Challenges and Opportunities of high intensity X/  photon beams for Nuclear Photonics and Muon Beams Luca Serafini – INFN-Milan, EuroGammaS scientific coordinator V. Petrillo, C. Curatolo – Univ. of Milan Physics/Technology Challenges of electron-(optical)photon colliders as X/  beam Sources using Compton back-scattering Need of high peak brightness/high average current electron beams (cmp. FEL’s drivers) fsec-class synchronized and  m-  rad-scale aligned to high peak/average power laser beams Main goal for Nuclear Physics and Nuclear Photonics: Spectral Densities > 10 4 N ph /(s. eV) (state of the art: Hi  S 300, bremsstrahlung sources 1) photon energy range 1-20 MeV, bandwidths class Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

Main goal for MeV-class  and TeV  - nucleon colliders: Peak Brilliance > N ph /(s. mm 2. mrad %) 10 9 <N ph <10 13 Source spot size  m-scale (low diffraction, few  rad) Tunability, Mono-chromaticity, Polarization (H,V,C) ELI-NP-GammaBeamSystem in construction by EuroGammaS as an example of new generation Compton Source Photon-Photon scattering (+ Breit-Wheeler: pair creation in vacuum) is becoming feasible with this new generation  -beams Interesting new option for low emittance pion and muon beams generation using X-FEL’s and LHC beams (demonstrator based on Compton Source and SPS beams) Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

Courtesy L. Palumbo If the Physics of Compton/Thomson back-scattering is well known…. the Challenge of making a Compton Source running as an electron-photon Collider with maximum Luminosity, to achieve the requested Spectral Density, Brilliance, narrow Bandwidth of the generated X  ray beam, is a completely different issue/business !

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Compton Inverse Scattering Physics is clear: recall some basics Courtesy V. Petrillo 3 regimes: a) Elastic, Thomson b) Quasi-Elastic, Compton with Thomson cross-section c) Inelastic, Compton, recoil dominated

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 FELs ( pure   ) Thomson X-rays Nuclear Photonics X/  [MeV] T e [MeV] 1 GeV1 TeV Polarized Positrons   Colliders

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 We need to build a very high luminosity collider, that needs to maximize the Spectral Luminosity, i.e. Luminosity per unit bandwidth negligible diffraction 0 crossing angle electrons laser Scattered flux Luminosity as in HEP collisions –Many photons, electrons –Focus tightly –ELI-NP Scattered flux Luminosity as in HEP collisions –Many photons, electrons –Focus tightly –ELI-NP f cfr. LHC 10 34, Hi-Lumi LHC 10 35

Courtesy M. Gambaccini 300  rad 60  rad Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

Bandwidth due to collection angle, laser and electron beam phase space distribution electron beam laser

ELI-NP γ beam: the quest for narrow bandwidths (from down to ) Courtesy V. Zamfir – ELI-NP Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

Spectr. Density > 10 3 Spectr. Density = 1

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 courtesy of G. Travish (UCLA)

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 ELI-NP GBS (Extreme Light Infrastrucutre Gamma Beam System) Main Parameters outstanding electron 750 MeV with high phase space density (all values are projected, not slice! cmp. FEL’s) Back-scattering a high quality J-class ps laser pulse not sustainable by RF, Laser!

Accelerator and Equipments in ELI-NP Building

109 Authors, 327 pages published today on ArXiv

CIRCULATOR PRINCIPLE 2 high-grade quality parabolic mirrors –Aberration free Mirror-pair system (MPS) per pass –Synchronization –Optical plan switching  Constant incident angle = small bandwidth PARAMETERS = OPTIMIZED ON THE GAMMA-RAY FLUX Laser power = state of the art Angle of incidence (φ = 7.54°) Waist size (ω 0 = 28.3μm) Number of passes = 32 passes Optical system: laser beam circulator (LBC) for J-class psec laser pulses focused down to  m spot sizes 2.4 m 30 cm Electron beam is transparent to the laser (only 10 9 photons are back- scattered at each collision out of the carried by the laser pulse) courtesy K. Cassou 15

Unlike FEL’s Linacs, ELI-NP-GBS is a multi-bunch accelerator, therefore we need to control the Beam-Break-Up Instability to avoid complete deterioration of the electron beam emittance, i.e. of its brightness and phase space density ELI-NP-GBS High Order mode Damped RF structure Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 courtesy David Alesini

C-BAND STRUCTURES: HIGH POWER TEST SETUP The structure has been tested at high power at the Bonn University under RI responsibility. Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Successfully tested at full power (40 MW) courtesy David Alesini

FLASH (nm) Thomson/Compton Sources Brilliance of Lasers and X-ray sources BELLA Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 ELI Outstanding X/  photon beams for Exotic Colliders

A MeV-class Photon-Photon Scattering Machine based on twin Photo-Injectors and Compton Sources  -ray beams similar to those generated by Compton Sources for Nuclear Physics/Photonics issue with photon beam diffraction at low energy! Best option: twin system of high gradient X-band 200 MeV photo-injectors with J-class ps lasers (ELI-NP-GBS) Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

peak cross-section, ≈1.6 µbarn at cross-section for unpolarized initial state (average over initial polarizations) optical transparency of the Universe Tunability! Narrow bdw! courtesy E. Milotti Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

courtesy E. Milotti

threshold of the Breit-Wheeler process 1 nb pb -1 integrated luminosity corresponding to a bare minimum of about 100 scattering events (total). E CM ≈ 630 keV E CM ≈ 880 keV E CM ≈ 13 MeV E CM ≈ 140 MeV threshold of the Bethe-Heitler process Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 courtesy E. Milotti

We evaluated the event production rate of several schemes for photon-photon scattering, based on ultra-intense lasers, bremsstralhung machines, Nuclear Photonics gamma-ray machines, etc, in all possible combinations: collision of 0.5 MeV photon beams is the only viable solution to achieve 1 nbarn -1 in a reasonable measurement time. 1)Colliding 2 ELI-NP 10 PW lasers under construction (ready in 2018), h =1.2 eV, f=1/60 Hz, we achieve (E cm =3 eV): L SC = , cross section= , events/sec= )Colliding 1 ELI-NP 10 PW laser with the 20 MeV gamma-ray beam of ELI-NP-GBS we achieve (E cm =5.5 keV): L SC = , cross section=10 -41, events/sec = Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

3)Colliding a high power Bremsstralhung 50 keV X-ray beam (unpolarized, 100 kW on a mm spot size) with ELI- NP-GBS 20 MeV gamma-ray beam (E cm =2 MeV) we achieve: L SC = , cross section=1  barn, events/s = ) Colliding 2 gamma-ray 0.5 MeV beams, carrying 10 9 photons per pulse at 100 Hz rep rate, with focal spot size at the collision point of about 2  m, we achieve: L SC = , cross section = 1  barn, events/s= , events/day=18, 1 nanobarn -1 accumulated after 3 months of machine running. Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

Luminosities of Colliders involving Photon Beams at various c.m. energy Compton Sources: L=10 35 cm -2 s -1 at keV c.m. energy (ELI-NP-GBS like)  colliders for photon-photon scattering experiment and Breit-Wheeler: L=10 26 cm -2 s -1 at MeV c.m. energy Photon–photon collider with 2x10 PW ELI Laser (most powerful of this decade): L=10 45 cm -2 s -1 at 3 eV c.m. energy LHC proton (7 TeV) – XFEL photon (20 keV) collider : ultimate Luminosity (10 13 p 200ns, TW-FEL * as for LCLS-II SC-CW) L=10 38 cm -2 s -1 at 1.2 GeV c.m. energy * C.Pellegrini et al., PRSTAB 15, (2012) production of low emittance  / beams… Is it of any interest?

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Not a new idea.. but A.Dadi and C.Muller analyzed a multi-photon reaction and didn’t make evaluations of the phase spaces for the generated pion/muon beams

2 Ingredients to make a Collider Source of a low emittance (high phase space density, high brilliance) secondary beam Emittance of secondary beam generated in collision: combination of emittance of momentum-dominant beam (protons for LHC-FEL, electrons for Compton Sources) and transverse momentum in c.m. frame (-> transverse momentum is invariant to Lorentz boost, i.e. transverse temperature/emittance is also invariant to Lorentz boost) Large Lorentz boost to collimate within narrow solid angle (in the Lab frame) all reaction products, i.e.  cm >> 1 Energy available in c.m. frame as momentum of secondary particles much smaller than their invariant mass energy

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 h 20 keV FEL photon is seen as a 2.  p. h = 300 MeV by the proton in its rest frame (max total cross section of pion photo-production 0.25 mbarn)

Momentum in laboratory frame: FF nFnF nBnB BB Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Large Lorentz boost :  cm = 5830

Phase Space Distribution Results of a montecarlo event generator with (upper) and without (lower) LHC proton beam emittance (proton rms transv. momentum 200 MeV,  x’ = 20  rad) 20  rad 260 GeV/c   48  s 2.5 TeV/c   0.5 ms 2.5 TeV/c   50 ms 150 GeV/c   5 ms

stop-band at  =20  rad (200 MeV p transv. mom.) Populating the Phase Space: combination of p-beam transverse emittance (temperature) and stochastic transverse temperature increase due to decay sequence (p, h ) -> (  +, n) -> ( , ) n

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 outstanding pion beam emittance < 10 mm. mrad thanks to 7  m emitting source spot-size and low  + rms trans. momentum (150 MeV: p  x /m  =1)

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Luminosity issues and pion/muon/neutron/neutrinos fluxes a) Assuming LHC p-beam at intensity and 5 MHz rep rate vs photons/pulse SC-CW XFEL (run in long 200 fs pulse and tapering), focused down to 7  m rms spot size, we can get pions per bunch crossing (no collective beam-beam at IP w.r.t. p- p collisions) b) We have a pion photo-cathode: how to match the pion beam into a storage ring / transport line is an open problem… c) Assuming the low  -beam emittance can be preserved, we can accumulate muons over half ot their life-time (10-60 ms), reaching N  = , which is enough, at 5 MHz rep rate, to reach a muon collider luminosity of about cm -2 s -1, without need of cooling nor acceleration.

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 d) Life-time of p-beam is about 10 hours (taking into account also  0, e+/e- and Compton events) e)  - production requires deuteron beams (simultaneous production of  + and  - thanks to pion-photoproduction quasi-symmetric cross section on deuteron) f) Potentials for highly collimated neutrino and neutron beams in the 10 GeV – 1 TeV range Is it going to be an interesting alternative option for  -collider? Using FCC beams we would need 3 keV X-rays -> simpler and cheaper FEL (5-6 GeV Linac vs GeV Linac for 20 keV photons and larger number of photons)

A Compact (10 m, 10 M€) Demonstrator at SPS of a Pion Photo-cathode Compton Source: 10 9 h 350 keV vs. 400 GeV protons -> measure diff. cross. sect., phase space accumulation (1  / b. cross.)

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015 Thank you for your kind attention Special Thanks to: C. Meroni, A. Ghigo, D. Palmer on the pion beams. E. Milotti, C. Curceanu for material on the photon-photon scattering. D. Alesini, N. Bliss, F. Zomer, K. Cassou, A. Variola and the whole EuroGammaS collaboration on the ELI-NP-GBS Project.

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015

h 12 keV FEL photon is seen as a 2.  p. h = 180 MeV by the proton in its rest frame (max total cross section of pion photo-production 0.1 mbarn)