# Presentation: 949435

## Femtosecond X-ray Science:

***Plans for beamline 6.0***

## Outline

-  structural dynamics in condensed matter on femtosecond time scale

- Generation of femtosecond x-rays at the Advanced Light Source

-  technique: femtosecond manipulation of electron beam

-  results from proof-of-principle experiments

- New Science

- Femtosecond Undulator Beamline

-  development plans

-  solid-state physics, chemistry, biology

-  technical issues

-  beamline, insertion device, laser, accelerator modifications

## Femtosecond X-ray Science at the ALS

- fundamental time scale for atomic motion
- vibrational period: Tvib ~ 100 fs

**Structural Dynamics in Condensed Matter**

-  ultrafast chemical reactions

-  ultrafast phase transitions

-  surface dynamics

-  ultrafast biological processes

- Rapidly emerging filed of research
- Physics, Chemistry and Biology

**Femtosecond X-ray Science at the ALS**

## Femtosecond Undulator Beamline

**Ultrafast X-ray Science Facility**

-   solid-state physics
-        - phase transitions
-        - warm condensed matter
-        (R. Falcone, J. Wark, R. Lee, Schoenlein/Shank)

-   atomic and molecular physics
-        - low-field  (N. Berrah, S. Pratt, J. Bozek, J. Hepburn)
-        - high field (T. Glover, A. Belkacem)

**Scientific Program**

-   ultrafast chemistry
- (M. Chergui, C. Bressler, J. McCusker, Schoenlein/Shank)

## h

- h

- high-spin state

- charge-transfer state

- low-spin state

- ~700 fs

- reaction coordinate

- energy

- h

- reactant

- photo-product

**Ultrafast Chemical Reactions**

- Structural Dynamics of the Transition State

-  structural dynamics –
-                spin crossover and e- transfer

-  biochemical processes (cytochrome P450)

-  magnetic and optical storage material

- 1MLCT

- 5T2

## Ultrafast Chemical Reactions - Solvent Dependence

- Ru – charge-transfer complex [Ru(bpy)3]2+

- Femtosecond Polarization Anisotropy Measurements (visible)

- Yeh, Shank, and McCusker, *Science*, **289** (2000)

*Femtosecond dynamics of excited-state evolution in [Ru(bpy)3]**2+*
- Damrauer, Cerullo, Yeh, Boussie, Shank, and McCusker, *Science*, **275**, 54, (1997).

## Capturing a Photoexcited Molecular Structure

**Capturing a Photoexcited Molecular Structure**
**through Time-Domain X-ray Absorption Fine Structure**
- Ni-TTP-L2 (nickel tetraphenylporphyrin)
- Lin X. Chen et al., *Science*, **292**, 2001
*Advanced Photon Source, Argonne National Laboratory*

## Transient XANES and EXAFS Spectra

- Ni-TTP-L2 (nickel tetraphenylporphyrin)
- Lin X. Chen et al., *Science*, **292**, 2001
*Advanced Photon Source, Argonne National Laboratory*

## Ultrafast Structural and Electronic Transitions in VO2

**VO****2**

**Rutile**

**T > 350 K**

**Ultrafast Structural and Electronic Transitions in VO****2**

- A. Cavalleri et al. *Phys. Rev. Lett * **87**, 237 (2001)

**Femtosecond X-ray Diffraction**

**T < 350 K**

## EXAFS

**short-range distortions**
- (sensitivty to V and O)

**NEXAFS**
**electronic transition **

**Insulator**

**Metal**

- Abbate et al., *Phys. Rev. B*, **43**, (1991).

**Ultrafast Structural and Electronic Transitions in VO****2**

***A. Cavalleri - MSD***

## Characteristics for Ideal Source

-  (1)  temporal resolution   100 fs

-  synchronization to laser trigger

-  (2)  high average flux 108-1013 photons/sec/0.1% BW

-  (3)  tunable 0.3 keV - 20 keV

-  (4)  rep. rate: 100 Hz - 10 kHz

-  high average brightness  <1 mrad source divergence

**X-rays for Ultrafast Structural Dynamics**

-  pulse duration

## Generation of Femtosecond X-rays from the ALS

- laser

- wiggler

- bend
- magnet

- mirror

- beamline

- x-rays

- wiggler

- femtosecond electron bunch

- bend magnet beamline

- 30 ps electron
- bunch

- femtosecond
- laser pulse

- spatial separation
- dispersive bend

- W

- electron-photon interaction in wiggler

- femtosecond x-rays

- e-beam

**Generation of Femtosecond X-rays from the ALS**

- Zholents and Zolotorev*, Phys. Rev. Lett.*, **76**, 916,1996.

## Energy Modulation in the Wiggler

- total field energy:

- wiggler radiated energy:

- *E* (energy mod)

- Elaser

*****L** *= 1.55 eV

- ***L *19 period wiggler 25 fs laser pulse

- A*L* = 225 J

- ALS beam energy spread ~1.9 MeV    Eo =1.9 GeV

- Dynamics of Modulated  Electron Beam

- Laser requirements:

## Synchrotron Beam Slicing - Layout

**Synchrotron Beam Slicing - Layout**

## Femtosecond Pulses of Synchrotron Radiation

- Electron Density Distribution

- -3x to +3x

- +3x to +8x

- +4x to +8x

- Schoenlein et al., *Science, ***287**, 2237 (2000)

**Femtosecond Pulses of Synchrotron Radiation**

## Femtosecond Synchrotron Pulses 

**Femtosecond Synchrotron Pulses **
**from Bend-magnet Beamline (BL5.3.1)**

**Instrument response <150 fs**
-    • pulse duration plus measurement resolution
**Measurement during normal user operation**
-    • Protein crystallography wiggler
-    • 1.9 GeV superbend lattice

##  flux ~1013 ph/sec/0.1% BW

-  flux ~1013 ph/sec/0.1% BW

-  brightness ~1016 ph/sec/0.1% BW

-  flux ~1015 ph/sec/0.1% BW

-  brightness ~1019 ph/sec/0.1% BW

**Bend Magnet**

**Undulator**

**Femtosecond X-ray User Facility – Scaling the X-ray Flux**

## Femtosecond Undulator Beamline 6.0

- I.  Beamline for Femtosecond X-ray Science

-  super-conducting undulator/wiggler (1.5 T, 50 x 3cm period)

- III.  Laser: average power/repetition rate

-  40 W (1 mJ per pulse, 40 kHz)

**sector 6 - proximity to existing wiggler 200 fs x-rays**

- x**10****2**** increase in flux, **x**10****3**** increase in brightness**

- x**10 increase in flux**

-  beamline - highest possible flux and brightness 0.2-10 keV

- II.  Insertion Device(s)

- IV.  Storage Ring Modifications

-  local vertical dispersion bump – sector 6 and/or 5

## Layout of the Ultrafast X-ray Science Facility - ALS Sector 6

- superconducting
- undulator

## Femtosecond Undulator Beamline 6.0 Layout

- P. Heimann, H. Padmore, J. Comins et al.

**Technical Challenges:**
-  hard x-ray capability
-  high speed chopper (40 kHz)
-  gated detectors (~2 nsec)

## Superconducting Undulator

-  1.5 m undulator (3 cm period)
-  Peak Field: 1.5 T
-  Magnetic gap: 16 mm
-  Vacuum aperture: 12 mm (cold bore)
-  2-stage cryo-cooling

- R. Schlueter, S. Marks, G. Sabbi et al.

## Femtosecond Laser System

**Femtosecond Laser System**

***Electron beam interaction requirements:***
-     ~1.5 mJ pulse energy, 50 fs FWHM, at ~800 nm
-     40 kHz repetition rate, 60 W average power
-     diffraction limited focusing, beam parameter: M21.1

***Excitation pump pulses for time-resolved experiments:***
-     ~1 mJ pulse energy at 800 nm (OPA)
-     50 fs pulse duration, 40 kHz repetition rate
-     ~500 ns relative delay

## Femtosecond Laser System: 2-pass Amplifier

- Ti:sapphire – cryogenic cooling

## Femtosecond Undulator Beamline

**Effective Isolation of Femtosecond X-rays**
- 	• mirror scattering theory and measurements
- 		(M. Howells, T. Glover et al.)
- 	• laser modulation of the electron beam
- 		modifications to protein crystallography wiggler, W16
- 		(R. Schlueter)
- 	• vertical dispersion bump
- 		(C. Steier, D. Robin, S. Zholents)

## Beam Profile Measurements – BL5.3.1 Camshaft Bunch

- 5 mrad

- x

- APD

- Si(111)

- - fraction of e-beam that is modulated = 75 fs  0.1 /75 psec = 10-4

- E/E=1/10

## Energy Modulation in the Wiggler

- total field energy:

- wiggler radiated energy:

- Elaser

- ***L *n19 period wiggler 75 fs laser pulse

- *E *9.5 MeV  **A*****L***** = 1 mJ**

- Laser requirements:

-  4.3 x AL for n=3

**1****st**** Harmonic Operation**

- `

## Femtosecond X-ray Profile Measurements

**Femtosecond X-ray Profile Measurements**

**1****st**** Wiggler Harmonic**

**3****rd**** Wiggler Harmonic**

- Emax=3E  (5.7 MeV)
- Emax=4E  (7.6 MeV)
- Emax=5E  (9.5 MeV)

- Emax=6E  (11.4 MeV)
- Emax=7E  (13.3 MeV)
- Emax=8E  (15.2 MeV)

- Calculated
- Electron Density Distribution

- Peak Laser Power ~ 10 GW
-                                   (0.8 mJ, 75 fs)

## Femtosecond X-ray Profile Measurements

- 1st Wiggler Harmonic

**Femtosecond X-ray Profile Measurements**

## Mirror Scattering – measurements from ALS BL10.3.2

**Mirror Scattering – measurements from ALS BL10.3.2**

- 	-  measured with a slit length of 2 x horizontal FWHM
- 	-  white light measurement; effective energy 13 keV
- 	- 15 m source - mirror and mirror - focus
- 	- Gaussian beam 110-4 at 100 m

- 	- fraction of beam that is kicked = 75 fs  0.1 / 75 psec = 10-4
- 	- position kick = 200 m  14 MeV kick, 4 cm dispersion, 1.9 GeV
- 	- for straight 6.0 undulator, y= 40 m  background at 300 m = 210-4

## —  model of 10.3.2 mirror scattering = 16 m

- — = 23.8 m
- — = 38.3 m

- -1

- -0.8

- -0.6

- -0.4

- -0.2

- 0

- 0.2

- 0.4

- 0.6

- 0.8

- 1

- 10

- -5

- 10

- -4

- 10

- -3

- 10

- -2

- 10

- -1

- 10

- 0

- -1

- -0.8

- -0.6

- -0.4

- -0.2

- 0

- 0.2

- 0.4

- 0.6

- 0.8

- 1

- 10

- -5

- 10

- -4

- 10

- -3

- 10

- -2

- 10

- -1

- 10

- 0

- y(m)

- y(m)

## Year 1

-  Modifications to protein crystallography wiggler
-  Prototype testing of power amplifier module
-  Vertical dispersion bump
-  R&D on superconducting undulator
-  R&D on mirror scattering
**Year 2**
-  Complete beamline design, begin fabrication
-  Complete undulator design, begin fabrication
-  Complete laser design and fabrication
**Year 3**
-  Complete beamline fabrication and installation
-  Laser installation and testing
-  Insertion device testing and installation

**Beamline 6.0 – Tentative Development Plan**

## Femtosecond X-ray Flux and Brightness

- Thomson Source:     flux:  2x103 ph/s/0.1% BW     brightness:  3x103 ph/s/mm2/mrad2/0.1% BW

- 103

- 104

- 105

- 106

- 107

- 108

- 109

- 1010

- 1011

- 1012

- photon energy (eV)

- flux (ph/s/0.1% BW)

- brightness (ph/s/mm2/mrad2/0.1% BW)

## Femtosecond X-ray Sources 

**Femtosecond X-ray Sources**** **

- 1) flux:
-       per mrad2 for plasma and Thomson sources, integrated over angular size of harmonic for undulator sources, <1 mrad V x 1 mrad H for bend magnet source
- 2) Synchronization: between x-ray source and a pump laser, <50 fs reflects passive (absolute) synchronization.
- 3) Energy Range: indicates the energy that can be covered in a discontinuous way, eg. changing targets in a laser plasma source
- 4) Spectroscopy (Y) indicates source can be tuned continuously at a rate suitable for spectroscopy, or is a white light source for dispersive spectroscopy
- 5) Thomson source assumes linac with 2 mm mrad norm. emitttance and 1 ps electron bunches

## Ultrafast X-ray Science Facility – Advanced Light Source

- Chemistry

- Biology,  Atomic and Molecular Physics

-  solid-solid phase transitions

-  order/disorder transitions (melting)

-  structural dynamics of the transition state

-  solvent/solute interactions (solvent structure)

- Time-resolved Measurements of Structural Dynamics in Condensed Matter

*** ******fundamental time scale for atomic motion - vibrational period ~100 fs***

-  200 fs x-rays - laser manipulation of e-beam

-  time-resolved spectroscopy  - passive synchronization, tunability

-  0.3-10 keV, superconducting undulator/wiggler

-  108 ph/s/0/1% BW,  1012 ph/s/mm2/mrad2/0.1% BW