HAL Id: jpa-00223962
https://hal.archives-ouvertes.fr/jpa-00223962
Submitted on 1 Jan 1984
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICROPROBES - BASIC PREMISES
AND THE CONTROL PROGRAM+
W. Chambers, J. Doyle
To cite this version:
W. Chambers, J. Doyle. A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICRO-
PROBES - BASIC PREMISES AND THE CONTROL PROGRAM+. Journal de Physique Colloques,
1984, 45 (C2), pp.C2-223-C2-226. �10.1051/jphyscol:1984249�. �jpa-00223962�
JOURNAL DE PHYSIQUE
Colloque C2, supplément au n°2, Tome 45, février 1984 page C2-223
A USER DESIGNED SOFTWARE SYSTEM FOR ELECTRON MICROPROBES - BASIC PREMISES AND THE CONTROL PROGRAM*
W.F. Chambers and J.H. Doyle*
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.
*Rookwell International, P.O. Box 464, Golden, CO 80402, U.S.A.
Résumé - Cette étude présente une méthode globale d'automatisation de micro- sondes électroniques. L'intégration des appels de routine en tant que com- mandes système a favorisé l'emploi de routines généralisées d'acquisition et d'analyse de données. Le logiciel, conçu autour des microsondes Cameca et JEOL les plus automatisées actuellement disponibles, permet une commande complète du spectromètre, de la platine et du faisceau.
Abstract - A systems approach to the automation of electron microprobes is presented. The use of generalized data collection and analysis routines has been encouraged by integrating their calls as system commands. The software has been designed around the most fully automated Cameca and JEOL micropro- bes now available and includes full spectrometer, stage, and beam control.
Although automated microprobe analysis "systems" have been available for several years, their software usually consists of a group of many unrelated programs which must be individually executed in order to perform qualitative and/or quantitative analyses. These approaches have resulted in systems which are either of limited utility or are very complex to use. A true systems approach has been achieved with the current set of programs. All of these programs are called by and run inside the control program, Sandia-TASK /1,2/. They have been written by and for microprobe operators in the FLEXTRAN /3/ language developed by Tracor Northern and will control any Cameca or JEOL microprobe that has been automated with Tracor elec- tronics. Extensive effort has been expended to assure that they are user friendly.
I - BASIC PREMISES.
The most basic premise has been that the software should be designed to be used by an intelligent operator who is not necessarily interested in learning "computereze."
Since the basic monitor and editing functions have been integrated in FLEXTRAN, it was possible to develop a software system that incorporates a large number of programs which are called by the user in a transparent manner. Once the computer system has been activated, all of the operating system's capabilities are made available by executing a single program, START. START prepares the system so that it will operate in the most efficient manner and then activates the main con- trol program, Sandid-TASK. TASK in turn reads a file that describes the particular instrument that it is being used with, verifies that the clock is set, prints a sum- mary of the current status of the machine, and enters its command mode.
The command structure of Sandia-TASK utilizes the "verb-noun" sequence used earlier by Tracor in their TASK III / 4 / . A menu-driven system has intentionally been avoided because it is less efficient for the experienced user. Instead, detailed documentation has been provided HI and a HELP command included. If HELP is typed, a list of the available commands will be displayed on the screen along with in- structions on obtaining help for any specific command (including HELP itself).
While in HELP mode, one can easily obtain help for any combination of commands or return to command mode.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984249
JOURNAL DE PHYSIQUE
The second premise is that the system should be capable of simultaneous data ac- quisition and reduction--it should be capable of multi-tasking operation. Although Tracor provided a system that would operate the spectrometers asynchronously, the concept was not continued to include simultaneous data collection and reduction.
The techniques used to obtain this important premise are described elsewhere in this volume /5/.
The third premise is that data should be treated on a statistical basis. This is done in essentially every aspect of the program. All X-ray intensity measurements have associated with them a minimum counting time, a maximum counting time, and a desired counting statistic. After the minimum counting time, a peak to background ratio is calculated, the required counting time to obtain the desired counting statistic is predicted, and a counting time decision is made. The system utilizes one set of counting statistic data for unknowns and a second set for standards.
Even the peaking routines are statistically based, adjusting the spectrometer rates according to the expected intensity from the standard.
The fourth premise is that the software should be designed around the most fully automated instruments available and, if necessary, have portions bypassed rather than having additional features patched to the system. Accordingly, the control system is capable of full spectrometer, stage, and beam control. Up to seven four- crystal spectrometers with their associated electronics (detector bias or pulse height analyzer (PHA) baseline, PHA window, timer, counter) can be controlled asynchronously. Spectrometer temperature can be monitored and peak position auto- matically compensated for thermal drift. By controlling the detector bias voltage rather than the analyzer baseline, it is possible to provide computer control over the full range of a four-crystal spectrometer without operator intervention. If bias control is not available, the system monitors the amplifier settings required for each crystal/detector combination and notifies the operator whenever an amp- lifier adjustment is required. Provisions have been made for beam current mon- itoring and for digitally controlling beam diameter, static position, scanning, and current. Stage control includes X, Y, Z, and rotation. X, Y and Z backlash corrections are made synchronously in order to maximize precision. Dangerous motion combinations are stored and are automatically avoided. As an extra pre- caution, both proximity and limit switches are recognized for all mechanical motion.
I1
-
SPECIAL CONSIDERATIONSBy designing the control system about fully automated instruments, it has been pos- sible to relatively easily accomodate both Cameca and JEOL. Two techniques have been used to maximize transportability. First, a patch program is maintained that contains the code that is necessarily different for the different manufacturers.
Second, a configuration file is created that describes an individual instrument.
This file contains such thfngs as flags that describe which crystals and detectors are associated with each spectrometer, mechanical limits, deadtimes, initial de- fault values for the control program, and information about optional items such as plotters. Values in the configuation file can be modified by using the CONFIG program. CONFIG has been written in a manner that permits it to be executed by itself or from inside TASK as one of the control program commands. This eases user modification of the software system to accommodate an expanded instrument.
Both energy dispersive (EDS) and wavelength dispersive (WDS) data collection modes are controlled from the single operating system in Sandia-TASK. The basic EDS capabilities of the equipment manufacturer have been retained but have been made more easily callable. Since several of these functions operate on the spectral data area of the multi-channel analyzer, it has been possible to utilize this group for WDS data manipulation by collecting the WDS data in the spectral area.
In order to retain a highly versatile system without demanding redundant input, the system utilizes a number of stored tables and files. Data describing up to 35 WDS
reference data sets can be stored in an element table (FIG. 1). Each reference data set includes a spectrometer/crystal assignment, X-ray position and intensity information, background and counting statistic information, a data collection pro- irity, and descriptors of the associated physical standard. Unlike many systems, the tables are designed so that they can be utilized for many different analyses.
Each quantitative program, for example, sets its own pointers to references in an element table.
7/20/83 3:05 PM
EL SP XTAL PRI POS BKG OFFSETS STD INT LAST BKG INT CF STD SI1 1 TAP 0 0.27777 0.017 0.017 3563.59 t 0.2% 1.49 1.000 SI S2 2 PET 0 0.61428 0.007 0.007 283.18t 0.5% 0.57 0.439 PYR FE3 3 LIF 0 0.48113 0.012 0.012 876.91 t 0.5% 1.81 1.000 FE N13 3 LIF 0 0.41196 0.006 0.006 908.12 t 0.4% 2.17 1.000 NI
Fig. 1
-
A portion of an ELEMENT tableThe locations of 25 sample points (including rotation if applicable) can be stored in a points table. Since the system permits storage of up to 200 files or tables of each type, it is possible to have 5000 predefined sample points. EDS reference spectra are stored as individual files which can be called into a refer- ence table as needed. Whenever a quantitative analysis is performed, the reduced data are automatically stored as files as are the instrument operating paramaters and full descriptors of the analysis being performed. The use of generalized data collection and analysis routines has been encouraged by integrating their calls as system commands 121. The writing of specialized routines is, however, not precluded.
I11
-
THE CALIBRATE COMMANDConsider the CALIBRATE command as an illustration of the system operation. CAL FE3 S2 N13 SI1 might be used to calibrate Fe on spectrometer 3 and S on spectrometer 2 with a FeS2 standard, Ni on spectrometer 3 with a Ni standard, and Si on spectr- ometer 1 with a Si standard. The calibration will be performed on a spectrometer driven priority basis, automatically associating the proper standard with each ele- ment in the list. After getting the, first standard, the machine will pause to permit the operator to verify its focus. Beam current and spectrometer temperature are measured, the proper crystal inserted, the PHA window and detector bias voltage or PHA baseline calculated and set, and a peak search performed. The spectrometer speed during the peak search is adjusted according to the expected standard in- tensity in order to optimize the centroid determination. As the peak search is performed, the peak shape is tested and displayed on the video screen. If the tests show that the centroid lies outside the initial range, the range is adjusted and more data are collected. Once the centroid has been found, its position is su- perimposed on the video display of the peak. Both peak and background data are then collected for a minimum time and the counting time required to obtain the de- sired standard deviation is calculated. Data collection proceeds for this time or for the maximum time allowed, whichever is smaller. Backgrounds are normally col- lected on both sides of the peak; however, they need not have similar offsets and either or both can pe suppressed if necessary. All data are corrected for deadtime and peak data are corrected for background, converted into counts per nanoampere per second, and stored along with the counting statistics, the background counts, and the centroid of the peak normalized to 25OC. All incoming data are displayed to assure the operator that the system is functioning properly. As the calibration of each reference is completed, a message of the following form is printed:
TEMP 26.1C
SI1 SPEC1 TAP PK POS= 0.27775 5 SEC, K=.9993t.0028 0.2% STD DEV. 191714 PK CNTS 159 BKG CNTS OLD STD= 4232.12 PK POS= 0.27768
NEW STD= 4229.15 PK POS= 0.27771 BKG INT= 3.17 PK BKG= 1334 .ll
C2-226 JOURNAL DE PHYSIQUE
Note that the current peak position (.27775) is not the stored position (.27771) since the spectrometer temperature was not 25OC. If the system finds that the new and old standards vary by more than a preset amount (usually 2%) the message: ATTN:
ACC ERROR! is printed. Upon completion of all of the calibrations in the command list, the system returns to command mode and is ready for additional input.
IV - X-RAY MAPPING
As a final indication of the control capabilities of the system, consider the low magnification digital collection of X-ray maps. Combining element table data with digital control of the spectrometers, the beam current, and the beam scanning system makes possible the digital collection of low magnification X-ray maps in a manner that will cause given concentrations of the elements of interest to attain a reference brightness on the maps /6,7/. This is done by knowing the pixel density that will result in the refer-
ence intensity and calculating a combination of scanning rate and beam current that will cause the given concentration to produce such a pixel density. The magnification of a map is used to dynam- ically calculate the amount that the beam is offset from the true focal point of the X-ray optics and to correspondingly calculate and initiate any required spec- trometer offsets. The system command that results in such a map is PHOTO ELEMENT MAGhI- FICATION CONCENTRATION. As well as performing the mapping
function, the computer fully labels each map as shown (Fig. 2). By using either a 35mm or 70mm camera, it is possible to take an unattended
sequence of X-ray maps at one Fig. 2
-
lOOX map of Ag in an experimental solder.or many points. The map was initiated with the command PHOTO AG 100 10. Note the reference intensity for 10 wt % Ag.
References :
[I] CHAMBERS (W. F.) and DOYLE (3. H.), Proc. 14th MAS Conf., 1979, 279.
[2] CHAMBERS (W. F.), Sandia National Laboratories report SAND82-1081, 1983.
[3] SCHAMBER (F. H.), FLEXTRAN Programming Instruction and Reference Manual, Tracor Northern, 1981.
[4] McCARTHY (J. J.) and WODKE (N. F.), TASK: Wave Dispersive Spectrometer and Stage Automation Program, Version 3, Tracor Northern, 1977.
[5] DOYLE (J. H.) and CHAMBERS (W. F.), ICXOM 10, 1983.
[6] CHAMBERS (W. F.), Proc. 13th MAS Conf., 1978, 84.
[7] CHAMBERS (W. F.), Proc. 16th MAS Conf., 1981, 43.
+ This work was supported by the U. S. Departmentof Energy under Contract Number AC04-76DP03533 and DE-AC04-76DP00789.
