Hi, recently I have been using some dosimeters to measure radiation sources (No worries everything is done safely) apart from the confusion that arises due to the different measurement systems used across the world, some older ones use Roentgens while newer ones are mostly Sieverts , and when using an older dosimeter I have to constantly recalculate to sievert because I'm more used to that scale. Heres a few things I would love to know.I would like to state a few things and you could tell me where i'm wrong and where i'm correct. Overall there's two types of radiation (not including gravitational or other forms) , particle radiation like electrons , positrons , neutrons etc , and electromagnetic radiation which is photons and comes in all frequency ranges from very low radio to THz.The frequency of EM radiation also then divides it into non ionizing (lower frequency , less powerful per photon) and ionizing (higher frequency more powerful per photon) Now is particle radiation also ionizing at higher energies, or is only EM radiation (photons) ionizing ? From what I understand both photons and elementary particles with mass (like electrons for example) can be ionizing it all depends on their energy, the difference being that photons can penetrate far deeper into a medium but electrons cannot and I assume its because photons have no mass or charge so their almost transparent while high energy electrons for example get "trapped" soon due to their charge and mass which makes them interact with nearby atoms? Also I want to clear another confusion that I have had for a while.I read wikipedia and other sources and so i gather that the difference between X rays and Beta radiation is that X rays are EM radiation with a specific characteristic frequency range and Beta radiation is the radiation of energetic electrons as particles.or positrons in the Beta+ case.? Another confusion to me , is Beta radiation only coming from nuclear reactions , more specifically radioactive decay or can it also be made by bombarding a metal target with high energy EM radiation like X rays ? I know from the photoelectric effect that if a sufficiently high frequency photon hits a metal target it knocks out an electron whose energy corresponds to the input energy of the photon.So from this the question about Beta radiation arises for me. And the last question for this post would be like this.I was in a nuclear reactor while ago and from what i observed and understand is that alpha particles are of little concern if not directly swallowed or otherwise put inside , since they are easily absorbed by skin and other thin materials. Beta goes deeper and has higher energies I assume but can also be stopped by fairly thin and lightweight materials. The biggest concern is Gamma photons and neutrons I suppose , which would explain why the reactor has very thick lead treated glass window through which the crew looks at the moment the spent fuel assemblies are taken out of the core. Neutrons seem to be the only ones that can activate a material which itself wasn't radioactive before or cannot be such naturally.I assume this is because a neutron has the ability to change an atoms nucleus while other forms of radiation like Gamma no matter how strong can only interact with an atoms electrons.? One last question about gamma absorption , why it requires very dense and thick materials to stop it?Is it because of the massless and chargeless nature of the photon so it travels some distance through the material unaffected and then when it finally interacts with the medium it travels through, it causes some secondary emission and isn't easily stopped with the first time? Like it interacts with an electron through the photoelectric effect and then the ejected electron further interacts , only I suppose the secondary emitted electrons or electron positron pairs have a much higher chance and less time and distance to interact with the medium than the incoming photon that created them. Thank you for your time.