1. SLAC UED/UEM Initiative and UED@ASTA
Accelerator Directorate Review on
X.J. Wang- May 20, 2014

2. Fundamental Probes in the BES
Parameter
Electron
Neutron
Photon
Charge ✔
Magnetic Moment
Mass
Spin
Polarization
Force
Electrostatic
Nuclear
Electromagnetic
Samples
Thin
Thick
Medium _
Users desire to use different probes to obtain complementary info on samples
Electrons & x-rays see electrons and proton, while neutrons can see nuclei

3. SLAC UED/UEM ini
Is also well aligned with the DOE mission – that is to develop state of art intrumentation

4. DOE BES Future Electron Scattering and Diffraction Workshop
A – Multidimensional Visualization of Real Materials
B – Atomic Scale Molecular Processes
C - Photonic Control of Emergence in Quantum Materials
D - Evolving Interfaces, Nucleation, and Mass Transport
Ultrafast Electron Diffraction and Microscopy Facility
B.1 – Source (MeV) and Electron Optics:
B.2 - Pump Technology

5. The UED-UEM initiative at SLAC/Stanford
Vision: The SLAC UED/UEM facility will be the world leading electron scattering instrumentation facility, complementary to the LCLS X-ray FEL. The UED/UEM facility will possess unique capabilities that enable Grand Challenge science in chemistry, material science, physics and biology. The availability of intense THz, X- ray and optical laser pumping in conjunction with UED/UEM probes will open new scientific opportunities.
THz
electron
beam

6. SLAC Lab Agenda (2014) X-Ray THz What is make the UED/UEM uniques
Two things.
One is uniques capble. And other is the broad user community.

7. SLAC UED/UEM Summary 18 months (2015) ~48 months (2019) 2016
*base design - upgrade - blue sky R&D

8. Ultrafast (< 10 ps) imaging only possible at higher voltages
Point Spread Function at 200 keV, 1 ns
50 nm
100 nm
-50 nm
-100 nm
Point Spread Function at 5 MeV, 10 ps
For picosecond resolution imaging, relativistic energies may be the only way to obtain high spatial resolution.
M. R. Armstrong, B. W. Reed, B. R. Torralva, and N. D. Browning, Appl. Phys. Lett. 90, (2007).

9. Large Scattering Signal
R.Valle et al, Ultramicroscopy 27, 67 (1989)

10. Pump-probe Velocity Mismatch
60keV UED
ΔtVM > 1ps
Ve= 0.446c
𝑒 − ℎ𝜈
3MeV UED
ΔtVM < 10fs
Ve= 0.989c ℎ𝜈
𝑒 −

11. Knock on Pulse radiolysis Charging Sample Damage
R.F. Egerton et al. Micron 35，399 （2004)

12. Ultrafast Electron Diffraction (UED)
La0.5Sr1.5MnO4: Orbit & Charge Orders
MeV-UED
BNL TEM
Laser
OPA / THZ
Syn
Axicon
UV Optics RF
RF Gun
Lens
Sample
Detector

13. Ultrafast Electron Diffraction (UED)
& Nano-UED
Laser
OPA / THZ
Syn
Axicon
UV Optics RF
RF Gun
Lens
Condenser
Sample
Detector

14. Ultrafast Electron Imaging (UEM)
Laser
OPA / THZ
Syn
Axicon
UV Optics RF
Projector
RF Gun
Lens
Condenser
Objective
Sample
Detector

15. UED @ ASTA? ASTA the most favorable site for fast impact experiments,
There are three potential sites at SLAC could be considered for the first phase of UED. Those three sites are ASTA, NLCTA and LCLS II injector.
ASTA the most favorable site for fast impact experiments,
Existing RF gun and infrastructure.
Laser system.
Synergy with LCLS cathode R&D – thermal emittance reduction.
X-band for beam diagnostics
Concerns:
Impact to existing program: LCLS cathode R&D, semi-conductor cathode, and X-band testing program
Space and environment (temperature and vibration)
safety (laser and radiation), budget and resource (manpower).
Others

16. The Accelerator Structure Test Area (ASTA)

19. UED@ ASTA Objectives FY14
First 100 Femto-second MeV UED at high rep rate
Order of magnitude improvement (120 Hz vs 10 Hz)
MeV UED Ultrafast Science
FY14
FePt
2nm
heat sink
Goal: understand & control materials processes related to heat-assisted magnetic recording
Understand and quantum control of chemical reactions.
Structure of intermediate states

20. Early Physics: UED@ ASTA (FY14)

21. Early Physics: UED@ ASTA (FY14)

22. Challenges in UED @ ASTA
Time and resource
Infrastructure upgrade – ASTA bunker space and laser room air conditioning
Technical challenges:
Electron beam line ( diagnostic, sample chamber and detector)
Laser RF synchronization
Low level RF
Klystron modulator
Laser transport and pump-probe optics

23. Challenges in MeV-UED - Timing Jitter
Laser RF
Oscillator
RF Gun
RF Drive
Cathode
Sample
Δtjitter =

24. ALD Review on UED@ASTA Agenda
Start End Time Title Speaker
​​​8:00 ​​8:30 ​​0:30 Executive session ​
​​​8:30 ​8:40 ​0:10 ​Welcome and charge to the committee ​ Bob Hettel
​​​8:40 ​9:10 ​0:30 SLAC UED/UEM Initiative and ​XJ Wang
​​​​9:10 ​​9:30 ​0:20 ​Science enabled by the UED/UEM and early science at ASTA ​Hermann Durr
​​​​9:30 ​​9:50 ​0:20 project plan and ES&H ​Carsten Hast
​​​​9:50 ​​10:05 ​0:15 beam line and mechanical layout ​Eric Bong
​10:05 ​​10:20 ​0:15 ​Coffee break ​
​​10:20 ​​​10:50 ​0:20 ​Beam Dynamics study ​ Juhao Wu
​​10:40 ​11:00 ​0:20 ​RF power stability ​ Minh Nguyen
​​​11:00 ​11:20 ​0:20 ​LLRF and timing triggers ​Stephen Weathersby
​​11:20 ​​11:40 ​0:20 ​Laser-RF timing and synchronization ​Joe Frisch
​11:40 ​12:00 ​0:20 UED laser transport and pump-probe optics ​Ryan Coffee
​12:00 ​12:20 ​0:20 UED commissioning ​ Renkai Li
​12:20 ​01:15 ​0:45 ​Lunch and discussion ​
​01:00 ​01:45 ​0:45 ​ASTA tour ​Bldg. 44
​01:45 ​03:30 ​2:00 ​Executive session, report preparation + additional questions ​
​03:00 ​ Coffee ​
​03:30 ​​04:30 ​0:30 ​Close-out

25. Summary
The SLAC UED/UEM facility will be the world leading electron scattering instrumentation facility, complementary to the LCLS X-ray FEL. The UED/UEM facility will possess unique capabilities that enable Grand Challenge science in chemistry, material science, physics and biology. The availability of intense THz, X-ray and optical laser pumping in conjunction with UED/UEM probes will open new scientific opportunities.
will be the first step toward SLAC UED/UEM facility, it will be the first UED breaking 100 fs barrier and enable some exciting science. We have a realistic plan to realize the first experimental in FY 2014.