IEC 62088:2001 pdf download
IEC 62088:2001 pdf download.Nuclear instrumentation – Photodiodes for scintillation detectors – Test procedures.
5 Physical characteristics
5.1
Active area, A
The active area of a PD, which is the useful area, is usually slightly smaller than the overall
area of the semiconductor wafer. This is due to the packaging or to the electrode or to the
protective layer on the junction edge, which may be needed in order to minimize the leakage
current (and consequently the noise).
Measurement of the active area shall be carried out, as shown in figure 2, by scanning the
overall area of the PD placed in total ambient darkness with a collimated beam of incident
light from a high stability reference light source.
The PD shall be biased and connected to a picoammeter using a conventional set-up as used
for semiconductor detector leakage current measurement or current-voltage characteristic
plotting (see IEC 60333).
Both the spot dimension on the surface of the PD and the scanning step in any direction shall
be less than 1/20 of the largest dimension of the semiconductor wafer and, in all cases, less
than 0,5 mm (see examples on the right of figure 2).
For each scanning path, the measured photocurrent of the PD is plotted as shown in figure 2
and a useful length, Xu is determined as the length of the path where the photocurrent is at
least equal to 90 % of its maximum value. The active area, defined as the area where the
photocurrent is at least equal to 90 % of its maximum value, is computed from all the
individual Xu determined for each scanning path. The computation details shall be stated.
The active area may depend on the wavelength of the scanning light. Consequently, the
active area shall be determined for several wavelengths in the useful spectral domain of the
PD. The measurement shall be made at least for the maximum responsivity wavelength入p
using a monochromatic or filtered light source emitting at入p t 50 nm.
The active area may change slightly with the bias voltage. A measurement shall be carried
out at least at the nominal bias voltage Uon: The bias voltage shall be stated for all
measurements.
For APDs, the active area may change significantly with aplied voltage. as the multiplication
factor may change slightly at different points of the device. Consequently, the active area for
G = 1 should also be determined and stated.
This measurement can also apply to photodiode arrays (PDAs) by summing the active areas
of the elementary PDs.
For the nominal bias voltage jbn’ the leakage currenter shall be stated at least at normal temperature, which shall be given, and at Tm
6.4 Rise time
The measuroment method described in IEC 60333 is applicable.
a) pholodiode alone
b) photodiode scintillation detactor.
C) photodlode ooupled to an amplifier.
d) photodlode scintillation detector coupled to an amplifier
6.5 Preamplifiers and amplifiers used with photodiode scIntillation detectors Preamplifiers and amplifiers used with photodiodes coupled to scintillators for nuclear radiation detection are of the same type as those used with semiconductor detectors. The measurement methods described In IEC 61151 are applicable.
6.6 Noise and resolution measurements
The measurement methods described in IEC 60333 and IEC 61151 are applicable.
6.7 GaIn of avalanche photodlodes (G)
6.7.1 General
The gain of an avalanche photodiode (APD) is the ratio of the photocurrent measured at a given voltage where multiplication takes place to the photocurrent measured at low voltage without multiplication, for constant Incident optical power.
The gain of an APD is strongly dependent on the bias voltage and also on temperature. particularly near the breakdown voltage,
The manufacturer of the APD shall give (see clause 8 — data sheet):
a) the maximum voltage Ubmae (or maximum gain) at which the APD can be operated:
b) a plot of the gain as a function of bias voltage or. if a nominal voltage 0bfl recommended, the slope G!tU around
C) the dependence of the gain on the temperature, at least for U and Ubmaz.
6.7.2 Measurement
To determine the gain of an APD for scintillation detection two methods may be used for measuring the ptiotocurrent as a function of voltage:
a) the general method of measuring the d.c. photocurrent with constant illumination, or
b) a pulsed light method, which uses the traditional nuclear spectrometry, pulse amplification and analysis system.
