Giuseppe Dalba
Department of Physics, University of Trento - Italy
Giuseppe Dalba, University of Trento, Italy
Outline
1. Mechanisms for X-ray production
Charge acceleration: bremsstrhalung
Electronic quantum transitions
2. X-ray tubes for X-ray diffraction measurements
3. Principles of synchrotron radiation
Synchrotron Radiation:
What is it?
How is it produced?
Which are their properties?
… which the main uses?
Giuseppe Dalba, University of Trento, Italy
Electromagnetic Radiation and Structure of matter
Synchrotron ligh sources
The shorter the wavelength, the greater the resolution for observing small object
Synchrotron radiation sources span wide regions of the electromagnetic spectrum
Giuseppe Dalba, University of Trento, Italy
Who are the responsibles of light emission?
From a candle?
da una lamfrom a lamppada?
From lasers?
By a broadcasting
antenna?
The amin responsible are the electrons
Giuseppe Dalba, University of Trento, Italy
Radiation production mechanisms
There are two ways to produce synchrotron radiation:
Classical mechanism: acceleration of charged particle (for instance, electrons
and positrons)
Bremsstrahlung: deceleration of high
energy electrons in a metal
Synchrotron radiation emitted by relativistic
charged particles in particle accelerators
Cosmic synchrotron radiation
Quantum mechanism: transitions of electrons from outer to inner empty energy
levels
Emission lines
Kα
Kβ
Characteristic radiation
Giuseppe Dalba, University of Trento, Italy
X ray production by tubes
Vacuum tube
Kα
HV
X-rays
Cathode
Electrons
Intensity (a. u.)
Anode
Characteristic
radiation
λmin
0.02
Filament
supply
Kβ
0.04
0.06
Bremsstrahlung
radiation
0.08
0.10
Wavelength (nm)
The spectrum from an X ray tube has discrete fluorescent lines superimposed on
the continuous bremsstrahlung radiation
Giuseppe Dalba, University of Trento, Italy
Spectra of different anodes
Characteristic lines
Bremsstrhalung spectrum
Relative intesity
Relative intesity
Kβ
I
I
50 kV
40 kV
30 kV
Kβ
Kα
Kα
Mo
Cu
20 kV
0.02 0.04 0.06 0.08 0.1
λ (Å)
Giuseppe Dalba, University of Trento, Italy
0.5
1.0
λ (Å)
1.5
Distribuzione spettrale
X-rays
Realtive
intensity
e-
1 λ2
λ, (Å)
Thin anode
Relative intensity
X-rays
eX-rays
Thick
anode
Strato 6
5
4
3
Primo 2
strato 1
Wavelenghth λ, (Å)
The continuous spectrum emitted by a thich anode can be considered as the sommation
of spectra emitted by thin layers of the anode
Giuseppe Dalba, University of Trento, Italy
Electronic transitions and K emission lines
Quantum numbers
n l j
3 2 3/2
NII
I
3p
3 l 1/2
M
3s
3 0 !/2
Selection rules
Δn ≠ 0
Δl = ±1
Δj = ±1 o 0
2 l 3/2
2p
2 l 1/2
2 0 1/2
L
2s
α2
α1
β2
β3
1 0 1/2
β1
1s
K
Simplified diagram of transitions from energy states characteristic of the
K emission line series
Giuseppe Dalba, University of Trento, Italy
Characteristic spectrum
It consists of series of discrete lines whose
energy is equal to the energy difference of two
atomic levels.
K
Each element has its own characteristic spectrum
L
Line emission denomination
M
Siegbahn
K? 1
K? 2
K? 1
K? 2
K? 3
IUPAC
Siegbahn
IUPAC
L? 1
L? 2
L? 1
L? 2
L? 3
L? 4
L3-M5
L3-M4
L2-M4
L3-N5
L1-M3
L1-M2
K-L3
K-L2
K-M3
K-N2,N3
K-M2
Giuseppe Dalba, University of Trento, Italy
Moseley law
Relationship between the atomic number of an element and the energy of its
spectral emission lines
E (Z ) = k j (Z − σ j )
energy
X-rayLine
Charact.
Energy [K
[keV]eV]
2
120
100
80
60
40
Kβ 2
Kβ 1
Kα 1
Kα 2
Kα1
Kα2
Kβ1
Kβ2
Lα1
Lα2
Lβ1
Lβ2
L β1
20
0
Lα 2
20
40
60
80
Atomic number
Number Z Z
Atomic
In terms of wavelenghth, the previous equation is:
Giuseppe Dalba, University of Trento, Italy
λ∝
1
Z2
Giuseppe Dalba, University of Trento, Italy
Target materials and associated constants
Z
Cr
Fe
Cu
Mo
24
26
29
42
kα1,
(Å)
2.2896
1.9360
1.5405
0.70926
kα2,
(Å)
2.2935
1.9399
1.5443
0.71354
Kα1-2, (Å)
2.2909
1.9373
1.5418
0.71069
kβ1,
2.0848
1.7565
1.3922
0.63225
β filter
V
Mn
Ni
Nb
α filter
Ti
Cr
Co
Y
(Å)
Giuseppe Dalba, University of Trento, Italy
Cooling water
Cooling water
Be window
X-ray beam
X-ray beam
e-
Vacuum
Anode
Be window
Focal spot
viewed from side
Focal spot
viewed from the front
Giuseppe Dalba, University of Trento, Italy
Angular distribution of the radiation emitted by an X-ray tube
Electronic beam
e-
X-ray radiation
Anode
Electronic beam
e-
ys
X-ra
Focal spot
θ = 6°
Anode
Giuseppe Dalba, University of Trento, Italy
tion
a
v
r
e
Obs ction
dire
to 37.2
Relative emission intensity
18
16
14
Mo
Kα
Mo
Kβ
12
10
8
6
4
2
0
0
.2
.4
.6
.8
1.0 1.2 1.2
λ (Å)
Giuseppe Dalba, University of Trento, Italy
Relative absorption intensity
16
14
12
10
8
6
4
2
0
0
.2
.4
.6
.8
λ (Å)
18
to 37.2
16
14
12
Mo
Kα
Mo
Kβ
10
8
6
4
2
0
1.0 1.2 1.2
Zr filter
0
.2
.4
.6
.8
λ (Å)
White beam
beam
Giuseppe Dalba, Universitymonochromatized
of Trento, Italy
1.0 1.2 1.2
Charged particles moving in circular motion radiate
Larmor Formula
P = Electromagnetic power
q = charge
a = centripetal acceleration
S = Pointing
vector
vv << c
The
The radiation
radiation angular
angular distribution
distribution
of
of non-relativistic
non-relativistic electrons
electrons has
has
the
the shape
shape of
of aa tire
tire orbiting
orbiting at
at the
the
same
same velocity
velocity of
of the
the electron
electron bunch
bunch
Giuseppe Dalba, University of Trento, Italy
Synchrotron radiation angular distribution
Electron orbit
Electron orbit
Acceleration
v
Acceleration
e-
e-
v << c
m0 = electron mass
v = electron velocity
E = electron energy
c = velocity of light
Θ ≅ m0c2/E
= 1/γ rad
v≅c
v
Top view
Radiation angular distribution (a) electrons travelling at low speed
(b) electrons travelling at relativistic speed (γ = (1-v2/c2)-1/2 ≅ 10000 at ESRF)
Giuseppe Dalba, University of Trento, Italy
Synchrotron light from a storage ring
1m
Synchrotron light
BM
R.F. cavity
BM
Undulator
BM
Bending magnet, BM
BM
BM
Wiggler
injector
BM
BM
Synchrotron light
Animation
Three types of magnetic systems
Giuseppe Dalba, University of Trento, Italy
Beamline
Elettra
Giuseppe Dalba, University of Trento, Italy
Properties of synchrotron radiation
Bending magnets
Bending
Magnets
Wigglers
Wigglers
Wigglers
Undulators
High collimation
?
High flux
Θ ≅1/γ rad
BM
I
ID
Wide spectrum
Brillance
λ
Polarization
E
I
Temporal structure
t
Giuseppe Dalba, University of Trento, Italy
Spectral distributions of different sources
flux
wavelength
Intensity and spectral range of synchrotron radiation sources are several order
of magnitude greater than those of rare gas discharge lamps.
Giuseppe Dalba, University of Trento, Italy
From the magnetic device to the experimental station
Synchrotron storage ring
300 m
5m
Spectrometer
Focusing
device
Undulator
Monochromator
2m
30 m
10 m
Als-Nielsen Introduction to Modern X-ray Physics
Giuseppe Dalba, University of Trento, Italy
ESRF - Grenoble
CNRS
EMBL
ILL
ESRF
The greatest concentration of laboratories in matter Physics in Europe
Giuseppe Dalba, University of Trento, Italy
The Grenoble machine
300 m
Beamlines
The European Synchrotron Radiation Facility (ESRF)
Giuseppe Dalba, University of Trento, Italy
ESRF beamlines
ESRF
Each beamline hosts one or more specialized experimental stations
Giuseppe Dalba, University of Trento, Italy
Diffraction
Sample
I
X-rays
angle
Detector
Small angle scattering
X-rays
Sample
I
Detector
angle
Inelastic scattering
X-rays
Detector
Giuseppe Dalba, University of Trento, Italy
Energy shift
Fluorescence
Elemental analysis
I
Detector
X-rays
Sample
wavelength
Absorption
µ
2.0
1.0
X-rays
Sample
Detector
0.0
8800
9000
Imaging
X-rays
Detector
Giuseppe Dalba, University of Trento, Italy
9200
9400
9600
E (eV)
Energy
9800
10000
Laue Diffraction
Low flux
beam
High flux
beam
Synchrotron light, Springer-Verlag Compact Disk 2000
Giuseppe Dalba, University of Trento, Italy
Laue pattern of a crystal of metabolic
enzyme isocitrate deydrogenase
NSLS Brookhaven
Time resolved crystallography: Exposure time: 10 ms
Giuseppe Dalba, University of Trento, Italy
Biology
The functions of the life molecules, like proteins and nucleic acids, depend
on three-dimensional atomic structure. For instance the knowledge of viruses
has allowed the preparation of anti-viruses compounds to be prepared
Diffraction is the technique to study the molecular structure of biological systems
Giuseppe Dalba, University of Trento, Italy
Film of molecular process
The myoglobine molecule
iron site
a CO molecule interacting
with a myoglobine
molecule
Giuseppe Dalba, University of Trento, Italy
The life construction plan reported by the genetic code
The collection of precise information on the molecular structure of chromosomes
and their components can improve the knowledge of how the genetic code of DNA
is maintained and reproduced
Reconstruction of the molecular structure of nucleosome with a resolution of .2 nm
Giuseppe Dalba, University of Trento, Italy
Study o materials under extreme conditions
High pressures and temperatures
Cella di diamante
In laboratory it is possible to reach pressures of some milions of atm (100 Gpa)
comparable with those present in the Earth nucleus
Iron is the dominant element present in the nucleus of
the Earth. The knowledge of iron properties at high
temperature and pressure is fundamental for Earth
science. At ESRF a new orthorombic phase of Fe has
been discovered at 45 GPa and 2100 K
Giuseppe Dalba, University of Trento, Italy
Diffuse scattering in crystalline materials
Diffraction
spots
Diffusion
spots
Synchrotron light - Springer Verlag
Unexpected diffusion peaks appear in a diffraction pattern of a non perfect
crystalline structures.
Giuseppe Dalba, University of Trento, Italy
Diffuse scattering in amorphous materials
6
1200oC
3
0
3
2
1
0
3
2
1
0
1100oC
S(k) [e.u.]
1000oC
o
2
1
0
3
2
1
0
950 C
2
500oC
800oC
1
0
The structure factors for pure silica gel
samples treated at different temperatures
starting from the as-prepared to 1200oC.
as-prepared
2
1
0
0
2
4
6
8
10
-1
12
14
16
k [Å ]
WAXS measurements can be carried out in short time at various conditions of
temperature and pressure.
Giuseppe Dalba, University of Trento, Italy
X-ray ray micro-tomography
Micro tomogram of iliac crest bone from a female patient undergoing haemodialysis.
The three images are of biopsies taken at three ages, 24, 27 and 32 years. The severe
loss of bone mass is apparent.
The ratios of bone volume to total volume fell from 29.6% to 23.7% between
the ages of 24 and 32
Giuseppe Dalba, University of Trento, Italy
The brilliance versus time
Giuseppe Dalba, University of Trento, Italy
Coronaric angiography
Giuseppe Dalba, University of Trento, Italy
Dual Energy Subtraction
Radiography
-
=
Giuseppe Dalba, University of Trento, Italy
Dual Energy Subtraction with contrast element
103
Mass attenuation coefficient (cm2/g)
Coefficiente di attenuazione
dei raggi X vs Energia
102
K Xe (34.36 K eV)
Xenon
101
1
Ossa
Acqua
10-1
20
40
60
X-ray photon energy (KeV)
Giuseppe Dalba, University of Trento, Italy
80
Giuseppe Dalba, University of Trento, Italy
Coronary Angiography
Giuseppe Dalba, University of Trento, Italy
BRONCHOGRAPHY
Immagine in vivo ottenuta mediante
sottrazione digitale dei polmoni di un
topo mostrante la distribuzione
dell’agente di contrasto, Xenon,
nell’albero bronchiale.
L’obiettivo è di vedere I dettagli morfologici dei bronchi ed il riempimento degli alveoli
Durante il ciclo respiratorio in presenza di xenon nelle vie respiratorie.
Giuseppe Dalba, University of Trento, Italy
Giuseppe Dalba, University of Trento, Italy
The brilliance versus time
Giuseppe Dalba, University of Trento, Italy
Bibliography
Synchrotron light, Springer-Verlag Compact Disk 2000, ISBN 3540148884.
100 anni di Raggi X, 2001, P. Fornasini, Università dgli Studi di Trento
Dipartimento di Fisica, Compact Disk, 2001
http://www.elettra.trieste.it (web site of Italian Synchrotron Light Source,
named ELETTRA, Trieste Italy))
http://www. sesame.htm
http://www.esrf.fr (web site of European Synchrotron Radiation Facility,
Grenoble, France)
http://www.lbl.gov/MicroWorlds/ALSTool/ (web site of theAdvanced Light
Source)
Time Resolved Macromolecular Crystallography, Physics Today, 54 (2001) 33.
Mr. Tompkins in paperback by G. Gamow
J Als-Nielsen, Des McMorrow Elements of modern X-ray Physics Wiley
Giuseppe Dalba, University of Trento, Italy
Trento
Milan
Trieste
Venice
Italy
Florence
Rome
Naples
Sardinia
Cagliari
Palermo
Sicily
Giuseppe Dalba, University of Trento, Italy
Emission from an x-ray tube
Giuseppe Dalba, University of Trento, Italy
Synchrotron light, Springer-Verlag Compact Disk 2000
Giuseppe Dalba, University of Trento, Italy
Synchrotron light, Springer-Verlag Compact Disk 2000
Giuseppe Dalba, University of Trento, Italy
Charged particles in accelerated motion radiate
Storage ring
Giuseppe Dalba, University of Trento, Italy
Bending magnet
Bunch of
relativistic
electrons
N
Light
S
Storage ring
Giuseppe Dalba, University of Trento, Italy
Angular divergence
Electron orbit
e-
Θ ≅ m0c2/E
= 1/γ rad
v≅c
h
Θ ≅ 1/γ rad
The beam collimation is defined as the photon opening angle Θ ≅ 1/γ rad.
For GeV electrons Θ can be smaller than 0.1 m rad. It means that at 100 m from the source
the vertical dimension of the beam, h, is 1 cm.
Horizontally the beam opens as a fan. A very thin sheet of light spreads out from
the orbit on the orbital plane.
Properties
Giuseppe Dalba, University of Trento, Italy
Wiggler
Top view
N
S
N
S
N
S
N
S
K/γ
Side view
N
S
N
S
1/γ
Synchrotron light, Springer-Verlag Compact Disk 2000
S
N
S
N
S
N
Storage ring
Radiation from a wiggler: the horizontal opening is higher than the
vertical one: K is around 20 for a wiggler
Giuseppe Dalba, University of Trento, Italy
Properties
Undulator
S
N
S
N
S
N
S
N
S
N
S
N
S
N
Top view
N
S
N
S
N
S
N
S
1
nγ
Collimation, Why?
Side view
N
S
N
S
1
nγ
S
N
S
N
S
N
Radiation from an undulator: typically N = 50
Giuseppe Dalba, University of Trento, Italy
Storage ring
Properties
An X-ray beam at the ESRF facility
Are X-rays visible?
Giuseppe Dalba, University of Trento, Italy
Properties
(Photons / s ·m rad (0.1% band pass))
Photon flux
Flux of synchrotron light .
1015
1014
1013
λc
1012
105
EC
104
103
102
101
100
10-1
λ (Å)
Infrared Visible Ultraviolet Soft X-ray Hard X-rays
10-1
100
101
102
103
104
Giuseppe Dalba, University of Trento, Italy
105
E (eV)
Spectral distribution of synchrotron light .
Photon flux
1015
1014
1013
λc
1012
105
EC
104
103
102
101
100
10-1
λ (Å)
Infrared Visible Ultraviolet Soft X-ray Hard X-rays
10-1
100
101
λC =
102
103
104
5.6 R 18.6
=
E3
B ⋅ E2
Giuseppe Dalba, University of Trento, Italy
105
E (eV)
?
Spectra
Spectral distribution curves from bending magnets
of some synchrotron light facilities
Properties
Critical energy
ESRF is the European facility located in Grenoble, ELETTRA, the Italian
facility is located in Trieste.
Giuseppe Dalba, University of Trento, Italy
Definition of Brilliance
e-
Ω
Mirror
Focusing device
Image
N (Photons/sec)
Source
A (mm2)
N
Brilliance =
A⋅ Ω


Photons / sec


 mm 2 .(m rad )2 (0.1% ban )


The brilliance represents the largest number of photons per second in a given
band pass that can be focused by a perfect optics onto the unit area at the sample
Spectra
Giuseppe Dalba, University of Trento, Italy
Spectral radiation distribution
Photon /sec/0.1%BW
Undulator
Wiggler
Wiggler
Photon energy
E (hν)
Properties
Giuseppe Dalba, University of Trento, Italy
UHXS Stanford (US)
Giuseppe Dalba, University of Trento, Italy
Giuseppe Dalba, University of Trento, Italy
Brilliance
Properties
Comparison of brilliances between synchrotron and conventional x-ray
sources
Giuseppe Dalba, University of Trento, Italy
The world as seen from the moving
reference frame...
...and from the laboratory
reference frame
v
u
Unbelively shortned
Moving observer
v
Lab observer
v’
u
vx
The relativistic effect on the vertical opening of the light beam
Properties
Giuseppe Dalba, University of Trento, Italy
Insertion devices
Bending magnets
Wigglers
Undulators
Electron bunches, their trajectory and synchrotron radiation in three different
magnetic devices: bending magnets, wigglers, undulators
Storage ring
Giuseppe Dalba, University of Trento, Italy
Why a so wide emission spectrum?
t
Θ = 1/γ
Θ
R
t+Δt
Θ
2Θ
Δt
Fourier relationship: Δt ⋅Δω ≅ 2π
E(t)
Δt ≈ 10−19 sec
t
Δt
⇓
Ι
Δω
Δω ≅ 1019 sec−1
ω
A cosinusoidal wave train modulated by a Gaussian envelope along
with its gaussian transform
Giuseppe Dalba, University of Trento, Italy
?
Low
wavelengths
L
λ0 = L/n
An undulator as seen in the laboratory reference system
Magnetic pole periodicity
n = number of periods
Relativistic contraction
λ’0 = L/nγ = λ0 /γ
The undulator as seen from the electron
Doppler shift
λ = L/2nγ2
Further reduction of the light periodicity due to the Doppler effect
Spectrum
Giuseppe Dalba, University of Trento, Italy
e-
S
N
S
N
S
N
N
S
N
S
N
S
1013
E = 1.5 GeV I = 100 mA
Photon Flux
Wiggler 6 T
R=
Bending
magnet
1012
E (GeV )
B (T )
Ec=k/R
Wiggler 1.85 T
1011
10
102
103
Photon energy (eV)
104
105
ID comparison
By decreasing the curvature radius of the electron trajectory the spectrum
shifts to higher photon energies
Giuseppe Dalba, University of Trento, Italy
e-
e-
S
N
S
N
S
N
N
S
N
S
N
S
Giuseppe Dalba, University of Trento, Italy
Δt
Top view
Electron
orbital
plane
Side view
Θ ≅ 1/γ (≈10−4 mrad)
Synchrotron light is spread on the orbital plane as a very thin sheet
Angular distribution
Giuseppe Dalba, University of Trento, Italy
Photon Flux
1011
3hc γ 3
EC =
4π R
EC
1010
EC
109
Ee (GeV) = 1.5
EC
2.5
4
108
101
102
103
104
Photon Energy (eV)
105
Dependence of the critical photon energy on the electron energy
Giuseppe Dalba, University of Trento, Italy
Polarization
The on-axis synchrotron light is
polarized in the orbital plane
Linear polarization
Orbital plane
Synchrotron light - Springer Verlag
Circularar polarization
The synchrotron light out of the
orbital plane has circular
components with opposite
helicities above and below the
horizontal plane.
Synchrotron light - Springer Verlag
Polarization is exploited for studying magnetic interactions. The difference in
absorption in left and right hand circularly polarised light by a solid can be
directly related to the ferromagnetic magnetization density (circular dichroism).
Properties
Giuseppe Dalba, University of Trento, Italy
Time structure
Light pulses
e- e- e-
e-
I
100 ps
1µs
Time pulsed emission is interesting for studying rapid reactions
Properties
Giuseppe Dalba, University of Trento, Italy
t
Synchrotron-light for Experimental Science and Applications in the Middle East
The SESAME Project aims to establish the Middle East's first major international
research center as a cooperative venture by the scientists of the region
SESAME will have as its centerpiece a
synchrotron radiation source based on a
gift from Germany of the 0.8 GeV BESSY I
storage ring and injector system which
stopped operation at the end of November
1999.
Eleven countries have so far joined the project. These are: Armenia, Cyprus,
Egypt, Greece, Iran, Israel, Jordan, Morocco, Oman, Palestinian Authority, and
Turkey.
The project is being developed under the umbrella of UNESCO and will be located
in Allaan, Jordan (30 km from Amman and 30 km from the King Hussein/Allenby
Bridge crossing of the Jordan River.
Giuseppe Dalba, University of Trento, Italy
Synchrotron light Springer Verlag
Principle of operation of a bending bending magnet
Giuseppe Dalba, University of Trento, Italy
Synchrotron light, Springer-Verlag Compact Disk 2000
Principle of operation of a bending magnet
Giuseppe Dalba, University of Trento, Italy
Kα excitation
e- primario
e-
63Cu
29
e- secondario
n=34
Z=29
K
L
M
N
Cu Kα
Excited system
63Cu
29
n=34
Z=29
K
L
M
N
Disexcitation
Giuseppe Dalba, University of Trento, Italy
Internal γ conversion
e-
γ
69Zn
30
n=39
Z=30
K
L
M
Zn Kα
N
Excited system
69Zn
30
n=39
Z=30
K
18
e2 e-
L
MN
Disexcitation
Giuseppe Dalba, University of Trento, Italy
Internal β conversion
129I
53
→
129Xe
54
+ βe-
n → p+ + e-
β
129I
53
n=76
Z=53
18 e18 e18 e-
K
β
Xe Kα
L
M
N
Sistema eccitato
129Xe
54
n=75
Z=54
K
18
e-
18
e18
L
e-
M
N
Diseccitazione
Giuseppe Dalba, University of Trento, Italy
Core electron capture
26
55Fe
Cattura K
55Mn
25
p+ + e- → n
26
55Fe
n=55
Z=29
K
L
Mn Kα
M
N
Sistema eccitato
55Mn
25
n=30
Z=25
K
L
M
N
Sistema diseccitato
Giuseppe Dalba, University of Trento, Italy