Recent results of PADReS, the Photon Analysis Delivery and REduction System, from the FERMI FEL commissioning and user operations

Abstract

The Photon Analysis Delivery and REduction System of FERMI (PADReS) has been routinely used during the machine commissioning and operations of FERMI since 2011. It has also served the needs of several user runs at the facility from late 2012. The system is endowed with online and shot-to-shot diagnostics giving information about intensity, spatial-angular distribution, spectral content, as well as other diagnostics to determine coherence, pulse length etc. Moreover, PADReS is capable of manipulating the beam in terms of intensity and optical parameters. Regarding the optics, besides a standard refocusing system based on an ellipsoidal mirror, the Kirkpatrick-Baez active optics systems are key elements and have been used intensively to meet users' requirements. A general description of the system is given, together with some selected results from the commissioning/operations/user beam time.

Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

“…FEL-2 is based on a double high gain harmonic generation (HGHG) conversion scheme wherein the first stage of the FEL serves as a pump for the second stage. The FEL beam was propagated along the Photon Analysis, Delivery, and Reduction System (PADReS), which includes shot-to-shot photon diagnostics (I0 monitor, PRESTO (Pulse-Resolved Energy Spectrometer (Transparent and Online))) and a gas attenuator (6 m, N2, 1.7 mbar) to remove the first stage FEL radiation [28]. The pulses were then passed through a 2 mm iris to attenuate off-axis emission and focused by an ellipsoidal mirror to a spot size of ~350 μm 2 .…”

PRESTO, the on-line photon energy spectrometer at FERMI: design, features and commissioning results

“…There is also the possibility to reduce the overall FEL intensity or to transmit almost only the third harmonic by using the gas absorber . The working principles of the various diagnostics as well as the commissioning results have already been explained in detail in previous papers (Zangrando et al, 2009(Zangrando et al, , 2014(Zangrando et al, , 2015. The location of the diagnostics is shown in Fig.…”

Experimental setups for FEL-based four-wave mixing experiments at FERMI

“…The mini-TIMER system does not have its own focusing optics, so that it requires an external focusing device. In particular, it is designed to be hosted by the DiProI experimental end-station (Capotondi et al, 2013(Capotondi et al, , 2015, equipped with a Kirkpatrick-Baez active optical system [KAOS (Raimondi et al, 2013;Zangrando et al, 2015)], but it can in principle be hosted by other experimental end-stations. The main limitation of this setup is the impossibility to generate and handle a third FEL beam (i.e.…”

“…3(d). The FEL beam exiting from the photon analysis, delivery and reduction system [PADReS (Zangrando et al, 2009(Zangrando et al, , 2015, not shown in Fig. 3(d)] is first split into two halves by a wavefront-division plane mirror [PM1, 2 grazing incidence, 260 mm  60 mm  50 mm (length  width  thickness), Au-coated] working in the vertical plane.…”