RF LINAC for Gamma-ray compton sources

RF LINAC FOR GAMMA-RAY COMPTON SOURCESC. Vaccarezza on behalf of european collaboration

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OUTLINE

Gamma Ray Compton Sources New generation source

requirements ELI-NP: the European proposal

a S-C-band solution : the reference WP the C-band structures the layout the lattice error sensitivity

HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013

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Gamma-Ray Compton sourcesThanks to the extremely advanced characteristics:energy,tunability, mono-chromaticity, collimation, brilliance, time rapidity, polarizability etc.the new generation of Compton Sources will play a critical role for advanced applications in:

Nuclear resonance fluorescence Nuclear photonics: (γ-p) (γ-n) reactions Medical applications: new medical isotopes

production Material studies Radioactive waste management and isotope

identification High brilliance Neutron sourcesHBEB 2013, San Juan Mar, Puerto Rico |March 25-

28, 2013

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New generation γ-source:High Phase Space density electron beams vs Lasers

Bright

Mono-chromatic

High Spectral Flux

Tunable

Highly Polarized

Photon energy 1-20 MeV

Spectral density > 104 ph/sec.eV

Bandwith (rms) <0.3%

# photons/sec within FWHM bdw.

0.5÷1.5 109

Linear Polarization >95 %


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The electron-photon collider approach:


The rate of emitted photons is given by:

where:

leading to:

𝑁𝛾=𝐿𝜎𝑇

𝐿=𝑁 𝐿𝑁 𝑒 /2𝜋 (𝜎𝑥❑2 +𝑤0❑

2 /4 )

Laser

e-

𝑁𝛾 [ 𝑠𝑒𝑐− 1 ]=4.1 ×108 𝑈𝐿 [ 𝐽 ]𝑄 [𝑝𝐶 ] 𝑓 𝑅𝐹𝑛𝑅𝐹

h𝜈𝐿 [𝑒𝑉 ](𝜎 𝑥❑2 [𝜇𝑚 ]+ 1

4𝑤0❑

2 [𝜇𝑚 ] )√1+(𝑐 𝜎𝑡 𝛿4𝜎𝑥

)2

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Within the desired bandwith:


Δ𝜈𝛾

𝜈𝛾

≅ √(𝛾𝜗 )4+4 ( ∆𝛾𝛾 )

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+( 𝜀𝑛𝜎𝑥)

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+( ∆𝜈𝐿

𝜈𝐿)

2

+(𝑀2 𝜆𝐿

2𝜋𝑤0)

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+( 𝑎0𝑝2/3

1+𝑎0𝑝2/2 )

2collimation

systeme- beam Laser system

A simple model by L. Serafini, V. Petrillo predicts :

/

5.1 2

withinsecphscattered

NN bw

L. Serafini

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Spectral density SPD: a key parameter


2

02

22222

022

20

2

414

2

3

4

02

24

24 2)(

8 1067.1

w

cwx

a

w

M

x

n

RFRFL

x

tz

pL

L

L

nfQUSPD

fRF = repetition rate

nRF = bunches per RF pulse

UL = Laser pulse energy (J)

Q = el. bunch charge (pC)

h = laser photon energy=2.4 eV

f = collision angle

x = e- beam focal rms spot size in mm w0 = laser focal spot size in mm

For the considered bandwith


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Analytical model vs. classical/quantum simulation

V. Petrillo

CAIN (quantum MonteCarlo)Run by I.Chaichovskaand A. Variola

TSST (classical)Developed byP. Tomassini

Comp_Cross (quantum semianalytical)Developed by V.Petrillo

Number ofphotons

bandwidth

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ELI-NP: a new generation γ-ray source


Photon energy 1-20 MeVSpectral Density > 104 ph/sec.eVBandwidth (rms) 0.3%# photons per shot within FWHM bdw.

1.0-4.0.105

# photons/sec within FWHM bdw. 2.0-8.0.108

Source rms size 10 - 30 µmSource rms divergence 25-250 µradPeak Brilliance (Nph/sec.mm2mrad2.0.1%)

1022 - 1024

Radiation pulse length (rms, psec) 0.7-1.5Linear Polarization > 99 %Macro rep. rate 100 Hz# of pulses per macropulse 31Pulse-to-pulse separation 16 nsec

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ELI-NP: the F-I-UK European proposal


European Collaboration for the proposal of the gamma-ray source:

Italy: INFN,SapienzaFrance: IN2P3, Univ. Paris SudUK: ASTeC/STFC

~ 80 collaborators elaborating the CDR/TDR

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ELI-NP requirements:


State of the art Compact

S-band Photoinje

ctor+

C-band linac

+ =

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A r.t. RF linac vs pulsed laser source


Electron beam parameter at IPEnergy (MeV) 180-750

Bunch charge (pC) 25-400Bunch length (µm) 100-400εn_x,y (mm-mrad) 0.2-0.6Bunch Energy spread (%) 0.04-0.1Focal spot size (µm) 15-30# bunches in the train 31Bunch separation (nsec) 16energy variation along the train

0.1 %

Energy jitter shot-to-shot 0.1 %Emittance dilution due to beam breakup

< 10%

Time arrival jitter (psec) < 0.5Pointing jitter (m) 1

Yb:Yag Collision Laser

Low Energy Interact

ion

High Energy

Interaction

Pulse energy (J) 0.2 0.5

Wavelength (eV) 2.4 2.4

FWHM pulse length (ps)

2-4 2-4

Repetition Rate (Hz)

100 100

M2 1.2 1.2

Focal spot size w0 (µm)

> 25 > 25

Bandwidth (rms) 0.05 % 0.05 %

Pointing Stability (µrad)

1 1

Sinchronization to an ext. clock

< 1 psec < 1 psec

Pulse energy stability

1 % 1 %

Advantages: Moderate risk (state of art RF gun,

reduced multibunch operation problems respect to higher frequencies, low compression factor<3)

Economic Compact (the use of the C-band

booster meets the requirements on the available space)

Possibility to use SPARC as test stand

Operation criteria: Long bunch at cathode for high

phase space density :Q/n

2 >103 pC/(µrad)2

Short exit bunch (280 µm) for low energy spread (~0.05%)

The hybrid scheme for the Linac:

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WPref from the photoinjector (Tstep tracking)


Egun=120 MV/mE(S1)=E(S2)=21 MV/mQ=250 pC

C. Ronsivalle


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C-band structuresD. Alesini


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Central cells


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Mitigation of multibunch effect with damped structure

D. Alesini

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The machine layout

ELI-NP infrastructure

N. Bliss

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Linac & Transfer lines

Low energy High Energy

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SB-Transverse beam size and distribution (Elegant tracking)


Low energy High energy


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WPref_SB-energy spread & current

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Wake on Δx=500 µm

Wake res Q 11000 Wake res Q 100

M. Migliorati

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Wake on Δx=500 µm

SB Wake res Q 100

Lattice error sensitivity:

Error value RFCW

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QUAD28

DIP4

x 80 µm X X Xy 80 µm X X XV 300 kV X - -

1° X - -k 5x10-4

fs- X -

1x10-3 fs

- X

The Latin Hypercube:

138 Variables (12*4+28*3+4*3) -1.0 Δu/u 1.0

100 machine runnings

• The applied Δx,y affects all the elements at the same time like a real machine

• Δx and Δy are applied together

• For each sample machine an Elegant input lattice is written with the corresponding errors

• The sample machine is runned• The all results are read and plotted

Ex. 10 machines Δu/u distribution:

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ΔV= ± 300 kV ΔΦ= 1°


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Δx= ± 80 m


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Δk/kmax= ± 5.0E-4 ΔB/Bmax= ± 1.0E-3


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All the contributions applied


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Conclusions


A C-band RF linac has been presented based on the requirements of the new generation gamma-ray source in the framework of the ELI-NP project: The key parameters have been described

together with the main aspects of the proposed solution

A lattice sensitivity study has been presented that even if not exhaustive anyway shows acceptable probability margin for the linac routine operation.

RF LINAC for Gamma-ray compton sources

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