NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS NRA studies at the INP Tandem: Present status and perspectives M. Kokkoris 1, C. T. Papadopoulos 1, R. Vlastou 1, P. Misailides 2, S. Harissopulos 3, A. Lagoyannis 3 1 Department of Physics, National Technical University of Athens, Zografou Campus , Athens, Greece 2 Department of Chemistry, Aristotle University, GR-54006, Thessaloniki, Greece 3 Institute of Nuclear Physics, TANDEM Accelerator, N.C.S.R. ‘Demokritos’, Aghia Paraskevi , Athens, Greece Acknowledgements This project is co-funded by the European Social Fund (75%) and National Resources (25 %) - (EPEAEK - II) - PYTHAGORAS II, NTUA ΠΕΒΕ ‘Karatheodwris’, and is being carried out in collaboration with the IAEA, Vienna.

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS TOPICS: 1. BRIEF INTRODUCTION ON IBA AND NRA 2. NRA vs NBS 3. CURRENT STATUS (IBANDL) AND EFFORTS 4. WORK SUBMITTED BY OUR GROUP: A) EXPERIMENTAL SETUP A) EXPERIMENTAL SETUP B) ANALYSIS AND DISCUSSION B) ANALYSIS AND DISCUSSION 5.REVIEW OF RECENT CONTRIBUTIONS 6.CONCLUSIONS / FUTURE PERSPECTIVES

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS What is IBA? The term corresponds to a series of analytical techniques for material studies. Ion Beam Analysis (IBA) is based on the interaction, at both the atomic and the nuclear level, between accelerated charged particles and the bombarded material. This can lead to the emission of particles or radiation whose energy is characteristic of the elements which constitute the sample material. IBA PROFILING TECHNIQUES: Rutherford Backscattering Spectroscopy / Nuclear Backscattering Spectroscopy (RBS / NBS) / Channeling Elastic Recoil Detection Analysis (ERDA) Nuclear Reaction Analysis (standard NRA and resonant-PIGE)NON-PROFILING: Charged Particle Activation Analysis (CPAA), Particle Induced X/γ-Ray Emission (PIXE/PIGE) Neutron Activation Analysis (NAA), Secondary Ion Mass Spectroscopy (SIMS)  Most popular orientation for small electrostatic accelerators worldwide (>95%)

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS NRA: Well – established nowadays as one of the principal IBA techniques for accurate quantitative depth profiling of light elements in complex matrices. Based on the use of nuclear reactions. More frequently used: 1.(p,α): Low Q-value ( 6 Li, 9 Be, 10 B, 27 Al) and high Q-value ( 7 Li, 11 B, 18 O, 19 F, 23 Na, 31 P). No absorber foil can be applied. Highly selective. 2.(α,p): Very few elements have positive Q-values ( 10,11 B, 19 F, 23 Na, 27 Al, 31 P, 35 Cl) thus the background is severely reduced. Cross sections are high enough only at high beam energies. 3.(d,p) and (d,α): Almost all light isotopes have high positive Q-values. They permit simultaneous analysis of many light elements in complex matrices (e.g. C, O, N, B, S etc.) at the expense of peak overlaps or background interference in some cases. Require very low beam energies. Radiation safety precautions are mandatory because the (d,n) reaction channel is almost always open. 4.Less frequently used: (p,d), (p, 3 He), 3 He-NRA

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS NRA Characteristics: POSITIVE High isotopic selectivity Enhanced sensitivity for many elements Capability of least – destructive depth profiling with nanometer resolution The matrix is not a critical factor as in other IBA techniques Clear isolated peaks with practically no background is usually the case If the deuteron beam is adopted, one can achieve simultaneous analysis of most of the main light elements (C, O, N, F, B, Li)NEGATIVE   Not many / or discrepant cross sections available in literature, usually with high experimental errors   Theoretical evaluation is missing   Usually time-consuming studies, while radiation safety is sometimes an issue (d-NRA)   Not all the elements present low enough MDLs (typical sensitivities: 1:10 4 in atomic proportion)

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS NRA vs NBS – Which is preferable? Data acquisition is much faster in the case of NBS. Data acquisition is much faster in the case of NBS. Depth profiling is more accurate due to the lower energies (enhanced stopping power) generally involved (e.g. oxygen profiling using the 3.05 resonance in 16 O(α,α) rather than the 16 O(d,p 0,p 1,α 0 ) reactions). Depth profiling is more accurate due to the lower energies (enhanced stopping power) generally involved (e.g. oxygen profiling using the 3.05 resonance in 16 O(α,α) rather than the 16 O(d,p 0,p 1,α 0 ) reactions). Significantly more differential cross section data are available, over a wide range of beam energies and detector angles. Significantly more differential cross section data are available, over a wide range of beam energies and detector angles. For the most important elements with resonances in elastic scattering evaluated differential cross section data already exist. For the most important elements with resonances in elastic scattering evaluated differential cross section data already exist. Nevertheless NRA is still the only technique that can provide accurate results for the profiling of light elements when the matrix is complex.

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS The present situation of d-NRA: The theoretical complexities of d-NRA: Theta= M. Kokkoris et al. NIM B (2006) Favorablecase Severeproblems 1.Coexistence of many open reaction channels. 2.Electric charge asymmetry of the deuteron. 3.Multiple projectile-target exchange of nucleons. 4.Existence of direct exchange processes (e.g. knock-out, stripping). 5.Overlapping resonances.

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS EXPERIMENTAL SETUP: 5.5 MV HV Tandem Accelerator, N.C.S.R. ‘Demokritos’ Motor driven goniometer Great angular accuracy (0.01 deg.) * A.Pakou et al., Phys. Rev. Lett. 90 (2003)

 up to 8 single SSB, associated with standard NIM/CAMAC electronics. Upgrading is scheduled.  The current setup allows for target cooling with water or methanol through a closed circuit during acquisition  Voltage suppression up to 1000 V on the collimator, target and/or faraday cup.

RESULTS FOR d+ 10 B: More than ~2000 differential cross section values have been determined for 8 different detector angles (at 5º intervals), in beam energy steps of ~25 keV ( keV). Results already at IBANDL, (NIM B 2007, Parts A and B).

INTERESTING POINTS – PROBLEMS: Thick target smears out the resonance structure α 1 does not exist! A note should be made at IBANDL

INTERESTING POINTS – PROBLEMS:  Very strong and unknown resonance structure ( 34 Cl level scheme is missing!)  Disagreement with Healy et al. NIM B (1998) data from thick target yield deconvolution, very good agreement with digitized data from publication!  More than ~500 new data points at IBANDL  NIM B 2008 RESULTS FOR d+ 32 S:

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS RESULTS FOR d+ 11 B: INTERESTING POINTS:  Very smooth excitation curves – weak angular dependence  More than ~200 new data points for IBANDL  NIM B 2009 (in press)

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS Selected recent important works in the field of d-NRA: d-NRA of low-abundance isotopes, such as 13 C (1.1% in nat C) at 165 o and 135 o J.L. Colaux, T. Thomé and G. Terwagne, Nucl. Instrm. Meth. B254 (2007) Analysis of the most important levels of a top NRA candidate, 14 N, at 150 o. Also contributions for 27 Al. S. Pellegrino et al. NIM B (2004) 140 * Many PIGE studies as well (Z.Elekes et al. Nucl. Instr. & Meth. B168, 2000, 305 etc.)

NATIONAL TECHNICAL UNIVERSITY OF ATHENS DEPARTMENT OF PHYSICS CONCLUSIONS / FUTURE PERSPECTIVES: (a) d-NRA studies are very promising. Many open questions: Angular distribution at forward angles? (b) Study of 14 N in progress using the same technique. Studies of the d+ 6,7 Li systems are currently carried out. (c) Time-consuming studies affect quick quantification of the results. (d) In the next phase we also need to proceed to (p,α) reaction studies on 6,7 Li, 10,11 B, 19 F and 23 Na. (e) The theoretical evaluation – if accomplished – will considerably enhance NRA capabilities. (f) As far as NBS is concerned, (d,d 0 ) on 6,7 Li, and 10,11 B and (α,α 0 ) on 31 P, nat S, 39 K and nat Ca are scheduled in a 5-year plan in order to facilitate the data evaluation process.

To Joseph Salomon (AGLAE, Paris)…

Local Organizing Committee: P. Misaelides, F. Noli Aristotle University, Thessaloniki M. Kokkoris, R. Vlastou National Technical University of Athens A. G. Karydas, A. Lagoyannis, S. Harissopulos N.C.S.R. ‘Demokritos’ A. Godelitsas, A. Karabarbounis University of Athens 10 th European Conference on Accelerators in Applied Research and Technology to be held in Athens, Greece, September 2010