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SNS Wire Scanner Preliminary Design Review. Heating Calculations. By C.J. Liaw, BNL July 24, 2002. Wire Heating in the HEBT. Carbon wire size: 32 m m dia. Beam parameters: *1 GeV H - beam, Gaussian Distributed *1 MW~ 2 MW, 60 Hz, 1 ms long
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SNS Wire Scanner Preliminary Design Review Heating Calculations By C.J. Liaw, BNL July 24, 2002
Wire Heating in the HEBT Carbon wire size: 32 mm dia. Beam parameters: *1 GeV H- beam, Gaussian Distributed *1 MW~ 2 MW, 60 Hz, 1 ms long * Beam current, I = 16 ~ 32 mA over a pulse Min. beam size: 1.4 mm x 1.4 mm ( sx x sy) Mean wire thk.:x= pd/4 =.0025 [cm] Power deposition: P= [(1/r dE/dx)p+ 2*(1/r dE/dx)e] rx* Imax/2psxsy [W/m2] Heating efficiency: h =.82
Wire Heating in the Ring Carbon wire size: 32 mm dia. Beam parameters: *1 GeV, 1 ~ 2 MW, 60 Hz proton beam *Injected 1000 bunches in 1 ms before extraction * Beam current, I = from 0 to 16 A in 1 ms (1 MW case) = from 0 to 32 A in 1 ms (2 MW case) Eff. beam size: A=6.45 x 10-6+3.09 *t [m2], where t =time [sec] Mean wire thk.:x= pd/4 =.0025 [cm] Power deposition: P= (1/r dE/dx)*rx* (Imax*t/1x10-3)/A = 1.27 x 108(t/A) [W/m2] (for 1 MW case) = 2.54 x 108(t/A) [W/m2] (for 2 MW case) Heating efficiency: h =.82
Wire Heating in the RTBT Carbon wire size: 32 mm dia. Beam parameters: *1 GeV proton beam, quasi-uniform distributed *1~ 2 MW, 60 Hz, 695 ns long * Ave. beam current, I = 23 A over a pulse (1 MW case) = 46 A over a pulse (2 MW case) * Max. beam current, Imax = I *1.25 Min. beam size: 56 mm x 68 mm ( H x V) Mean wire thk.:x= pd/4 =.0025 [cm] Power deposition: P= (1/r dE/dx)prx* Imax/ (H*V) [W/m2] Heating efficiency: h =.82
Governing Equation dT/dt = 4(rpdc)(Ph-pse(T4-T04)) where T = wire temperature [K] To = beam pipe temperature = 297 [K] d = diameter of the wire [m] t = time [sec] h= heating efficiency s = Stefan Boltzmann constant = 5.67 x 10-8 [W/m2K4] r = density =2000 kg/m3 e= emissivity =0.8
Maximum Wire temperature in the HEBT, the Ring, and the RTBT (One MW Case)
Maximum Wire temperature in the HEBT, the Ring, and the RTBT (Two MW Case)