Ricerc@Sapienza

In high-brightness LINear ACcelerators (LINACs), electron bunch length can be measured indirectly by a radio frequency deflector (RFD). In this paper, the accuracy loss arising from non-negligible correlations between particle longitudinal positions and the transverse plane (in particular the vertical one) at RFD entrance is analytically assessed. Theoretical predictions are compared with simulation results, obtained by means of ELEctron Generation ANd Tracking (ELEGANT) code, in the case study of the gamma beam system (GBS) at the extreme light infrastructure—nuclear physics (ELI-NP).

The correlations between vertical and longitudinal planes at the Radio Frequency Deflector (RFD) entrance can be introduced by misalignments of accelerating sections or quadrupoles upstream of the RFD. These correlations are undesired effects and they can affect the RFD based bunch length measurements in high-brightness electron LINAC. In this paper, an RFD based measurement technique for vertical and longitudinal planes is proposed.

The effects of assumptions about bunch properties on the accuracy of the measurement method of the bunch length based on radio frequency deflectors (RFDs) in electron linear accelerators (LINACs) are investigated. In particular, when the electron bunch at the RFD has a non-negligible energy chirp (i.e. a correlation between the longitudinal positions and energies of the particle), the measurement is affected by a deterministic intrinsic error, which is directly related to the RFD phase offset.