Target irradiated

Fig. 7.7. Spectrum of the X-ray radiation detected from the front side and from the rear side of a three-layer Cr-Ni-Fe target irradiated at an intensity of 5 x 1019 W cm 2. The spectrum was obtained adding up all identified photon from the analysis of the low flux images obtained from 350 laser shots. The target was irradiated on the Cr side. Note that the relative intensities of the two spectra are not to scale...

A frequently used procedure is targeted irradiation with y-rays, which block cell reproduction due their mutagenic effect (see p. 256). Another approach is to inhibit cell growth by chemotherapy. The growth-inhibiting substances used are known as cytostatic drugs. Unfortunately, neither radiotherapy nor chemotherapy act selectively—i. e., they damage normal cells as well, and are therefore often associated with severe side effects. 

The first cyclotron was built by Ernest O. Lawrence in 1932, and since 1938, cyclotrons have been used for patient treatment. In Berkeley, in 1954, the first human target irradiated with protons was the pituitary gland with the aim to suppress its function for slowing down the metastatic development of breast cancer. 

Optoexplosive System Including Nuclear Explosive Light Generator and Target Irradiation", USP 3715596 (6 Feb 1973)... 

The relevant nuclear reaction for tellurium is primarily Sb-121(p,4n)Te-118 with some contribution from the (p,6n) reaction on Sb-123 (42.7% abundance). The nuclear excitation functions for these reactions have not been measured. A series of stacked foil irradiations is planned to determine thin target cross sections. This will allow selection of optimal bombardment parameters for thick target irradiation at the BLIP. A calculated excitation function for the (p,4n) reaction is shown in Figure 8. This calculation is based on the interpolation method of Munzel et al. (11) and should allow prediction of thick target yields to within a factor of 2 or 3. 

It is easy to calculate the number of product nuclei produced during an irradiation, N. If we assume the product nuclei are stable, then the number of nuclei produced is the (rate of production) x (length of the irradiation, t). For a thick target irradiation, we have... 

Various combinations of projectiles and targets are in principle possible for the synthesis of heavy elements actinide targets irradiated by light projectiles of elements in the range from neon to calcium, targets of lead and bismuth irradiated by projectiles from calcium to krypton, and symmetric combinations like tin plus tin up to samarium plus samarium. Also inverse... 

Table I. Neutron cross section parameters used to compute transmutations in HFIR target irradiations...

Preparation of Target, Irradiation in Reactor and Dissolution - Am02 powder and an excess of A1 powder were well mixed and irradiated at a neutron flux of 6.8 x 1013 neutron/ cm2/sec until an integral flux of 2.6 x 1020 neutrons/cm2 was achieved. The resulting mixture was dissolved as shown in Figure 1. 

The third means of radionuclide production involves target irradiation by ions accelerated in a cyclotron. One example of this approach is provided by the production of Ge, which decays with a 280 day half-life to the positron emitter Ga. Proton irradiation of Ga produces Ge in a (p,2n) reaction. After dissolution of the target material a solution of the Ge product in concentrated HCl is prepared and adsorbed on an alumina column which has been pre-equilibrated with 0.005 M EDTA (ethylenediaminetetraacetate) solution. The Ga daughter may then be eluted using an EDTA solution in a system which provides the basis of a Ga generator. Cyclotron production of radionuclides is expensive compared with reactor irradiations, but higher specific activities are possible than with the neutron capture process. Also, radionuclides with particularly useful properties, and which cannot be obtained from a reactor, may be prepared by cyclotron irradiation. In one example, cyclotron produced Fe, a positron emitter, may be used for bone marrow imaging while reactor produced Fe, a /3-emitter, is unsuitable. " ... 

The French transplutonium elements production program (essentially 21+3Am and 2l+,+ Cm) is based on the treatment of plutonium-aluminum alloy targets irradiated in the Celestin reactors at Mar-coule. At the time of chemical treatment, these targets (which initially contained approximately 400 g of 239Pu) contain 44 g of 21+2Pu, 8.5 g of 2l+3Am, 7.5 g of 2l+,+Cm, and about 340 g of fission products, including - 240 g of lanthanides, chiefly the elements La, Ce and Nd (J). 

The shape of the focal spot on the target irradiated by the electron beam is essentially a projection of the coiled filament, and its size is typically 1 x 10 mm. When the x-rays from such a focal spot exit through the tube window at a take-off angle a of 6°, the beam has a roughly 1 x 1 mm cross section, if the window is along the extension of the long dimension of the focal spot, as in Figure 2.2. The beam, on the other hand, appears to have a 0.1 x 10 mm cross section, if the window is... 

N-Nitrogen can also be prepared from water targets irradiated with protons. The from a water target has been used to prepare... 

Doping atom Preparation method Ti precursor Dopant source Removal target Irradiation wavelength (nm) Ref. 

Polymer substrate Immobilization method Removal target Irradiation waveiength (nm) Ref. 

The shield cask serves to provide radiation shielding for facility workers during the transfer of irradiated targets from the ACRR core to the HCF steel transfer box. The thickness of DU in the cask is sufficient to reduce the dose rate from a Mo-99 target irradiated for 7 days at 20 kW fission power followed by a 6-hour decay to approximately 5 mR/hr on contact... 

In addition, the short target irradiation times used during isotope production result only in the generation of low-level waste no transuranic waste is generated. 

Figure 8.14 Schematic representation of radioisotope excitation system with annular source configuration (a) direct irradiator (b) secondary target irradiator. (Reprinted from Ref. 9 with permission from Kevex Corp., Burlingame, Calif.)...

FIGURE 2 Imaging of atmospheric path luminance irradiation Ha together with target irradiance Hj over identical image-plans space. 

A CU3AS target irradiated with protons contains both Se and As, formed via As(p,n) Se and As(p,pn) As reactions, respectively. Detailed removal studies as a function of temperature revealed that [ As] AS2O3 is removed at 600° C, whereas for removal of radioselenium, a temperature of about 1,100°C is required. Thus, by a two step thermochro-matographic treatment, it is possible to separate radioselenium from the matrix. 

---