The detection of rapid dynamics in diverse physical systems is traditionally very difficult and strongly dominated by several noise contributions. Laser mode-locking, electron bunches in accelerators, and optical-triggered phases in materials are events that carry important information about the system from which they emerge. By detecting single-shot spectra with high repetition rates over long-time scales, new possibilities and applications to diagnose, control and tailor the spectral dynamics of lasers and electron beams in synchrotron and free-electron laser (FEL) accelerators open up. This contribution focuses on the latest developments of real-time, single-shot, high-repetition-rate detectors and data acquisition systems, with a special focus on emerging technologies and new possibilities in the diagnostics of rogue optical signals.
KEYWORDS: Analog electronics, Clocks, System on a chip, Field programmable gate arrays, Picosecond phenomena, Calibration, Terahertz radiation, Data conversion, Photodetectors, Electro optics
The detection of rapid dynamics in diverse physical systems is traditionally very difficult and strongly dominated by several noise contributions. Laser mode-locking, electron bunches in accelerators and optical-triggered phases in materials are events that carry important information about the system from which they emerge. To understand the underlying dynamics of complex systems often large numbers of single-shot measurements must be acquired continuously over a long time with extremely high temporal resolution. Ultrafast real-time instruments allow the acquisition of large data sets, even for rare events, in a relatively short time period. The real-time measurement of fast single-shot events with large record lengths is one of the most challenging problems in the fields of instrumentation and measurement. In this contribution, the novel ultra-fast and continuous data sampling system THERESA using photonic time-stretch is presented and its performance is discussed. The proposed data acquisition system is based on the latest ZYNQ Radio Frequency System on Chip (ZYNQ-RFSoC) family from Xilinx, which combines an array of fast (GS/s) multi-channel Analog-to-Digital Converters (ADCs) with a Field Programmable Gate Array (FPGA) and a multi-core ARM processor in a single heterogeneous programmable device. The stretched pulse is sampled in parallel by 16 wideband sampling channels operating in time-interleaving mode. The sampled data is transferred by a 100 Gb Ethernet data link to the Data Acquisition (DAQ) compute node for further analysis. The combination of both, the photonic time-stretch and the fast sampling system, is capable of sampling short pulses with femtosecond time resolution. Applications of the new system, hardware implementation and the commissioning of the first system for the electron bunch diagnostics are presented.
KEYWORDS: Sensors, Field programmable gate arrays, Free electron lasers, Data processing, Electronics, Silicon, Synchrotrons, Analog electronics, Data acquisition, Diagnostics
KALYPSO is a novel detector operating at line rates above 10 Mfps. The detector board holds a silicon or InGaAs linear array sensor with spectral sensitivity ranging from 400 nm to 2600 nm. The sensor is connected to a cutting-edge, custom designed, ASIC readout chip, which is responsible for the remarkable frame rate. The FPGA readout architecture enables continuous data acquisition and processing in real time. This detector is currently employed in many synchrotron facilities for beam diagnostics and for the characterization of self-built Ytterbium-doped fiber laser emitting around 1050 nm with a bandwidth of 40 nm.
A bottleneck for the investigation of electron beam dynamics in ring accelerators is a fast detection scheme coping with their high repetition rates in the MHz range. For example, at KARA (KArlsruhe Research Accelerator), the electron storage ring at the Karlsruhe Institute of Technology (KIT) in Germany, we showed that electro-optical methods enable single-shot detection of longitudinal electron bunch profiles by imprinting them onto chirped laser pulses. However, commercial cameras required to detect the spectra are typically limited to hundreds of kHz in readout speed. To tackle these challenges, we developed KALYPSO (KArlsruhe Linear array detector for MHz-rePetition rate SpectrOscopy), a linear detector array with a data acquisition system (DAQ) allowing high data-rates over long time scales. Due to a modular approach, various sensors (InGaAs and Si) can be used, so that KALYPSO can be adapted to different experiments with spectral regimes ranging from near-ultraviolet (NUV) to near-infrared (NIR). In this talk, we present recent results on studies of longitudinal and horizontal bunch profiles using KALYPSO. As an outlook, we give another example for MHz-range readout using KALYPSO, namely horizontal bunch profile diagnostics measuring the radiation emitted from a dispersive section in a storage ring. At the KARA visible light diagnostics (VLD) port the emitted radiation above 400 nm was previously recorded with a fast-gated camera. Here, limitations are the repetition rate in combination with the huge number of cycles during continuous measurements. To overcome these limitations, KALYPSO can repleace the fast-gated camera. Furthermore, due to the easy implementation of KALYPSO, we envision numerous applications for table-top experiments as well as for large-scale facilies.
KALYPSO is a novel detector operating at line rates above 10 Mfps. It consists of a detector board connected to FPGA based readout card for real time data processing. The detector board holds a Si or InGaAs linear array sensor, with spectral sensitivity ranging from 400 nm to 2600 nm, which is connected to a custom made front-end ASIC. A FPGA readout framework performs the real time data processing. In this contribution, we present the detector system, the readout electronics and the heterogeneous infrastructure for machine learning processing. The detector is currently in use at several synchrotron facilities for beam diagnostics as well as for single-pulse laser characterizations. Thanks to the shot-to-shot capability over long time scale, new attractive applications are open up for imaging in biological and medical research.
The photonic time-stretch technique allows electric field pulse shapes to be recorded with picosecond resolution, at megahertz acquisition rates. Using this strategy, we could directly record spatial patterns that spontaneously appear in relativistic electron bunches, and follow their dynamical evolution over time. We present recent results obtained using two strategies. At SOLEIL, we present the shapes of the THz pulses which are emitted by the structures, and detected far from the emission point, at the end of a beamline. At ANKA, we present how it has been possible to monitor directly the electron bunch near-field. These new types of single-shot recordings allow direct and stringent tests to be performed on electron bunch dynamical models in synchrotron radiation facilities.
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