Ametek ORTEC radEAGLET, Руководство пользователя

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C Technological Background, Limitations
C.1 Stabilization
The primary spectroscopic detector of radEAGLET is the NaI scintillation crystal. This crys-
tal produces light pulses whenever gamma photons interact with the crystal material. The
light pulses are very weak so they must be amplified. Therefore, the NaI crystal requires a
photo-multiplier tube (PMT) which is coupled to the crystal. This assembly allows the inci-
dent gamma photons to be digitized by the internal electronics, and the pulses (which are
proportional to the energy of the incident gamma rays) form a histogram or gamma spec-
trum. This spectrum is stored in the embedded multi-channel analyzer.
The response of both the NaI detector and the PMT may vary based on measurement con-
ditions such as temperature or magnetic field. The peaks in the gamma radiation spectrum
may shift due to these temperature variations. As temperature changes are encountered,
modern scintillation based instruments must apply some means of stabilization. Shown be-
low is the procedure the
radEAGLET uses to correct for peak shifts and to adjust the peaks
in the spectrum to their scientifically correct positions.
C.1.1 Initial Stabilization
Each time the system is turned on, during the start-up the radEAGLET performs an initial sta-
bilization. This process takes about 80 seconds. It runs temperature checks and searches
for known peaks in the spectrum. It is strongly advised not to have check sources in the
immediate area during this initial phase, because this can confuse the process.
C.1.2 Continuous Temperature Monitoring
During the manufacturing process, each radEAGLET is tested in a climate chamber to learn
the individual temperature dependencies of crystal and PMT. Both the absolute value of the
temperature as well as the temperature gradients are used in this process. In the field, the
instrument continuously monitors and adjusts the gain by measuring the temperature. It
also distinguishes between slow temperature drifts and quick temperature shocks.
C.1.3 Continuous Spectroscopic Adjustments
Although there is not always an actual source present, the natural background spectrum
often contains valuable information. The
radEAGLET uses the natural background peaks
for an advanced stage of self-stabilization. When turned on, the radEAGLET is automati-
cally taking background spectra and analyzing them. All this happens automatically in the
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