Molecular (H/D/T) sources in JET

Abstract

Molecular Fulcher-a spectroscopy is used for the investigation of the HD and DT molecule formation in JET during H 2 and T 2 puffs, respectively. In the hydrogen case, the HD fraction in the outer divertor was about 10% of the molecular D 2 flux, resulting in a 1% contribution of H 2 to the D 2 flux using the law of mass action which is a very sensitive means to measure low quantities of H 2 or T 2 respectively via the detection of the isotopomeres HD and DT. Since the puffed tritium was about one order of magnitude smaller than the H flux introduced, a DT-flux of only $1% is expected, resulting in a T 2 flux of 0.1%. Evidence will be presented that similar levels have indeed been detected, although the signals were near the detection limit, demonstrating that this type of spectroscopy offers an interesting potential tool as a fuelling and recycling rate diagnostic.

Lyman transitions of high rovibrationally excited H2, HD and D2 molecules

“…The wavelength range lower than 110-115 nm is not accessible due to the non-availability of transparent windows in this spectral range. Thus, the Lyman transitions detected by this spectroscopic setup are limited to transitions of hydrogen molecules with internal excitations higher than about 1 eV, i.e., (v, J) > (2, 5) in case of H 2 , (v, J) > (2,9) in case of HD and (v, J) > (4,9) in case of D 2 .…”

“…In experimental fusion reactors, when driven by mixtures of H 2 and D 2 , HD and D 2 molecules were found as recombination products in the cooler regions, i.e., in front of surfaces exposed to the plasma core [7][8][9]. While in space only the lowest rovibrational states of molecular hydrogen are occupied due to the low temperature, hydrogen molecules can be excited to high vibrational v and rotational J states in technological plasmas [7,8,10].…”

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

“…For example Hollmann et al have detected extermely hot D 2 molecules in the DIII-D reactor from their spectroscopic signatures [8]. Similarly Pospieszczyk et al investigated various hydrogen molecular isotopomers in the JET fusion reactor [9].…”

Nondissociative electron and photon ionization cross sections of molecular hydrogen and deuterium

“…In tokamak discharges, H 2 and its isotopic counterparts are the main fuelling species, primarily generated from plasma recycling on the vessel walls and from gas puffing. Measurements of molecular and atomic hydrogen and their isotopes have been obtained in DIII-D (Hollmann et al 2006), JET (Keilhacker et al 1999, Pospieszczyk et al 2007 and TEXTOR (Brezinsek et al 2003). Since the spatial distribution of atomic and molecular hydrogen in the plasma edge plays an important role in plasma processes, accurate cross sections are needed to characterize the production and destruction reactions that determine the spatial distributions.…”