Static thermal analysis and experimental evaluation of heat-pipe oven for plasma Wakefield accelerator experiment

The heat-pipe oven described here is used for the generation of uniform temperature lithium vapour column in a Plasma Wakefield Accelerator (PWFA) experiment system. The PWFA experiment is being pursued at the Institute for Plasma Research as part of the basic plasma research activities. A 50 MeV, short pulse, high brightness electron Linac is also planned to be set up at IPR for this experiment. In a PWFA experiment, a bunch of ultra-short (3ps) electrons will be injected into a homogenous plasma of density 1013-1014 cm-3 where the head of the electron bunch would create a wake in the plasma and electrons in the tail of the bunch are subjected to high acceleration gradients generated by electrons trapped in the wake. Lithium vapour will be generated in a heat-pipe oven in order to produce uniform vapour densities to generate the plasma. The heat-pipe oven consists of a stainless steel tube wrapped over by a heater section, 400 mm in length, along its central part and cooled with cold water jackets placed symmetrically at either ends from the Center. A stainless steel mesh tube 'wick' of thickness 2 mm encircling the inner wall of the tube is placed extending up to the cooling jacket. It creates a uniform column of lithium vapour, bound by helium buffer gas. Finite Volume Analysis (FVA) based simulation studies for the temperature profile of the system were carried out with and without lithium in the system and their results compared to experimentally obtained data. Simulations were carried out by applying convection boundary conditions on geometrically well-defined longitudinal sections of the heat-pipe oven. Different correlations have been used to obtain heat transfer coefficients which are required in the simulation. (author)