524058 MCA Box
Overview
The MCA box is part of the CASSY-S system and together with suitable detectors (e.g. NaJ(Tl) scintillation counters, Si-semiconductor detectors) and in combination with Sensor CASSY (524 010USB), CASSY Lab (524 200) and a computer, it constitutes a multi-channel pulse-amplitude analyzer for a fast and easy recording of the spectra of radioactive decay products. The interaction mechanism in the detectors generates electrical pulses of various amplitudes which are proportional to the energy loss in the detector, unlike Geiger-Müller counter tubes. These pulses are converted to equivalent numerical values, and the Sensor CASSY adds these values together in channels which correspond to the numerical values. The resulting energy spectrum represents the probability distribution of the detected radioactive radiation in dependence on the energy. Consequently, an MCA is significantly different from a single-channel analyzer, which consecutively sweeps the entire spectrum using a small window (channel), and is thus less suitable for low activities. To demonstrate the difference in the experiment the MCA box can also be used as a single channel analyzer.
The MCA box contains a BNC input which allows the connection of external detectors, e.g. an NaJ scintillation counter (559 901) with detector output stage (559 912) or a semiconductor detector (559 92) or from (559 56) with discriminator-preamplifier (559 93). Additionally, their analog output signal can be observed by an oscilloscope using a BNC-T-adapter (501 091). The polarity of input signals and the amplitudes of different detectors can be adapted accordingly. The voltage supply for the discriminator pre-amplifier (559 93) and the detector output stage (559 912) can be obtained from the MCA box via a multi-pin socket. The detector output stage (559 912) allows the measurement of high voltage supply at the detector.
NaJ scintillation counters are particularly suitable for γ and β radiation, while Si-semiconductor detectors are appropriate for α and β radiation. For measurements with extremely weak radioactive sources (e.g. radioactively contaminated mushrooms, 137 Cs) the (lead) scintillator screening (559 89) with socket (559 891) can protect the scintillation counter (559 901) against the natural radioactivity of the environment.
The former detector output stages (559 91) and (559 911) can be placed at the MCA box, but they do not allow measurement of high voltage and mechanically they do not suit to the socket for the scintillator screening (559 891).
The software CASSY Lab (524 200) permits the recording of measured values (including high-voltage measurement), the display and evaluation of any spectra in parallel. Energy calibration occurs with one or two known energies and can be realized for each curve individually or for many spectra simultaneously. Integration of any spectrum sections (e.g. of photopeak), fit of Gaussian distribution, addition and substraction of spectra are possible for the evaluation.
The MCA box contains a BNC input which allows the connection of external detectors, e.g. an NaJ scintillation counter (559 901) with detector output stage (559 912) or a semiconductor detector (559 92) or from (559 56) with discriminator-preamplifier (559 93). Additionally, their analog output signal can be observed by an oscilloscope using a BNC-T-adapter (501 091). The polarity of input signals and the amplitudes of different detectors can be adapted accordingly. The voltage supply for the discriminator pre-amplifier (559 93) and the detector output stage (559 912) can be obtained from the MCA box via a multi-pin socket. The detector output stage (559 912) allows the measurement of high voltage supply at the detector.
NaJ scintillation counters are particularly suitable for γ and β radiation, while Si-semiconductor detectors are appropriate for α and β radiation. For measurements with extremely weak radioactive sources (e.g. radioactively contaminated mushrooms, 137 Cs) the (lead) scintillator screening (559 89) with socket (559 891) can protect the scintillation counter (559 901) against the natural radioactivity of the environment.
The former detector output stages (559 91) and (559 911) can be placed at the MCA box, but they do not allow measurement of high voltage and mechanically they do not suit to the socket for the scintillator screening (559 891).
The software CASSY Lab (524 200) permits the recording of measured values (including high-voltage measurement), the display and evaluation of any spectra in parallel. Energy calibration occurs with one or two known energies and can be realized for each curve individually or for many spectra simultaneously. Integration of any spectrum sections (e.g. of photopeak), fit of Gaussian distribution, addition and substraction of spectra are possible for the evaluation.
Technical Data
•Resolution: from 256 to 2048 channels (8-11 bits) per spectrum
•Storage depth: 2 x 109 events per channel (31 bit)
•Dead time: approx. 60 µs
•Energy linearity: < 3% of final value
•Coincidence window: 4 µs
•Operating limit for external sensors: 0.5 V to 5 V according to the adjustment of the attenuator, positive or negative. Internal attenuator and polarity adjustable via software.
•High-voltage measurement up to 1.5 kV in connection with detector output stage (559 912)
•Dimensions: 92 mm x 92 mm x 30 mm
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