64Cu Reaction Research Articles

Measurement of 63Ni and 59Ni by accelerator mass spectrometry using characteristic projectile X-rays

The long-lived isotopes of nickel (59Ni, 63Ni) have current and potential use in a number of applications including cosmic radiation studies, biomedical tracing, characterization of low-level radioactive wastes, and neutron dosimetry. Methods are being developed at LLNL for the routine detection of these isotopes by AMS. One intended application is in Hiroshima dosimetry. The reaction 63Cu(n,p)63Ni has been identified as one of a small number of reactions which might be used for the direct determination of the fast neutron fluence emitted by the Hiroshima bomb. AMS measurement of 63Ni (t12 = 100 y) requires the chemical removal of 63Cu, which is a stable isobar of 63Ni. Following the electrochemical separation of Ni from gram-sized copper samples, the Cu concentration is further lowered to < 2 × 10−8 (CuNi) using the reaction of Ni with carbon monoxide to form the gas Ni(CO)4. The Ni(CO)4 is thermally decomposed directly in sample holders for measurement by AMS. After analysis in the AMS spectrometer, the ions are identified using characteristic projectile X-rays, allowing further rejection of remaining 63Cu. In a demonstration experiment, 63Ni was measured in Cu wires (2–20 g) which had been exposed to neutrons from a 252Cf source. We successfully measured 63Ni at levels necessary for the measurement of Cu samples exposed near the Hiroshima hypocenter. For the demonstration samples, the Cu content was chemically reduced by a factor of 1012 with quantitative retention of 63Ni. Detection sensitivity (3σ) was ∼ 20 fg 63Ni in 1 mg Ni carrier (63NiNi ≈ 2 × 10−11). Significant improvements in sensitivity are expected with planned incremental changes in the methods. Preliminary results indicate that a similar sensitivity is achievable for 59Ni (t12 = 105 y). Initial work has been undertaken on the application of this isotope as a biomedical tracer in living systems.

Ultra-separation of nickel from copper metal for the measurement of 63Ni by AMS

Measurements of 63Ni (t12 = 100 yr) produced by the reaction 63Cu(n,p)63Ni could be used in the assessment of fast-neutron fluence from the Hiroshima atomic bomb. Such measurements would add new information to help resolve the current discrepancy between measured thermal neutron activation values and those calculated with the DS86 dosimetry system. It has been estimated that the 63Ni production at 5 m from the hypocenter was (1.4 ± 0.1) × 107 atoms/g Cu. Because of its sensitivity, accelerator mass spectrometry (AMS) is ideal for measurements at this low level. However, 63Ni has to be separated from large amounts of stable atomic isobar 63Cu (69% of pure Cu). In this study, a procedure is presented for the electrochemical separation of ultra-low amounts of Ni from Cu. The method was developed using samples of electrical Cu wire that were irradiated with fission neutrons from a 252Cf source. The wire samples were electrochemically dissolved in a solution containing 1 mg of Ni carrier. The Cu was selectively deposited on a cathode at controlled potential. Measurements of total Ni after electroseparation indicate ∼ 100% carrier recovery. To prevent Cu contamination, AMS targets were prepared by nickel carbonyl generation. The AMS results show a successful quantitative separation of ∼ 107 atoms of 63Ni from 2–20 g samples of Cu.

Partial neutron cross sections for 64Zn, 66Zn, 67Zn and 68Zn between 14.2 and 18.2 MeV

Activation techniques have been used to measure the partial neutron cross sections for the 64Zn(n,p) 64Cu reaction at neutron energies between 14.2 and 17.2 MeV, the 64Zn(n,2n) 63Zn, 66Zn(n,p) 66Cu and 67Zn(n,p) 67Cu reactions from 14.2 to 18.2 MeV, and the 68Zn(n,p) 68mCu and 68Zn(n,α) 65Ni reactions between 14.2 and 16.2 MeV. The mixed powder method and a Ge(Li) detector gamma-ray spectrometer were utilized in the measurements. Neutrons were produced by the 3H(d,n) 4He reaction, and the neutron flux was measured through the 27Al(n,α) 24Na reaction. The reactions, the measured cross sections and the respective neutron energies (each with a spread of ±0.2 MeV) are as follows: 64Zn(n,p) 64Cu, 180 ± 10, 152 ± 9, 116 ± 6 and 122 ± 8 mb at 14.2, 15.2, 16.2 and 17.2 MeV; 64Zn(n,2n) 63Zn, 121 ± 6, 176 ± 10, 222 ± 13, 267 ± 17 and 327 ± 27 mb at 14.2, 15.2, 16.2, 17.2 and 18.2 MeV; 66Zn(n,p) 66Cu, 76 ± 5, 72 ± 6, 71 ± 8, 62 ± 7 and 57 ± 7 mb at 14.2, 15.2, 16.2, 17.2 and 18.2 MeV; 67Zn(n,p) 67Cu, 82 ± 5, 106 ± 6, 125 ± 8, 141 ± 21 and 230 ± 30 mb at 14.2, 15.2, 16.2, 17.2 and 18.2 MeV; 68Zn(n,p) 68mCu, 5 ± 0.6, 6 ± 1 and 2 ± 1 mb at 14.2, 15.2 and 16.2 MeV; 68Zn(n,α) 65Ni, 10 ± 0.7, 9 ± 0.7 and 7 ± 1 mb at 14.2, 15.2 and 16.2 Mev.

A method to determine the absolute neutron output of small D-T neutron generators

We propose a standard method of establishing the absolute neutron output from small, D-T, 14 MeV neutron generators. This method uses a copper activation measurement in a configuration that we have calibrated with fission ionization chambers from NIST. The absolute uncertainty in this calibration is less than ± 7%. The copper activation method is insensitive to backgrounds from low energy scattered neutrons because it uses the 63Cu(n, 2n) 62Cu reaction which has a 12 MeV threshold. With this calibration method, measurements of absolute neutron output are possible under a variety of experimental conditions, including those simulating nuclear well logging. In addition, the configuration of the copper samples that we propose gives high counting rates so that the statistical precision of the measurement of neutron output, depending upon the generator voltage and beam current, is on the order of 1%.

Excitation functions of proton induced nuclear reactions on enriched 61Ni and 64Ni: Possibility of production of no-carrier-added 61Cu and 64Cu at a small cyclotron

Excitation functions were measured by the stacked-foil technique for 61Ni(p,n) 61Cu and 61Ni(p,2n) 60Cu nuclear reactions using 88.84% enriched 61Ni and for 64Ni(p,n) 64Cu reaction using 95% enriched 64Ni from threshold up to 18.6 MeV. The optimum energy range for the production of both 61Cu and 64Cu was found to be 12 → 9 MeV. The calculated thick target yield of 61Cu amounts to 17.5 mCi (647 MBq)/γAh. At the given enrichment the yield was 15.5 mCi (573 MBq)/γAh and the expected level of 60Cu and 64Cu impurities at EOB reached 14.59 and 0.086%, respectively. For production of 64Cu the yield was 6.71 mCi (248 MBq)/γAh. At 95% enrichment of the target material the 64Cu yield amounts to 6.38 mCi (236 MBq)/γAh and the 60Cu and 61Cu impurities at EOB are 10.01 and 0.41%, respectively. An anion-exchange chromatographic technique for the separation of radiocopper from activated Ni target was developed. The 61Ni(p,n) 61Cu and 64Ni(p,n) 64Cu processes are suited for the production of 61Cu and 64Cu at a small cyclotron. The common production routes for 64Cu are briefly reviewed.

Calibration of the fission-track dating method: Is Cu useful as an absolute thermal neutron fluence monitor?

Thermal neutron fluence measurements have been performed with Au and Co standard monitors at the one side and Cu monitors (foils and wires) at the other. using three reactor channels with different neutron energy spectra and two calibrated Ge detectors. Care was taken to eliminate errors caused by epithermal activation and neutron self-shielding while special attention was also paid to the problem of incomplete annihilation of the 64Cu β + radiation. Our new measurements reveal consistent fluences between Cu and the Au and Co standard monitors, when using the recommended and/or recently evaluated nuclear parameters for the 63Cu(n,γ) 64Cu reaction. However, we do not endorse the usage of Cu as a standard fluence monitor for fission-track dating because from a metrological standpoint too large uncertainties still exist on some of its relevant nuclear parameters such as the thermal neutron activation cross-section ( σ 0) of 63Cu.

Excitation functions for deuteron induced reactions in natural nickel: Production of no-carrier-added 64Cu from enriched 64Ni targets for positron emission tomography

The excitation functions for the production of 64Cu and other radionuclides by the deuteron irradiation of natural Ni targets have been measured up to 19 MeV incident energy. The excitation function for the 64Ni(d, 2n) 64Cu reaction shows a maximum effective cross section of 7.2±0.9 mbarn at 16.2 MeV for the natural Ni target. Data have been used for the production of large quantities of 64Cu by the deuteron irradiation of enriched (96.4%) 64Ni targets. The radiochemical extraction procedures developed can produce either carrier-free 64Cu or utilize a small amount (50 μg) of carrier. The thick target yield of 64Cu is 107 ± 16 GBq/C (10.5 ± 1.6 mCi/ μ Ah) and the contamination with 61Cu is only 0.29% at EOB. Data on the production yields of 61Cu, 64Cu, 57Ni, 55Co, 56Co 57Co and 58Co during the deuteron irradiation of natural Ni and enriched 64Ni targets are presented.

Use of the 28Si(n, p)28Al reaction for the measurement of 14 MeV neutrons from fusion plasmas

The 28Si(n, p)28Al reaction is shown to be ideal for monitoring the emission of 14 MeV neutrons from d-t fusion plasmas. The daughter nuclide, 28Al, has a 2.246 min half-life and so is suitable for studying discharges of up to 1 min duration; the decay gamma radiation has an energy of 1.779 MeV and is easily detected with a NaI(Tl) detector. The same sample can be recycled for successive JET discharges and the data taking is fully automatic. Absolute neutron yields are obtained by calibrating with the standard 63Cu(n, 2n)62Cu reaction. The effective threshold energy of 5 MeV completely discriminates against 2.5 MeV d-d neutrons, making this reaction also highly appropriate for the study of the 14 MeV neutrons emitted during the burnup of the 1.0 MeV tritons produced in the second branch of the d-d reaction. Some results from this application will be presented.

The 63Cu(α, p) 66Zn cross section and the corresponding thermonuclear reaction rate

Differential cross sections and excitation functions for the reaction 63Cu(α, p) 66Zn have been measured over the energy range E α = 6–10 MeV. Results of statistical model calculations are compared to the excitation functions for individual proton groups and are found to give good representations to within about a factor of two. The data and the calculated cross sections are used to determine the thermonuclear reaction rates for temperatures of astrophysical interest.

Calibration of the TFTR neutron activation system

Neutron generators, both D–D and D–T, have been used to calibrate the TFTR neutron activation (NA) system for point sources located within the tokamak. The foils used were In for D–D neutrons and Cu, Al, and 238U for D–T neutrons. Delayed neutrons following fission were counted when using 238U foils, 336-keV γ rays from 115In(n,n′)115m In reactions, annihilation radiation from 62Cu following the 63Cu(n,2n)62Cu reaction, and 1368- and 2754-keV γ rays from the 27Al(n,α)24Na reaction. Large effects caused by source anisotropy and local machine structure were observed. These effects and the attempts to accommodate them in the data analysis will be described.

Spatial distribution of radionuclides produced in copper by photonuclear spallation reactions

The spatial distribution of radionuclides produced in a 15 cm thick copper target, which is commonly used as accelerator material, was measured by bombarding the bremsstrahlung radiation generated by 900 MeV electrons. The production of radionuclides of 64Cu, 61Cu, 60Cu, 58Co, 57Co, 55Co, 56Mn, 52Mn, 48Sc, 47Sc,and 44mSc was clearly identified up to about 10 cm in depth. The spatial distribution of bremsstrahlung radiation in copper was also calculated by the electromagnetic cascade Monte Carlo code, EGS-4. By comparing the experimental data and the calculated results, the effective cross sections and the effective energy ranges were derived for 65Cu(γ,n) 64Cu, 63Cu(γ,2n) 61Cu, 63Cu(γ,3n) 60Cu and other photonuclear spallation reactions.

The yrast bands in 77Kr and 76Kr

High-spin states of both parities in 77Kr have been studied in the reaction 63Cu( 16O, pn). On the basis of γγ- and nγ-coincidence experiments, we extended the yrast bands up to spin I π = 25 2 + and 21 2 t-. Doppler-shift attenuation and recoil-distance measurements have been performed for some fifteen states. In addition, lifetimes of some yrast states in 76Kr have been determined in the reaction 63Cu( 16O, p2n). Transition energies and E2 strengths in 76Kr have been interpreted with the IBA-2 and different collective and microscopic triaxial rotor models, those in 77Kr with the triaxial rotor plus quasiparticle model.

Gamma-ray spectroscopy of62Cu

A spectroscopy study has been made of the62Ni(p,nγ)62Cu reaction, allowing levels in62Cu to be investigated up toEx=1.843 MeV. Ten new levels and eleven spins are given.

55Co]- and [ 64Cu]DTPA: New radiopharmaceuticals for quantitative tomocisternography

The diethylenetriaminepentaacetic acid (DTPA) complexes of the convenient half-life positron emitters 55Co and 64Cu have been prepared for quantitation of cerebrospinal fluid (CSF) kinetics in different areas of the brain using positron emission tomography. The radionuclides are prepared by proton bombardment of natural nickel ( 58Ni(p,α) 55Co and 64Ni (p,n) 64Cu reactions). The chemical separation of the radionuclides from the target is described, and the production yields, radionuclidic purities and specific activities are given.

Coulomb excitation and lifetime measurements of the 2 1+ states in 76, 82, 84Kr

A mean lifetime of τ = 35 ± 3 ps of the 2 + 1 state in 76Kr has been measured with the recoil distance method via the reaction 63Cu( 19F, α2n) 76Kr. The B(E2; 0 + 1 → 2 + 1) values and lifetimes of the 2 + 1 states in 82, 84Kr have been measured via Coulomb excitation using the 1.4 MeV/A UNILAC krypton beams. The intensities of the γ-rays from the Coulomb excited levels of 82, 84Kr were interrelated with those of the target nuclei 27Al, 64, 66Zn and 70, 72, 74, 76Ge and yielded the values B( E2; 0 + 1 → 2 + 1 = 0.255±0.009 and 0.122 ± 0.005 e2 · b2 for 82, 84 Kr , respectively. In turn, these B( E2) values and the (E2; 0 + 1 → 2 + 1 values of the even Ge and Zn isotopes from the literature were used in a Doppler-shift attenuation analysis to obtain experimentally lacking electronic stopping power for Kr ions slowing down in Al, Zn and Ge. for Ge ions in Ge and for Zn ions in Zn.

Some activation measurements with 3H(d, n) 4He neutrons

Accuracy of the concentric ring geometry for fast neutron monitoring is verified by activating concentric rings and discs, which were made of copper, and measuring the neutron fluxes using the 63Cu(n, 2n) 62Cu reaction. Consistent results were obtained using 3H(d, n) 4He neutrons from Van de Graaff and Dynamitron accelerators. In addition, 12.9–15.9 MeV neutrons were used to measure the excitation function for the 121Sb(n, 2n) 120gSb reaction and the ratios of 63Cu(n, 2n) 62Cu and 27Al(n, p) 27Mg reaction cross-sections, which were used for neutron energy determination. The investigation includes also a novel gamma ray counting method for the determination of the antimony cross-section, and recommendations for establishing the concentric ring technique as a standard.

(p, γ) reaction studies on 60Ni

The γ-ray spectra from the 60Ni(p, γ) 61Cu reaction were measured for 27 isolated resonances. From these studies the J π assignment of the compound states in 61Cu were made. Moreover, a value for the El photon strength function k(El) = 1.03 × 10 −9 MeV −3 was obtained from seven l = 0 resonances to the 16 low-lying states. This value was then compared with the theoretical estimates of El strengths as predicted from the s.p. and giant dipole resonance models. The distribution of partial radiative widths about their mean value was determined from a Monte Carlo technique and was found to be consistent with the Porter-Thomas distribution when the Γ γ, ij were divided by the E γ 5 energy dependence. Values for the coefficients of the correlation R between Γ λ, p and Γ λ, γj and T between Γ λ, yj and Γ λ, γƒ where f ≠ j, were computed with the values R = 0.14 and T = 0.39, respectively. Also the correlation coefficients C(〈 Γ λ, yj 〉, I 3He, d, j) and C(〈Γ λ, yƒ〉 I d, n, ƒ ) yielded the values ρ = 0.87 and ρ = 0.80 respectively. All these correlations which are found to be statistically significant, imply that the (p, γ) reaction in 60Ni is partly due to direct capture such as given by valence and doorway state contributions.

Preparation of carrier-free 67Cu by the 68Zn( γ, p) reaction

The 68Zn( γ, p) 67Cu reaction by the use of an isotopically enriched 68Zn (98.97%) target has proved to be useful for the preparation of the carrier-free 67Cu in a high radionuclidic purity. The production rates of 67Cu and contaminants were determined as a function of the maximum bremsstrahlung energies between 30 and 60 MeV; the chemical separation of the carrier-free 67Cu and the recovery of the 68Zn target were also studied.

Measurements of63Cu(n,2n)62Cu and27Al(n,p)27Mg reaction cross sections for 12.9-15.9 MeV neutrons

63Cu(n,2n)62Cu and 27Al(n,p)27Mg reaction cross sections were measured in the 12.9-15.9 MeV energy region under improved experimental conditions to resolve the discrepancies in the published data. The experimental procedures included irradiation in a low neutron scattering environment and the use of the concentric ring technique for fast-neutron monitoring. A consistency between the results obtained using a Dynamitron and Van de Graaff particle accelerators is reported. Comparison of the experimental results with statistical-model calculations indicate that the 63Cu(n,2n)62Cu reaction proceeds predominantly by compound nucleus formation. A direct interaction contribution must be included for the 27Al(n,p)27Mg reaction.

Production of 61Cu by α and 3He Bombardment on Cobalt Target

Abstract In order to determine the optimum irradiation conditions to produce the 61Cu for nuclear medical use, excitation curves and thick-target yield curves were determined for the α reactions producing 61Cu, 57Co, and 58Co, and 3He reactions producing 61Cu, 56Co, 57Co, and 58Co, both from natural cobalt. The 59Co(α, 2n) 61Cu and the 59Co(3He, n) 61Cu reactions give cross section peaks of 340 mb and 6 mb at 25 MeV and 35 MeV, respectively. The 61Cu thick-target yields for these reactions at 40 MeV were 6 mCi/μAh and 110 μCi/μAh, respectively. A simple and reliable anion-exchange method was developed to provide carrier-free 61Cu. The purity of 61Cu was determined with a Ce(Li) spectrometer. Photopeak efficiencies have been calculated at principal γ-ray energies of 61Cu, 64Cu, and 67Cu, for a 1/2 in. NaI scintillation camera. Alternative nuclear reactions and the methods for producing 61Cu are compared.