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MeV-UED Endstations

 

The SLAC UED system supports multiple sample chambers optimized for different types of sample delivery. Please note that not all endstations may be available for the current general User Program.

MeV-UED Solid State (Materials) & Warm Dense Matter (Single Shot) 
Endstations

Sample motion

5-axis sample motion
Transverse to beam:
    X (horz): 50 mm (5 um resolution)
    Y (vert): 25 mm (0.1 um resolution)
Along beam:
    Z (horz): 25 mm (5 um resolution)
Rotations:
    Yaw (about Y): +/- 45 degrees
    Pitch (about X): +/- 45 without cooling;
                                    +/- 15 with cooling.

Sample Cooling

30 - 300 K

Diagnostics

Frosted YAG for electron/laser overlap
Single-crystal gold for q reference
Si temperature sensor
Bi for time-zero reference

Sample mounting

TEM mesh grids
TEM Si3N4 membranes
Si3N4 membrane arrays (contact)

Vacuum

<1 x10-7 Torr

MeV-UED Gas Phase Endstation

Sample Temperature Range

Sample reservoir: RT - 50 °C (flow cell) & RT - 150 °C (pulsed nozzle)
Transport line : RT - 80 °C (flow cell) & RT - 180 °C (pulsed nozzle)
Pulsed nozzles : RT - 200 °C
Flow cell: RT to ~ 100 °C

Sample Vapor Pressure Requirement

> 100 torr at 150 °C for pulsed valves
> 0.5 torr at RT for flow cell (3 to 4 mm path length)

Sample Reservoir Size

100 mL (e.g. standard 2.75 CF nipple)

Buffer Gas (optional)

Helium, 5 bar for Parker general valve

Nozzle Properties

Pulsed, up to 180 Hz
100 - 200 µm orifice
Typical opening time: 100 - 300 µs

Gas Jet Size (FWHM)

200-400 µm

Nozzle motion

3-axis translational motion
X (Horizontal in lab, perpendicular to beam propagation direction): 2"
Y (Vertical in lab): 2"
Z (Horizontal in lab, beam propagation direction): 2"

Cold Trap Temperature

< 100 K

Diagnostics

Frosted YAG for electron/laser overlap
Single-crystal Au/Si for Q reference and time zero reference (within 400 fs)

Pump-probe propagation angle

~2°

Vacuum

Operation condition:
Flow cell operates at 1-10 Torr
Background pressure ~10-6 - 10-4 Torr

Gas Line Material

Stainless Steel

Nozzle Puppet/Seal Materials

Vespel (Parker general valve; series 9)
Polyimide (for high repetition rate valves)

Flow cell materials

(1) Stainless steel  (2) Macor ceramic

Q range

0.5 to 12  Å-1

Q resolution (FWHM)

0.17  Å-1

Time resolution (FWHM)

150 fs

Pump Wavelength

200 nm, 266 nm, 400 nm, 800nm, 240 nm - 2 µm tunable

Delay Stage Range

2 ns

Delay Stage Resolution

7 fs

MeV-UED Liquid Phase Endstation

Sample Delivery

Converging sheet jet

  • Jet thickness > 250 nm thickness

  • Flow rate ~2.7 mL/min

  • Viscosity range < 0.1 Poise

Gas Accelerated Jet – contact for details

Recirculation

Yes, volume required > 50 mL (> 500 mL recommended)

Nozzle motion

3-axis motion: X, Y &  Z

Optical Pump Geometry

Collinear or 30 degrees to sheet normal

Samples

Neat liquids & Solutions

  • Organic and inorganic liquid solvent with pressure limit up to 25 torr. Examples are listed:

    • 1-propanol (14.9 Torr at 20 ℃)

    • water (17.5 Torr at 20 ℃)

  • Delivery solvent above 25 Torr (at 20 ℃) is under development (R&D in progress) with limited support. Feasibility will be reviewed by the UED facility team. You are highly recommended to consult the local UED team before proposal submission.

  • Organic or inorganic solute: Solutes need to be well mixed with solvents across a large temperature range with relatively high concentration, >0.5 M.

Solutes that are easy to come out of solution below 0 ℃ are not favorable due to clogging. 

Reference Material

J. P. F. Nunes, K. Ledbetter, M. Lin, M. Kozina, D. P. DePonte, E. Biasin, M. Centurion, C. J. Crissman, M. Dunning, S. Guillet, K. Jobe, Y. Liu, M. Mo, X. Shen, R. Sublett, S. Weathersby, C. Yoneda, T. J. A. Wolf, J. Yang, A. A. Cordones and X. J. Wang, "Liquid-phase mega-electron-volt ultrafast electron diffraction", Struct. Dyn. 7, 024301 (2020) doi: 10.1063/1.5144518

MeV-UED Contacts

Alex Reid

MeV-UED Facility Director & Instrument Lead
(650) 926-7467
alexhmr@slac.stanford.edu

Joel England

MeV-UED Accelerator Lead
(650) 926-3706
england@slac.stanford.edu

Stephen Weathersby

Area Manager
(650) 926-3890
spw@slac.stanford.edu

Ming-Fu Lin

Lead Scientist
(650) 926-2586
mfucb@slac.stanford.edu

Matthias Hoffmann

Lead Laser Scientist
(650) 926-4446
hoffmann@slac.stanford.edu

Xinxin Cheng

Staff Scientist
xcheng@slac.stanford.edu

Patrick Kramer

Laser Scientist
(650) 926-5148
pkramer@slac.stanford.edu

Randy Lemons

Laser Scientist
(650) 926-3477
rlemons@slac.stanford.edu

Cameron Duncan

Associate Scientist
cjduncan@slac.stanford.edu

Fuhao Ji

Associate Scientist
(650) 926-4678
fuhaoji@slac.stanford.edu

Yusong Liu

Associate Scientist
yusongl@slac.stanford.edu

Aaron Garza

Staff Engineer
(650) 926-4282
aarongs@slac.stanford.edu

Ian Roque

Staff Engineer
(650) 926-3407
iroque@slac.stanford.edu

Tianzhe Xu

Research Associate
txu@slac.stanford.edu

Sharon S. Philip

Research Associate
sharonsp@slac.stanford.edu

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