I don't think there is a special name for it, so I suggest you just call it "a large crucifix".
Rood
Crucifix
the crucifix
it's called a crucifix
The Holy Crucifix
A niche is a recess in a wall which often contains a statue. A church could certainly have a niche that holds a crucifix. A niche need not be in a church.An apse is a large recess at one end of a church. If often contains an altar or statuary and is its walls are covered by paintings or carvings or other artwork. A large crucifix is a possible central figure for an apse. An apse is a term for a part of a church but it need not hold a crucifix.
A crucifix in the chancel is often referred to as a "chancel crucifix" or "altar crucifix." It is a representation of Jesus on the cross, typically displayed prominently in the church's chancel area, serving as a focal point for worship and reflection. This symbol emphasizes the central message of Christianity regarding the crucifixion and resurrection of Jesus.
A 'T' shape could be called a cross, and in a religious manner, a crucifix.
A crucifix is a representation of Jesus on the cross. The crucifix is used mainly in the Roman Catholic church.
The Pope holds a Holy Crucifix or 'sceptre'. It is officially called a 'Pastoral Staff' pr Crosier with the Crucifix mounted atop of it. Though it is not required, he believes it has spiritual influence and symbolizes might or power.
The CATHOLIC DENOMINATION uses the CRUCIFIX.
You can buy a crucifix at any Catholic gift shop.