5.3.6 Data Processing

Several different programs were used to gather and further process the JUSO data. This section briefly describes the software used and the data files produced. Further information may be found directly in the corresponding source files.

The data at JUSO was recorded using the TOFISS software, an integral part of the JUSO experiment. TOFISS is written in Turbo Pascal and is running on MS-DOS. During the measurement campaign several enhancements and bug fixes were implemented. This new software was named XTOFISS. The new features included a more comfortable handling for TOF measurements, an improved but backwards compatible file format, and changes to make the algorithm used to calculate the primary beam energy more stable.

A complete dataset consists of one .PRI file and several .TOF files. The .PRI file is a combined TOF spectra obtained by deflecting the primary beam into the TOF tube first with postacceleration voltage turned on and second with the voltage turned off. This spectra is used to determine the mean energy and the spectra of the primary beam. The spectra obtained by scattering the beam off the surface are stored in one or more .TOF files.

For further processing the .TOF files were converted to .energy, .atom_energy, and .ion_energy files using a program called JUSOTOF.EXE written using Borlands Delphi environment and running on Windows 95/NT. JUSOTOF.EXE does the conversion of the time of flight to the energy space for different particle mass and charge states by solving Equations 5.1 and 5.2 numerically.

The three .energy file types and the corresponding .TOF file are then combined to a more versatile, text only, and human readable data format: the .spectrum file. The conversion scripts datagen and datagenall are written in perl [30] and as shell script respectively. These scripts require a Linux/Unix environment.

Further processing is done based on the .spectrum data format. The peak fitting and detection efficiency correction routines are written in IDL [31]. Plots are generated using the IDL program jusotof and in some cases using xmgrace [32] especially for summary plots. A sample plot of the output of the jusotof IDL script is shown in Figure 5.5.

Figure 5.5: Sample output of the jusotof-IDL script. Data from scattering a 2699eV H \( ^{+}_{2}\)primary beam of a MgO surface is shown.

March 2001 - Martin Wieser, Physikalisches Institut, University of Berne, Switzerland