[en] At Elettra, the Italian synchrotron light source, an internal project has been started to develop an electron beam position monitor capable of achieving sub-micron resolution with a self-compensation feature. In order to fulfil these requirements, a novel RF front end has been designed. A high isolation coupler combines the input signals with a known pilot tone which is generated by the readout system. This allows the parameters of the four channels to be continuously calibrated, by compensating the different responses of each channel. A similar technique is already known, but for the first time experimental results have shown the improvement in resolution due to this method. The RF chain was coupled with a 4-channel digitizer based on 160 MHz, 16 bits ADCs and an Altera Stratix FPGA. At first, no additional processing was done in the FPGA, collecting only the raw data from the ADCs; the position was calculated through the FFT of each signal. A simulation was also performed to verify the analytic relation between spatial resolution and signal-to-noise ratio; this was very useful to better understand the behaviour of the system with different sources of noise (aperture jitter, thermal noise, etc.). The experimental data were compared with the simulation, showing indeed a perfect agreement with the latter and confirming the capability of the system to reach sub-micrometric accuracy. Therefore, the use of the pilot tone greatly improves the quality of the system, correcting the drifts and increasing the spatial resolution by a factor of 4 in a time window of 24 hours.

[en] The paper presents first operational experience with the new digital beam position monitoring system (DBPM) for the Swiss Light Source (SLS). The system permits for the first time to have a single position monitoring system that measures both the slow and the fast aspects of beam position. When the electronics is set to 'slow', the DBPM allows position measurements with high precision, stability and reproducibility and is ideally suited for closed orbit measurements and feedback systems. When set to 'fast', the DBPM turns into a powerful beam dynamics tool that permits to extract more dynamic parameters of the beam/machine from turn-by-turn position readings. The key strengths of the system is its programmability that delivers an arbitrary FIR low pass transfer function with a bandwidth spanning from few hundred Hz to over 1 MHz, good reproducibility obtained through the use of a pilot signal and excellent linearity that relies on the direct sampling of the intermediate frequency signal (IF). The core components of the system are the RF front end, the digital receiver and the DSP board, which are all housed in a VME crate. The interface to the EPICS control system at SLS is done via an Input/Output Controller, which resides in the same crate

[en] A prototype Low Gap BPM system has been installed at ELETTRA and it is now undergoing the first tests. The main purpose of this system is to provide ultra-stable position signals, at the micrometer level, to the Orbit Feedback processors. The system consists of a new Low Gap monitor and a new digital BPM electronics. The monitor was designed at ELETTRA and fits to the 14 mm low gap ID vacuum chamber. Full advantage has been taken from the reduced gap button distance. To reach maximum stability of the BPM itself, a new support system has been designed where, by means of two bellows, the BPM movements are de-coupled from the vacuum chamber slow drifts. Furthermore an external system monitors the BPM position with respect to a reference column made of carbonium. The Low Gap BPM system adopts the digital BPM electronics that was conceived at the Paul Scherrer Institut for the Swiss Light Source (SLS). One of its features is the programmable bandwidth that offers sub-micron position data when set to low bandwidth (<1 kHz). The project evolved into a successful collaborative development between ELETTRA, APL, SLS and the company Instrumentation Technologies. In this paper the first results obtained on the ELETTRA Storage Ring are presented and future system integration is outlined