Comb beam for particle-driven plasma-based accelerators

Comb beam for particle-driven

plasma-based accelerators

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

particle-driven plasma-based accelerators.

A.

Mostacci,

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.

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

µ

m long, 20

µ

m spot size, in a plasma

of density 10

e

/m

at

λ

p

=300

µ

m

•

Ramped bunch train configuration to enhance transformer ratio

•

High quality bunch preservation during acceleration and transport

A.R. Rossi,

Plasma accelerators: external injection, Wednesday 25-09.

F. Massimo,

Transformer ratio studies for PWFA, Tuesday 24-09.

Inj. phase

Bunch spacing

Train length

Accelerating field phase

Energy separation

TW focusing field (~300G)

Emittance

Bunches current, length and

their max compression phase

Gun focusing field (~3kG)

Emittance

Bunches current, length

Gun exit energy

Beam brightness

Compression phase

stability

Bunch separation

stability

Gun inj. phase and

space charge

Bunches distance at

the linac entrance

Compression

φ

<90 deg

Over-compression

180 deg<

φ

<90 deg

Deep over-compression

φ

>180 deg

Compression

φ

<90 deg

Over-compression

180 deg<

φ

<90 deg

Deep over-compression

φ

>180 deg

TSTEP simulation by C. Ronsivalle

TSTEP

MEASUREMENT

Compression

φ

<90 deg

Over-compression

180 deg<

φ

<90 deg

Deep over-compression

φ

>180 deg

TSTEP simulation by C. Ronsivalle

MEASUREMENT

Compression

φ

<90 deg

Over-compression

180 deg<

φ

<90 deg

Deep over-compression

φ

>180 deg

TSTEP simulation by C. Ronsivalle

Gun energy

5.7MeV

Charge

40pC/80pC/50pC/30pC

Bunch length on crest

2126.3 (8.7) fs

Min. bunch length

168.2 (8.7) fs

Gun ext. phase

35 deg

Energy 168-109 MeV

Energy Spread <0.8%

Compression

Over compression

Deep

over compression

Compression

Over compression

Deep

over compression

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

amplitude and separation

RF comp. phase

-89.5 deg

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

amplitude and separation

RF comp. phase

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

RF comp. phase

-93.5 deg

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

RF comp. phase

-96.5 deg

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

Compression

Over compression

Deep

over compression

4p 3p 2p 1p

C. Ronsivalle, TSTEP simulations.

The injection phase in the compressor (RF compressor phase) can select the number

of bunches and their relative current.

RF comp. phase -105.5 deg

Modulation in the bunch

Selection of the

number of pulses

Tuning of the relative

M. Bellaveglia,

fs synchronization systems for advanced accelerator applications, Thursday 26-09.

E. Chiadroni,

Linac-based THz radiation sources,

Tuesday 24-09.

R. Pompili,

Single-shot longitudinal not intercepting diagnostic (EOS), Wednesday 25-09.

F. Villa,

Two Colors FEL experiment at SPARC_LAB,

Tuesday 24-09.

L. Innocenti, A. Cianchi, Measurement of TWISS parameters for COMB beams

.

THz radiation source

Beam diagnostics

Two color FEL radiation

Low level RF system

Measurements,

4 pulses, 200pC

E. Chiadroni et al., Rev. Sci.

Instrum. 84, 022703 (2013)

V. Petrillo et al., Phys. Rev. Lett.

111, 114802 (2013).

Measurements,

2 pulses, 160pC

FEL Single

Spike

THz

Radiation

LWFA_ext

LASER

COMB

Velocity Bunching

PWFA

Thomson

C_Band

driver

DWFA

THz Radiation

FEL

See A. Cianchi,

Advanced beam dynamics

experimental studies and

applications at SPARC_LAB,

Wednesday 25-09.

See D. Alesini,

High-gradient C-band

accelerating structures,

Wednesday 25-09.

Thank

you