IPAC2017 - Classification: 01 Circular and Linear Colliders / A02 Lepton Colliders

Paper	Title	Page
TUZB2	Commissioning Status of High Luminosity Collider Rings for SuperKEKB	1275
	H. Koiso KEK, Ibaraki, Japan
	SuperKEKB project aims to obtain the world's highest luminosity of 8x10³⁵/cm/s, in order to discover new particle physics beyond the Standard Model. Key technologies for the high luminosity are nano-beam scheme at the collision point and high positron and electron stored current with low emittance, which require the significant upgrade of both the injector and the collider rings. Recently commissioning of the renewal collider rings has been performed without final focus magnets and the Belle II detector (Phase 1). This talk gives results of the Phase 1 commissioning and construction status toward the first beam collisions (Phase 2).
	Slides TUZB2 [64.509 MB]
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TUOCB1	Progress in the Design of Beam Optics for FCC-ee Collider Ring*	1281
	K. Oide, K. Ohmi KEK, Ibaraki, Japan M. Benedikt, H. Burkhardt, B.J. Holzer, A. Milanese, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland A.P. Blondel, M. Koratzinos DPNC, Genève, Switzerland A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov BINP SB RAS, Novosibirsk, Russia M. Boscolo INFN/LNF, Frascati (Roma), Italy
	The beam optics for the FCC-ee collider has been updated: (a) the layout is adjusted to a new footprint of FCC-hh, (b) the design around the interaction point is refined considering a number of machine-detecor interface issues, (c) the arc lattice is refined taking realistic magnet designs into account, (d) the β^* and betatron tunes are re-optimized according to recent results of the beam-beam simulations, and more. These changes make the collider design more realistic without performance degradation.
	Slides TUOCB1 [4.891 MB]
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WEPIK001	Advanced Beam Dump for FCC-ee	2906
	A. Apyan ANSL, Yerevan, Armenia B. Goddard, F. Zimmermann CERN, Geneva, Switzerland K. Oide KEK, Ibaraki, Japan
	A modified beam dump for the future electron positron circular collider FCC-ee is discussed. The extraction line with a dilution kicker system distributes bunches at different transverse locations on the face of the beam dump. For a standard absorber the maximum energy deposition of all bunches occurs at the same longitudinal position inside the beam dump. This region experiences an enormous temperature rise compared with the surrounding parts of the beam dump. We propose a novel type of beam dump which spreads out the deposited energy over its whole volume quasi-uniformly, thereby reducing the maximum temperature rise. Results of Monte-Carlo simulations for a multi-material mosaic beam dump and for absorbers with distorted shapes are shown.
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WEPIK004	Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design	2914
	G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani CERN, Geneva, Switzerland N. Bacchetta INFN- Sez. di Padova, Padova, Italy M. Boscolo INFN/LNF, Frascati (Roma), Italy M.K. Sullivan SLAC, Menlo Park, California, USA
	A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.
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WEPIK006	Cancellation of the Leak Field from Lambertson Septum for the Beam Abort System in the SuperKEKB	2918
	N. Iida, M. Kikuchi, K. Kodama, T. Mimashi, T. Mori, Y. Ohnishi, K. Oide, H. Sugimoto, M. Tawada KEK, Ibaraki, Japan
	The first commissioning of SuperKEKB, Phase 1, was performed from February 2016 for five months. A Lambertson septum magnet is utilized to vertically extract the aborted beam, kicked by the horizontal abort kickers upstream into a beam dump. This magnet creates unexpected leak field with a non-negligible skew quadrupole component to the stored beam. Two kinds of skew quadrupole magnets are installed on both sides of the Lambertson septum. One is additional skew windings on the sextupole magnet, and the other is a skew quadrupole magnet with permanent magnets. This paper will report that the cancellations of the leak fields was successful and useful for optics correction.
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WEPIK007	Optics Design and Observation for the Beam Abort System in SuperKEKB HER	2922
	N. Iida, K. Egawa, Y. Enomoto, Y. Funakoshi, M. Kikuchi, T. Mimashi, Y. Ohnishi, K. Oide, Y. Suetsugu KEK, Ibaraki, Japan
	In the first commissioning of SuperKEKB, which is 'Phase 1', the new abort system is tested in the High Energy Ring (HER). There is a risk that aborted beams with low emittance and high current may destroy the window for extraction from beam pipe. In order to enlarge the aborted beam at the window, quadrupole field is applied only for the aborted beam. In the Low Energy Ring (LER), quadrupole pulsed magnets will be installed to enlarge the aborted beam, and in the HER, a pair of identical sextupole magnets is installed between the abort kickers and the extraction window. These sextrupole magnets are connected by I or 'I transformation to cancel the geometrical nonlinearity for the stored beam in the ring. This paper will report the optics design for the abort system of the HER as well as the observation of the aborted beam.
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WEPIK008	Problems in SuperKEKB Vacuum System During the Phase-1 Commissioning and Their Mitigation Measures	2925
	Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui KEK, Ibaraki, Japan
	The first (Phase-1) commissioning of the SuperKEKB, an energy-asymmetric electron-positron collider in KEK, Japan, started in February and ended in June, 2016. The vacuum system of the main ring worked well through the commissioning period as a whole, but experienced several problems, such as the electron cloud effect (ECE) in the positron ring, the pressure bursts accompanying beam losses due to dust particles in the beam pipe, an air leak at a connection flange due to the direct hitting of synchrotron radiation (SR), and so on. Towards the next (Phase-2) commissioning, countermeasures to these problems are taken during the shutdown period. For example, permanent magnets generating axial magnetic fields are attached to beam pipes at drift spaces for the suppression of the ECE. Knockers, which can artificially drop dust particles attached to the top surface in beam pipes by continuous impacts, are prepared to the beam pipes at which the pressure bursts had been frequently observed. Bellows chambers with masks are installed to protect the leaked flange from SR. The problems and their mitigation measures will be summarized in the presentation.
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WEPIK010	Commissioning Status of SuperKEKB Main Ring Magnet System	2933
	M. Masuzawa, T. Adachi, K. Egawa, T. Kawamoto, S. Nakamura, Y. Ohsawa, T. Oki, R. Sugahara, R. Ueki KEK, Ibaraki, Japan
	SuperKEKB is an electron-positron collider, which aims for the very high peak luminosity of 8x10³⁵ cm^-2s^-1 , 40 times higher than that of KEKB. The SuperKEKB Main Ring (MR) system is very large, consisting of more than 1700 water-cooled normal-conducting magnets and about 900 air-cooled normal-conducting magnets. More than 400 magnets and power supplies were newly fabricated, tested and installed for SuperKEKB Phase I beam operation. The MR magnet system worked well, which contributed greatly to the smooth start-up of the MR. Commissioning status of the MR magnet system during SuperKEKB Phase I operation will be reported. Some problems resulting in beam abort will also be reported.
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WEPIK016	CEPC-SppC Towards CDR	2954
	J. Gao IHEP, Beijing, People's Republic of China
	Funding: supported by National Key Programme for S&T Research and Development (2016YFA0400400), National Natural Science Foundation of China (11575218, 11605211, 11605210, 11505198), Key Research Program of Frontier Sciences, CAS, (QYZDJ-SSW-SLH004) and CAS Center for Excellence in Particle Physics (CCEPP) In this paper we will give an introduction to Circular Electron Positron Collider (CEPC). The scientific background, physics goal, the collider design requirements and the conceptual design principle of CEPC are described. On CEPC accelerator, the optimization of parameter designs for CEPC with different energies, machine lengthes, single ring and crab-waist collision partial double ring, advanced partial double partial ring and fully partial double ring options, etc. have been discussed systematically, and compared. CEPC accelerator baseline and alternative designs have been proposed based on the luminosity potential in relation with the design goals. The sub-systems of CEPC, such as collider main ring, booster, electron positron injector, etc. ave also been introduced. The detector and MDI design have been briefly mentioned. Finally, the optimization design of Super Proton-Proton Collider (SppC), its energy and luminosity potentials, in the same tunnel of CEPC are also discussed. The CEPC-SppC Progress Report (2015-2016) has been published.
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WEPIK017	100 km CEPC Parameters and Lattice Design	2958
	D. Wang, T.J. Bian, X. Cui, J. Gao, H. Geng, Q. Qin, B. Sha, N. Wang, Y. Wang, C.H. Yu, J.Y. Zhai, C. Zhang, Y. Zhang IHEP, Beijing, People's Republic of China F. Su Institute of High Energy Physics (IHEP), People's Republic of China
	The 100km double ring configuration with shared su-perconducting RF system has been defined as baseline by the circular electron positron collider (CEPC) steering committee. Based on this new scheme, we will get higher luminosity for Higgs (+170%) keeping the beam power in preliminary conceptual design report (Pre-CDR) or to reduce the beam power (19 MW) while keeping same luminosity. CEPC will be compatible with W and Z ex-periment. The luminosity for Z is designed at the level of 1035 cm^-2s⁻¹. The requirement for the energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The optics of arc and final focus system (FFS) with crab sextupoles has been designed, and also some primary dynamic aperture (DA) results were introduced.
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WEPIK018	Optics Design for Cepc Double Ring Scheme	2962
	Y. Wang, T.J. Bian, J. Gao, H. Geng, B. Sha, D. Wang, C.H. Yu, Y. Zhang IHEP, Beijing, People's Republic of China F. Su Institute of High Energy Physics (IHEP), People's Republic of China
	CEPC is a future Circular Electron and Positron Collider proposed by China to mainly study the Higgs boson. Its baseline scheme is double ring scheme and alternative scheme is partial double ring scheme. This paper will present the optics design for the main ring of double ring scheme. CEPC will also work as W and Z factories. Compatible optics design for W and Z mode will be presented as well.
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WEPIK022	CEPC Booster Lattice Design	2968
SUSPSIK004	use link to see paper's listing under its alternate paper code
	T.J. Bian, X. Cui, J. Gao, C. Zhang IHEP, Beijing, People's Republic of China
	In September 2012, Chinese scientists proposed a Circular Electron Positron Collider(CEPC) at 240 GeV centre of mass for Higgs studies. The CEPC booster(CEPCB) provides 120 GeV electron and positron beams to the CEPC collider for top-up injection. We foucus on the beam dynamic study for CEPCB and analyse the key point of CEPCB lattice design. In this paper, a lattice design with good dynamic aperture is proposed.
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WEPIK023	Sawtooth Effect in CEPC	2971
	H. Geng, J. Gao, B. Sha, D. Wang, Y. Wang, C.H. Yu, Y. Zhang IHEP, Beijing, People's Republic of China
	Funding: This work was supported by National Natural Science Foundation of China, under contract NO. 11405188. CEPC is a circular electron and positron machine designed to study the property of the Higgs boson. The beam energy for CEPC is thus chosen to be 120GeV. At such a high energy, synchrotron radiation has pronounced effect on the beam behavior. In this paper, we will show the synchrotron radiation effect in the CEPC single ring design, namely, the closed orbit, linear optics and dynamic aperture. Analytical analysis will be given trying to explain the phenomenon.
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WEPIK028	Status of the Electron-Positron Collider VEPP-4	2985
	P.A. Piminov BINP SB RAS, Novosibirsk, Russia
	The next phase of the e⁺e⁻ collider VEPP-4 (Budker INP, Novosibirsk) is focused on experiments in the energy range from 4 to 10 GeV (c.m.). To recover the lack of positrons at high energy a new positron source was connected to the collider. The paper discusses the facility performance with new injection and other aspects of experimental study at high energy including laser polarimeter for precise energy calibration.
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WEPIK029	High Luminosity at VEPP-2000 Collider With New Injector	2989
	P.Yu. Shatunov, O.V. Belikov, D.E. Berkaev, K. Gorchakov, A.S. Kasaev, A.N. Kirpotin, I. Koop, A.A. Krasnov, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, D.V. Rabusov, Yu. A. Rogovsky, A.M. Semenov, A.I. Senchenko, Y.M. Shatunov, D.B. Shwartz, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov BINP SB RAS, Novosibirsk, Russia E. Perevedentsev, Yu. A. Rogovsky, A.I. Senchenko, D.B. Shwartz NSU, Novosibirsk, Russia
	VEPP-2000 e⁺e⁻ collider at BINP was commissioned and started data taking with two detectors in 2010 with old injection chain. In the middle energy range, where the luminosity was limited by beam-beam effects, the world record values of beam-beam parameter were achieved, ksi=0.12/IP. At the same time the design luminosity value of L = 10³² cm^-2s⁻¹ at top energy (E = 1 GeV per beam) remained unreachable due to limited e⁺ production rate. The injection chain was significantly upgraded in 2013-2016. The experience of upgraded VEPP-2000 complex operation at top energies with Round Colliding Beams will be presented.
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WEPIK031	Challenges and Status of the Rapid Cycling Top-Up Booster for FCC-ee	2996
	B. Härer, S. Aumon, B.J. Holzer, Y. Papaphilippou, T. Tydecks CERN, Geneva, Switzerland K. Oide KEK, Ibaraki, Japan
	FCC-ee is a 100 km e⁺ e⁻ collider, which is being designed within the Future Circular Collider Study (FCC) for precision studies and rare decay observations in the range of 90 to 350 GeV center-of- mass energy. The beam lifetime will be limited to less than one hour, because of radiative Bhaba scattering and beamstrahlung. In order to keep the luminosity on the high level of 10³⁵ cm^-2s^-1 continuous top-up injection is required. Therefore, besides the collider, that will operate at constant energy, a fast cycling booster synchrotron will be installed in the tunnel. The injection energy to the booster synchrotron will be around 6-20 GeV. Such a small energy together with the large bending radius not only creates an ultra-small beam emittance, but also requires very low magnetic fields close to the limit of technical feasibility. This paper will focus on the challenges and requirements for the top-up booster design arising from low magnetic fields and collective instabilities and present the status of the lattice design.
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WEPIK034	Progress in the FCC-ee Interaction Region Magnet Design	3003
	M. Koratzinos, A.P. Blondel DPNC, Genève, Switzerland M. Benedikt, F. Zimmermann CERN, Geneva, Switzerland E.R. Bielert University of Illinois at Urbana-Champaign, Illinois, USA A.V. Bogomyagkov, S.V. Sinyatkin, P. Vobly BINP SB RAS, Novosibirsk, Russia M. Boscolo INFN/LNF, Frascati (Roma), Italy M. Dam NBI, København, Denmark K. Oide KEK, Ibaraki, Japan
	The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (±15mrad) in a region where the detector solenoid magnetic field is large. Moreover, the very low vertical β^* of the machine necessitates that the final focusing quadrupoles are also inside this high field region. The beams should be screened from the effect of the detector solenoid field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized. We present an update on the subject.
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WEPIK075	Electron Cloud Instability in SuperKEKB Phase I Commissioning	3104
	K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama KEK, Ibaraki, Japan
	Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.
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WEPVA055	Pre Orbit Correction Based on Tunnel Level Measurement in SuperKEKB	3385
	A. Morita, H. Koiso, Y. Ohnishi, H. Sugimoto KEK, Ibaraki, Japan
	The SuperKEKB accelerator tunnel has about 30mm displacement in the vertical direction. From the result of optics correction simulation with the tunnel displacement, it was decided that the beamline components align against the smoothed line of the measured tunnel level in order to save the alignment cost and time. In order to compensate the large tunnel displacement, the pre orbit correction based on the tunnel level measurement is applied at the beginning of the phase-1 commissioning, and the beam circulation is achieved with the small number of magnet adjustments. We report the result of the pre orbit correction.
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Paper

Title

Page

Commissioning Status of High Luminosity Collider Rings for SuperKEKB

1275

H. Koiso
KEK, Ibaraki, Japan

SuperKEKB project aims to obtain the world's highest luminosity of 8x10³⁵/cm/s, in order to discover new particle physics beyond the Standard Model. Key technologies for the high luminosity are nano-beam scheme at the collision point and high positron and electron stored current with low emittance, which require the significant upgrade of both the injector and the collider rings. Recently commissioning of the renewal collider rings has been performed without final focus magnets and the Belle II detector (Phase 1). This talk gives results of the Phase 1 commissioning and construction status toward the first beam collisions (Phase 2).

Slides TUZB2 [64.509 MB]

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TUOCB1

Progress in the Design of Beam Optics for FCC-ee Collider Ring*

1281

K. Oide, K. Ohmi
KEK, Ibaraki, Japan
M. Benedikt, H. Burkhardt, B.J. Holzer, A. Milanese, J. Wenninger, F. Zimmermann
CERN, Geneva, Switzerland
A.P. Blondel, M. Koratzinos
DPNC, Genève, Switzerland
A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov
BINP SB RAS, Novosibirsk, Russia
M. Boscolo
INFN/LNF, Frascati (Roma), Italy

The beam optics for the FCC-ee collider has been updated: (a) the layout is adjusted to a new footprint of FCC-hh, (b) the design around the interaction point is refined considering a number of machine-detecor interface issues, (c) the arc lattice is refined taking realistic magnet designs into account, (d) the β^* and betatron tunes are re-optimized according to recent results of the beam-beam simulations, and more. These changes make the collider design more realistic without performance degradation.

Slides TUOCB1 [4.891 MB]

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WEPIK001

Advanced Beam Dump for FCC-ee

2906

A. Apyan
ANSL, Yerevan, Armenia
B. Goddard, F. Zimmermann
CERN, Geneva, Switzerland
K. Oide
KEK, Ibaraki, Japan

A modified beam dump for the future electron positron circular collider FCC-ee is discussed. The extraction line with a dilution kicker system distributes bunches at different transverse locations on the face of the beam dump. For a standard absorber the maximum energy deposition of all bunches occurs at the same longitudinal position inside the beam dump. This region experiences an enormous temperature rise compared with the surrounding parts of the beam dump. We propose a novel type of beam dump which spreads out the deposited energy over its whole volume quasi-uniformly, thereby reducing the maximum temperature rise. Results of Monte-Carlo simulations for a multi-material mosaic beam dump and for absorbers with distorted shapes are shown.

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WEPIK004

Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design

2914

G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani
CERN, Geneva, Switzerland
N. Bacchetta
INFN- Sez. di Padova, Padova, Italy
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
M.K. Sullivan
SLAC, Menlo Park, California, USA

A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.

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WEPIK006

Cancellation of the Leak Field from Lambertson Septum for the Beam Abort System in the SuperKEKB

2918

N. Iida, M. Kikuchi, K. Kodama, T. Mimashi, T. Mori, Y. Ohnishi, K. Oide, H. Sugimoto, M. Tawada
KEK, Ibaraki, Japan

The first commissioning of SuperKEKB, Phase 1, was performed from February 2016 for five months. A Lambertson septum magnet is utilized to vertically extract the aborted beam, kicked by the horizontal abort kickers upstream into a beam dump. This magnet creates unexpected leak field with a non-negligible skew quadrupole component to the stored beam. Two kinds of skew quadrupole magnets are installed on both sides of the Lambertson septum. One is additional skew windings on the sextupole magnet, and the other is a skew quadrupole magnet with permanent magnets. This paper will report that the cancellations of the leak fields was successful and useful for optics correction.

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WEPIK007

Optics Design and Observation for the Beam Abort System in SuperKEKB HER

2922

N. Iida, K. Egawa, Y. Enomoto, Y. Funakoshi, M. Kikuchi, T. Mimashi, Y. Ohnishi, K. Oide, Y. Suetsugu
KEK, Ibaraki, Japan

In the first commissioning of SuperKEKB, which is 'Phase 1', the new abort system is tested in the High Energy Ring (HER). There is a risk that aborted beams with low emittance and high current may destroy the window for extraction from beam pipe. In order to enlarge the aborted beam at the window, quadrupole field is applied only for the aborted beam. In the Low Energy Ring (LER), quadrupole pulsed magnets will be installed to enlarge the aborted beam, and in the HER, a pair of identical sextupole magnets is installed between the abort kickers and the extraction window. These sextrupole magnets are connected by I or 'I transformation to cancel the geometrical nonlinearity for the stored beam in the ring. This paper will report the optics design for the abort system of the HER as well as the observation of the aborted beam.

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WEPIK008

Problems in SuperKEKB Vacuum System During the Phase-1 Commissioning and Their Mitigation Measures

2925

Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui
KEK, Ibaraki, Japan

The first (Phase-1) commissioning of the SuperKEKB, an energy-asymmetric electron-positron collider in KEK, Japan, started in February and ended in June, 2016. The vacuum system of the main ring worked well through the commissioning period as a whole, but experienced several problems, such as the electron cloud effect (ECE) in the positron ring, the pressure bursts accompanying beam losses due to dust particles in the beam pipe, an air leak at a connection flange due to the direct hitting of synchrotron radiation (SR), and so on. Towards the next (Phase-2) commissioning, countermeasures to these problems are taken during the shutdown period. For example, permanent magnets generating axial magnetic fields are attached to beam pipes at drift spaces for the suppression of the ECE. Knockers, which can artificially drop dust particles attached to the top surface in beam pipes by continuous impacts, are prepared to the beam pipes at which the pressure bursts had been frequently observed. Bellows chambers with masks are installed to protect the leaked flange from SR. The problems and their mitigation measures will be summarized in the presentation.

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WEPIK010

Commissioning Status of SuperKEKB Main Ring Magnet System

2933

M. Masuzawa, T. Adachi, K. Egawa, T. Kawamoto, S. Nakamura, Y. Ohsawa, T. Oki, R. Sugahara, R. Ueki
KEK, Ibaraki, Japan

SuperKEKB is an electron-positron collider, which aims for the very high peak luminosity of 8x10³⁵ cm^-2s^-1 , 40 times higher than that of KEKB. The SuperKEKB Main Ring (MR) system is very large, consisting of more than 1700 water-cooled normal-conducting magnets and about 900 air-cooled normal-conducting magnets. More than 400 magnets and power supplies were newly fabricated, tested and installed for SuperKEKB Phase I beam operation. The MR magnet system worked well, which contributed greatly to the smooth start-up of the MR. Commissioning status of the MR magnet system during SuperKEKB Phase I operation will be reported. Some problems resulting in beam abort will also be reported.

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WEPIK016

CEPC-SppC Towards CDR

2954

J. Gao
IHEP, Beijing, People's Republic of China

Funding: supported by National Key Programme for S&T Research and Development (2016YFA0400400), National Natural Science Foundation of China (11575218, 11605211, 11605210, 11505198), Key Research Program of Frontier Sciences, CAS, (QYZDJ-SSW-SLH004) and CAS Center for Excellence in Particle Physics (CCEPP)
In this paper we will give an introduction to Circular Electron Positron Collider (CEPC). The scientific background, physics goal, the collider design requirements and the conceptual design principle of CEPC are described. On CEPC accelerator, the optimization of parameter designs for CEPC with different energies, machine lengthes, single ring and crab-waist collision partial double ring, advanced partial double partial ring and fully partial double ring options, etc. have been discussed systematically, and compared. CEPC accelerator baseline and alternative designs have been proposed based on the luminosity potential in relation with the design goals. The sub-systems of CEPC, such as collider main ring, booster, electron positron injector, etc. ave also been introduced. The detector and MDI design have been briefly mentioned. Finally, the optimization design of Super Proton-Proton Collider (SppC), its energy and luminosity potentials, in the same tunnel of CEPC are also discussed. The CEPC-SppC Progress Report (2015-2016) has been published.

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WEPIK017

100 km CEPC Parameters and Lattice Design

2958

D. Wang, T.J. Bian, X. Cui, J. Gao, H. Geng, Q. Qin, B. Sha, N. Wang, Y. Wang, C.H. Yu, J.Y. Zhai, C. Zhang, Y. Zhang
IHEP, Beijing, People's Republic of China
F. Su
Institute of High Energy Physics (IHEP), People's Republic of China

The 100km double ring configuration with shared su-perconducting RF system has been defined as baseline by the circular electron positron collider (CEPC) steering committee. Based on this new scheme, we will get higher luminosity for Higgs (+170%) keeping the beam power in preliminary conceptual design report (Pre-CDR) or to reduce the beam power (19 MW) while keeping same luminosity. CEPC will be compatible with W and Z ex-periment. The luminosity for Z is designed at the level of 1035 cm^-2s⁻¹. The requirement for the energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The optics of arc and final focus system (FFS) with crab sextupoles has been designed, and also some primary dynamic aperture (DA) results were introduced.

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WEPIK018

Optics Design for Cepc Double Ring Scheme

2962

Y. Wang, T.J. Bian, J. Gao, H. Geng, B. Sha, D. Wang, C.H. Yu, Y. Zhang
IHEP, Beijing, People's Republic of China
F. Su
Institute of High Energy Physics (IHEP), People's Republic of China

CEPC is a future Circular Electron and Positron Collider proposed by China to mainly study the Higgs boson. Its baseline scheme is double ring scheme and alternative scheme is partial double ring scheme. This paper will present the optics design for the main ring of double ring scheme. CEPC will also work as W and Z factories. Compatible optics design for W and Z mode will be presented as well.

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WEPIK022

CEPC Booster Lattice Design

2968

SUSPSIK004

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T.J. Bian, X. Cui, J. Gao, C. Zhang
IHEP, Beijing, People's Republic of China

In September 2012, Chinese scientists proposed a Circular Electron Positron Collider(CEPC) at 240 GeV centre of mass for Higgs studies. The CEPC booster(CEPCB) provides 120 GeV electron and positron beams to the CEPC collider for top-up injection. We foucus on the beam dynamic study for CEPCB and analyse the key point of CEPCB lattice design. In this paper, a lattice design with good dynamic aperture is proposed.

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WEPIK023

Sawtooth Effect in CEPC

2971

H. Geng, J. Gao, B. Sha, D. Wang, Y. Wang, C.H. Yu, Y. Zhang
IHEP, Beijing, People's Republic of China

Funding: This work was supported by National Natural Science Foundation of China, under contract NO. 11405188.
CEPC is a circular electron and positron machine designed to study the property of the Higgs boson. The beam energy for CEPC is thus chosen to be 120GeV. At such a high energy, synchrotron radiation has pronounced effect on the beam behavior. In this paper, we will show the synchrotron radiation effect in the CEPC single ring design, namely, the closed orbit, linear optics and dynamic aperture. Analytical analysis will be given trying to explain the phenomenon.

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WEPIK028

Status of the Electron-Positron Collider VEPP-4

2985

P.A. Piminov
BINP SB RAS, Novosibirsk, Russia

The next phase of the e⁺e⁻ collider VEPP-4 (Budker INP, Novosibirsk) is focused on experiments in the energy range from 4 to 10 GeV (c.m.). To recover the lack of positrons at high energy a new positron source was connected to the collider. The paper discusses the facility performance with new injection and other aspects of experimental study at high energy including laser polarimeter for precise energy calibration.

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WEPIK029

High Luminosity at VEPP-2000 Collider With New Injector

2989

P.Yu. Shatunov, O.V. Belikov, D.E. Berkaev, K. Gorchakov, A.S. Kasaev, A.N. Kirpotin, I. Koop, A.A. Krasnov, A.P. Lysenko, S.V. Motygin, E. Perevedentsev, V.P. Prosvetov, D.V. Rabusov, Yu. A. Rogovsky, A.M. Semenov, A.I. Senchenko, Y.M. Shatunov, D.B. Shwartz, M.V. Timoshenko, I.M. Zemlyansky, Yu.M. Zharinov
BINP SB RAS, Novosibirsk, Russia
E. Perevedentsev, Yu. A. Rogovsky, A.I. Senchenko, D.B. Shwartz
NSU, Novosibirsk, Russia

VEPP-2000 e⁺e⁻ collider at BINP was commissioned and started data taking with two detectors in 2010 with old injection chain. In the middle energy range, where the luminosity was limited by beam-beam effects, the world record values of beam-beam parameter were achieved, ksi=0.12/IP. At the same time the design luminosity value of L = 10³² cm^-2s⁻¹ at top energy (E = 1 GeV per beam) remained unreachable due to limited e⁺ production rate. The injection chain was significantly upgraded in 2013-2016. The experience of upgraded VEPP-2000 complex operation at top energies with Round Colliding Beams will be presented.

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WEPIK031

Challenges and Status of the Rapid Cycling Top-Up Booster for FCC-ee

2996

B. Härer, S. Aumon, B.J. Holzer, Y. Papaphilippou, T. Tydecks
CERN, Geneva, Switzerland
K. Oide
KEK, Ibaraki, Japan

FCC-ee is a 100 km e⁺ e⁻ collider, which is being designed within the Future Circular Collider Study (FCC) for precision studies and rare decay observations in the range of 90 to 350 GeV center-of- mass energy. The beam lifetime will be limited to less than one hour, because of radiative Bhaba scattering and beamstrahlung. In order to keep the luminosity on the high level of 10³⁵ cm^-2s^-1 continuous top-up injection is required. Therefore, besides the collider, that will operate at constant energy, a fast cycling booster synchrotron will be installed in the tunnel. The injection energy to the booster synchrotron will be around 6-20 GeV. Such a small energy together with the large bending radius not only creates an ultra-small beam emittance, but also requires very low magnetic fields close to the limit of technical feasibility. This paper will focus on the challenges and requirements for the top-up booster design arising from low magnetic fields and collective instabilities and present the status of the lattice design.

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WEPIK034

Progress in the FCC-ee Interaction Region Magnet Design

3003

M. Koratzinos, A.P. Blondel
DPNC, Genève, Switzerland
M. Benedikt, F. Zimmermann
CERN, Geneva, Switzerland
E.R. Bielert
University of Illinois at Urbana-Champaign, Illinois, USA
A.V. Bogomyagkov, S.V. Sinyatkin, P. Vobly
BINP SB RAS, Novosibirsk, Russia
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
M. Dam
NBI, København, Denmark
K. Oide
KEK, Ibaraki, Japan

The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (±15mrad) in a region where the detector solenoid magnetic field is large. Moreover, the very low vertical β^* of the machine necessitates that the final focusing quadrupoles are also inside this high field region. The beams should be screened from the effect of the detector solenoid field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized. We present an update on the subject.

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WEPIK075

Electron Cloud Instability in SuperKEKB Phase I Commissioning

3104

K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.

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WEPVA055

Pre Orbit Correction Based on Tunnel Level Measurement in SuperKEKB

3385

A. Morita, H. Koiso, Y. Ohnishi, H. Sugimoto
KEK, Ibaraki, Japan

The SuperKEKB accelerator tunnel has about 30mm displacement in the vertical direction. From the result of optics correction simulation with the tunnel displacement, it was decided that the beamline components align against the smoothed line of the measured tunnel level in order to save the alignment cost and time. In order to compensate the large tunnel displacement, the pre orbit correction based on the tunnel level measurement is applied at the beginning of the phase-1 commissioning, and the beam circulation is achieved with the small number of magnet adjustments. We report the result of the pre orbit correction.

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