photon applications of accelerators - show and share .test facilities (e.g. scss) ... petrovic et

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  • Photon Applications

    of Accelerators

    Elaine A. Seddon

    16th February 2015

  • Courtesy W. Eberhardt

  • FELs

    examples

    photon output characteristics

    Photon science opportunities

    atoms in intense fields

    mass selected clusters

    reaction dynamics

    nano-crystallography

    single molecule diffraction

    Overview

  • Overview

    The first X-ray FEL LCLS at SLAC

    Golden Gate bridge

    San Francisco Bay

    Pacific Ocean

    San Francisco

    San Jose

    SLAC

  • Status

    April 10th 2009 first lasing at 1.5

    April 14th achieved saturation

    October 1st 2009 LCLS became

    the worlds first operational

    multi-user X-ray free electron

    laser

    From:

    E Trakhtenberg

    G Weimerslage

    Beam quality sufficient to lase at 1.5

    0.75-2 keV X-rays 5-30 mins to change

    Pulses 60-300 fs

    10 fs pulses possible takes 1-3 hrs to set up

    - many parameters to adjust

  • Courtesy H. Braun, PSI

    Worldwide two hard X-ray FELs in operation

  • RIKEN-JASRI Joint-Project for SPring-8 XFEL

    Emax 8 GeV

    0.1 nm

    3.5mm fixed gap

    Period 15 mm

    fs pulse widths

    Peak brilliance

    ~1033

    SACLA & SCSS

    SPring-8

    8GeV XFEL

    Funding April 2006

    FEL Prototype Machine,

    Succeeded in lasing,

    June 2006

    Status

    building construction

    completed March

    2009

    first lasing June 2011

  • LCLS

    SACLA

    FLASH I & II

    FERMI@Elettra

    Operational short wavelength FELs:

    Other examples, under construction or proposed

    e.g. European XFEL first light 2017

    SwissFEL first light 2019

    PAL XFEL Korea, first light 2016

    LCLS II development at SLAC

    test facilities (e.g. SCSS)

    Many examples of long wavelength FELS not included here

    Photons

  • Radiation Sources

    Bending magnet, broad band

    NW x bending magnet

    NU2 x bending

    magnet

    NU2 x Ne x bending magnet

    NU , NW = # magnetic periods

    Ne = # electrons in a bunch

  • Synchrotron radiation vs. FEL radiation

    The difference is in the electron beam quality

    Conventional synchrotron radiation

    Electron brightness

  • Intense pulses

    Extremely high brightness

    >1030 ph/(s mm2 mrad2 0.1% B.P.)

    9 orders of magnitude

    High peak powers

    GWs. High average powers 10kW at JLAB

    Broad wavelength range accessible (THz through to x-ray) and easily tuneable by varying electron energy or undulator parameters.

  • 1013

    Photonen

    109

    Photonen

    FEL

    Undulator (x 10 )

    6

    100 ps

    100 fs

    Photons

    Photons

    time

    Sub 100 fs

    Spontaneous radiation

  • t (fs) Dw/w (%)

    The SASE radiation is powerful, but noisy!

    SASE FEL amplifies random e density modulations

  • Problem with SASE FELs start up from noise means each shot is

    different

    Sometimes you can use this to scan over a range of arrival times

  • 0 1 2 3 4 5 6 7

    0.00

    0.05

    0.10

    0.15

    SASE (no seed) x10

    Seeding

    Insta

    nta

    ne

    ou

    s P

    ow

    er

    (GW

    )

    Time (psec)

    Nature Photonics, 2008

    Seeding at 160 nm: HHG with a conventional laser

  • Pulses transversely coherent without seeding

    Pulses transversely and longitudinally coherent with seeding

    -4

    -3

    -2

    -1

    0

    1

    2

    3

    4

    corrected diffraction pattern

    Slits 0.5 mm apart

    FLASH

    COHERENCE

  • In summary, SR to FEL

    More than a million-fold

    increase in peak brightness

    thousand fold reduction

    in pulse lengths

    coherence

    ph/(s mm2 mrad2 0.1% B.P.)

  • Science Opportunities

    Probing the ultra-small

    Single molecule diffraction

    Imaging nano-crystals

    Imaging live cells

    Sub-cellular imaging

    Capturing the ultra-fast

    Structural dynamics

    Electron dynamics

    Exploring the extremes

    Dilute systems

    Non-linear processes Atoms, molecules, clusters &

    solids in intense fields

    Care!

    Science matched

    to the source

    characteristics

  • Atoms in intense X-ray fields: non-linear XPS

    Optical regime: many photons required for photoemission

    X-ray regime: each photon may carry sufficient energy for ionisation

    Target changes throughout the pulse duration

    Very different from lab- or SR-based XPS

    Removal and rearrangement of electrons on fs timescale within

    a single X-ray pulse

    fundamental physics

    fs structural determinations

  • Ne LCLS ~1018 W cm-2

  • h < 870 eV: valence electrons stripped

    h > 870 eV: inner shell electrons preferentially ejected

    h > 993 eV: hollow neon formed (i.e. no 1s es) if PI rate > Auger decay

    Ne

  • X-ray Transparency

    At 2000 eV photoabsorption decreases if pulse length is reduced

    from 230 fs to 80 fs

    Qualitatively: 1s photoionisation dominant

    When both emitted cross-section drops until

    theyre replaced by valence electrons.

    But

    Auger decay very fast, 2.4 fs, why do we see

    anything?

    Cause: Auger refilling time increases dramatically

    with charge state.

  • Non Linear effects at short

    wavelengths: Xe

    Photon

    Wavelength 13.3 nm

    Energy 93 eV

    Focus 3 m diameter Irradiance level

  • Non Linear effects at short wavelengths: Xe

    TOF mass spectra

    Starting from neutral Xe, Xe21+ requires at least 5 keV

    Implies >57 93 eV photons absorbed in 10 fs

    Theory still being developed

    Photons

    Wavelength 13.3 nm

    Energy 93 eV

    Focus 3 m diameter

    Irradiance level

    7.8x1015 W cm-2

    Richter, et al.

    App. Phys. Lett.,

    92 (2008) 473

  • MPI Xe: LCLS

    Rudek, et al.

    Nature Photonics (2012) 858

    result of resonantly

    enhanced absorption

  • Ultra Dilute Systems

    FLASH: 1013 photons per pulse i.e. in 100 fs it delivers the same as a 3rd generation SR source does in 1 s.

    Experiments in the soft x-ray regime on ultra dilute targets (typically with only a few

    particles in the interaction volume) become possible for the first time.

    e.g. Mass-selected

    clusters

    Highly

    charged ions

    Molecular Ions

  • MASS SELECTED CLUSTERS

    32.8 nm ~38 eV

    27 pulses of approx 20 fs each

    Separated by 10 s at 5Hz rep rate

    MASS SELECTED CLUSTERS PE counts red - with clusters

    blue - background

  • V. Senz and coworkers,

    Phys. Rev. Letters, 102 (2009) 138303

    MASS SELECTED CLUSTERS

  • FEL

    laser

    Variable time delay

    Laser-laser pump-probe

    Single beam split get excellent

    synchronisation

    Limited in probe wavelength

    Laser-FEL pump-probe

    Synchronisation challenging

    Short pulses

    X-rays

    Reaction dynamics

    Structural dynamics

    Time resolved studies

    Not just interested in static information

  • Reaction dynamics: OPXP Optical Pump X-ray Probe

    Optical pulse initiates reaction, X-ray probe monitors change

    by TR X-ray-induced X-ray photoionisation and fragmentation

    Ion fragmentation patterns encode info on instantaneous molecular

    geometry and motion

    1,3 cyclohexadiene

    CHD

    uv pulse initiates ring opening

    Delayed X-ray pulse starts to fragment the molecule

    1,3,5-hexatriene

    HT

    insight into the isomerisation

    Relevant to vitamin D biosynthesis Petrovic et al. PRL 108 (2012 ) 253006

  • Advantages of X-rays:

    Very short X-ray pulses (

  • KER and no. of H+ ion fragments per molecule evolve over 1 ps

    When electrons removed faster than the timescale for nuclear

    motion the Kinetic Energy Release (KER) is a measure of the

    distance between the +ve charges before they start flying apart

    (Coulomb explosion)

    - Reconstruct molecular geometry

    Petrovic et al. PRL 108 (2012 ) 253006

  • Molecular structure

  • Data obtained on the Diamond Light Source

    Protein Structures using SR: Cysteine Protease

    Ribbon diagram:

    Helices

    Beta sheets

    Bradshaw et al. Acta Cryst. D70-7, (2014) 983.

    Twelve data sets

    collected from

    four crystals

    SR structural

    determinations

    crystal size mm

    down to 10s

    microns

    X-rays scatter from the ordered protein molecules, diffraction pattern

    encodes the atomic positions.

  • Pioneering work on Structural Dynamics

    Michael Wulff and coworkers, Science 2003

    Global structural

    changes have already

    occurred on the 100ps

    timescale

    ESRF experimental results

    Why is a FEL needed?

    Have the wavelength required

    - but not the intensity at the

    required time resolution

    Electron densities of CO-myoglobin

    before and after photolysis

    Understanding of