Author: Judin, V.
Paper Title Page
MOCZB1 A Picosecond Sampling Electronic “KAPTURE” for Terahertz Synchrotron Radiation 24
 
  • C.M. Caselle, M. Brosi, S.A. Chilingaryan, T. Dritschler, N. Hiller, V. Judin, A. Kopmann, A.-S. Müller, L. Petzold, J. Raasch, L. Rota, M. Siegel, N.J. Smale, J.L. Steinmann, M. Vogelgesang, M. Weber, S. Wuensch
    KIT, Karlsruhe, Germany
 
  For a few years, coherent synchrotron radiation (CSR) generated by short electron bunches has been provided at the ANKA light source. Electron bunches can be filled in up to 184 buckets with a distance between two adjacent bunches of 2 ns corresponding to the RF system frequency of 500 MHz. Arbitrary filling patterns are generated to investigate the interaction of adjacent bunches in CSR. To study the THz emission characteristics over multiple revolutions superconducting YBa2Cu3O7−δ (YBCO) film detectors are used. The intrinsic response time of YBCO thin films is in the order of a few picoseconds only. For fast, continuous sampling of these individual ultra-short terahertz pulses, a novel digitizer system has been developed. The KAPTURE (KArlsruhe Pulse Taking Ultra-fast Readout Electronics) consists of a wideband low-noise amplifier, a picosecond pulse sampling card and a GByte transfer data link back-end readout card. High-end graphic processing units (GPUs) perform real-time data analysis. The KAPTURE system was successfully demonstrated for readout of the intensity fluctuations in the CSR at the ANKA Storage Ring detected in THz range. Four samples are recorded in parallel for each fast pulse with programmable sampling times in the range of 3 to 100 psec. A clean jitter phase locked loop (PLL) provides a clock signal with high temporal accuracy. The back-end card receives the 4 digital samples every 2 ns with 12 bits resolution and transmits the data to the data analysis unit. The readout board is based on programmable logic FPGA and DDR3 memories for on-line data preprocessing and temporary storage. The data is transmitted to the GPU computing node by a fast data transfer links based on a bus master DMA engine connected to PCI express endpoint logic to ensure a continuous high data throughput of up to 4 GByte/s. This heterogeneous real-time system architecture based on FPGA and GPU is used for on-line pulse reconstruction and evaluations and calculates the peak amplitude of each pulse and the time between consecutive bunches with a picosecond time resolution. A Fast Fourier Transform (FFT) is performed on-line for the frequency analysis of the CSR undulations. With the presented acquisition system it was possible to resolve the bursting behavior of single bunches even in a multi-bunch environment to study the bunch-bunch-interactions at ANKA. First results obtained have already been published in the synchrotron machine physic community. The monitoring of bursting for different ANKA parameters using KAPTURE system opens up new analysis and diagnostics possibilities for electron storage rings operating at short bunch lengths.  
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MOPD17 Single-Shot Electro-Optical Diagnostics at the ANKA Storage Ring 182
 
  • N. Hiller, A. Borysenko, E. Hertle, V. Judin, B. Kehrer, A.-S. Müller, M.J. Nasse, M. Schuh, P. Schönfeldt, N.J. Smale, J.L. Steinmann
    KIT, Karlsruhe, Germany
  • P. Peier, B. Steffen
    DESY, Hamburg, Germany
  • V. Schlott
    PSI, Villigen PSI, Switzerland
 
  Funding: This work is funded by the BMBF contract numbers: 05K10VKC, 05K13VKA.
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 distribution can be extracted. The setup is tuned to 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 longitudinally 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, hinting bunch-bunch interactions.
 
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