THz-based accelerator diagnostics
Terahertz (THz) based electron bunch diagnostics are critical techniques used in modern particle accelerators to measure the longitudinal profile, length, and arrival time of ultra-short (femtosecond and picosecond) electron bunches. As accelerators like Free-Electron Lasers (FELs) and Laser-Wakefield Accelerators (LPA) push toward shorter pulse durations, traditional radio-frequency (RF) structures hit physical resolution limits. THz methods bypass these boundaries by utilizing the short wavelengths and high frequencies of terahertz radiation to achieve sub-femtosecond temporal resolution.
The main focus of the actual research activities at the HZDR within the program topic accelerator-research and development: subtopic 3 ps - fs photon and electron beams (ARD-ST3) is in the development of such versatile (THz-based) diagnostics for electron bunches and superradiant THz sources. To this end (T)ELBE serves within ARD-ST3 as a testfacilitiy for diagnostics on quasi-CW electron and photon beams. Two examples for are the first demonstration of pulse-resolved arrivaltime monitoring at high repetition rate [1], as well as the development of an integrated THz spectrometer chip for advanced bunch compression monitoring [3,4]. Other activities within ARD-ST3 are the characterization and development of compact superradiant THz sources [2,5,6,7]. (T)ELBE also serves as a test field for the implementation of existing diagnostics such as Bunch-Arrival-Time (BAM) Monitors of the XFEL type at high-current quasi-cw accelerators [8] or electro-optic sampling (EOS) based bunch duration monitors [9].
Benchmarking of the THz-based XUV tomography scheme as arrival time monitor. 2D plot of the THz electric field for 600 consecutive pulses with artificially generated timing jitter of
40 fs (left, color coding represents field strength); white line represents the central peak of the THz waveform. (a) Corresponding line-out of the temporal
position of the central maximum of the THz waveform for an artificially generated jitter of approximately 40 fs, (b) line-out for approximately 10 fs, and (c) line-out for
0 fs. The light blue line indicates artificially introduced arrival time variations, and the light red line denotes the observed arrival time jitter.
From I. Ilyakov, et al., "Terahertz-wave decoding of femtosecond extreme-ultraviolet light pulses," Optica 9, 545-550 (2022) .
© 2022 Optica Publishing Group. Reproduced under the terms of the Optica Open Access Publishing Agreement.
For accelerator-based experiments on ultrafast processes, the single-pulse information on the arrival time, duration, and shape of the probing x-ray and XUV pulses is essential. In collaboration with the European XFEL and FERMI, a terahertz time-domain detection system was demonstrated which uses single-shot EOS measurements to precisely map duration, arrival time, and energy of each individual XUV pulse. [10]
This research is performed in close collaboration with colleagues from DESY, KIT and SLAC and also extends to the development of diagnostics suitable for 4th Generation X-ray lightsources such as FLASH [11,12], FERMI [10], the European XFEL, LCLS and TU Darmstadt [13].
The research activities are funded through the HGF (program topic ARD), the BMBF (projects INSeL and SAMoS) as well as the European Union (EUCALL).
[1] S. Kovalev et al., "Probing ultra-fast processes with high dynamic range at 4th-generation light sources: Arrival time and intensity binning at unprecedented repetition rates", Struct. Dyn. 4 (2017), 024301.
[2] B. Green et al., "High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter", Sci. Rep. 6 (2016), 22256.
[3] M. Schiselski et al., "Integrated Schottky Diode Detector for THz Spectrometer", Proceedings of 2015 GERMAN MICROWAVE CONFERENCE, (2015), 272.
[4] M. Schiselski et al., "A planar Schottky diode based integrated THz detector for fast electron pulse diagnostics", 2016 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM (IMS), (2016).
[5] M. Gensch et al., "SUPER-RADIANT LINAC-BASED THz SOURCES IN 2013", Proceedings of FEL2013, New York, NY, USA, (2013), WEIBNO01.
[6] V. Asgekar et al., "Interference effects in super-radiant THz sources", Infrared Phys. Technol. 64 (2014), 26.
[7] S.S. Dhillon et al., "The 2017 terahertz science and technology roadmap", Journ. Phys. D 50 (2017), 043001.
[8] A. Angelovski et al., "Evaluation of the cone-shaped pickup performance for low charge sub-10 fs arrival-time measurements at free electron laser facilities", Phys. Rev. Spec. Top. 18 (2015).
[9] C. Kaya et al., Phase sensitive monitoring of electron bunch form and arrival time in superconducting linear accelerators, Appl. Phys. Lett. 100 (2012), 141143.
[10] I. Ilyakov, N. Agarwal, J.-C. Deinert, J. Liu, A. Yaroslavtsev, L. Foglia, G. Kurdi, R. Mincigrucci, E. Principi, G. Jakob, M. Kläui, T. S. Seifert, T. Kampfrath, S. Kovalev, R. E. Carley, A. O. Scherz, and M. Gensch, "Terahertz-wave decoding of femtosecond extreme-ultraviolet light pulses," Optica 9, 545-550 (2022)
[11] F. Tavella, N. Stojanovic, G. Geloni & M. Gensch, Few Femtosecond Timing at Fourth Generation X-ray Lightsources, Nat. Photon. 5 (2011), 162.
[12] R. Riedel et al., "Single-shot pulse duration monitor for extreme ultraviolet and X-ray free-electron lasers", Nature Comm. 4 (2013), 1731.
[13] R. Yadav et al., State-of-the-Art Room Temperature Operable Zero-Bias Schottky Diode-Based Terahertz Detector Up to 5.56 THz. Sensors 23, 3469 (2023).
