N. Smale

An ultra-fast data acquisition system for coherent synchrotron radiation with terahertz detectors

The recording of coherent synchrotron radiation requires data acquisition systems with a temporal resolution of tens of picosecond. This paper describes a new real-time and high-accuracy data acquisition system suitable for recording individual ultra-short pulses generated by a fast terahertz (THz) detector (e.g. YBCO, NbN, Zero Biased Schottky Diode). The system consists of a fast sampling board combined with a high data throughput readout. The first board is designed for sampling the fast pulse signals with a full width half maximum (FWHM) between a few tens to one hundred picoseconds with a minimum sampling time of 3 ps. The high data throughput board consists of a PCIe-Bus Master DMA architecture used for fast data transfer up to 3 GByte/s. The full readout chain with fast THz detectors and the acquisition system has been successfully tested at the synchrotron ANKA. An overview of the electronics system and preliminary results with multi-bunch filling pattern will be presented.

Real-time measurement of picosecond THz pulses by an ultra-fast YBa2Cu3O7−d detection system

The temporal evolution of picosecond THz pulses generated at ANKA, the electron storage ring of the Karlsruhe Institute of Technology, has been measured in real-time using an ultra-fast YBa2Cu3O7−δ detection system. YBa2Cu3O7−δ thin-film detectors with 30 nm thickness were patterned to microbridges (2 μm long, 4.5 μm wide) and embedded into a planar log-spiral THz antenna. The detectors were glued on a silicon lens and installed in an ultra-fast readout system with a temporal resolution of 15 ps (full width at half maximum). Detector responses as short as 17 ps were recorded showing very good agreement with the expected storage ring bunch lengths.

High-Speed Y–Ba–Cu–O Direct Detection System for Monitoring Picosecond THz Pulses

A high-speed YBa₂Cu₃O_7-δ direct detection system was developed to monitor terahertz picosecond pulses in the time domain. High-T_C superconducting thin-film YBa₂Cu₃O_7-δ microbridges with critical temperatures of T_C = 85 K were embedded into a planar log-spiral antenna to couple the broadband terahertz radiation (0.1 -2 THz) of several picosecond pulsed sources. The YBa₂Cu₃O_7-δ detectors were installed in a liquid nitrogen cryostat equipped with 18 GHz effective bandwidth readout electronics. THz pulses generated at the electron storage rings ANKA and UVSOR-II have been resolved with a temporal resolution of 30 ps (full width at half maximum) limited by the readout electronics bandwidth. Beam dynamic effects of bursting coherent synchrotron radiation were successfully monitored.

Highly Responsive Y–Ba–Cu–O Thin Film THz Detectors With Picosecond Time Resolution

High-temperature superconducting YBa2Cu3O7 - δ (YBCO) thin-film detectors with improved responsivities were developed for fast time-domain measurements in the THz frequency range. YBCO thin films of ≈ 30 nm thickness were patterned to micro- and nanobridges and embedded into planar log-spiral THz antennas. The YBCO thin-film detectors were characterized with continuous wave radiation at 0.65 THz. Responsivity values as high as 710 V/W were found for the YBCO nanobridges. Pulsed measurements in the THz frequency range were performed at the electron storage ring ANKA from the Karlsruhe Institute of Technology (KIT). Due to the high responsivities of the nanobridges no biasing was required for the detection of the coherent synchrotron radiation pulses achieving very good agreement between the measured pulse shapes and simulations.

An ultra-fast digitizer with picosecond sampling time for Coherent Synchrotron Radiation

Since a few years Coherent Synchrotron Radiation (CSR) generated by short electron bunches is provided at the ANKA synchrotron light source. To study the THz emission characteristics over multiple revolutions superconducting YBa2Cu3O7-δ (YBCO) thin-film detectors can be used. The intrinsic response time of YBCO thin films is in the order of a few picoseconds only. For fast and continuous sampling of this individual ultra-short terahertz pulses a novel digitizer system has been developed with programmable sampling times in the range of 3 to 100 ps. The Real-time system is based on a heterogeneous FPGA and GPU architecture for on-line pulse reconstruction and evaluations of the peak amplitudes and the time between consecutive bunches. The data is transmitted to a GPU computing node by a fast data transfer link based on a bus master DMA engine connected to PCI express endpoint logic. This new DMA architecture ensures a continuous high data throughput of up to 4 GByte/s. The presented DAQ system is able to resolve the bursting behavior of single bunches even in a multi-bunch environment and to study the bunch-bunch-interactions.