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AlphaSpec-1K : Design and Experiments
CalibrationA standard Am-241 source with known energy of 5485 keV is used for applying a single pointcalibration. Multi peak sourcescan be used to apply calibrationwith up to 3 degree polynomials.
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241Am EnrichedSource
Channel Number
Channel: 496Energy: 5485 keVFWHM: 81 keV
Attenuation Experiments : At atmospheric pressure, Alpha particles are rapidlyattenuated. Students place the source at varying distances from the detector, andrecord the centroid channel to study this. Similarly, the effect of air pressure is studied by setting different levels of vacuum for a constant source-detector distance
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Channel Number
Channel Number vs Distance for 241Am
A
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Pressure (mBar)
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Channel number vs Pressure for 241Am
B
Channel Number
Non-Enriched Sources : Thorium Nitrate is easily available from chemical suppliers,and we can use electrolysis ( 20mA, 10 minutes for a 5gm/5gm aqueous solution ) to deposit a thin film of Bismuth-212 on lead foils used as electrodes. The short half life of Bi-212 (60.5 minutes) enables students to view the typical exponential decay curve within one lab session by studying the activity of the film deposited on the Anode. 212-Bismuth's decay chain involves two distinct alpha particle energies, with the highest known branching ratio of 66:34, and this can also be verified to better than 1% accuracy with our spectrometer.
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ΔI(t)
Time (t) in minutes
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Counts
8785
6062
Thin film in vacuum
Lead foil electrodewith 212-Bi deposited
Energy (keV)
212-Bi Spectrum
Rate of decay
Electrolysis
5gm THNO3in 5ml Waterapprox.
Lead FoilAnode
Lead FoilCathode
Connect toConstant Current Source