S - BPM S Band Beam Position Monitor

The S-band / L-band Beam Position Monitor (S–BPM) is an electronics module for fast analog processing of beam pickup signals.
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Single-pass bunch and macropulses can be measured thanks to parallel processing of inputs. Macropulses and single bunches up to 2 MHz repetition rate can be measured individually. X and Y coordinates are memorized until the next macropulse of bunch. CW beam can be measured continuously. The X and Y coordinates are available permanently. Beam position motions up to 5 MHz can be observed.

X and Y outputs are strong analog ±2V signals.

S-band / L-band BPM is compatible with Bergoz' multiplexed BPM and Log-ratio BPMs. They can be plugged into the same chassis. Precise phase matching of input signals is not required.


  • Non-interceptive beam position measurement
  • For linacs, microtrons and transfer lines
  • Single bunch, macropulse and CW
  • Beam charge range > 1000


S–BPM was designed by S. Artinian based on the earlier LR-BPM by A. Kalinin


Front-end Filter / Amplifier FEFA:

One Front-end Filter / Amplifier is required for every BPM pickup electrode. It is tuned to the beam RF or harmonic. It is powered from the S–BPM module via the coaxial cable linking them together. It must be installed close to the BPM pickup block, e.g. 1 meter.


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. 

Schema S-BPM

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

Schema S-BPM