At IBA a compact 14 MeV H+ cyclotron has been constructed. A special feature of this cyclotron is that there is no electrical deflector installed, i.e. the beam is selfextracted. The goal is to obtain high beam currents with good extraction efficiency without the need of single turn extraction. This is achieved with two ingredients: i) a special shaping of the magnetic field, showing a very steep fall-off near the outer radius of the pole and ii) the creation of a lar ge turn-separation on the last turn. The pole gap has a quasi-elliptical shape, allowing for the steep fall-off of the magnetic field by the machining of a groove in one of the poles at a radius where the gap is small. The lar ge turn separation is obtained by either the use of harmonic coils or by permanent magnet field bumps placed in two opposite valleys. Both methods have been tested and give good results with an extraction efficiency of 80 %. The concept and layout of the machine is explained. The status of the project is outlined. First results of beam tests are presented. The cyclotron is intended for medical isotope production at multi-mAbeam intensity.
Background
Bdelloid rotifers are micro-invertebrates distributed worldwide, from temperate latitudes to the most extreme areas of the planet like Antarctica or the Atacama Desert. They have colonized any habitat where liquid water is temporarily available, including terrestrial environments such as soils, mosses, and lichens, tolerating desiccation and other types of stress such as high doses of ionizing radiation (IR). It was hypothesized that bdelloid desiccation and radiation resistance may be attributed to their potential ability to repair DNA double-strand breaks (DSBs). Here, these properties are investigated and compared among nine bdelloid species collected from both mild and harsh habitats, addressing the correlation between the ability of bdelloid rotifers to survive desiccation and their capacity to repair massive DNA breakage in a phylogenetically explicit context. Our research includes both specimens isolated from habitats that experience frequent desiccation (at least 1 time per generation), and individuals sampled from habitats that rarely or never experienced desiccation.
Results
Our analysis reveals that DNA repair prevails in somatic cells of both desiccation-tolerant and desiccation-sensitive bdelloid species after exposure to X-ray radiation. Species belonging to both categories are able to withstand high doses of ionizing radiation, up to 1000 Gy, without experiencing any negative effects on their survival. However, the fertility of two desiccation-sensitive species, Rotaria macrura and Rotaria rotatoria, was more severely impacted by low doses of radiation than that of desiccation-resistant species. Surprisingly, the radioresistance of desiccation-resistant species is not related to features of their original habitat. Indeed, bdelloids isolated from Atacama Desert or Antarctica were not characterized by a higher radioresistance than species found in more temperate environments.
Conclusions
Tolerance to desiccation and radiation are supported as ancestral features of bdelloid rotifers, with a group of species of the genus Rotaria having lost this trait after colonizing permanent water habitats. Together, our results provide a comprehensive overview of the evolution of desiccation and radiation resistance among bdelloid rotifers.
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