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BL20 - LOREA

ANGLE RESOLVED PHOTOEMISSION SPECTROSCOPY (ARPES)

ALBA BEAMLINES

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DESCRIPTION

LOREA is a beamline specified for the investigation of electronic structure of solids by means of Angle Resolved Photo-Emission Spectroscopy (ARPES). The beamline operates in the photon energy range 10-1000 eV with tunable linear and circular polarizations produced by an APPLE II helical undulator. Thanks to the energy range and the high photon flux, LOREA is suitable for high resolution VUV ARPES investigations in the 10-200 eV range, while it is feasible to extend the ARPES measurements in the 200-600 eV energy range (soft X-ray ARPES). In addition, core level photoemission, resonant photoemission and X-ray absorption spectroscopies will be accessible in the whole energy range. In a forthcoming upgrade, LOREA will be equipped with a spin-detector to perform spin-resolved ARPES (SR-ARPES) experiments.

IM_LOREAStaff

Massimo Tallarida (beamline responsible, right) with the former collaborators: Debora Pierucci (now at C2N-CNRS / Université Paris-Saclay, left) and Federico Bisti (now at University of L’Aquila, center)

 

STATUS

LOREA is fully operational. First official users arrived in October 2021.

Commissioning with first light on M1 was started in July 2020

IM_Status LOREA-1

The rising sun of LOREA undulator: on the left the image shows the contribution of the bending magnet downstream the undulator (completely open, with gap=300mm). As the gap of the undulator is reduced, the more intense spot of the radiation originated by the LOREA undulator increases in intensity (center, for gap=200mm, and right for gap=180mm)

 

TECHNICAL SPECIFICATIONS 

Photon energy range 10-1000 eV
Polarization Variable (left- and right-handed circular, linear horizontal and vertical)
Resolving power >  104 in the whole range
Photon flux

   1013 ph/s/0.1%BW @ hν = 10-350 eV 

> 1012 ph/s/0.1%BW @ hν = 350 - 1000 eV

Beam spot size at sample position (V×H)   ̴ 13 × 13 µm@ hν = 30 eV

 

SOURCE

The source is a pure permanent magnet APPLE II helical undulator, designed by the ID group of ALBA and produced by Kyma S.r.l. . It is capable of delivering linearly polarized light (vertical and horizontal), as well as circularly-polarized light (left- or right-handed). 

ParameterValue
Period 125 mm
Number of periods 16
Minimum gap

13.0 mm

Max Bx [T]

Linear H: 0.0000

Linear V:1.0594

Circular: 0.7734

Max By [T]

Linear H: 13.3095

Linear V: 0.0000

Circular: 9.0296

 

OPTICS LAYOUT

IM_LOREAOpticsLayout

Schematic view of the optical layout of the LOREA beamline.

 

The first optical element inside the optical hutch is a flat mirror (M1). It is internally cooled with water to reduce the surface deformation due to the heating. The following element is in the experimental hall and it is the monochromator (green square), which includes three switchable spherical mirrors (SM), and four varied-line-spacing (VLS) plane. Downstream the monochromator there is a plano-elliptic mirror (M3), which focuses the source horizontally at a plane placed 0.5 m upstream of the exit slit. The beam is vertically focused by the monochromator mirrors at the exit slit plane. Finally, a Kirkpatrick-Baez (KB) mirrors pair (blue square, with one vertically deflecting mirror, VFM, and one horizontally deflecting mirror, HFM, both with a plano-elliptic figure) refocuses the beam on the sample.

IM_LOREA beamline layout

Beamline layout

 

ENDSTATION

The end station will be composed by a central radial distribution chamber to which all other vessels are connected, including chambers for: ARPES analysis, with auxiliary chamber for sample preparation on 6-axes manipulator; in situ UHV deposition with “physical” methods (sputtering, evaporation, oxidation) and characterization with LEED; high pressure deposition (Chemical Vapor Deposition, CVD, and Atomic Layer Deposition, ALD); organic molecule deposition; sample storage; docking of vacuum suitcases; docking of STM; and fast entry load lock. An upgrade of the system, including a spin detector and an STM, is planned.

IM_LOREA endstation layout

Endstation layout.