Numerical simulation of experimental tests performed on ZAO® non-evaporable-getter pump designed for neutral beam injector applications

Siragusa, M.; Sartori, E.; Mura, M.; Siviero, F.

doi:10.1063/1.5128662

Cited by 10 publications

(7 citation statements)

References 7 publications

(7 reference statements)

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“…The installed pumping speed (about 100 m 3 /s) turned out to be insufficient to such purpose. The SPIDER pumping system is being improved with the addition of non-evaporable getter (NEG) pumps [9] [10]. In the meantime, to allow the experimentation, most of the plasma grid apertures were masked by a thin molybdenum layer so as to limit the required gas flow to operate the source at 0.3-0.4 Pa without overcoming p limit [11].…”

Section: The First Operations In Spidermentioning

confidence: 99%

Optimizing the ITER NBI ion source by dedicated RF driver test stand

Mario,

Pimazzoni,

Sartori

et al. 2024

J. Phys.: Conf. Ser.

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The experimental fusion reactor ITER will feature two (or three) heating neutral beam injectors (NBI) capable of delivering 33(or 50) MW of power into the plasma. A NBI consists of a plasma source for production of negative ions (extracted negative ion current up to 329 A/m2 in H and 285 A/m2 in D) then accelerated up to 1 MeV for one hour. The negative ion beam is neutralized, and the residual ions are electrostatically removed before injection. The beamline was designed for a beam divergence between 3 and 7 mrad. The ion source in ITER NBIs relies on RF-driven, Inductively-Coupled Plasmas (ICP), based on the prototypes developed at IPP Garching; RF-driven negative-ion beam sources have never been employed in fusion devices up to now. The recent results of SPIDER, the full size ITER NBI ion source operating at NBTF in Consorzio RFX, Padova, measure a beamlet divergence minimum of 12mrad and highlighted beam spatial non-uniformity. SPIDER results confirmed the experimental divergence found in smaller prototype sources, which is larger compared to filament-arc ion sources. Although prototype experiments have shown that the extracted current requirement can be achieved with minor design improvements, the beamlet divergence is expected to marginally achieve the design value of 7 mrad, which in multi-grid long accelerators results in unexpected heat loads over the accelerator grids. A contributor to the beam divergence is the energy/temperature of the extracted negative ions, so it is believed that plasma differences between the two source types play a role. Research is focused on the plasma parameters in the ion source. One RF driver, identical to the ones used in SPIDER, installed in a relatively small-scale experimental set-up, inherently more flexible than large devices, is starting operations devoted to the investigation of the properties of RF-generated plasmas, so as to contribute to the assessment of negative ion precursors, and of their relationship with the plasma parameters, particularly when enhancing plasma confinement. The scientific questions, that have arisen from the preliminary results of SPIDER, guided the design of the test stand, which are described in this contribution, together with the diagnostic systems and related simulation tools. The test stand, which shares with the larger experiment all the geometrical features and constraints, will allow technological developments and optimized engineering solutions related to the ICP design for the ITER NBIs.

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Section: The First Operations In Spidermentioning

confidence: 99%

Optimizing the ITER NBI ion source by dedicated RF driver test stand

Mario,

Pimazzoni,

Sartori

et al. 2024

J. Phys.: Conf. Ser.

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“…may passivate the getter surface and therefore reduce the pumping speed for H 2 . A detailed description of the model used is available in [16].…”

Section: Evaluations On the Application Of Neg Pumps In Dtt Nbimentioning

confidence: 99%

“…Figure 5: Pumping speed of a ZAO NEG pump: (a) pumping speed as a function of hydrogen concentration, measured on the prototype described in [18]; (b) model to calculate the capture coefficient with the presently considered layout of NEG cartridges in DTT NBI. Q is the throughput measured in Pa m 3 s −1 , while Qtilde is the specific throughput (or throughput per unit of area) measured in Pa m s −1 .A detailed description of the model used is available in[16].…”

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confidence: 99%

Conceptual design of the Gas Injection and Vacuum System for DTT NBI

Agostinetti

Bello

Dinh

et al. 2023

Fusion Engineering and Design

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“…Furthermore, the promised capacity is not exploitable if a considerable fraction of disks is not reached by the gas. Consequently, several simulations were performed to study all of these dependencies of the three different arrangements [7], as summarized in the following.…”

Section: Arrangement Selectionmentioning

confidence: 99%

Experimental Characterization of an NEG Pump of Novel Size—A Major Step toward Its Application in DEMO Neutral Beam Injectors

et al. 2023

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A future nuclear fusion plant DEMO needs neutral beam injection (NBI) systems requiring a vacuum pumping system with a very high pumping speed, in the order of several 1000 m3/s. Large customized cryopumps are actually used to meet the requirements. A promising concept for future NBI systems is based on high capacity getter materials. The ZAO® alloy, developed by SAES Getters, Italy, provides a drastically improved performance for the pumping of hydrogen compared to conventional getter materials. This paper describes the experimental characterization of a large pump of scalable size with 15 kg of ZAO® and the achieved results, in particular the systematic investigation of sorption characteristics and regeneration behaviors. Major findings include a very good repeatability of the sorption performance, a reduced pumping speed at higher pressures only above the NBI relevant level, an improved performance (+20%) with elevated getter temperature and an isotope independent sticking coefficient for hydrogen. Furthermore, improved operation experience and regeneration prediction tools have been developed. Employing the experimental results, a simulation task was performed and the sticking factor of the getter cartridge was determined with 7%.

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Numerical simulation of experimental tests performed on ZAO® non-evaporable-getter pump designed for neutral beam injector applications

Cited by 10 publications

References 7 publications

Optimizing the ITER NBI ion source by dedicated RF driver test stand

Optimizing the ITER NBI ion source by dedicated RF driver test stand

Conceptual design of the Gas Injection and Vacuum System for DTT NBI

Experimental Characterization of an NEG Pump of Novel Size—A Major Step toward Its Application in DEMO Neutral Beam Injectors

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