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TJ-II:Heavy Ion Beam Probe: Difference between revisions
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== HIBP 2 == | == HIBP 2 == | ||
A second, similar system | A second, similar system has been installed in [[TJ-II:Sectors|sector]] A4 (see photo). | ||
[[File:IMG 1627.JPG|350px|thumb|right|Installation of the second HIBP probe (March, 2011)]] | [[File:IMG 1627.JPG|350px|thumb|right|Installation of the second HIBP probe (March, 2011)]] | ||
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The Heavy Ion Beam Probe (HIBP) is a unique diagnostic for its ability to measure plasma electric potential well inside the plasma column, where no material probes can be inserted. The operating principle is as follows: heavy ions <math>I^q</math> with charge <math>q</math> (Cs<math>^+</math> in the case of TJ-II) are accelerated to high energies (several hundred keV) and injected as a continuous jet into the plasma column. The interaction with the plasma yields a fan of secondary ions <math>I^{q'}</math> that are more strongly deflected by the magnetic field. Those secondary ions produced in the so-called `sample volume' are collected in an energy analyser. Their energy contains information on the electric potential in the sample volume. Trajectory reconstruction codes allow us to measure the position and reltive potential of the sample volume. | The Heavy Ion Beam Probe (HIBP) is a unique diagnostic for its ability to measure plasma electric potential well inside the plasma column, where no material probes can be inserted. The operating principle is as follows: heavy ions <math>I^q</math> with charge <math>q</math> (Cs<math>^+</math> in the case of TJ-II) are accelerated to high energies (several hundred keV) and injected as a continuous jet into the plasma column. The interaction with the plasma yields a fan of secondary ions <math>I^{q'}</math> that are more strongly deflected by the magnetic field. Those secondary ions produced in the so-called `sample volume' are collected in an energy analyser. Their energy contains information on the electric potential in the sample volume. Trajectory reconstruction codes allow us to measure the position and reltive potential of the sample volume. | ||
===Formal expression of the electric potential | ===Formal expression of the electric potential ''φ'' === | ||
Refering to the figure, we will denote as <math>A</math>, <math>B</math> and <math>C</math> the injection, ionization and detection points respectively. The Hamiltonian of a charge in an electromagnetic field is | Refering to the figure, we will denote as <math>A</math>, <math>B</math> and <math>C</math> the injection, ionization and detection points respectively. The Hamiltonian of a charge in an electromagnetic field is | ||
[[Image:HIBP3.png|256px|thumb|right|alt=Schematic HIBP operation principle.|Schematic HIBP operation principle.]] | [[Image:HIBP3.png|256px|thumb|right|alt=Schematic HIBP operation principle.|Schematic HIBP operation principle.]] | ||
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</math> | </math> | ||
===Operational expression for the electric potential | ===Operational expression for the electric potential ''φ'' === | ||
The energy analyser of the HIBP diagnostic at TJ-II is of the Proca-Green type. The kinetic energy of the secondary ions entering the analyser is given by | The energy analyser of the HIBP diagnostic at TJ-II is of the Proca-Green type. The kinetic energy of the secondary ions entering the analyser is given by | ||