Software Manual Section 25

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Manual Energy Edge Determination
	Introduction This is the same routine that is called by the analysis programs Iso and Trace, with the only difference that here it is being started manually. It finds the center of the secondary ion energy distribution and the 'energy edge'. It can be used to set the extraction voltage to a predetermined offset value.
	Manual vs. Automated Mode When this program is called up manually from the Menu window, it looks the way it is shown above. All of the buttons and numeric entry field are available in this mode. However, when this program is called as a subroutine from one of the analysis programs, only the bottom two panes (graph and curve statistics) are visible as shown here on the left. In this automatic mode a direct user interaction is not necessary/possible. In the individual description below all items that refer to the bottom two panes are valid for both modes.
	Measurement Conditions: Mass The current mass value is shown here. This display is both active input and output: It is possible to change the mass both here and with the B-field knob on the ims3f. The accuracy of the mass value calculation depends on the current mass calibration.
	Measurement Conditions: Energy Window The size of the energy window (in Volts) is displayed here. The value is taken from the Initialize routine (section 3). If you try to change the value here you are friendly reminded that these kinds of basic settings need to be changed from Initialize.
	Measurement Conditions: Mode When I wrote this program I thought it might be useful to have the choice between different routines to find the peak maximum and the edge. After much testing the current method proved so reliable that an alternative way was not really necessary. Thus, this button is here only for historical reasons.
	Measurement Conditions: Offset From Edge Enter here the desired offset value (in Volts from the edge of the peak). The sign (+ or -) of the value is irrelevant of the secondary beam current, the offset is always set in the direction of the high energy side.
	Measurement Conditions: Start Offset Enter the starting value (in Volts) for the HV offset here. This is where the program starts the search for the maximum. In practice, the start offset does not matter much and can always safely set to zero.
	Measurement Conditions: Detector Choose the detector that should be used for the energy edge determination (EM or FC).
	Measurement Conditions: Time/Step This is the counting time for each measurement step in seconds.
	Measurement Conditions: Step Size Enter the desired value for the initial step size (in Volts) here. In practice, just about any value here works because the program reduces the step width automatically once the position of peak and maximum has been narrowed down. Note that this whole energy edge routine does not support steps smaller than 1 V.
	Curve Statistics: Position of Current Offset The current offset at all times during the routine will be displayed as a vertical line in the graph and its value (in Volts) will be shown here.
	Curve Statistics: Maximum Count Rate The count rate at the maximum of the energy distribution peak will be shown here.
	Curve Statistics: Position of Maximum The position (in Volts) of the maximum of the energy distribution is shown here. If this value is very different from zero the sample might be charging.
	Curve Statistics: 10% Count Rate The 'energy edge' is the point on the low energy side where the outline of the peak intersects the this horizontal blue line which is at 10% of the maximum count rate.
	Curve Statistics: Position of Edge The position (in Volts) of the 10% edge of the energy distribution is shown here.
	Curve Statistics: Position of New Offset The new offset position at the desired distance from the edge is displayed with a vertical green line in the graph and its value (in Volts) is shown here.
	Curve Statistics: 50% Peak Width The width of the energy peak in Volts is automatically calculated and displayed here. This value should be very similar to the size of the energy window or something is wrong. Only for very small window sizes there can be a significant difference between these two values.
	Graph: Vertical Axis Scaling Choose between a logarithmic and a linear scale for the (vertical) count rate display in the graph. The minimum and maximum values of the axis are scaled automatically.
	Graph: Horizontal Axis There are three different item shown on the horizontal (energy offset) axis: Voltage Offset: This value ranges from 127 V to -127 V, which is the maximum range the ims3f can accomodate. Absolute Voltage: This is the actual voltage for the secondary ion extraction. Low vs. High Energy Side: Shows on which side the high energy secondary ions are.
	Start Click here to start the automatic energy edge determination routine. During the routine it is possible to stop the measurement by clicking on the 'Abort' button that shows up after clicking on Start.
	Number of Steps This is here for historical reasons and has no actual function
	Total Number of Steps This is where the number of steps gets really displayed. It is for reference only.
	Exit To exit this energy edge determination program, click here. The 'New Offset' will be retained as current offset value.

FJ Stadermann	Back to Top	Next Section