Download - Channeling Studies at LNF
Channeling Studies at LNF
Sultan B. Dabagov on behalf of CUP & X collaboration: LNF +
Mainz + Aarhus About radiation features: for e+ BTF and for 150 MeV
e-; Simulations by Babaev & Tomsk group; @ Free Electron Laser
Self-Amplified-Spontaneous-Emission
(No Mirrors - Tunability Harmonics) SEEDING FEL project at Frascati
Channeling @ FEL activity at LNF MAMBO
Channeling FEL project at Frascati Source Pulsed SelfAmplified
Radiation Coherent SEEDING @ SPARC & Applications Plasmon 14.5
m 1.5m 10.0 m 5.4 m 11
quadrupoles dipoles Diagnostic 1-6 Undulator modules Photoinjector
solenoid RF sections Plasmon Thomson RF deflector collimator 25 FEL
Application Bunch charge (nC) Energy (MeV) Bunch length rms (ps)
Norm. rms emittance (mm) Energy Spread (%) PlasmonX 0.025 0.1 0.2
Thomson 1-3 28-200 3 2-5 @ Channeling of Charged Particles
@ Amorphous: @ Channeling: Atomic crystal plane planar channeling e
+ e- Atomic crystal row (axis) axial channeling e- - the Lindhard
angle is the critical angle for the channeling @ Channeling of
Charged Particles & Channeling Radiation
Atomic plane of crystal e + - the Lindhard angle is the critical
angle for the channeling @ Channeling Radiation: - optical
frequency Doppler effect - 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
undulator and -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). Powerful radiation source of X-rays and -rays: polarized
Tunable (keV - MeV) narrow forwarded @ Channeling: Continuum
model
screening function of Thomas-Fermi type screening length Moliers
potential Lindhard potential Firsov, Doyle-Turner, etc. Lindhard:
Continuum model continuum atomic plane/axis potential @ Channeling
Radiation
- optical frequency Doppler effect - Powerful radiation source of
X-rays and -rays: polarized tunable narrow forwarded @
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: Nph Quantum energy @ 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 Nph Quantum energy @ Bremsstrahlung & Coherent
Bremsstrahlung vs Channeling Radiation
@ crystal: d channeling at definite conditions channeling radiation
can be significantly powerful than bremsstrahlung B: CB: ChR: @
Channeling Radiation & Thomson Scattering
- radiation frequency - - number of photons per unit of time - -
radiation power - @ comparison factor: Laser beam size & mutual
orientation @ strength parameters crystal & field: @ Channeling
Radiation & Thomson Scattering
For X-ray frequencies: 100 MeV electrons channeled in 105 mm Si
(110) emit ~ 10-3 ph/e- corresponding to a Photon Flux~ 108 ph/sec
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 @ BTF Layout 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 MeV positrons e+ g Crysral undulator
High background/noise @ Positron Channeling in Si-Ge Undulator @
Positron Channeling in Si-Ge Undulator @ Dechanneling of positrons
@ Theoretical estimations: need for small divergence @ Theoretical
estimations: feasibility of observation @ Experimental Setup at BTF
@ Crystal characterization: MAMI 855 MeV e- @ Radiation record at
BTF 600 MeV e+
No evidence for channeling / channeling radiation X-ray channeling:
flux peaking @ down to bulk x-ray channeling
mm l : grazing incidence optics : from nm to mm : surface
channeling nm l : diffraction angle approaches Fresnel angle : bulk
channeling As is well known from quantum mechanics, any well is
able to support at least one quantum bound state (channeling
state); the number of bound states can be estimated from the
expression for the potential (4). Equation (3) for radiation
propagation in a medium with the potential (4) can be solved for
the case of -guides as well as for the n-guides. The basic dierence
of radiationpropagation in - and n-channels is dened by the ratio
between the eective guide-channel size and the transverse
wavelength of radiation (Fig. 1). The guiding channel is dened by
its shape in -channels (collimation prole or surface curvature)
whereas for n-channels - by the transverse channel size. Multiple
reflections:
@ Simulations for x channeling (straight & bent) Angular
distributions Spatial Coherent scattering: 0-L0 Multiple
reflections: L0-20L0-103L0 Angle of incidence 0.5 critical angle of
channeling @ Simulations for x channeling: bending of
radiation
Evolution of angular distribution rcurv ~ 2 m : Strong bending
effect @ wave field formation in a planar waveguide
Diffraction from Si corner (gap 30 nm; =0.1 nm): (a) analytical
solution; (b) computer simulation @ planar n-guide :: quantum
states of channeling
:: character of radiation transmission :: :: the ray optics
approach for describing radiation propagation = 2a/ = 2a/c [c = /c
]:: the number of bound modes N. >> 2 N 1 :: the geometric
optics approximation >> 2 a >> c [glassc= 40 nm] Thus
for a wide waveguide a 40 nm there are many bound modesand multiple
reflection of rays can be used. In the other limit