Stopping powers of havar for 1.6, 2.3 and 3.2 MeV/u heavy ions

Energy Technology Data Exchange (ETDEWEB)

Alanko, T. E-mail: tommi.alanko@phys.jyu.fi; Hyvoenen, J.; Kylloenen, V.; Raeisaenen, J.; Virtanen, A

2000-03-01

Stopping powers of havar for {sup 28,30}Si-, {sup 36}Ar-, {sup 54,56}Fe- and {sup 80,84}Kr-ions with energies of 1.6, 2.3 and 3.2 MeV/u have been determined by a transmission technique. Sample foils are exposed to the direct beams. No previous data for havar with these ions have been published. The obtained results are brought together with literature havar data for {sup 1}H-, {sup 4}He-, {sup 7}Li-, {sup 11}B-, {sup 12}C-, {sup 14}N-, {sup 16}O- and {sup 127}I-ions at the same ion velocity. The experimental data are compared with the values predicted by the SRIM-2000 parametrization using Bragg's rule. A systematic underestimation, by 6-23%, of the experimental stopping powers was observed. The empirical correction scheme of Thwaites has been applied to the stopping power values obtained by the parametrization. The corrected values agree well with the present results. Also, the effective charge values of the various ions were deduced from the experimental set of data.

Polycarbonate, Mylar and Havar stopping powers for 1.0-3.25 MeV/nucleon {sup 40}Ar-ions

Energy Technology Data Exchange (ETDEWEB)

Alanko, T. [Department of Physics, University of Jyvaeskylae, Jyvaeskylae (Finland)]. E-mail: tommi.alanko@phys.jyu.fi; Hyvoenen, J.; Kylloenen, V.; Laitinen, P.; Matilainen, A.; Raeisaenen, J.; Virtanen, A. [Department of Physics, University of Jyvaeskylae, Jyvaeskylae (Finland)

2001-12-03

Stopping powers of polycarbonate, Mylar and Havar for 1.0-3.25 MeV/nucleon {sup 40}Ar-ions have been determined by the transmission method in two geometries. The stopping power values were obtained within uncertainty of 2.1-4.5% for the various materials. The present results are compared with the predictions obtained by the most commonly used procedures employed in obtaining stopping powers. These include the Northcliffe and Schilling model, semi-empirical parametrization of Ziegler et al (SRIM2000) with and without the cores and bonds model and the Hubert et al formulation. SRIM2000 values were in good agreement in case of Mylar and Havar, on average within 3% of present results. For polycarbonate the differences were less than 6% on average. The cores and bonds (CAB) model improved the parametrization values slightly. The Northcliffe and Schilling model and the Hubert et al formulation both yielded values within 5% or less for Mylar and polycarbonate. For the Havar the Hubert et al formulation and the present results disagreed by 10% on average. (author)

Stopping powers of havar and effective charge for 1.4-3.2 MeV/u {sup 127}I-ions

Energy Technology Data Exchange (ETDEWEB)

Alanko, T. E-mail: tommi.alanko@phys.jyu.fi; Hyvoenen, J.; Kylloenen, V.; Raeisaenen, J.; Virtanen, A

2000-06-01

Stopping powers of havar for 1.4-3.2 MeV/u {sup 127}I-ions have been determined by the transmission technique using two geometrical arrangements. No previous data have been published for havar with this ion. The experimental data are compared with predictions obtained by using Bragg's additivity rule with various parametrizations of the stopping power found in the literature. The values obtained by the parametrizations underestimate the experimental data by 5-11%. The empirical correction scheme of Thwaites yields values in rather good agreement with the present results, especially at energies above 1.9 MeV/u. The effective charges of the {sup 127}I ions were also deduced from the experimental data.

Improved 10Be and 26Al-AMS with a 5 MV spectrometer

International Nuclear Information System (INIS)

Xu Sheng; Dougans, Andrew B.; Freeman, Stewart P.H.T.; Schnabel, Christoph; Wilcken, Klaus M.

2010-01-01

Detector and ion source changes have increased Be and Al count rates and reduced measurement background at SUERC. Low energy 16 MeV 26 Al 3+ ions can be separated from interferences by adopting thin silicon nitride membrane detector windows. In contrast, a thick Havar detector window is used to preferentially slow boron ions for simplified 10 Be vs. 10 B separation without an additional gas cell.

Measurement of the induced radionuclides in production of radiopharmaceuticals for positron emission tomography (PET)

International Nuclear Information System (INIS)

Machizuki, Shingo; Ogatam Yoshimune; Ishigure, Nobuhito; Hatano, Kentaro; Abe, Junichiro; Ito, Kengo; Ito, Yoshihiro; Nishino, Masanari; Miyahara, Hiroshi

2006-01-01

The radioactive by-products contained in an entire series of target foil, [ 18 O]H 2 O and synthesis apparatus were identified and quantified. From the perspective of waste management, 60 Co induced in Havar foil should be taken into consideration. Because the exempt activity of 60 Co in BSS is 0.1 MBq, the used Havar foil should be managed more than for 20 years. The radionuclides in the [ 18 F]-FDG synthesis apparatus are negligible. Equivalent doses at skin and to tissues were estimated assuming a point source at a distance of 30 cm in air. The annual equivalent doses at skin and equivalent dose at deep tissues of such an operating staff will be 56 and 8.3 μSv, respectively, as two times the remove of the target foil and five hundreds times the synthesis of the [ 18 F]-FDG. When proper radiation protection is provided, the exposure from the cyclotron management and the [ 18 F]-FDG synthesis process will not cause meaningful radiological risk to the operating staff. The activity concentration of 3 H, 180 kBq·cm -3 , detected in the target water, is 3,000 times the legal limit of effluent for 3 H. The operators should take care of the treatment of the target water when they make a distillation for reuse and a disposal. (author)

Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for ["1"8F] production

International Nuclear Information System (INIS)

Skliarova, Hanna; Renzelli, Marco; Azzolini, Oscar; Felicis, Daniele de; Bemporad, Edoardo; Johnson, Richard R.; Palmieri, Vincenzo

2015-01-01

Chemically inert coatings on Havar"® entrance foils of the targets for ["1"8F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar"®. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for [{sup 18}F] production

Energy Technology Data Exchange (ETDEWEB)

Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Renzelli, Marco, E-mail: marco.renzelli@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); Felicis, Daniele de, E-mail: daniele.defelicis@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Bemporad, Edoardo, E-mail: edoardo.bemporad@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

2015-09-30

Chemically inert coatings on Havar{sup ®} entrance foils of the targets for [{sup 18}F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar{sup ®}. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

Results of the Czech-Austrian calculations of BDBA radiological consequences

International Nuclear Information System (INIS)

Carny, P.; Hohenberg, J.-K.

2003-01-01

Full text: Common Czech - Austrian comparisons of codes and calculations of BDBA radiological consequences have been performed. Background of these comparisons is described in the paper presented at this symposium. Results of single steps are summarized and discussed in this poster presentation. From the Czech side calculations have been performed with computer codes PC Cosyma, este, RTARC, HAVAR, HERALD, PTM, RODOS/MATCH and long range code MEDIA used by the Czech meteorological institute (CHMI). Code PC Cosyma is taken as main comparable code in this inter-comparisons as it is used by the Czech and the Austrian side. For every accident scenario and for deterministic as well as probabilistic assessment of accident consequences results of both sides have been practically identical. Computer code 'este' is instrument for projection of release and evaluation of real release under real VVER 440 and WER 1000 emergency conditions. The code can be operated with real radiological, meteorological and technological data from the plant. The code calculates projection of avertable doses and simulates movement of radioactive clouds in the vicinity (up to 40-50 km) of the plant. The code participates in these comparisons as it serves as a support instrument for the staff at the emergency centre of the Czech nuclear regulatory body. Code RTARC (Real Time Accident Release Consequences) serves as an instrument for evaluation of radiation situation in the vicinity of the plant (up to 40 km) during the early phase of an accident. The code participates in these comparisons as it was used in the process of the Czech nuclear power plants protective action planning zone determination. Codes HERALD and HAVAR have been used by Skoda and Energoprojekt for analyses of consequences of design bases accidents in Temelin safety report. They were compared with PC Cosyma in one step of these common calculations by the Czech side. The code HAVAR enables to calculate ingestion doses, too, and

Co-sputtered amorphous Nb–Ta, Nb–Zr and Ta–Zr coatings for corrosion protection of cyclotron targets for [{sup 18}F] production

Energy Technology Data Exchange (ETDEWEB)

Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver, BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

2015-08-05

Highlights: • Nb–Ta, Nb–Zr and Ta–Zr alloy films were deposited by co-sputtering. • Co-sputtered Nb–Zr and Nb–Ta alloy coatings had crystalline microstructures. • Diffusion barrier efficiency of Nb–Zr and Nb–Ta decreased with the increase of Nb %. • Co-sputtered Ta–Zr films with 30–73 at.% Ta were amorphous. • Sputtered amorphous Ta–Zr films showed superior diffusion barrier efficiency. - Abstract: Protective corrosion resistant coatings serve for decreasing the amount of ionic contaminants from Havar® entrance foils of the targets for [{sup 18}F] production. The corrosion damage of coated entrance foils is caused mainly by the diffusion of highly reactive products of water radiolysis through the protective film toward Havar® substrate. Since amorphous metal alloys (metallic glasses) are well-known to perform a high corrosion resistance, the glass forming ability, microstructure and diffusion barrier efficiency of binary alloys containing chemically inert Nb, Ta, Zr were investigated. Nb–Ta, Nb–Zr and Ta–Zr films of different alloy composition and ∼1.5 μm thickness were co-deposited by magnetron sputtering. Diffusion barrier efficiency tests used reactive aluminum underlayer and protons of acid solution and gallium atoms at elevated temperature as diffusing particles. Though co-sputtered Nb–Ta and Nb–Zr alloy films of different contents were crystalline, Ta–Zr alloy was found to form dense amorphous microstructures in a range of composition with 30–73% atomic Ta. The diffusion barrier efficiency of Nb–Zr and Nb–Ta alloy coatings decreased with increase of Nb content. The diffusion barrier efficiency of sputtered Ta–Zr alloy coatings increased with the transition from nanocrystalline columnar microstructure to amorphous for coatings with 30–73 at.% Ta.

Single-jet gas cooling of in-beam foils or specimens: Prediction of the convective heat-transfer coefficient

Science.gov (United States)

Steyn, Gideon; Vermeulen, Christiaan

2018-05-01

An experiment was designed to study the effect of the jet direction on convective heat-transfer coefficients in single-jet gas cooling of a small heated surface, such as typically induced by an accelerated ion beam on a thin foil or specimen. The hot spot was provided using a small electrically heated plate. Heat-transfer calculations were performed using simple empirical methods based on dimensional analysis as well as by means of an advanced computational fluid dynamics (CFD) code. The results provide an explanation for the observed turbulent cooling of a double-foil, Havar beam window with fast-flowing helium, located on a target station for radionuclide production with a 66 MeV proton beam at a cyclotron facility.

Analysis of improvement in performance and design parameters for enhancing resolution in an atmospheric scanning electron microscope.

Science.gov (United States)

Yoon, Yeo Hun; Kim, Seung Jae; Kim, Dong Hwan

2015-12-01

The scanning electron microscope is used in various fields to go beyond diffraction limits of the optical microscope. However, the electron pathway should be conducted in a vacuum so as not to scatter electrons. The pretreatment of the sample is needed for use in the vacuum. To directly observe large and fully hydrophilic samples without pretreatment, the atmospheric scanning electron microscope (ASEM) is needed. We developed an electron filter unit and an electron detector unit for implementation of the ASEM. The key of the electron filter unit is that electrons are transmitted while air molecules remain untransmitted through the unit. The electron detector unit collected the backscattered electrons. We conducted experiments using the selected materials with Havar foil, carbon film and SiN film. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Realization of a liquid hydrogen target

International Nuclear Information System (INIS)

Libin, J.F.; Gangnant, F.

1997-01-01

Experiments by the SPEG facility at GANIL need liquid hydrogen targets of some cm 3 . To achieve such targets, temperatures lower than 20 K must be obtained while their thin windows must withstand to pressures higher than 1000 m bars at these temperatures. Havar windows of 4.4 μm thickness met these requirements. A RW5 type Leybold cryo-generator was used as well as a system of ohmic heaters allowing regaining the initial state in a time equivalent with time elapsed for cooling. The working regime was chosen to be constant volume - variable pressure. The various components of this equipment (cryogenic head, buffer volume, hydrogen reservoir and vacuum pump) were coupled through 'aeroquip' allowing by dismantling and changes to keep the hydrogen isolated from the ambient atmosphere. The tests confirmed the accuracy of estimations done for the buffer volume and pressure. The only uncertainty is related to the window deformations. The time of cooling and reheating of target is around one hour. This allows during an experiment to aerate the chamber as the target was accessible to any necessary intervention

Evaluation of residual radioactivity and dose rate of a target assembly in an IBA cyclotron

Energy Technology Data Exchange (ETDEWEB)

Hwang, Seon Yong; Kim, Young Ju; Lee, Seung Wook [School of Mechanical Engineering, Pusan National University (Korea, Republic of)

2016-12-15

When a cyclotron produces 18F-, accelerated protons interact with metal parts of the cyclotron machine and induces radioactivity. Especially, the target window and chamber of the target assembly are the main parts where long-lived radionuclides are generated as they are incident by direct beams. It is of great importance to identify radionuclides induced in the target assembly for the safe operation and maintenance of a cyclotron facility. In this study, we analyzed major radionuclides generated in the target assembly by an operation of the Cyclotron 18/9 machine and measured dose rates after the operation to establish the radiation safety guideline for operators and maintenance personnel of the machine. Gamma spectroscopy with HPGe was performed on samples from the target chamber and Havar foil target window to identify the radionuclides generated during the operation for production of 18F-- isotope and their specific activity. Also, the dose rates from the target were measured as a function of time after an operation. These data will help improve radiological safety of operating the cyclotron facilities.

Radiation damage measurements on nonmetals made during irradiation with 1 to 3 MeV electrons. Final Report

International Nuclear Information System (INIS)

Levy, P.W.

1982-01-01

To investigate the fundamental processes producing radiation damage in nonmetals a unique facility has been developed for making optical absorption, luminescence and other measurements during irradiation with 1 to 3 MeV electrons. Measurements are made with a 13 meter long double beam spectrometer arranged so that all sensitive components, e.g., phototubes, are outside of the irradiation chamber. A computer provdies automatic control and data recording. A 256 point absorption and a 256 point luminescence spectra are recorded as often as every 40 seconds in either the 200-400 or 400-800 mm wavelength range. Samples are irradiated, at temperatures between 20 and 900 C, in an electronically controlled chamber containing He exchange gas and equipped with thin Havar windows to transmit the electron beam and high purity fused silica windows for the spectrophotometer beams. Radiation induced luminescence and absorption in the chamber windows, etc. is eliminated by the double beam spectrophotometer. Studies made with this equipment demonstrate clearly that many of the processes occurring during damage formation are transient

New approach to energy loss measurements

CERN Document Server

Trzaska, W H; Alanko, T; Mutterer, M; Raeisaenen, J; Tjurin, G; Wojdyr, M

2002-01-01

A new approach to energy loss measurements is proposed. In the same experiment electronic stopping force (power) in gold, nickel, carbon, polycarbonate and Havar for sup 4 sup 0 Ar, sup 2 sup 8 Si, sup 1 sup 6 O, sup 4 He and sup 1 H ions in the energy range 0.12-11 MeV/u has been measured. In this paper we give the full results for gold, nickel, and carbon and for sup 4 sup 0 Ar, sup 1 sup 6 O, sup 4 He and sup 1 H ions. Good agreement of the measured stopping force values for light ions with literature data is interpreted as the positive test of the experimental technique. The same technique used with heavy ions yields agreement with the published data only for energies above 1 MeV/u. At lower energies we observe progressively increasing discrepancy. This discrepancy is removed completely as soon as we neglect pulse height defect compensation. This observation makes us believe that the majority of the published results as well as semi-empirical calculations based on them (like the popular SRIM) may be in er...

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

International Nuclear Information System (INIS)

Alharbi, A.A.; Alzahrani, J.; Azzam, A.; Nuclear Research Center, Cairo

2011-01-01

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 nat Ni(p,x) 57 Ni, nat Co(p,x) 58(m+g) Co and nat Mo(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.

Design considerations for foil windows for PET radioisotope targets

International Nuclear Information System (INIS)

Hughey, B.J.; Shefer, R.E.; Klinkowstein, R.E.; Welch, M.J.

1992-01-01

This paper describes the results of a study performed at SRL to develop analytical and computational techniques for optimizing the design of conduction-cooled foil windows for PET targets. Single foil conduction cooled windows have been found to be good target entrance windows for both low energy accelerators and medium energy cyclotrons. Detailed thermal analysis has given an approximate analytical expression for the maximum temperature reached in a foil window under conditions of realistic ion beam bombardment. The effects of 'hot spots' in the beam density profile were investigated. It was shown that a factor of two safety margin in window design should be adequate to compensate for any possible beam hot spots. In addition, the reduction of foil stress by slack mounting was verified by experiments. The properties of conventional and novel foil materials were investigated for use in conduction cooled windows. Novel foil materials include two-component Al/Ti and Al/Havar foil. Results on the testing of candidate foil materials for thermal conductivity and mechanical strength at elevated temperature were presented. Two optimum foil window geometries were analyzed: a high aspect ratio window and a multiply slotted window. The multiply slotted window combines the advantages of a high aspect ratio foil window with a circular beam strike and is a promising window design for both TCA and cyclotron targets. A multiply slotted window for a N 2 gas target for 15 O production was designed using the methodologies discussed above. This prototype target was successfully tested using the TCA beam at SRL. (author) 6 figs., 3 tabs., 10 refs

Target generated impurities present during the synthesis of FDG

International Nuclear Information System (INIS)

Henderson, D.J.; Barnes, R.K.; Fawdry, R.M.; Stimson, D.H.

1997-01-01

Full text: Target cells employed in the production of aqueous 18 F - are made from high purity silver. A target foil manufactured from Havar a high-strength non-magnetic alloy, is in contact with the target solution at the beam-strike end of the target cell. It has been postulated that metallic impurities, possibly leached from the target during proton bombardment, could hinder reactions of no carrier added (NCA) 18 F - , used in the synthesis of fluorodeoxyglucose (FDG). With the objective of increasing the radioactive yields of FDG, we have investigated the consistency of nuclear yields from the cyclotron targets and measured, using two different analytical methods, the levels and types of metal cation impurities in the 18 F- target solutions. Gamma-ray spectroscopy of decayed 18 F samples allowed the identification and quantification of radioimpurities. The second procedure involved the quantitative analysis of non-radioactive metallic impurities in both pre-bombardment and decayed samples by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Nuclear yields consistently average mCi/μA 224 at saturation, approaching the theoretical yields of mCi/μA 225 for 18 F production at 16 MeV. Levels of 51 Cr, 52 Mn and radiocobalts were less than 475 Bq/mL at end of bombardment. The non-radioactive contaminants, such as Co, Ni, Mn Fe and Cr, were present in amounts less than 30 ng/mL. Further, it was found that these target-generated impurities were successfully trapped by purification steps in the FDG syntheses

Measurement of volatile evolution from polyurethane induced by accelerated ion beam irradiation

International Nuclear Information System (INIS)

Murphy, J.J.

2003-01-01

Irradiation of polymer samples using an accelerated beam of He 2+ ions passed through a 10μm thick window of havar foil has been performed. Such irradiation simulates the effects of large α radiation doses, on a vastly reduced time-scale. Analysis of volatiles evolved during irradiation is performed by a residual gas analyser (RGA), which is located close to the sample chamber. Presented in this paper are the results obtained during a radiation study on polyester/MDI based polyurethane materials. During high dose rate irradiation a number of high mass species were observed. A comparison between two similar polyurethanes formulated with slightly different polyesters indicated some differences. They were, however, too minor to link to specific degradation mechanisms. The dominant degradation products evident to the RGA at low dose rates were H 2 , CO and CO 2 . A series of polyurethane samples previously conditioned by γ irradiation at doses between 0 and 5MGy were irradiated in the ion beam. Identification of differences in trends in the rates of volatile evolution between these samples indicated the precise vacuum conditions at the time of irradiation had a major influence. There was also an indication that the surface of the sample had a small effect on rates of volatile evolution. Comparative plots of CO and CO 2 evolution for a series of 1MGy irradiations indicated variations in behaviour between samples with different γ doses. Evolution during the first 1MGy was inhibited for the unirradiated sample, the extent of inhibition diminished with increasing γ dose and was no longer evident in a sample with 1.5MGy γ dose. H 2 does not show an equivalent inhibition. Evidence for a low dose crosslinking reaction is put forward as a reason for the inhibition. Chemical reaction mechanisms are postulated and used to explain differences in the behaviour observed

SU-E-T-534: Level of Residual Radioactivity of Activated Parts of a Decommissioned Cyclotron

International Nuclear Information System (INIS)

Choi, HHF; Leung, TM; Chiu, TL; Yang, B; Wu, PM; Cheung, KY; Yu, SK

2015-01-01

Purpose: CTI cyclotron RDS-111 was used at the Hong Kong Sanatorium and Hospital (HKSH) to produce radiopharmaceuticals and radioactive tracers for diagnostic scans between 1999 and 2007. During the operation, some machine components became radioactive by activation. For the safety of staff, decommissioning took place in 2009, two years after the cyclotron had stopped operation. This study investigates the residual radioactivity and radionuclides found in different cyclotron components in 2014 in compliance with the local regulations in Hong Kong for transfer of radioactive waste. Methods: A representative sample of each part was counted using a high-purity germanium detector (manufacturer: ORTECT) for at least four hours. GammaVision, a multichannel analyzer software, was used to identify the radionuclides found in the cyclotron components, as well as the associated activities. A standard library and a Mariscotti peak search algorithm were used to identify the present radionuclides. Only radionuclides with half-life greater than 180 days were considered. Results: Among the components, the Havar target foil has the highest specific activity ((4.6±0.6)×10 2 Bq/g), with Co-60 being the most prominent ((3.8±0.5)×10 2 Bq/g). The total activity of the target foil, however, is still low due to its small mass of 0.04 g. Radioisotopes Mn-54 (46±6 Bq/g), Na-22 (6.8±0.8 Bq/g), Co-57 (7.3±0.9 Bq/g), and Fe-59 (6.0±0.9 Bq/g) have also been detected in the target foil. The target window holder and the vacuum window register a specific activity of 88.3±0.6 Bq/g and 48.6±0.1 Bq/g, respectively. Other components, such as the collimator, the target tube, the valve body and the beamline, are also found with trace amounts of radionuclides. Conclusion: Even seven years after the cyclotron had stopped operation, some components still exhibited residual radioactivity from activation exceeding the IAEA clearance levels. Special consideration for radiological protection may need