R. Sergo - Academia.edu (original) (raw)
Papers by R. Sergo
Structural Dynamics, 2021
Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivit... more Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity Structural Dynamics 8, 034305 (2021);
Journal of Synchrotron Radiation, 2017
The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated ... more The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated to pump–probe experiments. Among others, the low-α mode operation is characterized by shorter pulse duration and represents the natural bridge between 50 ps synchrotron pulses and femtosecond experiments. Here, the capabilities in low-α mode of the experimental set-ups developed at the TEMPO beamline to perform pump–probe experiments with soft X-rays based on photoelectron or photon detection are presented. A 282 kHz repetition-rate femtosecond laser is synchronized with the synchrotron radiation time structure to induce fast electronic and/or magnetic excitations. Detection is performed using a two-dimensional space resolution plus time resolution detector based on microchannel plates equipped with a delay line. Results of time-resolved photoelectron spectroscopy, circular dichroism and magnetic scattering experiments are reported, and their respective advantages and limitations in the ...
Journal of synchrotron radiation, Jul 1, 2017
Complete photoemission experiments, enabling measurement of the full quantum set of the photoelec... more Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at t...
Damage to VUV, EUV, and X-Ray Optics II, 2009
The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the ... more The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the Sincrotrone Trieste laboratory in Trieste (Italy). It is a based on a seeded scheme that will provide an almost perfect transform limited beam and fully spatial coherent. It will cover the wavelength range from 100 to about 3 nm and in a short future down to
Adaptive X-Ray Optics II, 2012
ABSTRACT FERMI@Elettra is a VUV/Soft X-ray Free Electron Laser (FEL) user facility under commissi... more ABSTRACT FERMI@Elettra is a VUV/Soft X-ray Free Electron Laser (FEL) user facility under commissioning in Trieste, Italy. It provides a spatially coherent transform-limited photon beam in the sub-ps regime with high fluence and tunable wavelength. One of the FERMI beamlines, TIMEX, will be dedicated to the study of matter under extreme and metastable conditions, created and probed by the FEL radiation. Moreover, an active optics dedicated to perform the beam shaping at focus is needed in order to provide the necessary flat-top intensity distribution for heating the sample uniformly. In this work the principles of the beam shaping applied to the TIMEX beamline will be discussed as well as the adopted solution. Ray tracing simulations will be shown for theoretical mirror profiles as well as the metrological measurements with an interferometer and the Long Trace Profiler (LTP).
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2010
A new Free Electron Laser (FEL) user facility, named FERMI@Elettra, is under construction at Sinc... more A new Free Electron Laser (FEL) user facility, named FERMI@Elettra, is under construction at Sincrotrone Trieste (Italy). It is based on a seeded scheme to provide an almost perfect transform limited beam with fully spatial coherence. The wavelength range will be 100–3nm with fundamental and will go down to 1nm by using higher harmonics. It will be operative by autumn 2010.The exceptional characteristics of the source must be preserved until the experimental chamber, where a large set of different experiments will be performed. This condition poses very tight requirements to the design of the beamlines and, in particular, to the focusing optics. Here we will present the active optics system developed for Fermi but intended to be used also on the Elettra beamlines. It is based on the adoption of a hybrid active system composed by UHV compatible stepping motors and piezo ceramic actuators. These mirrors are supposed to provide focal distances from 0.8m to infinity with an angle of incidence up to a few degrees and residual shape errors below 10 or 5nm (depending on the wavelength). In this way it is possible to work with an almost perfect focused coherent beam as well as with a uniform defocused or unfocused image.The metrology results on the first 400mm long mirror will be shown and the actuator system described. A strain gauge assembly, calibrated in Elettra by means of a long trace profiler, and controlled by a custom made electronic system developed by us, is used as a direct in situ encoder.
SPIE Proceedings, 2000
abstract The diffraction gratings are widely used to monochromatize and even focus the soft X-ray... more abstract The diffraction gratings are widely used to monochromatize and even focus the soft X-ray radiation produced by the high brilliance third generation synchrotron radiation sources. Nevertheless, the final performance of an instrument that uses a diffraction ...
Review of Scientific Instruments, 1995
Abstract The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of... more Abstract The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of adsorbates on single crystal surfaces using soft x‐ray synchrotron radiation. It receives the light from an 81 period undulator with 5.6 cm period and 4.5 m length in the ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far an... more This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far and shows how the facility development has been driven by the new research frontier of ultra-fast, extreme ultraviolet and soft X-ray science. The commissioning phases and first experience with user pilot experiments are presented and discussed. ___________________________________________ *Work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3.
Synchrotron Radiation News, 1996
... Acknowledgement We would like to thank Riccardo Tommasini, Alberto Steindler, Paolo Pittana a... more ... Acknowledgement We would like to thank Riccardo Tommasini, Alberto Steindler, Paolo Pittana and Silvia Di Fonzo for helping to make this experiment a success. RP Walker, C. Bocchetta and their collabo-rators are thanked ...
2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2017
Time-resolved experiments often need detection devices able to provide information about position... more Time-resolved experiments often need detection devices able to provide information about position and arrival time of each detected event. Time resolution is a fundamental requirement for these devices, along with the high versatility and fast real-time computing of the acquisition system. Typical architectures, based on Time-to-Digital Converters (TDC) followed by a FPGA, combine very fast parallel computing with a time precision better than hundreds of picoseconds, allowing to perform state-of-the-art time-resolved experiments. Nevertheless, time resolution is still a limiting factor, in particular for imaging applications where the detector spatial resolution is determined through time measurement. Furthermore, the separation between the TDC devices and a readout FPGA has some drawbacks in terms of versatility of the system. In this article, we present a new approach, combining FPGA-based multi-channel Tapped-Delay-Line TDC and an efficient multipurpose readout logic, to greatly ...
2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2019
In many experiments involving detection of events, information is represented both by position an... more In many experiments involving detection of events, information is represented both by position and time of occurrence of the interaction. For the latter, the resolution is a primary demand that must remain compliant with global versatility and fast real-time computing of the system.At the basis of this kind of measurements are detectors providing at the same time X-Y position and the arrival time t of each detected event. Among these detectors, Cross Delay-Lines (CDL) detectors are one of the reference solutions and use the information of detection time also for determining the position of the event.The requests of precise time measurement and fast computing time-resolved experiments are nowadays fulfilled at best by the combination of Time-to-Digital Converter (TDC) architectures with spatial computing environment of Field Programmable Gate Array (FPGA) devices. Although very promising results have been achieved, time resolution necessary to imaging applications is still a serious ...
Time-resolved experiments often need detection devices able to provide information about position... more Time-resolved experiments often need detection devices able to provide information about position and arrival time of each detected event. Cross Delay-Lines detectors (CDL), which use arrival time information also for position detection, are the most suited instruments for this task and time resolution is a fundamental requirement, along with the high versatility and fast real-time computing. Typical acquisition architectures, based on Time-to-Digital Converters (TDC) followed by a Field Programmable Gate Array (FPGA), combine very fast parallel computing with a high time precision, allowing to perform state-of-the-art time-resolved experiments. In these devices, time precision as much as time accuracy are fundamental in order to guarantee a homogenous time-to-space conversion. Nevertheless, time resolution is still a limiting factor when time resolved experiments are associated to imaging.In 2017 at Nuclear Science Symposium, inside ″Development of fully FPGA-based 3D (X, Y, t) det...
A wide-band bunch-by-bunch Transverse Multi-Bunch Feedback, developed in collaboration with the S... more A wide-band bunch-by-bunch Transverse Multi-Bunch Feedback, developed in collaboration with the Swiss Light Source (SLS), has been installed at ELETTRA. After a description of the main hardware/software components, the first commissioning results and the present status of the system are given.
2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)
Time resolved experiments are among the most powerful tools in physic for exploring photoelectron... more Time resolved experiments are among the most powerful tools in physic for exploring photoelectron spectroscopy phenomena over time scales from milliseconds to picoseconds Moreover, acquisition systems with versatility and real-time computing are needed. Cross Delay-Lines detectors (CDL) are extremely suitable for these applications, since arrival time measurement is exploited to perform position detection, allowing to provide both information together. Typical architectures for acquisition systems are based on Aplication Specific Integrated Circuit (ASIC) Time-to-Digital Converters (TDCs) followed by a Field Programmable Logic Array (FPGA); fast parallel computing is combined with time precision, allowing to perform state-of-the-art time resolved experiments. Nevertheless, the limiting factor of this architecture is the absence of reconfigurability of the ASIC that strongly limits the customization respect to the requests of a specific set-up. Especially today, where the state-of-the-art TDCs implemented in FPGA, is comparable to the ASIC solutions. In 2019 Nuclear Science Symposium, we presented a fully-reconfigurable FPGA-based solution, where the TDC and the image reconstruction algorithm were hosted in two FPGAs. In particular, we focused on the 4-channel TDC that, guarantees high-performance in terms of resolution (1 ps), Full-Scale Range (200 µs), Integral Non Linearity, (4 ps over 500 ns), In this contribution, we give significant improvements in order to satisfy the aforementioned experimental experimental requests. In fact, the “pulse-to-pulse” dead-time of the TDC has been reduced from 20 ns to 7 ns, and the transmission rate between the FPGAs has been incremented from 10 to 100 Msps. Furthermore, we have increased the number of channels of the TDC from 4 to 8. This makes possible to correlate the CDL events with signals coming from other sources that can be as well Time-of-Fight or laser pulses as other CDL signals.
Journal of Instrumentation
X-ray computed micro-tomography (μCT) is one of the most advanced and common non-destructive tech... more X-ray computed micro-tomography (μCT) is one of the most advanced and common non-destructive techniques in the field of medical imaging and material science. It allows recreating virtual models (3D ...
Structural Dynamics, 2021
Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivit... more Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity Structural Dynamics 8, 034305 (2021);
Journal of Synchrotron Radiation, 2017
The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated ... more The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated to pump–probe experiments. Among others, the low-α mode operation is characterized by shorter pulse duration and represents the natural bridge between 50 ps synchrotron pulses and femtosecond experiments. Here, the capabilities in low-α mode of the experimental set-ups developed at the TEMPO beamline to perform pump–probe experiments with soft X-rays based on photoelectron or photon detection are presented. A 282 kHz repetition-rate femtosecond laser is synchronized with the synchrotron radiation time structure to induce fast electronic and/or magnetic excitations. Detection is performed using a two-dimensional space resolution plus time resolution detector based on microchannel plates equipped with a delay line. Results of time-resolved photoelectron spectroscopy, circular dichroism and magnetic scattering experiments are reported, and their respective advantages and limitations in the ...
Journal of synchrotron radiation, Jul 1, 2017
Complete photoemission experiments, enabling measurement of the full quantum set of the photoelec... more Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at t...
Damage to VUV, EUV, and X-Ray Optics II, 2009
The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the ... more The FERMI@Elettra free electron laser (FEL) user facility is currently under construction at the Sincrotrone Trieste laboratory in Trieste (Italy). It is a based on a seeded scheme that will provide an almost perfect transform limited beam and fully spatial coherent. It will cover the wavelength range from 100 to about 3 nm and in a short future down to
Adaptive X-Ray Optics II, 2012
ABSTRACT FERMI@Elettra is a VUV/Soft X-ray Free Electron Laser (FEL) user facility under commissi... more ABSTRACT FERMI@Elettra is a VUV/Soft X-ray Free Electron Laser (FEL) user facility under commissioning in Trieste, Italy. It provides a spatially coherent transform-limited photon beam in the sub-ps regime with high fluence and tunable wavelength. One of the FERMI beamlines, TIMEX, will be dedicated to the study of matter under extreme and metastable conditions, created and probed by the FEL radiation. Moreover, an active optics dedicated to perform the beam shaping at focus is needed in order to provide the necessary flat-top intensity distribution for heating the sample uniformly. In this work the principles of the beam shaping applied to the TIMEX beamline will be discussed as well as the adopted solution. Ray tracing simulations will be shown for theoretical mirror profiles as well as the metrological measurements with an interferometer and the Long Trace Profiler (LTP).
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2010
A new Free Electron Laser (FEL) user facility, named FERMI@Elettra, is under construction at Sinc... more A new Free Electron Laser (FEL) user facility, named FERMI@Elettra, is under construction at Sincrotrone Trieste (Italy). It is based on a seeded scheme to provide an almost perfect transform limited beam with fully spatial coherence. The wavelength range will be 100–3nm with fundamental and will go down to 1nm by using higher harmonics. It will be operative by autumn 2010.The exceptional characteristics of the source must be preserved until the experimental chamber, where a large set of different experiments will be performed. This condition poses very tight requirements to the design of the beamlines and, in particular, to the focusing optics. Here we will present the active optics system developed for Fermi but intended to be used also on the Elettra beamlines. It is based on the adoption of a hybrid active system composed by UHV compatible stepping motors and piezo ceramic actuators. These mirrors are supposed to provide focal distances from 0.8m to infinity with an angle of incidence up to a few degrees and residual shape errors below 10 or 5nm (depending on the wavelength). In this way it is possible to work with an almost perfect focused coherent beam as well as with a uniform defocused or unfocused image.The metrology results on the first 400mm long mirror will be shown and the actuator system described. A strain gauge assembly, calibrated in Elettra by means of a long trace profiler, and controlled by a custom made electronic system developed by us, is used as a direct in situ encoder.
SPIE Proceedings, 2000
abstract The diffraction gratings are widely used to monochromatize and even focus the soft X-ray... more abstract The diffraction gratings are widely used to monochromatize and even focus the soft X-ray radiation produced by the high brilliance third generation synchrotron radiation sources. Nevertheless, the final performance of an instrument that uses a diffraction ...
Review of Scientific Instruments, 1995
Abstract The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of... more Abstract The Super‐ESCA beamline has been designed for high resolution core level spectroscopy of adsorbates on single crystal surfaces using soft x‐ray synchrotron radiation. It receives the light from an 81 period undulator with 5.6 cm period and 4.5 m length in the ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far an... more This article describes the design goals of FERMI@Elettra, reports on the goals achieved so far and shows how the facility development has been driven by the new research frontier of ultra-fast, extreme ultraviolet and soft X-ray science. The commissioning phases and first experience with user pilot experiments are presented and discussed. ___________________________________________ *Work was supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3.
Synchrotron Radiation News, 1996
... Acknowledgement We would like to thank Riccardo Tommasini, Alberto Steindler, Paolo Pittana a... more ... Acknowledgement We would like to thank Riccardo Tommasini, Alberto Steindler, Paolo Pittana and Silvia Di Fonzo for helping to make this experiment a success. RP Walker, C. Bocchetta and their collabo-rators are thanked ...
2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2017
Time-resolved experiments often need detection devices able to provide information about position... more Time-resolved experiments often need detection devices able to provide information about position and arrival time of each detected event. Time resolution is a fundamental requirement for these devices, along with the high versatility and fast real-time computing of the acquisition system. Typical architectures, based on Time-to-Digital Converters (TDC) followed by a FPGA, combine very fast parallel computing with a time precision better than hundreds of picoseconds, allowing to perform state-of-the-art time-resolved experiments. Nevertheless, time resolution is still a limiting factor, in particular for imaging applications where the detector spatial resolution is determined through time measurement. Furthermore, the separation between the TDC devices and a readout FPGA has some drawbacks in terms of versatility of the system. In this article, we present a new approach, combining FPGA-based multi-channel Tapped-Delay-Line TDC and an efficient multipurpose readout logic, to greatly ...
2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2019
In many experiments involving detection of events, information is represented both by position an... more In many experiments involving detection of events, information is represented both by position and time of occurrence of the interaction. For the latter, the resolution is a primary demand that must remain compliant with global versatility and fast real-time computing of the system.At the basis of this kind of measurements are detectors providing at the same time X-Y position and the arrival time t of each detected event. Among these detectors, Cross Delay-Lines (CDL) detectors are one of the reference solutions and use the information of detection time also for determining the position of the event.The requests of precise time measurement and fast computing time-resolved experiments are nowadays fulfilled at best by the combination of Time-to-Digital Converter (TDC) architectures with spatial computing environment of Field Programmable Gate Array (FPGA) devices. Although very promising results have been achieved, time resolution necessary to imaging applications is still a serious ...
Time-resolved experiments often need detection devices able to provide information about position... more Time-resolved experiments often need detection devices able to provide information about position and arrival time of each detected event. Cross Delay-Lines detectors (CDL), which use arrival time information also for position detection, are the most suited instruments for this task and time resolution is a fundamental requirement, along with the high versatility and fast real-time computing. Typical acquisition architectures, based on Time-to-Digital Converters (TDC) followed by a Field Programmable Gate Array (FPGA), combine very fast parallel computing with a high time precision, allowing to perform state-of-the-art time-resolved experiments. In these devices, time precision as much as time accuracy are fundamental in order to guarantee a homogenous time-to-space conversion. Nevertheless, time resolution is still a limiting factor when time resolved experiments are associated to imaging.In 2017 at Nuclear Science Symposium, inside ″Development of fully FPGA-based 3D (X, Y, t) det...
A wide-band bunch-by-bunch Transverse Multi-Bunch Feedback, developed in collaboration with the S... more A wide-band bunch-by-bunch Transverse Multi-Bunch Feedback, developed in collaboration with the Swiss Light Source (SLS), has been installed at ELETTRA. After a description of the main hardware/software components, the first commissioning results and the present status of the system are given.
2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)
Time resolved experiments are among the most powerful tools in physic for exploring photoelectron... more Time resolved experiments are among the most powerful tools in physic for exploring photoelectron spectroscopy phenomena over time scales from milliseconds to picoseconds Moreover, acquisition systems with versatility and real-time computing are needed. Cross Delay-Lines detectors (CDL) are extremely suitable for these applications, since arrival time measurement is exploited to perform position detection, allowing to provide both information together. Typical architectures for acquisition systems are based on Aplication Specific Integrated Circuit (ASIC) Time-to-Digital Converters (TDCs) followed by a Field Programmable Logic Array (FPGA); fast parallel computing is combined with time precision, allowing to perform state-of-the-art time resolved experiments. Nevertheless, the limiting factor of this architecture is the absence of reconfigurability of the ASIC that strongly limits the customization respect to the requests of a specific set-up. Especially today, where the state-of-the-art TDCs implemented in FPGA, is comparable to the ASIC solutions. In 2019 Nuclear Science Symposium, we presented a fully-reconfigurable FPGA-based solution, where the TDC and the image reconstruction algorithm were hosted in two FPGAs. In particular, we focused on the 4-channel TDC that, guarantees high-performance in terms of resolution (1 ps), Full-Scale Range (200 µs), Integral Non Linearity, (4 ps over 500 ns), In this contribution, we give significant improvements in order to satisfy the aforementioned experimental experimental requests. In fact, the “pulse-to-pulse” dead-time of the TDC has been reduced from 20 ns to 7 ns, and the transmission rate between the FPGAs has been incremented from 10 to 100 Msps. Furthermore, we have increased the number of channels of the TDC from 4 to 8. This makes possible to correlate the CDL events with signals coming from other sources that can be as well Time-of-Fight or laser pulses as other CDL signals.
Journal of Instrumentation
X-ray computed micro-tomography (μCT) is one of the most advanced and common non-destructive tech... more X-ray computed micro-tomography (μCT) is one of the most advanced and common non-destructive techniques in the field of medical imaging and material science. It allows recreating virtual models (3D ...