Thermal Analysis Problem
 

I have a problem with an ANSYS simulation. I am trying to simulate a static thermal analysis for heating up a sample holder inside a plasma stream. The problem I have is with the temperature distributiion. The CAD model is hereby:

http://i59.tinypic.com/2whpi13.png

My boundary conditions are:
-Radiation with Epsilon = 0.9 of the complete surfaces of the right body (Carbon with a thermal conductivity of around 0.99 W/m*K)
-Radiation with Epsilon = 0.9 of all surface of the middle body (Insulator with a thermal conductivity of around 0.5 W/m*K)
-Radiation with Epsilon = 0.9 of all surfaces of the left two bodies (Copper with a thermal conductivity of around 400 W/m*K)

-Convection of 200 W/m²*K at 4000 Kelvin applied at the outer shell of all bodies, but only the outer shells of the assembly
-Heat Flow of 644.4 Watt at the front surface of the right body

The Problem is, that I get the following temperature distribution:

http://i62.tinypic.com/6hhisx.png

As you can see the minimum temperature is at the plug between the first and second part. Do you maybe know why that is, or how I can fix this ? Because I would expect a more linearly temperature distributiion inside the holder consisting out of 4 parts.

Thank you very much for your help !

Best Regards
Christian