Guidelines for the preparation and isolation of Radionuclides produced with In-house cyclotrons Bombardments

Carrier-free radioisotopes and cyclotrons are largely manufactured and sold in market in high prices, even many challenges are facing isotopes production in industry. Thus, we came here to introduce valuable and easy working conditions using different thick target materials under well-defined irradiations to separate some important isotopes. As a result, in carrier-free form, the present work has successfully isolated seventeen most common cosmogenic and biological radioisotopes recommended by the IAEA-TECDOC-1211, Charged Particle Cross-section Database for Medical Radioisotope Production: Diagnostic Radioisotopes and Monitor Reactions, and the IAEA, in addition to US National Nuclear Data Center (NNDC) databases.

Introduction

In November, 2005, the United States Atomic Energy Commission (USAEC) has launched a novel programme [1,2], to enhance the needs for developing cyclotron-generated and reactor-produced radionuclides (i.e. Tc-99 m, I-123, I-124, Zr-89, Cu-64, Ga-67, Ga-68, In-111, Y-86 and Sc-44) (or called as reactor-produced radioactive isotopes (RPRI); energy range 3 MeV-20 MeV) distribution including their marketing process especially for medical applications [3,4]. In 5yrs, the programme was being in process, which perceived the work on radiopharmaceuticals. cyclotron producing radioisotopes had been largely expanded especially in clinical application [3]. Even though, as noted by USAEC, it was not marketed as the nuclear RPRI, which nowadays plays a foremost active role in scientific research, and recent developments in several arenas especially “molecular biology” [5,6]. The challenge that brakes the distribution of this important technique attributes to the imbalance between the expenditures and the gained products, where to produce a little quantity of radioactivity by the expensive charged particle accelerator (CPA), this entails high expenses. Taking into consideration this challenge, the cyclotron produced carrier free radioisotopes (CFSR) can overcome these obstacles and presents its assets as desirable technique in major fields [5].

A carrier free isotope or CFSR has been considered the only technique that needs no quantifiable masses of stable isotopic elements of the same component present [7]. Through charged particle radioactivity, the carrier free isotopic elements are generated where their atomic numbers (Z) (or the chemical identity) are different from Z-values of the original target substance/material (TM) [8]. With the usage of distinct chemical separation systems, such as solvent extraction and/or ion exchange chromatography (IEC), macro extent of TM can be separated from the tiny quantity of radioactive material then decontaminated and organised as per CFSR [9,10]. CFSR may be implemented in several ways. These could be inoculated into humans and animals due to the insignificant chemical tolerance, i.e. As⁷⁴ [11]. These could be utilised for radiochemical investigations in very little contents, (< 0.01µmolar). They can also be implemented for preparing of insubstantial lightweight-counting standards, abolishing the amendments aimed at scattering and self-absorption correction [12].

Basic principles of CPAs yield radioisotopes that generally are neutron-deficient nuclei regarding the nuclear-powered stable line, and that falling-off through positron discharge or even electron seizure [13,14].

RPRI designed by neutron capture are too much neutron, falling-off thru β-particle emission [15]. For a particular element, the rate of radioisotopes’ half-lives is commonly dissimilar. Therefore, by various applications, the selection of radioisotopes of a certain element, of varied properties of radioactivity is accessible. As an example, the shorter-lived isotopic nuclide of 65-d Sr⁸⁵, flexible to an appropriate system of scintillation counting feature, is utilised with noxious fission isotopic product (~30-yr Sr⁹⁰), that only decays via β-particles radiation (β⁻ and β⁺). So that, Sr⁹⁰ decays (100% of the time with E_{β, max} = 546 KeV) to Y⁹⁰ then the later decays to the stable isotope Zr⁹⁰ (~64-hr) by also β-emission. Hence, after approximately 7x64 hrs (18.67 d), the Sr⁹⁰ and Y⁹⁰ are reached secular equilibrium and decay at the same rate. The longer-lived radionuclide of 2.6-yrs Na²² or even 105-d Y⁸⁸ can be utilised in operations implement certain isotopes of awfully short half-lives as 64-hr Y⁹⁰ or even 15-hr Na²⁴. cyclotron irradiation may frequently generate radionuclides with no association of other radioactive isotopes of an identical element, that in other way is only gained by the reactor irradiation of electromagnetically enriched isotopes [16]. Electromagnetic source equipment for this type of separation is usually made up of functional subunits, so arranged that any component that fails in service can be removed and replaced by remote control without the necessity for complete chemical and mechanical servicing of the entire unit. It has also been suggested that the receiver be designed so that individual collectors can be readily handled through recovery chemistry. Remote handling of all systems behind suitable barriers appears to be practical. Wash chemistry and recovery chemistry would be handled in areas isolated from operational and servicing areas [17]. As an illustration, 3-yr Fe⁵⁵ may arranged with no 45-d Fe⁵⁹. Lastly, the fraction of elements which does not hold practical radioisotopes is completed with nuclear reactor irradiation. They comprise Al, Ti, and V. Exclusively, cyclotron irradiations have been designed at developing ~10⁶-yr Al²⁶, 3.08-hr Ti⁴⁵ and 16.2-d V⁴⁸.

The commencement of a database for the invention and circulation of cyclotron fashioned CFSR asked for the growth of a number of actions which had not been beforehand described including the overviews of the amendments into published trials [11,18] and which were not utterly acceptable for the envisioned practice as of short chemical yield or a deficient product purity. Moreover, the fairly scant data of cyclotron have also posed another challenge for the current study.

Materials and Methods

The chemical procedures were operated in Pyrex glassware excluding sodium isotope (Na²²) and when employing hydrofluoric acid (HF). However, to get minimal exchange medium of Na²² along with the sodium exists in the silicate glass, Vycor containers (96% SiO₂ and 4% B₂O₃) were utilised. Polyethylene (PE, (C₂H₄)_n) and alternatively HF-inert materials have been implemented to capacitate HF solutions.

The measures are designed for radiochemical separations of such elements wherefore artificial-shaped radionuclides have been detected. Yet, the realised separations encompass the supplementation of labile isotopic ratios of matching element as carriers, has achieved reference chemical procedures with sub-µg amounts of radioactive classes pursued. Meanwhile, carrier-free radioisotopes can be favourite products and those techniques of separation are commonly unfitting. The separation measures for the sub-µg extents of isotopes ought to be considered with the available instruments which are typically mass-independent, alike to coprecipitation along with solvent extraction, IEC, and non-isotopic carriers. The actions, given in this paper, were settled from these practices. In addition, every so often, hypothetical yield assessment is the only information offered. A comparison study has been carried out with previous published works, which were utilised as virtual references in scheduling irradiations. With 8MeV protons, deuterons of 15MeV energy, and with protons of 15 and 20MeV energies, the radioactivity for the manufacture of the CFSR has been investigated in the current article.

Via Ɣ-radiation spectroscopy, the analysis (apart from W¹⁸¹, Cd¹⁰⁹, and Fe⁵⁵) of the isolated activity equipped with a well-formed thallium (Tl)-doped sodium iodide (NaI) modulated with a scintillator system armed with single-channel pulse-height analyser (SCPHA) has been implemented (linearity within 1% of deviation for radiation energy; stability within 1%/24hrs of fluctuation; temperature stability of channel position and width ± 0.002%/°C; deadtime 23 µsec.; resolution 0.08 µsec.) and the spectra taken with SCPHA were in a good agreement with these taken by cathode ray tube (CRTA) analyser (both analyser window widths were set at approximately 500 mV). At one time, the SCPHA used for a pulse height analysis has a lower and an upper level discriminator, and produces an output logic pulse when an input pulse lies between the discriminator levels. All pulses in a specific range are routed to a scalar (counter). The SCPHA was set to a narrow ∆V range and then the lower level discriminator has been swept through a series of voltages using an SCPHA Sweep device. All pulses outside the SCPHA window were lost, so that the smaller the window for better resolution, the longer the time required to get adequate counts. In this experiment, it was not necessary to use multi-channel pulse-height analyser (MCPHA) even it would be suggested to collect the entire spectra at once because SCPHA is a sufficient analyser used in establishing coincidence between nuclear decays which is better than most MCPHAs that are busy themselves in digitizing many uninteresting events increasing the dead time. Besides, SCPHA is much cheaper and simpler in design than MCPHA.

However, for W¹⁸¹, Cd¹⁰⁹, and Fe⁵⁵, which do not possess distinguished energetic Ɣ-rays, end-window variable-geometry proportional flow counters have been utilised. To assess counter effectiveness for the miscellaneous radiations of interest, standard specimens of various isotopes were brought from either the National Bureau of Standards (NBS) or checked analytically with the assistance of external quality control (QC) with other testing laboratories. Considering the unavailability of the standards for specific isotopes, the emerging faced problem in this research, counter efficacies were assessed by adopting a method of interpolation among the obtainable standards. For specific situations of very tiny radiation energy density, that was exigent to roughly estimate the counter effectiveness regarding the physical ordering and assets of the counter electronic parts.

On the whole, analyses can be performed not as much of 10% absolute uncertainty (AU) and the latter term is usually emerged from serious sources related to the thick target yield data arise from such places of origin.

Results and Discussion

In the current programme, the achieved irradiations have provided seventeen dense target yields of radioisotopes (n = 3) (Table 1). We also presented in this table, the incident elements used in irradiation, the target chemical, the yield-dense target adjusted for falls experienced in the chemical operation and falling-off from the time of termination of the irradiation to analysis time. Besides, we extracted the yield-dense target numbers published in the previous studies for matching radioisotope, in addition to the main causes of uncertainties in the yield-dense targets. By hand, the chemical operating of the exposed targets, period and intensity of irradiations, in addition to the radiometric assays of the isolated carrier-free activities have been served to assess the thick target yield data. The yields of activities after chemical isolation and the combined beam streams of the irradiations have been indicated by experimental runs.

In general, the absolute yields reached (≥90%) and the assessed errors were allotted (≤5%.) In limited instances, the yield was hard to measure and the possible absolute error reached higher than 30%. The short-lived isotopic elements were needed for collating the total yield information and the rapid separation. For the aggregated present data, we allotted the probable absolute errors of the order of 5-10%. Under unsealed irradiated settings, the target evaporation was regarded as a probable cause of non-reproducibility of cyclotron-produced of irradiation yields. This was confirmed with Sr⁸⁵ yield, where the irradiations made with rubidium chloride (RbCl) were greater than the anticipated variations. Further radioisotopes of the matching element were formed for certain itemised radioisotopes. Those cases had complicated the analysis, where the segregation of the wanted isotope might not be realised by chemical means. For instance, two bismuth (Bi) radioactive isotopes were interfered with the radiometric analysis of Bi²⁰⁷.

To permit an adequate decay of 6-d Mn⁵² isotope for an Mn⁵⁴ accurate assay, an extensive delay period was necessitated. However, these forms of decaying systems along with the involvement of half-lives have increased the uncertainty levels and added some erratic yield determinations. Based on the routine analyses, the chemical isolation methods have successfully been performed and their results are discussed below. But actually, those methods were based on certain procedures used suitable techniques for CFSR as coprecipitation (CPT) along with IEC, non-isotopic carrier, or solvent extraction, or could be an integration of them.

We had registered an incomplete decontamination and some meagre yields as results of great deviations from the specified conditions, actually attributed to the reagent concentrations and volumes. Even though, the produced isotopes attained were ostensibly carrier-free, e.g. no non-energetic atoms are purposefully supplemented, roughly inactivated substance remains unvaryingly existing. The origins of the uncleanness are attributed to the reagents employed in the segregation and the contaminations in TM. Therefore, we suggest careful selection of reagents used and active purification of the TM, in order to practically get carrier-free products.

Summary-perspectives in tentative nuclear experiences

From our successful experience in this research, we suggest the following practices for carrier-free separation for radioisotopes (CFSR), depending on the type of isotope.

I. Be⁷. TM: lithium (Li).

Product (Prod.): 99 + %Be⁷, in hydrochloride acid (HCl) or nitric acid (HNO₃).

Production reactions (Prod. Reac.): Li⁷ (p,n) Be⁷ or Li⁷ (d,2n) Be⁷.

Other important reactions (OIR): None.

Chemical separation principles (Chem. Sep. Princ.): Be⁷ is persisted on ferric hydroxide (Fe(OH)₃). After that, Iron (Fe^III) is detached by IEC.

Recovery (Rec.) obtained (98%); Time required (TR): nearly 4 hrs.

The Li metal, about 10g, is etched from its Cu with the assistance of 0.02N HCl. After acidification of the ensuing solution with HCl, any precipitates exist are separated by filtration. Then, 30mg of Fe^III carrier are supplemented, and the solution is just kept ammoniac. After 1hr of digestion, the Fe(OH)₃ has been segregated by separation through Whatman^TM cellulose paper (Grade 42). Be⁷ activity has quantifiably reserved in the solid phase. The latter phase is desolated in a minimum volume of HCl and then reprecipitated with ammonium hydroxide (NH₄OH). After 1hr digestion, the precipitate has isolated by centrifuge and washed two-times with water, and re-desolated in 5ml (12N HCl).

II. The anion exchange resin Amberlite IRA-400 is proved as an effective and reusable catalyst, thus, this column has been prepared and conditioned with 12N HCl. The solution is gone across this column, the Fe being retained and the Be⁷ transverses over. The column is rinsed thrice using 12N HCl. To break down the organic matter (OM), the whole eluate has evaporated to near dryness and dealt with HNO₃ solution. As if wanted, Be⁷ is transformed to chloride form by recurrent evaporation with HClNa²². TM: magnesium (Mg).

Prod.: 99 + %Na²², in HCl or HNO₃ solution.

Prod. Reac.: Mg²⁴ (d,α) Na²².

OIR: Mg²⁵ (d,n) Al²⁶; Mg²⁶ (d,2n) Al²⁶.

Chem. Sep. Princ.: Al²⁶ is taken off by carrying on beryllium hydroxide (Be(OH)₂). The majority of Mg is removed through the precipitation with ammonia (NH₃). Remaining Mg has done away with IEC.

Rec.: 96%; TR: ~ 12hrs.

The Mg cup target is floated on 50ml of water in a Vycor beaker. Minor volumes of HCl are supplied pending an activity utterly abolished. Approximately 10g of Mg are desolated, 25ml of HCl added and the solution watered down to 200ml. Sequentially, precipitates are separated by filtration.

To regain Al²⁶, 25mg of Be carrier are added then with NH₄OH the solution fetched to a methyl red endpoint. After cooling to room temperature, the Beryllium hydroxide (Be(OH)₂) is detached by centrifugation, washed two-times with water, and kept back to recover Al²⁶

The supernatant solution is condensed by the evaporation to 100ml and saturated with NH₃ gas in ice bath. Magnesium hydroxide (Mg(OH)₂) precipitate is separated by filtration, with suction across a fritted glass funnel. The precipitate is suspended in the funnel thrice with NH₄OH and dehydrated by suction every once. The washes and filtrate are mixed and evaporated to near dryness, 25ml HNO₃ supplemented, and the solution is evaporated to near dryness. The prescribed action is repeated twofold to get rid of ammonium chloride (NH₄Cl) extant. 25ml water is added to the deposit of the last evaporation. If unsolvable material is existed, using filtration, we disposed it.

The sulfonic acid ion-exchange resin (Dowex-50) column is conditioned with 2N NH₄OH until the effluent reaches a pH of 9. At a rate of about 0.3ml.min^-1.cm^-2, the solution is passed over the column. The column is washed with 200ml of water then with 0.35N HCl, the Na²² is eluted. In a Vycor beaker, the eluate is evaporated near to dryness and NH₄Cl is yet once more eliminated with HNO₃. Furthermore, with the later acid the OM is further vanished and if wanted, Na²² can be prepared carrier free in HCl solution by recurrent evaporations using HCl.

For especial situations, when inactive Na is recognised in existence with Mg target, or where a definite activity of the command of 10c/g is satisfactory, the practice could be condensed to a certain degree. If 1mg of Na is existing, the overall purification step could be affected by the precipitation of sodium magnesium uranyl acetate. Uranium (U) is precipitated with NH₄OH and the remaining Mg is then getting rid of by CEC as outlined above. Al²⁶ can be recovered by one of the following methods [42,43].

III. V⁴⁸. TM: TiO₂.

Prod.: 98 + %V⁴⁸ + V49 in HNO₃ or HCl solution.

Prod. Reac.: Ti⁴⁷ (d,n) V⁴⁸; Ti⁴⁸ (d,2n) V⁴⁸; Ti⁴⁸ ( d,n) V⁴⁹; Ti⁴⁹ ( d,2n) V⁴⁹.

OIR: Ti⁴⁸ (d,α,) Sc⁴⁴; Ti⁴⁸ (d,α,) Sc⁴⁶; Ti⁴⁹ (d,α,) Sc⁴⁷; Ti⁴⁸ (d,αp) Ca⁴⁵; Ti⁴⁶ ( d,n) V⁴⁷; Ti⁴⁷ (d,2n) V⁴⁷.

Chem. Sep. Princ.: A sodium carbonate (Na₂CO₃) – sodium nitrate (NaNO3) fusion of the dissolute target leads to unsolvable titanium dioxide (TiO₂) and a solvable vanadate material (i.e. trioxovanadate VO₃-, tetraoxovanadate VO₄-, decavanadate V₁₀O₂₈^-6). Calcium (Ca) and scandium (Sc) are co-deposited with ferrous hydroxide (Fe(OH)₂) from high concentration of caustic NaOH solution. V in a form of vanadyl ion or oxovanadium(IV) cation, VO₂+, is persisted in Fe(OH)₃ along with adjusting pH conditions. Fe is eliminated via IEC.

Rec.: ~90%; TR: ~6 hrs.

To a fine powder, the target, nearly 5g of TiO₂ is pulverised and deposited in a Ni-crucible. 0.2g NaNO3 and 10g Na2CO3 are supplemented and the solids are blended in a thorough manner.

For 45min and at 700°C, the blend is fused. The melt is cooled off, pulverised, and drained away with cold water to secure complete V-dissolution. Using evaporation technique, the bulk of the solution is condensed to 100ml then l0mg Fe^III carrier is supplemented, a bonus amount of NaOH has been added to ensure Fe(OH)₃ precipitation. The deposition has performed again and served to get away both Sc and Ca. After Fe(OH)₃ removal by centrifugation, the solution is acidulated and heated to thrust carbon dioxide (CO₂) out. 10g of Fe^III carrier are added and the pH is cautiously adjusted to 6.2 with NH₄OH. After 30min period of digestion, Fe(OH)₃ is segregated by centrifugation. As vanadyl ion, apparently V is quantitatively reserved by the precipitate, so that, the precipitation is performed more than two times. Besides, in a minimum quantity of 4N HCl, the ending deposition is dissolute and the obtained solution is transverse across an Amberlite IRA-400 column that with 4N HCl is being conditioned.

To eliminate the remaining V-activity from the column, an 4N HCl wash-down has been completed. The eluate is evaporated near to dryness, and dealt in sequence with HNO₃ to get rid of NH₄Cl and to break down OM. By evaporation with HCl, the Cl- solution is resulted. But it would also be perceived that this process does not eliminate aluminium. Besides, the target backing or the container must be Ni.

IV. Mn52 and Mn54. TM: Cr.

Prod.: 98+% Mn⁵²+ Mn⁵⁴, in HCl or HNO₃ solution.

Prod. Reac.: A. deuteron bombardment, Cr⁵² (d,2n) Mn⁵²; Cr⁵³(d,n) Mn⁵⁴; Cr⁵⁴ (d,2n) Mn⁵⁴.

B. proton bombardment, Cr⁵² (p,n) Mn⁵²; Cr⁵³ (p,2n) Mn⁵² ; Cr⁵⁴ (p,n) Mn⁵⁴.

OIR: A. deuteron bombardment, Cr⁵⁰ (d,α) V⁴⁸.

B. proton bombardment, Cr⁵⁰ (p,2p) V⁴⁹.

Chem. Sep. Princ.: Mn⁵² and Mn⁵⁴ are carried on Fe(OH)₃ from NaOH-Br₂ solution.

Cr and V are reserved in the liquid-supernatant layer. To separate from the residual Na, Mn52 and Mn54 are carried on Fe(OH)₃ from NH₄OH, and Fe is separated by IEC.

Rec.: ~95%; TR: ~6hrs.

With HCl, the Cr is etched from its Cu-backing and 10-15g are solvated. 20mg Fe^III are mixed and the solution is evaporated near to dryness. Then, the residue has been solvated in a min. HCl, whereby the volume is adjusted to 25ml. The solution is decanted, blended with cold 7N NaOH (300ml) saturated with liquid Br2. The ensuing Fe(OH)₃ precipitate has quantitatively carried Mn, whereas Cr and V are reserved in the supernate.

On a hot-plate and after 30min of digestion, the precipitate with suction is separated by filtration through a fritted-glass funnel. The precipitate is watered until no colour is distinguished in the washing water, which then solvated in a min. 1N HCl. The deposition (by means of a usage of NaOH-Br₂ solution (150ml)), filtration, and washing are then reiterated thrice. The last deposition substance is solvated in a minimum quantity of HCl, then a surplus volume of NH₄OH is added to deposit Fe(OH)₃. The precipitation is repeated two-times to isolate the activity from residual Na and the ending precipitate is solvated in 4N HCl (5ml).

With 4N HCl, the Amberlite IRA-400 column is conditioned, the solution is passed across the column, and the activity is washed through with 4N HCl. Fe is retained by the column. The elute is evaporated near to dryness and dealt with HNO₃ in order to eliminate OM. If wanted, the Mn⁵² may be obtained in HCl solution by processing a repetitive evaporation with HCl [42,43].

V. Mn⁵⁴ and Co⁵⁶, Co⁵⁷, Co⁵⁸. TM: Fe.

Prod.: 98 + %Mn⁵⁴ and 98 + % pure aggregated Co activity in HCl or HNO₃ solution.

Prod. Reac.: Fe⁵⁶ (d,α) Mn⁵⁴; Fe⁵⁶ (d,2n) Co⁵⁸; Fe⁵⁶ (d,n) Co⁵⁷; Fe⁵⁷ (d,2n) Co⁵⁷; Fe⁵⁷ (d,n) Co⁵⁸; Fe⁵⁸ (d,2n) Co⁵⁸.

OIR: Fe⁵⁴ (d,α) Mn⁵².

Chem. Sep. Princ.: Using ethyl ether ((C₂H₅)₂O), Fe has been extracted. Mn and Co are discriminatorily eluted from an anion exchanger.

Rec.: 98%; TR: ~8hrs.

With HCl, the Fe target is etched until basically all the activity is in solution. About l0g are dissolved. 20mg of cold liquid Br2 are supplied to oxidise the existed Fe to Fe^III. The solution is permitted to stand for 2hrs and after that has evaporated to 40ml. Fe is extracted with (C₂H₅)₂O and with 3- extractions more than 95% of Fe has been removed. The solution is evaporated to almost dryness then 8N HCl (5ml) are added. Using the later acid with the same concentration, Dowex-1 column is conditioned. The solution is passed over the column and by using 8N HCl, the Mn has eluted. 10mg fractions are collated, then checked for activity. Once the Mn is being entirely eluted, the eluant is changed to 4N HCl to eliminate the Co. Similarly, 20mg portions are collated and checked. Fe abides on the column. Mutually, the Mn and Co portions are dealt with HNO₃ to eliminate OM. What’s more, the activity is transformed to the chloride by reiterating the evaporation action with HCl.

VI. Fe⁵⁵. TM: Mn.

Prod.: 99 + % Fe⁵⁵, in HCl or HNO₃ solution.

Prod. Reac.: Mn⁵⁵ (p,n) Fe⁵⁵; or Mn⁵⁵ (p,2n) Fe⁵⁵.

OIR: none.

Chem. Sep. Princ.: Mn is separated by IEC.

Rec.: 99%. TR: ~4hrs.

From its backing, the Mn is etched using HCl. Approximately, 10g are solvated. The resultant solution is condensed by drying to 20ml, then with water has diluted to 40ml. With 4N HCl, the Dowex-1 column is conditioned and then the solution passed across the column. Moreover, Fe is retained and Mn has eluted from the column with 4N HCl. Subsequently, the Fe⁵⁵ has eluted with HCl (0.5N). Near to dryness, the eluate is dried and dealt with HNO₃ to eliminate OM. Notably, the HCl solution is collected by repetitive evaporation of HCl.

VII. Zn⁶⁵. TM: Cu.

Prod.: 99 + %Zn⁶⁵, in HCl or HNO₃ solution.

Prod. Reac.: Cu⁶⁵ (d,2n) Zn⁶⁵; or Cu⁶⁵ (p,n) Zn⁶⁵.

OIR: Cu⁶⁵ (d,α) Ni⁶³; Cu⁶⁵ (d, αp) Co⁶⁰.

Chem. Sep. Princ.: By an anion exchanger in a weak HCl, Zn⁶⁵ is reserved. While the other divalent transition dements are not.

Rec.: 98%; TR: ~5hrs.

VIII. By 1N HNO₃, the activity is etched from the Cu-target. An amount between 5 and 10g are solvated. The ending solution is dewatered to dryness and transformed to chloride by proper evaporation with HCl. The residue has been solvated using a min. 1N HCl that after a full evaporation to dryness. A Dowex-1 column is arranged and with 1N HCl has conditioned. The solution is passed over the column, which is then washed with 1N HCl till Cu cannot be distinguished with H2S addition to the effluent. Co and Ni are not reserved, however then, with 0.5mN HCl, the Zn is eluted. To almost dryness, the solution is dried out and dealt with HNO₃ to eliminate OM. A chloride solution may be gained with HCl evaporations.Ga⁶⁷. TM: Zn.

Prod.: 98 + %Ga⁶⁷, pure aggregated Ga activities in HCl or HNO₃ solution.

Prod. Reac.: Zn⁶⁶ (d,n) Ga⁶⁷; Zn67 (d,2n) Ga⁶⁷.

OIR: Zn⁶⁶ (d,2n) GaSup>66

Chem. Sep. Princ.: Ga is carried on Fe(OH)₃ from NH₄OH solution. Cu is retained in the supernate. Fe is isolated by precipitation from high concentration of KOH solution. K and the remaining Cu are sorted out by IEC.

Rec.: 80 + %; TR: ~6hrs.

About 5g of the Zn target is dissolved in a min. quantity of HCl and the solution is diluted to 100ml. 20mg each of Fe^III and CuII carriers are added. The pH is cautiously maintained at 5.5 with NH₄OH and the solution is permitted to digest for 15min. The precipitate is getting rid of by centrifugation then solvated in HCl. The 2nd precipitation is executed to guarantee a proper isolation from Cu. In a minimum of HCl, the last precipitate is dissolved, the volumetric content is made up at 20ml with water. At that point, an additional quantity of KOH is supplemented. The precipitate is segregated by centrifugation after heating to the boiling point (bp), and the supernate containing the activity as gallate ion (C7H5O5-) is maintained. The precipitate is solvated in HCl and a 2nd precipitation is carried out. The supernates are intermingled, neutralised through HCl addition, then a surplus amount of HCl is added to give a solution 3N in HCl. The solution has gone across a Dowex-1 column and is conditioned with 3N HCl. 3- column volumes of 3N HCl are moved across the column to eliminate K and the remaining Cu. With a 0.2N HCl, the Ga has been eluted. OM is eliminated by evaporation with HNO₃ after heating the solution to the desired degree near to dryness. By evaporating the solution with HCl, the conversion to chloride is affected.

IX. As⁷³, As⁷⁴. TM: Ge.

Prod.: 98 + %As⁷³ + As⁷⁴, in HCl-Cl₂ solution.

Prod. Reac.: Ge⁷² (d,n) As⁷³; Ge⁷³ (d,2n) As⁷³; Ge⁷³ (d,n) As⁷⁴; Ge⁷⁴ (d,2n) As⁷⁴.

OIR: Ge⁷⁰ (d,n) As⁷¹ Ge⁷¹.

Chem. Sep. Princ.: In the existence of Cl₂, Ge is separated from HCl by distillation process. Then, As is distilled out from an HCl-CuCl medium.

Rec.: 90 + %; TR: ~6hrs.

Approximately 5g of the Ge target is aged for 10-15d to let As⁷¹ decaying which is sequentially solvated in aqua regia (Royal water, HNO₃ + 3 HCl). The Cl2 gas has rapidly carried through the solution which is heated to the boiling point two-times. Next to the dilution with 15ml HCl, the solution is moved to a distillation flask that possess a dip tube, which forces the constant gas current to set off from the solution in the period of distillation.

During Cl2 gas passage through the still, Ge has been distilled into a trap comprising 6N NaOH. Along with the HCl supplementations between evaporations, the solution has evaporated several times to reach the drying point. An overall volumetric range of 25-35ml has been distilled.

Subsequently, by adding 5ml of a saturated HCl solution of CuCl to the still and passing HCl gas through the still, As has distilled into an ice-cooled water trap. The distillation is resumed up till activity would not be distinguished in the distillate. The active distillate has dried to the wanted size, though Cl2 gas bubbling into the solution.

X. Sr⁸⁵. TM: RbCl.

Prod.: 99 + %Sr⁸⁵, in HCl or HNO₃ solution.

Prod. Reac.: Rb⁸⁵ (p,n) Sr⁸⁵; or Rb⁸⁵ (d,2n) Sr⁸⁵.

OIR: Rb⁸⁵ (d,α) Kr⁸⁵.

Chem. Sep. Princ.: Sr⁸⁵ has carried on Pb(NO₃)₂ and in the time of sample dissolution Kr⁸⁵ is volatilised. Then, Pb carrier is eliminated as PbS.

Rec.: 98%; TR: 3hrs.

The RbCl, about 5g, is dissolved in water, acidulated, and filtered out. 10mg Pb carrier are added and the solution condensed to 1ml by evaporation. 30mg of fuming HNO₃ are added and the solution cooled down in an ice bath, with infrequent blending.

Pb(NO3)2 which carries the Sr85 quantitatively, is eliminated by centrifugation, dissolved in a minimum volume of water, and reprecipitated. The Pb(NO3)2 is sorted out by centrifugation, and dissolved in water (25ml).

PbS is deposited by saturating the solution with H2S. Sr85 is quantitatively reserved in the supernate. The solution is filtrated out, heated to an evaporation point near to dryness, and the activity solvated in HCl or HNO₃.

XI. Y⁸⁸. TM: strontium oxide (SrO).

Prod.: 98 + %Y⁸⁸, in HCl or HNO₃.

Prod. Reac.: Sr⁸⁸ (p,n) Y⁸⁸.

OIR: Sr⁸⁸ (p,2n) Y⁸⁷.

Chem. Sep. Princ.: Y⁸⁸, is carried on Fe(OH)₃. The Fe^III is eliminated by IEC.

Rec.: 98%; TR: ~4hrs.

The SrO target, about 5g, is dissolved in 0.1N HCl. 10mg of Fe^III carrier are added. CO₃^-2 - free NH₄OH is added until the pH reaches 8.5. The Fe(OH)₃ precipitate, which carries Y88 quantitatively, is segregated by centrifugation. 4- reprecipitations are performed, using a minimum of HCl to dissolve the precipitates. The last precipitate is washed twice with water, then solvated in a minimum quantity of concentrated HCl (6N). The solution is moved across an Amberlite IRA-400 column that has been maintained with 6N HCl. The activity is washed from the column with 6N HCl. Then, the eluate is evaporated near to dryness then dealt with HNO₃ to break OM down. After that, the Y⁸⁸ can be transformed to chloride by heating to dryness with HCl. It should be noted that if Al is present (from backing or container), several Fe(OH)₃ precipitations with high concentrations of NaOH should be performed.

XII. Cd¹⁰⁹. TM: Ag.

Prod.: 98 + %Cd¹⁰⁹, in HCl or HNO₃ solution.

Prod. Reac.: Ag¹⁰⁹ (p,n) Cd¹⁰⁹ or Ag¹⁰⁹ (d,2n) Cd¹⁰⁹.

OIR: Ag¹⁰⁷ (p,n) Cd¹⁰⁷ or Ag¹⁰⁷ (d,2n) Cd¹⁰⁷; Ag¹⁰⁹ (d,α) Pd¹⁰⁷.

Chem. Sep. Princ.: Cd¹⁰⁹ is extracted from a thiocyanate (SCN-) medium into chloroform (CHCl3)-pyridine (C5H5N), back-extracted into 1M HNO₃, and this cycle repeated. Final purification is affected by means of anion exchange.

Rec.: 95%; TR: ~6hrs.

The active portion of the target, about 10g, is dissolved in HNO₃. After evaporating the solution to dryness, 150ml of water are added and any insoluble matter is eliminated by filtration. Solid NH₄CNS is then added until the precipitate which first forms are re-dissolved. The pH is adjusted to 5 with NaCNS, and the solution is transferred to a separatory funnel. The Cd¹⁰⁹ is extracted 3-times with 50ml of CHCl₃ containing 50% of C₅H₅N. The activity is back-extracted into three 25ml portions of 1M HNO₃, which are then evaporated near to dryness. The activity is dissolved, treated, and extracted with CHCl₃- C₅H₅N, as before. After back-extracting into three 25ml portions of 1M HNO₃ and evaporation near to dryness, the activity is solvated in 0.3N HCl (10ml) and passed through a Dowex-1 column which has been washed with water and conditioned with 0.3N HCl. With six column volumes of 0.3N HCl, the column is rinsed, after which the Cd¹⁰⁹ is eluted with 0.3mN HCl. The active eluate is evaporated near to dryness and dealt to break OM down. By evaporation with HCl, Cd¹⁰⁹ may be transformed to chloride.

XIII. In¹¹¹. TM: Cd.

Prod.: 98 + % In activities, in HCl or HNO₃ solution.

Prod. Reac.: Cd¹¹⁰ (d,n) In¹¹¹; Cd¹¹¹ (d,2n) In¹¹¹.

OIR: Cd¹⁰⁸ (d,n) In¹⁰⁹; Cd¹¹⁰ (d,2n) In¹¹⁰; Cd¹¹³ (d,n) In¹¹⁴; Cd¹¹⁴ (d,n) In¹¹⁵; Cd¹¹⁶ (d,2n) In¹¹⁶; Cd¹¹⁶ (d,n) In¹¹⁷.

Chem. Sep. Princ.: In-activities are carried on Fe(OH)₃ from ammoniacal solution. The Fe is extracted with isopropyl ether ((CH₃)₂CHOCH(CH₃)₂).

Rec.: 98%; TR: ~4hrs.

The Cd target metal, about 10g is etched from its backing with HCl. 20mg of Fe^III carrier are inserted, and the solution is neutralised with NH₄OH. 20ml of excess NH₄OH are added. The deposition layer is segregated by centrifugation and solvated in a min. quantity of HCl. After diluting to 15ml with water, the precipitation is repeated. After two additional reprecipitations, 15ml of 8N HCl are added, and the Fe extracted 3-times with (CH₃)₂CHOCH(CH₃)₂. The liquid is evaporated near to dryness. With HNO₃, OM is broken down by repeated evaporations. By evaporation with HCl, the transformation to chloride can be affected.

XIV. Ce¹³⁹. TM: lanthanum oxide (La₂O₃).

Prod.: 98 + %Ce₁₃₉, in HCl or HNO₃ solution.

Prod. Reac.: La¹³⁸ (d,n) Ce¹³⁹; La¹³⁹ (d,2n) Ce¹³⁹ or La¹³⁹ (p,n) Ce¹³⁹.

OIR: none.

Chem. Sep. Princ.: Ce¹³⁹ is extracted into hexone (4-methyl 2-pentanone).

Rec.: 95%; TR: ~2hrs.

The La₂O₃ target, about 3g, has been dissolved in a min. quantity of 3N HCI. 5ml of HNO₃ are added and the solution is dried by evaporation. A blend of conc. HNO₃ (6ml), 2M NaBrO₃ (2ml), and water (2ml) are added, and the resultant solution is thoughtfully heated until a vigorous reaction ensues. The solution is cooled out and moved to a separator funnel comprising of 50ml of hexone which has been conditioned by agitation with 50ml of 9M HNO₃. 1ml of 2M NaBrO3 and 1.5 ml of HNO₃ are inserted. The funnel is instantly agitated, the phases permitted to discrete, and the aqueous layer retained for next retrieval of Ce139. It is highly vital to have bonus amount of NaBrO3 existing during extraction. The hexone layer is rinsed two-times with 9M HNO₃ (10ml) and a few drops of 2M NaBrO₃. The washes are reserved. Ce¹³⁹ is then extracted from the hexone with double quantity of 5ml portions of water comprising 4 drops of H2O₂ (30%). The hexone is castoff into a stream of flowing water. Attention: HNO₃ – hexone is possibly explosive.

The remaining Ce¹³⁹ in the aqueous phase formerly retained has extracted with hexone, and subsequently the aqueous phase is eliminated. The hexone layer is washed with double quantity with 9N HNO₃ and Ce¹³⁹ is eliminated from the hexone with double portions of water (5ml) encompassing 30% H2O₂ (4 drops). The hexone is removed. Since the scattering of Ce¹³⁹ amongst the hexone and 9N HNO₃ washes is nearly to 8:1, it is required to retrieve the Ce¹³⁹ in the 4-rinses. These are aggregated and evaporated till dryness. A blend of conc. HNO₃ (6ml), 2M NaBrO3 (2ml), and water (2ml) is added, and the ending solution heated. The Ce¹³⁹ in the solution is extracted twice with hexone. The hexone layers are each washed two-times with 9M HNO₃ (10ml), and the washes are discarded. The Ce¹³⁹ in the hexone phases is then back-extracted with double 5ml portions of water comprising 30% H₂O₂ (4drops). The later oxide extracts are combined with the first H₂O₂ extracts and are then evaporated near to dryness. OM has broken down with HNO₃. The transformation to chloride can be fulfilled by evaporation with HCl.

XV. W¹⁸¹. TM: tantalum (Ta).

Prod.: 98 + %W¹⁸¹, in HCl-HF.

Prod. Reac.: Ta¹⁸¹ (p,n) W¹⁸¹ or Ta¹⁸¹ (d,2n) W^181M.

OIR: none.

Chem. Sep. Princ.: W¹⁸¹ is isolated apartly from Ta by IEC. The last separation is completed by coprecipitating W¹⁸¹ with Fe(OH)₃ at pH 4. Fe is extracted with (C₂H₅)₂O.

Rec.: 90 +%. TR: ~10hrs.

In a platinum (Pt) dish, the Ta target is etched with HF to eliminate the active layer. Approximate 5g are solvated. After the evaporation near to dryness, HF (4ml) and HCl (20ml) are added, and the blend is heated to get a pure solution. A volume of water (16ml) is added. The solution is passed across a 40cm polyethylene (PE) column containing Dowex-1 which has been conditioned with 1.5N HF + 6N HCI. W¹⁸¹ is eluted with 1.5N HF + 6N HCl. Fractions of 20ml are brought in PE containers. The active fractions are integrated and dried by evaporation to 5ml in a Pt dish. Water (30ml), boric acid (H₃BO₃) (200mg), and Fe^III carrier (10mg) have been supplemented. Adequate 6N NaOH is inserted to reach pH 4.0. The resultant precipitate is segregated by centrifugation and solvated in a min. quantity of conc. HCl. The precipitation is reiterated more than two-times. The ending precipitate is rinsed out two-times with water and solvated in 6N HCl. With (C₂H₅)₂O, Fe has extracted 3-times. The aqueous phase is heated and evaporated near to dryness. By evaporation with HNO₃, the OM is broken down. Whereas, by evaporating with HCl, the transformation to chloride is affected. One droplet of HF is added.

XVI. Bi²⁰⁷. TM: Pb.

Prod.: 98 + %Bi activities, in HNO₃ solution.

Prod. Reac.: Pb²⁰⁷ (p,n) Bi²⁰⁷; Pb²⁰⁸ (p,2n) Bi²⁰⁷.

OIR: Pb²⁰⁶ (p,n) Bi²⁰⁶; Pb²⁰⁷ (p,2n) Bi²⁰⁶.

Chem. Sep. Princ.: The Pb is eliminated by precipitation with fuming HNO₃. Moreover, in the incidence of an extra amount of NaOH, Bi is coprecipitated with Fe(OH)₃. After that, Fe is taken off through the extraction with (C₂H₅)₂O.

Rec.: ~90%; TR: ~6hrs.

Approximately 25g of the Pb target metal, is etched from its backing with 6N HNO₃. The ending slurry is moved to a centrifuge bottle after evaporating to around 50ml, then fuming HNO₃ (100ml) is added. Immediately, the precipitate is eliminated by centrifuge technique after cooling in an ice bath and then rinsed two-times with cold fuming HNO₃. Fe^III carrier (20mg) is added to the aggregate mixture of the supernate and washes, and the solution is evaporated near to dryness. A volume of water (15ml) is added; then 9N NaOH (15ml) is supplemented and the blend agitated. Bi is quantitatively transferred by the Fe(OH)₃, whereas the solvable plumbate (formed by the reaction of lead(IV) oxide, PbO, with alkali) stays in the supernate. The sedimentation is separated by centrifugation and solvated in a min. quantity of conc. HCl. 3-reprecipitations are carried out. The ending precipitate is solvated in 6N HCl (15ml), and with (C₂H₅)₂O, the Fe is extracted 3-times. OM is eliminated by evaporation with HNO₃.

Conclusion

The current study is significant for the producers, processers and distributers of carrier-free radioisotopes and cyclotron-produced. Even though, cyclotron produced radioisotopes are intrinsically considered of extremely higher-priced compared to the reactor-produced radioisotopes, numerous conditions have been suggested under which their applications are preferable, and for such circumstances sound obligatory. Quite a lot of new isotopes, formerly rendered hard to get, are recently effortlessly obtainable. Our suggested measures have been described in more details for the partition of seventeen radioisotopes in a carrier-free shape: Be⁷, Na²², V⁴⁸, Mn⁵², Mn⁵⁴, Fe⁵⁵, Co⁵⁷, Zn⁶⁵, Ga⁶⁷, As⁷⁴, Sr⁸⁵, Y⁸⁸, Cd¹⁰⁹, In¹¹¹, Ce¹³⁹, W¹⁸¹ and Bi²⁰⁷. In addition, yield-dense targets have been designed for the synthesis of these radioisotopes by means of the cyclotron irradiations by using 15MeV energy of deuterons in association with other protons’ energies (8, 15 and 20MeV).

1. Rivard MJ, Bobek LM, Butler RA, Garland MA, Hill DJ, et al. (2005) The US national isotope program: Current status and strategy for future success. Appl Radiat Isot 63: 157-178. Link: https://bit.ly/2xdvtpw  
2. Saji H (2009) Manufacturing and quality control of positron emitting radiopharmaceuticals produced by in-house cyclotron. Radioisotopes 58: 115-120. Link: https://bit.ly/2X3Kqdh  
3. May MM (2017) Safety first: The future of nuclear energy outside the United States. Bull At Sci 73: 38-43. Link: https://bit.ly/2X5lX7d  
4. Synowiecki MA, Perk LR, Nijsen JFW (2018) Production of novel diagnostic radionuclides in small medical cyclotrons. EJNMMI Radiopharm Chem 3: 3. Link: https://bit.ly/2Fy0cSC  
5. Watt R, Gyles W, Zyuzin A (2015) Building on TR-24 success: advanced Cyclotron Systems Inc. launches a new cyclotron model. J Radioanal Nucl Chem 305: 93-98. Link: https://bit.ly/2FvEHSy  
6. Pazur A (2018) Calcium ion cyclotron resonance in dissipative water structures. Electromagn Biol Med 37: 100-113. Link: https://bit.ly/2FyWusa  
7. Wilkniss PE, Beach LA, Marlow KW (1972) Production of carrier-free 197m,197Hg with a Cyclotron. Radiochim Acta 17: 110-113. Link:
   https://bit.ly/2ZJ7QRU  
8. Gumiela M (2018) Cyclotron production of 99mTc: Comparison of known separation technologies for isolation of 99mTc from molybdenum targets. Nucl Med Biol 58: 33-41. Link: https://bit.ly/2ZPrrjx  
9. Mukhopadhyay B, Lahiri S (1999) Review article: separation of the carrier free radioisotopes of second transition series elements. Solvent Extr Ion Exch 17: 1-21. Link: https://bit.ly/2KIQEZx  
10. Herdzik I, Dembiński W, Narbutt J, Siekierski S (2012) Separation of Gallium and Indium isotopes by cation and anion exchange chromatography. Solvent Extr Ion Exch 30: 593-603. Link: https://bit.ly/2xbzdb1  
11. Siri S, Segovia MS, Cohen IM (2019) The production of no carrier added arsenic radioisotopes in nuclear reactors. J Radioanal Nucl Chem 319: 175-184. Link: https://bit.ly/2KC6TXX  
12. Shanmugam T, Mathan R, Selvaraj M (2018) Protective effect of Sulforaphane against Arsenic-induced hepatotoxicity in rats: Role of PI3K/Akt-mediated Nrf2 signaling pathway. Free Radic Biol Med 128: S120. Link: https://bit.ly/2XA7Vty  
13. Umegaki Y (1977) Medical use of particle accelerators. Radioisotopes 26: 49-59.
14. Prakash V (2018) Cyclotron interaction of lower hybrid wave with charged particle beams. International Journal for Research in Applied Science and Engineering Technology 6: 122-131.
15. Kiyanagi Y (2018) Accelerator-based neutron source for boron neutron capture therapy. Radiother Oncol 2: 55-55.
16. Stothers LA, Hou X, Vuckovic M, Buckley K, Bénard F et al. (2019) Analysis of radioactive waste generated during the cyclotron production of 99mTc. Phys Med Biol 64: 055008. Link: https://bit.ly/2WZ8c5b  
17. Abramychev SM, Balashov NV, Vesnovskii SP, Vjachin VN, Lapin VG, et al. (1992) Electromagnetic separation of actinide isotopes. Nucl Instr Meth Phys Res B 70: 5-8.
18. Choudhury D, Naskar N, Lahiri S (2018) Production and separation of no-carrier-added 181−184Re radioisotopes from proton irradiated tungsten target. Radiochim Acta 106: 743-749. Link: https://bit.ly/2ZO3c4X  
19. Zhu X, Lu Y (2018) Growth of beryllium thin films on beryllium (0001) surface: Influence of incident energy and incident angle by molecular dynamics simulation. J Appl Phys 124: 175304.
20. Bruninx E, Crombeen J (1969) Thick target neutron yields and neutron spectra produced by 20 MeV helium-3 ions, 14 MeV protons and 7·5 MeV deuterons on a beryllium target. Int J Appl Radiat Isot 20: 255-264. Link: https://bit.ly/2ZFicSK  
21. Browne CP (1959) Energy levels of Na22 from the Mg24 (d, α) Na22 and Mg25(p, α)Na22 reactions. Nucl Phys 12: 662-671. Link: https://bit.ly/31Rs7qh  
22. Hudis J, Tanaka S (1968) Production of Be7, Na22, an dNa24 fragments from heavy elements at 3, 10, and 30 GeV. Phys Rev 171: 1297-1300. Link: https://bit.ly/2X6uyq6  
23. Peart RF (1965) Diffusion of V48 and Fe59 in vanadium. J Phys Chem Solids 26: 1853-1861. Link: https://bit.ly/2xakaOZ  
24. Boehm F (1958) Interference between Gamow-Teller and Fermi interaction in Mn52. Phys Rev 109: 1018-1019. Link: https://bit.ly/2Xu9r0j  
25. Evers D, Harasim A, McGrath RL, Assmann W (1977) Gamma spectroscopy of Fe52, Mn52, and Cr52 from α+Cr50 reactions. Phys Rev C 15: 1690-1697. Link: https://bit.ly/2XArfXG  
26. Krasnov NN, Dmitriev PP (1966) Yields of nuclear reactions used for preparing Mn54 in a cyclotron. Soviet Atomic Energy 21: 678-680. Link:
    https://bit.ly/2RE8wFu  
27. Kiortsis M (1969) Uptake of Zn65 and Mn54 by irradiated Bacillus megaterium. Experientia 25: 761-762. Link: https://bit.ly/2J8pszS  
28. Pavlov-Verevkin BS (1970) Deactivation of radioactive waste from Fe55 production. Soviet Atomic Energy 28: 81-82. Link: https://bit.ly/2RwVHNb  
29. Jedidi A, Markovits A, Minot C, Abderrabba M (2012) Core restructuring for magnetic Fe55 icosahedral nanoparticles. Chem Phys Lett 541: 101-104. Link: https://bit.ly/2KC3pos  
30. Krasnov NN, Dmitriev PP (1966) Reaction yields for preparation of Co57 in a cyclotron. Soviet Atomic Energy 20: 70-72. Link: https://bit.ly/2Xrlvj6  
31. Lee JD, Schroeer D (1976) Mossbauer study of Fe57 and Co57 in Co1+xV27minus; xO4. Solid State Commun 18: 7.
32. Aoki T, Hagiwara M, Baba M, Sugimoto M, Mirura T, et al. (2004) Measurements of differential thick target neutron yields and 7Be production in the Li, 9Be(d, n) reactions for 25 MeV deuterons. J Nucl Sci Technol 41: 399-405. Link: https://bit.ly/2x9CuaQ  
33. Senekowitsch R, Kriegel H, Möllenstädt S (1985) Altered Uptake of Tc99m-MDP, Ca47 and Ga67 by Mice Osteogenic Sarcoma after Administration of a Cytostatic Drug. In: Cox PH, Limouris G, Woldring MG (eds), Progress in Radiopharmacology, vol 9, Springer, Dordrecht, The Netherlands 251-261. Link: https://bit.ly/2NlP81c  
34. Wilcke O (1964) Möglichkeiten und Grenzen der Hirntumordiagnostik mit Positronenstrahlern (Cu64und As74). Minim Invasive Neurosurg 7: 33-41. Link: https://bit.ly/2RxEnHB  
35. Krasnov NN, Dmitriev PP, Erlychenko VP, Konstantinov IO, Konyakhin NA, et al. (1969) Production of Sr85 in a cyclotron. Soviet Atomic Energy 27: 692-695. Link: https://bit.ly/2Lg5fuA  
36. Ramaswamy MK, Jastram PS (1960) Decay of Y88. Nucl Phys 19: 243-247. Link: https://bit.ly/2NdGlP7  
37. Sakakura H, Murakumo Y, Mii S, Hagiwara S, Kato T, et al. (2014) Detection of a soluble form of CD109 in serum of CD109 transgenic and tumor xenografted mice. PLoS ONE 9: e83385. Link: https://bit.ly/2II7lBW  
38. Takagui EM, Dietzsch O (1980) In111-In109 mass difference. Phys Rev C 21: 1667-1669.
39. Dmitriev PP, Konstantinov IO, Krasnov NN (1968) Ce139 yield in La139 (p, n) and La139 (d, 2n) reactions. Soviet Atomic Energy 24: 344-345. Link:
    https://bit.ly/2LenyAl  
40. Krasnov NN, Dmitriev PP (1966) Excitation functions and yields of the reactions Ta181 (d, 2n) W181 and Ta181 (p, n) W181. Soviet Atomic Energy 20: 189-190. Link: https://bit.ly/2FwBja3  
41. Dmitriev PP, Krasnov NN, Molin GA, Panarin MV (1972) Yields of Bi205, Bi206, and Bi207 from lead irradiated with protons or deuterons. Soviet Atomic Energy 33: 976-978. Link: https://bit.ly/2II9u0t  
42. Skobov VG, Chernov AS (2001) Nonlinear doppler-shifted cyclotron resonance in aluminum. J Exp Theor Phys 92: 338-344. Link: https://bit.ly/2KDYJyv  
43. Zhou K, Song YT, Ding KZ, Ge J, Yao K (2018) Analytical solution of transverse oscillation in cyclotron using LP method. Chin Phys C 42: 037001. Link: https://bit.ly/2XrAM3v