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.