SuperKEKB Injector Linac towards Υ(6S) Collision

[Overview] [Resonaces] [Parameters] [Schedule] [Conditioning] [Reports] [Links]

Overview

Replacing old S-band structures with newly designed structures in order to mitigate damages by discharges and to improve the gradient.

SuperKEKB injector linac employs 2-m long S-band accelerating structures (cavities). They were fabricated by using a technology called electroforming. Among them 150 structures out of 230 structures are 40 years old and have been damaged under severe operational environment. It is planned to replace some of the structures and improve the accelerating gradient to reach the collision energy up to Upsilon 6S. Please send your comments and questions to K.Furukawa.

Resonance energies

Upsilon (Υ) states

4S : 10.5794 GeV, e+ : 4.000 GeV, e- : 7.007 GeV
5S : 10.875 GeV, e+ : 4.112 GeV, e- : 7.203 GeV
6S : 11.019 GeV, e+ : 4.166 GeV, e- : 7.298 GeV
(by t.kamitani, nov.2021 updated)

Collision energy change scenario at SuperKEKB (by y.ohnishi)

Another interesting state

10.751 GeV
10.751 GeV: e+ : 4.065 GeV, e- : 7.121 GeV
10.751 + 0.059 : 10.810 GeV: e+ : 4.087 GeV, e- : 7.160 GeV

Other parameters

Nominal energy gain per accelerating structure (2 m long)

40 MeV (20 MeV / m)

Nominal energy gain per accelerator unit (10 m long)

160 MeV

Link to

Database of accelerating structures

Beam transport line positron energy limit, QC1LP 90%, Main ring bend power supply 98%

4.290 GeV (coil heating limit, by m.kikuchi, n.tokuda, n.ohuchi)

Beam transport line electron energy limit

8.465 GeV (coil heating limit, by m.kikuchi)

Maximum (symmetric) collision energy

11.35 GeV, e+ : 4.29 GeV, e- : 7.51 GeV

Real maximum (assymmetric) collision energy

12 GeV, e+ : 4.29 GeV, e- : 8.41 GeV

Schedule

2016 - 2018.

Design and test of new accelerating structure

Summer 2020.

Conditioning of first fabrication batch

Winter 2021.

Installation of first batch at Unit #44 in Main Linac

2021c.

Beyond Y(4S) collision, energy scan at 10.66, 10.71, 10.75, 10.81 GeV, internal plan by belle2, acceleration energy confirmation by ego

2021 - 2022.

Conditioning of remaining batches of structures

Summer 2022.

Installation of an additional klystron at Unit #44 in Main Linac

Winter 2023.

Installation of structures

Winter/Spring 2023.

Beam acceleration tests (Decided in July 2022 to postpone Y(6S) to ensure more data at Y(4S))

With additional budget.

Replacement of damaged dummy loads in Main Linac, and more structures and modulators for a higher energy

Conditioning

Typical conditioning during sumer 2020.

Reports on higher-energy acceleration at the injector linac

• Observation of e+e- → ωχbJ(1P) and search for Xb → ωΥ(1S) at √s near 10.75 GeV [pdf]
  The Belle II Collaboration, [ arXiv ], Aug.28.2022.

• Belle II Results and Plans [pdf]
  B. Fulsom, [ Exotic heavy meson spectroscopy ], Aug.15.2022.

• Quarkonium at Belle II [pdf]
  K. Lautenbach, [ DIS2022 ], May.4.2022.

• Bottomonium WG Overview [pdf]
  B.Fulsom, [ 41st B2GM ], Jan.27.2022.

• 2021c Operation including 10.75 GeV Energy Scan from Nov.10 to Nov.29.
  Y.Onishi et al.

• Upgrade plan of power supplies for bending magnets of beam transport line [pdf]
  M.Kikuchi, [ 18th Beam Injection Task Force Meeting ], Nov.19.2021.

• Accelerator structure development towards high-gradient stable acceleration [pdf]
  H.Ego, [ 9th SKB long term plan ], Oct.1.2021.

• [ Above Y(4S) Task Force / SuperKEKB Meeting ], Jul.13.2021.

• Bottomonium and Beyond Y(4S) report [pdf]
  B.Fulsom, [ 39th B2GM ], Jun.24.2021.

• Injector linac status and energy margin [pdf]
  K.Furukawa, [ 37th B2GM ], Nov.9.2020.
  Beyond 4S [pdf]
  B.Fulsom, [ 37th B2GM ], Nov.9.2020.

• Above Upsilon(4S) Task Force Update
  B.Fulsom, [ B2EB ], Jun.16.2020.  

• Approach to the more stable injector linac for SuperKEKB [pdf]
  H.Ego, [ Beyond 4s meeting ], Jun.12.2020.

• Above Upsilon(4S) Discussion Slides [pdf]
  B. Fulsom, R. Mizuk, [ Bottomonium and Hyperons WG Meeting #49 ], May.29.2020.

• Approach to the more stable injector linac for SuperKEKB [pdf]
  H.Ego, [ 33rd B2GM ], Jun.17.2019.

• Inspection of inner surface of S-band accelerating structures of KEK electron-positron injector linac used for more than 30 years [pdf] [poster-pdf]
  T.Higo, H.Ego, Y.Enomoto, S.Ushimoto, Proc. of PASJ 2018, Nagaoka, Japan, August 2018, pp.445-449.

• Manufacture of S-band accelerating structure [pdf]
  A.Saji, K.Ihara, A.Machida, T.Suzuki, K.Endo, T.Higo, H.Ego, Y.Enomoto, T.Takatomi, Proc. of PASJ 2018, Nagaoka, Japan, August 2018, pp.918-921.

• Accelerating structure [pdf]
  H.Ego, [ 22nd KEKB Accelerator Review Committee ], Mar.14.2018.

• Accelerating structure [pdf]
  T.Higo, [ 3rd SuperKEKB Domestic Review ], Sep.8.2017.

• Injector Linac Energy Margin [pdf]
  K.Furukawa, [ 26th B2GM ], Feb.10.2017.

• Surface Inspection and High Gradient Performance of S-Band Accelerator Tubes used for 20-30 Years at KEK [pdf]
  T.Higo, Y.Yano, N.Toge, K.Suzuki, S.Ushimoto, Proc. of PASJ 2016, Chiba, Japan, August 2016, pp.853-857.

• Upgrade Scenario to Ecm = 12 GeV [pdf]
  M.Kikuchi, Private communication, Dec.1.2011.
  

• Accelerator design at SuperKEKB [pdf]
  Y.Onishi et al., PTEP, 2013, 03A011, 2013. (section 2.2 beam energy)

Links

Collision energy change scenario at SuperKEKB Database of accelerating structures (acrf) Information of acceleration gain (epics pv) Linac-related B2GM reports Linac conference papers Linac reports Linac projects Belle II indico

New accelerating structures at #44 unit.

[Overview] [Resonaces] [Parameters] [Schedule] [Conditioning] [Reports] [Links]