End-point Energy Research Articles

Preparation of 99Mo from the 100Mo(γ, n) reaction and chemical separation of 99mTc

The radionuclide 99Mo has been prepared by 100Mo(γ, n) reaction using two types of natural molybdenum compound (molybdenum trioxide and zirconium molybdate gel) with the bremsstrahlung end-point energies of 10 and 15 MeV. After the equilibrium, 99mTc was separated as NaTcO4 from the irradiated samples using two different chemical procedures to examine the chemical yield. The separated Na[99mTc]TcO4 from the ZrMo gel has the 99Mo breakthrough of 99 % as well as chemical impurities of Al, Mo and Zr < 10 ppm. The estimation of 99Mo and 99mTc was done by using off-line γ-ray spectrometric technique. The chemical yield of the separated 99mTc from the dissolved molybdenum trioxide is 70.7–75.2 %, whereas in the undissolved zirconium molybdate gel, it is 19.1–43 %. The second method is preferable because it is user friendly in hospital radiopharmacy throughout the shelf-life.

Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing 19F

In the present study ⌀ 5′′× 3′′ and ⌀ 2′′× 2′′ EJ-313 liquid fluorocarbon as well as ⌀ 2′′ × 3′′ BaF2 scintillators were exposed to neutrons from a 252Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β− particles with maximum endpoint energy of 10.4 MeV from the n+19F reactions were studied. Response of a ⌀ 5′′ × 3′′ BC-408 plastic scintillator was also studied as a reference. The β− particles are the products of interaction of fast neutrons with 19F which is a component of the EJ-313 and BaF2 scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a 252Cf source showed that the relative neutron detection efficiency ratio, defined as ϵBaF2 / ϵEJ−313−5′′, is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF2, respectively. Moreover, the ⌀ 5′′ EJ-313 and side-on oriented BaF2 were also exposed to neutrons from the D+T neutron generator, and the relative efficiency ϵBaF2 / ϵEJ−313−5′′ was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF2 detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility.

Fission and spallation data evaluation using induced-activity method

The induced-activity investigations in off-line analysis performed in different experiments, concerning pre-actinide and actinide nuclei, are here presented and discussed. Generalized expressions for the determination of independent yields/cross sections of radioactive nuclei, formed in the targets, are derived and analysed. The fragment mass distribution from U-238, Th-232 and Ta-181 photofission at the bremsstrahlung end-point energies of 50 and 3500 MeV, and from Am-241, U-238 and Np-237 fission induced by 660-MeV protons, are scrutinized from the point of view of the multimodal fission approach. The results of these studies are hence compared with theoretical model calculations using the CRISP code. We subsequently discuss the complex particle-induced reaction, such as heavy-ions and deuterons, by using the thick-target thick-catcher technique and the two-step vector model framework as well. This is accomplished in order to present the investigation of the main processes (fission, spallation and (multi)fragmentation) in intermediate- and high-energy ranges of the incident particle. The set of experimental data, presented in this work, encompasses not merely the data as total production cross sections. Notwithstanding, it further covers other data, as individual yields/cross sections, charge, mass and spin distributions of the reaction fragments, as well as kinematic features. These sources of experimental data can serve as a consistent set of benchmarking data, still necessary for the study of heavy nuclei. Besides, it is also useful for technological applications, from astrophysics and environmental sciences to accelerator technology and accelerator-based nuclear waste transmutation and energy amplification as well.

Photonuclear reactions with zinc: A case for clinical linacs

The use of bremsstrahlung photons produced by a linac to induce photonuclear reactions is wide spread. However, using a clinical linac to produce the photons is a new concept. We aimed to induce photonuclear reactions on zinc isotopes and measure the subsequent transition energies and half-lives. For this purpose, a bremsstrahlung photon beam of 18MeV endpoint energy produced by the Philips SLI-25 linac has been used. The subsequent decay has been measured with a well-shielded single HPGe detector. The results obtained for transition energies are in good agreement with the literature data and in many cases surpass these in accuracy. For the half-lives, we are in agreement with the literature data, but do not achieve their precision. The obtained accuracy for the transition energies show what is achievable in an experiment such as ours. We demonstrate the usefulness and benefits of employing clinical linacs for nuclear physics experiments.

Multinucleon photonuclear reactions on 209Bi: Experiment and evaluation

Photon activation technique using bremsstrahlug with end-point energy 55.6 MeV is used to induce photonuclear reactions in a 209Bi target. Absolute yields and integrated cross sections of multiparticle reactions (γ, 2n-6n), (γ, 4n1p), and (γ, 5n1p) are obtained. The results are compared to predictions of statistical models using systematical and microscopic description of photoabsorption and to the result of evaluation of the partial photoneutron reaction cross sections. Based on a comparison with existing experimental photoneutron cross sections and model calculations, we make a conclusion that neutron multiplicity assignment in available photoneutron cross sections on 209Bi can be corrected and evaluated cross sections of (γ, 1n) and (γ, 2n) are obtained that are in an agreement with the obtained experimental results.

Comparison of fission signatures from β− delayed γ-ray and neutron emissions

The delayed γ-ray and neutron fission signals utilized in active inspection techniques were measured simultaneously in order to directly compare their detection sensitivities. Fissionable and non-fissionable targets were irradiated by a 15-Hz pulsed bremsstrahlung beam operating at endpoint energies from 7 to 22MeV. The fissionable mass detection limits for both these signals decreased approximately three orders of magnitude as the irradiation energy was increased with the delayed γ-ray limits 4.3–8.2 times smaller. The signals from the non-fissionable targets were consistent with the natural passive backgrounds for irradiation energies up to 16MeV. At higher bremsstrahlung energies, there was a target independent active background in the delayed γ-ray signal that accounted for 35% of the gross yield. In addition, these higher irradiation energies resulted in products from 9Be(γ,p)8Li and 18O(γ,p)17N reactions interfering with the delayed γ-ray and neutron fission signals, respectively.

Measurement of isomeric yield ratios of 197m,gPt and 190m2,g+m1Ir from the 198Pt(γ,n) and natPt(γ,xn1p) reactions induced by 55-, 60-, and 65-MeV bremsstrahlung

We have measured the isomeric yield ratios of 197m,gPt from the 198Pt(γ,n) reaction and 190m2,g+m1Ir from the natPt(γ,xn1p) reaction, induced with the bremsstrahlung end-point energies of 55-, 60-, and 65-MeV. The measurements were carried out by the activation method in combination with the direct γ-spectrometry. The experiments were performed at the 100MeV electron linac of the Pohang Accelerator Laboratory (PAL). The obtained results at 55-, 60- and 65-MeV for the 197m,gPt from the 198Pt(γ,n) reaction are 0.166±0.012, 0.174±0.011, and 0.175±0.011, whereas for the 190m2,g+m1Ir from the natPt(γ,xn1p) reaction are 0.072±0.006, 0.084±0.006 and 0.087±0.006, respectively. The present results are measured for the first time over the investigated energy range. The present data are compared with the similar literature data at lower energy to examine the role of excitation energy.

Measurement of isomeric yield ratios in the photo-production of 133m,g;137m,gCe from natCe using 55-, 60-, and 65-MeV bremsstrahlung

The isomeric yield ratios of 133m,gCe and 137m,gCe produced from the natCe(γ,xn) reactions were determined by using the activation and the off-line γ-ray spectrometric technique with the end-point bremsstrahlung energies of 55-, 60-, and 65-MeV at 100-MeV electron linac of the Pohang accelerator laboratory. The induced activities in the irradiated foils were measured by using an energy- and efficiency-calibrated HPGe detector coupled to a PC based multi-channel analyzer. The necessary corrections were made to improve the accuracy of the experimental results. The experimental results at bremsstrahlung energies of 55-, 60-, and 65-MeV were 0.324±0.089, 0.331±0.086, and 0.403±0.089 for the 133m,gCe, and 0.210±0.062, 0.221±0.061, and 0.262±0.061 for the 137m,gCe, respectively. The present results for natCe(γ,xn)133m,g;137m,gCe in this energy region were obtained for the first time which has no comparable literature data. The obtained isomeric yield ratios are compared with the calculated values based on the statistical model code TALYS 1.6.

Mass yield distributions and fission modes in photofission ofU238below 20 MeV

Photon activation technique is used to obtain photofission mass distributions of $^{238}\mathrm{U}$ after irradiation in a bremsstrahlung beam with end-point energies 19.5, 29.1, 48.3, and 67.7 MeV. The weights of the symmetric (SL) and asymmetric (STI and STII) modes in the mass distributions of photofission of $^{238}\mathrm{U}$ and neutron-induced fission of ${}^{235,238}\text{U}$ at the average excitation energies of up to 20 MeV are calculated on the basis of the obtained results and other available data. The weight of the SL mode increases by about an order of magnitude as the average excitation energy increases from 8.5 to 17 MeV, while the weight of the STI mode decreases by two times, and the weight of the STII mode slightly increases. It is shown that the peak-to-valley ratios in photofission of $^{238}\mathrm{U}$ and neutron-induced fission of $^{235}\mathrm{U}$ are very close across almost the whole studied energy range. A similar conclusion is made concerning the behavior of asymmetric and symmetric fission modes in photofission of $^{238}\mathrm{U}$ and neutron-induced fission of $^{235}\mathrm{U}$ and $^{238}\mathrm{U}$.

Photofission of 238U Nuclei

The spectrum of the 238U(γ, f) photofission reaction which is obtained using bremsstrahlung photon beams from a clinical e-linac is analyzed. The following nuclei 94Y, 134Te, 136Pr, 142Ba, 138Xe, 104Tc in the spectrum of our experiment have been identified. The gamma ray energies of the produced nuclei are compared with the literature values. This work is a proof-of-concept experiment which is the first of in the series of our future planned photofission experiments using a clinical e-linac operated with different endpoint energies.

Isomeric and ground state energy level measurements of natural tellurium isotopes via (γ,n) reaction

We have planned to measure isomeric and ground state energy levels in 120Te(γ,n)119m,gTe, 122Te(γ,n)121m,gTe, 128Te(γ,n)127m,gTe, 130Te(γ,n)129m,gTe photonuclear reactions of natural tellurium induced by bremsstrahlung photons with end-point energy at 18 MeV. The sample was irradiated in the clinical linear electron accelerator (Philips SLi-25) at Akdeniz University Hospital. The gamma spectrum of the tellurium sample was measured using HP(Ge) semiconductor detector (ORTEC) and multi channel analyzer. We used both MAESTRO (ORTEC) and home made root based gui program (Theia) for data analyzing. The obtained experimental data values are compared with NUDAT energy values.

Investigation of the Photo-activation Analysis on Concentrations of Various Materials

It is possible to excite atomic nuclei electromagnetically and even separate proton or neutron from a sample which is exposed to gamma rays by a clinical linac. Thus, the determination of the elemental concentration of a sample by photo-activation analysis is a reasonable attempt since it is related to the detailed analysis of the photonuclear reaction of an intended element. In this study, in order to get the proof of principle for photo-activation a titanium dioxide and a 10 kurus Turkish coin samples are irradiated with high energy bremsstrahlung photons at the end-point energy of 18 MeV and their zinc and copper concentrations are determined by a precise measurement with a high purity germanium detector.

Photonuclear reactions on titanium isotopes

The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes 47,48,49,50Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes 49,50Ti.

Qualitative Elemental Analyses of a Meteorite Sample Found in Turkey by Photo-activation Analysis Method

In this paper, a meteorite sample provided from TÜBITAK National Observatory found in Turkey has been investigated by using a clinical linear accelerator that has endpoint energy of 18 MeV, and a high purity Germanium detector for qualitative elemental analysis within photo-activation analysis method. 21 nuclei ranging from 24Na to 149Nd have been identified in the meteorite sample.

Energy Levels and Half-Lives of Gallium Isotopes Obtained by Photo-Nuclear Reaction

We have run an experiment to determine the energy levels and half-lives of Gallium nucleus by using the photonuclear reactions with end-point energy of 18 MeV bremsstrahlung photons, produced by a clinical linear accelerator. As a result of 71Ga(y,n)70Ga and 69Ga(Y,n)68Ga photonuclear reactions, the energy levels and half-lives of 70Ga and 68Ga nuclei have been determined. The results are in good agreement with the literature values.

Bremsstrahlung-induced fission and spallation of the pre-actinide nucleusTa181

A study of photofission on $^{181}\mathrm{Ta}$ induced by bremsstrahlung with endpoint energies of 50 and 3500 MeV has been performed. The fission yields have been measured by using the induced-activity method in an off-line analysis. The total photofission yields for the tantalum target at 50 and 3500 MeV are found to be $5.4\ifmmode\pm\else\textpm\fi{}1.1 \ensuremath{\mu}\mathrm{b}$/ equivalent quanta per second (eq.q) and $0.77\ifmmode\pm\else\textpm\fi{}0.11$ mb/eq.q, respectively, and the corresponding deduced fissilities are $(0.23\ifmmode\pm\else\textpm\fi{}0.05)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $(2.9\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. Mass- and charge-yield distributions were derived from the data. The results were compared with the simulated results from the crisp code for multimodal fission by the assuming symmetrical fission mode.

The Accuracy Check of Peak Voltages of Industrial X-Ray Machine Using Spectrometer System

Measurement of peak voltage of Philips Industrial X-ray Machine is essential to be carried out at least at annual basis to ensure the accuracy of tube voltage applied in determination of standard radiation qualities for calibrating diagnostic dosemeter. In this paper, the peak voltages for dial voltages range within 40kV to 160kV were measured using Amptek spectrometer system. All X-ray spectrums produced from the X-ray tube were calibrated against standard calibration spectrum that was established using two standard sources: 55Fe and 57Co. The peak voltage for each dial voltage was determined based on the end point energy of the X-ray spectrum. The percentage deviation of measured peak voltage relative to dial voltage was calculated. The results from measurement in 2008 to 2013 demonstrate that all peak voltages from 40kV to 160kV tube potentials are within the tolerance limit of ± 5%. These results complies the recommendation by the International Electrotechnical Commission (IEC) 61676. As a conclusion, regular checks of peak voltage should be performed to ensure consistency of voltage applied to the X-ray tube thus maintain the accuracy of standard radiation qualities produced from the X-ray tube.

Measurement of the internal bremsstrahlung spectrum of a 89Sr beta emitter in the 1–100 keV photon energy regime

The internal bremsstrahlung (IB) spectrum of 89Sr, which is a unique first forbidden beta emitter, is studied in the 1–100keV photon energy regime. The IB spectrum is experimentally measured using a Si(Li) detector, which is efficient in this photon energy regime, and is compared with the IB distributions that are predicted by the Knipp, Uhlenbeck and Bloch (KUB), Nilsson, and Lewis and Ford theories. In the soft energy regime up to 15keV, the measured results are in agreement with all the aforementioned theories. However, from 16–30keV, the experimental results are in agreement with the Lewis and Ford theory, which applies to forbidden transitions, and at higher photon energies, the Nilsson theory best describes the measured results. The differences among the different theories also increase with the photon energy. The effect of the electrostatic Coulomb field on the IB process for beta emitters with different end-point energies is investigated by comparing the ratio of the IB probabilities predicted using the KUB and Nilsson theories for 35S and 89Sr, i.e., soft and hard beta emitters, respectively. The Coulomb effect is shown to be significant in the high photon energy regime and for beta emitters with low end-point energies.

Flux-weighted average cross-sections of natAg(γ, xn)103–106Ag reactions with end-point bremsstrahlung energies of 45–60 MeV

The flux-weighted average cross-sections of the natAg(γ, xn)103–106Ag reaction with the end-point bremsstrahlung energies of 45, 50, 55, and 60 MeV were determined by activation and the off-line γ-ray spectrometric technique using the 100 MeV electron linac at the Pohang accelerator laboratory (PAL). The natAg(γ, xn)103–106Ag reaction cross-sections as a function of the photon energy were estimated from the TENDL-2013 library based on the TALYS 1.6 computer code. The flux-weighted average cross-sections at the end-point bremsstrahlung energies of 45-60MeV were obtained from the literature data and the theoretical data based on the mono-energetic photons. We found that the present data and the flux-weighted theoretical values for the natAg(γ, xn)103–106Ag reaction increase sharply from their threshold values to certain energies where other reaction channels are opened. Then, the first reaction remains constant until the second one reaches its maximum. Thereafter, the first reaction decreases slowly with an increase in the end-point bremsstrahlung energy due to the opening of different reaction channels.

Measurement of isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr in the photonuclear reactions of 89Y and natZr at the end-point bremsstrahlung energies of 45 and 55 MeV

The isomeric yield ratios of 86m,gY, 87m,gY, and 89m,gZr produced in the reactions of 89Y and natZr with end-point bremsstrahlung energies of 45 and 55MeV have been determined by activation and off-line γ-ray spectrometric technique using the 100MeV electron linac at Pohang Accelerator Laboratory (PAL), Korea. The present data along with literature data show that the isomeric yield ratios of 86m,gY and 87m,gY in the 89Y(γ,xn) and natZr(γ,x) reactions and those of 89m,gZr in the natZr(γ,x) reaction increase with the end-point bremsstrahlung energy, which indicates the effect of excitation energy. However, the increase trend of the isomeric yield ratios of 87m,gY in the 89Y(γ,xn) reaction and 89m,gZr in the natZr(γ,x) reaction are very fast from the threshold value to 30MeV due to the giant dipole resonance effect. After certain point of excitation energy, the isomeric yield ratios increase slowly with the end-point bremsstrahlung energy due to the partition of energy in different reaction channels. It was also observed that in both the reactions, the isomeric yield ratios of 87m,gY are always higher than those of 86m,gY. This is because of more number of particle emission and thus the disposition of more excitation energy needed for the formation of 86m,gY compared to 87m,gY.