CITIUS Instrumentation

1. High-harmonic generation beamline

The CITIUS laboratory is equipped with a high-harmonic generation (HHG) beamline delivering extreme-ultraviolet pulses as short as 30 fs in the spectral range from 16 to 62 nm (20 to 80 eV) at a repetition rate of 5 kHz. The beamline consists of a generation chamber that contains a gas cell (typically filled with Ar or Ne) and a monochromator with a set of off-plane geometry gratings for ultrafast time resolution (from few to several tens of fs) and medium energy resolution (from 100 meV to 400 meV), and a set of classical geometry gratings for high energy resolution (from 15 meV to 40 meV) and a long time response (a few 100 fs).

HHG performance

HHG photon flux as a function of photon energy for Ar and Ne.

HHG pulse characteristics (100 μm monochromator exit slit; H15, i.e., 23.2 eV)

Grating Duration (fs) Energy resolution (eV) Fourier limit (eV)
OPG G200 23 ± 1.2 0.5 0.08
OPG G400 35 ± 1.7 0.25 0.052
OPG G600 35 ± 1.9 0.16 0.052
CG G300 170 ± 10 0.03 0.01
OPG=off-plane geometry grating; CG=classical geometry grating; 

Characteristics of the monochromator gratings

Off-plane geometry (OPG)
G200 (groove density: 200 gr/mm)
Spectral region
Energy resolution

100-250 nm (12-5 eV)
G400 (groove density: 400 gr/mm)
Spectral region
Energy resolution

27-100 nm (45-12 eV)
G600 (groove density: 600 gr/mm)
Spectral region
Energy resolution

12-40 nm (100-30 eV)
Classical geometry (CG)
G300 (groove density: 300 gr/mm)
Spectral region
Energy resolution

80-250 nm (16-5 eV)
G600 (groove density: 600 gr/mm)
Spectral region
Energy resolution

50-100 nm (25-12 eV)
G1200 (groove density: 1200 gr/mm)
Spectral region
Energy resolution

30-60 nm (41-21 eV)

The HHG beamline with the generation chamber (left), monochromator (middle) and slits (right) for adjusting the spectral resolution and photon flux.

2. Experimental chamber

The experimental chamber for time and angle resolved photoemission spectroscopy is equipped with a VG-Scienta R3000 electron spectrometer, 5 degrees of freedom (x,y,z and two rotational axes) cryogenic manipulator (minimum sample temperature of 18 K) and a monochromatized X-ray source (Al Kα, 1486 eV) for static XPS measurements. An angle resolved time-of-flight (ARTOF 10K from VG-Scienta) electron spectrometer is currently being commissioned.

R3000 (VG-Scienta) electron spectrometer specifications:

  • high throughput lens
  • optimized transmission for high intensity in UPS, XPS
  • angular resolved modes: ±10°, ±7.5°, ±5°, ±3°
  • angular resolution: <0.1°
  • energy resolution: < 3 meV at 2 eV pass energy at 20 eV kinetic energy

ARTOF 10K (VG-Scienta) electron spectrometer specifications:

  • kinetic energy range up to 1000 eV
  • angular resolved modes: ±7°, ±15°
  • energy resolution: < 1 meV
  • angular resolution: <0.1°

The experimental chamber is also equipped with the following sample preparation/manipulation tools:

  • Ar sputtering
  • e-beam sample heating up to 1000°C
  • evaporators
  • cleaver

The time and angle resolved photoemission spectroscopy experimental chamber.

3. Ti:sapphire laser source

The HHG beamline is pumped by a Coherent Ti:Sa laser system operating at 800 nm (Micra Ti:Sa oscillator and a Legend Elite Duo two-stage amplifier), which provides 35 fs pulses with an energy of 3 mJ per pulse at a repetition rate of 5 kHz. By focusing such pulses, intensities on the order of 1016 W/cm2 can be reached, which is enough to generate high harmonics of the driving laser in gas.

The Coherent Ti:Sa laser system.

4. Optical parametric amplifier

Part of the light from the Ti:Sa laser system is used to pump an optical parametric amplifier (OPA), which can provide ultrashort pulses (~50 fs) tunable in the wavelength range from 230 nm to 2600 nm. Such pulses are used as a pump in a time-resolved photoemission spectroscopy setup.

OPA performance

Measured OPA energy per pulse for a pump pulse duration and energy of 40 fs and 0.92 mJ, respectively.

The OPerA Solo optical parametric amplifier providing tunable pulses for the pump-probe setup.

Ultima modifica il Lunedì, 12 Giugno 2017 15:23