Challenges and Opportunities of high intensity X/g 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/g beam Sources using Compton back-scattering
• Need of high peak brightness/high average current electron
beams (cmp. FEL’s drivers) fsec-class synchronized and mmmrad-scale aligned to high peak/average power laser beams
• Main goal for Nuclear Physics and Nuclear Photonics:
Spectral Densities > 104 Nph/(s.eV)
(state of the art: HigS 300, bremsstrahlung sources 1)
photon energy range 1-20 MeV, bandwidths 10-3 class
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
• Main goal for MeV-class g - g and TeV g - nucleon colliders:
Peak Brilliance > 1021 Nph/(s.mm2.mrad2.0.1%) 109<Nph<1013
Source spot size mm-scale (low diffraction, few mrad)
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 g-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
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/g ray beam,
is a completely different issue/business !
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
Courtesy L. Palumbo
Compton Inverse Scattering Physics is clear: recall some basics
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
Courtesy V. Petrillo
4 0
g 
  collective effects
1  4 gh 0 
2 1
2 
2g 
mc 
4 0g 2
g 
1 -  
2 2
2
1 g   a0 2
4gh 0

mc 2
 1 Compton recoil
0  2.4 eV (0  500 nm)
Thomson  g 2


Compton

X/g
[MeV]

Compton  Thomson1 - 

1 GeV
Compton
Thomson
Te [MeV]

Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
1 TeV
We need to build a very high luminosity collider,
that needs to maximize the Spectral Luminosity,
i.e. Luminosity per unit bandwidth
 T  0.67 10-24 cm 2  0.67 barn
8 2
re
3
• Scattered flux Ng  L T
• Luminosity as in HEP collisions
T 
– Many photons, electrons
N L N e- f
– Focus tightly
L
4  x2
negligible diffraction
0 crossing angle
electrons
laser
– ELI-NP
LS 
L
g
1.3 1018  1.6 109
-1
35
-2 -1
L
2 3200(s )  2.5 10 cm s
4 0.0015cm

cfr. LHC 1034, Hi-Lumi LHC 1035
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
300 mrad
60 mrad
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
Courtesy M. Gambaccini
Bandwidth due to collection angle, laser and
electron beam phase space distribution
4g 2
g  
1 - 
2 2
2
1 g   a0 2
4g h mc 2

1 2g h mc 2
 1 Compton recoil
2
2
g 2 2  g 2 2  g 2 e2  g 2 rms
 ( p /mc) 2  g 2 rms
 2( n / x ) 2

2
4
4
2
2
2
2


 g   2 n      M L 
a0 p /3
g
4

 (g ) rms  4   
   
  
2
g
 g    x      2w0  1 a0 p /2 
g  normalized
collection angle
electron beam
laser
Optimized Bandwidth  2( n / x ) 2
Maximum Spectral Density  Luminosity /( n / x ) 2  Q / n2
Maximum Spectral Density  Phase Space density
ELI-NP γ beam: the quest for narrow
bandwidths (from 10-2 down to 10-3)
Courtesy V. Zamfir – ELI-NP
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
Spectr. Density = 1
Spectr. Density > 103
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
courtesy of G. Travish (UCLA)
ELI-NP GBS (Extreme Light Infrastrucutre Gamma Beam System)
Main Parameters
g - ray 1 - 20 MeV ; rms Bandwidth 3. - 5. 10
-3
Spectral Density : 10 3 -10 4 photons/s eV
needs 3.10
5
photons/ pulse @ 3 kHz rep rate
rms divergence 30  300 mrad
linear or circular polarization  98%
outstanding electron beam @ 750 MeV with high phase space density
(all values are projected, not slice! cmp. FEL’s)
Q  250 pC
;  n  4.10 -7 m rad ; g g  5 10 -4
Back-scattering a high quality J-class ps laser pulse
U L  400 mJ ; M  1.2 ;
2
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015


not
 5 10 sustainable
by RF, Laser!
-4
Accelerator and Equipments
in ELI-NP Building
109 Authors, 327 pages
published today on ArXiv
http://arxiv.org/abs/1407.3669
Optical
system: laser
beam
(LBC) are backElectron beam
is transparent
to the
lasercirculator
(only 109 photons
for J-class
psec
laser pulses
down tobymthe
m spot
scattered
at each
collision
out of focused
the 1018 carried
lasersizes
pulse)
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 (ω0 = 28.3μm)
Number of passes = 32 passes
30 cm
courtesy K. Cassou
ELI-NP-GBS High Order mode Damped RF structure
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
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.
Successfully tested at full power (40 MW)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
courtesy David Alesini
Brilliance of Lasers and X-ray sources
ELI
N ph  10 -10
19
20
12.4
1.24
0.124
N ph  1011 -1013
BELLA
t  10 - 200 fs
t  10 - 20 fs
B

FLASH
N ph
2t M  
2
2
 (nm)



N ph  10 8 -10 9
t  100 fs - 5 ps

Outstanding X/g photon beams
for Exotic Colliders
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015


BCompton  g 2
A MeV-class Photon-Photon Scattering Machine based on
twin Photo-Injectors and Compton Sources
• g-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
6
æ w ö
s » 0.13ç
2 ÷ mbarn
è me c ø
peak cross-section, ≈1.6 µbarn
at w » 1.5mec2
2
æ me c ö
s » 20ç
÷ mbarn
è w ø
2
s (mbarn)
Tunability!
Narrow bdw!
cross-section for unpolarized initial state
(average over initial polarizations)
optical transparency
of the Universe
ECM (MeV)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
courtesy E. Milotti
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
courtesy E. Milotti
s u ( mbarn )
threshold of the
Breit-Wheeler
process
threshold of the
Bethe-Heitler
process eg ® ee+ e-
integrated luminosity corresponding
to a bare minimum of about 100
scattering events (total).
1 nb-1
ECM ≈
880 keV
ECM ≈
13 MeV
s gg
10 pb-1
s BW ·10 -6
ECM ≈
630 keV
ECM ≈
140 MeV
ECM ( MeV)
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 (Ecm=3 eV):
LSC=6.1045, cross section= 6.10-64, events/sec=10-19
2)Colliding 1 ELI-NP 10 PW laser with the 20 MeV gamma-ray
beam of ELI-NP-GBS we achieve (Ecm=5.5 keV): LSC=6.1033,
cross section=10-41, events/sec = 10-8
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 ELINP-GBS 20 MeV gamma-ray beam (Ecm=2 MeV) we
achieve: LSC=6.1022, cross section=1 mbarn, events/s =
10-8
4) Colliding 2 gamma-ray 0.5 MeV beams, carrying
109 photons per pulse at 100 Hz rep rate, with focal
spot size at the collision point of about 2 mm, we
achieve: LSC=2.1026, cross section = 1 mbarn,
events/s=2.10-4, 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=1035 cm-2s-1 at 1-100 keV c.m. energy
(ELI-NP-GBS like)
• g-g colliders for photon-photon scattering experiment and
Breit-Wheeler: L=1026 cm-2s-1 at 0.5-2 MeV c.m. energy
• Photon–photon collider with 2x10 PW ELI Laser (most
powerful of this decade): L=1045 cm-2s-1 at 3 eV c.m. energy
• LHC proton (7 TeV) – XFEL photon (20 keV) collider : ultimate
Luminosity (1013 p 200ns, TW-FEL* as for LCLS-II SC-CW)
L=1038 cm-2s-1 at 1.2 GeV c.m. energy
*C.Pellegrini
et al.,
PRSTAB 15, 050704 (2012)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
production of low
emittance /m//
beams…
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
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
2 Ingredients to make a Collider Source of a low emittance
(high phase space density, high brilliance) secondary beam
• Large Lorentz boost to collimate within narrow solid angle (in
the Lab frame) all reaction products, i.e. gcm >> 1
• Energy available in c.m. frame as momentum of secondary
particles much smaller than their invariant mass energy
 n   x px ;  px 
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)
1.5
pLHC
 7 mm   px

938  200 MeV ( x   19 mrad)
7
p
px  x  x g
mc

 npLHC 1.5 mrad ;  xpLHC
px2
h 20 keV FEL photon is seen as a 2. gp. h = 300 MeV by the proton in its
rest frame (max total cross section of pion photo-production 0.25 mbarn)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
Momentum in laboratory frame:
7
nF
|p|, |p|n(TeV/c)
6
5
nB
4
F
3
2
1
0
B
0,00
0,05
0,10
0,15
0,20
 angle (mrad)
Large Lorentz boost : gcm = 5830
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
0,25
Phase Space Distribution Results of a montecarlo event generator
with (upper) and without (lower) LHC proton beam emittance
2.5 TeV/c
t 0.5 ms
260 GeV/c
t 48 ms
(proton rms transv. momentum 200 MeV, x’ = 20 mrad)
2.5 TeV/c
tm 50 ms
150 GeV/c
tm 5 ms
20 mrad
Populating the Phase Space: combination of p-beam transverse emittance
(temperature) and stochastic transverse temperature increase due to decay
sequence (p, h) -> (+, n) -> (m,) n
stop-band at =20 mrad
(200 MeV p transv. mom.)
outstanding pion beam emittance < 10 mm.mrad thanks to 7 mm 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 1013 intensity and 5 MHz rep rate vs.
1013 photons/pulse SC-CW XFEL (run in long 200 fs pulse and
tapering), focused down to 7 mm rms spot size, we can get 6.104
pions per bunch crossing (no collective beam-beam at IP w.r.t. pp 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 Nm=3.109 , which is enough, at 5 MHz rep rate, to reach
a muon collider luminosity of about 1031 cm-2s-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 m-collider?
Using FCC beams we would need 3 keV X-rays -> simpler and
cheaper FEL (5-6 GeV Linac vs. 15-18 GeV Linac for 20 keV
photons and larger number of photons)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
A Compact
10 M€)
Demonstrator
SPS
of a
9 hm,
Compton
Source: 10(10
/pulse
@ 350
keV vs. 400 at
GeV
protons
Photo-cathode
-> measure diff. cross. sect.,Pion
phase
space accumulation (1  / b. cross.)
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
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015
h 12 keV FEL photon is seen as a 2. gp. h = 180 MeV by the proton in its
rest frame (max total cross section of pion photo-production 0.1 mbarn)
Future Res. Infrastr., Challenges and Opportunities, Varenna, July 9th 2015