NE2581A Therapy Dosimetry Ion Chamber
NE2581A Therapy Dosimetry Ion Chamber

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

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