LR-BPM

Log-Ratio BPM Electronics

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LR-BPM

Principles

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.

Main features

  • Resolution X & Y Pickup diameter / 1000
  • Dynamic Range > 50 dB
  • Operating Frequency ≤ 500 MHz

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Datasheets

User's manual

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Signal processing

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.

Logs of opposite pickups are subtracted. If pickups are rotated, axes are translated to obtain X and Y positions.

The process is all-analog, wideband.

See also

Features

  • The Log-Ratio Beam Position Monitor (LR-BPM) is an electronics module for fast analog processing of beam pickups signals.
  • Input signals parallel processing allows single-pass position measurement.
  • Bunches at any repetition rate up to 500MHz. Individual bunches can be distinguished from one another up to 5 MHz repetition.
  • ±2V X and Y outputs are held until the next bunch when Sample & Hold mode (optional) is activated.
  • Provides log signal from each pickup electrode for computer analysis, with 5MHz bandwidth.
  • Cables length matching not critical: pickup signals don’t need to be in phase