Software Manual Section 22

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Setup 2 for Trace Element Measurements
	Introduction Here the details of the measurements are set. This includes file names, number of cycles, sample description and the like. Between measurements, you always come back to this window to change these details for the next analysis spot.
	Status Some of the basic instrument setup data are displayed here. If anything is incorrect, click on 'Change' and make the necessary changes in the 'Init' program.
	Trace Setup 1 Display The summary of the basic settings from setup 1 are shown here. Note that these settings cannot be changed from here. For changes it is necessary to go back to setup 1.
	Data Files Up to three data files in different formats can be produced with each run. To simplify the file naming, everything starts with a 'base name'. This base name is supposed to describe the measurement in short. The base name can have spaces and funny characters which will be stripped automatically before the base name is converted into a valid file name.
	Data File Directory The directory where the data files are to be saved is shown here. To select a different directory, click anywhere on this display and make the necessary changes.
	Data File Formats and Names There are three different formats for the data files from trace measurements. At least one of these formats has to be selected at all times. File names cannot be chosen individually, but are assigned based on the 'base name' entered earlier. Finals File: This file format tries to duplicate the final files that were produced by the old HP computer. Data files in this format show only a limited amount of information about the measurement. However, it is possible to use the old UNIX-based data processing routines that were written for the old format. Files in this format have names ending with '_f.txt': Cycles File: These files are the same as the old cycles files from the HP computer. Together with the finals file they can be used for processing with the UNIX REE programs. Files in this format have names ending with '_c.txt': Verbose Format File: Data files in this format contain detailed informatin about every single step during the measurement. Basically, a data file in this format records all the steps in the format they are shown in the 'Analysis Record' window (see section 14). Data files in this format use lots of space to store and are useful mostly for debugging purposes. Verbose files have names beginning with 'vb_':
	File Names For Multiple Runs The file names generated are automatically coded for multiple runs. If a 'base name' of X and a measurement with 3 runs is chosen, the files will be names X_01f.txt, X_02f.txt and X_03f.txt. (The .txt extension is added to make life easier on PCs which have a hard time with unknown files.) If only one run is chosen, the file name does not get a numbered extension in the middle, but will simply be called X_f.txt. Note: Even when only one run is chosen initially, there will be a pre-selected file name for a second run. The reason for this -seemingly odd- feature is that it is always possible to add more runs during the execution of the measurement. In case the number of runs is changed from 1 to 3 during the first run, the data files created will have the names X_f.txt, X_02f.txt and X_03f.txt (i.e. there is no X_01f.txt in this case).
	Invalid Filenames The program checks whether the file names chosen are valid. In case a file with the given name already exists in the data directory chosen, a red 'Error' flag will show up right behind the invalid name. Modify the 'base name' to create new, unique file names. As long as at least one red 'Error' flag is shown, the 'Start Measurement' button will be dimmed out and disabled.
	Optional Settings The selections here are either for information only or are intended only for offline data processing programs (such as REE on Unix). The settings here have absolutely no effect on the actual measurement.
	Measurement Type Select here whether the current measurement is on a sample or on a standard (or neither).
	Measurement Description Add a short description of the measurement or the sample here. If this field is empty, the 'base name' will be entered automatically.
	Mineral Type Choose the mineral type of the sample. The items shown in this pull-down menu are from a setup file called Minerals.txt which can be edited to include other mineral types. This may only occasionally be necessary, since most commonly used mineral types are already included. The file 'Minerals.txt' looks like this: Do not modify the lines that start with '!' or '*' but edit/add/delete the other lines if necessary. To find out where this file is located on the harddisk, see section 50 on files and folders.
	Reference Element Choose the reference element for this measurement. The options in this pull-down menu are from the same file Minerals.txt (see above).
	Reference Concentration Enter the concentration of the reference element in the sample in weight percent here.
	Required Settings These setting have an actual effect on the measurement (as opposed to the optional settings discussed above).
	Faraday Cup Masses If nothing else is selected, the electron multiplier (EM) is used for the measurement of all masses. When the count rate of a given mass is expected to exceed 1,000,000 c/s the Faraday Cup (FC) should be used instead. As shown here, none of the masses would be measured with the FC. To make changes, click anywhere on this display. That opens this new window: The text in this window about says it all. After changing mass 27 to FC and entering the EM efficiency as 85%, the window looks like this: After all the necessary changes have been made click on 'Save & Exit' to return to the trace setup 2 window. The box 'Masses to Measure With Faraday Cup' should now reflect the changes made.
	Automatic Mass Calibration The mass calibration for the trace measurement consists of two steps: During the startup routines of the measurement, the user can manually adjust the magnetic field for one mass (the 'local calibration' mass). Later, the program automatically detemines the peak positions for all (at least three) selected 'calibration masses'. The average peak shift value is then applied to all masses to be measured. This automatic mass calibration can be done in two different ways: Once Per Run: This is the default and the only option in the old HP version of this program. Every Cycle: With this option selected, the mass calibration is done in every cycle. This makes the measurement quite a bit longer and it is not entirely clear how important this constant re-calibration is for a low mass resolution measurement.
	Counting Times In this trace program the measurement times for individual masses are automatically set. There are two options to choose from: Based on Preliminary Counts: This is the default option. The program goes through a special measurement cycle to optain preliminary count rates for all masses and the measurement times for all following analysis cycles will automatically be determined. Same as Previous Run: It is possible to use the counting times that were used in the previous measurement. This option saves time, but only makes sense when the composition of the sample in the previous measurement is very similar to the one to be analyzed now. The algorithm used for the automatic count time determination leads to the count rate - count time relationship that is shown in the graphic below. Basically, a longer measurement time is used for very low count rates up to a maximum measurement time of 20 seconds.
	Energy Offset To filter out unwanted molecular interferences, the trace element measurements are usually made at a voltage offset of 100 V from the low energy side edge of the energy distribution. Other values can be selected here. Note that there is only one step in a trace element measurement where an offset voltage other than the one chosen here is used: If during the automatic mass calibration the count rate for one of the masses drops below a certain value, the offset is reduced to 40 V for the duration of the mass peak centering routine. Immediately after the peak centering, the HV offset is returned to its original value.
	Number of Runs and Cycles Choose here how many runs and cycles you want the measurement to make. Note that there are no 'blocks' in trace element measurements (as there are in isotope measurements). One cycle represents one measurement loop through all masses and since the individual counting times can be up to 20 seconds, the total time per run can be several hours. When more than one run is selected, a new set of data files is created for each run. However, unlike in the first run, no operator interaction is required for additional runs.
	Print Options It is possible to send some of the data to the HP ThinkJet line printer. The options are: Nothing: No printout at all. Save trees. General Setup (1st Run) & Results of First Cycle: This option gives you the printout from both of the options below. General Setup (1st Run) Only: This option prints one page with general measurement setup information like date, time, user name, analytical conditions (deadtime, noise, slit settings etc.), measurement type, sample description, names of data files, number of runs, number of cycles and a complete mass list. If a measurement consists of more than one run, this general setup will only be printed during the first run (since these setup conditions do not change anyway). Results of First Cycle Only: With this option, the actual results from the first measurement cycle will be printed. The printout contains the following information: mass number, detector (EM/FC), counting time, count rate and actual counts. If a measurement consists of more than one run, the results of each run's first cycle will be printed.
	Abort Trace To exit the trace measurement setup without starting a measurement and without going back to setup 1, click here.
	Back to Trace Setup 1 This button takes you back to the window from setup 1. Note that some (not all) of the settings from this setup 2 window will get lost when you go back to setup 1 and then come back here to setup 2. Check to make sure that all options are still set right.
	Start Measurement Click here to begin the measurement. This button may be disabled when invalid options are selected in this setup 2 window (e.g. incorrect data file names).

FJ Stadermann	Back to Top	Next Section