Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Versuch "Gammaspektren II - Halbleiterdetektoren" im Fortgeschrittenen-Praktikum


dr Marzieh Bahmani, marzieh.bahmani (at)


Experiment duration: approx. 7 hours

Start of experiment: 09:00

Labor location: Room 2'203


Contact the experiment supervisor in advance to arrange an appointment for the pre-test.

A prerequisite for participants is knowledge of nuclear and particle physics as well as solid state physics. Please also take note of the literature listed below. The experiment can only be carried out if you have familiarized yourself with the topics mentioned below and can prove this in the preliminary test which will be held one day before the experiment via zoom.


Please be informed that this course is in English

Short description

For modern elementary particle experiments such as the LHC, electronically readable detectors are inevitable. Large amounts of data can only be measured, stored, processed and made accessible worldwide when the electronic signals are easily digitized. In this experiment, the basic mode of operation as well as the typical properties and parameters of such a detector are to be conveyed using the example of the semiconductor detector. When carrying out the experiment, the focus is particularly on the typical methods in experimental particle physics for obtaining and analyzing the data.


First, spectrum of natural radioactive material is recorded. Then gamma sources of known emission lines and activities are measured in order to calibrate the detector. The aim of the experiment is to determine the absorption coefficients of various metals as well as to measure the characteristics of the detector. The data will be available as spectra in ASCII format. you are required to write a program for the evaluation of data which can read it in and fit the peaks. Which programs are used - whether evaluation or graphical representation - is up to you.


The experiment takes place in room 2.203. Read the experiment instructions HLD file carefully and familiarise yourself with the following terms. Selected literature extracts are made available to you for this purpose. Bibliography for more in-depth studies can be found below.

A) Gamma spectroscopy:
  • Generation of gamma radiation through radioactive decay
  • Interaction of gamma quanta with matter (dependence on gamma energy, material properties)
  • characteristic effects in spectra measured by gamma detectors and their causes (e.g. Compton edge, "escape peak", backscatter peak)
B) semiconductor detector:
  • Functional principle of semiconductor detectors (including solid-state physical fundamentals such as band model, etc.)
  • Structure of the coaxial HPGe
  • Contributions to energy resolution and its physical causes, causes of detector ineffciencies, peak-to-Compton ratio
  • Dependence of the energy resolution and detector effciency on the gamma energy and detector parameters
C) Applications:
  • Basic terms of dosimetry (units of measurement and their meaning)
  • Sources of natural radioactivity
  • Mass absorption coeffcient (depending on gamma energy and material properties)
D) data evaluation:
  • Methods of quantitative evaluation of gamma spectra (determination of energy and intensity of spectral lines), consideration of background spectrum, fit of any functions on data.
  • Statistics for radioactive decays and counting experiments, handling of statistical errors


Please bring a USB stick with you to transfer the recorded spectra to your computer.

Materials and Report

  Documents on the experiment

  1. Manual for the Maestro program, which takes on the tasks of data acquisition, in particular that of a multi-channel analyzer (MCA: Multi Channel Analyzer) and the control of the hardware parameters of the semiconductor detector. .
  2. Location instructions with the most important operating instructions as well as a list of gamma sources with details of the most important emission lines

Useful links (but not required):

  1. Grafische Darstellung mit matplotlib Jupyter Notebook
  2. Python und PyROOT Tutorial
  3. Graphic evaluation program Root

The evaluation can be carried out in a program of your choice . Prior consultation with the supervisor is recommended. 


The Report must be submitted no later than two weeks after the experiment has been carried out. If by e-mail, then please be sure to use it as a PDF file !!



In addition to the selected excerpts from the literature that are made available, the following literature is suitable for preparing the experiment and for deepening knowledge:


  • C. Grupen: “Teilchendetektoren” (Wissenschaftsverlag, 1993)
  • Th. Ferbel: "Experimental Techniques in High Energy Physics" (Addison Wesley, Advanced Book Program, 1987)
  • Glenn F. Knoll: “Radiation detection and measurement” Second edition (John Wiley & Sons, 1989)
  • W.R. Leo: “Techniques for Nuclear and Particle Physics Experiments” Second revised edition (Springer-Verlag, 1994)
  • J.R. Taylor: "An Introduction to Error Analysis", Second edition (University Science Books, 1997)
  • Literaturwerte:


  1. for point A) und B)
    • Knoll, Kap. 12.

    • Grupen, Kap.1.2
  2. for Point B)
    • Grupen, Kap. 7.1
    • Ferbel, Part III ("High Resolution Electronic Particle Detectors") chap. 4. (pg 233ff)
    • Leo, esp. Cape. 10.1 - 10.4, 10.7
  3. for point C)
    • Knoll, chap. 20
    • Groups, Chapter 3 and Glossary 3
    • Leo, chap. 3
    • Knoll, Kap 2.III.B or a book on nuclear physics of your choice (on the term mass absorption coefficient)

  4. for point D)
    • Leo, chap. 4.

    • Taylor, esp. Cape. 3 and 11