Schottky Diode Detectors for Monitoring Coherent THz Synchrotron Radiation Pulses

Abstract

Coherent synchrotron radiation (CSR) in the terahertz frequency range is a powerful tool for the diagnostics of the electron-beam relying on the fact that the emission spectrum of THz CSR depends on the shape of the electron bunch from which the radiation is emitted. Among available direct THz detectors only superconducting microbolometers and Schottky diodes are capable to resolve single CSR pulses. Here we present recent photoresponse measurements of CSR with a quasioptical zero-bias Schottky diode detector which was produced at ACST GmbH. The rise-time of the recorded real-time transient was limited to approximately 20 ps by the 18-GHz bandwidth of interconnecting cables. Non-saturated responsivity of the detector, that is the amplitude of the voltage transient referred to the total CSR pulse energy in the detector quasioptical mode, was approximately 1.5 mV/fJ. The dynamic range of the detector spans almost three orders of magnitude from 3 fJ to 1 pJ. The intrinsic jitter of the detector was less than 2 ps thus not affecting the effective time resolution and allowing us to measure the arrival-time jitter of CSR pulses for different settings of the storage ring parameters.