Account for Dead Time

Use RPS > Account for Dead Time (geogxnet.dll(Geosoft.GX.Radiometrics.AccountForDeadTime;Run)*) to apply instrument live time or dead time corrections to airborne radiometric data (potassium (K), uranium (U), thorium (Th), total count (TC), upward uranium (UpU), and cosmic channels). For more details, see the Application Notes below.

To rerun the process with previous settings, select the header cell of any channel generated by this operation, then right-click to open the context menu. The last item in the menu is the most recently executed process (GX). Select it to reopen the associated dialog. From there, you can rerun the process using the existing settings, adjust parameters before execution, or simply close the dialog. Learn more about Dynamic Process Links (Makers).

Account for Dead Time dialog options

Use this dialog to choose the correction method and configure the relevant parameters.

Input channel suffix	If Generate Radioelement Counts has been applied to the current database, the suffix used for its generated channels (K, U, Th, TC, UpU, cosmic) is automatically detected and preselected. If multiple generated channel sets exist, all detected suffixes are listed, with the most recent one selected by default. After you select a suffix, the associated channels are listed below the field. Script Parameter: SPECTRO.ACCOUNT_FOR_DEAD_TIME_INPUT_SUFFIX
Correction method	Choose how the correction will be applied: Live time: Select this option when a live time channel is available. Dead time: Select this option when a dead time channel is available. Script Parameter: SPECTRO.LTMETHOD [0 - live time; 1 - dead time]
If an upward‑looking detector is available, you may optionally specify a separate live time or dead time channel and an acquisition time input (either a channel or a constant) for the upward‑looking data. If no upward‑looking channels are defined, the live time/dead time settings for the downward‑looking spectra are also applied to the upward‑looking data.
Live Time Method Parameters
Live time channel	Enabled when Live time is selected. Choose the instrument's live time channel. Script Parameter: SPECTRO.LIVETIME
Upward live time channel	Select the live time channel for the upward‑looking detector. Script Parameter: SPECTRO.UPWARD_LIVETIME_CHANNEL
Dead Time Method Parameters
Dead time channel	Enabled when Dead time is selected. Choose the instrument's dead time channel. Script Parameter: SPECTRO.LIVETIME
Upward dead time channel	Select the dead time channel for the upward‑looking detector. Script Parameter: SPECTRO.UPWARD_LIVETIME_CHANNEL
Acquisition Time Options
Acquisition time values (channels or constants) must use the same units as the live time or dead time channels (typically seconds).
Acquisition time input	Choose how acquisition time is provided: Channel Constant Script Parameter: SPECTRO.ACQUISITION_TIME_METHOD [0 - channel; 1 - constant]
Channel Option Select the relevant acquisition time channels.
Acquisition time channel	Select the channel representing acquisition time for the primary detector. Script Parameter: SPECTRO.ACQUISITION_TIME_CHANNEL
Upward acquisition time channel	Select the channel representing acquisition time for the upward‑looking detector. Script Parameter: SPECTRO.UPWARD_ACQUISITION_TIME_CHANNEL
Constant Option Specify acquisition time constants appropriate to the instrument configuration or survey design.
Acquisition time constant	Enter the acquisition time. Script Parameter: SPECTRO.ACQUISITION_TIME_VALUE
Upward acquisition time constant	Enter the acquisition time for the upward‑looking detector. Script Parameter: SPECTRO.UPWARD_ACQUISITION_TIME_VALUE
Output Channel
Output channel suffix	Enter a suffix to append to the corrected channel names. Default: `live` As you type, the information string below the field updates to show the resulting channel names. Each name is formed by combining the radiometric element name with the suffix (letters and numbers only). Output channels follow the pattern element_suffix. Script Parameter: SPECTRO.ACCOUNT_FOR_DEAD_TIME_OUTPUT_SUFFIX

Application Notes

This tool operates on pre-processed channels generated by Generate Radioelement Counts, which are labeled *_raw when the default suffix is retained. Based on the selected correction method, the tool applies a time correction and generates new output channels, labeled *_live by default.

Dead Time and Live Time Corrections

Spectrometer data are typically recorded in counts per second. However, instruments may briefly pause to process incoming signals—this pause is referred to as dead time, during which no counts are registered. In contrast, live time represents the period during which the detector is actively recording pulses; it is equal to the total acquisition time minus the dead time.

Sampling time must balance measurement precision with field efficiency. For example, when using a 350 cm³ NaI(Tl) detector, a sampling time of approximately 2 seconds is suitable for highly radioactive environments, whereas longer sampling intervals—typically around 6 seconds—are used in low‑radioactivity environments.

This tool provides corrections for both dead time and live time effects.

Live Time Correction

When live time is recorded (that is, when a live time channel is available), the live time corrected output channel is calculated using the following formula:

where:

live_time_corrected — Live time corrected output channel
acq_time — Acquisition time, provided either as a constant or as a channel (must be in the same units as live_time)
raw_count — Input raw count channel value
live_time — Live time channel

The same correction is applied to upward‑looking channels using the corresponding upward‑looking inputs.

Dead Time Correction

Dead time corrections are applied to each spectral window using the following expression:

where:

dead_time_corrected — Dead time corrected output channel
acq_time — Acquisition time, provided either as a constant or as a channel (must be in the same units as dead_time)
raw_count — Input raw count channel value
dead_time — Dead time channel

The same correction is applied to upward‑looking channels using the corresponding upward‑looking inputs.

*GX.NET tools are embedded in the geogxnet.dll file located in the \Geosoft\Desktop Applications\bin folder. To run this GX interactively (outside the menu), navigate to the bin directory and specify the GX.NET tool in the required format. See the Run GX topic for more guidance.