1. No category

SLAC UED/UEM Initiative and UED@ASTA
Accelerator Directorate Review on UED@ASTA
X.J. Wang- May 20, 2014
Fundamental Probes in the BES
_
Parameter
Electron
Neutron
Photon
Charge
✔
Magnetic Moment
✔
✔
Mass
✔
✔
Spin
✔
✔
✔
Polarization
✔
✔
✔
Electrostatic
Nuclear
Electromagnetic
Thin
Thick
Medium
Force
Samples
• Users desire to use different probes to obtain complementary info
on samples
• Electrons & x-rays see electrons and proton, while neutrons can
see nuclei
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
4
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, Xray and optical laser pumping in conjunction with UED/UEM probes will open new
scientific opportunities.
electron
beam
THz
SLAC Lab Agenda (2014)
X-Ray
THz
6
SLAC UED/UEM Summary
~48 months (2019)
18 months (2015) 2016
*base design - upgrade - blue sky R&D
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Ultrafast (< 10 ps) imaging only possible at
higher voltages
Point Spread Function at 200 keV, 1 ns
-100 nm
-50 nm
0
50 nm 100 nm
Point Spread Function at 5 MeV, 10 ps
-100 nm
-50 nm
0
50 nm 100 nm
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, 114101 (2007).
Large Scattering Signal
R.Valle et al, Ultramicroscopy 27, 67 (1989)
Pump-probe Velocity Mismatch
ΔtVM > 1ps
60keV UED
Ve= 0.446c
𝑒−
ℎ𝜈
ΔtVM < 10fs
3MeV UED
Ve= 0.989c
𝑒−
ℎ𝜈
10
Sample Damage
• Knock on
• Pulse radiolysis
• Charging
R.F. Egerton et al. Micron 35，399 （2004)
Ultrafast Electron Diffraction (UED)
MeV-UED
Laser
BNL TEM
OPA / THZ
Syn
Axicon
RF
La0.5Sr1.5MnO4: Orbit & Charge Orders
Lens
Sample
RF Gun
Detector
Ultrafast Electron Diffraction (UED)
& Nano-UED
Laser
OPA / THZ
Syn
Axicon
RF
Lens
Condenser
Sample
RF Gun
Detector
Ultrafast Electron Imaging (UEM)
Laser
OPA / THZ
Syn
Axicon
RF
Lens
Condenser
Projector
Objective
Sample
RF Gun
Detector
UED @ ASTA?
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, semiconductor cathode, and X-band testing program
• Space and environment (temperature and vibration)
•
safety (laser and radiation), budget and resource (manpower).
• Others
The Accelerator Structure Test Area (ASTA)
UED@ ASTA Objectives
FY
14
• First 100 Femto-second MeV UED at high rep rate
Order of magnitude improvement (120 Hz vs 10 Hz)
• MeV UED Ultrafast Science
Goal: understand & control materials processes
related to heat-assisted magnetic recording
FePt
UV pump
• Understand and quantum control of chemical
reactions.
•Structure of intermediate states
Potential energy
heat sink
pp*
np* DE
Conical
Intersection
Ground
state
Reaction coordinate
Early Physics: UED@ ASTA (FY14)
Early Physics: UED@ ASTA (FY14)
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
Challenges in MeV-UED - Timing Jitter
Timing jitter
Laser
RF
Oscillator
RF Drive
Cathode
0
1"
2"
Scale
RF Gun
Δtjitter
3"
Sample
æ 1 1 ö Ldrift 1 æ DE ö
=ò ç
- ÷d »
÷
2ç
è V(t) c ø
b c g è E ø jitter
ALD Review on UED@ASTA Agenda
Start
​8:00
​8:30
​8:40
​9:10
End
​8:30
​8:40
​9:10
​9:30
Time
​0:30
​0:10
​0:30
​0:20
​9:30
​9:50
​10:05
​10:20
​10:40
​11:00
​11:20
​11:40
​12:00
​12:20
​01:00
​01:45
​03:00
03:30
​9:50
​10:05
​10:20
​10:50
​11:00
​11:20
​11:40
​12:00
​12:20
​01:15
​01:45
03:30
​0:20
​0:15
​0:15
​0:20
​0:20
​0:20
​0:20
​0:20
​0:20
​0:45
​0:45
​2:00
04:30
0:30
Title
Speaker
Executive session
​Welcome and charge to the committee
Bob Hettel
SLAC UED/UEM Initiative and UED@ASTA
​XJ Wang
​Science enabled by the UED/UEM and early science at ASTA
Hermann Durr
UED@ASTA project plan and ES&H
Carsten Hast
​UED@ASTA beam line and mechanical layout
​Eric Bong
​Coffee break
​Beam Dynamics study
Juhao Wu
​RF power stability
Minh Nguyen
​LLRF and timing triggers
​Stephen Weathersby
​Laser-RF timing and synchronization
​Joe Frisch
UED laser transport and pump-probe optics
​Ryan Coffee
UED commissioning
Renkai Li
​Lunch and discussion
​ASTA tour​Bldg. 44
​Executive session, report preparation + additional questions
Coffee
​Close-out
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.

UED@ASTA 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.
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