IEC 62372 pdf – Nuclear instrumentation – Housed scintillators – Test methods of light output and intrinsic resolution

IEC 62372 pdf – Nuclear instrumentation – Housed scintillators – Test methods of light output and intrinsic resolution
4Test methods of basic parameters of housed scintillators4.1 General
4.1.1 Test conditions
Measurements shall be made under normal conditions,unless otherwise specified in thespecifications of the manufacturer of housed scintillators.
Measurements should start at least 0,5 h after the last device has been switched on，unlessotherwise specified by the manufacturer specifications.
Before measuring, the housed scintillator and the PMT is kept under high voltage for the time
necessary for getting to the operation condition. Before measuring，the PMT is kept underhigh voltage for the time necessary for getting to the operation condition.
All parameters are measured during the complete blackout of the housed scintillator and PMT.
Optical contact between the housed scintillator and the PMT is provided by the materialspecified in the manufacturer specifications of the housed scintillator.
For the measuring,the following condition of choosing PMT should be reached: the workingpart of the photocathode shall overlap the output window of the scintillator.
lt is allowed to apply a light guide or an assembly of several PMT, if technical characteristicsand use conditions of light guide or assembly are specified in the specifications.
The measured housed scintillator is mounted on the PMT photocathode by optical contact,unless otherwise is specified in the manufacturer’s specifications.
lt is allowed to place a source of ionizing radiation inside the light protective chamber.PMT voltage should correspond to its attached data for operation conditions.
The spectrum of pulse height should be measured to define operation conditions of theassembly.
4.1.2 The sources of ionizing radiation
Enclosed radioactive sources of alpha-,beta-，gamma-，X- and neutron radiation with knownenergies should be used. The source of radiation shall be selected depending on theapplication of measured housed scintillator according to Table 1.
For measurements with the alpha- or beta-radiation sources, they should be placed directly onthe entrance window of the housed scintillator.
For measurements with the alpha- or beta- sources, it is allowed to use a single-hole or multi-hole collimator with a hole diameter less than the thickness of the collimator.
4.1.3 The assembly test conditions
The current of the divider should exceed the PMT average anode current more than 10 times.
PMT power supplies shall provide high voltage stability better than 0,05 % and divider currentmore than 0,5 mA.
At low-resistance inputs of subsequent stages of the measurement section the measurementsmay be performed without matching stage.
For a recording device providing a pulse heights spectrum suitable for further processingmulti-channel pulse analyzers，which have an output recording device of any type thatregisters and allows to give the pulse height spectrum in form convenient for processing,should be used.
4.2Test methods of nonlinearity and instability of the assembly4.2.1 Nonlinearity measurement
4.2.1.1General
The dependence of the pulse height (Vout) at the output of the assembly on the signal ( Vin) atthe input of the assembly (assembly conversion response) is defined according to formula:
where
k a is the assembly conversion factor;
V o is the initial point of assembly conversion response.
If conversion response of the housed scintillator is linear, the assembly conversion response with the housed scintillator is also linear:
Then
Vo = Vo+Va = Vo+ ax eps,
is energy lost by ionizing particle in the scintillator;
ais the assembly conversion factor with the housed scintillator;
Vodis the initial point of assembly conversion response with the housed scintillator;Vdis the initial point of housed scintillator conversion response;
epsis the initial point of housed scintillator conversion response, in energy units.