Speaker
Description
The Electron-Ion Collider (EIC) is a high-current, high luminosity (10^34 cm^2 s^(-1)) machine designed to reveal the internal spin structure of the proton by colliding beams of electrons and heavy ions such as lead and uranium. Frequent small angle Coulomb scattering, known as intra-beam scattering of the ion beam causes emittance growth, degrading luminosity. Coherent electron cooling is considered as a future EIC upgrade to counteract ion beam emittance growth, reducing vertical emittance from 2.5 μm to 0.3 μm in 2 hours. In this system, a cool, dense electron beam co-propagates with a “hot” ion beam enabling energy transfer from ions to electrons.
This electron beam would be accelerated through SRF 591 MHz cavities, before it is decelerated and its energy recovered by the cavities. Each electron bunch is 4-5cm long, occupying a significant fraction of the RF wavelength and so it experiences a non-linear accelerating voltage introducing curvature of the bunch longitudinal phase space. A third harmonic cavity is proposed to compensate for this non-linearity.
This work presents the use of machine learning for the RF optimisation of a third harmonic cavity with respect to maximum electric and magnetic surface fields imposed on superconducting cavities. Damping of high impedance dipole modes is critical for ERLs, as insufficiently damped modes may trigger regenerative beam-breakup instabilities, lowering the breakup threshold current and consequently compromising energy recovery. We investigate very large aperture radii (≥30 mm) geometries to ensure dipole HOMs lie above cut-off. We find that for all candidate geometries the first dipole passband remains trapped, requiring investigation and subsequent optimisation of both end-cell geometry and an enlarged bottleneck cavity-beampipe transition to improve dipole propagation. Remaining high impedance dipoles are damped by use of waveguides, of which several configurations are investigated.
| Presenting Author | Sara Toole |
|---|---|
| Is the Presenting Author a PhD Student or Early Career Scientist ? | Yes |
| Area of research | RF systems |