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Extreme High Vacuum
Published in Pramod K. Naik, Vacuum, 2018
interior of a stainless steel system with a thin (~1 µm) film of getter material. Ti, Zr, V and their binary alloys have been used as getter materials. The coated surface is transformed from a gas source to a pump by an in-situ bakeout at temperatures of 250–300°C. Pressure of 10 –11 Pa has been produced by using this method. Cryo-condensation and cryo-sorption types of pumps also find application in XHV. Historically, there are instances when XHV pressures were possibly attained 10,11 in relatively small systems in experimental research work using cryo-condensation but could not be measured due to lack of measurement capabilities. Tsukui et al 12 evacuated the main analysis chamber by a TSP and a cryosorption pump at 4.2 K to obtain the XHV condition that could be maintained for longer than 200 h. The beam pipe in the centre of the superconducting magnet coils of the Large Hadron Collider at CERN is maintained in direct contact with the helium bath at 1.9 K (cold-bore beam pipe) 13. At this temperature, the vacuum chamber wall becomes a very efficient cryo-pump.
Vacuum Tube Principles
Published in Jerry C. Whitaker, Power Vacuum Tubes, 2017
To maintain a high vacuum during the life of the component, power tubes contain a getter device. The name comes from the function of the element: to “get” or trap and hold gases that may exist inside the tube. Materials used for getters include zirconium, cerium, barium, and titanium.
Capture Pumps
Published in Igor Bello, Vacuum and Ultravacuum, 2017
In general, a getter should have the following properties: (i) a getter should have a high reaction rate with as many gases as possible; (ii) a getter should easily be stored before its application; (iii) a getter should not affect negatively the performance of the sealed device; (iv) products of the reaction of the getter and gases should have low saturation pressures at operation temperatures of devices; (v) a getter should not evaporate at its degassing; and (vi) the vaporization temperature of a getter should not be very high.
Modification of Ti foils irradiated by intense heavy ion beams
Published in Radiation Effects and Defects in Solids, 2020
R. N. Sagaidak, F. Sh. Abdullin, O. L. Orelovich
Vacuum conditions are also crucial for the correct determination of sputtering yields since contamination or oxidation of the surface can distort the measured or expected yield. A dynamically clean surface can be only maintained if the sputtering rate is much larger than the adsorption rate of contaminants. A rule of thumb gives an adsorption rate of 10 particles/cm/s at the pressure of 10 mbar (9, 10). This value is much higher than the sputtering rate expected from the Ti window foil surfaces facing to the beam (the pressure in front of the window can vary within mbar during irradiation). The backside of the Ti window foils is in the atmosphere of rarefied hydrogen gas at the pressure of 1.3 mbar (a typical DGFRS condition). We note that titanium is the material with a high getter capacity corresponding to about one atom of hydrogen per atom of Ti. Its getter capacities for nitrogen and oxygen are appreciably lower. Due to a rather high temperature of Ti foils irradiated by an intense HI beam (see Section 4), their getter capacity is active continuously. That is because the diffusion rate of the surface-bound hydrogen atoms into the bulk of the material increases with the temperature [see, for example, (15)].
Assessment of Tritium Release Through Permeation and Natural Leakage in ITER CN HCCB TBS Under Normal Operations
Published in Fusion Science and Technology, 2018
Chang An Chen, Xin Zhou, Zhanlei Wang, Bo Wang, Lingbo Liu, Xin Xiang, Yong Yao, Jiangfeng Song
Tritium in the ceramic breeders will be recovered in time through operating the TES, in which a He-H2 purge gas is used to carry tritiated species (HT, HTO, etc.) above the breeders. Hydrogen isotope gases including tritium will be entrapped by the hydrogen getter bed (depleted uranium or Zr-Co alloy as the hydrogen absorption material) before the impurities like oxygen, nitrogen, and carbon are removed by the reduction bed (Zr-Mn-Fe alloy as the getter). Some components of the TES such as the circulation pump, He-H2 makeup unit, and reduction bed will be housed in the ITER port cell. The others will be located in the ITER tritium plant building (Fig. 2).
Modeling of the HCPB Helium Coolant Purification System for EU-DEMO: Process Simulations of Molecular Sieves and NEG Sorbents
Published in Fusion Science and Technology, 2023
Jonas C. Schwenzer, Alessia Santucci, Christian Day
The preconceptual design phase of the EU-DEMO has identified two technology variants for the CPS (Ref. 4). The first is based on the ITER Test Blanket Module (TBM) CPS, utilizing copper oxide conversion beds and zeolite molecular sieves (ZMSs) (referred to as ZMS variant in the following).5 The second process variant uses non-evaporable getter (NEG) materials for the direct absorption of hydrogen (NEG variant).3Figure 1 shows the process layout for both variants taken as a basis for the process simulation, with the requirements and dimensioning of the systems investigated based on the preconceptual design status thereof described in Refs. 1, 3, and 4.