When Kundalini reaches over the crown chakra do we then become aware of our light body?
What is the body of light?
Is it a soul we travel in then?
This depends on what you mean by Light Body. You can Astrally Project (for example) prior to any kind of Kundalini or Energy awakening. Some people call this the light body. When Kundalini awakens, or when you awaken your internal energy through the practices of Tummo you become aware of the chakras, channels, drops, energies. Some people have called that the light body. Or when you realize the ultimate nature of reality, and all your sense of self and other evaporates, the internal winds and energies come to stillness, the body becomes as though it is made of space, and realization dawns in your mind. Some people have said that this is the point at which you obtain or become aware of a light body. Others still have said that when you die, if you have achieved completion of the path of cutting through, although you leave your physical body behind, you immediately incarnate into a body of light, go to a pure land, and acheive total realization there. Finally, some say that if you have complete realization of total Buddhahood, that your physical body transforms into light, and they have called that the light body.
As for Kundalini, when it reaches the crown charka, one experiences the great bliss of the union of Siva and Shakti, the primordial non-duality arises in ones mind and, if this is recognized, one is liberated from Samsara and becomes like Siva himself.
As for the light body being a soul, it is not a soul, it is a body. Like our physical body, but composed of subtle energy instead of gross energy (matter). Regardless of which light body you are referring to. Some of them are more permanent than others, but they are all impermanent (at least according to my understanding, which is feeble and limited).