The new digital-receiver-based system for antiproton beam diagnostics

Abstract

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.

A novel current mode operating beam counter based on not preamplified HPDs

“…The ADC data were transfered to a personal computer via a VME/MXZ bus, while the scope data were readout via GPIB and both recorded on a disk. The number of ps was measured for each shot before the extraction by a low noise Schottky pickup (SP) [17,18], with a sensitivity of ≃ 1%. The beam was fully dumped by an Al foil, positioned at the entrance of the ATHENA beam pipe, as shown in fig.…”