Semiflex 3D Ion Chamber 31021

Always perfectly oriented.

  • Vented, waterproof, fully guarded - the ideal chamber for relative and reference dosimetry measurements in water, air or solid state phantoms
  • True 3D geometry - uniform response in any direction
  • Unique design - fast, accurate scanning in in-plane and cross-plane directions without tank rotation or change of detector setup
  • Easy horizontal or vertical mounting for high-resolution measurements in both radial and axial orientations
  • Reference-class ionization chamber with exceptional dosimetric characteristics - suitable for reference dosimetry following standard dosimetry protocols, e.g., IAEA TRS-398, AAPM TG-51
  • Small size (0.07 cm³), high spatial resolution - perfect for measurements in small and FFF fields down to a field size of 2.5 cm x 2.5 cm
  • Radioactive check device optionally available
Suitable for photon and electron dosimetry in multiple applications


  • LINAC Acceptance Testing
  • TPS Beam Data Commissioning
  • Clinical Reference Dosimetry
  • Point Dose Measurements
The New Reference Class

Semiflex 3D meets and exceeds the performance requirements of a reference-class ionization chamber as laid out in AAPM TG-51 and IEC 60731:

  • Minimal polarity effect (< 0.4 % correction, < 0.5 % maximum variation)
  • Extremely low volume effect (est. ≤ 0.05 % correction in FFF field)
  • Excellent chamber settling (< 0.3 %)
  • Very low post-irradiation leakage - far below IEC 60731 requirements
  • Significantly reduced cable effects (< 200 fC / (Gy * cm))
  • Minimal chamber-to-chamber variation - reliable kQ and kS values
  • Radioactive Check Device (T48012)

Radioactive check device for air density correction and constancy checks of therapy dosemeters when using vented ionization chambers.
Includes encapsulated low activity of 33 MBq.
Chamber holding devices and check device for use with flat chambers (T48010) optionally available.

  • Semiflex 3D Chamber Holder for Check Device (T48002.1.004)
  • TRUFIX Holders for Semiflex 3D with stop thimbles for axial and radial irradiation (L981483)
  • Adapter for PTW Water Phantom 41023 for horizontal beams (T41023.1.280)
  • Acrylic PMMA Chamber Plate 30 cm x 30 cm (T2967/U6)
  • RW3 Chamber Plate 30 cm x 30 cm (T29672/U33)
  • Chamber Plate for OCTAVIUS 4D (T40056.1.007)
Type No. 31021
Design: vented cylindrical ionization chamber, waterproof, fully guarded
Measured quantities: absorbed dose to water, air kerma, exposure
Nominal sensitive volume: 0.07 cm³,
radius 2.4 mm, length 4.8 mm
Reference point: on chamber axis, 3.45 mm from chamber tip
Nominal response: 2 nC/Gy
Chamber voltage: 400 V nominal
± 500 V maximal
Radiation quality: Co-60 ... 50 MV photons
(9 ... 45) MeV electrons
Field size: (2.5 x 2.5) cm² ... (40 x 40) cm²
(3.0 x 3.0) cm² ... (40 x 40) cm²
≥ 18 MV
Connectors: BNT, TNC or M

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Related Downloads

MR-RT Products ( 2 MB )
Semiflex 3D Chamber ( 637 KB )
Detectors Catalog ( 9 MB )
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