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Updated electrical design of the Diagnostic Neutral Beam Injector in RFX-mod2

Marco Barbisan, Bruno Laterza, Luca Cinnirella, Lionello Marrelli, Federico Molon, Simone Peruzzo, Enrico Zampiva

TL;DR

The updated DNBI design for the RFX-mod2 addresses obsolescence in power and control systems by detailing a comprehensive overhaul of the High Voltage Deck and HV components, alongside new subsystems (MIPS, GVPS) and multipurpose control boards. The redesign relocates the HVD to a safer, mezzanine-based layout, replaces the triple-insulation transformer with a standard resin unit, and implements robust TVS protection and expanded monitoring to improve reliability and safety. A PLC-based control and data acquisition architecture using ET200SP enhances scalability and maintainability, enabling cross-device deployment and safer operation at high voltage. Together with planned vacuum and beam duct upgrades, the work aims for full DNBI commissioning by 2027 and better core-plasma diagnostics via CXRS and MSE for RFP plasmas, under EU funding.

Abstract

The Diagnostic Neutral Beam Injector of the RFX-mod2 experiment (Consorzio RFX, Padova) is expected to provide novel and significant information about the Reversed Field Pinch confinement of fusion plasmas. The injection of the hydrogen beam in the plasma will allow Charge Exchange Recombination Spectroscopy (CXRS) and Motional Stark Effect diagnostics (MSE) to measure several quantities: ion speed, ion temperature, impurity content, intensity and pitch of the magnetic field. The DNBI is of particular importance for allowing the determination of these quantities at the core of the plasma. The present DNBI, built by the Budker Institute of Plasma Physics, features an arc discharge H+ source, coupled to a 4-grid 50 keV acceleration system. The 50 ms, 5 A ion beam is neutralized by charge exchange by means of a gas target; residual ions are then deflected by a magnetic field before injection in the torus chamber. The beam can be modulated at maximum 250 Hz. The DNBI will undergo extraordinary maintenance and a structural upgrade to improve its reliability and safety. This contribution presents the latest upgrades of the electrical plants and of the control system of the DNBI.

Updated electrical design of the Diagnostic Neutral Beam Injector in RFX-mod2

TL;DR

The updated DNBI design for the RFX-mod2 addresses obsolescence in power and control systems by detailing a comprehensive overhaul of the High Voltage Deck and HV components, alongside new subsystems (MIPS, GVPS) and multipurpose control boards. The redesign relocates the HVD to a safer, mezzanine-based layout, replaces the triple-insulation transformer with a standard resin unit, and implements robust TVS protection and expanded monitoring to improve reliability and safety. A PLC-based control and data acquisition architecture using ET200SP enhances scalability and maintainability, enabling cross-device deployment and safer operation at high voltage. Together with planned vacuum and beam duct upgrades, the work aims for full DNBI commissioning by 2027 and better core-plasma diagnostics via CXRS and MSE for RFP plasmas, under EU funding.

Abstract

The Diagnostic Neutral Beam Injector of the RFX-mod2 experiment (Consorzio RFX, Padova) is expected to provide novel and significant information about the Reversed Field Pinch confinement of fusion plasmas. The injection of the hydrogen beam in the plasma will allow Charge Exchange Recombination Spectroscopy (CXRS) and Motional Stark Effect diagnostics (MSE) to measure several quantities: ion speed, ion temperature, impurity content, intensity and pitch of the magnetic field. The DNBI is of particular importance for allowing the determination of these quantities at the core of the plasma. The present DNBI, built by the Budker Institute of Plasma Physics, features an arc discharge H+ source, coupled to a 4-grid 50 keV acceleration system. The 50 ms, 5 A ion beam is neutralized by charge exchange by means of a gas target; residual ions are then deflected by a magnetic field before injection in the torus chamber. The beam can be modulated at maximum 250 Hz. The DNBI will undergo extraordinary maintenance and a structural upgrade to improve its reliability and safety. This contribution presents the latest upgrades of the electrical plants and of the control system of the DNBI.
Paper Structure (10 sections, 11 figures)

This paper contains 10 sections, 11 figures.

Table of Contents

  1. Introduction
  2. High Voltage Deck Improvements
  3. Overview
  4. High Voltage Components
  5. Upgrade of power supplies
  6. Magnetic Insulation Power Supply
  7. Gas Valve Power Supplies
  8. Custom developed control boards
  9. Improvements on Control and Data Acquisition
  10. Conclusions

Figures (11)

  • Figure 1: Implementation of the HVD design (final cabling and setup of HV circuit is still ongoing).
  • Figure 2: High voltage circuit in the HVD.
  • Figure 3: R0 and first section of the resistive divider (R1).
  • Figure 4: TVS protection for 50 kV (TVS1, bottom) and for the PG-EG gap (TVS2, top).
  • Figure 5: Basic electric scheme of the MIPS.
  • ...and 6 more figures