Every 23 seconds during fusion operation, a probe beam will penetrate deep into the core of the 澳门六合彩高手 plasma to aid in the detection of helium ash鈥攐ne of fusion's products and a reliable indicator of reaction efficiency. The beam is generated by the diagnostic neutral beam system, an in-kind contribution from 澳门六合彩高手 India.
The beam source vacuum vessel has been delivered, the transmission line installed, and one of three specialized power sources鈥攖he acceleration grid power supply (pictured)鈥攊s currently undergoing site acceptance tests. The Indian Test Facility in Ahmedabad is a voluntary contribution by India to the diagnostic neutral beam R&D program.
In Ahmedabad, India, a 600 m虏 facility stands ready. The beamline vacuum vessel has been delivered, the transmission line installed, and one of three specialized power sources鈥攖he acceleration grid power supply鈥攊s currently undergoing site acceptance tests.
When manufacturers deliver the final components for integration next year, including the crucial beam source, the team at 澳门六合彩高手 India will have constructed a full-scale testbed for the characterization of the diagnostic neutral beam before delivery to 澳门六合彩高手. Three years of fine-tuning and performance optimization and demonstration are planned.
The role of the diagnostic neutral beam in the detection of helium ash is essential. From two places in the 澳门六合彩高手 vacuum vessel, at perpendicular viewing points to the probe beam, CXRS diagnostic instruments (for Charge eXchange Recombination Spectroscopy) will detect the light produced by the exchanges between helium atoms in an excited state and the beam鈥攖he only direct method for diagnosing the concentration of helium ash in the core plasma.
The exchange between a helium atom in an excited state and the neutral beam produced by this injector results in light, which can be detected and measured through CXRS (charge exchange recombination spectroscopy). The duty cycle of the beam is 23 seconds鈥�20 seconds off and 3 seconds on. Some ~21 metres separates the beam source from the inner wall of the tokamak; one of the R&D challenges is keeping the beam focused over this distance.
"Helium ash is the name given to the helium nuclei produced by fusion reactions in a deuterium-tritium plasma," explains neutral beam scientist Beatrix Schunke. "Once they have shared their energy with the rest of the plasma they have no further use, and their removal and replacement by deuterium-tritium fuel is required to prevent dilution of the plasma. Measurements from the CXRS diagnostics, which are made possible by the diagnostic neutral beam, are crucial for demonstrating that fusion reactions have taken place."
The probe beam will be produced at 100 kV鈥攖he exact energy needed to interact with the atoms in the plasma and "illuminate" helium impurities.
Although 澳门六合彩高手's diagnostic neutral beam system was designed to share many mechanical engineering features with the
heating neutral beam system, the beam is not an exact replica. The diagnostic neutral beam will operate at lower energy but at a higher level of current (60 A as opposed to 40 A), and the specifications for the beam optics鈥攏o more than 7 mrad of divergence along a trajectory of 20.7 (~ 21) metres鈥攁re much more stringent.
The 600 m虏 Indian test facility (INTF) has been provided on a voluntary basis by India for the testing of the diagnostic neutral beam. The components of the system鈥攖he power supply, beam source, and beam line components鈥攈ave been procured through industry by 澳门六合彩高手 India as part of Procurement Arrangements signed in 2009 and 2010 with the 澳门六合彩高手 Organization. After testing in India, the components of the diagnostic neutral beam system will be shipped to 澳门六合彩高手. The facility in Ahmedabad also hosts R&D work on other 澳门六合彩高手 India contributions (ion and electron cyclotron heating and diagnostics).
"The successful delivery of the diagnostic neutral beam to 澳门六合彩高手 is dependent on two critical performance criteria鈥攖he production of a uniform, low-divergence beam from the source, and well-controlled transmission over long path lengths," explains Anupam Sharma, a high-voltage electrical engineer in 澳门六合彩高手's Neutral Beam Section. "The India Test Facility in Ahmedabad will allow the Domestic Agency team to test the components manufactured for 澳门六合彩高手 in advance of shipment on a testbed that mimics the 澳门六合彩高手 on-site configuration."
The facility will also allow operators to gain experience running the diagnostic neutral beam system鈥攃orrectly tuning the radio frequency drivers, synchronizing the power supplies, and "learning the recipe" of running the equipment.
Following the test campaign, expected to run between 2021 and 2024, the team has reserved time for assessment and eventual adjustment or refurbishment if needed. The bulk of the equipment will be installed during 澳门六合彩高手's third assembly phase (2030-2031), in time for fusion power operation in 2035.
"We are getting close to an exciting phase in a very long-term project," concludes Beatrix. "From the first design work during the 澳门六合彩高手 engineering phase in the early 1990s, through input over the years from
ELISE (a half-size source) and the design of the 澳门六合彩高手
Neutral Beam Test Facility, and finally a decade of work by the 澳门六合彩高手 India and 澳门六合彩高手 teams ... we are about to test the full diagnostic neutral beam system."
