Semiflex Ionization Chamber 31010

Standard therapy chamber for scanning systems and for reference dosimetry

Waterproof, semiflexible design for easy mounting in scanning water phantoms
Minimized directional response
Sensitive volume of 0.125 cm³, vented
Point dose patient QA with RUBY

The 31010 semiflexible chamber is the ideal compromise between small size for reasonable spatial resolution and large sensitive volume for precise dose measurements.
This makes the 31010 chamber to one of the most commonly used chambers in scanning water phantom systems.

The chamber volume of 0.125 cm³ gives enough signal to use the chamber also for high precision reference dose measurements.

The sensitive volume is approximately spherical resulting in a flat angular response and a uniform spatial resolution along all three axes of a water phantom.

Type of product	vented cylindrical ionization chamber
Application	reference dosimetry in radiotherapy beams
Measuring quantities	absorbed dose to water, air kerma, exposure
Reference radiation quality	⁶⁰Co
Design	waterproof, vented, guarded
Direction of incidence	radial
Nominal sensitive volume	0.125 cm³
Nominal response	3.3 nC/Gy
Long-term stability	≤ 1 % per year
Chamber voltage	400 V nominal, ± 500 V maximal
Polarity effect at ⁶⁰Co	< 2 %
Reference point	on chamber axis, 4.5 mm from detector tip
Photon energy response	≤ ± 2 % (140 kV ... 280 kV)
	≤ ± 4 % (200 kV ... ⁶⁰Co)
	≤ ± 5 % (50 kV ... 150 kV)
Directional response in water	≤ ± 0.5 % for rotation around the chamber axis and for tilting of the axis up to ± 10°
Leakage current	≤ ± 4 fA
Cable leakage	≤ 1 pC/(Gy·cm)

Materials and measures

Wall of sensitive volume	0.55 mm PMMA, 1.19 g/cm³
	0.15 mm graphite, 0.82 g/cm³
Total wall area density	78 mg/cm²
Dimensions of sensitive volume	radius 2.75 mm
	length 6.5 mm
Central electrode	Al 99.98, diameter 1.1 mm
Build-up cap	PMMA, thickness 3 mm

Ion collection efficiency at nominal voltage

Ion collection time	121 μs
Max. dose rate for
≥ 99.5 % saturation	6 Gy/s
≥ 99.0 % saturation	112 Gy/s
Max. dose per pulse for
≥ 99.5 % saturation	0.5 mGy
≥ 99.0 % saturation	1.0 mGy

Ranges of use

Chamber voltage	± (100 ... 400) V
Radiation quality	140 kV ... 50 MV photons
	(10 ... 45) MeV electrons
	(50 ... 270) MeV protons
Field size	(3 x 3) 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
T48002.1.004	Chamber holding device for check device
T40072.1.160	RUBY detector holder T31010

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