- Email: [email protected]
Accelerator-based research activities at “Centro Nacional de Aceleradores”, Seville (Spain)
Available online at www.sciencedirect.com
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 266 (2008) 2105–2109 www.elsevier.com/locate/nimb
Accelerator-based research activities at ‘‘Centro Nacional de Aceleradores”, Seville (Spain) M.A. Respaldiza a,b,*, F.J. Ager a,c, A. Carmona a,f, J. Ferrer a, M. Garcı´a-Leo´n a,b, J. Garcı´a-Lo´pez a,b, I. Garcı´a-Orellana a, B. Go´mez-Tubı´o a,d, Y. Morilla a, M.A. Ontalba a,e, I. Ortega-Feliu a,b a Centro Nacional de Aceleradores, Avd. Thomas A. Edison 7, E-41092 Sevilla, Spain Departmento de Fı´sica Ato´mica, Molecular y Nuclear, Universidad de Sevilla, Sevilla, Spain c Departmento de Fı´sica Aplicada I, Universidad de Sevilla, Sevilla, Spain d Departmento de Fı´sica Aplicada III, Universidad de Sevilla, Sevilla, Spain e Departmento de Fı´sica, Universidad de Extremadura, Ca´ceres, Spain f Laboratoire de Chimie Nucle´aire Analytique et Bioenvironnementale, Universite´ de Bordeaux, France b
Available online 13 March 2008
Abstract In February 1998, almost 10 years ago, the set-up of the first IBA (ion beam analysis) facility in Spain took place with the arrival of a 3 MV tandem accelerator [J. Garcı´a-Lo´pez, F.J. Ager, M. Barbadillo-Rank, F.J. Madrigal, M.A. Ontalba, M.A. Respaldiza, M.D. Ynsa, Nucl. Instr. and Meth. B 161–163 (2000) 1137]. Since then, an intensive research program using IBA techniques has been carried out. Subsequently, a cyclotron for 18 MeV protons has been also installed at the ‘‘Centro Nacional de Aceleradores” (CNA), devoted mainly to isotope production for PET (positron emission tomography) techniques, but possibly applied to material analysis and damage studies on a dedicated beam line. Moreover, a 1 MV tandem has been recently installed for AMS (accelerator mass spectrometry) 14C dating and environmental research with other isotopes. In the present paper we describe the new facilities and the developments of the 3 MV tandem beam lines occurred during the past years, as well as some examples of the most recent research activities in our Center in the fields of Material Science, Archaeometry, Biomedicine and Environment. Ó 2008 Elsevier B.V. All rights reserved. PACS: 29.17.+w; 29.20. c; 82.80. d; 07.30.Kf Keywords: Ion accelerators; Laboratory portrait; IBA techniques; PET; AMS
1. Introduction The CNA is a Spanish Centre for interdisciplinary research with accelerators. It is located in Seville, SouthWestern Spain and is jointly operated by the University * Corresponding author. Address: Centro Nacional de Aceleradores, Avd. Thomas A. Edison 7, E-41092 Sevilla, Spain. Tel.: +34 954 460 553; fax: +34 954 460 145. E-mail address: [email protected] (M.A. Respaldiza).
0168-583X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2008.02.080
of Seville, the Spanish CSIC (Consejo Superior de Investigaciones Cientı´ficas) and the Andalusian government. The CNA is open to collaborations with Universities, other public or private research institutions, hospitals, industrial companies, etc. Many groups from these institutions, mostly from Spain, but also from other countries, carry out their investigations at CNA. Research projects in Material Science, Biomedicine, Archaeology, Environmental Science, Nuclear Physics, etc. are undergoing at this Centre.
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2. Experimental facilities The first accelerator installed at the CNA was a 3 MV Tandem from NEC installed in 1998 and extensively described in [1]. Since then, only minor changes occurred in the accelerator itself, the main one being the recent acquisition of a third ion source, a duoplasmatron from NEC, that will be installed through the 0° port of the injection magnet, to complement the two present sources (alphatross and SNICS also from NEC). The beam lines have undergone more changes. The four initial ones have been upgraded with several minor improvements during these years and they have been completed with three new beam lines. We can briefly describe these new lines as follows (Fig. 1): (a) Irradiation chamber: This homemade scattering chamber has been designed to allow the irradiation of large areas (16 20 cm2) by raster scanning of the beam through magnetic deflection. It is a movable beam line, in such a way that the complete system can be easily transported to the cyclotron when irradiation with high energy protons is required. More details can be found in [2].
(b) Nuclear physics beam line: This beam line is used by groups of experimental nuclear physics, for the preparation of instruments to be used in international high energy facilities. Different scattering chambers are coupled to this line for testing vacuum system, detectors, acquisition systems, etc. (c) Ultra-high vacuum scattering chamber: In this ultra-high vacuum spherical chamber, IBA techniques can be complemented with surface analytical techniques, like XPS (X-Ray Photoelectron Spectroscopy). The UHV system allows to reach 10 10– 10 11 torr in such a way that real surface techniques can be applied. The system is connected to a second vacuum chamber, where samples can be prepared by different methods (ion and electron bombardment, etc) and sent directly to the measurement chamber without any breakdown of the vacuum. The second laboratory installed at the CNA was built around a cyclotron accelerator (model cyclone 18/9 from the IBA Company) received in January 2004. The objectives of this new facility are:
Fig. 1. Schematic layout of the acceleration system and experimental beam lines of the 3 MV tandem laboratory.
M.A. Respaldiza et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2105–2109
1. The production of the radioisotopes needed for PET and the chemical synthesis of pharmaceuticals labelled with 11C, 13N, 15O and 18F. 2. The proton irradiation techniques of technological and biological samples, for radiation damage and ion implantation studies (research beam line). 3. Small animals scanning with PET technique. 4. Developments of new drugs with PET studies. The new facility comprises two vaults for the cyclotron itself and the materials irradiation chamber, laboratories for radiopharmacy and quality control and two scanning rooms. The cyclotron is a negative ion machine able to accelerate protons/deuterons up to 18 and 9 MeV, respectively. It has eight target ports, seven of which are dedicated to short half life radioisotopes production and the eighth is used for beam transport to the research beam line vault. The research beam line of the cyclotron is formed by two sections. The first one is placed inside the cyclotron vault and consists of a quadrupole doublet and a beam shutter right in front of the vacuum line, allowing the beam to reach the second vault through a 2 m thick wall. In this way, the R & D vault can be accessed even during radioisotope production by shutting the beam. The second section is placed in the R & D vault and consists of a quadrupole and the irradiation chamber mentioned previously when describing the tandem beam lines. In Fig. 2 a general layout of the cyclotron bunker is shown. Eight shielded hot cells from the Italian company Comecer for radiopharmaceutical synthesis have been installed also at CNA. Three of them are installed in a separate laboratory for commercial 18F-fludesoxiglucosa (FDG) synthesis and dose dispensing. The others are installed in the so-called ‘‘research laboratory” and host chemical modules
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made by nuclear interface-general electric for the synthesis 13 NH3, methylation of 11C compounds, of FDG, H15 2 O, and molecules obtained through electrophilic and nucleophilic substitution reactions with fluorine. The strict pharmaceutical and radioprotection regulations, some of them contradictory, have forced us to develop a very complex ventilation system to comply with both simultaneously. The laboratory has been completed with a PET tomograph to explore small animals (Model Philips Mosaic) allowing us to fruitfully use of the very short half-life isotopes for different research programs. The third laboratory installed at the CNA has been the accelerator mass spectrometry (AMS) system. So far, our AMS accelerator is able to measure 10Be, 14C, 26Al, 129I and Pu-isotopes for different purposes. A full description of the spectrometer, technical features and applications are given elsewhere in these proceedings [3]. 3. Research activities During the last years a very intensive interdisciplinary research program has been developed at the CNA in four main fields: 3.1. Materials science In collaboration with a large number of Research Centers in Spain and abroad, many studies on materials analysis and modification have been carried out during these years, including practically all kinds of materials: metallic alloys, semiconductors, superconductors, insulators, compound materials and ceramics. In particular, an extensive research on silicon carbide (SiC) is being performed. Silicon carbide is a semiconductor material of great
Fig. 2. Layout of the cyclotron hall at the CNA.
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technological interest due to its wide band gap, large thermal conductivity, high electron mobility and high breakdown voltage. These properties make possible its use in high power, high temperature and high frequency applications where silicon can not operate [4]. However, SiC poses a number of new processing problems. Due to the very low diffusivity of dopants at T < 1800 °C, ion implantation is a must and the defects induced as well as their annealing properties should be studied. In the past years, we have extensively studied the structural properties of SiC single crystals as a function of the implantation conditions. In some cases, it may be important to determine independently the damage produced on the carbon and silicon sub-lattices, since the displacement threshold energies for Si and C are different. The widely used Rutherford backscattering spectrometry technique in channelling geometry provides only information about the silicon sub-lattice, as the small carbon signal appears on the high background of silicon. We have studied the carbon sub-lattice by means of the non-Rutherford backscattering/ channeling technique making use of the elastic resonance 12 C(a, a) 12C at 4.26 MeV [5]. The sensitivity of the method for carbon measurements is enhanced by a factor 100 due to the resonance cross section [6] and this enhancement is of prime importance when very small ion doses are implanted. The damage produced in the SiC material during the implantation of Al+ ions at 200 keV and room temperature was studied by means of RBS/Channeling. Spectra were recorded at 4300 keV for implanted samples with doses of 4 1014 and 1016 Al/cm2 and compared with the spectra of an amorphous SiC and a non implanted single crystal. From them it can be seen how the superficial region of the implanted sample at higher dose has been amorphized and the defects density is much less, but appreciable, for the implanted sample at lower dose. By changing the incident beam energy step by step above the resonance energy and determining the peak area versus beam energy, the depth distribution of displaced carbon atoms can be obtained, which is related to the damage profile. The maximum damage appears at the depth of the projected range of the ions. The recovery of the original structure after the annealing process was also studied. The implanted samples were annealed at 1200 °C in Ar atmosphere for one hour. Our results show that the crystalline structure is fully recovered for samples implanted with a low dose, whereas for higher doses the recovery is partial in the deeper interface and negligible close to the surface. 3.2. Arts and archaeometry A large research program has been undertaken in collaboration with different Museums of Seville and the Prehistoric and Archaeological Department of the University of Seville. Many different types of materials have been characterised at the CNA by using IBA techniques, taking advantage of their non-destructive character. AMS for 14C dating is starting also to be used in different research projects.
Ceramics, pigments, manuscripts, marbles, metallic alloys and a large list of other materials have been analysed mainly using the external microbeam line of the 3 MV tandem. However the most complete research program at the CNA in this field has been the study of gold alloys in jewellery objects of the Tartesic period in the South of the Iberian Peninsula. In the next paragraphs we will try to describe briefly the main features of these studies. During the last years, in the frame of different research projects, most of the important jewellery sets found in archaeological sites in the region have been analysed by our research group using PIXE (Particle Induced X-Ray Emission) [7]. This collection is representative of the gold work accomplished in the valley of the Guadalquivir river by the Tartesic and Turdetan people (7th–2nd centuries B.C.). Other investigated samples are funerary collections of Phoenician and Punic tombs in Ca´diz [8] and ‘‘El Carambolo” treasure (Camas, Sevilla) [9], representative of the period of oriental influence in the valley of the Guadalquivir river (7th–6th centuries B.C.) (in this last case using portable XRF). The general result of the many jewelry sets analyzed from the south Iberian Peninsula is that most of the gold alloys used for their manufacture are very rich in gold, over 70 wt.% with half of them even richer with more than 90 wt.%. Copper is found to be around 2.5 wt.% and the rest corresponding to silver. Trace elements have not appeared in the alloy as a characteristic of the samples, therefore we can state that the most common gold alloy used for manufacturing jewelry items in south Iberian Peninsula between 7th and 3rd centuries BC, was very pure in gold, with some silver and copper. However there are some exceptions coming from the same geographical area (Ca´diz), being all of the items kept in the Museum of Ca´diz [8,10]. Palladium was found as a trace element in two items that belong to a group of elaborated Punic pendant earrings. Palladium was detected and quantified (up to 0.7 wt.%) systematically in all the analysed areas of these two objects. From geological and archaeological considerations it is concluded that very special ore brought to the area of Ca´diz probably from alluvial placers from the former West African Gold Coast or NW Iberia, or more unlikely from Eastern Africa or Near East. Thanks to the good beam focalisation obtained with the external microbeam of the CNA, it has been also possible to study the decorative techniques of granulations and filigranes employed for the production of most of the analysed jewels [7]. The soldering procedures have been identified in several cases and only two procedures (gold fusion and local use of Ag/Cu alloy in the soldering points) have been found by now. 3.3. Biomedicine Although applications to biomedicine are probably our less developed field, there has been also an important activity in this area. There were interesting studies on osteoporosis preventive treatments [11], on the characterisation of
M.A. Respaldiza et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2105–2109
metals in samples of human teeth, on Pt distribution in human cells for oncological treatment and more recently a study of heavy metals in neurons [12]. 3.4. Environmental science In the field of Environmental Sciences, studies concerning sediment and aerosol analysis are regularly carried out at the CNA [13,14]. Together with these, a few more specific research projects are undertaken. One of them is the metal localization and quantification in the plant Arabidopsis thaliana, in both natural and transgenic lines, with the purpose of soil remediation [15,16]. 4. Conclusion The growing activity of the ‘‘Centro Nacional de Aceleradores” during the last decade is shown in this paper, together with some relevant applications. Starting with a 3 MV tandem accelerator with four beam lines, the Centre is operating now three different machines with many active experimental beam lines, covering most of the ion beam analysis and ion beam modification techniques. Research projects in practically all scientific areas were and are being performed at the same time as the potential of the Centre increases continuously. Acknowledgements Thanks are due to the three host Institutions, Universidad de Sevilla, Junta de Andalucı´a and CSIC, for the continuous support given to our Centre. Also, the competent and friendly cooperation of a large list (too large to be listed here) of colleagues that during all these years visited us to work in different projects or gave us excellent advices, has been of great help and is most appreciated.
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References [1] J. Garcı´a-Lo´pez, F.J. Ager, M. Barbadillo-Rank, F.J. Madrigal, M.A. Ontalba, M.A. Respaldiza, M.D. Ynsa, Nucl. Instr. and Meth. B 161–163 (2000) 1137. [2] A. Ferrero, J. Garcı´a Lo´pez, M.A. Respaldiza, in: Proceedings of the Workshop Radiation Effects on Components and Systems 2004, pp. 343–345. ISBN 84-930056-1-4. [3] E. Chamizo et al., Nucl. Instr. and Meth. B 266 (2008) 2217. [4] Zhe Chuan Feng, SiC Power Materials, Devices and Applications, Springer-Verlag, 2004, ISBN 3-540-20666-3. [5] G. Battistig, J. Garcı´a Lo´pez, N.Q. Kha´nh, Y. Morilla, M.A. Respaldiza, E. Szila´gyi, Mater. Sci. Forum 433–436 (2003) 625. [6] A.F. Gurbich, Nucl. Instr. and Meth. B 161–163 (2000) 125. [7] M.A. Ontalba, F.J. Ager, M.D. Ynsa, B. Go´mez-Tubı´o, M.A. Respaldiza, F. Ferna´ndez-Go´mez, M.L. Bandera, G.W. Grime, Nucl. Instr. and Meth. B 181 (2001) 664. [8] M.A. Ontalba Salamanca, B. Go´mez-Tubı´o, I. Ortega-Feliu, M.A. Respaldiza, M. Luisa de la Bandera, G. Ovejero Zappino, A. Bouzas, A. Go´mez-Moro´n, Nucl. Instr. and Meth. B 249 (2006) 622. [9] M.A. Ontalba Salamanca, B. Go´mez Tubı´o, M.A. Respaldiza, F. Ferna´ndez Go´mez, in: C. Rolda´n (Ed.), Ana´lisis del tesoro de ‘‘El Carambolo” mediante un equipo porta´til de fluorescencia de rayos X, Actas del IV Congreso Nacional de Arqueometrı´a, Universidad de Valencia, C.D. Deposito legal no. V-247-2002, p. 176. ´ . Ontalba-Salamanca, M.A ´. [10] I. Ortega-Feliu, B. Go´mez-Tubı´o, M.A Respaldiza, M.L. de la Bandera, G. Ovejero-Zappino, Nucl. Instr. and Meth. B 260 (2007) 329. [11] M.D. Ynsa, T. Pinhero, F.J. Ager, L.C. Alve´s, J.C. Milla´n, M.A. Go´mez-Zubeldia, M.A. Respaldiza, Nucl. Instr. and Meth. B 189 (2002) 431. [12] R. Ortega, M.-C. Biston, G. Deve`s, S. Bohic, A. Carmona, Nucl. Instr. and Meth. B 231 (2005) 321. [13] J.E. Martı´n, M.A. Respaldiza, J. Gonza´lez-Labajo, Nucl. Instr. and Meth. B 188 (2002) 102. [14] I. Garcı´a-Orellana, M.A. Respaldiza, S. Nava, F. Lucarelli, in: Milos Budnar, Matjaz Kavcic (Eds.), Proceedings of the 10th International Conference on Particle-Induced X-Ray Emission and its Analytical Application, ISBN 961-6303-62-7, 503.1, Ljubljana, 2004. [15] F.J. Ager, M.D. Ynsa, J.R. Dominguez-Solis, C. Gotor, M.A. Respaldiza, L.C. Romero, Nucl. Instr. and Meth. B 189 (2002) 494. [16] F.J. Ager, M.D. Ynsa, J.R. Domı´nguez-Solı´s, M.C. Lo´pez-Martı´n, C. Gotor, L.C. Romero, Nucl. Instr. and Meth. B 210 (2003) 401.
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 266 (2008) 2105–2109 www.elsevier.com/locate/nimb
Accelerator-based research activities at ‘‘Centro Nacional de Aceleradores”, Seville (Spain) M.A. Respaldiza a,b,*, F.J. Ager a,c, A. Carmona a,f, J. Ferrer a, M. Garcı´a-Leo´n a,b, J. Garcı´a-Lo´pez a,b, I. Garcı´a-Orellana a, B. Go´mez-Tubı´o a,d, Y. Morilla a, M.A. Ontalba a,e, I. Ortega-Feliu a,b a Centro Nacional de Aceleradores, Avd. Thomas A. Edison 7, E-41092 Sevilla, Spain Departmento de Fı´sica Ato´mica, Molecular y Nuclear, Universidad de Sevilla, Sevilla, Spain c Departmento de Fı´sica Aplicada I, Universidad de Sevilla, Sevilla, Spain d Departmento de Fı´sica Aplicada III, Universidad de Sevilla, Sevilla, Spain e Departmento de Fı´sica, Universidad de Extremadura, Ca´ceres, Spain f Laboratoire de Chimie Nucle´aire Analytique et Bioenvironnementale, Universite´ de Bordeaux, France b
Available online 13 March 2008
Abstract In February 1998, almost 10 years ago, the set-up of the first IBA (ion beam analysis) facility in Spain took place with the arrival of a 3 MV tandem accelerator [J. Garcı´a-Lo´pez, F.J. Ager, M. Barbadillo-Rank, F.J. Madrigal, M.A. Ontalba, M.A. Respaldiza, M.D. Ynsa, Nucl. Instr. and Meth. B 161–163 (2000) 1137]. Since then, an intensive research program using IBA techniques has been carried out. Subsequently, a cyclotron for 18 MeV protons has been also installed at the ‘‘Centro Nacional de Aceleradores” (CNA), devoted mainly to isotope production for PET (positron emission tomography) techniques, but possibly applied to material analysis and damage studies on a dedicated beam line. Moreover, a 1 MV tandem has been recently installed for AMS (accelerator mass spectrometry) 14C dating and environmental research with other isotopes. In the present paper we describe the new facilities and the developments of the 3 MV tandem beam lines occurred during the past years, as well as some examples of the most recent research activities in our Center in the fields of Material Science, Archaeometry, Biomedicine and Environment. Ó 2008 Elsevier B.V. All rights reserved. PACS: 29.17.+w; 29.20. c; 82.80. d; 07.30.Kf Keywords: Ion accelerators; Laboratory portrait; IBA techniques; PET; AMS
1. Introduction The CNA is a Spanish Centre for interdisciplinary research with accelerators. It is located in Seville, SouthWestern Spain and is jointly operated by the University * Corresponding author. Address: Centro Nacional de Aceleradores, Avd. Thomas A. Edison 7, E-41092 Sevilla, Spain. Tel.: +34 954 460 553; fax: +34 954 460 145. E-mail address: [email protected] (M.A. Respaldiza).
0168-583X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2008.02.080
of Seville, the Spanish CSIC (Consejo Superior de Investigaciones Cientı´ficas) and the Andalusian government. The CNA is open to collaborations with Universities, other public or private research institutions, hospitals, industrial companies, etc. Many groups from these institutions, mostly from Spain, but also from other countries, carry out their investigations at CNA. Research projects in Material Science, Biomedicine, Archaeology, Environmental Science, Nuclear Physics, etc. are undergoing at this Centre.
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M.A. Respaldiza et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2105–2109
2. Experimental facilities The first accelerator installed at the CNA was a 3 MV Tandem from NEC installed in 1998 and extensively described in [1]. Since then, only minor changes occurred in the accelerator itself, the main one being the recent acquisition of a third ion source, a duoplasmatron from NEC, that will be installed through the 0° port of the injection magnet, to complement the two present sources (alphatross and SNICS also from NEC). The beam lines have undergone more changes. The four initial ones have been upgraded with several minor improvements during these years and they have been completed with three new beam lines. We can briefly describe these new lines as follows (Fig. 1): (a) Irradiation chamber: This homemade scattering chamber has been designed to allow the irradiation of large areas (16 20 cm2) by raster scanning of the beam through magnetic deflection. It is a movable beam line, in such a way that the complete system can be easily transported to the cyclotron when irradiation with high energy protons is required. More details can be found in [2].
(b) Nuclear physics beam line: This beam line is used by groups of experimental nuclear physics, for the preparation of instruments to be used in international high energy facilities. Different scattering chambers are coupled to this line for testing vacuum system, detectors, acquisition systems, etc. (c) Ultra-high vacuum scattering chamber: In this ultra-high vacuum spherical chamber, IBA techniques can be complemented with surface analytical techniques, like XPS (X-Ray Photoelectron Spectroscopy). The UHV system allows to reach 10 10– 10 11 torr in such a way that real surface techniques can be applied. The system is connected to a second vacuum chamber, where samples can be prepared by different methods (ion and electron bombardment, etc) and sent directly to the measurement chamber without any breakdown of the vacuum. The second laboratory installed at the CNA was built around a cyclotron accelerator (model cyclone 18/9 from the IBA Company) received in January 2004. The objectives of this new facility are:
Fig. 1. Schematic layout of the acceleration system and experimental beam lines of the 3 MV tandem laboratory.
M.A. Respaldiza et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2105–2109
1. The production of the radioisotopes needed for PET and the chemical synthesis of pharmaceuticals labelled with 11C, 13N, 15O and 18F. 2. The proton irradiation techniques of technological and biological samples, for radiation damage and ion implantation studies (research beam line). 3. Small animals scanning with PET technique. 4. Developments of new drugs with PET studies. The new facility comprises two vaults for the cyclotron itself and the materials irradiation chamber, laboratories for radiopharmacy and quality control and two scanning rooms. The cyclotron is a negative ion machine able to accelerate protons/deuterons up to 18 and 9 MeV, respectively. It has eight target ports, seven of which are dedicated to short half life radioisotopes production and the eighth is used for beam transport to the research beam line vault. The research beam line of the cyclotron is formed by two sections. The first one is placed inside the cyclotron vault and consists of a quadrupole doublet and a beam shutter right in front of the vacuum line, allowing the beam to reach the second vault through a 2 m thick wall. In this way, the R & D vault can be accessed even during radioisotope production by shutting the beam. The second section is placed in the R & D vault and consists of a quadrupole and the irradiation chamber mentioned previously when describing the tandem beam lines. In Fig. 2 a general layout of the cyclotron bunker is shown. Eight shielded hot cells from the Italian company Comecer for radiopharmaceutical synthesis have been installed also at CNA. Three of them are installed in a separate laboratory for commercial 18F-fludesoxiglucosa (FDG) synthesis and dose dispensing. The others are installed in the so-called ‘‘research laboratory” and host chemical modules
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made by nuclear interface-general electric for the synthesis 13 NH3, methylation of 11C compounds, of FDG, H15 2 O, and molecules obtained through electrophilic and nucleophilic substitution reactions with fluorine. The strict pharmaceutical and radioprotection regulations, some of them contradictory, have forced us to develop a very complex ventilation system to comply with both simultaneously. The laboratory has been completed with a PET tomograph to explore small animals (Model Philips Mosaic) allowing us to fruitfully use of the very short half-life isotopes for different research programs. The third laboratory installed at the CNA has been the accelerator mass spectrometry (AMS) system. So far, our AMS accelerator is able to measure 10Be, 14C, 26Al, 129I and Pu-isotopes for different purposes. A full description of the spectrometer, technical features and applications are given elsewhere in these proceedings [3]. 3. Research activities During the last years a very intensive interdisciplinary research program has been developed at the CNA in four main fields: 3.1. Materials science In collaboration with a large number of Research Centers in Spain and abroad, many studies on materials analysis and modification have been carried out during these years, including practically all kinds of materials: metallic alloys, semiconductors, superconductors, insulators, compound materials and ceramics. In particular, an extensive research on silicon carbide (SiC) is being performed. Silicon carbide is a semiconductor material of great
Fig. 2. Layout of the cyclotron hall at the CNA.
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technological interest due to its wide band gap, large thermal conductivity, high electron mobility and high breakdown voltage. These properties make possible its use in high power, high temperature and high frequency applications where silicon can not operate [4]. However, SiC poses a number of new processing problems. Due to the very low diffusivity of dopants at T < 1800 °C, ion implantation is a must and the defects induced as well as their annealing properties should be studied. In the past years, we have extensively studied the structural properties of SiC single crystals as a function of the implantation conditions. In some cases, it may be important to determine independently the damage produced on the carbon and silicon sub-lattices, since the displacement threshold energies for Si and C are different. The widely used Rutherford backscattering spectrometry technique in channelling geometry provides only information about the silicon sub-lattice, as the small carbon signal appears on the high background of silicon. We have studied the carbon sub-lattice by means of the non-Rutherford backscattering/ channeling technique making use of the elastic resonance 12 C(a, a) 12C at 4.26 MeV [5]. The sensitivity of the method for carbon measurements is enhanced by a factor 100 due to the resonance cross section [6] and this enhancement is of prime importance when very small ion doses are implanted. The damage produced in the SiC material during the implantation of Al+ ions at 200 keV and room temperature was studied by means of RBS/Channeling. Spectra were recorded at 4300 keV for implanted samples with doses of 4 1014 and 1016 Al/cm2 and compared with the spectra of an amorphous SiC and a non implanted single crystal. From them it can be seen how the superficial region of the implanted sample at higher dose has been amorphized and the defects density is much less, but appreciable, for the implanted sample at lower dose. By changing the incident beam energy step by step above the resonance energy and determining the peak area versus beam energy, the depth distribution of displaced carbon atoms can be obtained, which is related to the damage profile. The maximum damage appears at the depth of the projected range of the ions. The recovery of the original structure after the annealing process was also studied. The implanted samples were annealed at 1200 °C in Ar atmosphere for one hour. Our results show that the crystalline structure is fully recovered for samples implanted with a low dose, whereas for higher doses the recovery is partial in the deeper interface and negligible close to the surface. 3.2. Arts and archaeometry A large research program has been undertaken in collaboration with different Museums of Seville and the Prehistoric and Archaeological Department of the University of Seville. Many different types of materials have been characterised at the CNA by using IBA techniques, taking advantage of their non-destructive character. AMS for 14C dating is starting also to be used in different research projects.
Ceramics, pigments, manuscripts, marbles, metallic alloys and a large list of other materials have been analysed mainly using the external microbeam line of the 3 MV tandem. However the most complete research program at the CNA in this field has been the study of gold alloys in jewellery objects of the Tartesic period in the South of the Iberian Peninsula. In the next paragraphs we will try to describe briefly the main features of these studies. During the last years, in the frame of different research projects, most of the important jewellery sets found in archaeological sites in the region have been analysed by our research group using PIXE (Particle Induced X-Ray Emission) [7]. This collection is representative of the gold work accomplished in the valley of the Guadalquivir river by the Tartesic and Turdetan people (7th–2nd centuries B.C.). Other investigated samples are funerary collections of Phoenician and Punic tombs in Ca´diz [8] and ‘‘El Carambolo” treasure (Camas, Sevilla) [9], representative of the period of oriental influence in the valley of the Guadalquivir river (7th–6th centuries B.C.) (in this last case using portable XRF). The general result of the many jewelry sets analyzed from the south Iberian Peninsula is that most of the gold alloys used for their manufacture are very rich in gold, over 70 wt.% with half of them even richer with more than 90 wt.%. Copper is found to be around 2.5 wt.% and the rest corresponding to silver. Trace elements have not appeared in the alloy as a characteristic of the samples, therefore we can state that the most common gold alloy used for manufacturing jewelry items in south Iberian Peninsula between 7th and 3rd centuries BC, was very pure in gold, with some silver and copper. However there are some exceptions coming from the same geographical area (Ca´diz), being all of the items kept in the Museum of Ca´diz [8,10]. Palladium was found as a trace element in two items that belong to a group of elaborated Punic pendant earrings. Palladium was detected and quantified (up to 0.7 wt.%) systematically in all the analysed areas of these two objects. From geological and archaeological considerations it is concluded that very special ore brought to the area of Ca´diz probably from alluvial placers from the former West African Gold Coast or NW Iberia, or more unlikely from Eastern Africa or Near East. Thanks to the good beam focalisation obtained with the external microbeam of the CNA, it has been also possible to study the decorative techniques of granulations and filigranes employed for the production of most of the analysed jewels [7]. The soldering procedures have been identified in several cases and only two procedures (gold fusion and local use of Ag/Cu alloy in the soldering points) have been found by now. 3.3. Biomedicine Although applications to biomedicine are probably our less developed field, there has been also an important activity in this area. There were interesting studies on osteoporosis preventive treatments [11], on the characterisation of
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metals in samples of human teeth, on Pt distribution in human cells for oncological treatment and more recently a study of heavy metals in neurons [12]. 3.4. Environmental science In the field of Environmental Sciences, studies concerning sediment and aerosol analysis are regularly carried out at the CNA [13,14]. Together with these, a few more specific research projects are undertaken. One of them is the metal localization and quantification in the plant Arabidopsis thaliana, in both natural and transgenic lines, with the purpose of soil remediation [15,16]. 4. Conclusion The growing activity of the ‘‘Centro Nacional de Aceleradores” during the last decade is shown in this paper, together with some relevant applications. Starting with a 3 MV tandem accelerator with four beam lines, the Centre is operating now three different machines with many active experimental beam lines, covering most of the ion beam analysis and ion beam modification techniques. Research projects in practically all scientific areas were and are being performed at the same time as the potential of the Centre increases continuously. Acknowledgements Thanks are due to the three host Institutions, Universidad de Sevilla, Junta de Andalucı´a and CSIC, for the continuous support given to our Centre. Also, the competent and friendly cooperation of a large list (too large to be listed here) of colleagues that during all these years visited us to work in different projects or gave us excellent advices, has been of great help and is most appreciated.
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