Try the aladin data base: http://www-amdis.iaea.org/ALADDIN/
Select heavy particle collision Reactant D product T Data quantity cross section or differential cross section Data type Or this paper: theoretical Go to data selection select one source Go to numerical data
You are donehttp://fds.oup.com/www.oup.co.uk/pdf/0-19-856264-0.pdf
Cross sections are crudely speaking the surface interaction (billard ball interaction), the bigest the particle, the higher the cross section, so one can not say things like "cross section of ion-ion fusion is much lower than ion-atom and atom-atom", it really depends on the species you study. One can not give a single value for cross sections because they are energy dependant.
The ITER project goals have been downgraded with the budgets. Breakeven is no longer an objective. At most they want to demonstrate they have the technology for the next big machine. The problem of the fusion community is that they have been lying for the last 50 years, always promising politicians a working fusion reactor if only they were getting the money to build it. But after every increase in size of the reactor they have discovered new instabilities they had not forseen. They nevertheless kept extrapoling results to convince the financiers. In fusion plasma physics a 50% margin between theory and experiment is considered as a great achievement. Concerning ITER, they are going to use beryllium (extremely toxic) to shield the wall, something which has never been done elsewhere. There is also the problem of the tritium production. They want to use a lithium blanket on the wall to produce tritium that will be burned into the reactor. If it does not work as expected, exit ITER, because there is currently only 30 kg of tritium available on earth and the nuclear plant which used to produce it is now closed (Canada). At last there is the energy and neutron fluxes on the walls. Current Tokamaks run 10s pulses. ITER is supposed to run a 500 GW, 10 min pulses. There is no known materials which can handle that. If there is a problem, with the toxic beryllium blanket, it will be a difficult one to solve.