The thermal defect of A-150 plastic and graphite for low-energy protons

The thermal defects of A-150 plastic and graphite referenced to aluminium were determined for 800 keV protons scattered by a 2 micron nickel foil (mean transmitted energy = 550 keV). Composite cores of Al/A-150, graphite/A-150 and Al/graphite which could be irradiated from one side or the other were employed. The temperature increase of a core caused by 30-100 s of irradiation (3-6 nA of proton beam current) was detected by two thermistors mounted in opposite legs of a Wheatstone bridge. The thermal defect of A-150 plastic was determined to be 0.0421 +/- 0.0036 (SE) referenced to aluminium and 0.0402 +/- 0.0034 referenced to graphite. The thermal defect of graphite referenced to aluminium is 0.0043 +/- 0.0034. No change in the thermal defect of A-150 plastic was detected for accumulated doses up to 8 x 10(5) Gy.