Stacked Foil Research Articles

The multi-scattering model for calculations of positron spatial distribution in the multilayer stacks, useful for conventional positron measurements

The spatial distribution of positrons emitted from radioactive isotopes into stacks or layered samples is a subject of the presented report. It was found that Monte Carlo (MC) simulations using GEANT4 code are not able to describe correctly the experimental data of the positron fractions in stacks. The mathematical model was proposed for calculations of the implantation profile or positron fractions in separated layers or foils being components of a stack. The model takes into account only two processes, i.e., the positron absorption and backscattering at interfaces. The mathematical formulas were applied in the computer program called LYS-1 (layers profile analysis). The theoretical predictions of the model were in the good agreement with the results of the MC simulations for the semi infinite sample. The experimental verifications of the model were performed on the symmetrical and non-symmetrical stacks of different foils. The good agreement between the experimental and calculated fractions of positrons in components of a stack was achieved. Also the experimental implantation profile obtained using the depth scanning of positron implantation technique is very well described by the theoretical profile obtained within the proposed model. The LYS-1 program allows us also to calculate the fraction of positrons which annihilate in the source, which can be useful in the positron spectroscopy.

Surface Wear Studies in Some Materials Using α-induced Reactions

The radio-activity produced during the irradiation of 63,65 Cu, 59 Co, 93 Nb and 121,123 Sb targets with α-particles have been measured using activation technique. The yields of radioactive isotopic products 66,67,68 Ga, 61 Cu, 96g,m Tc and 123,124,126 I have been determined in the energy range ≈ 10-40 MeV using stacked foil technique. Radioactive counting of samples was performed with a high-resolution gamma-spectrometer. As light ion beams produce an extremely narrow layer of activities in the surface of a material, these reactions may be useful for thin layer activation study. 1. IntR oDUctIon The thin layer activation (TLA) technique has become a widely used sensitive tool to study the surface wear of micron order in metallic surfaces in various engineering components. It is known that reliability of industrial equipments, transport systems, power plants both nuclear as well as conventional etc., is considerable influenced by the process of wear, corrosion and erosion. As such, the development of effective methods for the detection, measurements and monitoring of these processes are quite important. This is an important aspects in the sense that dangerous accidents during operation of industrial installation, and production losses may be avoided due to machine break-down. The charged particle activation for measurement and monitoring of corrosion and wear is important particularly when the parts of the surface are not really accessible. In TLA method, radioactivities in thin layers of the metallic foils are induced by bombarding them with light charged particles like protons, deuterons and α-particles. The incident charged particles may produce radio-active residues in the target material through nuclear reactions. The yield of the radio-active residues as a function of the depth gives the profile of surface wear. The yield of a particular radio-isotope may be determined from the measured cross-sections for that reaction responsible for the formation of the residue. The cross-sections for the production of

Activation cross-sections of longer-lived products of proton induced nuclear reactions on dysprosium up to 36 MeV

Activation cross-sections of longer-lived products of proton induced nuclear reactions on dysprosium were measured up to 36MeV by using stacked foil irradiation technique and γ-spectrometry. We report for the first time experimental cross-sections for the formation of the radionuclides 162mHo, 161Ho, 159Ho, 159Dy, 157Dy, 155Dy, 161Tb, 160Tb, 156Tb and 155Tb. The experimental data were compared with the results of cross-section calculations of the ALICE and EMPIRE nuclear model codes and of the TALYS nuclear reaction model code as listed in the on-line libraries TENDL 2011 and TENDL 2012.

Deuteron induced reactions on Ho and La: Experimental excitation functions and comparison with code results

Activation products of rare earth elements are gaining importance in medical and technical applications. In stacked foil irradiations, followed by high resolution gamma spectroscopy, the cross-sections for production of 161,165Er, 166gHo on 165Ho and 135,137m,137g,139Ce, 140La, 133m,133g,cumBa and 136Cs on natLa targets were measured up to 50MeV. Reduced uncertainty is obtained by simultaneous remeasurement of the 27Al(d,x)24,22Na monitor reactions over the whole energy range. A comparison with experimental literature values and results from updated theoretical codes (ALICE-D, EMPIRE-D and the TENDL2012 online library) is discussed.

Excitation functions for the formation of longer lived isotopes by deuteron irradiation of Europium

Excitation functions for nuclear reactions induced on natural europium targets by energetic deuterons were studied up to 50MeV. A standard stacked foil technique was used for irradiation and high resolution gamma spectrometry was applied for activity assessment. Direct or cumulative cross sections for reaction products with half-life longer than 2h were determined. Reactions leading to the formation of the radionuclides 147,149,151,153Gd, 147,148,149,150m,150g,152m,152g,154gEu, 153Sm and 150Pm were studied. In most cases no earlier data were available in the literature. The new experimental results were compared with values tabulated in the on-line TENDL2011 library.

Effect of the metallic matrix on the sliding wear of plasma assisted debinded and sintered MIM self-lubricating steel

A new processing route to obtain a homogeneous dispersion of discrete particles of solid lubricant in the volume of sintered steels produced by metal injection moulding (MIM) was recently presented. In this technique, both thermal debinding and sintering are carried out in a single thermal cycle using a Plasma Assisted Debinding and Sintering (PADS) process. The homogeneous dispersion of discrete particles of solid lubricant was achieved by in situ formation of graphite nodules due to the dissociation of a precursor (SiC particles) mixed with the metallic matrix powders during the feedstock preparation. Nodules of graphite (size≤20μm) presenting a nanostructured stacking of graphite foils with thickness of a few nanometres were obtained. In this work, the effect of the metallic matrix composition on the sliding wear behaviour (dry reciprocating sliding tests; normal load 7N; frequency 2Hz; stroke 10mm; 5mm diameter 52100 steel ball) of 3% SiC plasma assisted debinded and sintered (T=1150°C, 1h) self-lubricating steel is presented and discussed. Three different matrix compositions (Fe+0.6% C; Fe+0.6% C+4.0% Ni; Fe+0.6% C+4.0% Ni+1.0% Mo) were analysed. The mechanical properties were greatly increased by the addition of Nickel and further improved (2x) by the presence of Molybdenum. Increasing the hardness of the composites induced a strong decrease of the average friction coefficient, which reached values as low as 0.04. The counter body wear rate was greatly affected by the matrix composition (4x). Similar behaviour was observed for the wear rate of the specimen. The results were discussed in terms of wear mechanisms, which were characterised using SEM and micro Raman spectroscopy.

New measurements and evaluation of database for deuteron induced reaction on Ni up to 50 MeV

Excitation functions for nuclear reactions induced by deuterons up to 50MeV on natural nickel targets were studied in five experiments using a standard stacked foil technique and non destructive high resolution gamma spectrometry. Reaction products with half life of more than 2h were assessed. The elemental activation cross sections were determined for reactions resulting in the radionuclides 61Cu, 56,57Ni, 55,56,57,58,60Co, 52,54,56Mn and 51Cr. The new experimental results were compared with earlier evaluated data and with values tabulated in the online TENDL2011 library.

Experimental excitation functions of deuteron induced reactions on natural thallium up to 50 MeV

Excitation functions of deuteron induced reactions on natural thallium leading to the formation of 204m,203m2+m1+g,202m,201m+g,200Pb and 202,201m+g,200m+gTl isotopes were determined up to 50MeV.The cross sections were measured by an activation technique using stacked foil irradiation. The excitation functions of the investigated reactions are compared with data reported in literature and also with the theoretical results of TALYS nuclear reaction code. From the measured cross section data, the thick target yield for the medical interesting 203Pb isotope is calculated.

STUDY OF ISOMERIC CROSS-SECTION RATIO AND PRE-EQUILIBRIUM FRACTION IN PROTON AND ALPHA PARTICLE INDUCED NUCLEAR REACTIONS ON 197Au

Excitation functions for the reactions 197 Au(p,n) 197g Hg and 197 Au(p,n) 197m Hg have been measured over the energy ranges from threshold up to 20 MeV using stacked foil activation technique. The isomeric cross-section ratio σm/(σm+σg) for the formation of 197g, m Hg was determined. The excitation functions and isomeric cross-section ratios were calculated for the reactions 197 Au(p,n) 197g,m Hg , 197 Au(p,2n) 196 Hg , 197 Au(p,3n) 195g,m Hg , 197 Au(p,4n) 194 Hg , 197 Au(p,5n) 193g,m Hg , 197 Au (α, n )200 Tl , 197 Au (α, 2n )199 Tl , 197 Au (α, 3n )198g,m Tl , 197 Au (α, 4n )197 Tl and 197 Au (α, 5n )196g,m Tl from reaction threshold up to 40 MeV for proton induced reactions and 80 MeV for alpha induced reactions. The results were compared with the theoretical cross-sections calculated by means of the code EMPIRE-II and with the available literature data, which makes use of the Hauser Feshbach model for the compound nuclear calculations and the exciton model for the pre-equilibrium emission part. The isomeric cross-section ratio is found to depend strongly on the relative spins of the isomeric and ground state, energy difference between the levels, presence of intermediate states and some dependence on decay modes and on the onset of pre-equilibrium emission.

Investigation of activation cross-sections of proton induced nuclear reactions on natMo up to 40 MeV: New data and evaluation

Cross-sections of proton induced nuclear reactions on natural molybdenum have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions of 93mTc, 93gTc(m+), 94mTc, 94gTc, 95mTc, 95gTc, 96gTc(m+), 99mTc, 90Mo(cum), 93mMo, 99Mo(cum), 90Nb(cum), 92mNb, 95mNb, 95gNb, 96Nb and 88Zr(cum), 89Zr(cum) were measured up to 40MeV proton energy by a using stacked foil technique and activation method. The main goals of this work were to study the production possibility of the medically important 99mTc and its 99Mo parent nucleus, to get experimental data for accelerator technology, for monitoring of proton beam, for thin layer activation technique and for testing nuclear reaction theories. The experimental data were compared with critically analysed published data and with the results of model calculations, obtained by using the ALICE-IPPE, EMPIRE-II and TALYS codes.

NUCLEAR ISOMERS90m, gZr,89m, gZr,89m, gYAND85m, gSrFORMED BY BOMBARDMENT OF89YWITH PROTONS OF ENERGIES FROM 4 TO 40MeV

Excitation functions for the reactions89Y (p, n)89gZr and89Y (p, n)89mZr have been measured over the energy ranges from threshold to 15 MeV using stacked foil activation technique. The isomeric cross-section ratio σm/(σm+σg) for the formation of89m, gZr was determined. The excitation functions and isomeric cross-section ratios were calculated for the reactions89Y (p, γ)90m, gZr ,89Y (p, n)89m, gZr ,89Y (p, p)89m, gY and89Y (p, αn)85m, gSr also for energy range 4–40 MeV . The PE emission fraction is found to depend strongly on the energy of the incident particle. The isomeric cross-section ratio is found to depend strongly on the relative spins of the isomeric and ground state and some dependence on energy difference between the levels.

Chemical changes in PMMA as a function of depth due to proton beam irradiation

In this work we determined depth profiles of the chemical change in PMMA irradiated with 2 MeV protons by infrared spectroscopic and micro-Raman measurements. The measurements were carried out on 10 μm thin stacked foil samples using an infrared spectrometer in universal attenuated total reflectance (UATR) and transmission modes; while the thick samples were analyzed with a confocal micro-Raman spectrometer. The depth profiles of the changes formed due to the various delivered fluences were compared to each other. The measurements show the strong dependence of the degree of modification on the energy transfer from the decelerating protons. Depth profiles reveal that at the fluences applied in this work the entire irradiated volume suffered some chemical modifications. In case of low-fluence samples the zone of maximal modification is restricted only to the Bragg peak, but with increasing fluences the region of maximal modification extends towards the sample surface.

Effect of precursor content and sintering temperature on the scuffing resistance of sintered self lubricating steel

Abstract The production of self lubrication composites containing second phase particles incorporated into the volume of the material appears to be a promising solution. A new processing route to obtaining a homogeneous dispersion of discrete solid lubricant particles in the volume of sintered steels produced by metal injection molding (MIM) was recently presented. This new route was achieved by in situ formation of graphite nodules due to the dissociation of precursor (SiC particles) mixed with the metallic matrix powders during the feedstock preparation. Nodules of graphite (size ≤20 μm) presenting a nanostructured stacking of graphite foils a few nanometers thick were obtained. The thermal debinding, as well as the sintering, was performed in a single thermal cycle using a Plasma Assisted Debinding and Sintering (PADS) process. In this work, we present and discuss the effect of precursor content and sintering temperature on the scuffing resistance of plasma assisted debinded and sintered self lubricating steel produced by metal injection mould technique. Three different temperatures (1100, 1150 and 1200 °C) and six different SiC contents (0–5%) were analyzed. Increasing the precursor content and, as a consequence, the number of graphite nodules, produced a clear increase in scuffing resistance for all analyzed sintering temperatures. Friction coefficient was little affected by the sintering temperature. However, the scuffing resistance was greatly increased (5×) for the lower sintering temperature (1100 °C).

High-intensity and high-brightness source of moderated positrons using a brilliant γ beam

Presently large efforts are conducted towards the development of highly brilliant gamma beams via Compton back scattering of photons from a high-brilliance electron beam, either on the basis of a normal-conducting electron linac or a (superconducting) Energy Recovery Linac (ERL). Particularly ERL's provide an extremely brilliant electron beam, thus enabling to generate highest-quality gamma beams. A 2.5 MeV gamma beam with an envisaged intensity of 10^15 s^-1, as ultimately envisaged for an ERL-based gamma-beam facility, narrow band width (10^-3), and extremely low emittance (10^-4 mm^2 mrad^2) offers the possibility to produce a high-intensity bright polarized positron beam. Pair production in a face-on irradiated W converter foil (200 micron thick, 10 mm long) would lead to the emission of 2 x 10^13 (fast) positrons per second, which is four orders of magnitude higher compared to strong radioactive ^22Na sources conventionally used in the laboratory.Using a stack of converter foils and subsequent positron moderation, a high-intensity low-energy beam of moderated positrons can be produced. Two different source setups are presented: a high-brightness positron beam with a diameter as low as 0.2 mm, and a high-intensity beam of 3 x 10^11 moderated positrons per second. Hence, profiting from an improved moderation efficiency, the envisaged positron intensity would exceed that of present high-intensity positron sources by a factor of 100.

Activation cross-sections of deuteron induced nuclear reactions on gold up to 40 MeV

Cross-sections of deuteron induced nuclear reactions on gold were measured up to 40 MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectroscopy. Experimental cross-sections and derived integral yields are reported for the 197Au(d,xn) 197m,197g,195m,195gHg and 197Au(d,x) 198g,196m,196g,195,194Au nuclear reactions. The experimental data are analyzed and compared to literature and predictions of the ALICE-IPPE, EMPIRE and TALYS theoretical model codes. The application of the new cross-sections for accelerator technology, medical radioisotope production, thin layer activation and dose calculation is discussed.

Production of medical radioisotopes with high specific activity in photonuclear reactions with γ-beams of high intensity and large brilliance

We study the production of radioisotopes for nuclear medicine in (γ,xn+yp) photonuclear reactions or (γ,γ′) photoexcitation reactions with high-flux [(1013–1015)γ/s], small diameter ∼(100 μm)2 and small bandwidth (ΔE/E≈10−3–10−4) γ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion,xn+yp) reactions with (ion = p,d,α) from particle accelerators like cyclotrons and (n,γ) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow γ-beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). However, for ions with a strong atomic stopping only a fraction of less than 10−2 leads to nuclear reactions resulting in a target heating, which is at least 105 times larger per produced radioactive ion and often limits the achievable activity. In photonuclear reactions the well defined initial excitation energy of the compound nucleus leads to a small number of reaction channels and enables new combinations of target isotope and final radioisotope. The narrow bandwidth γ excitation may make use of the fine structure of the Pygmy Dipole Resonance (PDR) or fluctuations in γ-width leading to increased cross sections. Within a rather short period compared to the isotopic half-life, a target area of the order of (100 μm)2 can be highly transmuted, resulting in a very high specific activity. (γ,γ′) isomer production via specially selected γ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground state occurs. We discuss in detail many specific radioisotopes for diagnostics and therapy applications. Photonuclear reactions with γ-beams allow to produce certain radioisotopes, e.g. 47Sc, 44Ti, 67Cu, 103Pd, 117m Sn, 169Er, 195m Pt or 225Ac, with higher specific activity and/or more economically than with classical methods. This will open the door for completely new clinical applications of radioisotopes. For example 195m Pt could be used to verify the patient’s response to chemotherapy with platinum compounds before a complete treatment is performed. Also innovative isotopes like 47Sc, 67Cu and 225Ac could be produced for the first time in sufficient quantities for large-scale application in targeted radionuclide therapy.

Preparation and Performance of a Catalyst-Coated Stacked Foil Microreactor for the Methanol Synthesis

A stacked foil microreactor (SFMR) was developed and used to study methanol synthesis under high pressure. Two catalyst foil coatings were applied: Pd/CeO2 by sol−gel coating and impregnation and C...

Study of activation cross sections of proton induced reactions on barium: Production of 131Ba→131Cs

In the frame of a systematic study of charged particle production routes of the therapeutic radioisotope (131)Cs, excitation functions of the (nat)Ba(p,x)(135,132mg)La, (ind135m,cum133m,cum133mg,cum131mg)Ba and (136mg,134mg,132,cum129)Cs reactions were measured in the 30-70 MeV energy range using stacked foil irradiation technique, activation method and gamma spectroscopy. Comparisons with new results of the ALICE-IPPE and EMPIRE-II codes and with existing data obtained with TALYS code are shown. From the measured cross section data integral yields were calculated and compared with experimental integral yield data reported in the literature. Potential use of proton induced reactions on Ba for production of (131)Cs is discussed.

Experimental deuteron cross section measurements using single natural titanium foils from 3 to 9MeV with special reference to the production of 47V and 51Ti

Abstract Although the conventional stacked foil technique is the common method for evaluating experimental cross sections of deuteron induced reactions on titanium, this work employed a single foil irradiation strategy. This strategy was selected for the purpose of improving the counting statistics for the reactions with low activation probabilities as it allowed for activity assay times comparable to the half-life of the product of interest. Given a single detector, similar activity assay times were not possible for the stacked foil technique as all remaining foils would have otherwise decayed significantly while the first foil was counting. To the best of our knowledge, this work reports the first comprehensive study of the elemental cross sections for production of 47 V ( t ½ = 32.6 m) and 51 Ti ( t ½ = 5.76 m) for 3–9 MeV deuterons on natural titanium foil. Elemental cross sections for the production of 44g,44m,46,47,48 Sc, and 48 V were also evaluated, with good agreement to previous literature generally observed.

Production of the therapeutic radioisotope 114mIn through the 116Cd(p,3n) 114mIn reaction

Excitation curves for reactions induced by proton beams up to 36 MeV on highly enriched 116Cd targets were assessed. The standard stacked foil method, with monitoring of beam parameters over the whole energy region, and high resolution gamma spectrometry were used. We report cross sections for reactions leading to 113m ,114m,115m,116m1In and 115Cd. A comparison with some earlier experimental data and with results of theoretical model codes ALICE-IPPE and EMPIRE are presented. Our previous estimation of use of the 116Cd(p,3n) reaction for production of 114mIn is confirmed.