microSilicon

Silicon Detector for Small Photon and all Electron Fields

THE silicon detector for small photon fields
Unshielded diode, perfectly suited for electrons
Excellent dose stability (@6MV only 0.1%/ kGy)
Very small detector to detector variation
Very low dose per pulse dependence
Very small sensitivity variation with temperature
Improved water equivalence

Small field output correction factors should be applied when performing small field measurements. The small magnitude of these factors increases with decreasing field size. Additionally, the detector to detector variation of the microSilicon is almost negligible, which provides a sound basis for reliable small field correction factors. The new detector shows only a small loss of response over accumulated dose. The new design results in a very small water equivalent window thickness. This has positive effects on the output factors, the small field correction factors and the location of the effective point of measurement, which is now closer to the detector surface. Additionally, the profiles scanned by the micoSilicon are very close to a theoretical true profile.

Type No.	60023
Detector type:	p-type silicon diode
Measuring quantities:	absorbed dose to water
Nominal sensitive volume:	0.03 mm³
Reference point:	on chamber axis, 0.9 mm from chamber tip Photons: corresponds to the effective point of measurement Electrons: effective point of measurement is 0.3 mm from tip
Direction of incidence:	axial
Nominal response:	19 nC/Gy
Temperature response:	typical ≤ 0.1 %/K, maximum ≤ 0.3 %/K
Directional response:	≤ ± 1 % for rotation around the chamber axis ≤ ± 1 % for tilting of the axis up to ± 20°
Bias voltage:	0 V
Entrance window:	0.3 mm RW3, 0.01 mm Al, 0.48 mm epoxy
Total window area density:	92 mg/cm²
Water-equivalent window thickness:	0.9 mm
Sensitive volume:	radius 0.75 mm, thickness 18 μm
Outer dimensions:	diameter 7 mm, length 45.5 mm
Radiation quality:	(6 ... 25) MeV electrons; 60 Co ... 25 MV photons
Field size:	(1 x 1) cm² ... (40 x 40) cm² for electrons (1 x 1) cm² ... (10 x 10) cm² for photons
Small fields*:	down to 0.4 cm

* This detector is well suited for measurements in small and very small fields. Please note that for high accuracy measurements any detector may need correction factors in small fields. The small field size limit is provided as equivalent square field size following the methodology of IAEA TRS483:2017. In accordance with TRS483, the smallest field size considered is 0.4 cm.

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