A preliminary assessment of the electron cloud effect for the FNALmain injector upgrade

Abstract

We present results from a preliminary assessment, via computer simulations, of the electroncloud density for the FNAL main injector upgrade at injection energy. Assuming a peak value for secondary emission yield δmax = 1.3, we find a threshold value of the bunch population, N b,th 1.25 × 10 11 , beyond which the electron-cloud density ρe reaches a steady-state level that is ∼ 10 4 times larger than for N b < N b,th , essentially neutralizing the beam, and leading to a tune shift ∼ 0.05. Our investigation is limited to a field-free region and to a dipole magnet region, both of which yield similar results for both N b,th and the steady-state value of ρe. Possible dynamical effects from the electron cloud on the beam, such as emittance growth and instabilities, remain to be investigated separately.