ORTEC RADEAGLET, Руководство пользователя

Страница: 50 / 60

uses this information to make an automatic calibration adjustments. In many cases, the most prominent
peak to do this is 1460 keV associated with natural potassium
40
K. In addition to
40
K, there are other
peaks (natural and/or non-natural) used by this instrument to create a superior stabilization process.
B.2 Effective Range Of Measurement
Detection and identification depend on the dose rate on the detector surface. This value can be defined
by either varying the distance of the source and detector or by simply using stronger or weaker sources.
The RADEAGLET measures spectra from 15 keV up to 3 MeV.
B.3 Determination of the Full Width at Half Maximum
RADEAGLET detectors have a specified FWHM, sometimes also denoted as resolution given in percent-
ages relative to their peak position. Our usual reference is the
137
Cs peak at 661.6 keV. It is the common
peak to specify a resolution. The procedure used to determine this value is given as follows:
1. Acquire a background spectrum.
2. Acquire a
137
Cs spectrum with at least 1 µSv/h at the detector surface.
3. Use a qualified background subtraction method to subtract the background from the cesium spec-
trum.
4. Perform a Gaussian fit on the peak data (using e.g. Matlab).
5. Locate both positions where the Gaussian curve reaches the half of its maximum.
6. Calculate the difference in terms of energy. The latter is the FWHM.
For sodium iodide based instruments, we specifiy a resolution better than 7.2 % at 661.65 keV which
corresponds to a FWHM of 47.6 keV.
B.4 Over-Range Characteristics for the Scintillator and the Nuclide
Identification
Nuclide identification results depend on the quality of the spectrum. For extremely high count rates, the
scintillation spectrum degrades and for dose rates greater than 200 µSv/h at the detector surface,
the RADEAGLET switches off the scintillation subsystem and uses the fall-back GM tube (included in all
RADEAGLET variants) for dose rate measurements.
A nuclide identification is possible in radiation fields up to 200 µSv/h. Though, a valid and precise ID is
only given if the limits of the
EASY-MODE ID are adhered to. Here, the instrument will clearly indicate,
whether an over-range situation exists or not.
Page 50 of 60 RADEAGLET User Manual• Software 2.1.16 • Document 1.32o • 2017-12-15 © innoRIID GmbH