Modeling and experimental study to identify arrival-time jitter sources in the presence of a magnetic chicane

P Craievich,S Di Mitri,G Penco,M Milloch,F Rossi

doi:10.1103/physrevstab.16.090401

P Craievich, S Di Mitri + Show 3 more

Open Access

https://doi.org/10.1103/physrevstab.16.090401

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Abstract

The accurate and stable synchronization between electron bunch and external laser is a key requirement for the successful operation of an externally seeded free electron laser. This requirement is particularly stringent when the electron bunch is longitudinally compressed to sub-ps durations. We present an analytical description of the electron bunch arrival-time jitter that, supported by experimental evidence, allows the identification of specific, dominant jitter sources. The arrival-time jitter measurements were carried out as a function of the bunch length compression factor in FERMI@Elettra linac. The experimental behavior of the pulse-to-pulse time jitter agrees well both with the analytical predictions and particle tracking simulations. Our modeling takes into account the photoinjector laser arrival time on the cathode, the jitter of phases and voltages of the radio-frequency accelerator, and fluctuations of the compressor's dipole field.

Highlights

The FERMI@Elettra free electron laser (FEL) is a single-pass, S-band linac-based externally seeded FEL implementing high gain harmonic generation in the 80-4 nm fundamental output wavelength range
The arrival-time jitter of an electron bunch after magnetic compression has been measured in the FERMI@Elettra main linac
The short-term stability tolerances for the FERMI linac have been achieved for each rf system and the final arrival-time jitter results in being smaller than 50 fs rms

Summary

INTRODUCTION

The FERMI@Elettra free electron laser (FEL) is a single-pass, S-band linac-based externally seeded FEL implementing high gain harmonic generation in the 80-4 nm fundamental output wavelength range. The main dispersive sections in the FERMI linac are the two magnetic chicanes that are used to longitudinally compress the beam in combination with an off-crest setting of the upstream accelerating structures rf phases. This configuration implies that electron bunch energy jitter at the entrance of the chicane develops into time jitter by. V is dedicated to the measurements of the electrons ATJ versus the compression factor performed in the FERMI linac

LAYOUT

ANALYTICAL MODEL FOR THE ARRIVAL-TIME JITTER

TRACKING CODE RESULTS

EXPERIMENTAL RESULTS

CONCLUSION AND DISCUSSION