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U zadnjih nekoliko godina monokristalni dijamantni detektori visoke čistoće postal su komercijalno dostupni. Oni se proizvode metodom depozicije iz parne faze (CVD – Chemical Vapor Deposition) i pokazuju dobru energijsku i vremensku razlučivost zbog odlične uniformnosti kristalne rešetke. U teškim radnim uvjetima, kao što su visoka temperature i povišena razina zračenja, očekuje se da dijamantni detektori zadržavaju svoje karakteristike te bi se ubuduće mogli primijeniti u slučajevima kad se silicijski detektori ne mogu koristiti ili se njihova spektroskopska svojstva naglo kvare. Metoda mjerenja induciranog naboja kojeg proizvede pojedinačni ion prolaskom kroz poluvodički element (IBIC – Ion Beam Induced Charge) veoma je prikladna za proučavanje efikasnosti sakupljanja naboja (CCE – Charge Collection Efficiency) na mikroskopskoj razini, prije i nakon ozračavanja detektora. Promjene CCE vrijednosti komercijalnog monokristalnog CVD dijamantnog detektora (1 mm^2 površine i 500 um debljine) s ohmskim električnim kontaktima proučavane su s fokusiranim ionskim snopovima. Korištenjem različitih iona (protona i ugljika) i energija, postignute su različite dubinske raspodjele kočenja ionizacijom. Teorija neionizirajućeg gubitka energije (NIEL – Non-Ionizing Energy Loss) korištena je za mjerenje otpornosti na zračenje, u svrhu čega su različita područja detektora ozračena s 6.5 MeV fokusiranim ugljikovim snopom i to dozama do 10^11 iona/cm^2. Naknadno je izmjerena energijska razlučivost od 25 keV (1.25 %) za detekciju 2 MeV-skih protona na cijeloj aktivnoj površini dijamantnog detektora. U ovom radu po prvi put je korištenjem IBIC metode sistematski proučavano uvođenje defekata s teškim ionima MeV-skih energija u monokristalni CVD dijamantni detektor. Suprotno ponašanju na visokim energijama (>1 GeV za protone), a uspoređujući rezultate sa silicijskim detektorom, za područje energija teških iona kratkog dosega (nekoliko mikrometara) utvrđena je slabija otpornost na zračenje dijamantnog detektora.

Deposition of large energy density at precisely defined area, by using low beam currents or even single ion irradiations, offers attractive possibilities for patterning with swift heavy ion microbeams. With a versatile ion microbeam setup, the 6 MV Tandem Van de Graaff accelerator at RBI Zagreb offers a wide range of ion species and energies that can be focused down to the submicrometer beam spot size. For the successful single ion irradiation, a reliable detection of swift heavy ion impact is necessary. This has to be accomplished both in transmission (for thin targets) as well as for the thick samples. In the case of thin targets, transmitted swift heavy ions are detected by conventional silicon particle detector, whereas for thick targets, ion impact is registered by detection of ejected secondary electrons. The current status of ion microbeam setup at RBI, Zagreb with an emphasis on low beam current operation and single ion irradiations is given. Test measurements of 10 MeV oxygen ions focused with upgraded system of magnetic quadrupole lenses in quintuplet configuration show 300 nm lateral resolution. In addition, several examples of materials patterning with our upgraded setup are presented.

A high purity single crystal diamond detector for spectroscopy, produced by a chemical vapor deposition (CVD) process, became recently commercially available. These detectors show good energy resolution and superior timing properties for charge particle detection due to excellent crystal uniformity. These devices should maintain their characteristics in harsh environments (e.g. high temperatures, elevated radiation, etc.), and therefore could be used in future applications when silicon detector either cannot operate, or their spectroscopic performance deteriorates fast. The ion beam induced charge (IBIC) technique preformed at the ion microprobe is a very suitable tool for studies of the charge collection efficiency (CCE) properties at microscopic level. IBIC can be also used for a radiation hardness testing during and after irradiation process. An energy resolution of 1.4 % was obtained for the 3 MeV proton detection over the whole active area of the pristine scCVD diamond detector (1 mm^2 surface area and 500 μm thickness). Inhomogeneities of the CCE spatial distribution in diamond single crystal have been studied by different ions (protons, carbon and silicon) in the energy range (1-15 MeV), having different ionization depth profiles. Non Ionizing Energy Loss (NIEL) concept was used for studies of the induced charge value decrease and the energy resolution deterioration obtained with selectively irradiated detectors with various focused ion beams up to fluences of 1011 ions/cm^2. These results are needed to assess the radiation hardness of diamond for MeV heavy ion detection. In addition, diamond and silicon radiation hardness will be compared on basis of our previously obtained results for silicon particle detectors. Problems associated with the polarization effect in diamond, which is a specific problem of diamond detectors, will be discussed as well.

High purity single crystal diamond detectors for spectroscopy, produced by a chemical vapor deposition (CVD) process, became recently commercially available. These detectors show good energy resolution and superior timing properties for charge particle detection due to excellent crystal uniformity. These devices should maintain their characteristics in harsh environments (e.g. high temperatures, elevated radiation, etc.), and therefore could be used in future applications when silicon detector either cannot operate, or their spectroscopic performance deteriorates fast. The ion beam induced charge (IBIC) technique preformed at the ion microprobe is a very suitable tool for studies of the charge collection efficiency (CCE) properties at microscopic level. IBIC can be also used for a radiation hardness testing during and after irradiation process. Inhomogeneities of the CCE spatial distribution in commercial scCVD diamond detector (1 mm^2 area, 500 μm thickness) with novel Ohmic electrical contact have been studied by different ions: 430 keV and 2 MeV protons, as well as 6.5 MeV carbon, having different ionization depth profiles. Non Ionizing Energy Loss (NIEL) concept was used to assess the radiation hardness test obtained by selectively irradiating detector with 6.5 MeV focused carbon beam up to fluencies of 10^11 ions/cm^2. In addition, an energy resolution of 1.4 % was obtained for the 3 MeV proton detection over the whole active area of the pristine scCVD diamond detector. This report is the first systematic IBIC study of MeV heavy ion induced radiation damage in single crystal diamond. Preliminary results do not confirm better radiation hardness of diamond comparing to silicon for detection of short range heavy ions.

A bronze statue of the athlete with a strigil - the Apoxiomenos - was discovered at the seabed of the North Adriatic in 1999. The statue was complete, with the majority of the surface being covered with a layer of corrosion products and substantial quantities of organic limestone. These deposits protected the bronze from electro-chemical deterioration, although the back of the statue, which was buried in the sand, was to a large extent corroded. After the slow desalination process, the restoration and conservation process started in October 2000, as a joint project between Croatian Conservation Institute (HRZ), Zagreb and Opificio delle Pietre Dure (OPD), Florence. OPD has also performed comprehensive investigations of the statue by many physical and chemical methods [1]. The restoration process was completed in 2005 when the statue was exhibited for the first time. Among the large number of analyses performed during restoration by OPD [1], probably the most important was 14C AMS carbon dating of organic material (seeds) found inside of the statue. According to results of three samples, the sample age is between 100 B.C and 250 A.D. which proved the high historical value and importance of this statue. However, many questions about the origin of the statue, called now the Croatian Apoxiomenos, remained still to be resolved. Our more recent work on the analysis of bronze composition that is presented here will try to reveal part of the mystery of this exceptional ancient work of art.

Električka svojstva i efikasnost sakupljanja naboja Hamamatsu S5821 silicijskih fotodioda proučavana su nakon ozračavanja fokusiranim snopovima H, He, Li, O i Cl iona. Vrsta i pripadajuća energija (~ 0.4 MeV/u) iona su takvi da je doseg iona u siliciju ~ 5 mikrometara unutar područja osiromašenja fotodiode. Integrirani tok (doza) različitih iona kreće su u rasponu 108 – 1012 cm-2, a vrijednosti ionskih doza su takve da se ukupne vrijednosti deponirane energije ionskog snopa utrošene za oštećenje pomakom u materijalu (apsorbirana doza) Dd u rasponu 1010 – 1013 MeV/g . Provedenim električkim mjerenjima opažen je najveći porast kapaciteta kod fotodiode ozračene ionima vodika. U siliciju n-tipa koji je ozračen niskoenergijskim ionima vodika, i nije naknadno termički obrađivan, nastaju donorska stanja koji sadrže implantirani vodik. Porast generacijske komponente zaporne struje u fotodiodama ozračenim različitim fokusiranim ionskim snopovima, ali jednake vrijednosti apsorbirane doze, raste s masom iona. Prema teoriji neionizirajućeg gubitka energije (engl. Non-Ionizing Energy Loss - NIEL), dobiveni rezultati pokazuju da je efikasnost stvaranja rekombinacijskih stanja unutar energijskog procijepa poluvodiča proporcionalna gustoći stvorenih vakancija za svaki pojedini ion projektil. Eksperimentalna metoda mjerenja induciranog naboja kojeg proizvode pojedinačni ioni prolaskom kroz poluvodički element (engl. Ion Beam Induced Charge -IBIC) korištena je za određivanje amplitude induciranog naboja i proučavanje efikasnosti sakupljanja naboja (engl. Charge Collection Efficiency - CCE) ozračenih fotodioda. Promjene CCE vrijednosti fotodioda uzrokovane njihovim ozračavanjem fokusiranim ionskim snopovima proučavane su u skladu s NIEL teorijom koja previđa promjene inducirane struje (naboja) proporcionalne apsorbiranoj energiji ionizirajućeg zračenja utrošenoj za oštećenje pomakom u poluvodičkom materijalu. Za matematičku prilagodbu smanjenja amplitude induciranog naboja Q, povećanjem apsorbirane doze Dd, korištena je funkcija oštećenja zračenjem. Izračunate vrijednosti faktora ekvivalentnog oštećenja Ked dobivene detekcijom pojedinih iona pomoću fotodioda ozračenih različitim ionskim snopovima (pojedinačni slučajevi proba-oštećenje) kreću se u rasponu 4∙ 10-15 – 7.2∙ 10-14 g/MeV. Iako NIEL hipoteza prilično dobro objašnjava detekciju protona i alfa-čestica, izmjerene razlike između pojedinačnih vrijednosti Ked proizlaze iz različitosti dubinskih raspodjela primarnih defekata (vakancija i intersticijskih atoma) koje proizvode ioni-projektili i/ili efikasnosti stvaranja stabilnih električkih defekata iz proizvedenih primarnih defekata. Rezultati mjerenja pokazuju da teži ioni (kisik i klor) proizvode više električki aktivnih defekata od lakih iona za jednake vrijednosti apsorbiranih doza. Izmjerene CCE vrijednosti koje odgovaraju detekciji različitih iona bitno ovise o dubinskoj raspodjeli kočenja ionizacijom (engl. Linear Energy Transfer - LET) čestice koja se detektira. Detekcija težih iona kratkog dosega u materijalu (čiji LET doprinos je najveći u blizini površine ozračene fotodiode) je vrlo osjetljiva na lokalizirano oštećenje koje proizvode ioni slične brzine (energije po jedinici mase) na dubini koja odgovara dosegu iona u unutrašnjosti poluvodiča. IBIC model koji se bazira na Gunnovom teoremu razvijen za simulaciju mehanizma sakupljanja naboja u ozračenim fotodiodama potvrđuje IBIC rezultate.

Metoda mjerenja induciranog naboja kojeg proizvode pojedinačni ioni (IBIC)kori-je za proučavanje efikasnosti sakupljanja naboja (CCE) prilikom detekcije nabi-čestica pomoću Si PIN fotodioda ozračenih fokusiranim snopovima H, He, Li, O i Cl iona. Energija (0.4 MeV/u) iona je takva da je doseg unutar područja osiro- mašenja fotodiode. Integrirani tok iona kreće su u rasponu 1E8 – 1E12 cm-2, a apsorbirana doza Dd za oštećenje pomakom u Si je u rasponu 1E10 – 1E13 MeV/g. Ozračavanjem nastale promjene CCE proučavane su u skladu s NIEL teorijom [1] koja previđa smanjenje induciranog naboja linearno s Dd. Iako NIEL hipoteza prilično dobro objašnjava detekciju H i He iona, izračunate različite vrije- dnosti faktora ekvivalentnog oštećenja K[2] koje su po prvi put zabilježene, proizlaze iz različitosti dubinskih raspodjela primarnih defekata (vakancija i intersticija) koje proizvode ioni-projektili i/ili efikasnosti stvaranja stabilnih defekata iz primarnih defekata. Teži ioni (O i Cl) proizvode više električki aktivnih defekata od lakih iona (H, He) za jednake Dd. Izmjerene CCE vrijednosti koje odgovaraju detekciji različitih iona bitno ovise o dubinskoj raspodjeli kočenja ionizacijom (LET) čestice koja se detektira. Detekcija težih iona kratkog dosega u tvari (čiji LET doprinos je najveći u blizu površine) je vrlo osjetljiva na lokalizirano oštećenje koje proizvode ioni na dubini koja odgovara njihovom dosegu u unutrašnjosti poluvodiča.

A high purity single crystal diamond produced by chemical vapor deposition (CVD) process recently became available as radiation detector device. Due to the excellent crystal quality and uniformity, these detectors show good energy resoluton and superior timing properties for charge particle detection. The ion beam induced charge (IBIC) is a very suitable ion microprobe technique for testing the charge collection properties of radiation detectors. With submicron spatial resolution of the ion microbeam, detector response can be studied at the microscopic level. In this work we report application of IBIC technique in characterization of commercial scCVD diamond detectors (1 mm2 area, 500 μ m thickness). Spatial distribution of charge collection efficiency (CCE) in diamond has been studied for different ions (protons, lithium and oxygen) and energies (1-10 MeV). Changes in energy resolution and polarization deterioration have also been studied in different working conditions and as a function of the ion energy, range and fluence. Preliminary results of radiation hardness measurements are also presented.

Development of techniques that use focused ion beams of MeV energy range for creation of new structures in materials by modifying their properties has been initiated in order to expand application possibilities of ion accelerators at the Ruđer Bošković Institute. In particular we have focused on heavy ions that create significantly larger radiation damage in materials when compared to protons and He ions. Structuring of radiation damage using the ion microbeam in crystalline materials has been developed and tested on silicon and diamond. Application possibilities of created structures came from the fact that radiation damage can decrease charge collection properties in silicon which may be of interest in production of position sensitive sensors. This approach has been demonstrated by creating position dependent response of silicon pin diodes. In the case of diamond, excessive radiation damage can increase conductivity which may be of interest for production of diamond based devices. Buried conductive lines have been produced in single crystal diamond. Additional application that use ion tracks created in different materials by heavy ion beams from 6.0 MV Tandem accelerator has also been developed. Application was first tested on polymers and subsequently on other materials of technological interest (such as SrTiO3). Cl and I ion beams of energies above 18 MeV have been used in this application. Implantation of lower energy ions such as carbon between 800 and 2000 keV has been performed also, using both broad and micro beam in order to form nanodiamonds in SiO2.

Metal casting is the most efficient way of shaping metals both for industrial purposes, as well as in art modeling. However, when casting an art model in metal, focus is on shape and form, and quality of a cast is often neglected. Therefore, artistic casts may vary in composition and structure, and often exhibit poor homogeneity. Inhomogeneity in composition decreases mechanical properties of a cast alloy, and also has a negative affect on corrosion resistance of alloy due to formation of anodic and cathodic places. These can lead to very dangerous local (galvanic) corrosion. Modern bronzes, cast in typical art foundries today, often show a high degree of inhomogeneity and various compositions due to many different casting methods in use and because of often very unrefined temperature control systems in processes of melting and solidification. In this work, we have studied several specimens of cast statuary bronzes and compared the results with the results obtained from the industrial standard bronze cast. In order to examine distribution of Sn as a major alloying element and Zn, Pb and Fe as trace elements larger area line scans were performed using PIXE (proton induced X-ray emission). Furthermore, the PIXE elemental maps allowed calculation of the homogeneity factor. The areas which have showed large scale inhomogeneities were subsequently examined by the means of PLP (potentiodynamic linear polarization) measurements, which were able to confirmed higher potential appearance of galvanic corrosion for those regions.

Outdoor bronze statues are usually exposed to aggressive environmental conditions thus covered with patina layers containing various constituents. Influence of sulfates is indicated as most important for creating patina layers under urban conditions. Majority of corrosion products in patina were identified as copper products but several studies have indicated the presence of tin compounds within naturally formed patinas on bronzes in atmospheric environments. In the present work, contribution of these tin-containing compounds to the protectiveness of a patina layer on statuary bronze (CuSn6) have been investigated. Artificial patina layers have been formed on bronze samples in 15mM Na2SO4 solution by immersion. The Cu/Sn ratio in patina layer was monitored versus immersion time using PIXE (proton induced X-ray emission) and the correlationbetween immersion time and Cu/Sn ratio was determined. The protective properties of patina layer have been determined by the method of electrochemical impedance spectroscopy. To avoid the contribution of increasing thickness of patina layer to corrosion resistance due to increased immersion time, the referent set of pure copper samples was immersed in the same solution as CuSn6 samples and measured at same time. These measurements helped establish correlation between protective properties of patina layer and Cu/Sn ratio in patina layer, and gain better understanding of bronze corrosion in neutral aqueous solutions.

There is a wide range of materials which are suitable for the nanostructuring using medium energy (≤1MeV/u) heavy ion beams. Only a few existing ion microprobes, including the one at the Ruđer Bošković Institute can focus medium energy heavy ion beams with a spatial resolution below 1 micrometer. Since the use of single ion positioning possibility can offer additional perspectives of patterning materials using ion tracks, we have tested several ion hit detection procedures. Heavy ions have been produced in 6 MV Tandem Van de Graaff accelerator of the Ruđer Bošković Institute. Low demagnification focusing was performed using a doublet from the first two quadropoles of the Oxford triplet configuration. Higher demagnification focusing system using a quintuplet configuration is now in testing stage. Both systems can focus low currents (fA) of heavy ion beams to submicron spotsizes with maximum ion ME/q2 of 25. In the view of these capabilities, we have constructed an ion hit detection system based on secondary electron and/or photon emission. Compared to systems based on detection of transmitted ions (STIM), systems that use light or electrons do not require thin samples that are transparent to the ion beam because secondaries are detected from the surface exposed to the beam. In this work, design and performance measurements of developed single ion hit detection system are presented.

The aim of this work was the investigation of pigments from five wooden polychrome altars from parochial churches in northern Croatia. All altars stem from the famous sculptor's workshop of Frantz Straub, which was active in the 1760s. Three of these altars from the parochial church of the Blessed Virgin Mary in Kloštar Ivanić have been recently restored in the Croatian Conservation Institute. The two other studied altars were the main altar from the parochial church in Pakrac and the altar from Velika Ludina.

Laboratory for ion beam interactions of the Ruđer Bošković Institute has been active in analytical applications for studies of cultural heritage objects for already more than 20 years, Majority of research has been performed using X-ray spectrometry techniques and in particular PIXE (Particle induced x-ray emission), with either broad proton beam or microbeam focused in a nuclear microprobe facility. Besides the non-destructive character of X-ray analysis, the versatility of PIXE has been proven in the multielemental analysis of paintings, alloys, ceramics and stone. Examples of recent applications presented here are: characterization of the metal threads from the 17th century church textile, analysis of inorganic pigments in the paintings by the Master Hans Georg Geiger and investigations of the provenance and elemental distribution in the glaze of the Chinese ceramics Tang Sancai. Furthermore, we present construction of the new external beam line PIXE set-up, which will allow investigations of objects in air, regardless of their size or shape, making this method even more universal. To enable extracting the proton beam out of the vacuum ambience special considerations have to be taken into account.

The installation of a new 1.0 MV Tandetron accelerator and a recent upgrade of the 6.0 MV Tandem Van de Graaff accelerator increased the application possibilities of the Zagreb ion microbeam system. Several ion sources enable now the selection of a wide variety of ions. Most of them can be focused by the existing microprobe system. Sample positioning tools and new scanner control options are implemented in the new generation of SPECTOR data acquisition system. Details of the upgrades are presented.

Low current irradiation is an important application of ion microprobe in the field of materials modification. As different ion species interact in a different way with the irradiated material, depending also on their energy, it does not exist a unique technique for the reliable ion fluence measurement. In single ion applications such as formation of ion tracks using swift heavy ions, detection of secondary electrons or photons that are emitted from the sample surface or scintillating surface layer can be used for reliable ion hit detection. In some applications transmitted ions (STIM), or charge signals (IBIC) can be utilized as well. For low currents of light ions, direct current measurement may not be possible, or is not sufficiently reliable. In these cases x-rays can be used for fluence normalization as well. In this work we discuss advantages and limitations of all these techniques, on the basis of efficiency measurements we performed for single ion hit detection. Protons, He, C and Si ions in the energy range from several hundred keV for light ions up to tens of MeV for heavier ions were used. We also present two application examples, namely ion track formation in polymers and structuring of electronic defects in semiconductor devices where reliable ion fluence measurement or ion hit detection is of prime importance.

The aim of the presentation is to show results of the collaboration between the Croatian Conservation Institute (CCI) and the Laboratory for Ion Beam Interactions of the Rudjer Boskovic Institute (RBI), based on the applications of the nuclear microprobe facility to the analysis of cultural heritage objects. The collaboration is based on characterization of inorganic pigments, alloys and other materials in paintings, statues and ancient buildings that are currently under conservation process performed by CCI.