Analysis of multibunch free electron laser operation

At the SASE-FEL user facilities FLASH and European XFEL, superconducting TESLA type cavities are used for acceleration of the driving electron bunches. The high achievable duty cycle allows for operating with long bunch trains, hence considerably increasing the efficiency of the machine. However, multibunch free electron lasers (FEL) operation requires longitudinal and transverse stability within the bunch train. The purpose of this work is to investigate the intra-bunch-train transverse dynamics at FLASH and European XFEL. Key relationships of superconducting rf cavity operation and the resulting impact on the intrabunch-train trajectory variation are described. The observed trajectory variation during multibunch user runs at FLASH is analyzed and related to both, intrabunch-train variations of the rf and the following impact on the multibunch FEL performance

A 96 channel receiver for the ILCTA LLRF system at Fermilab

The present configuration of an ILC main LINAC RF station has 26 nine cell cavities driven from one klystron. With the addition of waveguide power coupler monitors, 96 RF signals will be down-converted and processed. A down-converter chassis is being developed that contains 12 eight channel analog modules and a single upconverter module. This chassis will first be deployed for testing a cryomodule composed of eight cavities located at New Muon Laboratory (NML) - Fermilab. Critical parts of the design for LLRF applications are identified and a detailed description of the circuit with various characteristic measurements is presented. The board is composed of an input band-pass filter centered at 1.3GHz, followed by a mixer, which down-converts the cavity probe signal to a proposed 13 MHz intermediate frequency. Cables with 8 channels per connector and good isolation between channels are being used to interconnect each down-converter module with a digital board. As mixers, amplifiers and power splitters are the most sensitive parts for noise, nonlinearities and crosstalk issues, special attention is given to these parts in the design of the LO port multiplication and distribution

Capture cavity II results at FNAL

As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest Low Level RF (LLRF) results obtained with Capture Cavity II (CCII) at the ILC Test Accelerator (ILCTA) test facility. The main focus will be on controls and RF operations using the SIMCON based LLRF system developed in DESY [1]. Details about hardware upgrades and future work will be discussed

LLRF System Installation for the European XFEL

This contribution presents an overview of the complete low level radio frequency system (LLRF) installation in the European x-ray free electron laser (E-XFEL). The focus is on the MicroTCA.4-based LLRF system architecture, testing and preliminary results. Some performance results of the commissioned XFEL injector will also be presented

Operational Statistics with MTCA LLRF Systems at FLASH and XFEL

User facilities require an accelerator uptime as high as possible. To help achieve availability of 95% and higher a low level radio frequency (LLRF) on-call service was set in place at DESY to support operation of the European XFEL and FLASH. In this contribution, operational statistics summarizing experts interventions, types of failure and associated downtime will be presented

Low Level RF for SRF Accelerators

Low level radio frequency (LLRF) systems are a fundamental component of superconducting RF accelerators.Since the release of the MicroTCA standard (MTCA.4), major developments in MTCA.4-based LLRF systems have taken place. State-of-the-art LLRF designs deliver better than 10−4 relative amplitude and 10mdeg phase stability for the vector sum control of SRF cavities. These developments in LLRF systems architecture and technology, driven by research institutes and supported by the industry are of highest importance for the European XFEL, but also for other SRF-based projects such as LCLS-II and the ESS, as well as for the next generation accelerators with 10−5 and mdeg regulation requirements