Speaker
Description
Medical accelerator-driven neutron sources are in a unique position. There are many accelerator neutron sources for experimental research, flux up to ~10^8n/s scale, and large-scale spallation-type facilities with high intensity exceeding ~10^13n/s. Accelerator-driven neutron sources for medical use[1], which are now becoming popular, are in a unique position, lying between the two.
At present, excluding the accelerator type, there are a variety of medical accelerator neutron devices such as neutron target materials (Li, Be) and charged particle energies (2.5, 8, 30 MeV)[2].
In addition, about 50 to 80 kW of power is required. Considering that the maximum EBW in widespread use is about 5 kW, a fierce struggle of R&D was expected.
Several types of neutron targets have been published in papers, but blistering, which has been assumed during development, was described by Forton et al. IBA group [3] in INCCT-13. Preliminary experiments with weakened strength require long-term operation, and the strength simulated in practice requires protection against radiation strength. There is a need for an irradiation device that is just now in demand, and more experimental evidence is needed.
We think that two elements, namely defect control and thermal management, are necessary as keywords for the development of this 10^8~10^13n/s neutron source, which should occupy among the existing accelerator-driven neutron sources.
The behavior of protons and hydrogen (atoms) in metals, the dissolution of hydrogen in solids, and the diffusion of hydrogen in beryllium are the subject of research and investigation. It is said that the diffusion of hydrogen in beryllium is slower than in other metals, but what is the rate-limiting part? The BINP group has proposed a blistering threshold, but these various amounts serve as guidelines[4].
After hydrogenating the sample, if it is taken out into the atmosphere, the hydrogen partial pressure in the atmosphere is almost zero, so the hydrogen in the metal should be lost little by little, but in reality this does not happen. It is often thanks to surface barriers that state diagrams have practical meaning. That is, it depends on the conditions at the surface, interface, rather than in the bulk[5].
The discussion of the mean free path in the 2nm process of semiconductor manufacturing and the discussion of Ru instead of Cu are helpful.
Such physics related to material defects, heat treatment of mixed phases of solid phase, liquid phase and gas phase, heat transfer and heat generation not based on diffusion. What is the assumed mean free path? I think that such discussion and consideration will be necessary.
references
[1] IAEA-TECDOC-1223
[2] Reviews of Accelerator Science and Technology Vol. 8 (2015) 181–207
[3] Applied Radiation and Isotopes 67 (2009) S262–S265
[4] Journal of Nuclear Materials 396 (2010) 43–48
[5] EPJ Web of Conferences 231, 03001 (2020)
| Themes for the contribution | 4 Target design, analysis, and validation of concepts: |
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