Status, Progress and Outlook
from AMOS Team
Nora Berrah, WMU
1. Team Organization.
2. Scientific Plan.
3. Progress in Experimental Plan to Carry
Out the First Experiment.
4. Future Plan.
AMOP Collaborative Team ( Original Merged LOIs A)
Mariage of Synchrotrons + Ultrafast Communities
Lou DiMauro (OSU) (T. Leader) & Nora Berrah (WMU) (co-T. Leader)
John Bozek (Instrument Scientist)
Pierre Agostini OSU
John Bozek LBL
Roy Clarke UM
Paul Fuoss ANL
Chris Greene U Colorado
Bertold Kraessig ANL
Dan Neumark UC Berkeley
Steve Pratt ANL
John Reading Texas A&M
Steve Southworth ANL
Linda Young ANL
Musahid Ahmed LBL
Philip H. Bucksbauom UM
Todd Ditmire UT Austin
Ernie Glover LBL
Elliot Kantor ANL
Steve Leone UC Berkeley
Gerhard Paulus Texas A&M
Alexei Sokolov Texas A&M
David Reis UM
Linn Van Woerkom OSU
~ Twenty Additional Scientists Expressed Interest at
the October 2004 Workshop
Update on AMOS Activities/
Organization
1.
2.
3.
4.
5.
Instrument Scientist on Board (Jan 2006)
Weekly Teleconf (DiMauro, Bozek, Young, Bucksbaum, Berrah)
N. Berrah on Sabbatical FY06
Periodic visits by L. DiMauro
Communication with Broader Team at Conferences
(Wisconsin W. 8/04; DOE M. 9/05; DAMOP 5/06)
6.
E-mail Updates to Broader Team when Necessary
(seek input, communicate news)
Discussions/communication led to determine the
instrumentation needs for first experiments!
7.
Conceptual Design and Instrument Budget
was submitted and Accepted by LCLS.
Outlook on AMOS Activities/
Organization (Cont..)
8.
Synergy between the PULSE Center and AMOS
9.
Workshop to Stimulate Theory (ITAMP 06-06)
10. Met with:
-----LCLS Optics Group
------Pump-Probe Team to Explore Common
Interest and will Continue to Meet.
11. Plan to Meet with Imaging Group to Explore Shared
Experimental System?
12. Organize LCLS/PULSE Summer School June 2007
AMOS Major Scientific Thrusts:
•X-Ray Strong Field Physics
•Dynamics at the AtomicScale
• Fundamental Atomic and
Chemical Physics
Status of Broad Scientific Plan
1. High Field Studies in Atomic, Molecular,
Cluster, Ion and Biological Systems.
-- Apply x-ray nonlinear processes to characterize the
LCLS x-ray pulse
2. Time-resolved Studies of Molecules and
Clusters
3. Scattering Experiments of Molecules and
Clusters
Initial Scientific Goals (First 2 Years)
1. High Field Studies in Atoms (Ne) in
Molecules (HBr) and in van der Waals
Clusters and C60.
2. Two-Color Auger Sideband Experiment
(initial timing diagnostic)
3. High Field Studies in Ions(Ne8+,Fe+, C60+/-, S-)
4. Scattering Experiment on Laser Aligned
Molecules
Introduction/Background
• Although the Weak Field Regime with Synchrotrons
Provides Inner-Shell Photoionization Baseline
Data for Atoms, Molecules, Clusters and their ions
And
• Laser High Field Research is Better Understood
AMO Research with LCLS is a New Ball
Game!
Because
• The LCLS beam intensity (1013 x-rays/200 fs) is greater
than the current 3rd generation sources (104 x-rays/100
ps).
• Extreme focusing leads to intensity ~1035 photons/s/cm2
(~ 1020 W/cm2 for 800 eV x- rays)
• Nonlinear and strong-field effects are expected when the
LCLS beam is focused to a spot diameter of 1μm.
• BUT, electron’s ponderomotive (quiver motion) important
at low frequencies IS negligible in the x-ray regime (λ2).
Low-Frequency Physics → High Frequency
IR:
Low frequency regime
VUV FEL:
Intense photon source
XFEL FEL:
Highly ionizing source
- Ip
- Ip
1015 W/cm2
• Keldysh parameter  <<1
• Tunnel / over the barrier
ionisation
• Ponderomotive energy 10
– 100 eV

- Ip
10x20 W/cm2
1013 W/cm2
• Keldysh parameter  >>1
• Multi-photon ionisation
• Ponderomotive energy
10 meV
Optical Frequency
Tunneling Frequency
• Angstrom wavelength
• Direct multiphoton ionisation
• Secondary processes
= (Ip/2Up)1/2 -1;
Up=I/4ω2 (au)
LCLS Beam will Allow Investigation of:
• Multi-photon excitation/ionization → Highly excited
states of matter; Multiple ionization sufficiently rapid
to form hollow atoms; Multiply-charged targets;
allows absorption below the edge
• Collective tunneling effects?
• Rescattering of ionized electrons with the targets?
• Certainly new and unexpected phenomena!!
How Would LCLS High Field Affect:
1. Auger Processes Subsequent to Inner-Shell
Photoionization of Gas-Phase Matter? Nonlinear effects,
Multiple core hole formation (Ne, S-)
2.
Inner-Shell Resonances (excitation to Rydberg state,
doubly or triply excited states)? (Ar, CO, HBr)
3. Threshold Effects? PCI (Ar) Electron Recapture? (Li-)
4. Fragmentation dynamics? (OCS, Van der Waals
Clusters)
LCLS High Field Beam will Favor NonSequential Auger Decay
Auger Decay
Photodetachment
(or Ionization)
Auger Decay
Sequential
(or “Cascade”)
Multi-Auger
Decay
Simultaneous
Double-Auger Decay
( 3-10% of single Auger)
Double K Vacancy in Gas-Phase
Systems: Possible Consequences
• The decay of the KK-vacancy state will
produce higher charge states
• This process → extensive fragmentation in
molecules
• This process → damage consideration in
experiments on Bio-molecules?
High Field Studies in Atoms
FLASH Experiment
PRL 94, 023001 (2005)
Theory Available! Calculate the rate of production of highly
charged Xei+ ions produced by direct multiphoton absorption, to
compare with experiment.
TOF Spectrum for Atomic Xenon Multiphoton Ionization
(Wabnitz et al.’05 )
Wabnitz et al. ‘05
First LCLS Experiment: K-Shell in Ne
1. Photoionization
2. Auger Decay
3. Sequential Multiphoton Ionization
4. Direct Multiphoton Ionization
Theory:
LCLS
Double-K ionization in Ne due to
absorption of 2-photons by 1 atom for
hγ>932 eV is predicted to be 100%
The probability of twophoton absorption by 1s2 shell accompanied by the
creation of double 1svacancies predominates
over the probability of the
process of two-photon oneelectron excitation/ionization
of the 1s2 shell in the range
of x-ray photon energies ≥
930 eV.
2 e-out
1e-out
Inner-Shell
Resonances in Ar;
2 p Excitation to
Rydberg States(ALS)
LCLS: K-Shell Ar
How would the ratio
of Doubly Ionized
Ions (Auger decay)
Compares to Singly
Ionized Ions due to
spectator Auger
decay?
Resonant shake-off of two electrons.
High Field Studies in Molecules
Molecular Fragmentation: Ion Momentum
Imaging of Molecules (ALS)
Resonant Auger Electron
Spectroscopy
• Interesting in molecules too – CO resonant
Auger:
Probe Auger(2+)/Spectator Auger
(1+) Decay & Fragmentation Pathways
Spectator Auger
HBr 3d (ALS)
Excitation/Ionization
2D Map; AngleResolved;e- TOFs
LCLS: HBr
2p & 2s
Ionization
High Field Studies in Clusters
Cluster Studies at FLASH in Hamburg
Cluster Studies, FLASH
Xenon Cluster size 2500 atoms
PFEL=2.5*10
6
7
W/cm
13
2
8
Tpuls=50 fs
FEL=98 nm
Intensity (arb. units)
3
4
5
6*10
Xe
12
2+
6*10
11
8*10
Xe
400
600
 Fragmentation starting at
1011 W/cm2
10
+
2*10
200
 Unusually high energy
absorption in cluster
800
Time of flight (ns)
10
Wabnitz et al, Nature 420, 482 (2002)
Coulomb explosions change at short wavelengths
Source:
Wabnitz et al,
Nature, Dec 2002
Molecular dynamics simulations indicate
that standard collisional heating cannot
fully account for the strong energy
absorption.
LCLS: Ion, e-, and Scattering
Experiments on Clusters
• Study the Dynamics of Cluster Explosion as a
Function of Cluster Size, Wavelengths, Intensity:
Is it a Coulomb Explosion Picture (as in intense
optical or near IR ultrafast laser pulses) OR
Explosion due to Hot Nanoplasma (multiple
scattering from the cluster atoms can confine electrons yielding a
nanoplasma); Explosion Time can be Different
OR, New mechanisms??
• Will Collective Electron Effects be important as in
the dynamics of IR irradiated large clusters?
Two Dimensional Map of Xe Clusters for 4d Ionization
(ALS)
Size Effect Revealed via Angle-Resolved
Study of Xe Clusters (ALS)
___ Atomic data
High Field Studies in Ions
High Charge State Formation Following 2p
Photodetachment of S- (ALS)
S2+/S+ 60%
Li3+/Li2+<1%
Th, Sim-Auger
Int, K-Out
H, S-Off; or
S-Up+Seq-Aug
Where will the Action Take
Place?
AMO “home”?
• Instrument
Layout Primarily
on Side-Branch
AMO Instrument - Layout
• Use APS style tables with multiple axes of motion
AMO Instrument - Layout
• Instrument control issues:
– Many stepper motors (50-100) to align
chambers, position detectors, etc
– High voltage (dozens) controlled through 010V analog signals (and similarly monitored)
– Valves & pumps etc for vacuum system
– Valves & pumps for gas handling system
– Hoping whole control system architecture can
live in hutch (no long cable pulls)
How do We Plan to Carry Out
the First Experiments?
Two Classes of Experiments
1. Kinematic Complete Characterization
(e-, Ion, Photon);
--- High/low resolution instrumentations
Multiple e- and Ions Imaging Detectors (5 eTOFs, COLTRIMs, Fluorescence Detectors).
----Dilute species/single shot measurements
2. Photon-In/Photon-Out (Diffraction)
High Field Experiments:
Fluorescence Spectrometers
– Probe entirely different electronic channels
than those available to electronic transitions
– Much less sensitive to space-charge
broadening
Schematic of the High-Field Experimental System
Being made by John
High Field Experiments: e--Ions
Detection
– Use 5 e- time-of-flight spectrometers to
measure energy and angular
distributions of electrons
• Choose geometry to obtain appropriate
information
• KE of electron will reveal multi-photon
absorption
• Signature of multiple photon
excitation/ionization – usual selection
rules broken
– Different l-values accessible (instead of Δl
= +1, -1 get
Δ l = -2, 0, +2) – i.e. s-to-s and s-to-d
transitions accessible
– Dipole angular distributions (i.e. β = -1, 0,
2)
Details: AMOS Three type of
Detectors
•
2D X-ray detector to be used for
small-angle elastic scattering (same
as Imaging Group).
. Electron detectors, 5 time-of-Flights,
50 ps time resolution, 50 mm
diameter, 120 Hz readout time
Electron energy & angular distributions
Detail; Ion Detectors (continued…)
•
Ion detector for momentum
measurement, Energy resolution: better
than 5µeV (with a supersonic beam.
Spatial resolution: better than 50µm (we
expect 20µm). Temporal resolution: better
than 100ps (we expect 50 ps). Detector
area: 80 mm or 120 mm diameter, multihit
capability: 3 events / 50 nsec (30 events /
50 nsec in future)
LCLS AMO Project Timeline
• Design begins June 2006
– completed August 2007
• Purchasing initiated in FY07
• Assembly & testing in FY08
– Staggered: diagnostics, high field experiment, refocus
optics, single particle diffraction
• Comissioning begins Nov 2008
– Full operation by project completion Mar. 2009
Beyond the First Experiments
1. Probing metal clusters photoionization-produced charge states, as a
function of time, photon energy, intensity, cluster size.
2. Probing inner-shell relaxation in real time, in an atom or a simple
molecule; Study timescale of the fragmentation via pump-probe
techniques
3. Chirped multiphoton excitation to excite an entire atomic shell to a
higher shell, in a single pulse (Ultimate Goal: Precise Control and
Charaterization of X-Ray Fields).
Advantages of AMO for Single
Particle Imaging/Diffraction
• Structure of size-selected clusters (when
combined with ion beamline to create
monodisperse beam)
• Dynamic imaging of dissociating
molecules, exploding clusters, etc
Cost of detectors encourages purpose
built chamber to be shared??
Further Equipments needs
• Lower photon energies beamline (C
edge)
• Monochromator for low hv (below 800
eV)
• Laser ablation system to generate metal
clusters
• Ion source (ECR/EBIT?)
• He cryostat for cluster source (including
metal clusters).
• Streak camera
R&D Needs
• KB focusing pair (submicron spot size, for soft x-rays)
• Imaging of fast (keV) electrons
• High readout rate detectors.
• Improved Synchronization between laser and LCLS
pulse (pump-probe)
• Non-collinear/collinear X-ray delay line
• X- ray Interferometers development (3-10)
• Support to Theorists for modeling and predictions
END