Precise average current measurement of CW beams or macropulses
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Precise average current measurement of CW beams or macropulses


The CWCT is a current transformer with strict limits on lower and upper cut-off frequencies, tailored to the beam RF. Its lower cut-off assures negligible droop between bunches. Yet, droop is high enough to allow fast differentiation.

Its upper cutoff is high enough to allow output signal return to baseline after each bunch, yet low enough to assure an output duty factor close to 50%. Thus it is tailored to the bunch length, facilitating the measurement of short bunches.

The BCM-CW-E is the electronics module processing the CWCT output signal.

By applying fast sample-and-hold techniques it measures the average beam current with microsecond response time.

Properly adjusted signal amplification and filtering improves the resolution of small beam current fluctuations.

Main features

  • Resolution of 1 µArms
  • With Low Current option: ≤ 8 nA rms resolution
  • Operating Frequency from 15 MHz to 200 MHz
  • Response Time of 1 µs



  • CWCT is mounted directly on the beam line
  • Improved radiation tolerance on option
  • Ceramic gap vacuum-brazed over kovar transition
  • Material AISI-304, 316LN on option
  • Arbitrary shape aperture on option
  • 1 core or 2 cores on option


BCM-CW-E uses fast sample-and-hold techniques to average the beam current.

BCM-CW-E inserts into a wired station of BCM-RFC, the 19” 3U RF-shielded chassis including power supplies.

Up to 10 stations per chassis can be installed.

Low Current option

The Low Current option allows to measure beams with tens of nanoamperes intensity, a shielded frontend electronics can be directly attached to the sensor.

This front-end consists of a Low-Noise Amplifier and specially tuned filters.

With the LC-CWCT and BCM-CW-E, a few nanoamperes resolution can be reached.


  • Beam repetition frequency 15 – 200 MHz
  • 3 selectable full scale ranges
  • IndependantIndependent of bunch shape and width
  • EMI, RFI and temperature immune
  • Linearity error < 1.5%
  • Beam loss resolution < 1%
  • UHV compatible down to 1E-11 mbar