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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: The use of a cylindrical collimator in stead of a square one, for IBA cyclotron. Tl-targets reduces the maximum target current by a factor 1,49. In any case the beam current density on target is limited to 0,493 A.mm-2. Taking into account the (6) beam target geometry, the maximum current density at the collimator cross section area is donne for a gaussian current distribution. The reduction of the thickness of the Cu carrier to 0,5 mm allows the total target current to increased to 495 A (cylindrical collimator) and to 738 A for a square collimator, total target current in case of homogeneous irradiation i.e. a factor of 1,91 higher then when a cylindrical collimator and 2 mm Cu-backing are used. The sophisticated fin-fitted target carrier can be replaced by a simple flat backing: the cross sectional area O equals 0,300 cm2 for a channel width of 2,5 mm, an area that is really equal to that of the fin-fitted version (O = 0,317 cm2). Due to the reduced surface area of the ellipse, the total target current is limited to 495 A. At the collimator outlet plane the maximum current density equals 6,31 A.mm-2. Reducing the Cu backing from 2 mm to 0,5 mm and doubling the flowrate of the coolant allows the current density to be increased by a factor 1,96. At the collimator exit plane the maximum current density equals 9,65 A.mm-2. |
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