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MeV-UED Specifications

Here we briefly describe the scientific techniques available at MeV-UED and the instrument specifications.

Scientific Capabilities

Scientific Application 

Technique

Time-resolved measurement of electron–phonon coupling

Measurement of Debye-Waller effect on multiple lattice reflections

Time-resolved studies of momentum resolved phonon dynamics

Thermal diffuse scattering measurement

Measurement of melting dynamics

Single-shot pump–probe measurements

Three dimensional measurement of structural dynamics

Measurements of positional change of multiple lattice reflections at different sample orientations

Measurement of chemical photodissociation or photoisomerization

Gas-jet UED

Measurement of novel phase of quantum materials

Cryo-UED

 

Source Parameters

Parameter

Value

Electron beam energy

@360 Hz: 2 - 4 MeV

@1080 Hz: 2 - 2.3 MeV

Repetition rate

Single shot → 360 Hz & 1080 Hz

Other available rates: 1 Hz, 60 Hz, 120 Hz, 180 Hz, 540 Hz

Charge per pulse

1 - 100 fC (104 - 106 electrons)

Beam emittance

2 - 20 nm-rad

Bunch length

@360 Hz <150 fs FWHM**

@1080 Hz < 300 fs FWHM#

Momentum resolution

<0.17Å-1

Beam spot size

100-200 um (typical), 10 um (FWHM) focused

*Upgrade planned in 2024, **Beam charge dependent, #Limited by r.f. jitter, contact staff for latest information.

 

Optical Laser Properties

Parameter

Value

Repetition rate

Single shot → 1080 Hz

Wavelength range

200 nm, 266 nm, 400 nm, 800nm, 240 nm - 2 µm tunable, 3-15 µm tunable

Typical optical pulse energy

> 8 mJ @ 800 nm
> 0.8 mJ @ 400 nm
> 0.08 mJ @ 266 nm
~ 16  µJ @ 200 nm
For pulse energies at specific wavelengths (e.g. 260 nm – 750 nm) or other details please contact Patrick Kramer

Nominal pulse duration

75 fs (FWHM)

Optical delay

0 - 1.5 ns (physical delay stage) Contact laser group about longer delays.

Optical spot size

200 - 1500 µm (FWHM)

*Upgrade planned in 2024

Detectors

Detector Parameter

Andor EMCCD

ePix direct electron detector

Detector system 

description

Electron diffraction patterns are collected on a P43 phosphor screen which is imaged via a 45 degree mirror using a Andor iXon Ultra 888 EMCCD

Diffraction patterns are recorded via direct electron detection on the ePix10k camera.

Operational mode

Integrating on the camera with times typically from 2 - 30 seconds.

Shot-by-shot readout at up to 360 Hz repetition rate

  • pedestal (dark count) subtraction
  • None-peakfinding (Direct integration mode)
  • Peakfinding (Single electron counting mode)

 

Point-spread-function

85 µm (rms)

< 4 pixels (full width)

Sensor size

1024 x 1024

7.5 x 7.5  cm2

Pixel size

13 µm x 13 µm

100 µm x 100 µm 

Gain

Variable 3-1000

3 gain modes (High/Medium/Low)

Data format

Legacy DAQ - .tiff

LCLS-II DAQ - converted to hdf5

-.xtc raw data files

-peak finding reduction data saved 

to .hdf5 files

Single electron 

detection

no

yes

In-active Area

Center hole in phosphor 

Horizontal/vertical gaps between modules covering < 10% of the detector area

 

 

 

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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Menlo Park, CA 94025
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