In ITER, magnetic fusion will explore the burning plasma regime. Because such burning plasma is sustained by its own fusion reactions, alpha particles need to be confined (Hazeltine 2010 Fusion Eng. Des.7–9 85). New experiments using d(3He,p)α and d(d,p)t fusion reaction products were performed in JET. Fusion product loss was measured from MHD-quiescent plasmas with a charged particle activation probe installed at a position opposite to the magnetic field ion gradient drift (see figure 1)—1.77 m above mid-plane—in the ceiling of JET tokamak. This new kind of escaping ion detector (Bonheure et al 2008 Fusion Sci. Technol.53 806) provides for absolutely calibrated measurements. Both the mechanism and the magnitude of the loss are dealt with by this research. Careful analysis shows measured loss is in quantitative agreement with predictions from the classical orbit loss model. However, the comparison with simulated loss radial profile, although improved compared with previous studies in TFTR, Princeton, US (Zweben et al 2000 Nucl. Fusion40 91), is not fully satisfactory and potential explanations for this discrepancy are examined.
ITERにおいて、磁場閉じ込め核融合は燃焼プラズマ領域を探求する。このような燃焼プラズマは自身の核融合反応によって維持されるため、アルファ粒子の閉じ込めが必要となる（Hazeltine 2010 Fusion Eng. Des.7–9 85）。JETにおいて、d(3He,p)αおよびd(d,p)t核融合反応生成物を用いた新たな実験が実施された。核融合生成物の損失は、磁場勾配ドリフトに対して反対側の位置（図1参照）—JETトカマクの天井から1.77 m上方—に設置された荷電粒子放射化プローブを用いて、MHD静穏プラズマから測定された。この新型のエスケープイオン検出器（Bonheure et al 2008 Fusion Sci. Technol.53 806）は、絶対校正された測定を可能にする。本研