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AN X-RAY CRYSTAL SPECTROMETER FOR ION-INDUCED MULTIPLE IONIZATION STUDIES, PARTICULARLY FOR M SATELLITE STRUCTURE
I. Török, B. Tóth
To cite this version:
I. Török, B. Tóth. AN X-RAY CRYSTAL SPECTROMETER FOR ION-INDUCED MULTI-
PLE IONIZATION STUDIES, PARTICULARLY FOR M SATELLITE STRUCTURE. Journal de
Physique Colloques, 1987, 48 (C9), pp.C9-79-C9-82. �10.1051/jphyscol:1987910�. �jpa-00227205�
AN X-RAY CRYSTAL .SPECTROMETER FOR ION-INDUCED MULTIPLE IONIZATION STUDIES, PARTICULARLY FOR M SATELLITE STRUCTURE
I. TOROK and B. T ~ T H
ATOMKI,
Institute of Nuclear Research of the Hungarian Academy of Sciences, Pf.
51, H-4001Debrecen, Hungary
Abstract: A f t e r the s h o r t description o f an X-ray c r y s t a l spectrometer three measurements are mentioned as examples o f i t s performance:
a, relative intensities o f A1 K alpha and b e t a satellites;
b, Mg content determination in the presence o f much Ca;
c, satellite s t r u c t u r e o f Ta M alpha and b e t a lines.
A simple Soller-type f l a t crystal X-ray spectrometer has been developed t o measure t h e satellite s t r u c t u r e o f characteristic X- radiation arising f r o m multiply ionized atoms created in energetic ion- atom collisions. The spectrometer is based on a rhombic goniometer mechanism. The home-built Soller s l i t s provide 0.3 degree angular divergence, The detection o f the X-rays reflected from the analyzer c r y s t a l is performed by a flow proportional counter.
An MCA based on a single card microcomputer controls the angular movements through a step-motor and analyses the signals f r o m the proportional counter, either in pulse height analysis o r in multiscaler mode, and a simple evaluation o f t h e obtained data is also Provided. The f i r s t t e s t s o f the system were performed by X-ray excitation o f thick targets.
Later the spectrometer has been installed on the beam line o f the 5 MV Van de Graaff generator o f t h e ATOMKI. Test spectra were taKen bombarding d i f f e r e n t elements by H+ and He+ ions. Thick t a r g e t s o f aluminium, silicon, q u a r t z glass, n a t u r a l chalk, titanium, stainless steel, copper and tantalum were used. Some o f the preliminary results a r e presented in the followings.
a,The aluminium K alpha satellite s t r u c t u r e has been studied already in details, e. g. Richards [I] measured it in the energy range o f 0.1- 3.0MeV ~ e + ion bombarding, Sonobe [2] in the 5.42-40.6 MeV range. We measured i t a t the 3.2 MeV He+ ion energy. One o f our A l K X-ray spectra is seen on Fig. 1. Fig.
2a. shows t h e relative intensities o f t h e diagram and t h e KL' satellite peaks as a function o f the bombarding ion energy (where the superscript i is the number o f L vacancies). Our measurements fit well between the data of the mentioned authors, proving t h a t our instrument can be used effectively in such measurements. This kind o f representation o f data reveals t h a t the highest vacancy numbers are the most sharply sensitive on the energy change o f the bombarding particle. Fig. 2b. gives t h e BEA calculations o f t h e K-shell and L- subshell ionization c r o s s sections, qualitatively explaining the shapes O f the curves in Fig. 2a.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987910
C9-80 JOURNAL
DE
PHYSIQUEFig. 1.--The K X-ray spectrum o f alu- minium, obtained by 3.2 MeV He+ ion bombardment, taken with an ADP ana- l y z e r c r y s t a l .
F /
BEA calculations3
Fig. 2arThe intensity distribution Fig. 2b.--Cross sections f o r K- o f KL1 X-ray lines o f aluminium as a and L-subshell ionization o f alumi- function o f bombarding He+ ion energy nium bombarded by He+ ions, calcula- (*
-
Ka Li; x-
Kg Li) t e d by a BEA code.b,A byproduct o f t h e Ca K, LI satellite intensity investigation has a possible practical interest. Fig. 3. gives a P a r t o f t h e X-ray spectrum obtained f r o m a natural chalk sample.ln natural chalks t h e r e is always present a certain amount o f magnesium. This spectrum taken a t 2 MeV proton bombardment and using an ADP analyzer crystal o f f e r s the possibility t o p e r f o r m PlXE measurements o f the relative Ca/Mg content when Mg is in a very l i t t l e amount relative t o Ca, since the Ca Ka is measured in a weak t h i r d o r d e r reflection, while the Mg line in a strong f i r s t order one. Probably one-two order o f magnitude enhancement can be obtained f o r the Mg Ka using thls method. This can be used e. g. t o measure t h e dolomitization grade o f chalks, o r the Ca/Mg ratio in concretes, what is important in their corrosion resistance.
c, A f u r t h e r investigation was t o measure M alpha and beta X-ray satellite structure. We used a thick tantalum metall target. Fig. 4.
gives the shape o f spectra obtained a t 2 MeV proton, 3.2 MeV He+ and 1.6 MeV ~ e + bombardment. The known satellite energies [3,4] are also shown.
The resolution o f the instrument is demonstrated by the Si K, spectrum measured under the same condition6 as the M spectra. The Si
, K
energy is j u s t between the, energies o f Ta Mu and Mp X-ray lines. Anyhow, it is interesting t o compare the structure a t the K and M shell a t about the same binding energy. It is seen t h a t the M satellite lines could n o t have been resolved, but f r o m the shape o f the lines it is obvious that the yields o f the d i f f e r e n t satellites a r e changing with the bombarding particle and-
in a less extent-
with the bombarding energy. Much resolution enhancement would not has been expected using 2nd order reflections, because o f the natural width o f the M lines.Our spectra show that probably other satellite lines than the known ones are exited mainly f o r the He-ion bombardment. Many o f the former authors investigating M X-rays assumed t h a t the multiple ionization i s not significant in the MeV bombarding energy range. Our observations do not support the above assumption. We found that in the case o f the 2 MeV proton bombardment the contribution o f the satellite lines t o the M intensity is about 50 per cent o f t h e intensity o f the diagram line, and f o r the He+-ion bombardment this contribution is already approximately 100 per cent in accordance with the predictions o f the so called
geometrical model o f ionization [5]. The Ta spectra are normalized t o the maximum channel content. It is seen, t h a t the Mu/Mp r a t i o is changing with the bombarding particle and with i t s energy. Studies on ion induced M satellite lines are r a t h e r scarce Ce. g. 61, b u t this field is worth f o r f u r t h e r experimental and theoretical investigations.
C9-82 JOURNAL
DE
PHYSIQUEchannel Fig. 4.--The Ta Ma and Mg lines obtained b y 2.0 MeV p r o t o n and 3.2 and 1.6 MeV ~ e + ion bombardment. I n s e r t : Si
+
3.2 MeV He+ Ka spectrum f o ri l l u s t r a t i o n O f t h e resolution of t h e system, The energy axis of t h e Si spectrum has t h e same calibration as t h a t o f t h e Ta spectrum. All s p e c t r a were taken with an ADP analyzer c r y s t a l .
Acknowledgments.
The work o f t h e crew o f t h e VdG laboratory is highly appreciated.
Thanks a r e due f o r t h e help in t h e long M-shell measurements t o B.
Sulik, L. Sarkadi, J. Palinkas and T. Papp.
R e f e r e n c e s .
113 RICHARDS, P., KAUFFMAN, R. L., MCGUIRE, J. H., MOORE, C. F., OLSEN, D. K., Phys. Rev. A8(1973)1369.
f21 SONOBE, B. I., Thesis, 1978, Texas A&M University.
f31 HIRSH,
F.
R. Jr., Phys. Rev. 38(1930914.141 CAUCHOIS, Y., SENEMAUD, C.,:Wavelengths o f X-ray Emission Lines and Absorption Edges. Pergamon Press, 1978, O x f o r d etc.
C ~ I SULIF, B.,
KADXR,
I., RICZ,s.,
VARGA, D., V ~ G H , J., HOCK, G., BERENYI,D., Nucl. I n s t r . Meth. B, t o be published161 ROSSEEL. T. M., DALE, J. M., HULETT, L. D.
