Not much is known about the second Neutron except that he was recruited into the Imperial Guard, after the original Neutron had been killed during the events of Realm of Kings.
The new Neutron was created by Dan Abnett, Andy Lanning and Kevin Walken and first appeared in Realm of Kings: Imperial Guard issue 5 (2009).
Major Story Arcs
A Legacy to Fullfill
The new Neutron had almost the same powers as the original. More recently, Neutron was part of the group of Imperial Guards that brought down Thanos. He also fought during the Asgard/ Shi'ar war.