Performance tests of a new fast digitiser for beam diagnostic applications

A new type of PCI-based fast digitisers has been deployed to implement new beam diagnostic systems and as a prototype for a new family of applications. The modules selected for the first tests and applications are the Acqiris DC265 fast digitiser boards, characterised by a high sampling speed, a large amount of memory per channel (2 MSamples per channel as the chosen option) and a PCI bus interface. This note details the tests carried out, and the results obtained, to ascertain the DC265 board and crate suitability to general beam diagnostics applications

The LEIR LLRF DSP-Carrier Board : Performance, CPS Renovation Plan and Recommendations

The LEIR LLRF project started in late 2003 and included designing,manufacturing and commissioning a novel, all-digital beam control system. The project was first to provide the LEIR machine with a beam control system satisfying the many performance requirements. This was achieved in 2006 with the successful LEIR LLRF system commissioning. In addition, the project was to act as a pilot to export the same technology to the other machines of the PS Complex (CPS), such as PS, PSB and AD. New machines currently being proposed (e.g. ELENA) will also rely on it. The evaluation of the LEIR experience and the recommendations on how to best pursue this migration strategy are therefore integral parts of the LEIR LLRF project. A fundamental building block of the LEIR LLRF system is the DSP-carrier board where all beam control loops are implemented. This note examines the main features of the DSP-carrier board release 1.0 used in LEIR and evaluates their impact on the LEIR LLRF implementation and operational performance. An outline of the intermediate release 1.bis, currently under way, is given. The requirements for a future DSP-carrier board release 2 are outlined, as they were discussed and planned since 2004. The benefits of this new implementation are evaluated and it is recommended that this DSP-carrier board release be studied, designed and manufactured, particularly in view of ever more demanding RF gymnastics and requirements from the different CPS accelerators

Digital signal processor fundamentals and system design

Digital Signal Processors (DSPs) have been used in accelerator systems for more than fifteen years and have largely contributed to the evolution towards digital technology of many accelerator systems, such as machine protection, diagnostics and control of beams, power supply and motors. This paper aims at familiarising the reader with DSP fundamentals, namely DSP characteristics and processing development. Several DSP examples are given, in particular on Texas Instruments DSPs, as they are used in the DSP laboratory companion of the lectures this paper is based upon. The typical system design flow is described; common difficulties, problems and choices faced by DSP developers are outlined; and hints are given on the best solution

The DSP-Carrier Board Used by the LEIR Low-Level RF System: User's Manual

A new digital technology to implement beam control systems was tested in the PS Booster in 2004 and 2005 and commissioned in LEIR in 2006. The technology is based upon RF custom hardware that heavily exploits Digital Signal Processors (DSPs) and Field Programmable Gate Arrays (FPGAs) processing power. This architecture is extremely flexible in that it relies on a DSP-carrier board hosting one DSP and carrying different daughtercards. The LEIR beam control system deploys three DSP-carrier boards, which inter-communicate and exchange data continuously for the implementation of the various beam control loops. This user's manual for the DSP-carrier board, release 1.0 (EDA-00990-V1), was written in 2004 and has been used by CERN and BNL developers since then. It describes the DSP-carrier board hardware, user settings and FPGA software; hints on the DSP code used with the board are also given. An additional VME board, called Rear Transition Module, is described because it acts as a DSP-carrier board extension

The New Digital-Receiver-Based System for Antiproton Beam Diagnostics

An innovative system to measure antiproton beam intensity, momentum spread and mean momentum in CERN's Antiproton Decelerator (AD) is described. This system is based on a state-of-the-art Digital Receiver (DRX) board, consisting of 8 Digital Down-Converter (DDC) chips and one Digital Signal Processor (DSP). An ultra-low-noise, wide-band AC beam transformer (0.2 MHz - 30 MHz) is used to measure AC beam current modulation. For bunched beams, the intensity is obtained by measuring the amplitude of the fundamental and second RF Fourier components. On the magnetic plateaus the beam is debunched for stochastic or electron cooling and longitudinal beam properties (intensity, momentum spread and mean momentum) are measured by FFT-based spectral analysis of Schottky signals. The system thus provides real time information characterising the machine performance; it has been used for troubleshooting and to fine-tune the AD, thus achieving further improved performances. This system has been operating since May 2000 and typical results are presented

Proposal for a Cavity Phase Observation System in the PS Machine

In multi-cavity synchrotrons it is essential to be able to measure the phase difference between RF cavities. Errors in relative phase can have a particularly deleterious effect on the beam during RF gymnastics. Currently, two methods are available to measure the relative phase in the CERN Proton Synchrotron (PS), but neither attains the desired resolution nor covers the full arsenal of cavities. This note describes a system that will measure the relative phase between cavities with high resolution. The system makes use of the digital hardware deployed in the LEIR beam control and of the corresponding DSP and FPGA signal processing. The focus is on beams controlled by the Multi Harmonic Source (MHS) clock. The system described here is also a step towards the deployment of a new generation of digital beam control systems for the PS Complex machines, within the framework of the LHC injector consolidation and following the successful commissioning of the LEIR digital beam control system. Some expected benefits are briefly summarised at the end of this documen

Real-Time Tune Measurements on the CERN Antiproton Decelerator

A novel system for real-time tune measurement during deceleration of a low-intensity particle beam is presented. The CERN Antiproton Decelerator decelerates low intensity (2x107) antiproton beams from 3.5 GeV/c to 100 MeV/c. Because of the eddy-currents in the magnets, a tune-measurement during a pause in the deceleration would not be representative. One must thus be able to measure the tune in real time during the deceleration. The low intensity of the antiproton beam prevents the use of standard Schottky techniques, and swept Beam Transfer Function (BTF) measurements are too slow. A system was therefore developed which uses an M-shaped power spectrum, exciting the beam in a band around the expected frequency of a betatron side-band. Excitation at the betatron frequency, where beam response is highest, is thus minimized and measurements of BTF, and therefore the tune, can be made with much reduced emittance blow-u

Antiproton beam parameters measurement by a new digital-receiver-based system

The Antiproton Decelerator (AD) provides the users with very low intensity beams, in the 107 particles range, hence prompting the development of an innovative measuring system, which was completed in early 2000. This system measures antiproton beam intensity for bunched and debunched beams, together with momentum spread and mean momentum for debunched beams. It uses a state-of-the-art Digital Receiver board, which processes data obtained from two ultra-low-noise, wide-band AC beam transformers. These have a combined bandwidth in the range 0.02 MHz - 30 MHz and are used to measure AC beam current modulation. For bunched beams, the intensity is obtained by measuring the amplitude of the fundamental and second RF Fourier components. On the magnetic plateaus the beam is debunched for stochastic or electron cooling and longitudinal beam properties (intensity, momentum spread and mean momentum) are measured by FFT-based spectral analysis of Schottky signals. The system provides real-time information characterising the machine performance; it has been used for troubleshooting and to fine-tune the AD, thus allowing further improved performance. This system has been operating since May 2000 and providing beam intensity data to the users on a routine basis since late 2000. A dedicated software package was expressly developed to take care of the control, data acquisition and processing phases. It consists of three main codes, namely a GUI, a Real Time Task and a Low Level Code. This report gives an overview of both the hardware and software developed

Beam Measurement Systems for the CERN Antiproton Decelerator (AD)

The new, low-energy antiproton physics facility at CERN has been successfully commissioned and has been delivering decelerated antiprotons at 100 MeV/c since July 2000. The AD consists of one ring where the 3.5 GeV/c antiprotons produced from a production target are injected, rf manipulated, stochastically cooled, decelerated (with further stages involving additional stochastic and electron cooling and rf manipulation) and extracted at 100 MeV/c. While proton test beams of sufficient intensity could be used for certain procedures in AD commissioning, this was not possible for setting-up and routine operation. Hence, special diagnostics systems had to be developed to obtain the beam and accelerator characteristics using the weak antiproton beams of a few 10E7 particles at all momenta from 3.5 GeV/c down to 100 MeV/c. These include systems for position measurement, intensity, beam size measurements using transverse aperture limiters and scintillators and Schottky-based tools. This paper gives an overall view of these systems and their usage