IBA Dosimetry Product Detectors

NACP Plane Parallel Chamber


The NACP is designed according to recommendations of the Nordic Association of Clinical Physicists (NACP), Acta Radiologica Oncology 19,55. The chamber is used for absolute dosimetry of electron beams 2-50 MeV. A thinner front wall minimizes contamination of the beam, allows measurements at shallow depths, and guarantees high accuracy even at low electron energies. It can be used for proton beam absolute and relative dosimetry and for photon beam depth-dose measurements as well.

The collecting electrode is manufactured of graphitized polystyrene. The NACP chamber cable is covered by a watertight silicon sleeve that allows for air ventilation.

Technical specs

Inner dimensions

  • Sensitive volume (nominal): 0.16 cm3
  • Cylinder height: 2.0 mm
  • Entrance window (polarizing electrode) diameter: 20 mm
  • Entrance window thickness: Mylar foil 0.1 mm & Graphite 0.5 mm
  • Diameter of collecting electrode: 10.0 mm
  • Guard ring outer diameter: 18 mm
  • Guard ring width: 3.0 mm

Operational characteristics

  • Polarizing voltage: ±200 V (max. ±400 V)
  • Typical leakage current: 5 fA
  • Recommended pre-irradiation: 5 Gy
  • Typical sensitivity: 6 nC/Gy
  • Guard potential: ±200 V (max. ±400 V)
  • Temperature range: +15 to +35 °C
  • Relative humidity range: 20 % to 80 %