Atomic, Molecular and Optical Science

AMO OverviewIntense 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

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 re-

actions on their natural time scales using well established and powerful

tools such as ion, photoelectron, Auger and X-ray emission spectroscopy.

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.

AMOL I N A C C O H E R E N T L I G H T S O U R C E

Main Contacts:

Name John Bozek� Instrument ScientistPhone 650-926-5091Email jdbozek@slac.stanford.edu

Name Christoph Bostedt AMO Instrument ScientistPhone 650-926-2591Email bostedt@slac.stanford.edu

Name Jerry Hastings LUSI Project DirectorPhone 650-926-3107Email jbh@slac.stanford.edu

AMO Complete Assembly

AMO at the LCLS

LCLSComplex

AMO/Near Hall/Hutch 1

Scienti�c Application

Techniques

Sample Environment

Focusing Capability

Beam Size at Sample

Energy Range

Energy Resolution ΔE/E

Magnetic BottleElectron Spectrometer

Pulse Energy Monitor

Beam Screens

Atomic, molecular and optical science with ultrafastand ultraintense x-rays at the lcls

Scienti�c Capabilities

Photon Beam Properties

Diagnostics

Electron time-of-�ight spectroscopy

Ion time-of-�ight spectroscopy

Ion imaging

Ion momentum spectroscopy

X-ray emission spectroscopy

Skimmed supersonic pulsed gas jet

Elliptically bent Kirkpatrick-Baez mirrors

~1-2 μm at interaction region

825-2000 eV

~0.2% (inhomogeneous fel bandwidth)

(no monochromator)

Measures the photon energy and bandwidth of the X-rayswith a high e�ciency electron spectrometer

Measures the energy of each pulse

Measures position and size of beam in the far �eld

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

AMO Science FocusThe interaction of ionizing radiation with matter has been a topic of much study

since Hertz observed (1887) and Einstein described (1905) the photoelectric ef-

fect. While the mechanisms of excitation and ionization following the illumina-

tion 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 mat-

ter 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 pro-

duced 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

scale that the LCLS is ideally suited to study, and the electronic structure of a

molecule adjusts to the changing nuclear structure. Furthermore, photoion-

ization of inner-shell electrons provide a site-specific probe of the electronic

structure of a molecule, i.e. allowing electrons from a carbon atom to be dif-

ferentiated from those of an oxygen atom. The LCLS is therefore a powerful tool

for studying the motion of atoms in molecules reactions initiated by an external

trigger (i.e. laser).

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

The AMO instrument is separated into four vacuum chambers, each with their own specific purpose:

• Single Pulse Shutter

• Focusing Optics

• High-field Physics End-station

• Diagnostics Chamber

In addition, a ~2mJ 120Hz 800nm pulsed laser (with harmonics) will be provided along with a control and data acquisition system ca-pable 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

P

P

Gas Jet

Up

to A

ir Va

lve

BypassValve

Di�erentialPumping

LaserIntroduction

Mirror

BeamFocus

Paddle

ElectronSpectrometers 5x

Telescopeand Camera

X-ray EmissionSpectrometers

1 of 3Ion Spectrometers

High-�eld Physics End-station

Turbo

RemoveableBeam Stop

BeamViewingPaddle

PP

P

PrimaryPump Sample P

PrimaryPump

TurboRG

A

Slow SpeedCamera

Slow SpeedCamera

P

P

IonPump

Single Pulse Shutterwith Beam Paddle

Single Pulse Shutter

Slow SpeedCamera

P P

P

IonPump

PrimaryPump

Turb

o

TSP

KB Mirror 1 and 2

Focusing Optics

Scanning Slits (2)with YAG Paddle

Slow SpeedCamera

Magnetic BottleElectron Spectrometer

X-ray EmissionSpectrometers

GasNeedle

Diagnostics Chamber

P P P

P

P

PrimaryPump

Turb

o

Turb

o

Sample

Di�erentialPumping

P

PrimaryPump

Turbo

RGA

Up

to A

ir Va

lve

Up toAir Valve

BeamViewingScreen

120 HzCameras

FixedBeamStop

Slow SpeedCamera

BeamViewingScreenTotal

PowerMeasurement

AMO CompleteAssembly

1

1

3

4

22

3

4

AMO Assembly Breakdown

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 millisec-

ond 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 experi-

mental chamber. Dynamically bent mirrors can be adjusted to focus the beam

into either the interaction region in the high-field physics chamber or the diag-

nostics chamber, depending upon the experimental requirements.

High-field Physics End-station:The main experimental chamber of the AMO instrumentation includes the ma-

jority of the experimental capabilities. A skimmed pulsed gas jet is used to intro-

duce 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 in-

teraction region to measure the energy and direction of the ejection of electrons

from the sample. One of three possible ion spectrometers, either a simple time-

of-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.

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 spectrom-

eter 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 inter-

pretation of the data obtained in the upstream chamber.

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