ACCT

Precise waveform measurement of long pulses

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Precise waveform measurement of long pulses

Principle

The ACCT is an evolution of the active transformer first proposed by Hereward in 1960.

Compared to the Hereward transformer, the ACCT presents much lower noise, a DC offset of the output reduced to a very small value and excellent long-term stability.

The sensor is built with a single winding, which requires only one wire pair between sensor and electronics; this allows much better EMI rejection when long cables are used.

The electronics circuit is multistage, implementing the best low-noise operational amplifier available for this application.

Two packaging type for the ACCT sensor

In-flange ACCT

In-flange ACCT

  • In-flange ACCT is mounted in the beam line.
  • Short axial length (40 mm), includes a ceramic gap vacuum-brazed to kovar.
  • Does not require bellows, wall current bypass nor electromagnetic shield.
  • Available from CF3“3/8 to CF8“
  • Material AISI-304, 316LN on option
  • Bakeable up to 185°C
  • UHV compatible

In-air ACCT

In-air ACCT installation, over the vacuum chamber Requires installation of a “gap” to prevent the wall current from flowing through the ACCT aperture.

The gap can be a brazed ceramic ring or an organic material O-ring depending on the vacuum requirements.

Typical installations include bellows, a wall current bypass and an electromagnetic shield enclosing the ACCT completely.

In-air ACCT

Two versions of ACCT electronics

ACCT electronics with 3-selectable ranges

ACCT electronics with 3-selectable ranges

  • In addition, 3 outputs available: 50Ω, 1MΩ and differential outputs
  • DIN-rail mountable
  • Power supply available

ACCT electronics with single range

  • Output to be read in high impedance device
  • DIN-rail mountable
  • Power supply available
ACCT electronics with single range