Cryogenic target with very thin “gold finger” heat pipe

An extremely light stainless steel heat pipe of 0.1 mm wall thickness and 5 mm diameter has been developed to transport heat from the liquid hydrogen/deuterium target to the cooling machine. As a further improvement an important reduction of the heat load to the cold parts of the system is achieved by coating the heat pipe and the target finger with a thin polished gold layer. This brings the radiation heat load from 1400 mW on the non-isolated stainless steel surface system down to 70 mW on the gold-coated system. A further reduction to 0.05 mW is achieved by using an aluminum heat shield at 50 K around the cold parts at 15 K. Finally, the heat load was further reduced by a factor 11, without changing the geometry, by coating both sides of the aluminum shield with a thin gold mirror layer. This new, very slim “gold finger” target system shows safe and stable performance even with a low power-cooling machine.