ITER Heating Neutral Beam Injector Research Articles

Diagnostics of the ITER neutral beam test facility

The ITER heating neutral beam (HNB) injector, based on negative ions accelerated at 1 MV, will be tested and optimized in the SPIDER source and MITICA full injector prototypes, using a set of diagnostics not available on the ITER HNB. The RF source, where the H(-)∕D(-) production is enhanced by cesium evaporation, will be monitored with thermocouples, electrostatic probes, optical emission spectroscopy, cavity ring down, and laser absorption spectroscopy. The beam is analyzed by cooling water calorimetry, a short pulse instrumented calorimeter, beam emission spectroscopy, visible tomography, and neutron imaging. Design of the diagnostic systems is presented.

Data Acquisition in the ITER Ion Source Experiment

The Ion Source experiment, called SPIDER, is the first experiment to be realized in the ITER Neutral Beam Test Facility under construction at Consorzio RFX, Padova, Italy. Its data acquisition system will provide the collection of around one thousand signals at a sampling rate ranging from a few S/s to 10 MS/s and of diagnostics and inspection images produced at a frame frequency from 10 to 150 frame per second, for beam durations of up to one hour. As the final product of the Test Facility will be the ITER Heating Neutral Beam Injector, we decided to follow the ITER CODAC guidelines. Therefore, the EPICS system provided in the CODAC Core System has been assessed and adopted in plant control. In addition to EPICS, the MDSplus system will be adopted for the overall data management. MDSplus can handle a rich set of data types and offers support for both local and remote data access in a variety of languages, a feature not fully supported by EPICS. All experiment data in SPIDER will be maintained in a single MDSplus database containing both experiment configuration and acquired data. The seamless integration of EPICS and MDSplus in a single system requires the development of some new tools, namely: A Channel Archiver which provides storage into MDSplus pulse files of data produced by EPICS Input Output Controllers (IOC) and exported as Process Variables via Channel Access; A set of IOC records providing direct access from IOC into MDSPlus files; A Channel Access Server to export MDSplus data as EPICS Process Variables, making them directly accessible by IOCs. We expect that the integration of the two frameworks will result in a system that combines the best features from each one, i.e., the management of distributed Process Variables and the IOC concept for EPICS, the sophisticated data management and remote access for MDSplus.

EPICS – MDSplus integration in the ITER Neutral Beam Test Facility

SPIDER, the ITER-size ion-source test bed in the ITER Neutral Beam Test Facility, is a fusion device requiring a complex central system to provide control and data acquisition, referred to as CODAS. The CODAS software architecture will rely on EPICS and MDSplus, two open-source, collaborative software frameworks, targeted at control and data acquisition, respectively. EPICS has been selected as ITER CODAC middleware and, as the final deliverable of the Neutral Beam Test Facility is the procurement of the ITER Heating Neutral Beam Injector, we decided to adopt this ITER technology. MDSplus is a software package for data management, supporting advanced concepts, such as platform and underlying hardware independence, self description data, and data driven model. The combined use of EPICS and MDSplus is not new in fusion, but their level of integration will be new in SPIDER, achieved by a more refined data access layer. The paper presents the integration software to use effectively EPICS and MDSplus, including the definition of appropriate EPICS records to interact with MDSplus. The MDSplus and EPICS archive concepts are also compared on the basis of performance tests and data streaming is investigated by ad-hoc measurements.

Comparison between commercial and open-source SCADA packages—A case study

SPIDER (Source for the Production of Ions of Deuterium Extracted from Rf plasma) is a new experimental device under development at Consorzio RFX aimed at providing a full-scale ion source prototype for MITICA (Megavolt ITer Injector and Concept Advance), the experiment devoted at supplying a full-scale prototype of the ITER Heating Neutral Beam Injector (HNB). Both experimental devices will be hosted in a new facility known as PRIMA (Padova Research on Injectors Megavolt Accelerated). The correct operation of SPIDER and MITICA will be guaranteed by process automation and plant monitoring that will be implemented using suitable controllers (cycle time greater than 10 ms) in conjunction with appropriate SCADA (Supervisory Control And Data Acquisition) software. This paper presents the tests performed at Consorzio RFX to evaluate commercial and open-source SCADA packages and prepare a technical base for the selection of the SCADA system for SPIDER. Two commercial solutions and two open-source solutions (EPICS and TANGO) were investigated. The typical test-bed was represented by a SCADA system exchanging data with a PLC (Programmable Logic Controller). The case study consisted of: (a) the development of a minimal panel provided with fields for setting parameters and of a trend window; (b) the set-up of two kinds of communication, a direct connection between the SCADA and the PLC and an indirect one by means of an OPC (Object Linking and Embedding for Process Control) server. The communication performance was evaluated measuring the network traffic with a fixed number of data variables exchanged and different polling cycle times. The conclusions show that the final choice of a SCADA package for SPIDER will be between one commercial SCADA and EPICS. This choice will not depend uniquely on the results of the tests, but will be also dictated by the early schedule of the SPIDER operations.

Cryopump design for the ITER heating neutral beam injector

Forschungszentrum Karlsruhe (FZK) is developing cryopumps for ITER heating neutral beam injectors (NBIs). The system is characterized by high gas flows coming from different sources against which the cryopumps must maintain a pressure between 10−2 and 10−3 Pa in the beam line (BL) vessel. The design of 2001 had proposed a cylindrical vessel with a cylindrical cryopump inside with a maximized pumping area to cover the vacuum requirements. In this design the only access to all BL components was through the beam source vessel, making it necessary to dismantle the beam source for all maintenance issues on the BL. During the ongoing design investigations on the heating NBI, it was decided in 2006 to use a rectangular vessel for the BL with a top access to improve the maintenance. This necessitated a full redesign of the cryopumps. In the new geometry of the BL vessel the size of the cryopump is limited to a flat rectangular geometry of 8 m length, 2.75 m height and 0.5 m depth. To cover the vacuum requirements two cryopumps of this size must be included for each injector. Gas profile calculations using the detailed BL geometry have been used to detect the needed gas capture probability of the pumping surface to guarantee the beam pulse operation. In this paper we give an outline of the working scope done to come up with a cryopump design covering the needs of the ITER NBI. The design of the novel cryopump and the heat load calculations for the different operation scenarios will be discussed. It is shown that the cryopump for the ITER heating NBI covers all vacuum requirements and it is fully adapted to the ITER cryogenic supply.

Preliminary design of the control and data acquisition systems for the Neutral Beam Test Facility

The Neutral Beam Test Facility, which will be built in Padova, Italy, is aimed at developing the ITER heating neutral beam injector (HNB) and at testing and optimizing its operation up to nominal performance before installation on ITER. It requires the development of two independent experiments referred to as SPIDER (source for production of ions of deuterium extracted from Rf plasma) and MITICA (megavolt ITer injector & concept advancement). SPIDER will explore the full-size negative ion source for ITER, whereas MITICA will explore the full-size ITER neutral beam injector. Both experiments will be designed for long-pulse operation, up to 3600 s, as ITER itself. MITICA includes three functional components: the heating neutral beam injector plant system (HNB), which is the device under test; the auxiliary plant system (AUX), which includes all equipment to operate the HNB in the test facility (e.g. the local electric grid to feed the HNB power supplies), and MITICA supervisory system that is an electronics/informatics infrastructure to operate the facility. The paper introduces the requirements for the control and data acquisition systems of the experiments and proposes a preliminary design for both systems. SPIDER, which is preparatory to MITICA and will be developed on a shorter time scale, has no constraints coming from ITER CODAC, whereas MITICA includes the ITER neutral beam injector and therefore must be fully compatible with ITER CODAC.

Design issues of the High Voltage platform and feedthrough for the ITER NBI Ion Source

In the ITER heating Neutral Beam Injector (NBI), a High Voltage air-insulated platform (named High Voltage Deck, HVD) will be installed to host the Ion Source and Extractor Power supply system and associated diagnostics referred to −1 MV DC potential. All power and control cables are routed from the HVD via a feedthrough (HV bushing) to the gas insulated transmission line which feeds the Injector. The paper focuses on insulation and mechanical issues for both HVD and HV bushing which are very special components, far from the present industrial standards as far as voltage (−1 MV DC) and dimensions are concerned. For this purpose, a preliminary design of the HVD has been carried out as concerns the mechanical structure and external shield. Then, the structure has been verified with a seismic analysis applying the seismic load excitation specified for the ITER construction site (Cadarache) and carrying out verifications according to relevant international standards. As regards the HV bushing design, proposals for the complex inner conductor structure and for interfaces to the HVD and transmission line are outlined; alternative installation layouts (aside or underneath the HVD) are compared from both mechanical and electrical points of view.