Download Atomic, Molecular and Optical Science

LINAC COHERENT LIGHT SOURCE
Atomic, Molecular and
Optical Science
AMO Overview
Intense short pulses of X-ray radiation created by the LCLS free electron
laser (FEL) will interact with electrons in the sample being illuminated to
create states of matter that have not been observed previously. The goal
AMO
Main Contacts:
Name
Phone
Email
John Bozek
Instrument Scientist
650-926-5091
[email protected]
Name
Phone
Email
Christoph Bostedt
AMO Instrument Scientist
650-926-2591
[email protected]
Name
Phone
Email
Jerry Hastings
LUSI Project Director
650-926-3107
[email protected]
of the Atomic, Molecular and Optical (AMO) science instrumentation at the
LCLS is to explore the interaction of this intense radiation with the simplest
forms of matter, namely atoms and molecules, to gain an understanding of
how their electronic structure responds. Femtosecond X-ray pulses from
the LCLS also offer the opportunity to follow the evolution of chemical reactions on their natural time scales using well established and powerful
tools such as ion, photoelectron, Auger and X-ray emission spectroscopy.
AMO at the LCLS
LCLS
Complex
A suite of instrumentation including focusing optics, gas delivery systems,
electron, ion and photon spectrometers and a synchronized high-power
laser are currently being designed for the AMO end-station.
AMO Complete Assembly
AMO/Near Hall/Hutch 1
AT O M I C , M O L E C U L A R A N D O P T I C A L S C I E N C E
AMO Characteristics
Scientific Capabilities
Scientific Application
Atomic, molecular and optical science with ultrafast
and ultraintense x-rays at the lcls
Techniques
Electron time-of-flight spectroscopy
Ion time-of-flight spectroscopy
Ion imaging
Ion momentum spectroscopy
X-ray emission spectroscopy
Sample Environment
Skimmed supersonic pulsed gas jet
Photon Beam Properties
Focusing Capability
Elliptically bent Kirkpatrick-Baez mirrors
Beam Size at Sample
~1-2 μm at interaction region
Energy Range
825-2000 eV
Energy Resolution ΔE/E
~0.2% (inhomogeneous fel bandwidth)
(no monochromator)
Diagnostics
Magnetic Bottle
Electron Spectrometer
Measures the photon energy and bandwidth of the X-rays
with a high efficiency electron spectrometer
Pulse Energy Monitor
Measures the energy of each pulse
Beam Screens
Measures position and size of beam in the far field
AMO Science Focus
The interaction of ionizing radiation with matter has been a topic of much study
since Hertz observed (1887) and Einstein described (1905) the photoelectric effect. While the mechanisms of excitation and ionization following the illumination of a sample with a weak beam of X-rays are well understood, little is known
about the processes which occur when an intense beam of X-ray radiation strikes
a target. Novel multi-electron processes are expected to occur and states of matter never before seen created. The goal of the AMO instrument is to study the
interaction of the intense, short pulses of X-rays from the LCLS with the simplest
forms of matter; atoms, molecules and clusters, to expand the understanding of
which processes are important at different intensity regimes.
The extremely short pulses of X-rays from the LCLS provide a unique capability
to study chemical processes at their natural time-scale. X-rays, such as those produced by the LCLS, interact with electrons in matter, exciting or ionizing them or
scattering from them. Electron dynamics occur on the attosecond time-scale,
much faster than the duration of the LCLS pulse. Nuclear dynamics (the motion
of nuclei in a molecule) occur on the femtosecond time scales, however, a time
The unique capabilities of the LCLS
AMO instrument will address a
wide variety of science such as:
• Investigate Multiphoton and High-field X-ray Processes in Atoms, Molecules and Clusters
•
Multi-photon Ionization/
Excitation in Atoms/Molecules/
Clusters
•
Accessible Intensity on Verge
of High-field Regime
•
Study Time-resolved
Phenomena in Atoms,
Molecules and Clusters Using Ultrafast X-rays
•
Inner-shell Side Band
Experiments
•
Photoionization of
Aligned Molecules
•
Temporal Evolution of
State-prepared Systems
molecule adjusts to the changing nuclear structure. Furthermore, photoion-
The AMO instrument is separated
into four vacuum chambers, each
with their own specific purpose:
ization of inner-shell electrons provide a site-specific probe of the electronic
• Single Pulse Shutter
structure of a molecule, i.e. allowing electrons from a carbon atom to be dif-
• Focusing Optics
ferentiated from those of an oxygen atom. The LCLS is therefore a powerful tool
• High-field Physics
End-station
scale that the LCLS is ideally suited to study, and the electronic structure of a
for studying the motion of atoms in molecules reactions initiated by an external
trigger (i.e. laser).
• Diagnostics Chamber
In addition, a ~2mJ 120Hz 800nm
pulsed laser (with harmonics) will
be provided along with a control
and data acquisition system capable of measuring data from each
pulse.
AT O M I C , M O L E C U L A R A N D O P T I C A L S C I E N C E
AMO Assembly Breakdown
Single Pulse Shutter
Focusing Optics
Slow Speed
Camera
P
Slow Speed
Camera
P
AMO Complete
Assembly
P
KB Mirror 1 and 2
Scanning Slits (2)
with YAG Paddle
Turbo
Single Pulse Shutter
with Beam Paddle
Ion
Pump
1
Ion
Pump
TSP
P
Primary
Pump
1
2
2
High-field Physics End-station
P
Electron
Spectrometers 5x
X-ray Emission
Spectrometers
Slow Speed
Camera
Laser
Introduction
Mirror
Turbo
Gas Jet
P
Telescope
and Camera
Bypass
Valve
P
P
P
Primary
Pump
3
4
RGA
1 of 3
Ion Spectrometers
Differential
Pumping
Up to Air Valve
P
Slow Speed
Camera
3
Beam
Focus
Paddle
Removeable
Beam Stop
Turbo
Beam
Viewing
Paddle
P
Sample
Primary
Pump
Diagnostics Chamber
P
Primary
Pump
4
X-ray Emission
Spectrometers
P
P
120 Hz
Cameras
Gas
Needle
P
Fixed
Beam
Stop
RGA
Up to
Air Valve
Up to Air Valve
Differential
Pumping
Magnetic Bottle
Electron Spectrometer
Turbo
Turbo
P
Slow Speed
Camera
Turbo
Beam
Beam
Viewing
Viewing
Screen Total Screen
Power
Measurement
P
Sample
Primary
Pump
AT O M I C , M O L E C U L A R A N D O P T I C A L S C I E N C E
Single Pulse Shutter:
The first small chamber will house a single pulse shutter that can be used to allow
only a single FEL pulse pass through to the experimental chambers. A millisecond shutter from azsol GmbH (http://www.azsol.ch/index.php?p=home&lg=en)
will be incorporated into the vacuum chamber on a translation stage to allow
insertion into the beam.
Focusing Optics:
Two elliptically bent mirrors will be used to image the FEL beam into the experimental chamber. Dynamically bent mirrors can be adjusted to focus the beam
into either the interaction region in the high-field physics chamber or the diagnostics chamber, depending upon the experimental requirements.
High-field Physics End-station:
The main experimental chamber of the AMO instrumentation includes the majority of the experimental capabilities. A skimmed pulsed gas jet is used to introduce sample gas into the chamber where it will be ionized/excited by X-rays from
the LCLS. Several spectrometers will detect the results of the interaction of the
FEL radiation with the sample, including electron, ion and X-ray spectrometers.
A set of five electron time-of-flight spectrometers will be arrayed around the interaction region to measure the energy and direction of the ejection of electrons
from the sample. One of three possible ion spectrometers, either a simple timeof-flight, a velocity map imaging, or a momentum resolving ion spectrometer,
will also be mounted simulataneously, providing a means of measuring both
ions and electrons from each shot. Eventually two X-ray spectrometers will be
available to measure fluorescence from the samples, although they will have to
be fit in place of the electron spectrometers when in use.
AT O M I C , M O L E C U L A R A N D O P T I C A L S C I E N C E
Diagnostics Chamber:
A separate diagnostics section is being designed to measure the parameters of
the X-ray FEL on a pulse-by-pulse basis. A magnetic bottle electron spectrometer will be used to measure the photon energy and bandwidth of each pulse.
Ce:YAG beam screens will be used to image the beam downstream of the focus
and a thermal energy monitor used to monitor the intensity of each pulse. These
tools are designed to provide information about each pulse to aid in the interpretation of the data obtained in the upstream chamber.