Farmer^® Ionization Chamber 30010

Classical therapy chamber for reference dosimetry in high-energy photon, electron and proton beams

Acrylic wall, graphited
Aluminum central electrode
Sensitive volume 0.6 cm3 , vented
Reference class in accordance with IEC 60731 and AAPM TG-51 Addendum

The 30010 Farmer chamber is a wide spread ionization chamber for reference dose measurements in radiation therapy.
Correction factors needed to determine absorbed dose to water or air kerma are published in the pertinent dosimetry protocols.

The acrylic chamber wall ensures the ruggedness of the chamber.
The chamber is designed for the use in solid state phantoms and therefore not waterproof.

Type of product	vented cylindrical ionization chamber
Application	reference dosimetry in solid state
	phantoms and air
Measuring quantities	absorbed dose to water, air kerma, exposure
Reference radiation quality	Co
Design	not waterproof, vented, guarded
Direction of incidence	radial
Nominal sensitive volume	0.6 cm³
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 %
Reference point	on chamber axis, 13 mm from chamber tip
Photon energy response	≤ ± 2 % (70 kV ... 280 kV)
	≤ ± 4 % (200 kV ... ⁶⁰Co)
Directional response in solid state phantom	the chamber axis and for tilting of the axis up to ± 5°
Leakage current	≤ ± 4 fA
Cable leakage	≤ 1 pC/(Gy·cm)

Materials and measures

Wall of sensitive volume	0.335 mm PMMA, 1.19 g/cm³
	0.09 mm graphite, 1.85 g/cm³
Total wall area density	56.5 mg/cm²
Dimensions of sensitive volume	radius 3.05 mm
	length 23.0 mm
Central electrode	Al 99.98, diameter 1.15 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

Ranges of use

Chamber voltage	± (100 ... 400) V
Radiation quality	30 kV ... 50 MV photons
	(10 ... 45) MeV electrons
	(50 ... 270) MeV protons
Field size	(5 x 5) cm2 ... (40 x 40) cm²
Temperature	(10 ... 40) °C
	(50 ... 104) °F
Humidity	(10 ... 80) %, max 20 g/m³
Air pressure	(700 ... 1060) hPa

Options

T48012	Radioactive check device ⁹⁰Sr
T48002.3.003	Chamber holding device for check device

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