R. Nocentini

Progress of the ELISE test facility: results of caesium operation with low RF power

The Max-Planck-Institut f?r Plasmaphysik test facility ELISE is an important intermediate step towards the in-time realization of the ITER neutral beam injection system (NBI). ELISE is equipped with a large radio-frequency (RF) driven negative hydrogen ion source (1???0.9?m2) of half the size of the ITER NBI source. The paper reports on the main results of the very first operation of the source with caesium, but with low RF power, both for hydrogen and deuterium, with pulse lengths of up to 500?s. The results are rather encouraging for the achievement of the required ITER NBI parameters, especially in hydrogen, where large current densities with respect to the low RF power could be achieved at a ratio of co-extracted electrons to extracted ions of 0.5?0.6 at the relevant source pressure of 0.3?Pa. The required magnetic filter field was significantly lower than expected from the experience with the prototype RF source. Similar large extracted ion currents could be achieved also in deuterium, but with larger amounts of co-extracted electrons. Here, the required ratio of co-extracted electrons to extracted ions of one could be achieved only in short pulses.

Physical and Experimental Background of the Design of the ELISE Test Facility

In 2007 the IPP RF driven negative hydrogen ion source was chosen by the ITER board as the new reference source for the ITER neutral beam system. In order to support the design of the Neutral Beam Test Facility in Padua and its commissioning and operating phases, IPP is presently constructing a new test facility ELISE (Extraction from a Large Ion Source Experiment) for a large‐scale extraction from a half‐size ITER RF source. Plasma operation of up to one hour is foreseen; but due to the limits of the IPP HV system, pulsed extraction only is possible. The extraction system is designed for acceleration of negative ions of up to 60 kV. The start of the ELISE operation is planned for middle of 2010. The aim of the design of the ELISE source and extraction system was to be as close as possible to the ITER design; it has however some modifications allowing a better diagnostic access as well as more flexibility for exploring open questions. The design was also supported by diagnostics and modeling efforts of th...

Towards 20 A negative hydrogen ion beams for up to 1 h: Achievements of the ELISE test facility (invited)

The large-scale RF-driven ion source of the test facility extraction from a large ion source experiment is aimed to deliver an accelerated ion current of 20 A D(-) (23 A H(-)) with an extracted electron-to-ion ratio below one for up to 1 h. Since the first plasma pulses for 20 s in volume operation in early 2013, followed by caesiation of the ion source, substantial progress has been achieved in extending the pulse length and the RF power. The record pulses in hydrogen are stable 400 s pulses with an extracted ion current of 18.3 A at 180 kW total RF power and 9.3 A at 80 kW stable for 1 h. For deuterium pulse, length and RF power are limited by the amount of co-extracted electrons.

Final design of the beam source for the MITICA injector

The megavolt ITER injector and concept advancement experiment is the prototype and the test bed of the ITER heating and current drive neutral beam injectors, currently in the final design phase, in view of the installation in Padova Research on Injector Megavolt Accelerated facility in Padova, Italy. The beam source is the key component of the system, as its goal is the generation of the 1 MeV accelerated beam of deuterium or hydrogen negative ions. This paper presents the highlights of the latest developments for the finalization of the MITICA beam source design, together with a description of the most recent analyses and R&D activities carried out in support of the design.

Toward a Large RF Ion Source for the ITER Neutral Beam Injector: Overview of the ELISE Test Facility and First Results

The ion source test facility extraction from a large ion source experiment (ELISE) has recently been built at Max Planck Institute for Plasma Physics (IPP) Garching (Germany) and has been operational since December 2012. ELISE is an important intermediate step in the R&D roadmap that the European domestic agency Fusion for Energy has defined for the International Thermonuclear Experimental Reactor (ITER) neutral beam injectors. This new test facility for a large radio frequency ion source builds up on the experience gained during many years of successful operation of smaller testbeds at IPP. The purpose of ELISE is to extract a negative ion beam, at ITER relevant parameters, using an ion source with the full width (1 m) and half the height of the ITER source. ELISE is designed to generate plasma for up to 1 h and extract a H- or D- beam at up to 60 kV. Available power supplies allow beam pulses of 10 s every 150-180 s. Although ELISE is designed to be as close as possible to the ITER source, technical solutions have been implemented that allow considerable experimental flexibility. Focus was put on easier diagnostic access and ease of maintenance. The results gained during the construction and operation of ELISE are delivering very important information to support the design and operation of the neutral beam test facility PRIMA to be built in Padua (Italy). This paper gives an overview of the project, presents experiences made during commissioning, and shows some basic results obtained so far.

Upgrade of the BATMAN test facility for H− source development

The development of a radio frequency (RF) driven source for negative hydrogen ions for the neutral beam heating devices of fusion experiments has been successfully carried out at IPP since 1996 on the test facility BATMAN. The required ITER parameters have been achieved with the prototype source consisting of a cylindrical driver on the back side of a racetrack like expansion chamber. The extraction system, called “Large Area Grid” (LAG) was derived from a positive ion accelerator from ASDEX Upgrade (AUG) using its aperture size (o 8 mm) and pattern but replacing the first two electrodes and masking down the extraction area to 70 cm2. BATMAN is a well diagnosed and highly flexible test facility which will be kept operational in parallel to the half size ITER source test facility ELISE for further developments to improve the RF efficiency and the beam properties. It is therefore planned to upgrade BATMAN with a new ITER-like grid system (ILG) representing almost one ITER beamlet group, namely 5 × 14 apertu...

Performance of multi-aperture grid extraction systems for an ITER-relevant RF-driven negative hydrogen ion source

The ITER neutral beam system requires a negative hydrogen ion beam of 48 A with an energy of 0.87 MeV, and a negative deuterium beam of 40 A with an energy of 1 MeV. The beam is extracted from a large ion source of dimension 1.9 × 0.9 m2 by an acceleration system consisting of seven grids with 1280 apertures each. Currently, apertures with a diameter of 14 mm in the first grid are foreseen.In 2007, the IPP RF source was chosen as the ITER reference source due to its reduced maintenance compared with arc-driven sources and the successful development at the BATMAN test facility of being equipped with the small IPP prototype RF source ( of the area of the ITER NBI source). These results, however, were obtained with an extraction system with 8 mm diameter apertures.This paper reports on the comparison of the source performance at BATMAN of an ITER-relevant extraction system equipped with chamfered apertures with a 14 mm diameter and 8 mm diameter aperture extraction system. The most important result is that there is almost no difference in the achieved current density—being consistent with ion trajectory calculations—and the amount of co-extracted electrons. Furthermore, some aspects of the beam optics of both extraction systems are discussed.

Simulations for the generation and extraction of negative hydrogen ions in RF‐driven ion sources

The injection of energetic neutral hydrogen atoms plays an important part for plasma heating in fusion experiments. In order to fulfill the requirements of the ITER neutral beam injection (NBI), a RF‐driven ion source based on the generation of negative ions prior to neutralization has been successfully developed at IPP Garching. Negative hydrogen ions are generated on a cesiated converter surface (plasma grid) by neutral particles and positive ions and are then transported to the extraction apertures, where the ion beam formation process takes place. Numerical models are necessary to include the relevant physical aspects of these processes. The Monte Carlo transport code CSFLOW is used to describe the dynamical behavior of the cesium distribution on the source walls during vacuum operation. The negative ion transport process is simulated by means of the probabilistic ion transport code TRAJAN, focussing on the effects of aperture diameter variations in mono‐ and multiaperture extraction systems. A simula...

Status of the ELISE Test Facility

The test facility ELISE, equipped with a large radio frequency (RF) driven ion source (1×0.9 m2) of half the size of the ion source for the ITER neutral beam injection (NBI) system, is operational since beginning of 2013. The first experimental campaign was dedicated to a thorough qualification of the test facility and its diagnostic tools at low RF power (80 kW in total, i.e. 20 kW per driver) in volume operation, i.e. operation without cesium, where the negative hydrogen ion production is done in the plasma volume only. This paper reports on the main results of the second and third experimental campaigns, where Cs was inserted in the ion source for an enhancement of the negative ion production by the surface process. The second experimental campaign was done still with low RF power, both for hydrogen and deuterium, with pulse lengths of up to 500 s. The results of this campaign are rather encouraging, especially in hydrogen, where large current densities with respect to the low RF power could be achieve...

Advanced Ion Beam Calorimetry for the Test Facility ELISE

The negative ion source test facility ELISE (Extraction from a Large Ion Source Experiment) is in operation since beginning of 2013 at the Max-Planck-Institut fur Plasmaphysik (IPP) in Garching bei Munchen. The large radio frequency driven ion source of ELISE is about 1×1 m2 in size (1/2 the ITER source) and can produce a plasma for up to 1 h. Negative ions can be extracted and accelerated by an ITER-like extraction system made of 3 grids with an area of 0.1 m2, for 10 s every 3 minutes. A total accelerating voltage of up to 60 kV is available, i.e. a maximum ion beam power of about 1.2 MW can be produced. ELISE is equipped with several beam diagnostic tools for the evaluation of the beam characteristics. In order to evaluate the beam properties with a high level of detail, a sophisticated diagnostic calorimeter has been installed in the test facility at the end of 2013, starting operation in January 2014. The diagnostic calorimeter is split into 4 copper plates with separate water calorimetry for each of...