UESDM UCLA Dec 12–14 2012UESDM, UCLA, Dec. 12 14, 2012

MeV electron diffraction and microscopyin Osaka Universityin Osaka University

Ji f g Y gJinfeng YangOsaka University, Japan

Collaborators:

y p

(RIKEN) Yoshie Murooka(Osaka Univ.) Y. Naruse, K. Kan, K. Tanimura, Y. Yoshida

OutlineOutline

1. Development of RF gun for UED/UEMRequirements / experimental results

2. RF gun based UED at Osaka Univ.MeV UED systems / measurementsy /

3. RF gun based UEM at Osaka Univ.prototype of RF gun based UEMprototype of RF gun based UEMfirst electron image measurement

4 Conclusion4. Conclusion

Ph t th d RFPhotocathode RF gunfor electron diffraction/microscopyfor electron diffraction/microscopy

in Osaka Univ.

What requirements for UEM?qFemtosecond laser

fs λ=266nm

RF2856MHz、~MW＠4μs

fs, λ=266nm Femtosecond e- bunch~MeV, ~pC

PhotocathodePhotocathodeCu, Mg RF cavity,~100MV/m

(Usually 1.5-cell)

Bunch length： ≤100 fs

The expected beam parameters:

Beam energy： 1~3 MeVEmittance： ~0.1 mm-mradEnergy spread： ~10-4 (10-5 for challenge)e- number： 107-8 e-’s/bunch (1~10 pC)

with ultralow dark current

New femtosecond RF gung

Developed under the collaboration with KEK

•remove two laser injection ports

Improvements:remove two laser injection ports

•a new turner system•new structure cavities•a new insertion function of photo•a new insertion function of photo-cathode (The photocathode is removable)

The mode separation between π mode andThe mode separation between π mode and 0 mode is increased up to

fπ - f0 = 8.5 MHz.The Q value is increased up to 14,500.(The cooling system and waveguide design are same

as the BNL gun-IV.)

Transverse beam dynamics in RF gunExperiment studies of femtosecond e- beam in RF gun

(exp. conditions: 100 fs UV laser, 30o gun phase, 3MeV)

y g

mradmmEkin −≅= 180σε

Reducing laser spot size to 0.1mm,

d10

For a copper cathode, the thermal emittance can be

mradmmcmrth ≅= 18.02

0

σε

eVEhvEkin 26.0sin0 ≅+−= θβαφmradmm −1.0~ε

RF gun based MeV electron diffraction at Osaka Univ.

Electron energy: 1～3 MeVTime resolution: 100 fs

RF gun based MeV UED at Osaka Univ.g

Sample

use of electron optical lenses as like in electron microscopy

ApertureΦ0.3mm Scintillator

RF gun1-5MW@4μs,10Hz2856MHz

<10-8PaSolenoid

Φ3.0mm

Sample

sample

P LD L

C.LensSolenoid

Φ

EMCCDProbe 3ω:257nm,90fs,1kHz 6mW

Pump 2ω:385nm,90fs, 10Hz ＜40mJ/cm2

P.LensD.Lens Φ300, 350μm

Area: 5x5cmCsI (Tl) scintillator

1kHz, 6mW 10Hz, ＜40mJ/cm2

Pump 2ω(Φ600μm,

[1-10]

Area: 5x5cm

Diffraction

3MeV100 fs e pulse

10Hz

Probe 3ω(Φ600μm,

18.2o,p-pol )

4.5x107 e/pulse100 fs e- pulse aperture

Φ0.3mm diffractionSi crystal

Picture of UED system at Osaka Univ.Picture of UED system at Osaka Univ.

RF gunS.LCL

DLPL

S

CCD 2 5 m

use of electron optical lenses, therefore, compact.

2.5 m

Quality of MeV electron diffractionQ yElectron beam: 3 MeV, Sample: 180nm-thick single crystal Si Intensity profile of 620 pattern

pulsecme //109.8 27×

Si<001>

62020 shots(2s)

• Beam convergence angle: 50 μrad • Bragg law

A highA high--quality quality MeVMeV ED was observed!ED was observed!

Beam convergence angle: 50 μrad2d sin θ = nλ

gg

LD=α2tan

• Maximum scattering vector : qmax >1.56Å-1

• Requirement of the e- number: 106-7 Lq

Y. Murooka, et al., Appl. Phys. Lett. 98, 251903 (2011)

Power of the technique: static diffractions• Single-shot measurement

Power of the technique: static diffractions

1 shot (0.1s)Sisingle crystalThickness: 180nm

1 shot (0.1s)Ausingle crystalThickness: 20nm

e- energy: 3MeV

Y. Murooka, et al., Appl Phys Lett

e- energy: 3MeV

M t l (Al) I l t

SiAppl. Phys. Lett. 98, 251903 (2011) Au

• polycrystal (100nm)

• Metal (Al)• Single crystal (~100s nm)

t

K(Fe,Mg)3(AlSi3O10)(OH,F)2

• Insulator (Mica)

200220311

331422

440

fcc

top side

KSiO4

SiO4

Fe, Mg

111200

600No charging effect(Difficult at Low Voltage)

Large scattering vectorqmax

Time-resolved measurement #2Laser heating and melting dynamics of single crystal Au

Time resolved measurement #2

200

after melting16 ps3 ps-4 ps

RF gun basedultrafast electron microscopyultrafast electron microscopy

Electron beam energy: 1～3 MeVElectron beam energy: 1～3 MeVTemporal resolution: 100 fsSpatial resolution: 10 nm

Concept of RF gun based UEMConcept of RF gun based UEMSpecimen50μm spot

Objective lensaperture-2RF gun

RF

Intermediate Solenoid

lens

5μm spotCL 1

50-fs laser

Projector

5μm spotCL-1

CL-2 Projector lens

CL 2

aperture-1

Image screen(1024x1024 pixels)

10μm spotSpecimen

Prototype of RF gun based MeV electron microscopy

RF gun

RF gun based MeV electron microscopy

Femtosecondphotocathode Femtosecondphotocathode

FemtosecondLaser

RF gun

electron gunelectron gunFemtosecondelectron beam

Electron energy： 1~3 MeVBunch length ： ≦100 fsEmittance： < 0 1mm mrad

3m

Emittance： < 0.1mm-mradEnergy spread： 10-4 (10-5 for challenge)Charge： 107~108e-’s/pulse

electron optical lenses

imageTime resolution: 100 fsSpatial resolution: 10 nmTime resolution: 100 fsSpatial resolution: 10 nm

imagemeas.

Challenge !Challenge !Prototype of MeV UEM

Prototype of RF gun based MeV electron microscopyRF gun based MeV electron microscopy

RF gun based injector 2T objective lens Interm. & proj. lenses

FemtosecondLaser

Femtosecondelectron beamFemtosecondelectron beam

Image recording system

2010 2011

g g y

Prototype of UEM（height: 3m, diameter: 0.7m）

The prototype was constructed at the end of Oct. 2012.

2012

Detection of MeV electron images

CsI (Tl) scintillator

g

•Illu. Vol.(<50µm)• Bright• High resol. (C l S )

( )(Hamamatsu)

MeV electron

(Column Structure) • Tough (for High E Xray)

• Large: 5x5cm

Thi P l i (5 )Thin Polymer mirror (5µm)ORCA-R2 CCD

X, e

The detection system was successfully used in UED measurement.(single-shot measurement with 105 e-s/pulse)(single shot measurement with 10 e s/pulse)

MeV electron diffraction in UEMMeV electron diffractions observed with 10 pulses and single-shot measurements

First exp. at Nov. 9, 201210 pulses

Electron beam (2 MeV)

diff. plane

Objective Lens

Specimen

diff. plane（BFP）

Single-shotImaging plane

(Selector diaphragm)Projector

lens

Sample： Au single crystal, ~15 nmElectron charge： ~100 fC/pulse

on the scintillator

MeV electron imaging in UEM

Images of

First exp. at Nov. 10, 2012 38 μm

Images of Au film

Exposure time：2s Exposure time：60s

Electron beam (2 MeV)

Specimen83μm

x50

Observed images of Au film

Exposure time：2s Exposure time：60s

10μm 38nm/pixel

BFP(Obj. Aper.)

Objective Lens

μ 38nm/pixel

Interm.image planeProjector

X385 x650 x1200

10

Projectorlens

Observation #110μm 38nm/pixel

Sample： Au single crystal, ~15 nmElectron charge： ~10 fC/pulse

Final image screen

19x650 x1200

Electron charge 10 fC/pulse on the scintillator Observation #2

Magnifications & spatial resolution

5.5 μmSolenoid lens

RF gun

Cu grid(1000mesh)

25μmFemtosecondelectron beam

CL-1

CL-2

5 μm 30 nm/pixel75 nm/pixel10μm

X200

Objective lens

Specimen

I t di t/p

Intermediate lens

Projector lens

観測例① X650 x1700

σ～300nm

σ～300nm

Spatial resolution in future300 nm

10 σ 300nm10nm

<1nm

Next TEM: “Dream TEM”

photocathodephotocathode

Weight: 140t

photocathode RF gun

photocathode RF gun

15cm

10m

Compact High-voltageCompact High-voltageTransmission Electron Microscopy

•high-voltage TEM function•high-voltage TEM function(nm or sub-nm, MeV)

+•time-resolved function

3m

3m

time resolved function (femtosecond)

Next TEM Dream TEM!Standard 3-MeV TEM

at Osaka Univ.

Next TEM Dream TEM!

New science and technology using UEM

Imaging Technologyイメージング テクノロジー

Pump laser pulse

Structural observation and imaging in “real space” with atomic-scale spatial resolution using high-energy electron beam.

Electron pulse（probe）

Methods

Electron beam（1～3MeV） Ultrafast

Observation超高速現象の観察

Observations of fundamental dynamic processes in matter occurring on femto-second time scales over atomic spatial dimensions.

超高速現象の観察

Compact high-voltage electron microscopy

MeV UEMMeV UEM

TargetsProtein Structural Dynamicsタンパク質構造ダイナミクス

Making Molecular Movie

Nano-technologyナノテクノロジー

(dream TEM)

•Visualizations of protein structural dynamics using ultrafast electron diffraction and imaging technique.

Making Molecular Movie分子運動の可視化：－新しい科学－

•Observation of single molecule motion.Ultrafast chemical reactions

•Photon-induced ultrafast dynamics of novel nano-scale materials.•Creation of new functional materials and devices for nanotechnology.

•New technologies and applications in medical biology.

•Ultrafast chemical reactions.•Discovery of transition states and reaction intermediates.

ConclusionConclusion

Both RF gun based UED and UEM systems have been constructed atg yOsaka University.In UED, single-shot and time-resolved measurements have beensucceeded In UEM the MeV electron imaging experiment was carried outsucceeded. In UEM, the MeV electron imaging experiment was carried out.Both experiments suggest that RF gun is very useful for ultrafast MeVelectron diffraction and is also expected to be used in ultrafast electronmicroscopy.

However, great efforts and many challenges are required:

reduce further the emittance (<0.1 μm) and energy spread (10-5 or less),increase the beam brightness,i th t biliti th h g d gimprove the stabilities on the charge and energy,develop a detection of very electron with MeV energy region.