UltraUltra--fast Xfast X--ray Streak Camera ray Streak Camera Development and application at the ALSDevelopment and application at the ALS

Jun Feng

Advanced Light Source, LBNL

International symposium on the development of detectors for partInternational symposium on the development of detectors for particleicleastroastro--particle and synchrotron radiation experiments, 4/6/2006, SLACparticle and synchrotron radiation experiments, 4/6/2006, SLAC

Collaborators:Collaborators:

W.Wan , J.W.Wan , J.QiangQiang, J.Byrd, G.Huang (ALS / AFRD, LBNL), J.Byrd, G.Huang (ALS / AFRD, LBNL)

A.A.BarteltBartelt, A. , A. CominComin, , J.J.NasiatkaNasiatka, A. Scholl, A. Scholl, H.J.Shin, A.H.J.Shin, A.MacPheeMacPhee, D.Weinstein, , D.Weinstein, T.Young,T.Young, and H.A.and H.A.PadmorePadmore (ESG / ALS, LBNL)(ESG / ALS, LBNL)

R. R. FalconeFalcone (UCB Physics)(UCB Physics)

1. Introduction

2. Ultra-fast X-ray streak camera program at the ALS

3. Magnetization dynamics application

4. Extending the performance of streak cameras to 100 fsec and beyond

5. conclusion

Outline

Photocathode

Anode Mesh)

Magnetic lens 2-D Detector

Sample

Tim

e

Space

Streaked image

Swee

p

X-rays

Introduction: Streak camera principle

X-ray

Convert fast time information into space information that can be recorded on an area detector

2222scjittersweepph τττττ +++=

Introduction: X-ray streak camera features and application

Features

- good temporal resolution (at present psec, could be 100 fsec or better)

- records the whole temporal response (ps-ns)

- wide photon energy range 10ev to 10kev

-simple and inexpensive

Applications

- Dynamics, like ultra-fast magnetization dynamics

- Diagnostics, Sliced X-ray source, XFEL

- plasma physics

- Ultra-fast electron diffraction

ALS x-ray streak camera

Au Photocathode

Anode Mesh (0 V)

Magnetic lensMCP

Sample in transmission

Tim

e

Space

RecordedStreak image

Meander plates parallel

to timing slit

Swee

p

Phosphor

CCD

Photoconductive GaAs switch for triggering

ALS streak camera program

Development area

• Photocathode: Increasing photocathode efficiency, reducing radiation damage

• Photo-conductive switch: efficiency, fast rise-time, Reduction of jitter

•Electron optics: reduction of aberration, compensation of chromatic aberration

•Modeling of Meander-plate: increase sweep speed

ALS-made PC switch : saturation range

- semi-insulating GaAs

- fabricated in-house

- Reliable 1kHz, 5 KHz operation at 500V

-10-90% ramp ~180 psecdetermined by the time window of ALS ring (~100ps)

- Switched efficiency ~90%

Static mode: image quality

Off axis

25um8um

Dynamic mode: UV imaging v. Energy

7.5keV, sep: 103px, FWHM:8-9px, 1k shot,1000fs

10keV, sep: 144px, FWHM:9px, 1k shots, 800fs

Sweep speed: 90fs/px

- excellent single shot resolution: 600fs

- photoconductive switch jitter reduction

- double switch, J.Kineffer, jitter-free

- Liu, 30fs jitter

- fast readout CCD

ALS Streak camera R&D lab

Power supply

50Ghz oscilloscope

Optical layout

chamber

Ti: Sapphire Lasers: 1 beamline and 1 lab system

KMlab 62.5 MHz oscillatorPositive Light Legend Laser:30 fsec, 0.6 mJ / pulse, 5 KHz

Femto-laser OscillatorPositive Light Legend Laser:30 fsec, 1 mJ / pulse, 1 KHz

1. Introduction

2. Ultra-fast X-ray streak camera program at the ALS

3. Magnetization dynamics application

4. Extending the performance of streak cameras to 100 fsec and beyond

5. Conclusion

Outline

What is the speed limit of magnetic recording?

State-of-art storage: long range interaction, low density, ns switching

future storage: local interaction, high density, ps switching

Is the early optical experiment accurate ?TR-Kerr measurements show different results

How does energy flow in a magnetic system when changing the magnetization?

- electron, spin, lattice, spin-orbit coupling

Motivation

L0

Laser System Setup

Beam, 800nm, 5Khz, 50fs

M1

Filter L01 Camera

BS1

M2

M5

M3

M4

L1 L2

PD

Trigger

GaAs

Diffuser

oscilloscope

2ω3ωλ/2

∆t

UVM1

UVM2

UVM4

UVM5

UVM6

UVM3

BS2

@4m

Delay 3

∆t1

∆t2

266nm

Delay 2

X-ray

Samplechamber

delay1

Delay 4KM 62.5 MHz Osc.

Positive Light regenLegend amplifier0.6 mJ, 5 kHz, 50 fsec 4 beams with 4 delays (0.6 mJ total)

- IR pump beam- IR to streak camera PC switch trigger- uv for temporal fiducial to photocathode- uv for timescale calibration to photocathode

Streak camera on ALS EPU BL 4

Laser,UV

X-ray

transmissionsample

magnet for field reversal

streak cameraCCD camera

It works: demagnetization happens within picoseconds

Streaked x-ray pulse and UV fiducials

UV fiducials

X-ray pulse

time

Full demagnetization is observed

XMCD streak at “time zero”

time

laser

sample

time

hν

1. Introduction

2. Ultra-fast X-ray streak camera program at the ALS

3. Magnetization dynamics application

4. Extending the performance of streak cameras to 100 fsec and beyond

5. Conclusion

Outline

Photocathode

Anode Mesh)

Magnetic lens 2-D Detector

Sample

Tim

e

Space

Streaked image

Swee

p

Corrector needed

- Photocathode has negative time dispersion Dt/DE=-k- ie. low energy electrons take the longest time

- fundamental resolution limit set by energy spread from photocathode

Au,Wf=4.6ev, FWHM=3.8ev, 10kV/mm field, ~500fs

CsI Wf=1.9ev, FWHM=1.5ev, 10kV/mm field, ~350fs

X-rays

corr

ecto

r

- need an additional element to produce positive energy dependent time of flight-corrector gives positive energy dependent time of flight dispersion

- low energy electrons take the shortest path and therefore take the shortest time

Chromatic time of flight correction in a streak camera

- 4 dipoles can be arranged to be double focusing, achromatic, zeroangular time of flight dispersion and with defined dT/dE for correction

- < 50 fsec resolution from initial simulation!

D

D

D

D

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

-150 -100 -50 0 50 100 150 200

dE_k

(eV

)

t (fs)

Longitudinal Phase Space

objectiveobjective and compressor

Temporal Deviation (fsec)

En

erg

y D

evia

tio

n (

eV))

corrector removesstraight line

uncorrected

corrected

Time-dependent 3D field in meander plate

End-to-end modeling

Using 3D time – varying field, end to end modeling is developed, full simulation can be done

Conclusion

• sub-psec 5 KHz streak camera has been developed at ALS

• psec magnetization dynamics program underway at ALS

• 50 fsec resolution appears possible using dispersion compensation

Acknowledgement

This work was support by the U.S. Department of Energy under contract No.DE-AC02-05CH11231, and LDRD of Lawrence Berkeley National Laboratory