5.3.3.9. Automatic Efficiency Calibration. ORTEC A66-BW GammaVision

783620H / 1013 5. MENU COMMANDS

5.3.3.9. Automatic Efficiency Calibration

GammaVision lets you automatically perform the efficiency calibration by using the table in an existing

.EFT

file.

Click the calibration sidebar’s Merge... button. This will open a standard filerecall dialog (Fig. 110). Select the

.EFT

file to be used and click Open. Gamma-

Vision will recall the table of entries and perform a calibration based on the data in the table. When the procedure is complete, the graph and table will be displayed.

Fig. 110. Recall Efficiency Table.

5.3.3.10. Manual Calibration

To perform a completely manual calibration, enter the efficiency and energy in the upper section of the Efficiency Calibration Sidebar, then click Enter. The fit, graphs, and table will update after each point is entered.

If the table of values for a manually entered calibration is saved, the only values it will contain are the energy and the efficiency. Doing an automatic recalibration with this table will restore the manual calibration. If the calibration is a mixture of worksheet values and manual entries, the automatic recalibration will use recalculated values for the worksheet entries, and the manual entries will be used as entered.

5.3.3.11. Other Efficiency Sidebar Control Commands

In addition to Edit File..., the Efficiency Calibration Sidebar’s control menu (Fig. 108) contains the Move, Close, Graph, Table, Restore, and Destroy functions. Close saves the efficiency and exits the efficiency calibration function. Graph and Table are display/hide toggles. Use Restore to ignore all calibration inputs made during this calibration session, and Destroy to clear the current working calibration and table of values.

5.3.3.12. Editing the Standard (.EFT) Table File

An efficiency standard table file contains all the data input needed to perform a calibration using the standard. This file can be created from the Efficiency Calibration Sidebar by clicking on the

Save button and assigning a filename, or with an ASCII text editor. The file can be modified with the Edit File... function on the sidebar’s control menu. Click File Edit... to open a standard file-recall dialog. Select the

.EFT

file to be edited; it will be displayed as shown in Fig. 111.

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GammaVision

®

v7 (A66-BW) 783620H / 1013

The table contains the following information (by columns):

! Isotope name (same as library).

! Gamma-ray energy (keV).

! Efficiency (used for manual efficiency inputs, ignored if remainder of line is valid).

! Activity in Bq or μCi at the date and time specified in column 7.

! Gammas/sec for this energy, at the specified date and time.

! Uncertainty for this nuclide.

! Calibration date and time for the gammas/sec calibration. The gammas/sec are automatically decay corrected from the date/time in column 5 to the date/time of the spectrum acquisition.

! Half-life of this nuclide in days.

! Branching ratio as gammas/100 disintegrations.

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Fig. 111. Edit Efficiency Table.

783620H / 1013 5. MENU COMMANDS

The Gammas per second and activity fields are shown based on the activity units as described below:

! If the units are GPS, then the Activity in the table is displayed as: Activity in edit control divided by (Gammas per 100d divided by 100) and GPS is displayed as the Activity in the edit control.

! If the units are Bq, then the Activity in the table is displayed as the activity in the edit control and the GPS in the table is calculated as the Activity in the edit control multiplied by (Gammas per 100d divided by 100).

! If the units are μCi, then the Activity in the table is displayed as the Activity in the edit control and the GPS in the table is calculated as the Activity in the edit control mulitplied by (Gammas per 100d divided by 100) multiplied by 37000.0.

The fields to validate are the Activity and GPS fields in the table. They are calculated from the

(1) Activity edit control, (2) Activity unit’s combo box, and (3) Gammas/100d field in the library group. Based on units:

! Activity Units set to GPS:

Activity in table = Activity in edit control / (Gammas/100d * 0.01)

GPS in table = Activity in edit control

! Activity Units set to Bq:

Activity in table = Activity in edit control

GPS in table = Activity in edit control * (Gammas/100d * 0.01)

! Activity Units set to μCi:

Activity in table = Activity in edit control

GPS in table = Activity in edit control * (Gammas/100d * 0.01) * 37000.0

After the energy list in the

.EFT

files is the following line:

FitType = <iAbove> <iBelow> <Knee> where:

<iAbove>

<iBelow>

<Knee>

= The fit type above the knee (0–3 or 6).

= The fit type below the knee (0–3).

= Knee energy for fit types 1–3.

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