Comparison of calculated neutral beam shine-through with measured shine-through in DIII-D

A comparison of the calculated shine-through of neutral particle beams in the DIII-D plasma to measured values inferred from the target temperature rise is reported. This provides an opportunity to verify the shine-through calculations and makes them more reliable in those cases where the shine-through cannot be measured. The DIII-D centerpost neutral beam target tiles are safeguarded against excessive beam shine-through by pyrometry and thermocouple (TC) arrays on the tiles. Shine-through beam power is calculated from the measured temperature changes reported by the target tile TC array. These measurements are performed at the beginning of each operational year at DIII-D. Theoretically, the beam energy deposited into the plasma can be expressed as a function of the change in beam density: E_b→p =ε[∫(dt)*∫(dV)*∫(-dsN_b(s))]. The expression for beam density propagating in a plasma is: dN_b(s)/ds=-N_b(s)n(s)σ. Where N_b(s) is the beam particle density, n(s) is the plasma density, σ is the interaction cross section, and ε is the energy per beam particle. The beam energy deposited onto the centerpost (shine-through) is then of the general form: E_cp=ε[∫(dt)*∫(dVN_b(a))], where N_b(a)=A[N_b(0)_e^-(naσ)γ+ C]. Given that a, is the plasma diameter, (na) is the line density, N_b(O) is the initial beam density, where A, C and g are system dependent constants. The line density and uncollided beam density are measured quantities. Values of σ are available in the general literature. Neutral beam energy deposition in a plasma (of known density) is inferred by comparing the results of a series of shine-through measurements for the 1997 campaign at DIII-D to the expected shine-through given by theory