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Gettering and Ion Pumping
Published in Marsbed H. Hablanian, High-Vacuum Technology, 2017
Even if some ion pumps can be started at pressures as high as 10 to 20 millitorr, it is not a good idea to do this too often because of the accelerated exhaustion of the cathodes. The cathodes of an ion pump, which are eroded by sputtering, cannot be regenerated but must be replaced. This replacement is not a simple matter because the pump wall has to be cut open and then rewelded. The cathode life depends on the amount of gas pumped, or the integral of pressure and time. Typical values for diode pumps are 200 h at a constant pressure of 10−4 torr, 2000 h at 10−5 torr, 20,000 h at 10−6 torr, and so on. Note that at 10−6 torr the life is over 2 years and at 10−3 torr only 20 h! For pumping nitrogen only the life of a diode pump at 10−6 torr will be about 50,000 h (5.7 years). Corresponding values for a triode pump are 35,000 h, and for a StarCell pump, 80,000 h.
Evaluation of dosimetric parameters after electron gun and ion pump replacement in linear accelerator device and comparison of results by gATE/Geant4 simulation
Published in Radiation Effects and Defects in Solids, 2023
Turan Şahmaran, Ceyran Yılmaz Koca
This study was conducted at the Department of Radiation Oncology, University of Health Sciences, Ankara Dışkapı Yıldırım Beyazıt Training and Research Hospital. Elekta Synergy (Elekta Synergy, Stockholm, Sweden) linear accelerator is a device that can produce two photons of 6 and 18 MV, and five different electron energies of 6, 9, 12, 15 and 18 MeV. After installing the Elekta Synergy linear accelerator device, the electron gun and ion pump were exchanged due to technical problems. In case of a performance change in the device after this replacement, measurements were taken for the dosimetric evaluation of the device after all calibration settings were made by the technical service, along with the change and assembly. Elekta Synergy Platform Linear Accelerator and three-dimensional water phantom system IBA Blue Phantom2 (IBA Dosimetry; Schwarzenbruck, Germany) were used for these measurements. The water phantom used in the study works under the OmniPro Accept v7 (IBA Dosimetry. Schwarzenbruck. Germany) software program. In experimental measurements, PDD, dose profile and TPR20/10 values were obtained at 6 and 18 MV photon energies.
Solid-state amorphization of gold and silicon bilayer films by annealing
Published in Philosophical Magazine, 2022
Silicon and gold bilayer films were prepared by successive vacuum evaporations at room temperature in a vacuum below 6.6 × 10−5 Pa using a sputter ion pump. Silicon films were deposited with an electron gun, and gold films were deposited with a conical tungsten filament. Three types of bilayer films were prepared. Type A films were polycrystalline gold on amorphous silicon bilayer films (a-Si/Au). Silicon was deposited onto a cleaved NaCl (100) crystal maintained at room temperature to obtain a 20 nm thick amorphous film. Then, the amorphous silicon film was covered with a 15 nm thick polycrystalline gold film during the second evaporation at room temperature. Consequently, the films were deposited without breaking the vacuum. Type B films were polycrystalline gold films on polycrystalline silicon films (c-Si/Au). The crystalline silicon film had a grain size of approximately 50 nm and was formed by the deposition of silicon onto a NaCl (100) crystal maintained at 673 K; subsequently, gold was deposited at room temperature. The thicknesses of the gold and silicon films were 15 and 30 nm, respectively. Type C films were amorphous silicon films on large-grained gold bilayer films (Au/a-Si). A gold film with a large grain size of approximately 300 nm was deposited by evaporation onto a NaCl (100) crystal maintained at 573 K, and then silicon was deposited on the gold film at room temperature. The thickness of both the gold and silicon films was 20 nm.
On loading of a magneto-optical trap on an atom-chip with U-wire quadrupole field
Published in Journal of Modern Optics, 2018
Vivek Singh, V. B. Tiwari, K. A. P. Singh, S. R. Mishra
The experimental setup has an octagonal-shaped vacuum chamber. This octagonal chamber is connected to a six-way cross on top of it using a ∼100-mm-long I-piece. The atom-chip mount system is placed inside the octagonal chamber through this six-way cross such that chip surface is positioned ∼7 mm above the centre of the octagonal chamber. The vacuum pumps (turbo molecular pump (TMP) (77 l/s) and sputter ion pump (SIP) (300 l/s)) are connected to this six-way cross for evacuating the chamber up to Torr. During the U-MOT operation, a current of 40 A is supplied to U-wire in presence of variable bias fields and . The central part of this U-wire has been kept broad (∼10 mm) to get a quadrupole field profile more close to the ideal one (10, 14).