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Bergoz Beam Position Monitors, BPM 
The Bergoz Log-Ratio Beam Position Monitor
(LR-BPM) is an electronics module designed for fast processing of beam position signals. To acheive this, the signals are parallel processed in a single pass position measurement. It is a non-intercepting system that is suitable for use in most Linacs, transfer lines, first turns, boosters and fast-cycling synchrotrons

For Beam Position Monitoring in electron and positron Storage Rings, please refer to the MX-BPM.

The LR-BPM is in use at <<Insert customers using the LR-BPM here>>.

The LR-BPM features
   •  Input signals are parallel processed allowing a single-pass position measurement.
   •  Beam charge range > 500
   •  Beam-based center determination
   •  Bunches at any repetition rate up to 500 MHz Individual bunches can be distinguished from one another up to 5 MHz repetition
   •  Log-Ratio BPM is plug compatible with Bergoz' multiplexed BPM
   •  L-band, S-band, X-band beams can be processed provided bunch groups are short (<3 ns)
   •  ±2V X and Youtputs are held until the next bunch when Sample & Hold mode (optional) is activated.
   •  Provides log signal from each pickup electrode for computer analysis, with 5 MHz bandwidth.
   •  Beam-based center determiuation accessory equalizes pickup signals to simulate beam on center.
   •  The Log-Ratio Beam Position Monitor (LR-BPM) is an electronics module for fast analog processing of beam pickup signals
   •  LR-BPM may be custom-built on daughter card for installation on user's DSP motherboards
   •  Cables length matching not critical pickup signals don't need to be in phase

Operating Principle
Based on the pioneering work of Robert E. Shafer at Los Alamos Laboratory, the Log-Ratio BPM derives beam position from logarithm of the ratio of opposite pickup signals Log(A/B).

Position measured by this method is more linear, over a wider range, than difference-over-sum.

The position of the beam from rotated pickups is obtained by axes translation to the vertical resp horizontal plane by wideband analog circuits

Signal Processing
The signals from the pickups are stretched to produce bursts. This is essential to measure the single pass of a bunch. Four parallel logarithmic amplifiers detect the burst envelopes. Amplifiers' response is log of amplitude and the logs of opposite pickups are subtracted. If pickups are rotated, axes are transtated to obtain X and Y positions. The process is all wideband analog.

Beam-based Center Determination
Differences between parallel processing channels can be nearly eliminated by using the Beam-based center determination accessory. It equalizes opposite pickup signals to simulate beam on center. The zero offsets can thus be measured at regular intervals under user's control and subtracted from subsequent readings. Signals entering the equalizer must be in phase. It is controlled by the LR-BPM module, via the input cables. Center determination and beam position measurement may be interleaved.
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