The ITER Neutral Beam Test Facility, in an advanced stage of construction in Padova, includes the installation, tests, and optimization of the full prototype of the ITER Heating Neutral Beams injector (HNBs), named MITICA. The MITICA Neutral Beam Injector will host its main components in a SS304L vacuum vessel composed of two modules, connected between them on site: the Beam Source Vessel (cubic shape of 5 m side and 67 tons weight) containing the Beam Source and the Beam Line Vessel (section 4.5 m x 4.5 m, length 11 m and 76 tons weight) containing the Beam Line Components and the Cryopumps. The manufacturing is described, going through the FE analyses performed to assess the structural integrity, the materials selection, the welding qualifications, the implementation of the double barrier sealings and the control of the deformations. The Factory Acceptance Tests of the individual vessels are presented, including their Helium Leak Tests. The two vessels have been assembled on-site inside the MITICA bio-shield. The main outcomes of on-site final assembly and Site Acceptance Tests are described. Both the vessels have been detail designed, manufactured, installed and tested by De Pretto Industried, from Schio, (VI) Italy, supporting fusion technology’s applications from more than 50 years. The design and the technical support were provided by Consorzio RFXa, while the procurement was managed by Fusion For Energye.

The SPIDER Beam Source (BS), the first prototype of a full scale ion source for the ITER Heating Neutral Beam injector, was delivered to the Neutral Beam Test Facility (NBTF) site in Padova (Italy) after about five years procurement phase. A huge effort was devoted during the procurement for quality controls and testing at the supplier's workshops. Several activities were also carried out on NBTF site for verification/adjustment of interfaces, solution of still open issues, as well as final tests before and after installation inside the vacuum vessel. The NBTF Team undertook the BS site acceptance tests including: pressure and leak tests of the hydraulic circuits; electrical tests; measurement of magnetic field profiles; functionality tests of diagnostics installed on the BS; checks of grids alignment by means of laser tracker. Accurate positioning of the BS inside the vacuum vessel was performed and various service lines were connected in a tight space. Several improvements were undertaken in order to guarantee reliability and reduce the risks during the commissioning and experimental campaign in 2018. After installation, the integrated commissioning phase was initiated, powering the RF and high voltage circuits, followed by the first operation in vacuum.

After installation of Mo liners in the source NIO1 (Negative Ion Optimization phase 1), hydrogen plasmas in a continuous regime operation (much longer than one hour) are routinely maintained, with more than 1 kW rf power and 0.5 Pa pressure, allowing a systematic investigation of pure H- volume effect, which requests a much lower acceleration voltage V-s congruent to 12 kV than future Cs operations at V-s congruent to 60 kV. A new extraction grid EG was installed (replacing some eroded insulators) and preliminary beam images are compared to old EG ones, discussing effects of different deflection field strength and need of intermediate values. Large improvements in beam diagnostics and the effect of installation of a cryogenic pump are also reported.

A system of electrostatic sensors has been designed for the SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) experiment, prototype RF source of the ITER NBI (neutral beam injection). A prototype of the sensor system was manufactured and tested at the BATMAN (BAvarian Test MAchine for Negative ions) facility, where the plasma environment is similar to that of SPIDER. Different aspects concerning the mechanical manufacturing and the signal conditioning are presented, among them the RF compensation adopted to reduce the RF effects which could lead to overestimated values of the electron temperature. The first commissioning tests provided ion saturation current values in the range assumed for the design, so the deduced plasma density estimate is consistent with the expected values.

In this paper qualification tests of various plastic lenses for operation in ultra-high vacuum (UHV) are reported for the first time. The results of a systematic investigation, covering the temperature range 20–200°C and aimed at qualifying the resin ADC200, an allyl diglycol carbonate, as a window for UHV vacuum vessels, are described. Tightness and permeation tests were performed and optical transmission monitored in the interval 200–850nm, to assess the effects of both the UHV environment and thermal excursion. Compatibility with UHV operation was checked independently over the temperature range 40–350°C using mass spectrometry. The results show that the polymer does not emit any contaminating components incompatible with UHV systems. Mechanical integrity was shown to be guaranteed up to a temperature of 150°C and no sign of degradation in the optical properties measured was ever detected. The major drawback of this technology for UHV would appear to be the high rate of He permeation through the plastic material. It is possible that this could be remedied by the application of suitable coatings.

Engineering Polymers are very good candidates for applications requiring mechanical properties comparable with metals, chemical inertia, high insulation capability, high temperature operation and ultra high vacuum (UHV) compatibility. The results of a systematic test series, aimed at qualifying the engineering resins VESPEL/spl reg/ SP1, PEEK and CELAZOLE/spl reg/ PBI as UHV seals, are reported. The study of the materials behavior has been carried out over a wide temperature interval, ranging from 20 to 400/spl deg/C. In addition to the tightness and permeation tests, thermal desorption and gas chromatographic-mass spectrometer (GC/MS) analysis have also been performed. The results obtained indicate that CELAZOLE/spl reg/PBI provides the best performance, since it can be operated safely up to 375/spl deg/C, without giving any sign of leak or other drawbacks. PEEK, on the contrary, does not stand temperatures higher than 275/spl deg/C but, below this limit, it remains a very cost effective and reliable alternative. VESPEL/spl reg/ SP1, in its turn, can be operated safely up to 325/spl deg/C but above this temperature its properties start to degrade even if not in an abrupt manner as is the case for the other two resins. The possible applications of some of these polymers in the field of nuclear fusion research are also briefly described.

Penning sensors were originally conceived to extend the measurement range of cold-cathode gauges in the direction of low pressures by introducing an additional constant magnetic field. This paper examines the possibility of using a commercially available sensor to measure magnetic field by keeping pressure constant. For the preliminary tests reported, a commercial Penning gauge was exposed to magnetic fields in the range of a few tens of mT to 1.1T. Three different regimes were identified. In the first, up to 150mT, the measured current increases linearly with the applied magnetic field. Following a very irregular transition region of the order of 50mT, for fields between 200mT and 1.1T, the measured current decays relatively smoothly. The results suggest that the principle may be applicable for the measurement of steady-state fields in harsh environments, with high temperature and neutron fluence.

The use of engineering resins has increased dramatically in the last years and now the mechanical and chemical properties of the most recent products render these new materials excellent candidates for ultra high vacuum (UHV) applications. In particular, a relatively inexpensive polymer like PEEK® can become competitive when vacuum seals have to be manufactured. In this paper, a systematic series of tests is described, aimed at comparing the properties of PEEK® and traditional Helicoflex seals. Two different designs for the new PEEK® seals were tested. Their performances were compared not only in cases of metal but also of glass plain surfaces. A complete temperature scan was carried out for both applications (metal and glass surfaces) up to 200°C. At room temperature the vacuum properties of PEEK® seals are comparable to those of the more traditional Helicoflex gaskets. At higher temperatures the only significant drawback of the proposed PEEK® prototypes is a significant He permeation. On the other hand, gaschromatographic-mass spectrometer analysis confirms that the outgassing of this material is compatible with UHV requirements. In the temperature range investigated, one of the tested solutions gives very positive results; given the lower cost and much easier handling of this prototype with respect to Helicoflex technology, the proposed design can be considered with great attention as a possible future replacement.

The properties of an upgraded active vacuum brazing procedure, explicitly developed to manufacture ceramic-metal joints, are presented and some of the most significant applications described. The essential feature of the technique is the use of AgCuTi as brazing material, which permits the joining of alumina (Al2O3) very reliably with various metals, including stainless steel. The careful control of the brazing cycle and the quality of the alumina, in terms of purity and density, play an essential role in determining the final performances of the components. With the technology presented, several vacuum components have been developed and manufactured, among which the most interesting are electrical feedthroughs compatible with commercially available signal connectors and capable of operating at temperatures of 500°C or higher. In particular, a completely new model of a signal feedthrough, to be used with the Minisnap-Plug of Odu and presenting an alumina–stainless steel joint, has been developed and thoroughly tested in the laboratory. Its performances have been verified at more than 700°C, with temperature variations of up to 10°/min. The latest version of these feedthroughs has shown good vacuum tightness and reliability up to 650°C and therefore presents better characteristics than most of the feedthroughs commercially available. In addition to being tested on the bench, some feedthroughs have been used in the nuclear fusion experiment Reversed Field eXperiment (RFX), without showing any sign of degradation or ageing.