Post on 13-Feb-2019
Channeling Experiments at DAFNE BTF for the
Development of a Crystal Undulator for Positrons
“CUP”
S.B. Dabagov, C. Natoli, L. Quintieri
… in collaboration with SPARC, Aarhus, Mainz & Frankfurt teams…
CUP project studies the positron channeling for the development of Crystal
Undulator for Positrons and represents the first step of an ambitious project
that investigates the possibility to create new, powerful sources of high-
frequency monochromatic electromagnetic radiation: crystalline undulatorand -laser, based on crystalline undulator. The physical phenomena to
investigate are essentially two: the spontaneous undulator radiation by
channeling of relativistic positrons and the stimulated emission in
periodically bent crystals (the lasing effect).
Free Electron LaserFree Electron Laser
Self-Amplified-Spontaneous-EmissionSelf-Amplified-Spontaneous-Emission
(No Mirrors - Tunability - Harmonics)(No Mirrors - Tunability - Harmonics)
Channeling Radiation & Coherent Bremsstrahlung
MAMBOMAMBO
+ ChannellingChannelling
FEL project at FEL project at FrascatiFrascati
SSourceource
PPulsedulsed
SelfSelf AAmplifiedmplified
RRadiationadiation
CCoherentoherent
Self-Amplified PulsedSelf-Amplified Pulsed Coherent Radiation SourceCoherent Radiation Source
Channeling: Orientational Effects of Transmission & Radiation
Rev. Mod. Phys. 1974: 1 MeV e- @ Cu crystal
• 1962-63:
Robinson &
Oen: Prediction of anomalous penetrationPiercy &
Lutz: Experimental discovery• 1965:
Lindhard: Theoretical description…..
Andersen
Uggerhoj Classical theoryKagan Quantum theoryKononez
Firsov
Tsyganov
Gibson
Kumakhov
Beloshitsky
Gemmel
Appleton
…..
more than 1000 articles + a number of monographs
Prediction of channeling radiation (ChR)
Experimental confirmation: positron channeling in diamond crystal
USSR-USA collaboration, SLAC 1978
JETP Lett. 1979 (Miroshnichenko, Avakyan, Figut, et al.)
@ Channeling:
e+
Atomic crystal plane
)~(1E
UL
<<< - the Lindhard angle is the critical angle for the channeling
Channeling of Charged Particles
Atomic crystal row (axis)
e-
e-
planar channeling
axial channeling
@ Amorphous:
@ Channeling:
e+
Atomic plane of crystal
@ Channeling Radiation:
)~(1E
UL
<<< - the Lindhard angle is the critical angle for the channeling
cos1)(
||
==fi
- optical frequency Doppler effect 2/30
20-
Powerful radiation source of X-rays and -rays:
•polarized
•Tunable (keV - MeV)
•narrow forwarded
fi
( )1>>
Channeling of Charged Particles & Channeling Radiation
Lindhard:
Continuum model –
continuum atomic plane/axis potential
Channeling: Continuum model
( ) ( )arr
eZZrV
2
21=
screening function of Thomas-Fermi type
( ) 3/22/1
2
2/1
108853. += ZZaa
screening length
( ):ar Molier’s potential( )arii
i=
exp3
1
3112
2/1
2+ C
r
CaLindhard potential
…… Firsov, Doyle-Turner, etc.
( ) ( )+
+= dxxVd
VRS
221
Channeling Radiation…
@ Channeling Radiation:
cos1)(
||
==fi
- optical frequency Doppler effect 2/30
20-
Powerful radiation source of X-rays and -rays:
•polarized
•tunable
•narrow forwarded
fi
( )1>>
Bremsstrahlung & Coherent Bremsstrahlung vs Channeling Radiation
@ amorphous - electron:
•Radiation as sum of independent impacts with atoms
•Effective radius of interaction – aTF
•Coherent radiation length lcoh>>aTF
•Deviations in trajectory less than effective radiation angles:
paTF /
Quantum energy
Nph
Bremsstrahlung & Coherent Bremsstrahlung vs Channeling Radiation
@ interference of consequent radiation events:
phase of radiation wave
Radiation field as interference of radiated waves:
Coherent radiation length can be rather large even for short wavelength
@ crystal:
d
Quantum energy
Nph
Bremsstrahlung & Coherent Bremsstrahlung vs Channeling Radiation
@ crystal:
d
0
channeling
3/22/1Z
B
ChR at definite conditions channeling radiation can be significantly powerful
than bremsstrahlung
B: CB: ChR:
2NZ
NZe
( )2NZ
effcoh NlN /2
( )2ZNeff
ChRChR
lab 022
2
1
2
+
2/1
ChR
ph
dt
dN
2P
- radiation frequency -
- number of photons per unit of time -
- radiation power -
Channeling Radiation vs Thomson Scattering
Constdt
dN
TS
ph
2P
2/32
@ comparison factor:
Laser beam size & mutual orientation
@ strength parameters – crystal & field:
For X-ray frequencies: 100 MeV electrons channeled in 105 μm Si (110) emit ~ 10-3 ph/e-
corresponding to a Photon Flux ~ 108 ph/sec
Channeling Radiation vs Thomson Scattering
ChR – effective source of photons in very wide frequency range:
• in x-ray range – higher than B, CB, and TS
• however, TS provides a higher degree of monochromatization and TS is not
undergone incoherent background, which always takes place at ChR
_The important and novel idea consists in realizing a microundulator, that is a suitable periodically
bent crystal, that allows to achieve much higher energy range for the emitted photons respect to the
conventional free electron laser (up to 100 keV). A crystalline undulator can be realized either
dynamically, using high amplitude transverse acoustic wave, or statically using graded composition of
strained layers. Both methods are easily applicable by means of modern technology.
The theoretical results establish the feasibility of a crystalline undulator, but in order to make the
project to advance it is mandatory to carry out experiments to test the idea and to characterize the
emitted radiation as a function of several parameters.
Bent Crystal as Microundulator & Lasing Effect
BTF Facility for Channeling Studies
• BTF as unique European facility to deliver positron beams in the range of the
energy required for CUP
• strong photon peak with energy from 20 keV up to 1,5 MeV should appear
according well accepted channeling and undulator theories for
400-600 MeV positrons
Piano Finanziario Globale
4610-10188
266-51052009
204-5832008
Totale,k
CostruzioneApparati, k
MaterialiInvent., k
MaterialiConsumo, k
MissioniEstere, k
MissioniInterne, k
ANNI
Electron Beam Parameter list
1Rms bunch length @ linac exit (mm)
0.4Rms beam spot size @ linac exit (mm)
0.06Rms incorrelated energy spread (%)
0.2Rms total correlated energy spread (%)
1000Rms longitudinal emittance (deg.keV)
< 1Rms slice norm. emittance (300 μm slice)
< 2Rms normalized transverse emittance @ linac exit
(mm-mrad); includes thermal comp. (0.3)
100Bunch peak current @ linac exit (A) (50% beam
fraction)
5.6Bunch energy @ gun exit (MeV)
1Laser pulse rise time (ps) 10% 90%
10Laser pulse duration, flat top (ps)
33Central RF launch phase (RF deg)
1.13Photocathode spot size (mm, hard edge radius)
0.273Peak solenoid field @ 0.19 m (T)
120Cathode peak field (MV/m)
1-10Repetition rate (Hz)
1.1Bunch charge (nC)
155Electron Beam Energy (MeV)
We have started collaboration with groups from:
Italy, Russia, USA, France, Germany, Switzerland,
Ukraine, Belarus, Armenia
…list will be extended…
Collaboration & Acknowledgements
The Scientific Case in the 10 nm 1 nm range:High Peak Brightness ( > 1030 ) Ultra-short (< 100 fs) radiation pulses are of
great interest in various areas
• molecular physics (vibrational modes, bond breaking and formation at
=10-1 nm)
• physics of the clusters (phase transitions at =10-1 nm,)
• surface and interfaces (real time dynamics and phase transitions, =10-
1 nm)
• time resolved chemical reactions (metastable and transition states,
magnetic scattering, confined systems, =10-1 nm)
EEx x 22 22laslas (1-cos (1-cos ))
• Produzioni di impulsi X :
101099 fotoni/s fotoni/s, durata 3 ps, monocromaticimonocromatici
tunabili nel range 20 keV - 1 MeV20 keV - 1 MeV.
Raggiungimento di 10101111 fotoni/s fotoni/s con spot focali
all’interazione di 5 5 μμmm.
• Studi di tecniche di mammografia (e angiografia
coronarica) con X monocromatici.
• Studi di single molecule protein cristallography.
NX T fN
eNh
coll2 = 2 109 / 11
Accelerazione a plasmaAccelerazione a plasma di pacchetti di elettroni ( di pacchetti di elettroni (25 pC25 pC) da) da
100 MeV a 130 MeV100 MeV a 130 MeV con spread energetico < 5%, emitt. con spread energetico < 5%, emitt.
< 1 < 1 μμm, con laser non guidato (5 mm acc. length).m, con laser non guidato (5 mm acc. length).
Accelerazione con laser guidato (Accelerazione con laser guidato (5 cm5 cm) fino a 400 MeV,) fino a 400 MeV,
gradienti > 5 GV/mgradienti > 5 GV/m..
p 50 μm
p 30 100 μmnnpnp
p
2