DiProI Beamline Description 2015

The DiProI beamline and end station are currently under commissioning: the core capabilities of the beamline are already guaranteed, while significant improvements are scheduled for the years 2012 and 2013, including the achievement of shorter FEL wavelengths, better focalization on the sample and the installation of infrared and X-ray delay lines for pump & probe experiments.

DiProI Beamline layout

FEL photons are delivered to the DiProI end station through the PADReS section of the FERMI@Elettra FEL. A layout is sketched here.

PADReS provides characterization, manipulation and delivery of the FEL photons. The beam, spatially defined by Beam Defining Apertures and Beam Position Monitors, can be attenuated by Gas Absorbers; intensity, before and after attenuation, wavelenght and spectrum are monitored on-line, shot-to-shot, by non invasive Intensity Monitors and Energy Spectrometer. Along the beamline, the beam shape, position and intensity can be monitored by invasive devices such as a photodiode, a Bolometer, a YAG:Ce Scintillator; further attenuation is provided by two aluminum filters of 800 nm and 1200 nm thickness, respectively.

32.5 nm pulses observed at 10 Hz on a YAG:Ce

A system of Kirkpatrick-Baez (KB) mirrors focuses the beam on the sample inside the experimental chamber. Time resolved setups are provided by a split delay line for X-ray pulses (under commissioning) and a synchronized infrared pump line (under development).

Kirkpatrick-Baez (KB) focusing mirrors The FEL beam is focused on the sample of the DiProI experimental station by a set of two bendable planar-elliptical mirrors in Kirkpatrick-Baez (KB) configuration. A focal spot smaller than 10 x 10 μm2 have been achieved with wavelengths between 50 nm and 20 nm. An improvement of the bending system is expected to bring the focus size down to 3 x 5 μm2 (slope error 0.5 μrad), providing a flux of 1016 W/cm2 on the sample, for 100 fs pulses of 1012 photons at 5 nm wavelength.

Focus size and shape  Size and shape of the focus can be reconstructed by a wave front sensor and measured making indentations impinging with the FEL beam on a PMMA film. Wave front sensor reconstruction and optical microscope analysis confirmed that the current system provides a spot smaller than 10 x 10 μm2.