First user experiments at the VUV-FEL
Josef Feldhaus, DESY
MAC meeting November 9, 2004
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.
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)
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
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
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
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
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
Cluster size dependence
2·1013 W/cm2
• 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
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
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
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”
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
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+
estim
ated
CHn+
H2O+
H3O+
NHn+
Relevant Photon Energies:• Interstellar clouds: < 13.6 eV• Close to stars: < 50 eV
VUV-FEL
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
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
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.