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Level: Intermediate

Cambio++: Spectrum Conversion & Analysis



Cambio was developed in response to a need of nuclear emergency response analysts everywhere to be able to quickly read gamma spectra data from any of a widely growing number of formats used by both commercial and government detector systems worldwide. As the number of manufacturers of nuclear detection instrumentation grows, so does the number of data formats that must be able to be read by emergency analysts. Manufacturers of instrumentation often need to create new and more complex versions of their own formats as technology advances and as new user requirements lead to new, more sophisticated instruments.

Convert a file - in 4 steps

The file conversion is completed in 4 steps:

1.) Selecting a file to be uploaded for conversion

2.) Select 1 from 7 target file format

3.) Start the conversion

4.) download the converted file or view dsepctrum in the Spectrum tab

Each of these steps is described in more detail below.

Step 1

After selection of the appropriate input file, the name if the selected file is shown in the "File to be uploaded" box.

Cambio++ user interface, showing selected file for convertion

Step 2

In this step, the user selects the format to be converted to from the drop down menu. The file can be converted to one of the eight more general file formats. If the input file is converted to the IaeaSpe format (chosen form the drop down menu), then the graph is displayed in the Spectrum tab.

Cambio++ user interface, showing the selected conversion formats

Step 3

The selected file can now be converted to the desired format by pressing the Convert button in Step 3. The names of the uploaded and converted files are shown. If the input file is converted to the IaeaSpe format, then the spectrum is displayed in the Spectrum tab.

Cambio++ user interface, showing the results of conversion

Step 4

Finally the converted spectrum can be downloaded by pressing the Download button in Step 4. In the graphic, the download process for the Firefox browser is indicated.

Cambio++ user interface: downloading the converted file


Once the file has been translated to IaeaSpe (.spe) format, the spectrum can be viewed in the Spectrum tab as shown below. When the mouse button is placed in the graph area, a grey cross hair cursor is shown. This cursor can be used to a) examine the various peaks in the spectrum, b) to define an area to be enlarged.

Cambio++ user interface: spectrum tab

  • examine the various peaks

When the cursor is placed over a peak, the information is shown in the first grid below the graph. The information shown consists of the curve colour, graph name, peak energy, channel number and number of counts. In the second grid below the graph, one or more nuclides are shown (depending on the library selected) which have energies near to the selected energy. In the example shown, the cursor is placed at 1462 keV. The lower gird shows that K-40 has a peak near this value at 1460.83 keV.

Fine tuning to a particular peak: a) place the cross hair cursor near the peak, b) move the mouse button vertically downwards until it outside the graph area, c) use the fine tuning arrows to move the cursor in small increments. It may be more useful to zoom into a particular area before these steps are carried out.

  • define an area to be enlarged

The cross-hair cursor can also be used to enlarge a selected area in the graph. This is discussed in more detail in the following section.

Zoom: select area to enlarge

Using the cross-hair, the user can select an area of the graph to enlarge. This can be achieved by a) clicking at some point on the graph, 2) hold the mouse button depressed, 3) move the mouse button to another point thereby defing the area to be enlarged, 4) release the mouse button. The selected area will now be enlarged.

Cambio++ user interface: Zoom area selection

The enlarged selected area is shown in the image below. The original spectrum can be obtained by clicking on the zoom out button to the right of the fine tuning selecter.

Cambio++ user interface: showing the enlarged area

Spectral Data

In this tab, it can be seen that two files have been uploaded/converted. By using the radio buttons the user can examine the "original" data for each file. In the example shown the original file "Gelb_Probe_4_2. Messung_seitlich.CNF" (i.e. a cnf file) has been converted to "Gelb_Probe_4_2. Messung_seitlich.spe" (a spe file).

The first textbox show the contents of the translated file containing only the number of counts and some calibration information. The adjacent data grid shows the channel number, counts and the energy (keV). The energy has been calculated using the calibration formula from the converted file and shown below the textbox.

Cambio++ user interface: spectral data tab

Sample Spectra

Some sample spectra
  File name     Description  
  Am-241unshielded 01.Spe     Unshielded Americium 241 sample measured with a Germanium detector.  
  Ba-133unshielded01.Spe     Unshielded Barium 133 sample measured with a Germanium detector.  
  BackgroundUnshielded.Spe     Measured Background spectrum with a Germanium detector.  
  Co60NaI.n42     Cobalt 60 modeled spectrum (GSG module), measured with NaI detector and converted by Cambio.  
  Cs-137unshielded01.Spe     Unshielded Ceasium 137 sample measured with a Germanium detector.  
  Eu152_GSG_HPGE.spe     Europium 152 modeled spectrum (GSG module with a Germanium detector), converted by Cambio  
  Eu152_GSG_NaI.spe     Europium 152 modeled spectrum (GSG module) with a NaI detector, converted by Cambio  
  Pu-84%_unshielded.Spe     Unshielded 84% enriched Plutonium sample measured with a Germanium detector.  
  U-4%_ unshielded.Spe     Unshielded 4.46% enriched Uranium sample measured with a Germanium detector.  
  U-natural_unshielded.Spe     Unshielded natural Uranium sample measured with a Germanium detector.  

Popular formats

Some popular spectrum file formats
  File name     Description  
  AspectMKC-A03_SPC.spc     SPC file format...  
  BerkeleyNucleonics_SAM935_ANS.ans     ANS stands for ANSI Text file  
  FLIR_radHUNTER_Preliminary2011.n42    The purpose of the ANSI N42.42 standard is to facilitate manufacturer-independent transfer of information from radiation measurement instruments for use in Homeland Security. This standard specifies the XML data format that shall be used for both required and optional data to be made available by radiation instruments  
  IAEA_MiniMCA_SPE.spe    SPE files are ASCII text files. The file format is based on the IAEA ASCII file format

recommendation for gamma spectrometers.  

  Nucleonica_GSG.txt     text files from Nucleonica's Gamma Spectrum Generator  

Verification, Validation, and Testing

Test 1: Double Conversion

In this first test, a file named Iaea.spe containing a gamma spectrum in the IaeaSpe format was used. The main characteristics of the spectrum are:

  • Measurement time(sec): 12509 live, 12964 real
  • Channels: 0-4095
  • Maximum: about 735000 counts at channel 75 (72.73 keV)
  • Spectrum Integral: 27690825
  • Calibration: -1.927466 0.995405

Then the Iaea.spe file was converted into each of the 8 target formats (IaeaSpe, N42Xml, OrtecChn, DetectiveSpc, IdentiFinder, Gr130Dat, Gr135Dat, GadrasPcf). Note that conversion from Iaea.spe to Iaea.spe was also performed. The converted file was then downloaded, uploaded again and converted back into the orignal IaeaSpe format. The 8 resulting spectra were compared with the original Iaea.spe file.

Identical spectra after foreward/backward translation

Results (general):

  • Most of the instrument and measurement parameters were lost in the resulting IaeaSpe spectrum file through the double conversion.
  • The data (counts) were conserved unless a rebinning was necessary due to a different number of channels in the intermediary spectrum format.
  • The channel number were shifted by 1 channel from 0-4095 to 1-4096. Nevertheless the energy was conserved by a slight compensation of the energy calibration polynomial, so that finally the (energy) graph of the original and the doubly translated spectrum were almost identical. This is true for the double translation of Iaea.spe to IaeaSpe, N42Xml, OrtecChn, GadrasPcf and back to IaeaSpe, as is shown in the figure: the original and resulting curves are exactly superposed. In addition the spectrum integral from the original and the doubly translated files were equal.

Results (particular cases):

Non identical spectra after double translation

In the figure the following effects can be seen:

  • IaeaSpe (blue) to IdentiFinder (light blue): this translation needs a rebinning to 1024 channels. The energy scale is conserved but the counts are modified, resulting in a higher count than in the original.
  • IaeaSpe (blue) to DetectiveSpc (red) : this translation needs a rebinning to 8192 channels. The counts are lower than in the original but the energy scale is conserved.
  • IaeaSpe (blue) to Gr130Dat (green): the data are rebinned to 256 channels. The resulting counts are higher as in the original spectra and the energy calibration is not conserved. In addition, with counts ≥ 216 we get an owerflow.
  • IaeaSpe (blue) to Gr135Dat (brown): the data are rebinned to 1024 channels. The resulting counts are higher as in the original spectra and the energy calibration is not conserved. On overflow which occurs at 216 counts, the counts are set to the maximum value of 216-1=65535.

Test 2: Single Conversion

A set of spectra from different file formats were uploaded and converted into the IaeaSpe format and downloaded. The original spectrum was then displayed with the WinPlots tool from Advanced Measurement Technologies and compared with the graph of the translated spectrum graph shown in the Spectrum tab.


  • IaeaSpe: in this case a translation was not necessary. The spectra are visualy identical. Using the marker, the highest peak of both spectra had identical values counts as well as channel number and energy.
  • OrtecChn: the spectra were found visually identical. Moving the marker to the higest peak, an identical count value but a difference of 1 channel representing about 0.2 keV was found
  • DetectiveSpc: the spectra looked visualy identical. The maximum peak are found with the same channel number and energy with the same count.

Other formats were converted successfuly, but in absence of an external tool to display the original spectra, the converted files could not be checked.


G. P. Lasche, Cambio: A File Format Translation Application for the Emergency Nuclear Response Community

G. P. Lasche, Capabilities, Methodologies, and Use of the Cambio File-Translation Application

G. P. Lasche, N42.42: ANSI Standard for Data Format for Radiation Detectors Used for Homeland SecurityN42.42ANSI

George Lasche and Bob Huckins, An Introduction to the ANSI N42.42 Data File Format

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