title: Experimental demonstration of electron longitudinal-phase-space linearization by shaping the photoinjector laser pulse.
abstract: Control of the electron-beam longitudinal-phase-space distribution is of crucial importance in a number of accelerator applications, such as linac-driven free-electron lasers, colliders and energy recovery linacs. Some longitudinal-phase-space features produced by nonlinear electron beam self- fields, such as a quadratic energy chirp introduced by geometric longitudinal wakefields in radio-frequency (rf) accelerator structures, cannot be compensated by ordinary tuning of the linac rf phases nor corrected by a single high harmonic accelerating cavity. In this Letter we report an experimental demonstration of the removal of the quadratic energy chirp by properly shaping the electron beam current at the photoinjector. Specifically, a longitudinal ramp in the current distribution at the cathode linearizes the longitudinal wakefields in the downstream linac, resulting in a flat electron current and energy distribution. We present longitudinal-phase-space measurements in this novel configuration compared to those typically obtained without longitudinal current shaping at the FERMI linac.
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Penco
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Danailov
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Demidovich
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Allaria
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy and University of Nova Gorica, 5000 Nova Gorica, Slovenia.
authors.forename: G
authors.initials: G
authors.lastname: De Ninno
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Di Mitri
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy and SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: W M
authors.initials: WM
authors.lastname: Fawley
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy and Dipartimento di Fisica, Università degli Studi di Trieste, Piazzale Europa 1, 34127 Trieste, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Ferrari
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy and Enea, via Enrico Fermi 45, 00044 Frascati, Roma, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Giannessi
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Trovó
mesh_terms: D004583:Electrons; D007834:Lasers; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D010315:Particle Accelerators / Q000295:instrumentation*