Aluminium irradiated sample

Samarium-153 was produced by irradiation of samarium samples at a neutron flux of 1 x 10 n cm s in the core of PARR-l. Natural or enriched 52Sm2O3 powder was sealed in quartz ampoules and placed in aluminium containers, which were then cold welded. Irradiated samples were dissolved in IM HNO3 0.2 mL of the solution was evaporated in the quartz ampoule. In another experiment, 0.2 mL of the Sm(NO3)3 solution was placed in quartz ampoules. These ampoules were sealed and cold welded in aluminium containers for irradiation. The irradiated targets were dissolved in 5M HCl and evaporated to dryness. The residue was dissolved in physiological sahne solution and diluted to a specified volume for labelhng studies. 

Electron spin resonance reveals the unpaired electrons associated with impurities or structural defects and can be used to identify the lattice site positions of these features. Nitrogen is shown to substitute for carbon and acts as a shallow donor. The various ESR triplets due to nitrogen in several SiC polytypes give information on the lattice sites occupied. For the acceptor boron, ESR shows it to occupy Si sites only, in disagreement with DAP photoluminescence measurements which show only boron on carbon sites. It may be that boron substitutes on both sites and the two techniques have sensitivity for only one particular lattice site. The aluminium acceptor is not observed in ESR but gallium has been noted in one report. Transition metals, Ti and V, have been identified by ESR both isolated on Si sites and in Ti-N complexes. Several charged vacancy defects have been assigned from ESR spectra in irradiated samples. 

Valladon et al. (237) used triton activation for the determination of oxygen in aluminium. The samples were irradiated for 1-2 h with a 1 mA beam of 3.5 MeV tritons. A 15 jum surface layer was removed by a combination of chemical etching and mechanical grinding (first 2 Mm were removed by etching in a mixture of hydrofluoric and nitric acids, then 10-12 Mm... 

The neutron activation method for the determination of arsenic and antimony in seawater has been described by Ryabin et al. [66]. After coprecipitation of arsenic acid and antimony in a 100 ml sample of water by adding a solution of ferric iron (10 mg iron per litre) followed by aqueous ammonia to give a pH of 8.4, the precipitate is filtered off and, together with the filter paper, is wrapped in a polyethylene and aluminium foil. It is then irradiated in a silica ampoule in a neutron flux of 1.8 x 1013 neutrons cm-2 s 1 for 1 - 2 h. Two days after irradiation, the y-ray activity at 0.56 MeV is measured with use of a Nal (Tl) spectrometer coupled with a multichannel pulse-height analyser, and compared with that of standards. 

Typically, the sample or object to be activated is placed in a container for irradiation. This may be aluminium foil (as aluminium cannot easily be measured by this technique) or silica glass tubes. Several samples and standards are placed in the same container for irradiation, to ensure the same conditions for samples and standards. For example, in the case of ceramics measured at the British Museum laboratories (Hughes et al. 1991), powdered... 

For example, suppose that traces of iron in an aluminium sample are to be determined. 59 Fe is characterised by 7 emission at 1.29 MeV. Aluminium under irradiation will yield 24Na, which is responsible for a 7 ray situated at 1.37 MeV via the reaction 27AI(n,a)24Na (r = 15h). Here, a time gap of several days between the end of radiation and measurement permits enough time for the aluminium to disappear. 

The samples used for irradiation must withstand the temperature and the radiation in the reactor without decomposition. In general, they are encapsulated in aluminium cans or in quartz ampoules which are introduced in irradiation tubes or directly into special positions within the reactor. 

Lutetium-177 was produced by irradiation of lutetium samples in the core of PARR-1, a swimming pool type reactor, at a thermal neutron flux of 1 X 10 n-cm -s for specified periods of time ranging from 1 to 96 h. Naturally abundant LU2O3 and enriched UiiO were dissolved in IM HNO3, evaporated to dryness and reconstituted in O.IM HNO3, and again evaporated to dryness. The Lu(NO3)3 (2.59% Lu) powder and enriched Lu(NO3)3 (68.9% Lu) powder thus obtained were sealed in quartz ampoules and cold welded in aluminium containers for irradiation. In another experiment, quartz ampoules were filled with 0.2 mL of liquid Lu(NO3)3, sealed and cold welded in aluminium containers. These targets were then irradiated in PARR-1. The... 

The isotope used to prepare labelled compounds is obtained by irradiation in a nuclear reactor, of solid targets containing atoms of nitrogen (aluminium or beryllium nitride), by neutrons of low energy, known as thermal neutrons, themselves the product of the controlled atomic fission of The radiocarbon formed is next isolated from the target sample by oxidation to Ba " 003, the variety in which it is delivered to chemists. From C02, it is possible to use a plethora of organic chemical reactions to synthesize different compounds in which the radio-isotope can be introduced to a specific position. 

A concept of the fiber-optic-based absorbance sensor is shown in Figure 18-8. Again, the fiber is threaded in a standard catheter, thus allowing its insertion into tissue or body fluids. A piece of aluminium foil is attached to the end of the inner needle (which contains the optical fiber). Fluids can be drawn into the sample irradiation cavity by aspiration, the volume between foils and Hber being Hlled through the hole shown. Typical pathlengths (twice the distance from the Hber tip to the foil) are O.S-4.3 mm. 

A block diagram of a TL instrument, which is composed of a light-proof box with a heating block to which the sample and a thermocouple are attached, is presented in Figure 6.20. An aluminium window allows the sample to be irradiated before heating. The chamber can be evacuated or purged with an inert gas. The TL sensor is a high-sensitivity photomultiplier with a dark... 

The weakly nitric-acid solution obtained as a result of concentration of the water sample is extracted with ethyl acetate following the addition of aluminium nitrate. The organic phase containing the uranium is separated off, evaporated in a platinum crucible, and the uranium is melted at 630 °C after adding sodium fluoride/potassium carbonate/sodium carbonate as a fluxing agent. The yellow-green fluorescence of the melt which appears when irradiated with an ultraviolet lamp is compared with that of standard samples prepared under equivalent conditions. 

The samples for irradiation are normally put in glass, polythene, or aluminium containers. Comparison between these containers has been discussed by Sroor et al. (2000). 

Beads of mass 5-10 mg were first cleaned ultrasonically, as required. They were stored individually in 1.2 mL polyethylene vials, were irradiated serially for five minutes at a neutron flux of 1.0 10 neutrons.cm. sec. Five to seven minutes after irradiation, the induced radioactivity was counted for five minutes using a hyper-pure germanium detector-based gamma-ray spectrometer. This produced analytical concentration data for cobalt (Co), tin (Sn), copper (Cu), sodium (Na), aluminium (Al), manganese (Mn), chlorine (Cl) and calcium (Ca). The samples were recounted for five to thirty-three minutes the next day to measure the concentrations of the longer-lived radioisotopes of Na, arsenic (As),... 

Apart from other published experiments [4.57] related to EURECA, mission radiation and recording of EPR spectra have been done at room temperature (see spectrum 3 in Fig. 4.61). Spectra 1 and 2 result from samples irradiated at 77 K, recorded at 170 K and irradiated at 77 K, annealed at 440 K, and recorded at 170 K, respectively (published in [4.57]). The main, quite complicated signal around gfree consists basically of a variety of the so-called oxygen hole centres (OHCs) close to aluminium or silicon. Aluminium has a natural abundance of 100% AP with 1 = 5/2, yielding a hyperfine coupling. In accordance with other publications it has been shown that all the A1 OHCs are situated in the h-quartz s.s. crystal phase of Zerodur . The computer simulation of the spectrum needed no distribution in the spin Hamiltonians as is necessary in random networks. 

These devices automatically follow the path of the sun in the sky. EMMA contains 10 highly polished aluminium mirrors precisely placed on a rack which is turned and tilted at computed angles in order to focus the sunlight onto the surface of the sample (3 cm x 13 cm) (Figs 10.128, 10.129). The mirrors reflect 70-78% of the UV radiation of sunlight and consequently the intensity of irradiation is about 8-10 times higher than in the case of a fixed... 

A flux monitor is irradiated and measured simultaneously with the sample and the standard. A double rectangular section (internal dimensions 26.5 X 9.5 mm) aluminium transport system is used. At the irradiation site, the tubes are placed one after another, the sample being nearest to the target. 

The samples and the standards are in general irradiated in vacuum, placed in an appropriate sample holder, to be mounted on the accelerator beam transport system. A simple sample holder is shown in Fig. 11-19. It is watercooled and an aluminium tube is placed on the sample holder to minimize the escape of secondary electrons, which may result in inaccurate beam intensity measurements. Before the sample holder a collimator is placed as shown in Fig. II-21b. 

Figure 11-39 shows a simple irradiation device. The platinum target (0 30 mm, thickness 6 mm) is water cooled. The sample and standard are introduced into the front part of the aluminium cartridge, which is closed by crimping. 

Boron concentration (ng/g) in an aluminium sample that yields at the end of an irradiation (1 mA intensity, irradiation time = one half life) at the indicated energy an activity of 100 desintegrations/min... 

Mortier et al. (32) irradiated for 2 h (aluminium) or 30 min (aluminium-magnesium alloy) with a 4 mA beam of 6 MeV protons, which was degraded to 4.3-4.6 MeV. After the irradiation, the sample was etched in a mixture of 7 volumes of concentrated phosphoric acid, 2 volumes of concentrated sulphuric acid and 1 volume of concentrated nitric acid at 80-90 C, to remove a 5-10 Mm surface layer. After a 20-60 d cooling time, the samples were measured with a Ge(Li) spectrometer for 60 h (aluminium) or for 20 h (alumi n i um-magnes i urn). 

The procedure of Mortier et al. (32) for the determination of boron in aluminium and aluminium-magnesium alloy is as follows The sample is irradiated for 20 min with a 2 uA beam of 7 MeV deuterons, which are degraded to 5.3-5.7 MeV, and a surface layer is removed by chemical etching (2.3.1). To separate the sample is dissolved in an oxidizing mixture of phosphoric acid, sulphuric acid and potassium dichromate. The C02 released is absorbed in 0.5 M sodium hydroxide and the activity measured with a t-t coincidence set-up. A pure decay is obtained. The chemical yield was checked by comparing, in a separate experiment, the activity of an aluminium sample, doped with 5000 tig/g of boron, measured instrumentally and after chemical separation. The yield was 100 %. 

This process has been used extensively to determine carbon in sodium purified by filtration. The samples were poured into Pyrex ampoules lined internally with a sheet of aluminium to facilitate recovery. These ampoules, placed in aluminium cartridges, were conveyed through the irradiation device by means of a pneumatic circuit. 

---