An assessment of the evaporation and condensation phenomena of lithium during the operation of a Li(d,xn) fusion relevant neutron source

Knaster, J.; Kanemura, Takuji; Kondo, Keitaro

doi:10.1016/j.heliyon.2016.e00199

Cited by 10 publications

(5 citation statements)

References 49 publications

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“…Recent experiments related with the Facility for Rare Isotope Beams developed in the Argonne National Laboratory [121] have shown that flowing lithium can work in supersaturated conditions even with beam power densities four orders of magnitude above the 1 GW m −2 that the IFMIF Li target will experience. In addition, vaporization tests developed in the ELTL [96] have confirmed the validity of Herz-Knudsen-Langmuir analytical expressions to estimate the vaporization of Li during operation of the IFMIF (see section 3.2) [96,98].…”

Section: Discussionmentioning

confidence: 61%

“…Vaporization rates are not a concern; a clear understanding of the behaviour has been obtained in specific tests carried out in ELTL [96] overcoming older confusing results [97]. Further, it has been demonstrated that the Hertz-Knudsen-Langmuir equation with η = 1.66 Schrage's accommodation factor is suitable for simple analytical calculations of the expected vaporization phenomena with an assessment for the IFMIF [98].…”

Section: Stability Of the LI Screen Absorbing The 2 × 5 Mw Beam Power...mentioning

confidence: 99%

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Overview of the IFMIF/EVEDA project

Knaster¹,

Garin

Matsumoto

et al. 2017

Nucl. Fusion

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IFMIF, the International Fusion Materials Irradiation Facility, is presently in its engineering validation and engineering design activities (EVEDA) phase under the Broader Approach Agreement. The engineering design activity (EDA) phase was successfully accomplished within the allocated time. The engineering validation activity (EVA) phase has focused on validating the Accelerator Facility (AF), the Target Facility and the Test Facility (TF) by constructing prototypes. The ELTL at JAEA, Oarai successfully demonstrated the long-term stability of a Li flow under the IFMIF’s nominal operational conditions keeping the specified free-surface fluctuations below ±1 mm in a continuous manner for 25 d. A full-scale prototype of the high flux test module (HFTM) was successfully tested in the HELOKA loop (KIT, Karlsruhe), where it was demonstrated that the irradiation temperature can be set individually and kept uniform. LIPAc, designed and constructed in European labs under the coordination of F4E, presently under installation and commissioning in the Rokkasho Fusion Institute, aims at validating the concept of IFMIF accelerators with a D+ beam of 125 mA continuous wave (CW) and 9 MeV. The commissioning phases of the H+/D+ beams at 100 keV are progressing and should be concluded in 2017; in turn, the commissioning of the 5 MeV beam is due to start during 2017. The D+ beam through the superconducting cavities is expected to be achieved within the Broader Approach Agreement time frame with the superconducting cryomodule being assembled in Rokkasho. The realisation of a fusion-relevant neutron source is a necessary step for the successful development of fusion. The ongoing success of the IFMIF/EVEDA involves ruling out concerns about potential technical showstoppers which were raised in the past. Thus, a situation has emerged where soon steps towards constructing a Li(d,xn) fusion-relevant neutron source could be taken, which is also justified in the light of costs which are marginal to those of a fusion plant.

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Section: Discussionmentioning

confidence: 61%

Section: Stability Of the LI Screen Absorbing The 2 × 5 Mw Beam Power...mentioning

confidence: 99%

Overview of the IFMIF/EVEDA project

Knaster¹,

Garin

Matsumoto

et al. 2017

Nucl. Fusion

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“…The geometry of the vacuum chamber and lithium's low room-temperature vapor pressure prevent any lithium from reaching the ion gauge: the optimal path from the viewport to the gauge still requires five collisions with the walls of the vacuum chamber. The sticking coefficient of Li on stainless steel and Li is 1 to an excellent approximation [40][41][42][43][44], so we conservatively estimate that the probability for a lithium atom to reach the ion gauge is 10 −10 . Additionally, when lithium was initially deposited onto the viewport from the dispenser, a turbomolecular pump and a residual gas analyzer (RGA) were attached to the vacuum chamber near the ion gauge.…”

Section: Resultsmentioning

confidence: 99%

Light-induced atomic desorption of lithium

et al. 2018

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We demonstrate loading of a Li magneto-optical trap using light-induced atomic desorption. The magnetooptical trap confines up to approximately 4 × 104 7Li atoms with loading rates up to approximately 4 × 103 atoms per second. We study the Li desorption rate as a function of the desorption wavelength and power. The extracted wavelength threshold for desorption of Li from fused silica is approximately 470 nm. In addition to desorption of lithium, we observe light-induced desorption of background gas molecules. The vacuum pressure increase due to the desorbed background molecules is ≲ 50 % and the vacuum pressure decreases back to its base value with characteristic timescales on the order of seconds when we extinguish the desorption light. By examining both the loading and decay curves of the magneto-optical trap, we are able to disentangle the trap decay rates due to background gases and desorbed lithium. Our results show that light-induced atomic desorption can be a viable Li vapor source for compact devices and sensors.

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“…where m Li is the mass of an atom and k b is the Boltzmann constant [23]. Equilibrium vapor pressure p ν (T) data for solid and liquid elements was compiled by Honig and Kramer in [24].…”

Section: Appendix A: Lithium Evaporation From a Cpsmentioning

confidence: 99%

“…At first glance, Γ is just a complicated function of surface temperature T(t, z). However, the premise of a half-Maxwellian velocity distribution at the liquid-gas boundary implies the free expansion of unbound non-interacting particles [23]. This excludes the effect of collisions, the presence of impurities or the action of capillary forces in the effective rate of evaporation.…”

Section: Appendix A: Lithium Evaporation From a Cpsmentioning

confidence: 99%

Boron synergies in lithium film performance

Devitre

Oyarzábal²,

Fernández-Berceruelo³

et al. 2020

Nucl. Fusion

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Fusion experiments use lithium and boron getters to capture impurities and control the density of fuel species in the plasma. In the TJ-II Stellarator, the addition of a boron-carbon substrate was found to extend the lifetime of the very reactive lithium wall conditioning. However, the synergies between the lithium layer and the underlying boron-carbon, or the effect of a glow discharge cleaning, on oxygen and deuterium gettering are not fully understood. Laboratory experiments were therefore initiated to gain deeper insight on the getter properties of B(C)/Li walls. The coatings were exposed to oxygen gas and plasmas while the capture and release of O was followed by mass spectrometry. Without the boron substrate, the maximum oxygen uptake is half the number of lithium atoms in the film for both oxygen gas and oxygen plasma. Conversely, the behaviour of B(C)/Li walls depends on the nature of the oxidation process: molecular oxygen (O:Li ≈ 0.15) or plasma (O:Li ≈ 0.50). The oxygen plasma gettering is thus preserved against molecular oxidation, e.g. an overnight exposure to the residual gas. While oxygen is known to promote hydrogen retention in lithium, the oxygen content of a B(C)/Li coating shows little effect on deuterium retention. Unlike simple lithium, the oxygen and deuterium gettering of B(C)/Li recovers after a helium glow discharge treatment. These advantageous features clearly point to a change in chemistry, with complex interactions between film constituents and the oxygen-rich environment of magnetic fusion devices.

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An assessment of the evaporation and condensation phenomena of lithium during the operation of a Li(d,xn) fusion relevant neutron source

Cited by 10 publications

References 49 publications

Overview of the IFMIF/EVEDA project

Overview of the IFMIF/EVEDA project

Light-induced atomic desorption of lithium

Boron synergies in lithium film performance

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