Transcript Diapositiva 1

The SPARX FEL Project
a source for coherent radiation
production in the soft X-ray
energy range
Main components of a Free Electron Laser
• an accelerator providing a bunched relativistic electron beam
• an undulator magnet
Electrons are not bound in atomic, molecular or solid-state
levels but are moving freely in vacuum
For visible or infrared light an optical resonator can be used
At l below 100 nm the reflectivity of metals and other mirror
coatings drops quickly to zero at normal incidence.
The principle of Self-Amplifified Spontaneous Emission (SASE)
allows the realization of high-gain FELs at these short l‘s
The Principle of Self-Amplified Spontaneous
Emission (SASE) X-FELs
Sparx
X-FEL
Fermi1
Fermi2
SPARX
SPARC
FLASH
~ 0.1
100  40
40  10
13  1
500  100
13  6.5
nm
nm
nm
nm
nm
nm
2013
2010
2011
2013
commissioning
in operation
100 nm ≈ 12 eV
h=6.6x10-34 J.s = 4.1 x 10 -15 eV.s
hn = 12 eV
n= 12 eV/h ≈ 3 x 10 15 s-1
l = c/n = 3 x 10 8ms-1/ 3 x 10 15 s-1= 10 -7 m = 100 nm
l = [h(eV.s).c]/E(eV)=(12.4 x 10 -7eV.m)/E(eV)
Peak brightness (brilliance) versus pulse duration
of various types of radiation sources
GE
UK
IT
GE
CH
IT
CH
Use of the FEL to help remove a tumor from the brain of a patient.
Unlike conventional lasers that produce light at given wavelengths,
the FEL beam can be tuned through a wide spectrum of colors. That
has allowed researchers to find the optimal wavelength (6.45µm) for
cutting cleanly through living tissue.
Free-electron laser used in
human brain/eye surgery
Explosion of T4 Lysozyme
X-ray intensity, I(t) = 3 x 1012 (12 keV~1Å) photons per 100-nm
diameter spot (3.8 x 106 photons per Å2)
Neutze et al. Nature (2000) 406:752
l = [h(eV.s).c]/E(eV)=(12.4 x 10 -7eV.m)/E(eV)
CCD detector
recording a continuous
diffraction pattern
A coherent diffraction
pattern of the object
recorded from a single
25-femtosecond FEL
pulse
Reconstructed image
No sign of radiation
damage
Diffraction pattern
from the
subsequent pulse
The first pulse
destroyed the object
after recording the
image
Schematic depiction of single-particle coherent diffractive imaging
with an XFEL pulse
K.J. Gaffney, H.N. Chapman
Science 316, 1444 (2007)
plasma formation
Coulomb explosion
The image is then
obtained by phase
retrieval
The Importance of the Phase Information
(a)
Fourier amplitude of (a)
+ Fourier phases of (b)
(b)
Fourier amplitude of (b)
+ Fourier phases of (a)
The First Experimental Demonstration
(a)
A Scanning Electron
Microscopy image
(b)
An oversampled
diffraction pattern
(c)
Miao, Charalambous, Kirz & Sayre,
Nature 400, 342 (1999).
Image reconstructed from (b)
FLASH: 45 proposals 32 approved
Henry Chapman:
Flash Diffraction Imaging of Biological Samples
Tor Vergata FEL colloquia
March, 19, 2008 – Prof. Giorgio Margaritondo
Ecole Polytechnique Fédérale de Lausanne, Switzerland
"Coherent Radiology - from Synchrotrons to Free Electron Lasers"
Aprile, 2, 2008 – Prof. Jianwei (John) Miao
Department of Physics and Astronomy, Univ. of California, USA
"Coherent Scattering, Oversampling and Applications of X-ray Free
Electron Lasers"
April, 23, 2008 – Prof. Janos Hajdu
Structural Biology Labs Biomedical Centre, Uppsala, Sweden
“TBA”
June, 18, 2008 – Prof. Massimo Altarelli
European X-ray Free-Electron Laser Project Team, DESY,Germany
“The European X-ray Free-Electron Laser Project in Hamburg”