Production of 38K via the 38Ar(p,n)-process at a small cyclotron

The excitation function of the ³⁸Ar(p, n)³⁸K reaction was measured from threshold up to 18 MeV by the activation technique using isotopically enriched ³⁸Ar as target gas. Differential and integral yields of ³⁸K were calculated. The optimum energy range for production was found to be E_p = 16 → 12 MeV, the ³⁸K yield at saturation amounting to 21 mCi (777 MBq)/μA. Experimental thick target yields of ³⁸K were determined under high current production conditions using ^natAr and enriched ³⁸Ar as target gases. The ³⁸Ar(p, n)³⁸K process is ideally suited for production of ³⁸K at a small cyclotron.     

Excitation functions of (p, 2n) and (p,pn) reactions and differential and integral yields of 123I in proton induced nuclear reactions on highly enriched 124Xe

Excitation functions were measured for (p, 2n) and (p, pn) reactions on 99.9% enriched ¹²⁴Xe from threshold up to 44 MeV. The (p, 2n) reaction is much stronger than the (p, pn) channel; above 36 MeV, however, the two processes have almost equal cross sections. Differential yields of ¹²³I were measured experimentally as a function of proton energy and were also calculated from the excitation functions. Our experimental and theoretical yield data are consistent within 15%, but are lower by a factor of 2 than the literature experimental values. Our studies show that the optimum energy range for the production of ¹²³I is E_p = 29 → 23 MeV. The theoretically expected thick target yield of ¹²³I at 6.6 h after EOB is 11.2 mCi/μAh, and is in agreement with the high-current experimental production yields.     

Excitation function and thick target yield of the Ar(α,p)K reaction: Production of K

The excitation function of the ⁴⁰Ar(α,p)⁴³K nuclear reaction has been measured via the activation technique using stacked gas cell targets. Absolute cross section values were deducted from the experimental data and were compared with theoretical predictions calculated by means of the STAPRE code. Thick target yields of ⁴³K were calculated from the experimental data. A target system working in static (batch) or in recirculating gas flow mode has been developed to produce ⁴³K.     

A novel way of producing an aqueous solution of K via the Ar(p, 3n)-Process

A novel way of producing ³⁸K⁺ has been developed which enables a rapid, remote and effective production of ³⁸K⁺ repeatedly via the ⁴⁰Ar(p, 3n) process. An i.v. injectable solution of 610±30 MBq ³⁸K⁺ was obtained in 2.2±0.4 min from EOB with a specific activity of 690±140 GBq/μmol and a radionuclidic purity of >99.9%, by irradiating natural argon gas (20 bar, 150 mm thick) with 40 MeV protons (39.2 MeV on target) at 6–6.5 μA for 15 min.     

Production of 73Se via (p, 3n) and (d, 4n) reactions on arsenic

Excitation functions were measured for ⁷⁵As(p, xn) ^{72, 73, 75}Se reactions over the energy range of 3–45 MeV and for ⁷⁵As(d, xn) ^{72, 73, 75}Se reactions from 5 to 56 MeV. Thin targets were prepared by electrolytic deposition of arsenic on Cu-, or Al-backing. The optimum energy ranges for the production of ⁷³Se were found to be E_p = 40 → 30 MeV and E_d = 45 → 33 MeV; theoretical thick target yields of ⁷³Se amount to 38 and 17.6 mCi/μAh, respectively, and the levels of ^{72, 75}Se impurities to <0.2%. An anion-exchange method was developed to separate no-carrier-added radioselenium. Irradiations of As₂O₃ for 2 h at nominal currents of 2 μA lead to batch yields of ⁷³Se (at EOB) of about 70 mCi in the case of the (p, 3n) reaction and about 35 mCi in the (d, 4n) reaction.     

The reactions 77Se(p,n) and 78Se(p, 2n) as production routes for 77Br

Yield curves were measured for the ⁷⁷Se(p, n)⁷⁷Br reaction and the ⁷⁸Se(p, 2n)⁷⁷Br reaction involving isotopically enriched selenium targets. Also the contamination levels due to ⁷⁶Br and ⁸²Br were measured. The suitability of both reactions for production of ⁷⁷Br for use in nuclear medicine is shown. The possibility of a dry-distillation technique for both a carrier-free separation of ⁷⁷Br from irradiated enriched selenium targets and a quantitative recovery of the selenium is discussed.     

Cross section measurements for (n, 3n) reactions induced by 14.8 MeV neutrons.

The cross sections for 209Bi(n, 3n)207Bi, 191Ir(n, 3n)189Ir, 151Eu(n, 3n)149Eu and 185Re(n, 3n)183Re reactions were measured by the activation method. The experimental results were 12.1+/-1.1, 64.6+/-6.5, 2.7+/-0.4 and 66.0+/-5.6 mb at the neutron energy of 14.8+/-0.2 MeV, respectively. The neutron flux was determined by the cross section of the 27Al(n, alpha)24Na reaction. The neutron energy in these measurements was determined by the method of cross section ratios for 90Zr(n, 2n)(89m + g)Zr and 93Nb(n, 2n)92mNb reactions.     

Systematics for the cross-sections of the reactions (n, p), (n, alpha) and (n, 2n) at 14.5 MeV neutrons.

Systematics are proposed for the (n, p), (n, alpha) and (n, 2n) reactions cross-sections at 14.5 MeV neutron energy based on the statistical model, with consideration of the Q-value dependence and odd-even effects. The obtained relations are compared with other recently proposed systematics based on the statistical model as well as on the asymmetry parameter dependence.     

Cross-section measurements for (n, 2n), (n, p) and (n, n′α) reactions on gallium isotopes in the neutron energy range of 13.5–14.6 MeV

Cross-sections for (n, 2n), (n, p) and (n, n'alpha) reactions have been measured on gallium isotopes at the neutron energies of 13.5-14.6MeV using the activation technique. Data are reported for the following reactions: 69Ga(n, 2n) 68Ga, 69Ga(n, p) 69mZn, 71Ga(n, p) (71m)Zn, and 71Ga(n, n'alpha) 67Cu. The neutron fluences were determined using the monitor reaction 93Nb(n, 2n) 92mNb.     

Calculations for the excitation functions of the 63Cu(p,n)63Zn, 63Cu(p, 2n)62Zn and 65Cu(p,n)65Zn reactions.

Calculations for the excitation functions of 63Cu(p, n)63Zn, 63Cu(p, 2n)65Zn and 65Cu(p, n)65Zn reactions have been carried out in 3-30 MeV energy range using statistical and pre-equilibrium nuclear reaction models. The calculations have been compared with reported measurements and discussed.     

Application of deuteron-deuteron (D-D) fusion neutrons to 40Ar/39Ar geochronology.

Neutron irradiation of samples for 40Ar/39Ar dating in a 235U fission reactor requires error-producing corrections for the argon isotopes created from Ca, K, and, to a lesser extent, Cl. The fission spectrum includes neutrons with energies above 2-3 MeV, which are not optimal for the 39K(n,p)39Ar reaction. These higher-energy neutrons are responsible for the largest recoil displacements, which may introduce age artifacts in the case of fine-grained samples. Both interference corrections and recoil displacements would be significantly reduced by irradiation with 2.45 MeV neutrons, which are produced by the deuteron-deuteron (D-D) fusion reaction 2H(d,n)3He. A new generation of D-D reactors should yield sufficiently high neutron fluxes (>10(12) n cm(-2)s(-1)) to be useful for 40Ar/39Ar dating. Modeling indicates that irradiation with D-D neutrons would result in scientific benefits of improved accuracy and broader applicability to fine-grained materials. In addition, radiological safety would be improved, while both maintenance and operational costs would be reduced. Thus, development of high-flux D-D fusion reactors is a worthy goal for 40Ar/39Ar geochronology.     

Cross sections for (n, 2n), (n, p) and (n, α) reactions on rare-earth isotopes at 14.7 MeV

Cross sections for (n, 2n)·(n,p) and (n, α) reactions have been measured on some rare-earth isotopes at 14.7±0.2 MeV using the activation technique. Data are reported for the following reactions: ¹⁵⁴Sm(n,2n) ¹⁵³Sm, ¹⁶²Er(n, 2n) ¹⁶¹Er, ¹⁶⁸Yb(n, 2n) ¹⁶⁷Yb, ¹⁷⁴Hf(n, 2n) ¹⁷³Hf, ¹⁷⁶Hf(n, 2n) ¹⁷⁵Hf, ¹⁴²Ce(n, p) ¹⁴²La, ¹⁴⁴Sm(n, p) ¹⁴⁴Pm, ¹⁴⁸Sm(n, p) ^148mPm, ¹⁴⁸Sm(n, p) ^148gPm, ¹⁵⁰Sm(n, p) ¹⁵⁰Pm, ¹⁶⁰Dy(n, p) ¹⁶⁰Tb, ¹⁶²Dy(n, p) ¹⁶²Tb, ¹⁶³Dy(n, p) ¹⁶³Tb, ¹⁶⁶Er(n, p) ^166gHo, ¹⁶⁷Er(n, p) ¹⁶⁷Ho, ¹⁶⁸Er(n, p) ¹⁶⁸Ho, ¹⁷⁴Yb(n, p) ¹⁷⁴Tm, ¹⁵⁰Sm(n, α) ¹⁴⁷Nd, ¹⁵²Sm(n, α) ¹⁴⁹Nd, ¹⁵⁴Sm(n, α) ¹⁵¹Nd, ¹⁵³Eu(n, α) ¹⁵⁰Pm, ¹⁵⁹Tb(n, α) ¹⁵⁶Eu, ¹⁶²Dy(n, α) ¹⁵⁹Gd, ¹⁶⁴Dy(n, α) ¹⁶¹Gd, ¹⁶⁸Er(n, α) ¹⁶⁵Dy, ¹⁶⁹Tm(n, α) ^166gHo, ¹⁷⁸Hf(n, α) ¹⁷⁵Yb, ¹⁸⁰Hf(n, α) ¹⁷⁷Yb.     

Proton beam monitoring via the Cu(p,x) 58Co, 63Cu(p, 2n) 62Zn and 65Cu(p,n) 65Zn reactions in copper

Cross sections for the Cu(p, x) ⁵⁸Co, ⁶³Cu(p, 2n) ⁶²Zn and ⁶⁵Cu(p, n) ⁶⁵Zn reactions were measured in the energy region from 4 to 33 MeV. The excitation functions for ⁵⁸Co, ⁶²Zn and ⁶⁵Zn were determined and compared with the published data. The experimental cross sections have been used as reference data for proton beam monitoring in the energy range of 13–33 MeV.     

Activation cross-sections for Dy(n,p)Tb, Dy(n,α)Gd and Dy(n,p)Tb reactions induced by neutrons at 14.7 MeV

The cross-sections for the ¹⁵⁸Dy(n,p)¹⁵⁸Tb, ¹⁵⁶Dy(n,α)¹⁵³Gd and ¹⁶⁰Dy(n,p)¹⁶⁰Tb reactions induced by 14.7 MeV neutrons were measured in this work and calculated by a previously developed formula. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. Nuclear model calculations using the code HFTT, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of the products.     

Cross sections for (n, 2n), (n, p) and (n, alpha) reactions on osmium isotopes in the neutron energy range of 13.5-14.8MeV.

Cross sections for (n, 2n), (n, p) and (n, alpha) reactions on the osmium isotopes were measured in the neutron energies 13.5-14.8MeV by the activation technique with the monitor reaction (93)Nb(n, 2n)(92m)Nb. Our measurements were carried out by gamma-detection using a coaxial high-purity germanium (HPGe) detector. Natural high-purity osmium powder (99.9%) was fabricated as the samples. The neutron energies were determined by the cross-section ratios for (93)Nb(n, 2n)(92m)Nb and (90)Zr(n, 2n)(89m+g)Zr reactions. The fast neutrons were produced by the T(d, n)(4)He reaction. The results obtained were compared with previous data.     

Analysis of epithermal neutron production by near-threshold (p,n) reactions

A recent advance in portable accelerator neutron source development was research on production of epithermal neutrons by near-threshold charged-particle reactions. When the projectile energy is accurately controlled at an energy close to the reaction threshold, the neutrons produced will have energies less than or around 100 keV and can be used with little or no moderation or filtration in neutron capture therapy. Although the total neutron yield is lower than at higher proton energies, the epithermal neutron flux may be sufficiently intense because of the softer energy spectrum and the requirement for less neutron moderation. This paper presents an analysis of the main characteristics of epithermal neutron production by this method using the Li (p,n) reaction as an example. The energy, yield and angular characteristics of neutron emission are discussed. The achievable epithermal fluxes are computed from experimental data. The results are used to assess the feasibility of near-threshold production of epithermal neutrons for neutron capture therapy with compact accelerators such as a RFQ proton acceelerator. The results indicated that, using a Li₃N target, 1 mA of 2 MeV protons will produce 10⁹ n/cm²/s with an average energy of 83 keV while 5.6 mA of 1.91 MeV protons can produce 10⁹ n/cm²/s with an average energy of 45 keV.     

Evaluation of excitation functions of 100Mo(p,d+pn)99Mo and 100Mo (p,2n)99mTc reactions: Estimation of long-lived Tc-impurity and its implication on the specific activity of cyclotron-produced 99mTc

Excitation functions were calculated by the code TALYS for 10 proton-induced reactions on ¹⁰⁰Mo. For ¹⁰⁰Mo(p,d+pn)⁹⁹Mo and ¹⁰⁰Mo(p,2n)^99mTc, calculations were also performed using the code STAPRE. Furthermore, for those two reactions and ^natMo(p,x)⁹⁶Tc, evaluation of available experimental data was also carried out. The production of ^99mTc via the ¹⁰⁰Mo(p,2n)-process is discussed. The ratio of atoms of long-lived ^99gTc and ⁹⁸Tc to those of ^99mTc is appreciably higher in cyclotron production than in generator production of ^99mTc; this may adversely affect the preparation of ^99mTc-chelates.     

Excitation function for (63)Cu(n,p)(63)Ni reaction in neutron energy range up to 15MeV.

The excitation function for the (63)Cu(n,p)(63)Ni reaction has been measured by activation method using the 4.5MV Dynamitron accelerator of the Fast Neutron Laboratory of Tohoku University. Copper plates and hollow spherical copper shells were irradiated by neutrons of various energy up to 14.9MeV produced by the T(p,n), D(d,n), and T(d,n) reactions. The (63)Ni produced in the irradiated copper target was chemically separated. The beta-rays emitted from the extracted (63)Ni were measured by a liquid scintillation method. The cross sections obtained were compared with the evaluated data files of JENDL-3.3, ENDF/B-VI and FENDL/A-2.0. Consequently, it is found that FENDL/A-2.0 is consistent with our experimental data in the energy range studied in this work. The effect of proton shell appeared in the excitation function obtained is also discussed.