Search

The compact and versatile linear accelerator-based test facility FLUTE (Ferninfrarot Linac- Und Test-Experiment) is operated at KIT. Its primary goal is to serve as a platform for a variety of accelerator R\ studies like the generation of strong ultra-short terahertz pulses. The amplitude of the generated coherent THz pulses is proportional to the square number of particles in the bunch. With the transverse emittance a measure for the transverse particle density can be determined. It is therefore a vital parameter in the optimization for operation. In a systematic study, the transverse emittance of the electron beam was measured in the FLUTE injector. A detailed analysis considers different influences such as the bunch charge and compares this with particle tracking simulations carried out with ASTRA. In this contribution, the key findings of this analysis are discussed., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Two parallel corrugated plates will be installed at the KIT storage ring KARA (KArlsruhe Research Accelerator). This impedance manipulation structure will be used to study and eventually control the beam dynamics and the emitted coherent synchrotron radiation (CSR). In this contribution, we present the results obtained with the Vlasov-Fokker-Planck solver Inovesa showing the impedance impact of different corrugated structures on the bunch and its emitted CSR power., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

To generate the electrons to be accelerated, a photoinjection laser is used at the linac-based test facility FLUTE (Ferninfrarot Linac- Und Test Experiment) at the Karlsruhe Institute of Technology (KIT). The properties of the laser pulse, such as intensity, laser spot size or temporal profile, are the first parameters to influence the characteristics of the electron bunches. In order to control the initial parameters of the electrons in the most flexible way possible, the laser optics at FLUTE are therefore supplemented by additional setups that allow transverse and longitudinal laser pulse shaping by using so-called Spatial Light Modulators (SLMs). In the future, the control of the SLMs will be integrated into a Machine Learning (ML) supported feedback system for the optimization of the electron bunch properties. In this contribution the first test experiments and results on laser pulse shaping at FLUTE on the way to this project are presented., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

For measuring the temporal profile of the coherent synchrotron radiation (CSR) at the KIT storage ring KARA (Karlsruhe Research Accelerator) an experimental setup based on electro-optical spectral decoding (EOSD) is currently being implemented. The EOSD technique allows single-shot, phase-sensitive measurements of the far-field radiation on a turn-by-turn basis at rates in the MHz range. Therefore, the resulting THz radiation from the dynamics of the bunch evolution, e.g. the microbunching, can be observed with high temporal resolution. This far-field setup is part of the distributed sensor network at KARA. Additionally to the information acquired from the near-field EOSD spectral decoding and the horizontal bunch profile monitor, it enables to monitor the longitudinal phase-space of the bunch. In this contribution, the characterization of the far-field setup is summarized and its implementation is discussed., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R An example for a new accelerator diagnostics tool currently studied at FLUTE is the split-ring-resonator (SRR) experiment, which aims to measure the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Particles passing through the SRR gap are time-dependently deflected in the vertical plane, which allows a vertical streaking of an electron bunch. This principle allows a diagnosis of the longitudinal bunch profile in the femtosecond time domain and will be tested at FLUTE. This contribution presents an overview of the SRR experiment and the results of various tracking simulations for different scenarios as a function of laser pulse length and bunch charge. Based on these results possible working points for the experiments at FLUTE will be proposed., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

FLUTE (Ferninfrarot Linac- und Test-Experiment) at KIT is a compact linac-based test facility for novel accelerator technology and a source of intense THz radiation. FLUTE is designed to provide a wide range of electron bunch charges from the pC- to nC-range, high electric fields up to 1.2 GV/m, and ultra-short THz pulses down to the fs-timescale. The electrons are generated at the RF photoinjector, where the electron gun is driven by a commercial titanium sapphire laser. In this kind of setup the electron beam properties are determined by the photoinjector, but more importantly by the characteristics of the laser pulses. Spatial light modulators can be used to transversely and longitudinally shape the laser pulse, offering a flexible way to shape the laser beam and subsequently the electron beam, influencing the produced THz pulses. However, nonlinear effects inherent to the laser manipulation (transportation, compression, third harmonic generation) can distort the original pulse. In this paper we propose to use machine learning methods to manipulate the laser and electron bunch, aiming to generate tailor-made THz pulses. The method is demonstrated experimentally in a test setup., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

A very common bottleneck to study short electron bunch dynamics in accelerators is a detection scheme that can deal with high repetition rates in the MHz range. The KIT electron storage ring KARA (Karlsruhe Research Accelerator) is the first storage ring with a near-field single-shot electro-optical (EO) bunch profile monitor installed for the measurement of electron bunch dynamics in the longitudinal phase-space. Using electro-optical spectral decoding (EOSD) it is possible to imprint the bunch profile on chirped laser pulses subsequently read out by a spectrometer and a camera. However, commercially available cameras have a drawback in their acquisition rate, which is limited to a few hundred kHz. Hence, we have developed KALYPSO, an ultra-fast line camera capable of operating in the MHz regime. Its modular approach allows the installation of several sensors e.g. Si, InGaAs, PbS, PbSe to cover a wide range of spectral sensitivities. In this contribution, an overview of the EOSD experimental setup and the detector system installed for longitudinal bunch studies will be presented., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

KALYPSO is a novel detector capable of operating at frame rates up to 12 MHz developed and tested at the institute of data processing and electronics (IPE) and employed at Karlsruhe Research Accelerator (KARA) which is part of the Test Facility and Synchrotron Radiation Source KIT. This detector consists of silicon, InGaAs, PbS, or PbSe line array sensor with spectral sensitivity from 350 nm to 5000 nm. The unprecedented frame rate of this detector is achieved by a custom-designed ASIC readout chip. The FPGA-readout architecture enables continuous data acquisition and real-time data processing. Such a detector has various applications in the fields of beam diagnostics and spectral analysis. KALYPSO is currently employed at various synchrotron facilities for electro-optical spectral decoding (EOSD) to study the longitudinal profile of the electron beam, to study the energy spread of the electron beam, tuning of free-electron lasers (FELs), and also in characterizing laser spectra. This contribution will present an overview of the results from the mentioned applications., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

FLUTE (Ferninfrarot Linac- und Test-Experiment) is a compact linac-based test facility for accelerator R and source of intense THz radiation for photon science. In preparation for the next experiments, the electron beam of the injector section of FLUTE has been characterized. In systematic studies the electron beam parameters, e.g., beam energy and emittance, are measured with several diagnostic systems. This knowledge allows the establishment of different operation settings and the optimization of electron beam parameters for future experiments., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The Ferninfrarot Linac- Und Test-Experiment (FLUTE) is a KIT-operated linac-based test facility for accelerator research and development as well as a compact, ultra-broadband and short-pulse terahertz (THz) source. As a key component of FLUTE, the bunch compressor (chicane) consisting of four specially designed dipoles will be used to compress the 40-50 MeV electron bunches after the linac down to single fs bunch length. The maximum vertical magnetic field of the dipoles reach 0.22 T, with an effective length of 200 mm. The good field region is ±40 mm and ±10.5 mm in the horizontal and vertical direction, respectively. The latest measurement results of the dipoles in terms of field homogeneity, excitation and field reproducibility within the good field regions will be reported, which meet the predefined specifications. The measured 3D magnetic field distributions have been used to perform beam dynamics simulations of the bunch compressor. Effects of the real field properties on the beam dynamics, which are different from that of the ASTRA built-in dipole field, will be discussed., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Synchrotron light sources operate with bunch repetition rates in the MHz regime. The longitudinal and transverse beam dynamics of these electron bunches can be investigated and characterized by experiments employing linear array detectors. To improve the performance of modern beam diagnostics and overcome the limitations of commercially available detectors, we have at KIT developed KALYPSO, a detector system operating with an unprecedented frame rate of up to 12 MHz. To facilitate the integration in different experiments, a modular architecture has been utilized. Different semiconductor microstrip sensors based on Si, InGaAs, PbS, and PbSe can be connected to the custom-designed low noise front-end ASIC to optimize the quantum efficiency at different photon energies, ranging from near-UV, visible, and up to near-IR. The front-end electronics are integrated within a heterogeneous DAQ consisting of FPGAs and GPUs, which allows the implementation of real-time data processing. This detector is currently installed at KARA, European XFEL, FLASH, Soleil, DELTA. In this contribution, we present the detector architecture, the performance results, and the ongoing technical developments., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

KARA, the Karlsruhe Research Accelerator, can be operated in different modes, including a short-bunch mode. During this mode, where the dispersion is stretched in order to reduce the momentum-compaction factor, micro-bunching instability can occur. At KARA, several measurement setups and techniques are used to investigate this instability further with the long-term perspective to suppress and control it. In this contribution, we give an overview about the different setups and the results achieved during the past years.

Scientific reports 13(1), 4618 (2023). doi:10.1038/s41598-023-31196-5, The description of physical processes with many-particle systems is a key approach to the modeling of numerous physical systems. For example in storage rings, where ultrarelativistic particles are agglomerated in dense bunches, the modeling and measurement of their phase-space distribution is of paramount importance: at any time the phase-space distribution not only determines the complete space-time evolution but also provides fundamental performance characteristics for storage ring operation. Here, we demonstrate a non-destructive tomographic imaging technique for the 2D longitudinal phase-space distribution of ultrarelativistic electron bunches. For this purpose, we utilize a unique setup, which streams turn-by-turn near-field measurements of bunch profiles at MHz repetition rates. To demonstrate the feasibility of our method, we induce a non-equilibrium state and show that the phase-space distribution microstructuring as well as the phase-space distribution dynamics can be observed in great detail. Our approach offers a pathway to control ultrashort bunches and supports, as one example, the development of compact accelerators with low energy footprints., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

In recent and future synchrotron radiation facilities, relativistic electron bunches with increasingly high charge density are needed for producing brilliant light at various wavelengths, from X-rays to terahertz. In such conditions, interaction of electrons bunches with their own emitted electromagnetic fields leads to instabilities and spontaneous formation of complex spatial structures. Understanding these instabilities is therefore key in most electron accelerators. However, investigations suffer from the lack of non-destructive recording tools for electron bunch shapes. In storage rings, most studies thus focus on the resulting emitted radiation. Here, we present measurements of the electric field in the immediate vicinity of the electron bunch in a storage ring, over many turns. For recording the ultrafast electric field, we designed a photonic time-stretch analog-to-digital converter with terasamples/second acquisition rate. We could thus observe the predicted link between spontaneous pattern formation and giant bursts of coherent synchrotron radiation in a storage ring., 9 pages, 5 figures

FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact versatile linear accelerator at the Karlsruhe Institute of Technology (KIT). It serves as a platform for a variety of accelerator studies as well as a source of strong ultra-short THz pulses for photon science. In the commissioning phase of the 7 MeV low energy section the electron bunches are used to test the different diagnostics systems installed in this section. An example is the split-ring-resonator-experiment. In this contribution we report on the commissioning status of the beam diagnostics and present first beam measurements at FLUTE., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The microbunching instability is a longitudinal collective instability which occurs for short electron bunches in a storage ring above a certain threshold current. The instability leads to a charge modulation in the longitudinal phase space. The resulting substructures on the longitudinal bunch profile vary over time and lead to fluctuations in the emitted power of coherent synchrotron radiation (CSR). To study the underlying longitudinal dynamics on a turn-by-turn basis, the KIT storage ring KARA (Karlsruhe Research Accelerator) provides a wide variety of diagnostic systems. By synchronizing the single-shot electro-optical spectral decoding setup (longitudinal profile), the bunch-by-bunch THz detection systems (THz power) and the horizontal bunch size measurement setup (energy spread), three important properties of the bunch during this instability can be measured at every turn for long time scales. This allows a deep insight into the dynamics of the bunch under the influence of the microbunching instability. This contribution will discuss effects like the connection between the emitted CSR power and the deformations in the longitudinal bunch profile on the time scale of the instability., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Accelerators with high bunch-repetition rates mandate high-throughput detector electronics to diagnose each individual bunch. KALYPSO with a 256-pixel detector line-array integrated in an fs laser-based electro-optical set-up allows longitudinal bunch profiling with sub-ps resolution as demonstrated at the storage ring ANKA for single-bunch mode operation at 2.7 MHz and also at the Eu-XFEL with a 4.5-MHz micro-bunch train. Improvements will enhance fs-time accuracy, reduce noise, and increase frame-rate. A custom front-end with an application-specific integrated circuit (ASIC) has been developed to operate with 10-MHz frame-rates at low noise. Several linear arrays with up to 1024 pixel and smaller pixel pitch were submitted for production. The development of a low-gain avalanche diode (LGAD) sensor will further improve the time resolution. Detector data is transmitted in the DAQ framework to external GPU-based clusters and processed in real-time at 7 Gbytes/s with a few μs latency. For beam dynamics studies we also develop KAPTURE capable to analyze terahertz detector pulses at GHz-repetition rates. These developments open new windows in beam diagnostics of modern accelerators., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

While recent diffraction-limited storage rings provide bunches with transverse dimensions smaller than the wavelength of the observed synchrotron radiation, the bunch compression in the longitudinal plane is still challenging. The benefit would be single cycle pulses of coherent radiation with many orders of magnitude higher intensity. However, the self-interaction of a short electron bunch with its emitted coherent radiation can lead to micro-bunching instabilities. This effect limits the bunch compression in storage rings currently to the picosecond range. In that range, the bunches emit coherent THz radiation corresponding to their bunch length. In this paper, new measurement setups developed at the Karlsruhe Institute of Technology are described for systematic turn-by-turn investigations of the micro-bunching instability. They lead to a better understanding thereof and enable appropriate observation methods in future efforts of controlling and mastering the instability. Furthermore, the described setups might also be used as high repetition rate bunch compression monitors for bunches of picosecond length and below., Proceedings of the 60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources, FLS2018, Shanghai, China

The development of fast detection methods for comprehensive monitoring of electron bunches is a prerequisite to gain comprehensive control over the synchrontron emission in storage rings with their MHz repetition rate. Here, we present a proof-of-principle experiment with at detailed description of our implementation to detect the longitudinal electron bunch profiles via single-shot, near-field electro-optical sampling at the Karlsruhe Research Accelerator (KARA). Our experiment is equipped with an ultra-fast line array camera providing a high-throughput MHz data stream. We characterize statistical properties of the obtained data set and give a detailed description for the data processing as well as for the calculation of the charge density profiles, which where measured in the short-bunch operation mode of KARA. Finally, we discuss properties of the bunch profile dynamics on a coarse-grained level on the example of the well-known synchrotron oscillation., Comment: 8 pages, 5 figures

High repetition rate diagnostics are required when detecting single-shot electro-optical (EO) bunch profiles. The KIT storage ring KARA (KArlsruhe Research Accelerator) is the first storage ring in the world that has a near-field EO bunch-profile monitor in operation. By imprinting longitudinal electron bunch profiles onto chirped laser pulses, single-shot detection is feasible. However, limitations of available detection systems are challenging: The constraints are either given by the repetition rate or the duration of the consecutive acquisitions. Two strategies can overcome these limitations: Based on the photonic time-stretch method, the ps laser pulses can be stretched to the ns range using km long fibers. The readout with a high-bandwidth oscilloscope then enables a single-shot detection at high repetition rates. The other strategy is the development of dedicated ultra-fast photodetector arrays allowing direct detection of the ps pulses at MHz repetition rates. We developed KALYPSO, a linear detector array with a DAQ allowing to record high data-rates over long time scales. Here, we present recent results of studies of the longitudinal electron bunch dynamics using KALYPSO., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

FLUTE (Ferninfrarot Linac- Und Test-Experiment) will be a new compact versatile linear accelerator at KIT. Its primary goal is to serve as a platform for a variety of accelerator studies as well as to generate strong ultra-short THz pulses for photon science. The machine consists of an RF gun, a traveling wave linac and a D-shaped bunch compressor chicane with corresponding diagnostics sections. In this contribution, we report on the latest developments of the diagnostics components. An overview of the readout and control system integration will be given., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Recently, a new setup for measuring the beam energy spread has been commissioned at the ANKA storage ring at the Karlsruhe Institute of Technology. This setup is based on a fast-gated intensified camera and detects the horizontal profiles of individual bunches in a multi-bunch environment on a single-turn base. As the radiation source point is located in a dispersive section of the storage ring, this allows time-resolved studies of the energy spread. These studies are of particular interest in the framework of short-bunch beam dynamics and the characterization of instabilities. The system is fully synchronized to other beam diagnostics devices allocated in various places along the storage ring, such as the single-shot electro-optical spectral decoding setup or the turn-by-turn terahertz detection systems. Here we discuss the results of the synchronous measurements with the various systems with special emphasis on the energy spread studies., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The acquisition rate of commercially available line array detectors is a bottleneck for beam diagnostics at high-repetition rate machines like synchrotron lightsources or FELs with a quasi-continuous or macro-pulse operation. In order to remove this bottleneck we have developed KALYPSO, an ultra-fast linear array detector operating at a frame-rate of up to 2.7 Mfps. The KALYPSO detector mounts InGaAs or Si linear array sensors to measure radiation in the near-infrared or visible spectrum. The FPGA-based read-out card can be connected to an external data acquisition system through a high-performance PCI-Express 3.0 data-link, allowing continuous data taking and real-time data analysis. The detector is fully synchronized with the timing system of the accelerator and other diagnostic instruments. The detector is currently installed at several accelerators: ANKA, the European XFEL and TELBE. We present the detector and the results obtained with Electro-Optical Spectral Decoding (EOSD) setups., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

The ANKA storage ring offers different operation modes including the short-bunch mode with bunch lengths tuned down to a few picoseconds. This can lead to the occurrence of micro-bunching instabilities coupled to the emission of coherent synchrotron radiation (CSR) in so-called 'bursts'. To study this CSR instability we use several turn-by-turn enabled detector systems to synchronously measure both the THz signal as well as bunch profiles. The different detectors are placed at different locations around the storage ring. Here we discuss the experimental setup and calibration of the various systems' synchronisation., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The accelerator test facility FLUTE (Ferninfrarot Linac Und Test Experiment) will allow research and development in electron accelerator technology as well as photon science. Electron bunches of durations in the femtosecond range will be provided to generate intense THz radiation. Start-to-end simulation of the accelerator has been performed with the bunch length as the optimization objective. Based on the resulting charge distribution the expected THz field properties can be calculated. In this paper we combine the two tools and present first results., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

An electron energy measurement setup based on the detection of Compton backscattered photons, generated by laser light scattered off the relativistic electron beam, has been proposed and developed for operation at the ANKA storage ring of the Karlsruhe Institute of Technology (KIT). In contrast to conventional methods based on head-on collisions, the setup at ANKA is, for the first time, realized in a transverse configuration where the laser beam hits the electron beam at an angle of ~90°. This makes it possible to achieve a relatively low-cost and very compact setup since it only requires a small side-port instead of a straight section. This development could benefit storage rings with restricted space or where no straight sections are available, for example due to interferences with existing beamlines. The setup and the first measurement results are presented in the paper., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

At KIT we are currently constructing the compact linear accelerator FLUTE (Ferninfrarot Linac Und Test Experiment). This 41 MeV machine is aimed at accelerator physics and synchrotron radiation research, using ultra-short electron bunches. The electrons are generated at a photo-cathode using picosecond long UV laser pulses. A magnetic chicane is used to compress the bunches longitudinally to a few femtoseconds. This contribution describes both the magnet design, in particular the optimization of the chicane dipoles based on finite element method (FEM) simulations, as well as the implementation of a magnet measurement system., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

FLUTE, a new linac-based test facility and THz source is currently being built at the Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. It consists of an RF photo gun and a traveling wave linac accelerating electrons to beam energies of ~41 MeV in the charge range from a few pC up to 3 nC. The electron bunch will then be compressed in a magnetic chicane in the range of 1 - 300 fs, depending on the charge, in order to generate coherent THz radiation with high peak power. An overview of the simulation and hardware status is given in this contribution., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

A new compact linear accelerator FLUTE is currently under construction at Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. It aims at obtaining femtosecond electron bunches (~1fs - 300 fs) with a wide charge range (1 pC - 3 nC) and requires a precise bunch length diagnostic system. Here we present the layout of a bunch length monitor based on the electro-optic technique of spectral decoding using an Yb-doped fiber laser system (central wavelength 1030 nm) and a GaP crystal. Simulations of the electro-optic signal for different operation modes of FLUTE were performed and main challenges are discussed in this talk. This work is funded by the European Union under contract PITN-GA-2011-289191, Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Time-resolved electron diagnostics with ultra-high temporal resolution is increasingly required by the state-of-the-art accelerators. Strong terahertz (THz) fields, excited in a split ring resonator (SRR), have been recently proposed to streak electron bunches for their temporal characterisation. Thanks to the high amplitude and frequency of the THz field, temporal resolution down to the sub-femtosecond range can be expected. We are planning a proof-of-principle experiment of the SRR time-resolved diagnostics at the accelerator test-facility FLUTE (Ferninfrarot Linac und Test Experiment) at the Karlsruhe Institute of Technology. The design of the experimental chamber has been finished and integrated into the design layout of the FLUTE accelerator. Beam dynamics simulations have been conducted to investigate and optimise the performance of the SRR diagnostics. In this paper, we present the design layout of the experimental setup and discuss the simulation results for the optimised parameters of the accelerator and the SRR structure., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

For electron accelerators, electro-optical methods in the near-field have been shown to be a powerful tool to detect longitudinal bunch profiles. In 2013, we demonstrated for the first time, electro-optical bunch profile measurements in a storage ring at the accelerator test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT). To study possible bunch-bunch interactions and its effects on the longitudinal dynamics, these measurements need to be performed in a multi-bunch environment. Up to now, due to long-ranging wake-fields the electro-optical monitoring was limited to single-bunch operation. Here, we present our new in-vacuum setup to overcome this limitation. First measurements show reduced wake-fields in particular around 2 ns, where the subsequent bunch can occur in a multi-bunch environment at ANKA., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

ANKA is the first storage ring in the world with a near-field single-shot electro-optical (EO) bunch profile monitor. The method of electro-optical spectral decoding (EOSD) uses the Pockels effect to modulate the longitudinal electron bunch profile onto a long, chirped laser pulse passing through an EO crystal. The laser pulse is then analyzed with a single-shot spectrometer and from the spectral modulation, the temporal modulation can be extracted. The setup has a sub-ps resolution (granularity) and can measure down to bunch lengths of 1.5 ps RMS for bunch charges as low as 30 pC. With this setup it is possible to study longitudinal beam dynamics (e. g. microbunching) occurring during ANKA's low-alpha-operation, an operation mode with compressed bunches to generate coherent synchrotron radiation in the THz range. In addition to measuring the longitudinal bunch profile, long-ranging wake-fields trailing the electron bunch can also be studied, revealing bunch-bunch interactions., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany