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

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,

Gamma-Ray Compton sources Thanks 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 sources HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

New generation γ -source: High Phase Space density electron beams vs Lasers  Bright  Mono-chromatic  High Spectral Flux  Tunable  Highly Polarized Photon energy1-20 MeV Spectral density> 10 4 ph/sec.eV Bandwith (rms)<0.3% # photons/sec within FWHM bdw. 0.5 ÷ Linear Polarization>95 % HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

The electron-photon collider approach: HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 The rate of emitted photons is given by: where: leading to: Laser e-e- 5

Within the desired bandwith: HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 collimation system e - beam Laser system A simple model by L. Serafini, V. Petrillo predicts : 6 L. Serafini

Spectral density SPD: a key parameter HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 f RF = repetition rate n RF = bunches per RF pulse U L = 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 w 0 = laser focal spot size in mm 7

Analytical model vs. classical/quantum simulation V. Petrillo CAIN (quantum MonteCarlo) Run by I.Chaichovska and A. Variola TSST (classical) Developed by P. Tomassini Comp_Cross (quantum semianalytical) Developed by V.Petrillo Number of photons bandwidth HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

ELI-NP: a new generation γ-ray source HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 Photon energy1-20 MeV Spectral Density> 10 4 ph/sec.eV Bandwidth (rms)  0.3% # photons per shot within FWHM bdw # photons/sec within FWHM bdw Source rms size µm Source rms divergence µrad Peak Brilliance (N ph /sec. mm 2 mrad %) Radiation pulse length (rms, psec) Linear Polarization> 99 % Macro rep. rate100 Hz # of pulses per macropulse  31 Pulse-to-pulse separation 16 nsec 9

ELI-NP: the F-I-UK European proposal HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 European Collaboration for the proposal of the gamma- ray source: Italy: INFN,Sapienza France: IN2P3, Univ. Paris Sud UK: ASTeC/STFC ~ 80 collaborators elaborating the CDR/TDR 10

ELI-NP requirements: HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, State of the art Compact S-band Photoinjector + C-band linac + =

A r.t. RF linac vs pulsed laser source HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 Electron beam parameter at IP Energy (MeV) Bunch charge (pC) Bunch length (µm) ε n _ x,y (mm-mrad) Bunch Energy spread (%) Focal spot size (µm)15-30 # bunches in the train  31 Bunch separation (nsec) 16 energy variation along the train0.1 % Energy jitter shot-to-shot0.1 % Emittance dilution due to beam breakup < 10% Time arrival jitter (psec)< 0.5 Pointing jitter (  m) 1 Yb:Yag Collision Laser Low Energy Interaction High Energy Interaction Pulse energy (J) Wavelength (eV)2.4 FWHM pulse length (ps)2-4 Repetition Rate (Hz)100 M2M2  1.2 Focal spot size w 0 (µm)> 25 Bandwidth (rms)0.05 % Pointing Stability (µrad)11 Sinchronization to an ext. clock < 1 psec Pulse energy stability1 % 12

 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 >10 3 pC/(µrad) 2  Short exit bunch (280 µm) for low energy spread (~0.05%) The hybrid scheme for the Linac:

WP ref from the photoinjector (Tstep tracking) HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, Egun=120 MV/m E(S1)=E(S2)=21 MV/m Q=250 pC C. Ronsivalle

C-band structures HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, D. Alesini

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

Mitigation of multibunch effect with damped structure HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, D. Alesini

HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, The machine layout ELI-NP infrastructure N. Bliss

Linac & Transfer lines 19 HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 Low energyHigh Energy

SB-Transverse beam size and distribution (Elegant tracking) 20 HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 Low energyHigh energy

WPref_SB-energy spread & current HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

Wake on Δ x=500 µ m 22 HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 Wake res Q Wake res Q 100 M. Migliorati

Wake on Δ x=500 µ m 23 HBEB 2013, San Juan Mar, Puerto Rico |March 25-28, 2013 SBWake res Q 100

Lattice error sensitivity: ErrorvalueRFCW 12 QUAD 28 DIP 4 80 µmXXX XXX 300 kVX-- 1°X-- 5x10 -4 fs-X- 1x10 -3 fs-X

The Latin Hypercube:  138 Variables (12*4+28*3+4*3)  -1.0  Δ u/u  1.0  100 machine runnings The applied Δ x,y affects all the elements at the same time like a real machine Δ x and Δ y 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 Δ u/u distribution:

Δ V= ± 300 kV Δ Φ = 1° HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

Δ x= ± 80  m HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

Δ k/k max = ± 5.0E-4 Δ B/B max = ± 1.0E-3 HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

All the contributions applied HBEB 2013, San Juan Mar, Puerto Rico |March 25-28,

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