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PTW 30012 Farmer Chamber

PTW 30012 Farmer Chamber
PTW 30012 Farmer Chamber

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PTW 30012 Farmer® Chamber.


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PTW 30012 Farmer® Chamber.

The 0.6 cm3 PTW Farmer chambers are designed for absolute photon and electron dosimetry with therapy dosemeters.  Three chamber types for measurements in air or in solid state phantom material are available.

Thimble chambers for measuring high-energy photon and electron radiation in air or in phantom material.

• Fully guarded chamber

• Vented sensitive volumes of 0.6 cm3

• Suitable as therapy chambers for use in solid phantoms

• Flat energy response

• Correction factors needed to determine absorbed dose to water or air kerma are published in the pertinent dosimetry protocols.

• The chambers are designed for the use in solid state phantoms and are not waterproof.

The 30012 is a Farmer chamber with graphite wall.  The 30012 Farmer chamber is intended for absolute dose measurements in radiation therapy.  The graphite wall makes the chamber almost water-equivalent, the aluminum central electrode improves the energy response at energies below 60Co used for therapy dosimetry.  The 30012 is used where a chamber with graphite wall and Al electrode is required.  The nominal photon energy range is from 60 kV to 50 MV.

The electron energy range of all chambers is from 10 MeV to 45 MeV.  The chambers type 30011 and 30012 with their graphite caps are of delicate construction and should be handled with extreme care.  The guard rings of all chamber types are designed up to the measuring volume.  An acrylic build-up cap for in-air measurement in 60Co beams is included with each chamber, as well as a calibration certificate.

Type of Product:  vented cylindrical ionization chamber acc. IEC 60731
Application:  absolute therapy dosimetry in solid state phantoms and air
Measuring Quantities:  absorbed dose to water, air kerma, exposure
Reference Radiation Quality:  60Co
Nominal Sensitive Volume:  0.6 cm3
Design:  NOT waterproof, vented fully guarded
Reference Point:  on chamber axis, 13mm from tip
Direction of Incidence:  radial
Nominal Response:  20 nC/Gy
Long-term Stability:  ≤0.5 % per year
Chamber Voltage:  400 V nominal ±500 V maximal
Polarity Effect at 60Co:  < 0.5%
Photon Energy Response:  ≤ ± 2% (70 kV to 280 kV),  ≤ ± 4% (200 kV to 60Co)
Directional Response in  Solid State Phantom:  ≤ ± 0.5% for rotation around the chamber axis and for tilting of the axis up to ± 5°
Directional Response in Water: 
Leakage Current:  ≤ ± 4 fA
Cable Leakage:  ≤ 1 pC/(Gy∙cm)

Materials and Measures:  0.425 mm graphite
Wall of Sensitive Volume:  1.85 g/cm3

Total Wall Area Density:  79 mg/cm2
Dimension of Sensitive Volume:  radius 3.05 mm, length 23.0 mm
Central Electrode:  Al 99.98, diameter 1.1 mm
Build-up Cap:  PMMA, thickness 4.55 mm

Ion Collection Efficiency at Nominal Voltage: 
Ion collection time:  140 µs

Max. dose rate for:
> 99.5 % saturation:
  5 Gy/s
> 99.0 % saturation:  10 Gy/s

Max. dose per pulse for:
> 99.5 % saturation:
  0.46 mGy
> 99.0 % saturation:  0.91 mGy

Useful ranges: 
Chamber voltage:  ±100 to 400 V

Radiation quality:  60 kV to 50 MV photons (10 to 45) MeV electrons (50 to 270) MeV protons
Field size:  (5 x 5) cm2 to (40 x 40) cm2
Temperature:  50° - 104° F (10° - 40°C)
Humidity:  10 - 80 %, max 20 g/m3
Air pressure:  700 - 1060 hPa


Please specify which connection end is needed

Data Sheet


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