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First user experiments at the VUV-FEL
Josef Feldhaus, DESY
MAC meeting November 9, 2004
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Layout of the Experimental Area
Klimaschrank
Opticallaser
BL310 µm
BL220 µm
BL1100 µm
PG2PG1
High resol. PGMmonochromatorIntensity and position
monitor (gas ionization)~42m to undulator
Uni HH (BMBF)
MBI and EU coll.
Coll. with PTB, Ioffe Inst.
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The First User Experiments
technicaldevelopments
atomsions
clusters
solidssurfaces
plasmas biological samples
0
2
4
6
8
10
12
Num
ber o
f VUV
-FEL
pro
ject
s
.
all
2005VUV-FEL Proposals in Sept. 2002
30 proposals submitted200 scientists involved
60 institutes11 countries
Available beam time heavily overbooked (98 weeks requested for the first year)
Areas of research
• Many groups have formed collaborations• Many groups have built new instrumentation• Substantial funding has been allocated for these
experiments (e.g. 14 groups funded by BMBF)
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User experimentsAreas of Proposed Research
• Interaction of ultra-intense XUV pulses with matter- FEL wavefront measurement and correction, sub-µm
focusing- multiphoton excitation of atoms and molecules- plasma physics
• Femtosecond time-resolved experiments- synchronisation FEL - optical laser- chemical reactions on surfaces - magnetism dynamics
• Investigation of extremely dilute samples- free radicals- monomeric clusters- highly charged ions
• High-resolution spectroscopy- nanometer focus- meV-resolution photon and photoelectron spectroscopy
of surfaces and solids
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Au film (15 nm) on Si substrate irradiated by a single FEL pulse
λ = 98 nm, W=100 TW/cm2
TTF1 results
R. Sobierajski et al., Pol. Acad. Sciences, DESY, GKSS
Damage of C coatings
SEM
AFM
⇒ Plasma physics
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Plasma Experiments: Extremely Hot Matter at Solid Densities
FEL-Beamλ = 40 nmI = 1016 W/cm²
100fs
Al-Target
Pressure in an atomic nucleus
A. Krenz, Diploma Thesis, MPI Garching
Collaboration of 12 groups
First simple experiment
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z=40m
Reflectivity Mirrors for FEL radiation
time
Temperature of the mirror surface
100
80
60
40
20
0
Ene
rgy
per a
tom
at 4
0 m
(meV
)
30025020015010050
Photon energy (eV)
z = 0x 0.01
3°
θ = 90°
2°
Au2°
Ni2°
1°
Typical damage threshold for coatings: ~50 mJ/cm2
experimental result from TTF1
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0 100 200 300 400 500 600 700 8000,0
0,2
0,4
g
average size of clustersN=300
7+6+
8+
5+
4+
Xe++
Xe3+
Xe+
inte
nsity
[arb
. uni
ts]
time of flight [ns]
IpXe = 12.1 eV
Ephot= 12.8 eV
Coulomb explosion of Xenon clusters with ~ 300 atoms
1013 photons in ~50 fsec
in a 20 µm spot
H. Wabnitz et al., Nature 420, 482 (2002)
TTF1 results
Single shot time-of-flight spectrum
Cluster physics
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Cluster size dependence
2·1013 W/cm2
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• Multi-Photon Processes in Atoms & Molecules
• Interactions with Molecular Ions
• Excitation of Highly-Charged Ions
Atomic Physics
Universität Frankfurt: R. Dörner, L. Schmidt, Th. WeberFritz-Haber Institut Berlin: U. BeckerUniversität Hamburg: B. SonntagMax-Planck-Institut Heidelberg: R. Moshammer, A. Dorn, D. Fischer,
C.D. Schröter, J. Ullrich
Max-Planck-Institut Heidelberg: H.B. Pederson, A. Wolf, D. Schwalm, J. Ullrich
Weizmann Institute Rehovot: D. Zajfmann
Max-Planck-Institut Heidelberg: J.R. Crespo, J. Braun, J. Bruhns, A. Dorn,R. Moshammer, C.D. Schröter, J. Ullrich
Fudan University Shanghai Y. ZouLLNL Livermore P. Beiersdorfer
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Multi-Photon Multi-Electron Processes in Atoms & Molecules
Project leader: J. Ullrich, MPI Heidelberg; with Univ. Frankfurt, Fritz-Haber Institut Berlin, Univ. Hamburg
Spectrometer:ion-electron coincidenceµeV resolution for ionsmeV for electrons
Reaction-Microscope
supersonic gas jetatoms, molecules
FELFEL
drift
Detectorposition-sensitivemulti-hit
Helmholtz coil
E-field
• ultra high vacuum: p < 10-11 mbar• cold target : T < 1 Kelvin• multi-hit detectors: ∅ = 12 cm, ∆t ~ 10 ns
ion detector
gas jet
electron det.
FEL
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Photo-Ionisation1 photon
Multi-Photon10 photons
Ee Ee Ee
ε ε
I ≈ 1012 W/cm2 I ≈ 1015 W/cm2
single active electron => single ionisation
Well und
erstood !!
Well und
erstood !!
But: Absorption of 2,3.. photons ??
Tunnel-Ionisation>15 photons
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two active electrons => double ionisation
Dörner et al. (2001)
ε
P|| /a.u.
-10 -5 100 5
ε
1 photon 50-100 photons
! not unde
rstood
! not unde
rstood
! understo
od! und
erstood
2 photons
“FEL”
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Photo-Dissociation of Molecular IonsProject leader: A. Wolf, Max-Planck-Institut Heidelberg, coll. with Weizmann Institute Rehovot
Ener
gy
R
Direct Predissociation Spontaneousradiative diss.
• photo-dissociation rates• branching ratios
Application: Interstellar cloud chemistry
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from Hartquist, Williams Cambridge Univ. Pr. 1995
H2 H2+ H3+
CO
HCO+
e-
Chν
e-H2
Interstellar cloud chemistryExample: CH+ (production of oxygen-bearing molecules)
loss mechanism
photo-dissociation
CO
Example: Diffuse Cloud (ξ Ophiuchi)NObser(CH+) = 2.9·1013 cm-2NModel(CH+) = 2.8·1010 cm-2
CH+
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estim
ated
CHn+
H2O+
H3O+
NHn+
Relevant Photon Energies:• Interstellar clouds: < 13.6 eV• Close to stars: < 50 eV
VUV-FEL
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Photo-dissociation experiment behind the PGM
Hollow cathode ion source 5 kV
Electrostatic ion beam trap
Einzel lens
• Kinetic energy release• Angular distributions• Cross sections
Cold molecular ion beam~ 50 ns pulserelax. time (CH+) ~ 0.4 sec
VUV FEL Photodissociation imaging
Molecular ionse.g. CH+, CH2+, HeH+
Otherexperiment monochromatic
FEL beam
5 m
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Ultra-High Resolution Photoelectron Spectroscopy
• ∆Ekin ~ meV• spatial resolution ~10 nm• high angle resolution
Project leader: L. Kipp, Universität Kiel
Photon sieve
Electronic structure of highly correlated materials
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Conclusions
• 30 high-quality projects have been approved, ~12 experimental systems are ready and wait for beam.
• The demand for beamtime is very high ⇒- maximise user beamtime;- make maximum use of the FEL beam.
• It is extremely important that the user experiments are successful; they must drive future developments and justify future funding.