Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

R Pompili ,W Li,A Mostacci ,M Petrarca ,C Vaccarezza ,S Lupi ,Giampiero Di Pirro ,D Di Giovenale ,M Croia ,F Giorgianni ,S Romeo ,A Cianchi ,A Gallo ,M Ferrario ,M P Anania ,G Gatti ,E Chiadroni ,Anna Giribono ,J Scifo ,L Piersanti ,M Bellaveglia ,A Biagioni ,V Shpakov ,F Filippi ,Giovanni Castorina ,F Villa

doi:10.1088/1367-2630/18/8/083033

Abstract

The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

Highlights

Introduction and motivationThe generation of ultra-short electron bunches is strongly driven by a wide range of applications spanning from high intensity radiation sources to novel acceleration concepts
The underlying principle of simultaneous bunch and jitter compression relies on space-charge effects that, especially for ultra-short beams, strongly affect the longitudinal phase space (LPS), but are mostly ineffective on the bunch centroid dynamics
The underlying principle for the simultaneous bunch compression and relative arrival timing-jitter (ATJ) reduction relies on the differences in dynamics between particles in the same bunch and bunches in different shots

Summary

Introduction

Introduction and motivationThe generation of ultra-short electron bunches is strongly driven by a wide range of applications spanning from high intensity radiation sources (e.g. free electron lasers [1] and THz [2]) to novel acceleration concepts (e.g. based on plasma wakefields [3]). The underlying principle of simultaneous bunch and jitter (with respect to the PC laser) compression relies on space-charge effects that, especially for ultra-short beams, strongly affect the longitudinal phase space (LPS), but are mostly ineffective on the bunch centroid dynamics (mean energy and time of arrival). It means that PC laser arrival time and RF accelerating field jitters have a different impact on the time-energy distribution of particles within the bunch (where space-charge must be considered) and on bunch centroids in consecutive shots (not affected by space-charge) By using this hybrid compression scheme we obtained a less than 90 fs (rms) bunch duration and an ATJ relative to the PC laser below 20 fs (rms) downstream the dogleg. Previous works on this topic, obtained in several facilities, reported relative timing-jitters in the range of 50–100 fs [9,10,11]

Objectives

Results

Conclusion