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[en] Neutral Beam Injection (NBI) is well established technique for heating tokamak plasma and is used in all fusion research programs. In our Steady state Superconducting Tokamak (SST) machine, neutral hydrogen beam power of 0.5 MW at 30 kV is required to raise plasma ion temperature of ∼ 1 keV. Future upgrade of the SST will require 1.7 MW of H deg at 55 kV. To fulfill this requirement, an ion extractor system (heart of any NBI system) has been designed to extract 35A H+ beam current at 30 kV and of 90 A at 55 kV respectively. In this paper, we have described the physics and ion beam optics study for an ion extraction system suitable for above mentioned long dynamic range of acceleration voltage. The ion beam optics simulation result is used as an input to the engineering design. After fabrication, its performance test has been done. The experimental results are in very good agreement with beam optics simulation. (author)
[en] To raise the ion temperature of ∼ 1 keV in steady state superconducting tokamak (SST-1) plasma, a neutral beam injector (NBI) is provided with neutral hydrogen beam power of 0.5 MW at 30 keV. For upgrade of SST-1, power of 1.7 MW at 55 keV is required. We have designed and fabricated 3 grid accel-decel ion extractor system which will satisfy the requirements for both SST-1 and its upgrade. This paper has described the beam optics design of this ion extractor system and its performance test results done at MARION Test Stand of IPP, Julich, Germany. The test results show the ion extractor system attains in a steady state condition which is essential requirement for long pulse operation of NBI. (author)
[en] Highly charged dust grains immersed in a plasma can exhibit charge fluctuations in response to oscillations in the plasma currents flowing into them. This introduces a new physical effect, namely, the electric charge on the dust particles becomes time dependent and a self-consistent dynamical variable. The consequent modifications in the collective properties of a dusty plasma are investigated. It is shown that these effects lead to dissipative and instability mechanisms for ion waves in the plasma and can lead to interesting applications to many laboratory and astrophysical situations
[en] Neutral Beam Injector (NBI) System is one of the heating systems for Steady state Superconducting Tokamak (SST-1). It is capable of generating a neutral hydrogen beam of power 0.5 MW at 30 kV. NBI system consists of following sub-systems: Ion source, Neutralizer, Deflection Magnet and Magnet Liner (ML), Ion Dump (ID), V-Target (VT), Pre Duct Scraper (PDS), Beam Transmission Duct (BTD) and Shine Through (ST). For better heat removal management purpose all the above sub-systems shall be equipped with Heat Transfer Elements (THE). During beam operation these sub-systems gets heated due to the received heat load which requires to be removed by efficient supplying water. The cooling water system along with the other systems (External Vacuum System, Gas Feed System, Cryogenics System, etc.) will be controlled by NBI Programmable Logic Control (PLC). In this paper instrumentation and its related design for cooling water system is discussed. The work involves flow control valves, transmitters (pressure, temperature and water flow), pH and conductivity meter signals and its interface with the NBI PLC. All the analog input, analog output, digital input and digital output signals from the cooling water system will be isolated and then fed to the NBI PLC. Graphical Users Interface (GUI) needed in the Wonderware SCADA for the cooling water system shall also be discussed. (author)
[en] For heating of plasma in steady state superconducting tokamak (SST -1) tokamak to ion temperature of ∼ 1 keV, a neutral beam injector is provided. This injector has a capability of injecting hydrogen beam with power of 0.5 MW at 30 keV. For upgrade of SST -1, power of 1.7 MW at 55 KeV is required. Further, beam power is to be provided for a pulse length of 1000 S. We have designed a neutral beam injector satisfying requirements for both SST -1 and its upgrade. Since intense power is to be transported to SST -1 situated at a distance of several meters from the ion source, optical quality of the beam becomes a primary concern. This in turn, is determined by the uniformity of the ion source plasma and extractor geometry. To obtain the desired optical quality of the beam stringent tolerances are to be met during fabrication of ion extractor system. Our neutral beam injector is based on positive ion source. The extraction system consists of 3 grids, each having extraction area of 230 mm x 480 mm and 774 shaped apertures of 8 mm diameter. To obtain horizontal focal length of 5.4 m and vertical of 7 m, each grid consists of two halves with 387 apertures. Two halves are inclined at an angle of 1.07 deg ± 0.01deg. For long pulse operation, active water cooling is provided by in-laid down of dense network of 22 wavy semicircular (R 1.1 ± 0.05 mm) cooling channels in the space available between the apertures. The required flatness of the copper plate is 100 μm and positioning of aperture is ± 60 μm. The results obtained after fabrication are compared with the set specifications. It is pointed out that fabrication within set tolerance limit could be achieved only through process of fabrication and high resolution measurements. (author)
[en] The effects of finite space charge on the equilibrium characteristics of charges confined in a Paul trap are investigated. It is found that space charge introduces two effects that have opposing influences on the confining pseudopotential well. The effect of electrostatic repulsion between like charges is to make the potential well shallower, but the plasma collective response can lead to a deepening of the well. Illustrative numerical solutions of thermal equilibria as well as an approximate analytical equilibrium are discussed. copyright 1995 American Institute of Physics
[en] This paper describes performance of an extractor system consists of three multi-aperture grids. The extractor system is capable of extracting 5 MW of positive ion beam power at 55 kV with beam divergence ∼0.97 deg. An extraction of 31 MJ of beam energy at 41 kV in 14 sec beam pulse has demonstrated that required 0.5 MW of beam power could be continuously injected into the SST - 1 Tokamak plasma for ion heating to 0.5 keV. (author)
[en] This paper describes beam optics of 3 grid acce-decel extraction system. It extracts high intensity, space charge limited, multi-charged positive ion beam from a volume type plasma source of neutral beam injector for SST-1 machine. (author)
[en] The influence of an intense beam in a high-pressure gas filled RF cavity has been measured by using a 400 MeV proton beam in the Mucool Test Area at Fermilab. The ionization process generates dense plasma in the cavity and the resultant power loss to the plasma is determined by measuring the cavity voltage on a sampling oscilloscope. The energy loss has been observed with various peak RF field gradients (E), gas pressures (p), and beam intensities in nitrogen and hydrogen gases. Observed RF energy dissipation in single electron (dw) in N2 and H2 gases was 2 10-17 and 3 10-17 Joules/RF cycle at E/p = 8 V/cm/Torr, respectively. More detailed dw measurement have been done in H2 gas at three different gas pressures. There is a clear discrepancy between the observed dw and analytical one. The discrepancy may be due to the gas density effect that has already been observed in various experiments.
[en] Recent High Pressure RF (HPRF) cavity experiment at MuCool Test Area (MTA) has used 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces the electrons. These electrons consume RF power inside the cavity. Number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is ∼ 1200. The measurement of beam position and profile are necessary. MTA is flammable gas (Hydrogen) hazard zone so we have developed a passive beam diagnostic instrument using Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. Neutral density filter was used to avoid saturation of CCD camera. Image data is filtered and fitted with Gaussian function to compute the beam size. The beam profile obtained from scintillation screen shall be compared with multi-wire beam profile.