NE2581A Therapy Dosimetry Ion Chamber

Description

The 0.6 cm3 NE2581A ionization chamber is developed from the original design by Professor F. T. Farmer. It is constructed using a tissue equivalent inner electrode and thimble, with a detachable build-up cap that also protects the thimble. Careful guarding of the signal conductors and cable has ensured low post-irradiation leakage. The NE2581A is used throughout the world for the measurement of photon and electron beam dosimetry. This is particularly suitable for routine output checks of X-ray, Co60 and Linacs.

Product includes the ion chamber, detachable build-up cap, 10m cable, TNC plug and carrying case.

Physical Characteristics
Sensitive Volume: Sensitive Length:	0.56cm³ 24.1mm
Thimble materials: Inner diameter: Wall thickness:	Shonka A-150 6.3mm 0.36mm
Inner electrode: Length: Outer diameter:	Shonka A-150 20.6mm 3.0mm
Build-up cap: Wall thickness: Outside diameter Density:	Lucentine CH 5.61mm 18.6mm 1.06gm cm^-3
Stem: Outside diameter	8.62mm
Energy range for electrons: In suitable phantom (measures absorbed dose to water)	8.62mm

Specification
Sensitive Volume:	0.56cm³
Sensitivity for X-rays of 1mm Cu HVL	5.9 R.nC-1 350 R.min-1.nA-159 Gy.μC-1 3.5 Gy.min-1.nA-1
Energy range for X and gamma radiation: (a) Without build-up cap: (measures exposure)	100kV to 300kV
(b) With build-up cap: (measures exposure)	0.3MV to 2MV
(c) In suitable phantom (measures absorbed dose to water)	2MV to 35MV
Energy range for electrons: In suitable phantom (measures absorbed dose to water)	5MeV to 35MeV
Leakage current: Typical: Maximum:	5 x 10^-15A 1.5 x 10^-14A
Maximum exposure rate (approx) or 99% collection efficiency:
Polarising potential—250V	50 kR.min^-1, continuous 100 mR/Pulse, pulsed 50 Gy.min^-1, continuous 1 mGy/Pulse, pulsed
Polarising potential—400V	130 kR.min-1, continuous 150mR/Pulse, pulsed 1.3 kGy.min-1, continuous 1.5 mGy/Pulse, pulsed