Abstract: An epitaxial reactor with a flat disc-shaped susceptor comprises a flat, substantially tubular quartz reaction chamber (12) containing a rotatable susceptor disk (14) having a plurality of recesses (16a-h) for housing a corresponding plurality of disc-shaped wafers (18a-h) of material to be processed, a tank (26) filled with flowing coolant liquid (28) surrounding the substantially tubular chamber (12), a primary supply inductor (90) substantially in the form of a flat spiral disposed outside the reaction chamber (12) in the lower portion of the tank (26) parallel to the susceptor disc (14) and having means (118) for modifying the distance between each individual turn of the primary inductor (90) and the susceptor disc, possibly a secondary inductor (102) formed by turns disposed parallel and closely coupled to the turns of the primary inductor (90), possibly means (158) for selectively connecting each turn of the primary inductor (90) to external loads according to a known technique or for selectively closin