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.