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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title MICROWAVE SOURCE Device for ƚŚĞ ƌĞĚƵĐƟŽn of back sĐĂƩĞred rays from a load subũĞĐƚĞd ƚo microwave radiĂƟon by a source (pre-load). DEVICE Ref. CNR 1629 Assignee(s): CNR LOAD CNR InsƟƚute: IFP Main Inventor: Sante Giovanni Cirant Countries: IT Priority date: 30/08/2004 Abstract /ƚ is common pƌĂĐƟce, while developing and using powerful microwave sources, ƚo use a caviƚLJ (“load”) in order ƚo absorb ƚhe ŐĞŶĞƌĂƚĞd power and in some cases ƚŽ provide a measure of ƚhe absorbed power (“bolŽŵĞƚƌic load”). The microwaves, in shape of ĐŽŶĐĞŶƚƌĂƚĞd beam, are ŝŶũĞĐƚĞĚ in ƚŚĞ load ƚŚƌough an appropriĂƚĞ opening. An elevĂƚĞd reŇecƟon, beyond ƚŽ being harmful for ƚŚĞ source, in ƚŚĞ bolŽŵĞƚƌic load case does noƚ allow an accuƌĂƚĞ measure. The developed device is consƟƚuƚĞd from a ŵĞƚĂllic body ǁŝƚŚ passing ĐĂǀŝƚy and convenieŶƚ inner geomeƚry (opposŝƚe cone secƟons), such ŶŽƚ ƚŽ block a microwave beam incoming in a load bƵƚ ƚo suppress ƚhe reŇecƚĞd radiĂƟon ƚowards ƚhe source. ThĂƚ is possible because ƚŚĞ microwave ƌĂĚŝĂƟon inside ƚŚĞ load ƌĞŇeĐƚƐ ǁŝƚŚ a greaƚ angular dispersion Ăƚ ƚŚe mouƚh of ƚhe load. Background In ƚŚe developmenƚ of microwave absorbing loads, due ƚŽ ƚŚe geomeƚry of ƚhe sysƚem, a cerƚĂŝŶ frĂĐƟŽn of ƚŚe bouncing rĂĚŝĂƟŽn can escape from ƚhe load eŶƚrance͗ depending on ƚhe chĂƌĂĐƚĞƌisƟcs of ƚhe load, up ƚŽ 10% of ƚŚe power can be reŇecƚed aƚ angles greaƚer ƚŚĂn 40° from ƚhe axis of symmeƚry. Safe operĂƟŽn of high power sources asks for overall reŇecƟŽŶƐ from ƚŚe load lower ƚŚĂn abouƚ 1%. In order ƚŽ reduce ƚŚis ĂŵŽƵŶƚ, an edžƚernal preload is added in fƌŽŶƚ of ƚŚe load. Technology The preload inner surface is consƟƚƵƚĞd by a corner-cube arrangemenƚ capable ƚŽ reŇĞĐƚ back ŝŶƚŽ ƚŚĞ load all ƚŚe rays coming ŽƵƚ aƚ a large angle while ŶŽƚ ŝŶƚerfering ǁŝƚh ƚŚe incoming beam. The developed device can individually be obƚained by mechanical working from a single block of meƚĂů and inner ƚurning or assembling single worked seĐƟŽŶƐ͗ in ƚŚĞ Įƌsƚ case ƚŚĞ device is vacuum ĐŽŵƉĂƟďůĞ and can also be used in order ƚo pump down ƚhe sysƚem. Advantages and ApplicaƟons tŝƚhouƚ preload, a load can reŇeĐƚ up ƚŽ 10% of ƚŚe injecƚed power. The developed accessory can reduce ƚŚĞ ƌĞŇĞĐƟŽŶ ĚŽǁŶ ƚŽ ϭй͕ ŝŵƉƌŽǀŝŶŐ ƚŚĞ ŽƉĞƌĂƟŽŶ ŽĨ Ă ůŽĂĚ ĨŽƌ ƚŚĞ ĂďƐŽƌƉƟŽŶ ĂŶĚ ƚŚĞ ŵĞĂƐƵƌĞ ŽĨ powerful microwave beams. /ƚ is useful in all ƚhe Įelds ƚhĂƚ demand use and/or developmeŶƚ of powerful microwave sources, ǁŝƚh frequency of 100÷200 GHz and power of 1÷2 ŵĞŐĂǁĂƩ. Development stage Devices for use under vacuum and in air have been developed and applied ƚŽ loads buŝůƚ for European laboraƚories working on ƚhe developmenƚ of high-power microwave sources and on microwave ŚĞĂƟŶŐ of plasmas for apƉůŝĐĂƟŽn ƚŽ Nuclear Fusion research. 15