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Transcript of phylab/files/Gamma_spectrometer.pdf · PDF filePhon e: +49 -2233 -604 -0 · Fax:...

  • P6.5.5.4

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    Atomic and nuclear physics Nuclear physics γ spectroscopy

    Identifying and determining the activity of radioactive samples

    Description from CASSY Lab 2 For loading examples and settings, please use the CASSY Lab 2 help.

    C A

    S S

    Y L

    a b 2

    ( 2

    0 1

    2 -0

    9 -2

    7 )

  • CASSY Lab 2

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    329

    Identifying and determining the activity of weakly radioactive samples

    can also be carried out with Pocket-CASSY

    Safety note

    When handling radioactive preparations, in addition to the radiation protection regulations, state-specific require- ments and the regulations of the educational authorities are also to be observed, e.g. in the Federal Republic of Germany at the very least the radiation protection regulations (StrlSchV - Strahlenschutzverordnung) and the direc- tives on safety during school lessons. This applies even in cases where the preparation used in this experiment in itself does not require the nomination of a trained radiation officer.

    Since the used preparations produce ionizing radiation, the following safety rules must nevertheless be kept to:

    · Prevent access to the preparations by unauthorized persons. · Before using the reparations make sure that they are intact. · For the purpose of shielding, keep the preparations in their safety container. · To ensure minimum exposure time and minimum activity, take the preparations out of the safety container

    only as long as is necessary for carrying out the experiment.

    · To ensure maximum distance, hold the preparations only at the upper end of the metal holder.

    Experiment description

    The detection probability of the scintillation counter is determined at several γ energies with calibrating preparations. The γ spectrum of a weakly radioactive sample is recorded, and its radioactive components are determined.

    Equipment list

    1 Sensor-CASSY 524 010 or 524 013 1 CASSY Lab 2 524 220 1 MCA box 524 058 2 Marinelli beakers 559 88 1 Calibrating preparation Cs-137, 5 kBq 559 885

  • CASSY Lab 2

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    330

    4 Potassium chloride, 250 g 672 5210 1 Scintillation counter 559 901 1 Detector output stage 559 912 1 High-voltage power supply 1.5 kV 521 68 1 Scintillator screening 559 89 1 Socket for scintillator screening 559 891 1 PC with Windows XP/Vista/7

    Experiment setup (see drawing)

    The output stage of the scintillation counter is connected to the MCA box and to the high-voltage power supply. The scintillation counter is mounted in the socket from above with the lead screening. The preparation in the Marinelli beaker is placed above the scintillation counter.

    Carrying out the experiment

    Load settings

    · Fill 1 kg of potassium chloride into a Marinelli beaker and place it above the scintillation counter. · Record the spectrum with varying the high voltage until the full range of measurement is covered. · Remove the Marinelli beaker and insert the calibrating preparation Cs-137 · Record the spectrum · Make an energy calibration using the lines at 1460 keV and 662 keV in the two spectra. · Remove the preparation · Equally distribute the test substance in a Marinelli beaker, place the beaker above the scintillation counter, and

    record the spectrum of the sample.

    · Make a background measurement without preparation. The measuring time should be equal to that with the sam- ple.

    Evaluation

    The activities of potassium chloride (17 kBq/kg) and the Cs-137 calibrating preparation (approx. 5 kBq, see calibra- tion certificate, mind the half-life) are known. From the integrated counting rate below the lines of the two spectra the detection probability of the scintillation counter at 1460 keV and 662 keV can be determined for this particular geome- try.

    The background spectrum is subtracted from the spectrum of the sample. From the resulting spectrum and the previ- ously determined detection probability the radioactive contamination of the sample can be determined. The observed energies enable the radiating isotope in the sample to be determined, and with the detection probabilities just deter- mined, the quantity can be estimated.

    Remarks

    The NaI(Tl) crystal at the end of the scintillation counter is sensitive to mechanical damage. Be careful when inserting the Marinelli beakers and when setting up the lead screen.

    When making measurements with strongly radiating samples heed the display of the dead time and, if necessary, dilute the sample.

  • P6.5.5.5

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    Atomic and nuclear physics Nuclear physics γ spectroscopy

    Recording a β spectrum with a scintillation counter

    Description from CASSY Lab 2 For loading examples and settings, please use the CASSY Lab 2 help.

    C A

    S S

    Y L

    a b 2

    ( 2

    0 1

    2 -0

    9 -2

    7 )

  • CASSY Lab 2

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    331

    Recording a β spectrum using a scintillation counter

    can also be carried out with Pocket-CASSY

    Safety note

    When handling radioactive preparations, in addition to the radiation protection regulations, state-specific require- ments and the regulations of the educational authorities are also to be observed, e.g. in the Federal Republic of Germany at the very least the radiation protection regulations (StrlSchV - Strahlenschutzverordnung) and the direc- tives on safety during school lessons. The preparations used in this experiment are type approved according to StrlSchV (2001) or they are below the exemption limit and do not require approval. For this reason handling without express permission is possible.

    Since the used preparations produce ionizing radiation, the following safety rules must nevertheless be kept to:

    · Prevent access to the preparations by unauthorized persons. · Before using the reparations make sure that they are intact. · For the purpose of shielding, keep the preparations in their safety container. · To ensure minimum exposure time and minimum activity, take the preparations out of the safety container

    only as long as is necessary for carrying out the experiment.

    · To ensure maximum distance, hold the preparations only at the upper end of the metal holder.

    Experiment description

    The β spectrum of Sr-90 is recorded with a scintillation counter. The energy loss per path length dE/dx of the β parti- cles in aluminum is measured.

    Equipment list

    1 Sensor-CASSY 524 010 or 524 013 1 CASSY Lab 2 524 220 1 MCA box 524 058 1 Set of radioactive preparations 559 835 1 Na-22 preparation 559 865

  • CASSY Lab 2

    © by LD DIDACTIC GmbH · Leyboldstrasse 1 · D-50354 Huerth · www.ld-didactic.com

    Phone: +49-2233-604-0 · Fax: +49-2233-604-222 · E-mail: info@ld-didactic.de · Technical alterations reserved

    332

    1 Set of absorbers and targets 559 94 1 Scintillation counter 559 901 1 Detector output stage 559 912 1 High-voltage power supply 1.5 kV 521 68 1 Scintillator screening 559 89 1 Socket for scintillator screening 559 891 1 Stand rod, 47 cm 300 42 1 Leybold multiclamp 301 01 1 Universal clamp, 0...80 mm 666 555 1 PC with Windows XP/Vista/7

    Experiment setup (see drawing)

    The output stage of the scintillation counter is connected to the MCA box and to the high-voltage power supply. The scintillation counter is mounted in the socket from above with the lead screening. The acrylic glass tube is put over the scintillation counter within the lead screening. The preparation is place a few centimeters above the scintillation counter with stand material. The absorber plates are laid on the acrylic glass tube so that they are located between the detector and the preparation.

    Carrying out the experiment

    Load settings

    · Mount the Sr-90 preparation, and record the spectrum with . Set the high voltage so that the spectrum is not cut off on the right side.

    · For the energy calibration, mount the Na-22 preparation, and calibrate the energy axis with the 511 keV and the 1275 keV line. The Sr-90 spectrum extends to approx. 2000 keV.

    · It is recommendable to determine the background without preparation. · Mount the Sr-90 preparation once more, and see to it that there is enough space for the absorbers. · One after another record the spectra without absorber, with a 0.5 mm thick alumi