New Parametric Current Transformer

For non-destructive measurement of average beam current.

NPCT can be installed "In-air" over the vacuum chamber or "In-flange", embedded inside a conflat flange for direct mounting on the beam pipe.


The New Parametric Current Transformer is the latest evolution of the Unser Transformer, commonly called DCCT, developed at CERN in 1966 by Klaus B. Unser:


  • Full scale range from ±20mA to ±20A controlled by TTL levels
  • 5 uA/sqrt(Hz) resolution in every range
  • 1 uA/sqrt(Hz) or lower resolution on option
  • Frequency response DC to 10 kHz
  • Linearity error < 0.1%
  • In-air sensor inner diameter from 55 to 245 mm to fit around any vacuum chamber
  • In-flange sensors from DN/NW25CF to DN/NW200CF flanges
  • In-flange with round aperture from 22.2mm to 198.4mm
  • Also for arbitrary shape vacuum chamber sections
  • NPCT package includes spares for electronics and power supply




Parametric Current transformers are used on most particles accelerators in the world to measure the average beam current. They are essential instrument for machine tuning, commissioning, operation and machine/personnel safety.
The large dynamic range, the wide bandwidth and high resolution make it the ideal instrument to measure beam lifetime in storage rings.
It is often the only truly calibrated beam instrument in an accelerator and serves as a reference to calibrate other beam diagnostics.


Operating Principle:


The NPCT works on the principle of the zero-flux DC current transformer (DCCT). The DC component of the current flowing throught the toroid sensor is detected by a magnetic modulator also called fluxgate or second harmonic detector.
The AC component is detected by a AC Hereward transformer. The two circuits are cascaded in a common feedback loop to generate a magnetic flux which always cancel the primary currrent flux. The NPCT ouptut is the voltage developed by the feedback current passing through a precision resistor.