MeV Endpoint Energy Research Articles

Measurements of neutron and photon induced cross sections for the production of medical isotopes of strontium

The cross sections of the 88Sr(n,2n)87Srm, 88Sr(n,p)88Rb, 88Sr(n,α)85Kr, 86Sr(n,2n)85Srm, 86Sr(n,2n)85Srg and 84Sr(n,2n)83Sr nuclear reactions at 14.77 ± 0.17 MeV neutron energy and the average cross sections of the 88Sr(γ,n)87Srm and 86Sr(γ,n)85Srm nuclear reactions at bremsstrahlung of 15 MeV endpoint energy were measured with the activation method and offline gamma-ray spectroscopy. The measured cross sections were reported with a detailed covariance analysis for uncertainty and correlation coefficients. The experimental results were compared with the previously reported experimental data from the EXFOR database and the evaluated data from the TENDL-2019 library. Statistical model calculations were performed with the latest TALYS-1.95 code with optimised input parameters to better reproduce reported experimental data. The measured cross sections were found to be in good agreement with the literature and theoretical calculations. These results highlight the alternate production routes for the medical radioisotopes of 87Srm and 85Srg.

Comparative survey of evaluated nuclear data libraries for fusion-relevant neutron activation spectrometry

The neutron flux-spectrum in a fusion device is frequently determined with activation foils and adjustment of a guess-spectrum in unfolding codes. Spectral-adjustment being a rather complex and uncertain procedure, we are carefully streamlining and evaluating it for upcoming experiments. Input nuclear cross-section data holds a vital position in this. This paper presents a survey of common dosimetry reactions and available data files relevant for fusion applications. While the IRDFF v1.05 library is the recommended source, many reactions of our interest are found missing in this. We investigated other standard sources: ENDF/B-VIII.0, EAF-2010, TENDL-2017, JENDL-4.0 etc. And, we analysed two experiments to ascertain the sensitivity of the spectral adjustment to the choice of nuclear data. One was performed with D-D (approx. 2.5 MeV peak) neutrons at the Joint European Torus (JET) machine and another with a white neutron field (approx. 33 MeV endpoint energy) at Nuclear Physics Institute (NPI) of Řež. Choice of cross-section source has affected the integral fluxes (<5%), reaction rates (<10%), total fluxes in some sensitive energy-regions (>20%) and individual group fluxes (<30%). Based on this experience, essential qualitative conclusions are made to improve the fusion activation-spectrometry.

Determination of the Sr/Ca ratio of tooth samples by photoactivation analysis in Southern Turkey

Abstract A nuclear analytical technique, namely instrumental photon activation analysis (IPAA), was used to determine Sr and Ca concentrations in human teeth. This work was conducted using the first accelerator facility, an off-shelf clinical linear accelerator (cLINAC), in Turkey. The tooth samples supplied by the Akdeniz University Faculty of Dentistry were analyzed for determination of the Sr/Ca element ratio. The results were obtained to demonstrate the impact of socioeconomic changes on dietary habits. A calibration material (CM; a mixture of calcium and strontium oxides) was required for quantification of the analytical results. The tooth samples, together with the CM, were exposed to 18 MeV end-point energy bremsstrahlung photons from the cLINAC. Thereafter, the γ-ray spectra of the samples and the CM were obtained using high resolution γ spectroscopy. Variations in the Sr/Ca ratio in the teeth of patients fed with beef and fizzy beverages were investigated in this study.

Photonuclear Reaction Results of Energy Levels of Iodine Isotopes

In this study, photonuclear reaction of 127 I has been studied by using bremsstrahlung photons of 18 MeV endpoint energy via a clinical linear accelerator. As a result of this, 127 I(γ,n) 126 I and 127 I(n,γ) 128 I reactions have been observed. The gamma photons emitted by the excited nuclei have been counted with an HPGe detector. The experimental data have been analyzed by using gf3 and ROOT spectrum programs and all the energy transitions have been calculated. The results have been compared with the literature values.

Feasibility of in situ beta ray measurements in underwater environment

We describe an attempt at the development of an in situ detector for beta ray measurements in underwater environment. The prototype of the in situ detector is based on a CaF2: Eu scintillator using crystal light guide and Si photomultiplier. Tests were conducted using various reference sources for evaluating the linearity and stability of the detector in underwater environment. The system is simple and stable for long-term monitoring, and consumes low power. We show here an effective detection distance of 7 mm and a 2.273 MeV end-point energy spectrum of 90Sr/90Y when using the system underwater. The results demonstrate the feasibility of in situ beta ray measurements in underwater environment and can be applied for designing an in situ detector for radioactivity measurement in underwater environment. The in situ detector can also have other applications such as installation on the marine monitoring platform and quantitative analysis of radionuclides.

Excitation of 11/2− isomeric state in 137Ce in (γ,n) reaction within 10–22MeV energy range

Isomeric yields ratios and energy differential cross-section of metastable state excitation in the [Formula: see text] reaction has been studied in the 10–22[Formula: see text]MeV end-point energy range of bremsstrahlung beams. Experimental data are compared with Hauser–Feshbach calculations performed with TALYS-1.6 statistical model code.

Experimental determination of the energy levels of 159Gd via photonuclear reaction

In this study, the energy levels of 159 Gd are measured within the framework of the photonuclear reaction. For this aim, bremsstrahlung photons of 18 MeV endpoint energy produced by a clinical linear accelerator are used. The gamma photons emitted from the unstable 159 Gd nucleus are counted by using a high purity Germanium detector. The energy levels are determined with gf3 and ROOT spectrum analysis programs. Finally, all the results are compared with the literature results.

Photoexcitation of the high-spin J=8 isomer in 176Yb using 8.5 MeV end-point energy Bremsstrahlung

Excitation of the 1049.8keV isomeric state (t1/2=11.4s, spin difference between ground and isomeric states ΔJ=8) in 176Yb using Bremsstrahlung radiation is observed for the first time. In contrast to the photoexcitation of isomeric states in other nuclei with lower spin differences, where effective integrated cross-sections are of order tens to hundreds of barneV, an integrated cross-section of just 0.0484±0.066barneV is observed for 176Yb.

The results of the first photonuclear reaction performed in Turkey: the zinc example

We have investigated the decays of several zinc isotopes produced by photonuclear reactions, which were induced by bremsstrahlung photon beams from a clinical e-linac. A photon beam of 18 MeV endpoint energy was directed at a target consisting of primarily zinc isotopes in their natural abundances. Subsequently, the induced decays of unstable zinc isotopes were measured with an HPGe detector twice, once shortly after irradiation and once on the following day. Decays of Zn-63, Zn-65, Zn-69m, and Cu-67 were measured and fitted. In addition, the gamma energy levels of the daughters of these decays were measured with good accuracy. All of the measurements were consistent with established data within error bars.

SU-E-T-394: Effects of Various Encapsulation Materials to the Dose Fall-Off for Beta-Emitting Brachytherapy Seed

Purpose: A beta‐emitting glass seed without encapsulation has been proposed for the brachytherapy treatment of prostate cancer. Beta sources have several desirable properties. Beta sources have short range and are easily shielded, lowering extraneous dose to the medical staff as well as the patient. Even though there are several advantages of using beta‐emitting glass seeds, the dose fall‐off is considerable. This study aims at evaluating the effects of dose fall‐off and bremsstrahlung using encapsulation. Methods: MCNPX2.6 Monte Carlo transport code was used to calculate the quantitative dosimetric parameters of the seeds. The radioisotope used for seed was 142Pr. The 142Pr decays by beta emission with a 2.162 MeV endpoint energy is followed by emission of a 1.575 MeV gamma‐ray with 3.7% abundance. The gamma dose was not included in this research except the contributions of bremsstrahlung because the encapsulation does not attenuate the 1.5 MeV gamma much. Various encapsulation materials were investigated including silver,titanium, and tungsten. A simulation model of glass seed with encapsulation was developed within MCNPX2.6. Dosimetry data in water were calculated in radial distances from the glass seed from 0.1 cm to 1.0 cm by using the mesh tally feature in MCNPX2.6. Results: The relative dose of titanium and tungsten to water at 0.2 cm were 84.5 % and 21.9 % while the relative dose at 0.6 cm was 60.4% and 12.4% respectively. Considering the reduction of dose at the target point (0.6 cm), it was found that titanium is the most appropriate material. The contribution of bremsstrahlung was insignificant. Conclusions: The effects of source encapsulation on dose fall‐off were studied. The encapsulation has effectively made the dose profiles uniform. The bremsstrahlung effect was insignificant. From this study, the dosimetric parameters would be derived for clinical use.

Measurement of focal spot size in a 5.5 MeV linac

High energy X-ray beams allow to perform analysis on different materials and objects of relevant interest that cannot be investigated with conventional X-ray sources. A 5.5 MeV endpoint energy bremsstrahlung source has been characterized by evaluating the size of X-ray emitting area. In order to perform a proper characterization, an ‘ad hoc’ slit-camera has been designed and a specific technique has been adopted. Due to the characteristics of the beam, a highly attenuating slit with variable aperture has been designed using Monte Carlo simulations of the X-ray beam and set up. Since the slit camera is far from the ideal model (negligible X-ray transmission and very thin aperture), a whole set of image profiles of the slit at different width sizes have been acquired and analyzed. Imaging correction procedures and data fitting lead to satisfactory experimental results according to the theoretical model.

Fragment characteristics from fission of 238U and 234U induced by 6.5–9.0 MeV bremsstrahlung

Fission of 238U and 234U induced by bremsstrahlung of 6.5–9.0 MeV endpoint energy has been investigated at the superconducting Darmstadt electron linear accelerator S-DALINAC. Using a twin Frisch grid ionization chamber, fission-fragment energy and mass distributions have been determined by means of the double kinetic-energy technique. Results on the fission-fragment characteristics from U238(γ,f) are in agreement with results from the literature. In addition fission-fragment mass and energy distributions from U234(γ,f) are presented for the first time in this energy region. An analysis of fission modes within the Brosa model has been performed. The relative yield of the S1 mode was found to be (13±3)% in 234U and (35±2)% in 238U.

Is the 4.742 MeV state in 88Sr the 1− two-phonon state?

A nuclear resonance fluorescence experiment on 88Sr has been performed with bremsstrahlung of 6.7 MeV endpoint energy. The γ-ray linear polarisation has been measured with a EUROBALL CLUSTER detector used as a Compton polarimeter. The results indicate positive parity for the J= 1 state at 4.742 MeV in 88Sr, in contrast to the previous interpretation as a 1− two-phonon (2+1⊗ 3−1) state and in conflict with the predictions of the quasiparticle-phonon model. On the basis of such calculations the 1+ state at 3.486 MeV may be considered as the 1+1 one-phonon state and the very strong 1+1→ 0+1 deexcitation as proton spin-flip 2p1/2→ 2p3/2 transition.

Photofission of 27Al nucleus in the quasi-deuteron region of photonuclear absorption

Quasi-monochromatic photon beams of 108 MeV Compton-edge energy produced in the ROKK-1M facility at the storage ring VEPP-4M (BINP, Novosibirsk) and makrofol sheets as fission track detectors were used to measure the photofission yield of 27Al. The fission yield was found to be (160±55) µb. From this result and previously measured 27Al photofission yield at ~79 MeV end-point energy with the LADON apparatus, the trends of fission cross section and fissility have been obtained in the incident photon energy range ~40-110 MeV. The present results and data for other intermediate-mass nuclei obtained with the same methodology indicate an increase of fissility with decreasing Z2/A as predicted by the liquid drop model for fissioning systems lighter than ~Ag.

Production of long-lived isomers by 4 MeV endpoint energy bremsstrahlung

Production of long-lived isomers by 4 MeV endpoint energy bremsstrahlung

Production of long-lived isomers by 4 MeV endpoint energy bremsstrahlung

Long-lived isomers of87Sr,103Rh,111Cd,113,115In,117Sn,176Lu,189Os,193Ir and195Pt were produced by means of bremsstrahlung from a 4 MeV endpoint energy 25µA intensity electron beam. Isomeric activities were measured by gamma-spectrometry. Photoexcitation exhibits a steep rise as compared to lower energy excitations of prior experiments by high activity137Cs,60Co,142Pr and24Na sources. The large variety in the magnitude of the excitation cross section may mostly arise from largely differing isomer ratios governed by spin differences between isomeric and ground levels, and likely by differences in the multipole character of the upward transitions, too. Isomer excitation seems to exhibit loose correlations with the product of photoabsorption cross section and isomer ratio derived from (n,n′) reactions on the one hand, and with the product of valence proton and neutron numbers and isomer ratio on the other hand.

Electric and magnetic dipole excitations to bound states in 70,72,74,76Ge

The nuclei 70,72,74,76Ge were studied by nuclear resonance fluorescence (NRF) experiments. Partially linearly polarized and unpolarized bremsstrahlung of 9 to 14 MeV endpoint energy was used at the Giessen 65 MeV electron linear accelerator; unpolarized bremsstrahlung of 4 MeV endpoint energy was used at the Stuttgart Dynamitron. The scattered photons were detected by Ge γ-ray spectrometers with high energy resolution. Multipolarities were determined by measuring the angular correlations between the beam and the scattered γ rays at different scattering angles. Precise excitation energies and ground-state decay widths of numerous (> 120) previously unknown spin-1 states were extracted. For 65 ground-state transitions (20 M1 transitions, 45 E1 transitions) parities were assigned, in a model-independent way, by polarized bremsstrahlung. A detailed distribution of electric and magnetic dipole strength in the even Ge isotopes was established.

Integral cross section of the99Tc(γ,γ′)99mTc reaction at 4 MeV

99mTc production was studied with the aid of photoexcitation by a 4 MeV endpoint energy bremsstrahlung from the LINAC of the Institute of Isotopes, Budapest. The intensity of the γ-flux was monitored by disc-shaped natural indium plates, placed in front of and behind the small cylindrical aluminium holders containing TcO2 samples in a powder form. Isomeric activities were measured through the 140 keV γ-line by a Ge spectrometer. The integral cross section at 4 MeV was found to be 63.3±7.1 μbMeV, which can be considered reasonable compared to the corresponding value of 55.3 μbMeV established for the115In (γ,γ′)115mIn reaction. We also attempted the photoexcitation of99mTc by irradiation with γ-rays from a 1.5×1015 Bq60Co source, but no isomeric activity could be observed. This places the first activation level between 1.33 and 4 MeV.

Photoexcitation of low-lying dipole transitions in 236U.

Nuclear resonance fluorescence experiments have been performed on the deformed actinide nucleus $^{236}\mathrm{U}$. Bremsstrahlung of 3.9 MeV endpoint energy has been used as the photon source. The scattered photons were detected by three high resolution Ge-\ensuremath{\gamma}-spectrometers installed at scattering angles of 92\ifmmode^\circ\else\textdegree\fi{}, 128\ifmmode^\circ\else\textdegree\fi{}, and 150\ifmmode^\circ\else\textdegree\fi{}, respectively. Precise excitation energies, decay branching ratios, and ground state decay widths of numerous previously unknown spin 1 states in the excitation energy range 1.8--3.2 MeV have been extracted. The dipole strength has been found to be concentrated in the energy range 2.1--2.5 MeV. The systematics of the so-called scissors mode observed as a result of the previous (\ensuremath{\gamma},\ensuremath{\gamma}') and (e,e') experiments on $^{232}\mathrm{Th}$ and $^{238}\mathrm{U}$ and, in particular, their combined analysis suggests likewise to attribute these new dipole excitations in $^{236}\mathrm{U}$ to the orbital M1 scissors mode.

Dipole excitations in 48Ti studied by nuclear resonance fluorescence

Nuclear resonance fluorescence experiments have been performed on the nucleus 48Ti. Unpolarized bremsstrahlung of 4.1 and 11 MeV and partially linearly polarized bremsstrahlung of 12 and 14 MeV endpoint energy, respectively, served as the photon sources. The scattered photons were detected by high-resolution Ge γ-spectrometers. Precise excitation energies, decay branching ratios, and ground-state decay widths of numerous previously unknown spin-1 states have been extracted. Model-independent parity assignments could be achieved for the strongest transitions. The results are compared with data from previous (γ, γ') work, from recent (e, e') and (p, p') experiments, and with theoretical predictions.