Uros Mavric

Multichannel vector field control module for LLRF control of superconducting cavities

The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33- channel, FPGA based down-conversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. A 32-bit, 400MHz floating point DSP provides additional computational and control capability for calibration and implementation of more complex control algorithms. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a SlotO CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as data acquisition.

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 up- converter 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 1.3 GHz, 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.

Standardized Solution for Management Controller for MTCA.4

The Micro Telecommunications Computing Architecture (MTCA) standard is a modern platform, that is gaining popularity in the area of High Energy Physics (HEP) experiments. The standard provides extensive management, monitoring and diagnostics functionality. The hardware management is based on the Intelligent Platform Management Interface (IPMI), that was initially developed for management and monitoring of complex computers operation. The original IPMI specification was extended and new functions required for MTCA hardware management, were added. The Module Management Controller (MMC) is required on each Advanced Mezzanine Card installed in MTCA chassis. The Rear Transition Modules (RTMs) require Rear transition module Management Controller (RMC) that is specified in MTCA.4 extension specification. The commercially available implementations of MMC and RMC are expensive and do not provide the whole functionality that is required by specific HEP applications. Therefore, many research centres and commercial companies work on their own implementation of AMC or RTM controllers. The available implementations suffer because of lack of a standard and interoperability problems. The Authors developed a unified solution of management controller fully compliant to AMC and MTCA.4 standards. The MMC v1.00 solution is dedicated for management of AMC and RTM modules. The MMC v1.00 is based on Atmel ATxmega MCU and can be fully customized by user or used as a drop-in-module without any modifications. The paper discusses the functionality of the MMC v1.00 solution. The implementation was verified with developed evaluation kits for AMC and RTM cards.

RTM RF Backplane for MicroTCA.4 crates

We developed a new Rear Transition Module (RTM) Backplane for MicroTCA.4 crates that is compliant with the PICMG standard and is an optional crate extension. The RTM Backplane provides multiple links for high-precision clock and RF signals to analog μRTM cards. Usage of an RTM Backplane allows to significantly simplify the cable management, and therefore to increase the reliability of electronic controls when multiple analog RF front-ends are required. In addition, the RTM backplane allows also to add so called extended RTM (eRTM) and RTM Power Modules (RTM-PM) to a 12-slot MicroTCA crate. Up to four 6 HP wide eRTMs and two RTM-PMs can be installed behind the front PM and MCH modules. An eRTM attached to the MCH via Zone 3 connector is used for analog signal management on the RTM backplane. This eRTM allows also installing a powerful CPU to extend the processing capacity of the MTCA.4 crate. Remaining three eRTMs provide additional space for analog and digital electronics that may not fit on the standard RTM cards. The RTM-PMs deliver managed low-noise (separated from front crate PMs) analog bipolar power (+VV, -VV) for the μRTMs and an unipolar power for the eRTMs. This extends functionality of the MicroTCA.4 crate and offers unique performance improvement for analog front-end electronics. This paper covers a new concept of the RTM Backplane, a new implementation for the real-time LLRF control system and performance evaluation of designed prototype.

Multi-channel down-conversion for MicroTCA.4 based control systems

One of the major benefit of the MicroTCA.4 system is to combine high-speed digital data processing AMC boards with high precision analog signal conditioning RTM boards. We present a multi-channel down-converter based on the MicroTCA.4 system operating in the 1GHz to 4GHz range with an excellent short-term amplitude stability of 6.5E-5 and phase stability of 3.5E-3 degree within a 1MHz bandwidth at 1.3GHz. The down-converter consists of the entire receiver, packed as an RTM board, which down converts the high frequency signal into an intermediate frequency, which is non-IQ sampled by a multi-channel 16-bit digitizer realized as an AMC board. We present all relevant signals along the detection chain and discuss the signal integrity within the RTM and AMC boards for a spurious free operation of the best ADCs available today.

Real time control of RF fields using a MicroTCA.4 based LLRF system at FLASH

The Free Electron Laser in Hamburg (FLASH) is a large scale user facility, providing highly stable and brilliant laser pulses down to a wavelength of 4.1 nm. Essential for stable and reproducible photon beam is the precision control of the electron bunch parameters. The acceleration principle of the electron bunches at FLASH is based on superconducting RF technology (SRF), in which the RF fields are controlled by a digital low level RF (LLRF) system. This system has been recently upgraded to the Micro Telecommunication Computing Architecture (MicroTCA.4) to improve the performance of the field regulation. This paper presents the first measurements and operation experiences using this new electronic crate standard at a large scale research facility. RF field regulation is carried out by real time fast digital processing on several boards in a MicroTCA.4 crate, and slow automation routines running on a dual core i7 front-end CPU. Scalability and modularity of this system is one of the key parameters to meet the next steps, namely being the platform standard for the European X-ray free electron laser currently build at DESY.

Analog Receiver and Transmitter Design for the ILC Main LINAC LLRF Control System

Particle accelerators of the next generation, like the International Linear Collider (ILC), will need exceptional beam quality in order to achieve the required luminosity and beam energy dictated by the experiments. Performance of a low-level radio frequency (LLRF) control system plays a major role in preserving beam quality in a particle accelerator. LLRF system regulation specifications are usually given in terms of phase and amplitude stability of the detected fields in a cavity and in the case of the ILC these are not the same for all parts of the machine. For instance, bunch compressor and damping rings have more severe specifications in terms of regulation than the main linear accelerator (LINAC). In the introduction, we present the main design issues for the ILC main LINAC LLRF system and focus on the analog receiver and transmitter design. In the first section a short overview of the main design approaches is given. In the following section we present measurements of the main building blocks in an analog receiver and transmitter and apply measured data on a model. We study interactions between the two modules, when integrated in a closed loop LLRF system. At the end, we present results followed by conclusion.

Mitigating Noise Sources in MTCA.4 Electronics for High Precision Measurements

The RF field detection instrumentation plays a crucial role in modern accelerator performance. The most critical section is the transition from the analog signal processing to the digitalization. In this paper we present state of the art performance of COTS components and limitations imposed by crate-oriented solutions. We give recipes on how to optimize performance and present some of the recent results.