I128 - 128 Channel Charge Integrator Digital Electrometer

The I128 is Pyramid's controller and readout for position-sensitive ionization chambers, combining 128 independent strip-readout channels with a dedicated dose plane input in a single 1U chassis. Each strip channel uses a no-lost-charge switched integrator digitized at 20 bits, so the I128 tracks beam position and shape across a full multi-strip chamber while the dose plane channel measures absolute dose and drives beam control in real time.

The dose plane input runs in either I-V converter mode (0 to ±20μA, four ranges) or gated integrator mode (0 to ±10nC, two ranges), selectable in software, with external accuracy better than 0.1% of full scale in I-V mode and 0.2% in gated integrator mode. The 128 strip channels handle 0 to 600nA with input noise below 10fC and offset under ±0.5pA, giving clean readouts even at low beam currents. An integrated high voltage supply, available in four order-time voltage ranges up to 2000V, includes loop-back verification, and the built-in safety relay, front-panel key-switch override, and beam enable/interlock circuitry let the I128 sit directly in a dosimetry safety chain rather than needing separate interlock hardware.

For a general-purpose electrometer with even higher channel count, see the IX256, which offers 256 independent low-current input channels.