The scientific objective of the NBTF project is to develop a system to obtain a negative ion beam with high energy (1MeV) and power (16.5 megawatt), and with an almost continuous operation capacity, which will serve to heat the ITER plasma.
These are performance levels that have never been reached before, hence the need to create a laboratory where to design, build and test such a complex device, with:
spaces large enough to contain the large equipment under test;
a power supply network capable of supplying the high power required;
adequate resources to construct buildings and infrastructures;
a solid organization, with an international team of experienced engineers and physicists, able to design and operate the plant, assisted by a group of competent technicians and administrators.
Activities are progressing quickly: SPIDER, the prototype of the negative ion source, has been in operation since 2018; MITICA, the prototype of the 1MV injector is in an advanced stage of construction.
The NBTF Project is an international operation that places Italy directly IN THE HEART OF FUTURE FUSION REACTORS
To better understand the project, let’s first take a look at the PARAMETERS REQUIRED BY ITER, remembering that the main heating system of ITER will consist of two neutral beam injectors (NBI), each with an energy of 1 MeV and a beam of negative Deuterium ions of 40 A, to supply the plasma a power of about 16.5 MW for one hour.
SPIDER & MITICA prototypes to reach ITER parameters
The required parameters have never been obtained experimentally, so it was decided to produce two prototypes to test the system in the Neutral Beam Test Facility installed in Padua: SPIDER, the most powerful negative ion source in the world and MITICA the 1:1 scale prototype of the ITER injector, capable of operating at full power and voltage.
The injector is essentially composed of 5 parts: ion source – acceleration grids – neutralizer – Residual Ion Dump – calorimeter. Among these, the ion source represents one of the most critical systems. Let’s see in detail the different problems to be addressed.
The critical issues to overcome
To obtain the injection of 16.5 MW in ITER it is necessary to create a beam of high energy accelerated neutral particles. Having no charge, the neutrals can pass freely through the strong magnetic fields that surround the plasma. To obtain accelerated neutral particles it is more convenient to accelerate negative particles, starting from negative ions, and subsequently neutralize the beam.
The first stage occurs in the beam source, the second stage through the neutralizer.
The extraction and acceleration of negative ions occurs in the beam source
The beam source consists of a negative ion source and extraction and acceleration plates
THE BEAM SOURCE
How is the ITER beam source made?
It is composed of a radio frequency ion source and an extraction and acceleration system consisting of 7 grids.
The ion source is needed to:
produce a plasma starting from a neutral gas, by means of radiofrequency fields
extract a 40 A negative ion beam from the hydrogen or deuterium plasma.
the extraction takes place through 1280 perfectly calibrated holes, made in a surface of the source 2 meters high and 0.7 m wide.
the ions are extracted by means of electrostatic fields generated by applying about 10 kilovolts.
The experimentation on SPIDER, the prototype of the full-size negative ion source, will allow to fine-tune the physical and chemical processes involved for the source and extraction of negative ions.
The acceleration of the beam
The ions extracted from the source are subsequently accelerated by means of a grid system. In ITER the acceleration voltage is 1MV and applied by means of grids in 5 steps of 200 kV each.
Leaving the accelerator, a beam of negative hydrogen (H-) or deuterium (D-) ions of 40 A and an energy of 1 MeV is thus obtained.
The neutral particle beam source will measure 3 meters wide x 3 meters long x 4.5 meters high, with a total weight of 15 tons and will be located inside in each of the two neutral particle injectors that will be installed in ITER, which will contribute to the heating of the plasma, each with 16.5 MW of power.
The experimentation on the beam source in MITICA, the prototype the full-scale neutral injector, will allow to fine-tune the aspects related to the extraction and acceleration of negative ions (source of the beam), and to the subsequent stage in the neutralizer and focusing of the high-energy beam. MITICA therefore represents a complete system for generating a beam of high-energy neutral particles.
MITICA beam source
Visualization of the MITICA neutral particle injector
V. Toigo, S. Dal Bello, M. Bigi, M. Boldrin, G. Chitarin, L. Grando, A. Luchetta, D. Marcuzzi, R. Pasqualotto, N. Pomaro, G. Serianni, P. Zaccaria, L. Zanotto, P. Agostinetti, M. Agostini, V. Antoni, D. Aprile, M. Barbisan, M. Battistella, M. Brombin, R. Cavazzana, M. Dalla Palma, M. Dan, S. Denizeau, A. De Lorenzi, R. Delogu, M. De Muri, M. Fadone, F. Fellin, A. Ferro, A. Fiorentin, E. Gaio, G. Gambetta, F. Gasparini, F. Gnesotto, P. Jain, A. Maistrello, G. Manduchi, S. Manfrin, G. Marchiori, N. Marconato, M. Moresco, E. Ocello, T. Patton, M. Pavei, S. Peruzzo, N. Pilan, A. Pimazzoni, R. Piovan, C. Poggi, M. Recchia, A. Rizzolo, G. Rostagni, E. Sartori, M. Siragusa, P. Sonato, A. Sottocornola, E. Spada, S. Spagnolo, M. Spolaore, C. Taliercio, P. Tinti, M. Ugoletti, M. Valente, A. Zamengo, B. Zaniol, M. Zaupa, D. Boilson, C. Rotti, P. Veltri, J. Chareyre, H. Decamps, M. Dremel, J. Graceffa, F. Geli, B. Schunke, L. Svensson, M. Urbani, T. Bonicelli, G. Agarici, A. Garbuglia, A. Masiello, F. Paolucci, M. Simon, L. Bailly-Maitre, E. Bragulat, G. Gomez, D. Gutierrez, C. Labate, G. Mico, J.F. Moreno, V. Pilard, G. Kouzmenko, A. Rousseau, M. Kashiwagi, H. Tobari, K. Watanabe, T. Maejima, A. Kojima, N. Umeda, S. Sasaki, A. Chakraborty, U. Baruah, H. Patel, N.P. Singh, A. Patel, H. Dhola, B. Raval, V. Gupta, U. Fantz, B. Heinemann, W. Kraus, M. Cavenago, S. Hanke, S. Ochoa, P. Blatchford, B. Chuilon, Y. Xue, G. Croci, G. Gorini, A. Muraro, M. Rebai, M. Tardocchi, M. D’Arienzo, S. Sandri, A. Tonti, F. Panin (2019) Progress in the ITER neutral beam test facility. Nuclear Fusion, Vol 59, N. 8 https://doi.org/10.1088/1741-4326/ab2271
V. Toigo, D. Boilson, T. Bonicelli, R. Piovan, M. Hanada, A. Chakraborty, G. Agarici, V. Antoni, U. Baruah, M. Bigi, G. Chitarin, S. Dal Bello, H. Decamps, J. Graceffa, M. Kashiwagi, R. Hemsworth, A. Luchetta, D. Marcuzzi, A. Masiello, F. Paolucci, R. Pasqualotto, H. Patel, N. Pomaro, C. Rotti, G. Serianni, M. Simon, M. Singh, N.P. Singh, L. Svensson, H. Tobari, K. Watanabe, P. Zaccaria, P. Agostinetti, M. Agostini, R. Andreani, D. Aprile, M. Bandyopadhyay, M. Barbisan, M. Battistella, P. Bettini, P. Blatchford, M. Boldrin, F. Bonomo, E. Bragulat, M. Brombin, M. Cavenago, B. Chuilo, A. Coniglio, G. Croci, M. Dalla Palma, M. D’Arienzo, R. Dave, H. P. L De Esch, A. De Lorenzi, M. De Muri, R. Delogu, H. Dhola, U. Fantz, F. Fellin, L. Fellin, A. Ferro, A. Fiorentin, N. Fonnesu, P. Franzen, M. Fröschle, E. Gaio, G. Gambetta, G. Gomez, F. Gnesotto, G. Gorini, L. Grando, V. Gupta, D. Gutierrez, S. Hanke, C. Hardie, B. Heinemann, A. Kojima, W. Kraus, T. Maeshima, A. Maistrello, G. Manduchi, N. Marconato, G. Mico, J. F. Moreno, M. Moresco, A. Muraro, V. Muvvala, R. Nocentini, E. Ocello, S. Ochoa, D. Parmar, A. Patel, M. Pavei, S. Peruzzo, N. Pilan, V. Pilard, M. Recchia, R. Riedl, A. Rizzolo, G. Roopesh, G. Rostagni, S. Sandri, E. Sartori, P. Sonato, A. Sottocornola, S. Spagnolo, M. Spolaore, C. Taliercio, M. Tardocchi, A. Thakkar, N. Umeda, M. Valente, P. Veltri, A. Yadav, H. Yamanaka, A. Zamengo, B. Zaniol, L. Zanotto, M. Zaupa (2015) Progress in the realization of the PRIMA neutral beam test facility. Nuclear Fusion, Vol 55 N.8 https://doi.org/10.1088/0029-5515/55/8/083025
V Toigo, R Piovan, S Dal Bello, E Gaio, A Luchetta, R Pasqualotto, P Zaccaria, M Bigi, G Chitarin, D Marcuzzi, N Pomaro, G Serianni, P Agostinetti, M Agostini, V Antoni, D Aprile, C Baltador, M Barbisan, M Battistella, M Boldrin, M Brombin, M Dalla Palma, A De Lorenzi, R Delogu, M De Muri, F Fellin, A Ferro, A Fiorentin, G Gambetta, F Gnesotto, L Grando, P Jain, A Maistrello, G Manduchi, N Marconato, M Moresco, E Ocello, M Pavei, S Peruzzo, N Pilan, A Pimazzoni, M Recchia, A Rizzolo, G Rostagni, E Sartori, M Siragusa, P Sonato, A Sottocornola, E Spada, S Spagnolo, M Spolaore, C Taliercio, M Valente, P Veltri, A Zamengo, B Zaniol, L Zanotto, M Zaupa, D Boilson, J Graceffa, L Svensson, B Schunke, H Decamps, M Urbani, M Kushwah, J Chareyre, M Singh, T Bonicelli, G Agarici, A Garbuglia, A Masiello, F Paolucci, M Simon, L Bailly-Maitre, E Bragulat, G Gomez, D Gutierrez, G Mico, J-F Moreno, V Pilard, M Kashiwagi, M Hanada, H Tobari, K Watanabe, T Maejima, A Kojima, N Umeda, H Yamanaka, A Chakraborty, U Baruah, C Rotti, H Patel, M V Nagaraju, N P Singh, A Patel, H Dhola, B Raval, U Fantz, B Heinemann, W Kraus, S Hanke, V Hauer, S Ochoa, P Blatchford, B Chuilon, Y Xue, H P L De Esch, R Hemsworth, G Croci, G Gorini, M Rebai, A Muraro, M Tardocchi, M Cavenago, M D’Arienzo, S Sandri, A Tonti (2017)The PRIMA Test Facility: SPIDER and MITICA test-beds for ITER neutral beam injectors. New Journal of Physics, Vol. 19 https://doi.org/10.1088/1367-2630/aa78e8
