MeV-UED 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

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