A low-noise front-end for an X-band particle deflector at DESY

Reukauff, Matthias; Hoffmann, Matthias; Jacob, Arne

Book/Dissertation / PhD Thesis

PUBDB-2022-03160

A low-noise front-end for an X-band particle deflector at DESY

Reukauff, M. (Corresponding author)DESY* ; Hoffmann, M. (Thesis advisor)DESY* ; Jacob, A. (Thesis advisor)

2022
Verlag Deutsches Elektronen-Sychrotron DESY Hamburg

Hamburg : Verlag Deutsches Elektronen-Sychrotron DESY, DESY-THESIS 110 pp. (2022) [10.3204/PUBDB-2022-03160] = Dissertation, Technische Universität Hamburg, 2022

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Please use a persistent id in citations: urn:nbn:de:gbv:830-882.0188609 doi:10.3204/PUBDB-2022-03160

Report No.: DESY-THESIS-2022-011

Abstract: In this thesis, a low-level RF (LLRF) system for the novel polarizable transverse deflecting structure PolariX TDS is developed, installed, and commissioned at the FLASHForward beamline at DESY. The PolariX TDS operates in the X-band at 12 GHz and requires an LLRF system capable of measuring and processing signals in this frequency band. Using an approach to reuse the existing S-band LLRF system that can process signals at 3 GHz, new hardware is being developed that converts RF signals between 12 GHz and 3 GHz.The underlying components of this conversion hardware are RF mixers, filters, amplifiers, and frequency multipliers. Various candidates for all these components are characterized and compared in terms of their electrical characteristics. Since the final system performance depends heavily on the phase noise, the main focus of the characterization will be on this.With the components selected, printed circuit boards are designed, simulated, produced and packaged in hermetically sealed housings before being mounted in 19" modules. After completion, the modules are also characterized in the laboratory.As a final step, the prototype of the PolariX TDS will be installed in the FLASHForward beamline together with the developed LLRF system. After successful commissioning, first measurements will be performed in the running accelerator. To analyze the short-term behaviour, possible procedures to eliminate the long-term effects will be discussed.The actuator chain, consisting of LLRF system, klystron and its preamplifier, is measured and characterized. The results show some discrepancy between expected and measured values and an analysis of possible sources of the problem is performed.Beam-based measurements are used to analyze the relation between the RF and the beam in terms of phase and amplitude noise. These measurements show good performance of the overall system in terms of short term phase stability in general. However, small deviations from the expected behavior are seen, analyzed, and procedures to correct them are proposed. Analyses of the long-term behavior show a large difference between the RF and beam-based measurements, which causes are still subject of research.Although not as important as the phase noise, the amplitude noise is also investigated and similar to the long term behavior, the measured RF shows better performance than the beam based measurements.

Note: Dissertation, Technische Universität Hamburg, 2022

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