Author: Nakayama, H.
Paper Title Page
TUOBC02 Small-Beta Collimation at SuperKEKB to Stop Beam-Gas Scattered Particles and to Avoid Transverse Mode Coupling Instability 1104
 
  • H. Nakayama, Y. Funakoshi, K. Kanazawa, K. Ohmi, Y. Ohnishi, Y. Suetsugu
    KEK, Ibaraki, Japan
  • H. Nakano
    Tohoku University, Graduate School of Science, Sendai, Japan
 
  At SuperKEKB, beam particles which are Coulomb-scattered by the residual gas molecular change direction and will be eventually lost by hitting beam pipe inner wall. Due to large vertical beta function and small beam pipe radius just before IP, most of Coulomb-scattered particles are lost there and are very dangerous for the Belle-II detector. To stop such particles before the IP, vertical collimators are installed in the ring. However, such vertical collimators should be placed very close (few mm) to the beam and therefore induce transverse mode coupling instability. To avoid beam instability and achieve collimation at the same time, we need to install vertical collimators where vertical beta function is SMALL, since maximum collimator width determined by aperture condition is proportional to β1/2, and minimum collimator width determined by instability is proportional to β2/3. We present our strategy to stop beam-gas scattered particles and simulated loss rate in the interaction region. We will also show dedicated vertical collimator design to achieve less instability.  
slides icon Slides TUOBC02 [2.196 MB]  
 
TUPPR007 Beam Background and MDI Design for SuperKEKB/Belle-II 1825
 
  • H. Nakayama, M. Iwasaki, K. Kanazawa, Y. Ohnishi, S. Tanaka, T. Tsuboyama
    KEK, Ibaraki, Japan
  • H. Nakano
    Tohoku University, Graduate School of Science, Sendai, Japan
 
  The Belle experiment, operated at the asymmetric electron-positron collider KEKB, had accumulated a data sample with an integrated luminosity of more than 1 ab−1 before the shutdown in June 2010. We have started upgrading both the accelerator and the detector, SuperKEKB and Belle-II, to achieve the target luminosity of 8×1035 cm−2 s−1. With the increased luminosity, the beam background will be severe. The development of Machine- Detector Interface (MDI) design is crucial to cope with the increased background and protect Belle-II detector. We will present the estimation of impact from each beam background sources at SuperKEKB, such as Touschek-scattering, Beam-gas scattering, radiative Bhabha process, etc.. We will also present our countermeasures against them, such as collimators to stop scattered beam particles, Tungsten shield to protect inner detectors from shower particles, and dedicated beam pipe design around interaction point to stop synchrotron radiation, etc.