Excitation functions of 120Te(d,xn)121,120m,gI reactions from threshold up to 13.5 MeV: comparative studies on the production of 120gI.

Excitation functions of the nuclear reactions 120Te(d,xn)121,120m,gI were measured for the first time from their respective thresholds up to 13.5 MeV. Thin samples prepared by electrolytic deposition of 99.0% enriched 120Te on Ti-backing were used. Integral yields of 121,120m,gI were calculated from the measured cross section data. A comparison of the 122Te(p,3n)-, 120Te(p,n)- and 120Te(d,2n)-processes for the production of 120gI is given. The 120Te(d,2n)-process is unsuitable for production purposes since the yield of 120gI is very low and the level of 121I impurity very high. The choice lies either on the 122Te(p,3n)- or the 120Te(p,n)-reaction and is governed by the available proton energy and the financial resources for procuring the enriched target material.     

Excitation functions of 124Te(d,xn)124,125I reactions from threshold up to 14 MeV: comparative evaluation of nuclear routes for the production of 124I.

Excitation functions of the nuclear reactions 124Te(d,xn)124-125I were measured from their respective thresholds up to 14.0 MeV via the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 99.8% enriched 124Te on Ti-backing. The excitation function of the 124Te(d,n)125I reaction was measured for the first time. The present data for the 124Te(d,2n)124I reaction are by an order of magnitude higher than the literature experimental data but are in good agreement with the results of a hybrid model calculation. From the measured cross sections, integral yields of 124,125I were calculated. The energy range Ed = 14 --> 10 MeV appears to be the best compromise between 124I-yield and 1251-impurity. The calculated 124I-yield amounts to 17.5 MBq/microA h and the 125I-impurity to 1.7%. A critical evaluation of the three nuclear routes for the production of 124I, viz. 124Te(d,2n)-, 124Te(p,n)- and 125Te(p,2n)-processes, is given. The reaction studied in this work proved to be least suitable. The 124Te(p,n)-reaction gives 124I of the highest radionuclidic purity, and a small-sized cyclotron is adequate for production purposes. The 125Te(p,2n)-reaction is more suitable at a medium-sized cyclotron: the yield of 124I is four times higher than in the other two reactions but the level of 0.9% 125I-impurity is relatively high.     

Excitation functions of 85Rb(p,xn)(85m,g,83,82,81)Sr reactions up to 100 MeV: integral tests of cross section data, comparison of production routes of 83Sr and thick target yield of 82Sr.

The beta+ emitter 83Sr (T(1/2) = 32.4 h, Ebeta+ = 1.23 MeV, Ibeta+ = 24%) is a potentially useful radionuclide for therapy planning prior to the use of the beta+ emitter 89Sr (T(1/2) = 50.5 d). In order to investigate its production possibility, cross section measurements on the 85Rb(p,xn)-reactions, leading to the formation of the isotopes (85m,g)Sr, 83Sr, 82Sr and 81Sr, were carried out using the stacked-foil technique. In a few cases, the products were separated via high-performance liquid chromatography. For 82Sr, both gamma-ray and X-ray spectrometry were applied; in other cases only gamma-ray spectrometry was used. From the measured excitation functions, the expected yields were calculated. For the energy range Ep = 37 --> 30 MeV the 83Sr yield amounts to 160 MBq/microA h and the level of the 85gSr (T(1,2) = 64.9 d) and 82Sr (T(1/2) = 25.5 d) impurities to <0.25%. In integral tests involving yield measurements radiostrontium was chemically separated and its radioactivity determined. The experimental production data agreed within 10% with those deduced from the excitation functions. The results of the 85Rb(p,3n)83Sr reaction were compared with the data on the production of 83Sr via the 82Kr(3He,2n)-process. In the energy range E3Hc = 18 --> 10 MeV the theoretical yield of 83Sr amounts to 5 MBq/microA h and the 82Sr impurity to about 0.2%. The method of choice for the production of 83Sr is thus the 85Rb(p,3n)-process, provided a 40 MeV cyclotron is available. During this study some supplementary information on the yield and purity of 82Sr was also obtained.     

Excitation functions and yields for 111In production using 113, 114,natCd(p,xn)111In reactions with 65 MeV protons

Excitation function for the ¹¹³Cd(p,3n)¹¹¹In and ¹¹⁴Cd(p,4n)¹¹¹In reactions were measured by the stacked-foil technique in the energy range from 63 to 3 MeV. The results were compared with theoretical calculations based on the hydrid model using the well developed computer code ALICE. For the same energy range, the effective cross-sections were determined for the ^natCd(p,xn)¹¹¹In reactions. At the initial proton energy of 63 MeV for production of ¹¹¹In from ¹¹³Cd, ¹¹⁴Cd and ^natCd the cumulative yields were found as 16.7, 15.7 and 10.4 mCi/μ Ah respectively. The contamination of the undesired nuclide ^114mIn was determined. The no carrier added (NCA) ¹¹¹In was separated from the cadmium cyclotron-target by a procedure based on ion exchange chemistry. The radionuclidic purity of the final radioindium was determined.     

Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.     

Excitation functions of natGe(p,xn)71,72,73,74 As reactions up to 100 MeV with a focus on the production of 72 As for medical and 73 As for environmental studies.

Excitation functions for the formation of the arsenic radionuclides (71)As, (72)As, (73)As and (74)As in the interaction of protons with (nat)Ge were measured from the respective threshold energy up to 100 MeV. The conventional stacked-foil technique was used and the needed thin samples were prepared by sedimentation. Irradiations were done at three cyclotrons: CV 28 and injector of COSY at Forschungszentrum Jülich, and Separate Sector Cyclotron at iThemba LABS, Somerset West. The radioactivity was measured via high-resolution gamma-ray spectrometry. The measured cross section data were compared with the literature data as well as with the nuclear model calculations. In both cases, the results generally agree but there are discrepancies in some areas, the results of nuclear model calculation and some of the literature data being somewhat higher than our data. The integral yields of the four radionuclides were calculated from the measured excitation functions. The beta(+) emitting nuclide (72)As (T(1/2)=26.01 h) can be produced with reasonable radionuclidic purity ((71)As impurity: <10%) over the energy range E(p) = 18-->8 MeV; the yield of 93 MBq/microAh is, however, low. The radionuclide (73)As (T(1/2)=80.30 d), a potentially useful indicator in environmental studies, could be produced with good radionuclidic purity ((74)As impurity: <11%) over the energy range E(p) = 30 --> 18 MeV, provided, a decay time of about 60 days is allowed. Its yield would then correspond to 2.4 MBq/microAh, and GBq amounts could be produced when using a high current target.     

Excitation functions for the production of 82Sr by proton bombardment of natRb at energies up to 100 MeV.

The excitation functions for the production of (82)Sr and other radionuclides produced in the proton bombardment of rubidium were measured by means of the activation technique. Stacks were assembled from RbCl targets, aluminium and copper monitor foils and bombarded with protons of energy up to 100 MeV and nominal current 0.1 microA. The measured data were compared with the theoretical calculations obtained by means of ALICE-IPPE, and also with previously published data. The measured data sets exhibit good agreement at incident energies below 45 MeV and greater than 60 MeV but show large discrepancies in the energy range between these values. The ALICE-IPPE calculations evidently overestimate all reported experimental cross sections, in particular overestimating the present data by a factor of 1.6. Notwithstanding the fact that there are discrepancies in the cross sections, good agreement is found with regards to the shape of the excitation function.     

A rapid and high-yield preparation method for 87Y/87mSr generators,using the 88Sr(p,2n) reaction

For production of ⁸⁷Y/^87mSr generators, the ⁸⁸Sr(p, 2n)⁸⁷Y reaction was explored using SrCl₂/SrO targets of natural isotopic abundance. With 26→20 MeV protons, the yield and production rate are 12 GBq·C⁻¹ and 0.67 GBq·h⁻¹ respectively. Yield and radionuclidic purity compare quite well with those reported for other ⁸⁷Y production routes.The generator filling consists of poly(tetrafluoroethylene) granules coated with di(2-ethylhexyl)phosphoric acid and is loaded with the target dissolved in HCl. The elution efficiency is >85% in 5 mL 0.1 M HCl eluant, with a ⁸⁷Y breakthrough of <10^−30/0.     

Excitation functions of Se(d,xn)Br reactions: Comparative evaluation of possible routes for the production of Br at a small cyclotron

Excitation functions were measured for the first time for ⁷⁴Se(d,n)⁷⁵Br and ⁷⁴Se(d,2n)^74mBr reactions from threshold to 23 MeV. Use was made of the stacked-foil technique, and thin samples were prepared by electrolytic deposition of 31.4% enriched ⁷⁴Se on Al-backing. Differential and integral yields of ^74mBr and ⁷⁵Br were calculated from the measured excitation functions. The optimum energy range for the production of ⁷⁵Br via the ⁷⁴Se(d,n)-process was found to be E_d = 12 → 8 MeV, with ⁷⁵Br-yield amounting to 509 MBq (13.75 mCi)/μAh and the ^74mBr impurity to 78Kr(p,)⁷⁵Br and ⁷⁴Se(d,n)⁷⁵Br, suggested for the production of ⁷⁵Br at a small cyclotron is given. The (d,n) reaction gives higher yield than the (p,) process and is preferable at cyclotrons with E_d 10 MeV. In general, at a small cyclotron the achievable batch yields of ⁷⁵Br via both the processes are limited.     

New measurements and evaluation of excitation functions for (p,xn), (p,pxn) and (p,2pxn) reactions on 133Cs up to 70 MeV proton energy

Cross sections for production of the therapeutic radioisotope ¹³¹Cs via the ¹³³Cs(p,3n)¹³¹Ba→¹³¹Cs route were investigated at cyclotrons. Excitation functions of the ¹³³Cs(p,x)^{133m,133mg,131mg,129g,129m,128}Ba, ^{132,129cum,127cum}Cs and ^{129m(ind),127cum,125cum}Xe nuclear reactions were measured up to 70 MeV proton energy. The experimental data were compared to the results of model calculations performed by means of ALICE-IPPE, EMPIRE-II and TALYS computer codes. Good overall agreement was observed. On the basis of the measured excitation functions integral yields were deduced. Charged particle production routes of ¹³¹Cs are discussed.     

Excitation functions of (p,x) reactions on natural nickel between proton energies of 2.7 and 27.5 MeV.

Excitation functions have been measured for a number of proton induced nuclear reactions on natural nickel in the energy range from 27.5 MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions for the reactions leading to the formation of (60)Cu, (61)Cu, (56)Ni, (57)Ni, (55)Co, (56)Co, (57)Co and (58)Co are presented and compared with earlier reported experimental data. Comparison with the recommended data reported by the International Atomic Energy Agency [Gul et al., 2001. Charged particle cross section database for medical radioisotope production. IAEA-TECDOC-1211, IAEA Vienna, Austria] is also presented when possible.     

Excitation functions of natZn(p,x) nuclear reactions with proton beam energy below 18 MeV

We measured the excitation functions of ^natZn (p,x) reactions up to 17.6 MeV, using the stacked-foils activation technique. High-purity natural zinc (and copper) foils were irradiated with proton beams generated by an 18 MeV isochronous cyclotron. Activated foils were measured using high-purity Ge gamma spectroscopy to quantify the radionuclides ⁶¹Cu, ⁶⁶Ga, ⁶⁷Ga, and ⁶⁵Zn produced from the reactions. Thick-target integral yields were also deduced from the measured excitation functions of the produced radioisotopes. These results were compared with the published literature and were found to be in good agreement with most reports, particularly those most recently compiled.     

Production of 89Zr via the 89Y(p,n)89Zr reaction in aqueous solution: Effect of solution composition on in-target chemistry

ObjectiveThe existing solid target production method of radiometals requires high capital and operational expenditures, which limit the production of radiometals to the small fraction of cyclotron facilities that are equipped with solid target systems. Our objective is to develop a robust solution target method, which can be applicable to a wide array of radiometals and would be simply and easily adopted by existing cyclotron facilities for the routine production of radiometals.MethodWe have developed a simplified, solution target approach for production of ⁸⁹Zr using a niobium target by 14 MeV energy proton bombardment of aqueous solutions of yttrium salts via the ⁸⁹Y(p,n)⁸⁹Zr nuclear reaction. The production conditions were optimized, following a detailed mechanistic study of the gas evolution.ResultsAlthough the solution target approach avoided the expense and complication of solid target processing, rapid radiolytic formation of gases in the target represents a major impediment in the success of solution target. To address this challenge we performed a systematic mechanistic study of gas evolution. Gas evolution was found to be predominantly due to decomposition of water to molecular hydrogen and oxygen. The rate of gas evolutions varied > 40-fold depending on solution composition even under the same irradiation condition. With chloride salts, the rate of gas evolution increased in the order rank Na < Ca < Y. However, the trend was reversed with the corresponding nitrate salts, and further addition of nitric acid to the irradiating solution minimized gas evolution. At optimized condition, ⁸⁹Zr was produced in moderate yield (4.36 ± 0.48 MBq/μA_•h) and high effective specific activity (464 ± 215 MBq/μg) using the solution target approach (2.75 M yttrium nitrate, 1.5 N HNO₃, 2 h irradiation at 20 μA).ConclusionThe novel findings on substrate dependent, radiation-induced water decomposition provide fundamental data for the development and optimization of conditions for solution targets. The developed methodology of irradiation of nitrate salts in dilute nitric acid solutions can be translated to the production of a wide array of radiometals like ⁶⁴Cu, ⁶⁸Ga and ⁸⁶Y, and is well suited for short-lived isotopes.     

Excitation functions for the production of some radioisotopes of Cs, Xe and I in proton bombardment of Xe up to 100 MeV

Integral excitation functions for the production of 16 radioisotopes of Cs, Xe and I in the bombardment of ^natXe with protons were measured up to 100 MeV. The results were compared with geometry-dependent hybrid-model calculations performed by means of the computer code ALICE/85/300, employing both the standard methods offered by the code to take nucleon pairing and shell-structure effects into account. Good overall agreement was obtained in both cases.     

Excitation functions for the production of 109Cd, 109In and 109Sn in proton bombardment of indium up to 200 MeV

Effective cross-sections for the production of ¹⁰⁹Cd as well as its precursors in the bombardment of ^natIn with protons were measured from threshold to 200 MeV. A thick-target production-rate curve for ¹⁰⁹Cd, based on its measured integral excitation function, was derived. The measured practical production rate at ∼100 MeV, 10 μA was found to be in good agreement with it. The experimental results were well reproduced by theoretical model calculations, the results of which were consequently used to predict thick-target production rates for a 100% enriched ¹¹³In target also. Both production routes offer substantially higher yields than the commonly-used ones employing Ag targets.     

Excitation functions and production rates of relevance to the production of 111In by proton bombardment of natCd and natIn up to 100 MeV

Excitation functions were measured from threshold up to 100 MeV for the production of ¹¹¹In and ¹¹¹Sn, as well as of each of their main radioisotopic contaminants, in the proton bombardment of ^natCd and ^natIn, respectively. Thick-target production-rate curves, based on the measured excitation functions, were derived in each case. The results are discussed in terms of expected yields and contamination levels of ¹¹¹In produced under various conditions via the ^natCd(p, xn)¹¹¹In and ^natIn(p, xn)¹¹¹Sn→¹¹¹In production routes. The experimental excitation functions obtained were also compared with theoretical calculations performed with the computer code ALICE/85/300, and excellent agreement was obtained.     

Yield and purity of 82Sr produced via the natRb(p,xn)82Sr process

The recently reported cross-section data for the production of ⁸²Sr via the ^natRb(p,xn)⁸²Sr process were evaluated. For the ^natRb(p,xn)⁸⁵Sr process, cross-sections were measured experimentally over the proton energy range of 25–45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of ⁸⁵Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide ⁸²Sr and the impurity ⁸⁵Sr were calculated. Yields were also determined experimentally over several energy ranges using thick ^natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of ⁸²Sr, an incident proton energy of 60 MeV or above is recommended; the ⁸⁵Sr impurity then corresponds to <20%.     

Cyclotron production of high-purity 123I I. A revision of excitation functions,thin-target and cumulative yields for 127I(p,xn) reactions

Excitation functions, thin-target and cumulative yields for the proton-induced reactions on ¹²⁷I targets were measured in the 67.5- to 5.3-MeV energy region. These results were used primarily to define the proton-energy ranges and target thicknesses to optimize radionuclide yields and purities for ¹²³I production from its 2.08-h ¹²³Xe parent. Other reactions producing radioxenons of interest in nuclear medicine (i.e. 36.406-d ¹²⁷Xe, 17.3-h ¹²⁵Xe, 20.1-h ¹²²Xe, and 38.85-min ¹²¹Xe), were also measured. These results are compared to other previously reported values.     

Thin-target excitation functions, cross-sections and optimised thick-target yields for natMo(p,xn)(94g ,95m,95g,96(m + g))Tc nuclear reactions induced by protons from threshold up to 44 MeV. No Carrier Added radiochemical separation and quality control.

This work describes the method adopted in our laboratories, to produce 94gTc, 95gTc, 95mTc and 96gTc radionuclides via proton-cyclotron irradiation on molybdenum targets of natural isotopic composition. A new set of experimental thin-target excitation functions and "effective" cross-sections for direct natMo(p,xn)(A)Tc [with A = 94, 95, 95, 96] nuclear reactions, with incident proton energy in the range from threshold up to 44 MeV is presented. Some definitions of the equations used and nuclear data traceability are reported. Thick-target yield values were calculated and optimised, by numerical fitting and integration of the measured excitation functions. These values allow optimisation of production yield of one radionuclide, minimising at the same time the yield of the others. Radiochemical separation on NCA technetium radionuclides from both molybdenum target and niobium, zirconium and yttrium radioactive by-products is reported. Quality control tests of the radiotracers were developed for the applications envisaged in environmental metallo-biochemical toxicology.     

Excitation functions and yields of relevance to the production of 67Ga by proton bombardment of natZn and natGe up to 100 MeV

Excitation functions were measured from threshold up to 100 MeV for the production of ⁶⁷Ga and its main radiogallium contaminants in the proton bombardment of ^natZn as well as ^natGe. From these, thick-target production-rate curves were derived in each case. The results are discussed in terms of expected yield curves of ⁶⁷Ga suitable for medical use (99% as well as 99.9% radionuclidically pure), obtained by allowing an appropriate period after EOB for its (shorter-lived) radiogallium contaminants to decay before its radiochemical separation. Theoretical calculations performed with the computer code ALICE/85/300 were also compared with the measured excitation functions, and reasonably good agreement was obtained.