IMPORTANT ANNOUNCEMENTFrom 1 January, 2008, the licencing conditions of Hypermet-PC have been changed, so now it is available FREE OF CHARGE. You can download the full-featured version from this website.
The original HYPERMET code was developed in FORTRAN language by Phillips and Marlow in the early seventies, at the Naval Research Laboratory, Washington D.C. for automatic and efficient analysis of multichannel pulse-height spectra using a high-speed mainframe computer. The authors' governing principle has been to require minimal input from the user in order to save manpower and to minimise human errors.
To achieve reliable results by automatic fitting, a carefully chosen semi-empirical parameterized function was adopted to represent the detector response of Ge(Li) and HPGe detectors, including all physical and statistical effects which contribute to a real spectrum. The peak shape function of HYPERMET is the linear sum of a Gaussian and an exponentially-modified Gaussian (EMG) on the left side. On the other hand, a step function folded with the same Gaussian and a similarly folded "tail" function, resembling a sharp Compton edge, are added to the usual first or second order polynomial background function.
The fit becomes nonlinear as far as parameters of the Gaussians and exponentials are allowed to vary. Fully automatic operation means that the parameters of peaks and background are found by a nonlinear fit for each separate region in the spectrum, starting from an initial guess.
Therefore, even very complicated multiplets can be successfully and automatically resolved with minimal user interaction. Note that multiplets may have curved, stepped or backstepped background, and peaks with different FWHM. The approximate widths and energy values of two distant peaks provided by the user are the only input needed.
At the time when HYPERMET was introduced only high-speed mainframe computers could be used efficiently due to the time-consuming nonlinear fitting involved. With some modifications the program became fast enough for use on personal computers. The progress of object-oriented programming languages in the '90s has motivated the development of an interactive version with a user-friendly graphics interface. In parallel, high-quality calibration routines and other innovative features were also introduced.
Thanks to these characteristics, Hypermet-PC has gained general acceptance and is applied with success in numerous PGAA, NAA, and other gamma-spectroscopy laboratories. Its remarkable peak evaluation performance was proven in the international intercomparisons.
- Supports most common multichannel spectrum formats:
- System 100 ( *.mca files, used by CANBERRA S-100 MCAs)
- AccuSpec ( *.dat files, used by CANBERRA / NUCLEAR DATA AccuSpec MCA's)
- ORTEC ( *.chn files, used by ORTEC MCA cards)
- SAMPO-90 ( *.spe files, generated by SAMPO-90 program)
- Nucleus ( *.spm files, generated by NUCLEUS MCAs)
- Silena ( *.dat, Silena spectrum file format)
- SEIKO ( *.chn files, used by SEIKO MCAs)
- ASCII ( *.asc, plain text files used by many companies, e.g. KFKI EPCA cards etc.)
- DCHYP (*.hpc, a special format to store up to 4 spectra in a compressed form.)
- Canberra's CAM Files (*.cnf, created by the data acquisition software Genie 2000) can also be loaded after converting to S100 *.mca format. A free converter utility is offered for this purpose.
- Automatic spectrum fitting
This picture shows a successfully fit on a region of a PGAA spectrum. Please note the multiplet fit, as well as the step-shape background. The fit produced automatically without manual interaction.
- Gamma spectroscopy data for calibrations
A collection of high-quality energy and intensity data, half-lives and the respective uncertainites for many radioactive sources and (n,gamma) reactions, used for detector calibration and spectrum evaluation. One can extend the dataset by adding the certified activities of radioactive sources, to produce the absolute efficiency curve.
- Determination of absolute and relative full-energy peak efficiency
The image illustrates the efficiency curve constructed from separate measurements.They were performed using absolute intensity calibrated or non-calibrated radioactive sources, as well as using the PGAA method. The use of orthogonal polynomials ensures the numerical stability of the fits. The confidence band of the interpolation curve is also calculated.
- System nonlinearity for precise energy measurement
To determine high-precision peak positions in energy units, one has to correct for the small bias in linearity present at most spectrometry systems. This is called nonlinearity correction. This is especially important when using Efficiency and Nuclide Identification modules, because the algorithms try to locate peaks in the vicinity of their literature energy values (typically ± 0.5 keV). In practice, by using just the two-point energy calibration and neglecting nonlinearity correction, a rather large deviation in peak positions can be expected (1-3 channels), and incorrect uncertainty data will appear in the peaklist report files (in general, uncertainties will be smaller than the real values if user do not apply nonlinearity correction).
Nonlinearity correction results in significant improvement in accuracy on peak centroid determination and takes only a few minutes to create. The figure shows the automatically constructed system nonlinearity curve for a given detector system.
- FWHM (detector resolution) vs. energy curve fitting
- ADC test module
The differential nonlinearity specifies the non-uniformity of the ADC’s channel widths. For the measurement, a sliding pulser signal (e.g. BNC PB-1 Pulser with LG-1 Ramp Generator) should be connected to the ADC input. In order to reduce the statistical error, the measurement typically takes 10-24 hours to collect sufficient data (usually 100 000 counts in each channel). The differential nonlinearity - expressed in percentage - is the maximum deviation of counts in any channel compared to the average number of counts in all channels.
- Support for Dual Loss Free Counting (LFC) spectra
The Loss-Free Counting (LFC) method provides the ability of performing real-time correction of system counting losses needed e.g. when measuring short-lived radionuclides in NAA. Among the several implementations the Westphal’s Virtual Pulse Generator technique of LFC seems to be the most advanced, which proved to be accurate up to 700 kHz. Since the LFC adds n rather than one for every event that is stored, the counting statistics of the corrected spectra is non-Poisson in nature. Consequently, the use of conventional peak search routines for LFC corrected spectra would result in hundreds of false peaks. A straightforward solution, marketed by Canberra, is the Dual Spectrum LFC module which accumulates a loss-free corrected and an uncorrected spectrum simultaneously in adjacent halves of the memory. Analysis of such a tandem spectrum provides more accurate quantification of the data than analysis from a single spectrum.
- Nuclide identification for NAA and PGAA
This option is intended for qualitative and quantitative analysis of gamma-ray spectra, applicable for almost every popular measurement method (e.g. different types of neutron activation analysis, prompt gamma activation analysis, fission product monitoring, charged-particle activation, photoactivation etc.). At this stage only a simple analysis of NAA and PGAA spectra is implemented.
- Various output formats (CSV, PKL, Sampo) for further data processing
- Comma separated value file (*.csv). Convenient to load data to spreadsheet applications
- Peak list file (*.pkl). Contains peak positions, energies, intensities, all uncertainites and the chi-value
- Sampo-90 compatible output (*.ptf). This is widely used in a number of composition-calculation programs, such as KAYZERO/SOLCOI, a software package for k0-NAA.
- For technical assistance, please contact Dr. László Szentmiklósi