Gamma Spectrometry Internship

General
Objective
Preliminary Remarks
    Procedure of the Practicum
    Preparatory Work
Gamma Spectrometry
The Scenario
Your Tasks
Carrying Out the Measurement
    Note
    Preparation
    Starting LVis
      Notes on the Gamma Spectrometry Program LVis
      Interrupting LVis
      Exiting LVis
      Exiting the Program Page
    Configuration of the Measurement System
    Selecting and Configuring Detector
    Energy Calibration
    Efficiency Calibration
Measurement
Evaluation
Conclusion of the Practicum

General

Your supervisor will introduce you to the topic of gamma spectrometry during a brief tour of the relevant facilities at RCM.

To carry out the measurements, you will use an online measurement station available 24/7. Access to this requires a username and password, which you should request in advance via email before the planned start of your practicum (see below).

You will use a professional gamma spectrometry program for measuring and evaluating the measurement data. Short video tutorials will help you familiarize yourself with the program's functions.

Objective

You will learn how radioactive samples are identified and quantified using gamma spectrometry. By examining a fictional scenario, we aim to relate this to - admittedly unusual - reality.

By the end of the practicum, you should be able to independently carry out a (simple) gamma spectroscopic measurement and analyze the data. You can further deepen these skills with your online access on different samples and various detector systems in the future.

Preliminary Remarks

Procedure of the Practicum

The practicum will be conducted online and therefore requires some preparatory work on your part.

Preparatory Work

Send an email with your name, matriculation number, and (TUM) email address at least three working days before your planned start of the Gamma Spectrometry Practicum to the address This email address is being protected from spambots. You need JavaScript enabled to view it..
- Following this, we will create access for you to use programs in the Webportal and upload the required files (e.g., calibration spectra) into your personally assigned practicum folder.
- You will then receive an email with your access password. This is personal assigned and must not be shared. Use your matriculation number prefixed with a p (e.g., p123456) as your username.If another person is interested in using the program and/or conducting measurements, we will be happy to provide them with their own access account upon registration via the corresponding link on EducTUM.de.
- With your access data, you can conduct the practicum at any time, potentially interrupting it and continuing later.
Familiarize yourself with the basics of Gamma Spectrometry.

Gamma Spectrometry

This section discusses the fundamentals for carrying out the Gamma Spectrometry Practicum or provides cross-references to relevant information sources.

You should be able to answer the following questions using the listed links or other information available to you:

What is meant by radioactive decay?
What is meant by gamma spectrometry?
What types of gamma detectors are there and how do they work?
- In particular, consider the functionality of NaI and HPGe detectors.
- What are the essential differences between the two types of detectors?
For conducting measurements and evaluations, the gamma spectrometry program LVis is used in this practicum.
- You must first log in to use the program (see preparations).
- There are a series of short video tutorials
  Recommendation: Please view the recommended tutorials below calmly before beginning the practicum.
  - Overview of the Configuration Area
  - Reference Sources
  - Creating a New Detector

The Scenario

Fig. 1.1 Rear-end collision of a car with a school bus.

In a traffic accident in Hogwarthshofen, a car rear-ended a school bus.
There were no serious injuries among the passengers of the bus or the driver of the rear-ended vehicle.
However, the driver of the car fled the scene of the accident.
The emergency services from the police and fire department, called to the scene, conducted a closer inspection of the car after attending to the students and the bus driver.
The fire department also used a dose rate measurement device for this purpose.
An increased dose rate was detected in the trunk area.

Fig. 1.2 Dose rate measurement at the opened trunk of the car by a fire department member.

After opening the trunk, a shipping piece with (possibly) radioactive content was found, as a direct measurement of its surface with a mobile radionuclide identification device (RID) indicated.

Fig. 1.3 Shipping piece (top) found in the trunk with (possibly) radioactive content. The dose rate is being measured with a mobile radionuclide identification device (RID).

The accident site was subsequently secured by the fire department and the relevant authorities were informed about the (possible) discovery of a radioactive source.

Fig. 1.4 Secured accident area with emergency vehicles and personnel.

The competent authority, in Bavaria for example the State Office for the Environment (LfU), has sent you as the on-call duty officer with an emergency vehicle to the accident site to gather more information regarding the (possibly) radioactive find.

Your Tasks

Upon your arrival at the scene, you should answer the following questions with the measurement equipment available to you (the detector to be used will be communicated to you by your supervisor during the introduction):

Is there actually radioactive material present?
If so, which radioactive substance(s) are involved?
What activities do the (possibly) identified radioactive substances have?
Is there a violation of the transport law that needs to be pursued?

Carrying Out the Measurement

Note

There are various detectors available for carrying out the measurement. The detector to be used will be communicated to you by your supervisor during the introduction. The images shown below were created with a NaI detector. The steps to be carried out for other detectors are analogous.

Warning: If your PC goes into sleep mode during the measurements, then the measurements will be aborted and the measurement data will be lost!

Recommendation: Disable sleep mode before starting measurements and consider re-enabling it afterward.

Preparation

Keep dhe certificate of the calibration source ready for your first use of LVis (it was given to you during the introductory session). You will need the data contained within to create a reference source, with which the provided calibration spectrum was measured.

Starting LVis

Follow these steps.

Open the section Programs in EducTUM (alternatively, directly open the access in the browser by calling prgr.eductum.de the login page).
Log in with your personally assigned user data.
Click on the icon LVis under currently available applications.
A connection to the server at RCM will be established and the program LVis will open.
If you are using LVis for the first time, it will appear with mostly empty windows

Notes on the Gamma Spectrometry Program LVis

There are numerous software programs from various manufacturers and providers available for the evaluation of gamma spectrometric measurements. Open-source applications are also available. Most programs are file-based, meaning they repeatedly apply the various analysis steps to the measured spectrum file and the results are stored in separate result files. This often makes sustainable storage of measurement data along with the analysis results problematic or requires additional programs that consider the various assignments (spectrum, calibration, used nuclide data).
For this practicum, we have chosen LVis for two reasons:

LVis is integrated into the EducTUM website and is fully available for the practicum.
LVis is a parameter-based spectrometry program, meaning all information (measurement data, analysis data, etc.) is stored together and transparently. This makes it particularly valuable for the traceability of practicum results.
LVis is a gamma spectrometry program used worldwide by various institutes and companies. Therefore, it could happen that LVis comes across your path in your professional life - and then you will be (almost) an expert in it.

Interrupting LVis

You can interrupt your work with LVis at any time. Your results created so far are saved in a personally assigned folder.
To exit LVis, use File/Exit. If results have not yet been saved, you will be prompted to choose where to save them. Confirm the proposed directories and file names.

Exiting LVis

When you finish your work with LVis, close the program via File/Exit. This is the only way to ensure that your current work is saved and will be available again on the next call.

Exiting the Program Page

After closing LVis - and if no other program is to be used - you also need to exit this page. For this, press the button Please log out.

Configuration of the Measurement System

Before a measurement can be carried out with a measurement system, it must be configured. This includes details about the detector system as well as its calibration (energy, efficiency).

When LVis is used for the first time, the explorer for configuration settings is displayed on the left side. It should only contain the entry Buffer (the lower left area allows switching between different displays using buttons).
Since a suitable gamma radiation detector is needed for measurements, it must be included and configured first.

Selecting and Configuring Detector

1. 1. 1. Right-click in the white configuration area (not on the Buffer entry!). A selection window opens, in which new detector is clicked.All currently available detectors are displayed. Please choose the detector specified by your supervisor for the practicum.
  2. The selected detector's name will now appear in the configuration explorer, marked with a red exclamation mark. The latter indicates that the detector has not yet been configured.
  3. To configure the detector, right-click on the detector's name and select Detector Configuration from the menu that opens.
  4. A window opens for entering the specific detector data.
  - - In the left section, select the detector type. By clicking the Details button, further information about the detector used can generally be entered. However, this information is not needed for the practicum.
    - In the right section, further details about the electronics of the detector system can be provided. It is important here to click on the Details button. In the window that opens, the following inputs must be made (Practice Question: what are the implications of the individual settings?):
    - - Gain of the amplifier (Gain): 1
      - Number of channels of the multichannel analyzer (Channels): 1024 for NaI and LaBr₃, 16,384 for HPGe
      - Enabling the high voltage (the voltage of the detector is fixed here)
  After applying the inputs, the detector will start. This is indicated by the now missing red exclamation mark in the configuration explorer.
  Energy Calibration
  The detector electronics deliver a pulse height spectrum as a result of the measurement. Knowledge of the association of channel number to energy is essential for identifying radionuclides. This association is established with energy calibration. (Note: In practice, energy calibration should be verified and documented at regular intervals (typically at least weekly) or in case of anomalies).
  1. To perform energy calibration, the data of the used calibration source(s) are required. If these have not yet been created in LVis (e.g., during one of your earlier uses of LVis), they need to be newly created in the Reference Sources section.
    1. Right-click in the file explorer Reference Sources, click on New Reference Source, and assign a unique name to the reference source (Suggestion: QCR310_19911201).
    2. In the window Reference Sources identify and enter the certificate of the calibration sources Reference Date and Time. Select Sample as the reference quantity unit.
    3. Now add all the gamma reference sources listed in the certificate by clicking the Add Nuclide button. Use the nuclide library Practikum_Cal.Lib stored in LVis and select the corresponding characteristic lines of the respective nuclides. Enter the activities and uncertainties in the table. Pay attention to the units!
    4. After applying the inputs with OK, the reference source will appear in the reference sources explorer (if necessary, restart LVis without deleting previous data!).
  2. After these preparatory works, the actual energy calibration can be carried out. For the execution of the energy calibration (and also the subsequent efficiency calibration), a previously measured calibration spectrum is available to you. The measurement of this calibration spectrum is carried out in practice analogously to the measurement of an unknown sample, with the significant difference that the data for the sample in this case are already known from the certificate of the calibration sources.
  3. After right-clicking on the detector in the configuration explorer and selecting Energy Calibration from Spectrum File, a window opens where you select the file amcsco_2025_11_24_2h_xx.chn (the designation xx stands for the chosen detector: nai, labr, dx1). If the files are not displayed, check whether Ortec CHN file *.chn is set and whether the correct directory (.../Measurements or a subdirectory of .../Measurements (e.g., Measurements /NaI-Osprey) is selected (the directory varies depending on the practicum).
  4. After confirming the selection, a new tab titled EnKal_2...... will be created, displaying the calibration spectrum. By clicking on the axes, the representation of the spectrum can be adjusted. A logarithmic representation is recommended for the pulse axis.
  5. To complete the information about the measurement, additional information will be stored in the other tabs
    - Sample Data
      - Select the calibration source (designation chosen by you for this)
      - No further information is required here
    - Sample Geometry
      - for the type under Container, select Point (source) (see certificate)
      - No further information is required here
    - other tabs
      - no further information required
  6. Click on the Calibration Editor button at the bottom left of the Spectrum tab. A table will open showing the calibration data you will subsequently need to determine. Energy must be selected at the bottom left.
  7. Now open the Spectrum tab. The following steps must now be carried out for each visible peak in the calibration spectrum in succession. Generally, you begin from right to left, meaning that the peak with the largest gamma energy is considered first (Practice Question: which nuclide does it come from, what energy and transition probability does it have? Note: use a nuclide map (e.g., IAEA - Live Chart of Nuclides).
    - Select a peak and zoom in on the spectrum. Move the cursor over the peak area while holding the left mouse button down.
      Recommendation: First, familiarize yourself with the various zoom options for the spectrum using the mouse. Use both mouse buttons and the mouse wheel. Try the keys L (Logarithmic/Linear) and A (Autoscale) for different representations. Click on the energy or pulse axis for further display options.
    - The peak is now enlarged. Position the cursor at the maximum of the peak and click on Peak Editor in the table. A window will open with a fit (red curve) to the observed peak.
    - On the right side of the window, the peak data determined from the fit will be displayed (Note: Since no energy calibration has yet been performed, the data refer to the channels). To determine the associated nuclide, click on the button with the three dots and select the corresponding line from the list of possible characteristic lines of the reference source (Note 1: If the button with the three dots is not displayed, you probably did not execute Point 6. Note 2: Consider the transition probabilities). Transfer the selected line into the calibration. The energy scale of the spectrum will already adjust. The selection is confirmed using Transfer to Calibration.
    - Once all peaks have been considered, save your entries (using the button at the bottom right in the Spectrum tab). Choose "<detector name>/Calibrations/Energy" as the storage location (for "<detector name>" use the designation of your detector). Respond with Yes to the question Should the energy calibration be included in the detector?.
  The result of the energy calibration can be viewed in the Calibration/Library tab. The red curve shows the channel-to-energy association. The corresponding equation is at the bottom. Check if the calibration curve appears "plausible" to you. If necessary, repeat the energy calibration. Along with the energy calibration, a full width at half maximum calibration (blue curve) was performed. Discuss the course of the full width at half maximum curve. Does it make sense?
  Efficiency Calibration
  The activity of the sample can be determined from the areas of the peaks using suitable models, which depend on the type of object being measured, the specific measuring geometry, and other influencing factors. The energy-dependent efficiencies with which a detector detects gamma radiation are required for this. These are determined during the efficiency calibration from the spectrum already used for the energy calibration. The procedure is fundamentally similar to that of energy calibration.
  (Note: In practice, efficiency calibration must also be verified and documented at regular intervals (typically at least weekly) or in case of anomalies).
  1. Through Efficiency Calibration from Spectrum File in the configuration explorer, the calibration spectrum (AmCoCs_Prak.chn) is loaded again for the selected detector. A tab titled EffKal_2... opens and displays the spectrum.
  2. In the Sample Data tab, the used calibration source must be selected.
  3. Click the Calibration Editor button at the bottom left of the Spectrum tab. A table opens with the determined calibration data. Select Efficiency at the bottom right. For the "Fit" type, select Interpolative.
  4. Proceed for each peak in the same way as for the energy calibration: select the peak, open the peak editor, transfer to calibration.
  5. Finally, save the calibration data in the parameter data set Quality Assurance: Efficiency.
  The result of the efficiency calibration can be viewed in the Calibration/Library tab. The green curve shows the efficiency-to-energy association. Check if this calibration curve appears "plausible" to you.
  Measurement of the Unknown Sample
  The measurement is carried out in the same geometry as the efficiency measurement, meaning you also measure a (nearly) point-like source at the same distance from the detector as during the calibration measurements. This means that no corrections regarding measurement geometry, etc., are required for quantification.
  1. Open the Detectors tab. Note that the operation of the spectrum acquisition is performed using the vertically arranged buttons to the right of the spectrum display.
  2. Delete any existing spectrum data (Delete Spectrum)
  3. Start the spectrum acquisition
  4. Stop the spectrum acquisition (Only end the measurement after an adequately long measurement time! This is the case when the (various) peaks are clearly visible and with low "noise" in the spectrum).
  Evaluation
  To evaluate the recorded spectrum, please carry out the following steps:
  1. In the configuration explorer, right-click on the detector with which you performed the measurement (and calibrations!) and select new parameter set. Enter a (any) name for the parameter set (e.g., first evaluation) and set for Type Standard, for Measurement Time Live time and Evaluation ROI. Confirm with OK.
  2. A tab with the title Name @ Detector Designation will open in the right window. In the Sample Data tab, you must now enter additional information about the measured sample that will be used in the subsequent evaluation. In our case, the required information is limited to the Measurement Time (Live time), which you can obtain from the spectrum (Detectors tab) at the top right, and the Sample Mass, which must be set to 1 and refers to the unit sample (as point sources can be assumed for the measurements, a mass entry is not required here!). Note that Reference Date/Time is the date and time when you performed the measurement of the unknown sample.
    In professional measurement, you would include further details and information, such as the sample name and location, "unknown shipping piece from an accident vehicle" etc. With this documentation, it will always be traceable at a later time, which sample it was, where, and when the measurement took place, etc.
  3. In the ROIs tab, click on Calibration File. In the menu that opens, select Efficiency and choose the efficiency calibration file you determined. Leave all further entries unchanged (Note: we neglect possible contributions from the background here). The Unit of Activity is Bq. Now save the selected parameter set using the Save button at the bottom right. Only then will the parameter set, i.e., your efficiency calibration, be taken into account in the subsequent evaluation steps.
  4. In the configuration explorer, your parameter set has been integrated into the menu structure under the detector. Right-click on it and select Evaluate Current Spectrum. A new tab titled Spectrum will be created, displaying the measured spectrum. Are all peaks well-defined? If not, the measurement time was too short. In this case, you should continue the measurement).
  5. Now evaluate the spectrum: highlight all the peaks in the spectrum. To highlight a peak, move the mouse over the peak while holding down the Shift key. The highlighted area will turn red. Repeat this for all peaks in the spectrum. If you want to delete an area again, grab the right or left edge of the corresponding highlight with the mouse and move it over the opposite limit. When a "red waste bin" appears, release the mouse button. The highlight is deleted. In a corresponding manner, you can also move the limits.
  6. Open the ROIs tab. Select a suitable library file (for the practicum, use the file Practikum_Meas.Lib).
  7. There should now be the corresponding values entered for all marked peaks. Each peak must now be assigned the corresponding nuclide (Note: when using high-resolution detectors (e.g., HPGe), automatic assignment occurs, but it should be verified). For this, double-click in the Nuclides column in each row on the placeholder ???. The detector efficiency will be displayed in the appearing window.
    The nuclide assignment is made by clicking on .... A list of nuclides that have characteristic peaks in this area will open. To select the correct nuclide, use a nuclide map (e.g., IAEA - Live Chart of Nuclides) or nuclide libraries (e.g., http://www.lnhb.fr/Laraweb/). Consider the transition probabilities of the respective characteristic lines and that some nuclides have multiple characteristic lines (consider transition probabilities!).To assist you, here's a list of possible nuclides: Am-241, Ba-133, Co-60, Cs-134, Cs-137, Eu-152, Eu-154, Eu-155, Na-22.
    Select the nuclide, and if the nuclide has multiple characteristic lines in the highlighted area, select the corresponding characteristic line in the following window. Confirm your entries with OK.
  8. After you have made the assignments for all ROIs, click Evaluate Spectrum. In the ROI Results tab, the calculated values for activity, detection limit, and quantification limit as well as further information will appear for each nuclide.
  Having now identified and quantified the unknown sample, the final question is whether a criminal act exists in the aforementioned scenario that needs to be pursued. To compare the activities you determined with the corresponding exemption limits from Annex 4 Table 1 Column 2 of the Radiation Protection Ordinance. A violation of transport law would exist if the activity of a nuclide exceeds the table value. In the case of multiple nuclides, the sum formula should be taken into account.
  \[\sum^n_{i=1}\frac{A_i}{FG_i}\le 1\]
  (The sum of individual activities A_i divided by the exemption limit FG_i must be less than or equal to 1). Also consider the information on detection and quantification limits in your considerations, if necessary.
  Conclusion of the Practicum
  Send an email to your practicum supervisor (This email address is being protected from spambots. You need JavaScript enabled to view it.) with the subject "Practicum - your matriculation number) including the following information:
  - Is there actually radioactive material present?
  - If so, which radioactive substance(s) are involved?
  - What activities do the (possibly) identified radioactive substances have?
  - Is there a violation of the transport law that needs to be pursued?
  Note:
  We would greatly appreciate any criticism and/or comments you may have regarding the practicum. We strive to constantly improve the practicum and certainly need your feedback for this. Thank you very much!