The SPIDER experiment, part of the Neutral Beam Test Facility (NBTF) at Consorzio RFX (Padua, Italy), is the prototype of the negative ion source for the ITER neutral beam injectors; the source is coupled to a 100 kV three-grid acceleration system. A Beam Emission Spectroscopy (BES) diagnostic was installed in SPIDER to study and optimize energy distribution, aiming, uniformity and divergence of the H-/D- beam extracted from the source. The diagnostic is based on the analysis of the Doppler shifted Hα/Dα light emitted in the interaction between the beam particles and the H2/D2 molecules of the background. In 2019 the BES diagnostic in SPIDER was installed and calibrated, and it allowed to characterize the first hydrogen beams extracted from the SPIDER source, in cesium free conditions. The number of active beamlets composing the beam was reduced from 1280 to 80, affecting the BES diagnostic capabilities. This paper presents the BES diagnostic setup and discusses the first collected results. Under limited extracted current density ($\sim$ 10 A/m^2) and ion energy ($\leq$35 keV), no significant vertical beam deflection caused by the magnetic filter field in the source was detected. In some cases the beamlets were observed to be elongated in horizontal direction; beamlet divergence values down to 20 mrad and 30 mrad e-folding were measured in vertical and horizontal direction, respectively; the intensity of the Doppler shifted radiation was found to be strongly correlated to the beam current and to the beam divergence. The progressive compensation of beamlet deflections (caused by electron suppression filter fields) with increasing voltage in the extraction gap was studied.
Tracing Electron Beams in the Sun's Corona with Radio Dynamic Imaging Spectroscopy
我们报告了分米波长的III型射电爆发（IIIdm型爆发）的观测-超热电子束在低日冕中传播的特征-使用最近升级的Karl G. Jansky甚大阵列（VLA）对于第一次，IIIdm型爆发的成像具有高的时间和频率分辨率在一个广泛的频带，使电子束的轨道在电晕推断。同时硬X射线（HXR）和极紫外线（EUV）的观测，我们表明这些光束从位于低日冕的能量释放网站在低于15微米的高度，并沿着一束离散的磁环向上传播到日冕。我们的观测使沿磁环的等离子体密度的直接测量成为可能，并使我们能够将这些磁环的直径限制在100公里以内。这些过于密集和超薄的环揭示了太阳日冕的基本纤维结构。电子束的脉冲性质，它们对不同磁场线的可访问性，以及由射电观测揭示的磁释放位点的详细结构表明，局部能量释放在时间和空间上是高度碎片化的，支持一个突发重联模型，该模型涉及用于磁能释放和粒子加速的二次磁结构。
