Alec

Electron beams emit coherent synchrotron radiation (CSR) when the trajectory is bent by a dipole. This radiation often has an adverse effect, inducing energy spread and emittance growth. Currently, experiments are underway through a reversed-chicane beamline at AWA to understand and measure the effect of parallel-plate shielding gaps within the bending magnet’s vacuum chamber as a method to mitigate CSR.

Alec’s work is in support of this experimental effort. This work involves simulation of the AWA beamline in preparation for an upcoming measurement campaign and includes post-processing and analysis of the results.

The parallel-plate shielding gaps along the bending dipoles in this reversed-chicane are tunable. At the most recent experiment the shielding gap sizes tested were 3 cm, 2 cm, and 1 cm. Downstream of the chicane, a transverse deflecting cavity (TDC) and spectrometer are installed to project the longitudinal phase space of the beam onto a camera. The shielding gap sizes were then repeated with an additional installed 2-mm slit, which blocks charge in a way such that CSR is minimized, but the other dynamics of the beam are not changed.

To provide a point of comparison with the measurements, a simulation was set up modeled after the real-life reversed-chicane using a one-dimensional tracking code, BEam Longitudinal Tracking (BELT). A single longitudinal phase space camera shot was chosen to become the input. The figure below shows the beam image chosen for this simulation, and the correlation and current profile derived from the single shot from left to right.

The figure below displays the results of this simulation work. The red curves are the no-slit cases, while the blue curves are cases with the slit. The left and right columns are experimental and simulated results, respectively. The rows are the 3 cm, 2 cm, and 1 cm cases from top to bottom. This analysis provides insight into the dependency of shielding gap size on its interactions with the CSR fields and helps to form plans to improve the method for upcoming planned campaigns.