Comb beam for particle-driven plasma-based accelerators

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1 A. Mostacci, on behalf of the SPARC team Comb beams are sub-picosecond, high-brightness electron bunch trains generated via the velocity bunching technique. Such bunch trains can be used to drive tunable and narrow band THz sources, FELs and plasma wake field accelerators. In this paper we present recent results at SPARC_LAB on the generation of comb beams for particledriven. Trieste Settembre 2013

Such bunch trains can be used to drive tunable and narrow band THz sources, FELs and plasma wake

2 Novel schemes for plasma based accelerators relies on high brightness beams (high current, low emittance). Recent and forthcoming technological upgrades have made SPARC a unique test bench for R&D on high brightness electron beam and their applications, other than SASE FEL activity already assessed. Resonant plasma Oscillations by Multiple electron Bunches. Generation of sub-ps, high brightness electron bunch trains (COMB beam). Successful generation of COMB beams (measurements). Numerical simulations for better understanding of the properties of COMB beams and investigating their application to particle-driven plasma based accelerators.

SASE FEL activity already assessed. Resonant plasma Oscillations by Multiple electron Bunches.

3 Coherent (resonant) plasma Oscillations by Multiple electron Bunches Weak blowout regime with resonant amplification of plasma wave by a train of high Brightness electron bunches produced by Laser Comb technique ==> 5 GV/m with a train of 3 bunches, 100 pc/bunch, 50 µm long, 20 µm spot size, in a plasma of density 1022 e-/m3 at λp=300 µm Ramped bunch train configuration to enhance transformer ratio High quality bunch preservation during acceleration and transport See also F. Massimo, Transformer ratio studies for PWFA, Tuesday A.R. Rossi, Plasma accelerators: external injection, Wednesday

plasma of density 1022 e-/m3 at λp=300 µm Ramped bunch train configuration to enhance transformer ratio High quality bunch preservation during

4 M. Boscolo, M. Ferrario et al., NIM A 577, (2007)

5 Gun focusing field (~3kG) Emittance Bunches current, length Accelerating field phase Energy separation Inj. phase Bunch spacing Train length Gun inj. phase and space charge Bunches distance at the linac entrance TW focusing field (~300G) Emittance Bunches current, length and their max compression phase Gun exit energy Beam brightness Compression phase stability Bunch separation stability

phase and space charge Bunches distance at the linac entrance TW focusing field (~300G) Emittance

7 Over-compression 180 deg<φ<90 deg Deep over-compression φ>180 deg Compression φ<90 deg TSTEP simulation by C. Ronsivalle

8 MEASUREMENT Over-compression 180 deg<φ<90 TSTEP deg Deep over-compression φ>180 deg Compression φ<90 deg TSTEP simulation by C. Ronsivalle

9 Over-compression 180 deg<φ<90 deg Deep over-compression φ>180 deg Compression φ<90 deg MEASUREMENT TSTEP TSTEP simulation by C. Ronsivalle

10 MEASUREMENT Over-compression 180 deg<φ<90 TSTEP deg Deep over-compression φ>180 deg Compression φ<90 deg TSTEP simulation by C. Ronsivalle

11 Measurements with 200pC Gun energy 5.7MeV Charge 40pC/80pC/50pC/30pC Energy MeV Energy Spread <0.8% Bunch length on crest (8.7) fs Min. bunch length (8.7) fs Gun ext. phase 35 deg

12 C. Ronsivalle, TSTEP simulations.

13 C. Ronsivalle, TSTEP simulations.

14 Deep over compression Over compression Compression C. Ronsivalle, TSTEP simulations.

15 Deep over compression Over compression Compression C. Ronsivalle, TSTEP simulations.

16 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the Modulation in the bunch amplitude and separation number of pulses Deep Over compression Compression over compression 4p 3p 2p 1p C. Ronsivalle, TSTEP simulations.

Tuning of the relative Selection of the Modulation in the bunch amplitude and

17 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the Modulation in the bunch amplitude and separation number of pulses Deep RF comp. phase Over compression Compression over compression deg 4p 3p 2p 1p C. Ronsivalle, TSTEP simulations.

18 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the Modulation in the bunch amplitude RF and comp. separation phase number of pulses Deep deg Over compression Compression over compression 4p 3p 2p 1p C. Ronsivalle, TSTEP simulations.

Tuning of the relative Selection of the Modulation in the bunch amplitude RF and comp.

19 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the Modulation in the bunch amplitude and separation number of pulses Deep Over compression Compression over compression 4p 3p 2p 1p RF comp. phase deg C. Ronsivalle, TSTEP simulations.

20 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the amplitude and separation number of pulses Modulation in the bunch Deep Over compression Compression over compression 4p 3p 2p 1p RF comp. phase deg C. Ronsivalle, TSTEP simulations.

Tuning of the relative Selection of the amplitude and separation number of pulses

21 The injection phase in the compressor (RF compressor phase) can select the number of bunches and their relative current. Tuning of the relative Selection of the Modulation in the bunch amplitude and separation number of pulses Deep Over compression Compression over compression 4p 3p 2p 1p RF comp. phase deg C. Ronsivalle, TSTEP simulations.

22 THz radiation source E. Chiadroni, Linac-based THz radiation sources, Tuesday Measurements, 4 pulses, 200pC E. Chiadroni et al., Rev. Sci. Instrum. 84, (2013) Two color FEL radiation F. Villa, Two Colors FEL experiment at SPARC_LAB, Tuesday Beam diagnostics R. Pompili, Single-shot longitudinal not intercepting diagnostic (EOS), Wednesday L. Innocenti, A. Cianchi, Measurement of TWISS parameters for COMB beams. Low level RF system Measurements, 2 pulses, 160pC V. Petrillo et al., Phys. Rev. Lett. 111, (2013). M. Bellaveglia, fs synchronization systems for advanced accelerator applications, Thursday

23 Velocity Bunching C_Band driver THz Radiation LWFA_ext See D. Alesini, High-gradient C-band accelerating structures, Wednesday See A. Cianchi, Advanced beam dynamics experimental studies and applications at SPARC_LAB, Wednesday LASER COMB Thomson FEL Single Spike THz Radiation PWFA DWFA FEL

24 Thank you

Les Accélérateurs Laser Plasma

Les Accélérateurs Laser Plasma Victor Malka Laboratoire d Optique Appliquée ENSTA ParisTech Ecole Polytechnique CNRS PALAISEAU, France [email protected] Accelerators : One century of exploration of