Radiation Therapy
PinPoint
™
Ionization Chamber,
0.015 cm
3
, Waterproof
Model 30-350
•
Specifically designed for
stereotactic field measurements
•
Completely Waterproof
•
0.015 cm
3
volume
•
2 mm active diameter
•
5 mm active length
•
Directional dependence is better
than 0.5% when tilting the chamber
by ± 20 degrees
•
Open volume, vented
•
Fully guarded up to measuring
volume
•
Touchable parts free of high voltage
The 0.015 cm
3
PinPoint ionization chamber is specifically designed for stereotactic
field measurements. PinPoint is a waterproof cylindrical ion chamber ideally suited to
perform relative measurements in water phantoms or solid-state phantoms when superior
spatial resolution is required. The chamber is fully guarded up to its measuring volume
and open to the surrounding air via its 4.3 ft (1.3 m) cable and BNC Triax connector.
PinPoint has a short rigid stem for mounting and includes a PMMA buildup cap.
Specifications
Volume
0.015 cm
3
Response
4 • 10
-10
C/Gy
Leakage
± 4 10
-15
A
Polarizing voltage
Maximum 400 V
Cable length
4.3 ft (1.3 m)
Cable leakage
10
-12
C/(Gy cm)
Wall material
PMMA (C
5
H
8
O
2
), Graphite (C)
Wall density
1.19 gm/cm
3
(PMMA), 0.82 gm/cm
3
(C)
Wall thickness
0.56 mm PMMA, 0.15 mm C
Area density
79 mg/cm
2
Electrode
Steel, 0.18 mm Ø, 4.5 mm long
Nominal useful range
60
Co to 50 mV
Range of temperature
10º to 40ºC
Range of relative humidity
10% to 80%
Ion collection time
100 V:
80 µs
200 V:
40 µs
300 V:
20 µs
Saturation behavior
Saturation
behavior
Polarizing
voltage
99.0%
saturation
99.5%
saturation
Maximum dose rate at
continuous irradiation
100 V
145 Gy/s
74 Gy/s
200 V
585 Gy/s
290 Gy/s
400 V
2,340 Gy/s
1,160 Gy/s
100 V
1.3 mGy
0.6 mGy
Maximum dose rate
per irradiation pulse
200 V
2.6 mGy
1.3 mGy
400 V
5.0 mGy
2.5 mGy
See next page for more specifications.
Specifications
(continued)
5.0
Diagram
Ø 3 .4
4.5
Thimble
Ø 0 .8
Ø 2 .0
Ø 7 .0
3.4
Ø 6 . 9
6.95
49.7
Approximate dimensions in mm.
Drawing not to scale.
Buildup cap, PMMA
Ø 3 .7
Ø 9 .7
Spatial resolution
1
0.9
0.125 cc
PinPoint
Dia mon d
0.8
0.
7
0.6
Chart showing profiles of a 0.5 cm gap for 18 mV
photons at 3.0 cm depth in water:
Detector
T
ype
50% profile width, cm
0.5
0.125 cm
3
1.01
PinPoint
0.80
0.4
Diamond
0.70
0.3
0.2
0.1
0
-20 -15 -10 -5 0 5 10 15 20
Position (m m )
Available model(s)
30-350
PinPoint Ionization Chamber, 0.015 cm
3
, Waterproof,
includes BNC Triax connector, PMMA buildup cap, and 33 mm rigid
stem for mounting
Other types of triaxial cable connectors available
