 For HDR 192IR & LDR 192IR, 137Cs, 125I, 103Pd, 198Au, 241Am- Sealed: no air density correction
- New HDR catheter holding mechanism
- Ion collection efficiency: >99.8% (10 Ci 192IR)
- Leakage: <3fA
- High current output: 38 pA at 1 mCi 125I
The 44D is a hermetically sealed re-entrant well ionization chamber, requiring no air density corrections. The fill gas is pure argon at an absolute pressure of 23.5 psi, which provides three distinct benefits. First, through the photoelectric absorption, argon enhances the response at low energies emitted from 125I and 103Pd. Second, because of its low electron attachment coefficient, argon provides a higher ion collection efficiency making it more suitable for 10Ci HDR 192Ir sources. Third, the positive pressure provides long term constancy measurements with the ability to verify the chamber seal.
The 44D is fully guarded into the chamber and is equipped with a 1.5 meter triaxial cable. It may be connected to any precision dosimetry grade electrometer. To cover the entire range of clinical sources from 125I seeds to HDR 192IR, the electrometer should be able to measure up to 2000 nA or 20,000 nC and be capable of resolving at least 10fA.
Specifications
Active Volume: 1200cc
Response Factors:
Not to be used to calibrate source strength
|
241Am
198Au
137Cs tube
125I/6702
125I/6711
|
9.3nA/Ci
15.3nA/Ci
18.6nA/Ci
46.2nA/Ci
37.8nA/Ci
|
131I
192Ir/HDR
192Ir/HDR
103Pd
89Sr
|
11.6 nA/Ci
30.0nA/Ci
28.7nA/Ci
9.7nA/Ci
0.48nA/Ci
|
|
Axial Response: “Sweet spot” defined as ±0.5% of response, nominal length is 40 mm ±5 mm, center located between 36 mm and 46 mm from the bottom of the well
Ion Collection Efficiency: >99.8% with 10Ci of 192Ir
Leakage Current: Guard to collector, <3 fA
Background: 1 fA per 1µR of background radiation
Stability: <1% per year, long term
Maximum Bias: Guard to HV electrode, 600 V
Well Opening: 7.2 cm dia. x 16.7 cm D
Cable: 1.5 m triaxial terminated w/BNC-M
Dimensions: 5” dia. x 10” H
Weight: 5.7 lbs
|
