Experimental studies on the proton-induced activation reactions of molybdenum in the energy range 22–67MeV

Proton therapy range verification method via delayed γ-ray spectroscopy of a molybdenum tumour marker

In this work, a new method of range verification for proton therapy (PT) is experimentally demonstrated for the first time. If a metal marker is implanted near the tumour site, its response to proton activation will result in the emission of characteristic γ rays. The relative intensity of γ rays originating from competing fusion-evaporation reaction channels provides a unique signature of the average proton energy at the marker, and by extension the beam's range, in vivo and in real time. The clinical feasibility of this method was investigated at the PT facility at TRIUMF with a proof-of-principle experiment which irradiated a naturally-abundant molybdenum foil at various proton beam energies. Delayed characteristic γ rays were measured with two Compton-shielded LaBr₃ scintillators. The technique was successfully demonstrated by relating the relative intensity of two γ-ray peaks to the energy of the beam at the Mo target, opening the door to future clinical applications where the range of the beam can be verified in real time.

Enhanced production of 99Mo in inverse kinematics heavy ion reactions

The reaction of a 100Mo beam at 12 MeV/nucleon impinging on a 4He gas-cell target was performed. The 99Mo alongside other coproduced isotopes were collected after the gas target on an aluminum catcher foil and their respective radioactivities were measured by offline γ-ray analysis. In this contribution, preliminary experimental results which are used to discuss the possibility of optimal large-scale production conditions of the produced radioisotopes are presented.

Computational simulation of natUO2, 232ThO2 and U3O8-Al pills to estimate (p,fission) 99Mo yield in the modeled targets irradiated by CYCLONE30 accelerator

⁹⁹Mo is important for both therapy and imaging purposes. Accelerator and reactor-based procedures are applied to produce it. Newly proton-fission method has been taken in attention by some research centers. In the present work, computationally investigation of the ⁹⁹Mo yield in different fissionable targets irradiated by proton was aimed. The results showed UO₂ pill target could be efficiently used to produce 11.12Ci/g-U saturation yield of ⁹⁹Mo using 25MeV proton irradiation of the optimized-dimension target with 70µA current.

Computational investigation of ⁹⁹Mo production yield via proton irradiation of natU and ²³²Th targets

Accelerators have some advantages such as safety and cheaper operating and decommissioning costs for (99)Mo production. Yield theoretical calculation using computational codes can powerfully estimate usefulness of a proposed nuclear reaction for a routine manufacturing. In this work, Monte Carlo-based code was used to compute (99)Mo yield in (232)Th and (nat)U proton-irradiated targets, as well as maximum applicable beam current. Results showed that the code well agrees with published experimental data. The targets can bear maximum beam current of 30 µA. Targets from (232)Th provides higher (99)Mo yield.

Evaluation ofMo99andTc99mProductions Based on a High-Performance Cyclotron

Following preliminary feasibility studies which started at Legnaro National Laboratories (LNL) in 2011, the Italian National Institute for Nuclear Physics (INFN) research activities are underway aiming at the alternative, accelerator-driven,Mo99/Tc99mproduction routes. One of the most promising approaches is to use100Mo-enriched (i.e., >99%) molybdenum metallic targets, bombarded with high-beam-current, high-energy proton cyclotrons. In order to get a comprehensive map of radionuclides expected, a detailed theoretical investigation has been carried out using the TALYS-TENDL 2012 excitation functions extended up to (p,6n), (p,p5n), and (p,2p4n) levels. A series of quality parameters have thus been calculated both at the end of beam (EOB) and at longer times. Results point out that accelerator-99Mo is of limited interest for a possible massive production because of the quite low specific activity with respect to reactor-99Mo. Accelerator-Tc99mquality parameters (i.e., radionuclidic purity (RNP), isotopic purity (IP), and specific activities) calculated are instead quite close to the generator-Tc. Calculations at 15, 20, and 25 MeV have thus been performed to assess the best operative irradiation condition forTc99mproduction while minimizing both the short-lived and long-lived Tc contaminant radionuclides. Although present in minimum quantities, Tc contaminants may indeed have an impact either on the pharmaceutical labeling procedures or on contributing to patient radiation dose during the diagnostic procedures.

Recent developments in nuclear data measurements and chemical separation methods in accelerator production of astatine and technetium radionuclides

The cyclotron produced neutron deficient technetium radionuclides (93Tc,94(m+g)Tc,95Tc,96Tc) have gained renewed interest in various fields, including nuclear imaging, provided they can be obtained in a pure form. Similarly,211At due to its moderate half-life and high intensityα-particle energy (both from211At as well as its transient decay product211Po) is of prime interest in targeted therapy. Another interest is to study the astatine chemistry, which is least studied compared to other halogens due to its non-occurrence in natural systems. For maximum production of these radionuclides various parameters need to be standardized. A chemical separation is required to achieve high radiochemical purity beforein-vivoapplication. This review describes various production routes of neutron deficient astatine and technetium radionuclides that have been reported after the year 2000. The analytical chemistry developed for separation of no-carrier-added (nca) Tc and At radionuclides in the same period is also discussed in detail.

Activation cross-section measurements of some proton induced reactions on Ni, Co and Mo for proton activation analysis (PAA) purposes

The experimental proton induced reaction cross sections on some elements of the Havar alloy were measured using the activation method and the well established stacked-foil technique combined with high resolution gamma-ray spectroscopy. They included the reactions natNi(p,x)57Ni, natCo(p,x)58(m+g)Co and natMo(p,x)94g,95g,96(m+g)Tc, the aim being to obtain reliable data in the proton energy range up to 26 MeV for some important reactions to be used in the proton activation analysis of steel or other alloys. Irradiations were performed using the CS-30 Cyclotron at KFSH and RC, Riyadh, Saudi Arabia. The activity measurements were carried out in PNU laboratories, Riyadh, Saudi Arabia. The experimental excitation functions for the investigated reactions were constructed and compared with the performed computed theoretical nuclear model calculations using two different codes: ALICE-IPPE and TALYS. A comparison between our measured cross-section values and the available published data is also presented, with a view to checking the consistency of the reported experimental work from various laboratories.

Separation of no-carrier-added (93,94,94m,95,96)Tc from (7)Li induced natural Zr target by liquid-liquid extraction

Charged particle activation was carried out on (nat)Zr foil by 42.5MeV (7)Li beam to produce (93,94,94m,95,96)Tc radionuclides. No-carrier-added (nca) technetium radionuclides were separated from co-produced (90,96)Nb and bulk Zr employing liquid-liquid extraction with the help of anion exchanger trioctylamine (TOA) diluted in cyclohexane and HCl. Bulk Zr was monitored by spiking (88,89)Zr produced by 20MeV proton induced reaction on (nat)Y target. The optimum separation was achieved at 0.1M TOA and 0.01M HCl. Technetium radionuclides were recovered from the TOA phase by stripping with 0.1M DTPA (diethylene triamine pentaacetic acid) dissolved in NaOH.

Production and separation of no-carrier-added93,94,95Tc from9Be activated yttrium target

Proton rich Tc radionuclides have been produced for the first time through89Y(9Be,xn)93,94,95Tc reactions. In order to optimize the yield of a particular radionuclide of choice, batch yield of93Tc,94Tc and95Tc have been measured at different incident energies using stacked-foil technique followed by off-line γ-spectrometry. No-carrier-added (nca)93,94,95Tc radionuclides have been separated from bulk yttrium by liquid–liquid extraction (LLX) and solid–liquid extraction (SLX) techniques. Trioctylamine (TOA) diluted in cyclohexane was used as liquid anion exchanger in LLX in presence of HCl. SLX was carried out using cation and anion exchanger resin, DOWEX-50 and DOWEX-1, respectively, in HCl medium.

Experimental determination of deuteron-induced activation cross sections of yttrium

Excitation functions were measured for the89Y(d,x)90m,88,87m,87m+gY,89Y(d,x)88,89Zr and89Y(d,x)85Sr reactions in the energy range 9–40 MeV by the stacked-foil activation technique in combination with high resolution HPGe γ-ray spectroscopy. The data above 27 MeV have been measured for the first time. Yield calculations revealed that in the deuteron-induced activation of yttrium the direct production of88Y is about two times lower than that of88Zr. The maximum cross section for the production of the PET isotope89Zr by the Y+dprocess is higher than by Y+p. The yields and decay characteristics of the88Y and88Zr nuclides are suitable for thin layer activation (TLA) analysis.

Experimental studies of the deuteron-induced activation cross-sections on natAg

Excitation functions were measured for the (nat)Ag(d,x)(105,106m,110m)Ag, (nat)Ag(d,x)(107,109)Cd and (27)Al(d,x)(24)Na reactions by the stacked-foil activation technique and high-resolution gamma-spectroscopy over the energy range 0.44-40 MeV. The thick target integral yields were deduced using the measured cross-sections. No experimental data on the (nat)Ag+d process are available in the literature above 27 MeV. The nuclides (105)Ag, (106m)Ag and (109)Cd produced with deuteron induced activation of natural silver have suitable yields and decay characteristics important for thin layer activation (TLA) analysis. The cross-section for the production of (107)Cd and (109)Cd is significantly large. Therefore, the Ag+d process can be an efficient route for the production of isotope with a medium energy accelerator. The results of the model calculation using the TALYS code are not consistent with the present data. A large shift in the incident energy is found in TALYS calculations.

Experimental studies on excitation functions of the proton-induced activation reactions on yttrium

Proton-induced activation cross-sections were measured for the (89)Y(p,x)(89,88,86)Zr, (89)Y(p,x)(88,87,87 m,86)Y, (89)Y(p,x)(85,83,82)Sr and (89)Y(p,x)(84,83)Rb reactions by a stacked foil technique in the energy range 15-80 MeV which was covered by two separate measurements for 15-50 and 32-80 MeV energy range with 50 and 80 MeV incident protons. The differences between the results of two irradiations were found within 6% in the overlapping energy regions. The production yields for the long-lived products like (88)Zr, and (88)Y are significantly larger than that of (nat)Mo+p, (nat)Nb+p and (nat)Zr+p processes. The productions of the medical isotopes, (85)Sr and (83)Sr are also effective by Y+p process using an 80 MeV beam. Thick target integral yields were also deduced using the measured cross-sections. The (87)Y, (88)Y, (88)Zr and (89)Zr radionuclides have suitable yields and decay characteristics important for thin-layer activation (TLA) analysis.

Experimental studies on excitation functions of the proton-induced activation reactions on silver

Excitation functions were measured for the production of 106m,105Ag, 103,101,100Pd, 105,102,101m,100,99Rh and 97Ru via proton-induced activation reactions on natural silver using a stacked foil technique in the energy range 11-80 MeV. The residual activity measurements were carried out nondestructively by the high-resolution HPGe gamma-ray spectroscopy. Thick target integral yields were deduced using the measured cross-sections from the respective threshold energies of the investigated reactions up to 80 MeV. The present work gives new results for the investigated radionuclides. The data in MENDL-2P deduced with the theoretical model code ALICE-IPPE are consistent in shape with the measured values, but show disagreement in magnitude.