Preliminary Simulation on Electron Cloud Build-up in SppC

Liu Yu Dong

ContentThe Photon simulations

Reflectivity (R) and Photo-Electron Yield (PY)

First simulations of electron cloud build-up in FCC-hh

Preliminary Simulation on Bulid-up of Electron Cloud

in SppC

Electron cloud in Drift region

Electron cloud in Dipole and quadrupole magnetic field

The Photon simulations

Number of SR photons per proton per meter:

Critical energy of the SR spectrum:

For SPPC, a proton can produce photons 2236, Ecrit=3.89keV

Photon Reflectivity (R)

R can be calculated and measured as a function of Material,

Angle of incidence ,Q Photon energy, and Surface Roughness

(best in the low regime).

PY can only be measured and (being proportional to photo-absorption)

depends on the same parameters as R, plus the photoelectric cross-section

(that can be calculated) and the Surface condition (it is more surface

dependent).

Photo-electron Yield (PY)

R. CiminoFCC-hh Design Meeting 12-3-2015

The photoelectron yield and the photon reflectivity depend both on material and SR properties, so needs to be determined separately for each case• For 40eV SR (LHC), several experimental studies have been made

at/with CERN(V. Baglin et al, CERN-LHC-PROJECT-REPORT-206; V. V. Anashin et al, Nucl.

Instrum.Meth. A 448 (2000) 76.)• For 4keV SR (FCC), an experimental study was made at KEK• (Y. Suetsugu et al, Journal of Vacuum Science & Technology A 21, 186 (2003).)

First simulations of electron cloud build-up in FCC-hh (simulated by L. Mether, G. Iadarola, G. Rumolo with code PyECLOUD)

Simulations of build-up in typical arc elements:

Dipole, Quadrupole, Field-free region

Bunch patterns: 50b + 12e for 25ns spacing

x-distribution of electrons in chamber

Preliminary Simulation on bulid-up of electron in SppC

( By Code ECIC developed by Liu Yu Dong for BEPCII)

 Parameters Value

Bunch particles nb(1011) 2.0

Bunch spacing (ns) 25

Pipe radius (mm) 20

Circumference(km) 54.7

Tune 60.3

rms bunch length(75mm) 75.5

Bunch size (rm) 1/1

Dipole magnetic field (T) 20

Quadrupole(T/m2) 1000

Simulation parameters

Electron Cloud in Drift Region

Electron Cloud in Dipole Magnetic Field

Electron Cloud in Quadrupole Magnetic Field

Conclusion and next plan for Electron Cloud

The photon reflectivity and photo-electron yield are

important characters for the distribution and density of

electron cloud;

The simulation results should be benchmarked with different

code;

The coating for vacuum pipe to reduce the SEY in magnetic

region is not necessary;

The dynamics of electrons in strong magnetic field need

more accurate physical model.

Thank you for attention!