Software Manual Section 04

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Main
	Introduction This is the "Main" routine that is modelled after the HP's MAIN program. It is the window that will most likely be open during the tune-up of the instrument. It displays basic operating conditions and detector signals and lets you change several parameters. All displays are updated once every second.
	Beam Off/On Clicking this button will turn the beam on or off. Of course, you could also use the "real button" on the 3f control panel, in which case this "software button" will get updated automatically. This is also true for all the other controls in this window. Try it.
	Display of Detector Readings This part of the window has three different states, which are discussed individually below:
Beam Off (i.e. Primary FC Engaged) In this situation, the "Primary Current" reading is highlighted with a red background. The current is shown in exponential notation on top and in more readable units below. The secondary count rate shown on the right are the last reading when the beam was on and is for reference only.   Beam On (and EM or Secondary FC Engaged) Now the "Count Rate" is highlighted with a red background and the count rate in counts/second is displayed. The value on top represents the last reading which is updated every second. The number below is the average of the last 10 readings, which can be helpful at highly variable low count rates. If there is no display at the bottom, the beam has not yet been on for at least 10 seconds. The primary current displayed on the left represents the reading when the beam was last measured with the primary FC. Beam on (and Channel Plate Engaged) In this case, there is neither a primary current nor a secondary count rate to report. Either the image or the cross-over is displayed on the channel plate. Both numbers show here are only the last values measured. To indicate that the beam is actually on, the "Count Rate" side gets a thin red frame this time.
	Sample Offset Voltage
This is where the sample offset voltage can be set and displayed. The possible range of offset voltages is from -125 to +125 V, which corresponds to sample voltages between 4375 and 4625 V. To set the offset voltage enter a value at the digital control or move the red slider to the desired position. To quickly go to zero offset, click on the >>0<< button.
	Mass Display Displays the current mass and the corresponding B-field value. Actually, only the B-field value has a real, physical meaning. The mass value displayed is only as good as your mass calibration. You can increase and decrease the mass in steps of 1 amu by clicking on the black triangles. Of course, a mass value can also be entered directly. The B-field value cannot be set directly. (Some people prefer "Dalton" as the mass unit, but it always makes me think of the Dalton brothers from the Lucky Luke comics, so I find it less distracting to use "amu", atomic mass units.)
	Periodic Table Instead of manually entering a mass number, you can also simply pick an element from a periodic table. This button will take you there. The details of this function are discussed in Section 5 of this manual.
	Mass Calibration If something is wrong with the mass calibration, this button should directly take you there to fix what needs to be fixed. Details in Section 6 of this manual.
	Fast Access Several often-used masses are available as buttons for fast access. Just clicking on any of these buttons changes the magnetic field accordingly. The labels refer to the dominant isotope, i.e. clicking on 'Mg' goes to 24Mg. Note: Alternatively it is possible to use the first function keys on the keyboard for this fast access. The keyboard is labeled with the same element names and pressing one of the function keys is equivalent to pressing these virtual buttons with the mouse. However, the keyboard equivalents only work as long as the Main window is active and in the foreground.
	Integer vs. Exact Mass For all isotopes -with the exception of 12C- the exact mass is not the same as their integer mass. The problem is that the mass calibration (Section 6) is customarily done in such a way that e.g. 1.000 corresponds to hydrogen and 27.000 corresponds to aluminum. Although this is not technically exact, it is convenient and does not have any adverse side effects. If the mass calibration is done in such a way that all isotopes have integer masses, this should be selected here. This way the 'Fast Access' buttons set the magnetic field to integer values and not to the exact masses.
	Detection Mode This array of button does the same as the corresponding buttons on the 3f control panel. Pressing/clicking buttons on either end will change the detection mode.
	Raster Size This box displays the current raster size of the primary beam. I have noted that sometimes none of the raster size buttons on the 3f control panel is lit when at the same time this computer raster size display says "500 micron". That should scare you! It means that the raster could on without you knowing it. As far as I can tell there seems to be no way to set the raster size with the computer, we can only display the value chosen on the hardware panel.
	Manual Magnet Control This allows you to disable the magnet control dial on the 3f control panel. It doesn't always seen to work and I am not quite sure why.
	Analysis Status This display changes to "Analysis Running" when you have started a measurement. During a measurement all the values displayed in this "Main" window are passive (but not necessarily static). The way this hierarchy works is detailed in Section 2 of this manual.
	Exit Makes this window go away.

FJ Stadermann	Back to Top	Next Section