results and prospects are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB021
About •	paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021
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THPAB022	Possibilities for Upgrading to Polarized SuperKEKB	3799
	Z.J. Liptak, M. Kuriki HU/AdSM, Higashi-Hiroshima, Japan J.M. Roney Victoria University, Victoria, B.C., Canada
	The SuperKEKB accelerator is currently in operation in Tsukuba, Japan, with a planned long shutdown in 2026. Among the possible upgrades being considered during this period is the change to a polarized electron beam in the High Energy Ring. Such a change would require modifications in the source generation and transport, geometrical and lattice variations to provide spin rotation, and polarimetry. A Polarized SuperKEKB Working Group has been formed from members of the Belle II experiment and the SuperKEKB accelerator team to investigate the possibilities and challenges of these modifications. This talk lays out the goals of the proposed upgrade, considers the necessary changes to the existing accelerator and their feasibility and lays out the physics motivation behind such an effort.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB022
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 29 August 2021
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THPAB025	A Proposed Beam-Beam Test Facility COMBINE	3802
	E.A. Nissen, G.A. Krafft JLab, Newport News, Virginia, USA J.R. Delayen ODU, Norfolk, Virginia, USA
	Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, license to publish or reproduce this manuscript. The COmpact Machine for Beam-beam Interactions in Non-Equilibrium systems (COMBINE) is a proposed, dedicated, beam-beam test facility. The base design would make use of a pair of identical octagonal rings (2.5 meters per side) one rotated 180 degrees from the other, meeting at their common interaction point. These would be fed by an electron gun producing up to 125 keV electrons. The low energy will allow for beam-beam tune shifts commensurate with existing colliders, some linac-ring type systems, and will also allow for an exploration of the predicted effects of gear-changing, which would be performed using a variable pathlength scheme. The low energy, and small size will allow for cost effective research, simulation code benchmarking, as well as training opportunities for students.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB025
About •	paper received ※ 20 May 2021 paper accepted ※ 01 September 2021 issue date ※ 16 August 2021
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Paper

Title

Page

Combined Effect of Beam-Beam Interaction and Beam Coupling Impedance in Future Circular Colliders

25

Y. Zhang, N. Wang
IHEP, Beijing, People’s Republic of China
E. Carideo
CERN, Geneva, Switzerland
M. Migliorati
SBAI, Roma, Italy
M. Zobov
INFN/LNF, Frascati, Italy

Funding: This work is supported by National Key Programme for S&T Research and Development, China (Grant No. 2016YFA0400400), National Natural Science Foundation of China (No. 11775238, No. 11775239).
The future large scale electron-positron colliders, such as FCC-ee in Europe and CEPC in China, will rely on the crab waist collision scheme with a large Piwinski angle. Differently from the past generation colliders both luminosity and beam-beam tune shifts depend on the bunch length in such a collision scheme. In addition, for the future circular colliders with extreme beam parameters in collision several new effects become important such as beamstrahlung, coherent X-Z instability and 3D flip-flop. For all these effects the longitudinal beam dynamics plays an essential role and should be taken into account for the collider luminosity optimization. In this paper we discuss an impact of the longitudinal beam coupling impedance on the collider performance.

Slides MOXC01 [2.269 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXC01

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paper received ※ 17 May 2021 paper accepted ※ 27 July 2021 issue date ※ 17 August 2021

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MOPAB030

Research and Development Progress of CEPC RF Shield Bellows

142

J.M. Liu, Y.H. Guan, S.M. Liu, B. Tan, P.C. Wang
DNSC, Dongguan, People’s Republic of China
H. Dong, Y. Ma
IHEP, Beijing, People’s Republic of China
H.Y. He, T. Huang
IHEP CSNS, Guangdong Province, People’s Republic of China

The circular electron positron collider (CEPC) is a candidate for the next-generation electron positron collider, which can be used to accurately measure the Higgs and electroweak bosons. The RF shield bellow is a vacuum component necessary for the construction of CEPC. Therefore, a RF shield bellow model machine with an elliptical cross-section was designed and processed for technical verification. Based on the traditional interdigital structure, a special contact force testing device was also designed to reduce measurement errors. The on-off status of the circuit was used by the device to determine whether the spring finger was pulled up, thus reducing the influences of human factors in the measurement process. It can be known from the measurement results of the model machine that the contact force of the spring finger is between 120g and 130g, which can satisfy the technical requirements.

Poster MOPAB030 [1.467 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB030

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paper received ※ 19 May 2021 paper accepted ※ 20 May 2021 issue date ※ 13 August 2021

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MOPAB032

Estimates of Collective Effects for the FCC-e⁺e⁻ Pre-Booster Ring

148

O. Etisken, F. Antoniou, K. Oide, Y. Papaphilippou, F. Zimmermann
CERN, Geneva, Switzerland
A.K. Çiftçi
Izmir University of Economics, Balçova/Izmir, Turkey

The FCC-e⁺e⁻ injector complex needs to produce and to transport high-intensity e⁺ and e^- beams at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: either using the existing SPS machine or designing a completely new ring. The purpose of this paper is to present the studies of collective effects with analytical estimates for both the pre-booster ring design options including space charge (SC), longitudinal micro-wave instability (LMI), transverse mode coupling instability (TMCI), ion effects, electron cloud (e-cloud), coherent synchrotron radiation (CSR), and intra-beam scattering (IBS).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB032

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paper received ※ 17 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021

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MOPAB033

Monochromatization of e⁺e⁻ Colliders with a Large Crossing Angle

152

V.I. Telnov
BINP SB RAS, Novosibirsk, Russia

The relative center-of-mass energy spread at e⁺e⁻ colliders is much larger than the widths of narrow resonances, which greatly lowers the resonance production rates of J/Psi, Psi-prime, Upsililon(nS), n=1-3. Thus, a significant reduction of the center-of-mass energy spread would open up great opportunities in the search for new physics in rare decays of narrow resonances, the search for new narrow states with small partial e⁺e⁻ width. The existing monochromatization scheme is only suitable for head-on collisions, while e⁺e⁻ colliders with crossing angles (the so-called Crab Waist collision scheme) can provide much higher luminosity. In this report, a new monochromatization method for colliders with a large crossing angle is discussed*. The contribution of the beam energy spread to the spread of the center-of-mass energy is canceled by introducing an appropriate energy-angle correlation at the interaction point; the relative RMS mass spread of about (3-5)10^-6 seems possible. Limitations of the proposed method are also considered. This monochromatization scheme is very attractive for the Upsilon-meson region and below.
* V.I.Telnov, Monochromatization of e⁺e⁻ colliders with a large crossing angle, arXiv:2008.13668

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB033

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paper received ※ 22 May 2021 paper accepted ※ 26 May 2021 issue date ※ 31 August 2021

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MOPAB034

VEPP-4M Collider Operation at High Energy

155

P.A. Piminov, G.N. Baranov, A.V. Bogomyagkov, V.M. Borin, V.L. Dorokhov, S.E. Karnaev, K.Yu. Karyukina, V.A. Kiselev, E.B. Levichev, O.I. Meshkov, S.I. Mishnev, I.A. Morozov, I.N. Okunev, E.A. Simonov, S.V. Sinyatkin, E.V. Starostina, A.N. Zhuravlev
BINP SB RAS, Novosibirsk, Russia

VEPP-4M is an electron positron collider equipped with the universal KEDR detector for HEP experiments in the beam energy range from 1 GeV to 6 GeV. A unique feature of VEPP-4M is the high precision beam energy calibration by resonant polarization technique which allows conducting of interesting experiments despite the low luminosity of the collider. Recently we have started new luminosity acquisition run above 2 GeV. The hadron cross section was measured from 2.3 GeV to 3.5 GeV has been done. The luminosity run for gamma-gamma physics has been started. The luminosity at ψ(1S)-meson has been obtained. For the beam energy calibration the laser polarimeter is used. The paper discusses recent results from VEPP-4M collider.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB034

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021

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TUPAB001

DAΦNE Commissioning for SIDDHARTA-2 Experiment

1322

C. Milardi, D. Alesini, O.R. Blanco-García, M. Boscolo, B. Buonomo, S. Cantarella, A. D’Uffizi, A. De Santis, C. Di Giulio, G. Di Pirro, A. Drago, L.G. Foggetta, G. Franzini, A. Gallo, S. Incremona, A. Michelotti, L. Pellegrino, L. Piersanti, R. Ricci, U. Rotundo, L. Sabbatini, A. Stecchi, A. Stella, A. Vannozzi, M. Zobov
INFN/LNF, Frascati, Italy
J. Chavanne, G. Le Bec, P. Raimondi
ESRF, Grenoble, France

DAΦNE, the Frascati lepton collider, has completed the preparatory phase in order to deliver luminosity to the SIDDHARTA-2 detector. DAΦNE colliding rings rely on a new interaction region, which implements the well-established Crab-Waist collision scheme, and includes a low-beta section equipped with newly designed permanent magnet quadrupoles, and vacuum components. Diagnostics tools have been improved, especially the ones used to keep under control the beam-beam interaction. The horizontal feedback in the positron ring has been potentiated in order to achieve a higher positron current. Luminosity diagnostics have been also updated so to be compatible with the new detector design. The commissioning was initially focused on recovering the optimal dynamical vacuum conditions, outlining alignment errors, and optimizing ring optics. For this reason, a detuned optics, featured by relaxed low-b condition at the interaction point and Crab-Waist Sestupoles off, has been applied. In a second stage a low-b optics has been implemented to test collisions with a preliminary setup of the experiment detector. Machine preparation and the first luminosity results are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB001

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021

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TUPAB002

Round Colliding Beams: Successful Operation Experience

1326

D.B. Shwartz, O.V. Belikov, D.E. Berkaev, D.B. Burenkov, V.S. Denisov, A.S. Kasaev, A.N. Kirpotin, S.A. Kladov, I. Koop, A.A. Krasnov, A.V. Kupurzhanov, G.Y. Kurkin, M.A. Lyalin, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, Yu.A. Rogovsky, A.M. Semenov, A.I. Senchenko, L.E. Serdakov, D.N. Shatilov, P.Yu. Shatunov, Y.M. Shatunov, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov
BINP SB RAS, Novosibirsk, Russia
S.A. Kladov, I. Koop, A.A. Krasnov, M.A. Lyalin, E. Perevedentsev, Yu.A. Rogovsky, Y.M. Shatunov, D.B. Shwartz
NSU, Novosibirsk, Russia

VEPP-2000 electron-positron collider operating in the beam energy range of 150-1000 MeV is the only machine originally designed for and successfully exploiting Round Beams Concept. After injection chain upgrade including link to the new BINP injection complex VEPP-2000 proceeded with data taking since 2017 with luminosity limited only by beam-beam effects. At the low energies (300-600 MeV/beam) the novel technique of effective emittance controlled increase by weak coherent beam shaking allowed to suppress the limiting flip-flop effect and resulted in additional luminosity gain factor of 4. The averaged delivered luminosity at the omega-meson production energy (2*391 MeV) achieved L = 2*10³¹cm^-2s⁻¹/IP. At the top energies above nucleon-antinucleon production threshold the stable operation with luminosity of L = 5*10³¹cm^-2s⁻¹/IP resulted in high average data taking rate of 2 pb^-1/day in 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB002

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paper received ※ 20 May 2021 paper accepted ※ 07 June 2021 issue date ※ 31 August 2021

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TUPAB004

Comparison of Accelerator Codes for Simulation of Lepton Colliders

1334

L. van Riesen-Haupt, H. Burkhardt, T.H.B. Persson, R. Tomás García
CERN, Meyrin, Switzerland

This paper compares simulation results obtained with SAD, MAD-X and the PTC implementation in MADX for the design studies of the FCC-ee. On-momentum and off-momentum optics are explored for the various programs. Particle tracking with and without synchrotron radiation are used to compare amplitude detuning and emittance. Finally, this paper outlines how well-established SAD features such as tapering have recently been integrated into MADX.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB004

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paper received ※ 16 May 2021 paper accepted ※ 15 June 2021 issue date ※ 26 August 2021

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TUPAB005

Emittance Estimates for the Future Circular Collider

1338

L. van Riesen-Haupt, T.K. Charles, R. Tomás García, F. Zimmermann
CERN, Meyrin, Switzerland
T.K. Charles
The University of Liverpool, Liverpool, United Kingdom

The alignment strategy of the FCC-ee has a large impact on its luminosity. Larger alignment tolerances result in increased coupling and a subsequently higher vertical emittance. At the same time, tighter alignment tolerances around the 100 km ring are a major cost driver. This paper applies analytical emittance estimate methods to the FCC-ee and compares their predictions to data from simulations with different alignment tolerances. These methods can be used to help understand the impact of misalignments of certain magnet groups and to come up with an efficient alignment strategy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB005

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paper received ※ 16 May 2021 paper accepted ※ 14 June 2021 issue date ※ 26 August 2021

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TUPAB007

A Correction Scheme for the Magnet Imperfection on the CEPC Collider Ring

1346

B. Wang, Y. Wang, Y. Wei, C.H. Yu, Y. Zhang
IHEP, Beijing, People’s Republic of China

This paper describes the error correction scheme for the CEPC CDR lattice in Higgs mode, which has a small beta function at the interaction point. The low emittance optics has an enhanced sensitivity to the magnet misalignments and field errors, especially for the final focus quadrupole misalignment. The magnet imperfection will cause the closed orbit distortion and optics distortion. The correction scheme for these magnet imperfections includes the closed orbit correction, the dispersion correction, the beta function correction and the betatron coupling correction. The resulting performance and the dynamic aperture for the corrected lattice are studied.

Poster TUPAB007 [1.075 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB007

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paper received ※ 14 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021

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TUPAB009

SuperKEKB Optics Measurements Using Turn-by-Turn Beam Position Data

1352

J. Keintzel, R. Tomás García
CERN, Geneva, Switzerland
H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, M. Tobiyama, R.J. Yang
KEK, Ibaraki, Japan

SuperKEKB, an asymmetric electron-positron collider, has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} using crab-waist collision scheme. In order to reach the design value of 6×10³⁵ \si{cm^-2s^-1} a vertical beta function at the interaction point of §I{0.3}{mm} is required, demanding unprecedented optics control. Turn-by-turn beam position data could enable fast optics measurements for rapid identification of unexpected error sources. Experiments exploring various data acquisition techniques at different squeezing steps during commissioning are presented and compared to results obtained from closed orbit distortion.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB009

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 24 August 2021

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TUPAB010

Impact of Bunch Current on Optics Measurements in SuperKEKB

1356

J. Keintzel, R. Tomás García, F. Zimmermann
CERN, Geneva, Switzerland
T. Ishibashi, H. Koiso, G. Mitsuka, A. Morita, K. Ohmi, Y. Ohnishi, H. Sugimoto, S. Terui, M. Tobiyama, R.J. Yang, D. Zhou
KEK, Ibaraki, Japan

SuperKEKB has recently achieved the world record instantaneous luminosity of 2.8 × 10³⁴ \si{cm^-2s^-1} and aims at reaching a target luminosity of about 6 × 10³⁵ \si{cm^-2s^-1}. To accomplish this goal it is planned to increase beam currents up to §I{3.6}{A} and §I{2.6}{A} for the positron and the electron ring, respectively. Increasing the beam currents and, in particular, the number of leptons per bunch, can impact the optics parameters obtained by turn-by-turn measurements, such as the betatron tune or phase advance. Optics measurements performed at various bunch currents can give first indications of possible intensity dependent effects. In this paper, the effect of varying bunch current on optics measurements at SuperKEKB is explored.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB010

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paper received ※ 18 May 2021 paper accepted ※ 10 June 2021 issue date ※ 30 August 2021

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WEXA03

Physics and Technology Challenges in Generating High Intensity Positron Beams

I. Chaikovska
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Positron sources are essential to the current and future lepton collider projects (ILC, CLIC, SuperKEKB, FCC-ee, etc.) with challenging critical requirements of high-beam intensity and low emittance necessary to achieve high luminosity. In the conventional positron-generation system, a possible scheme to increase the positron intensity is to increase the incident electron beam power (intensity and/or energy). However, the allowable heat load as well as the thermo-mechanical stresses in the target severely limit the allowable beam power of the incident electrons. The positron source community should consolidate the effort and explore different methods of positron production, both classical techniques and especially novel ones, primarily for future high-energy physics applications requiring orders of magnitude higher intensity than what was demonstrated up to now, and for considering future hadronic applications (including the EIC) requiring both polarization and intensity. The studies should be focused on different source types, targets, capture approaches including the existing limitations and potential for polarized positron production identifying the main axes for future R&D.

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WEXA07

Beam Background Measurements at SuperKEKB/Belle-II in 2020

2532

H.N. Nakayama, T. Koga
KEK, Ibaraki, Japan
K. Kojima
Nagoya University, Nagoya, Japan
A. Natochii, S. Vahsen
University of Hawaii, Honolulu,, USA

The SuperKEKB electron-positron collider began collision operation in 2018 and achieved the world-record luminosity of 2.4x10³⁴~cm^-2s^-1 in June 2020. We pursue higher luminosity by squeezing beam sizes and increasing beam currents. Beam backgrounds induced by stray particles will also increase and might cause severe radiation damage to Belle II detector components and worsen the quality of collected physics data. To mitigate these backgrounds, we have carefully designed our interaction region and installed movable collimators in the machine. We present recent measurements of beam background at SuperKEKB. We have performed dedicated machine studies to measure each background component separately and found that beam-gas scattering and Touschek scattering in the positron ring are the dominant sources of background rates in Belle II. We also present the latest observations of injection background, which determines the timing of a required Belle II data acquisition trigger veto and therefore affects the integrated luminosity. We show the beam background extrapolation toward the expected higher-luminosity operation and our plans for further background mitigation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA07

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 13 August 2021

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WEPAB029

Challenges for the Interaction Region Design of the Future Circular Collider FCC-ee

2668

M. Boscolo, A. Ciarma, F. Fransesini, L. Pellegrino
INFN/LNF, Frascati, Italy
N. Bacchetta
INFN- Sez. di Padova, Padova, Italy
M. Benedikt, H. Burkhardt, M.A. Jones, R. Kersevan, M. Lueckhof, E. Montbarbon, K. Oide, L. Watrelot, F. Zimmermann
CERN, Meyrin, Switzerland
L. Brunetti, M. Serluca
IN2P3-LAPP, Annecy-le-Vieux, France
M. Dam
NBI, København, Denmark
M. Koratzinos
MIT, Cambridge, Massachusetts, USA
M. Migliorati
INFN-Roma1, Rome, Italy
A. Novokhatski, M.K. Sullivan
SLAC, Menlo Park, California, USA
F. Poirier
CNRS - DR17, RENNES, France

Funding: This work was partially supported by the EC HORIZON 2020 project FCC-IS, grant agreement n.951754, and by the U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-76SF-00515.
The FCC-ee is a proposed future high-energy, high-intensity and high precision lepton collider. Here, we present the latest developments for the FCC-ee interaction regions, which shall ensure optimum conditions for the particle physics experiments. We discuss measures of background reduction and a revised interaction region layout including a low impedance compact beam chamber design. We also discuss the possible impact of the radiation generated in the interaction region including beamstrahlung.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB029

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paper received ※ 11 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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THPAB012

The Magnetic Compensation Scheme of the FCC-ee Detectors

3773

M. Koratzinos, K. Oide
CERN, Meyrin, Switzerland

A crucial part of the design of an FCC-ee detector is the minimisation of the disruption of the beam due to the presence of a large and powerful detector magnet. Indeed, the emittance blow-up of the few meters around the interaction point (IP) at lower energies is comparable to the emittance introduced by the rest of the 100 km ring. Vertical emittance is the single most important factor in achieving high performance (luminosity, in this case) in a modern e⁺ e⁻ storage ring such as the FCC-ee. The design adopted is the simplest possible arrangement that can nevertheless deliver high performance: two additional coils per IP side. The performance achieved is such that vertical emittance blow-up will not be a limiting performance factor even in the case of a ring with four experiments, and even in the most demanding energy regime, that of the Z running (about 45 GeV beam energy).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB012

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paper received ※ 10 May 2021 paper accepted ※ 28 July 2021 issue date ※ 30 August 2021

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THPAB021

Status of VEPP-5 Injection Complex

3796

F.A. Emanov, A.V. Andrianov, K.V. Astrelina, V.V. Balakin, A.M. Barnyakov, A.M. Batrakov, O.V. Belikov, D.E. Berkaev, Y.M. Boimelshtain, D. Bolkhovityanov, A. Butakov, A.R. Frolov, G.V. Karpov, A.S. Kasaev, A.A. Kondakov, N.Kh. Kot, E.S. Kotov, G.Y. Kurkin, R.M. Lapik, N.N. Lebedev, A.E. Levichev, Yu.I. Maltseva, P.V. Martyshkin, S.V. Motygin, A.A. Murasev, V. Muslivets, D.A. Nikiforov, A.V. Pavlenko, A.M. Pilan, Yu.A. Rogovsky, S.L. Samoylov, A.G. Tribendis, S. Vasiliev, V.D. Yudin
BINP SB RAS, Novosibirsk, Russia

VEPP-5 injection complex is being put into operation as beam source of VEPP-2000 and VEPP-4 colliders at the end of 2016. Since then injection complex demonstrated maximum positron storage rate 1.7·10¹⁰ e+/s and stable operation at the energy of 430 MeV. Latest operation results and prospects are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB021

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021

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THPAB022

Possibilities for Upgrading to Polarized SuperKEKB

3799

Z.J. Liptak, M. Kuriki
HU/AdSM, Higashi-Hiroshima, Japan
J.M. Roney
Victoria University, Victoria, B.C., Canada

The SuperKEKB accelerator is currently in operation in Tsukuba, Japan, with a planned long shutdown in 2026. Among the possible upgrades being considered during this period is the change to a polarized electron beam in the High Energy Ring. Such a change would require modifications in the source generation and transport, geometrical and lattice variations to provide spin rotation, and polarimetry. A Polarized SuperKEKB Working Group has been formed from members of the Belle II experiment and the SuperKEKB accelerator team to investigate the possibilities and challenges of these modifications. This talk lays out the goals of the proposed upgrade, considers the necessary changes to the existing accelerator and their feasibility and lays out the physics motivation behind such an effort.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB022

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 29 August 2021

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THPAB025

A Proposed Beam-Beam Test Facility COMBINE

3802

E.A. Nissen, G.A. Krafft
JLab, Newport News, Virginia, USA
J.R. Delayen
ODU, Norfolk, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, license to publish or reproduce this manuscript.
The COmpact Machine for Beam-beam Interactions in Non-Equilibrium systems (COMBINE) is a proposed, dedicated, beam-beam test facility. The base design would make use of a pair of identical octagonal rings (2.5 meters per side) one rotated 180 degrees from the other, meeting at their common interaction point. These would be fed by an electron gun producing up to 125 keV electrons. The low energy will allow for beam-beam tune shifts commensurate with existing colliders, some linac-ring type systems, and will also allow for an exploration of the predicted effects of gear-changing, which would be performed using a variable pathlength scheme. The low energy, and small size will allow for cost effective research, simulation code benchmarking, as well as training opportunities for students.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB025

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paper received ※ 20 May 2021 paper accepted ※ 01 September 2021 issue date ※ 16 August 2021

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