Roos™ Electron Ionization Chamber, 0.35 cm³, Waterproof

Radiation Therapy

Roos ™ Electron Ionization

Chamber, 0.35 cm 3 , Waterproof

Model 30-332

• Designed as a standard chamber

for electron dosimetry

• Wide guard ring excludes

perturbation effects, even at low

electron energies

• Negligible polarity effect, < 0.5% at

10 MeV

• Energy dependence is only

influenced by the stopping power

correction, a type dependent

correction is not necessary

• Completely Waterproof

• Ideal for use in water phantoms or

suitable solid state phantoms

• Open volume, vented

The Roos chamber, a development from Dr. Roos of PTB-Braunschweig, is used as a

standard chamber for electron dosimetry. This chamber has a very wide guard ring to

exclude any perturbation effect, even at low electron energies. The polarity effect is

negligible. Energy dependence is only influenced by the stopping power correction, a

type dependent correction is not necessary. The chamber is waterproof and vented through

the connection cable. Roos includes a 3.5 ft (1.08 m) cable and BNC Triax connector.

Specifications

Volume 0.35 cm 3

Response 1 • 10 -8 C/Gy

Leakage ± 4 10 -15 A

Polarizing voltage 100 V recommended, maximum 400 V

Cable length 3.5 ft (1.08 m)

Cable leakage 3.5 10 -12 C/(Gy cm)

Wall material Acrylic (C 5 H 8 O 2 )

Wall density 1.19 gm/cm 3

Wall thickness 1.0 mm

Area density 119 mg/cm 2

Electrode Acrylic, graphite coated, 15 mm Ø

Guard ring 4 mm wide

Nominal useful range 2 to 25 MeV

Range of temperature 10º to 40ºC

Range of relative humidity 10% to 80%

Ion collection time

100 V: 0.37 ms

200 V: 0.13 ms

300 V: 0.07 ms

Saturation behavior

Saturation

behavior

Polarizing

voltage

99.0%

saturation

99.5%

saturation

Maximum dose rate at

continuous irradiation

100 V

2.6 Gy/s

1.3 Gy/s

200 V

11.0 Gy/s

5.2 Gy/s

400 V

42.0 Gy/s

21.0 Gy/s

100 V

0.5 mGy

0.2 mGy

Maximum dose rate

per irradiation pulse

200 V

0.9 mGy

0.5 mGy

400 V

1.9 mGy

0.9 mGy

See next page for more specifications.

Specifications (continued)

Diagram

Ø 4 4

Ø 15 .6 (el ec trod e)

Ø 1 6

4 (g u a rd ri ng )

Approximate dimensions in mm.

Drawing not to scale.

Ø 2 4

5.8

Directional dependence

The deviation of the response following tilting of the chamber by up to 10º at 6 and 20 MeV,

at the dose maximum in water, is less than 0.1%.

Optional accessories

Check Source, 90 Sr, 20 MBq (541 µCi) (Model 30-658)

Available model(s)

30-332 Roos Electron Ionization Chamber, 0.35 cm 3 , Waterproof,

includes BNC Triax connector

Other types of triaxial cable connectors available