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Since the 2018 IAEA FEC Conference, FTU operations have been devoted to several experiments covering a large range of topics, from the investigation of the behaviour of a liquid tin limiter to the runaway electrons mitigation and control and to the stabilization of tearing modes by electron cyclotron heating and by pellet injection. Other experiments have involved the spectroscopy of heavy metal ions, the electron density peaking in helium doped plasmas, the electron cyclotron assisted start-up and the electron temperature measurements in high temperature plasmas. The effectiveness of the laser induced breakdown spectroscopy system has been demonstrated and the new capabilities of the runaway electron imaging spectrometry system for in-flight runaways studies have been explored. Finally, a high resolution saddle coil array for MHD analysis and UV and SXR diamond detectors have been successfully tested on different plasma scenarios.

We present the latest version of OpenCAPWAP, our open-source implementation of the Internet Engineering Task Force control and provisioning of wireless access point CAPWAP protocol. The CAPWAP protocol is designed to support centralized management of large-scale and heterogeneous wireless networks, with a special focus on IEEE 802.11-based networks. The implementation presented in this paper improves substantially on the previous version, adding full support for the Split MAC architecture and decoupling completely the implementation from a specific driver solution. Although the main goal of the paper is to describe the technical solutions we adopted in the new implementation rather than present a complete performance analysis, we report, besides a wide set of experimental tests that validates the new implementation of OpenCAPWAP in terms of its functionalities and stability, also performance figures that show how OpenCAPWAP does not introduce any significant overhead with respect to commercial proprietary solutions. Copyright © 2016 John Wiley & Sons, Ltd.

FTU is operating since 1989, thus its hardware and software infrastructure must be continuously updated to preserve its efficiency and reliability. This issue can be addressed by means of two distinct approaches: (i) the migration to an emulated environment enabling the use of modern hardware on virtualized standard servers to keep the operating systems full functionality and the application environment; (ii) the porting of the complete system architecture to new hardware, new operating systems, and new programming languages. This paper reports on the upgrades implemented on FTU in the last two years using both these approaches including the new system to acquire and store the image frames of FTU plasma discharges through a Photron FASTCAM SA4 camera. Regarding data handling, a small Linux high performance computing system (1TFlops) with a high performance data storage system (100 TB) in InfiniBand DDR infrastructure has been installed as data analysis, modelling and archive cluster for the next three years of FTU experimental activities. © 2014 EURATOM-ENEA.

FTU three-level slow control system has undergone several enhancements during its lifetime [1], involving essentially the supervisory and medium level, while the lower level is still mainly based on old Westinghouse Numalogic PLCs. The legacy PLC controlling the toroidal magnet flywheel generator, named MFG1, is now being replaced with a more modern Siemens Simatic S7 PLC, because of its versatility an the ability to be integrated via standard networking protocol. The upgrade to this family of Siemens PLCs, which in the meantime has been selected as standard by ITER CODAC, has made MFG1 slow control an ideal candidate to deploy ITER CODAC software technologies and architecture to a running plant in an operating tokamak environment. A project has thus been started to port MFG1 control to ITER CODAC I&C architecture using the software package CODAC Core System [2] to interface the PLC with the ITER standard systems for instrumentation and control, Plant System Host (PSH) and Mini- CODAC, developing dedicated HMI and realizing the communication layer between MFG1 plant system and FTU supervisor. This paper will give a full account of the project and will report the results that have been obtained up to now, focusing also on the definite advantages provided by a distributed control architecture compared to the supervisor-dependent one still running at FTU, in view of future fusion devices. [1] Iannone F. et al, “CompactPCI/Linux platform in FTU slow control system”, Plasma Science and Technology Volume 6, Issue 6, December 2004, Pages 2535-2540 [2]http://www.iter.org/doc/www/edit/Lists/WebsiteText/Attachments/95/CODAC_Core_System _Overview_34SDZ5_v2_5.pdf

As in any other long-lasting experiment, new and standard activities on Frascati Tokamak Upgrade may require technological updates, especially on the control and data acquisition domain. The present paper will deal with a set of experiences arising from the necessity to replace ageing systems that turned out to be an interesting test-bed for new technologies. The first case study deals with FTU slow control, which is based on a standard three-layer model. The lower layer has been updated in the G1 power supply of the toroidal field, replacing the old Westinghouse PLC with a Siemens-S7. To integrate the new PLC in FTU control system, the open source LibNodave package under Linux operating system has been used. The results are compared to those obtained using the Siemens-S7 commercial library. The second case study regards FTU magnetic measurements. The system proposed will lead to the replacement of the old CAMAC system with a PXI embedded controller, acquiring hundreds of signals. Finally it will be shown how, taking advantage of those technologies, an ITER relevant control and data acquisition architecture can be designed.

The Control And Provisioning of Wireless Access Points (CAPWAP) protocol is under definition within the IETF to enable an Access Controller (AC) to manage a collection of Wireless Termination Points (WTPs). CAPWAP aims at simplifying the deployment and control of large scale, possibly heterogeneous, wireless networks. We present the first open source implementation of the CAPWAP protocol along with early experimental results aiming at the assessment of its reliability and performances. The paper ends describing applications of the CAPWAP protocol to management and QoS scenarios and discussing benefits and technical issues concerning its use.

The introduction of the IP multimedia subsystem on 3G cellular networks and the integration with other widely deployed wireless networks based on the IEEE 802.11 protocol family require support for both mobility and quality of service. When mobile systems move across heterogeneous networks, ongoing real-time sessions are affected not only by handoff delay but also by different packet delay and bit rate. In this paper, we propose a cross-layer mechanism that takes into account mobility at different layers of the network stack in order to yield better quality for VoIP, videoconferencing, and other real-time applications. We describe our cross-layer architecture, adaptation techniques, a prototype implementation, and experimental results.

Recently the slow control of the MFG1 motor flywheel generator powering FTU toroidal magnet has been redesigned within the framework of the ITER CODAC I&C architecture [1] using the software package CODAC Core System (CCS). In this paper the progress made towards the final commissioning will be detailed, focusing on the system integration in the FTU control system supervisor through a software bridge and a multithreaded channel access interface to the Plant System Host, emphasizing the problems found so far and their solutions. The development and implementation of the alarm handler, the logging system and the data archiving system will also be illustrated, as well as the relevant monitoring and visualization interfaces developed on the Mini-CODAC node with the standard EPICS tools BEAST, BOY and BEAUTY. Furthermore, the tests run on FTU that finally led to a successful commissioning will be thoroughly discussed. Due to the satisfactory outcome of the project, and taking advantage of the release of the new CCS v 3.0 introducing the management of fast controllers, an account on a possible application of the CODAC ITER fast control architecture at FTU will also be given, taking the FTU real time feedback system as the first test case, to be further extended to newly implemented fast controllers. © 2013 Euratom-ENEA Association sulla Fusione.

New FTU ohmic discharges with a liquid lithium limiter at I P = 0.7–0.75 MA, B T = 7 T and n e0 ⩾ 5 × 1020 m−3 confirm the spontaneous transition to an enhanced confinement regime, 1.3–1.4 times ITER-97-L, when the density peaking factor is above a threshold value of 1.7–1.8. The improved confinement derives from a reduction of electron thermal conductivity (χe) as density increases, while ion thermal conductivity (χi) remains close to neoclassical values. Linear microstability reveals the importance of lithium in triggering a turbulent inward flux for electrons and deuterium by changing the growth rates and phase of the ion-driven turbulence, while lithium flux is always directed outwards. A particle diffusion coefficient, D ∼ 0.07 m2 s−1, and an inward pinch velocity, V ∼ 0.27 m s−1, in qualitative agreement with Bohm–gyro-Bohm predictions are inferred in pellet fuelled lithized discharges. Radio frequency heated plasmas benefit from cleaner plasmas with edge optimized conditions. Lower hybrid waves penetration and current drive effects are clearly demonstrated at and above ITER densities thanks to a good control of edge parameters obtained by plasma operations with the external poloidal limiter, lithized walls and pellet fuelling. The electron cyclotron (EC) heating system is extensively exploited in FTU for contributing to ITER-relevant issues such as MHD control: sawtooth crash is actively controlled and density limit disruptions are avoided by central and off-axis deposition of 0.3 MW of EC power at 140 GHz. Fourier analysis shows that the density drop and the temperature rise, stimulated by modulated EC power in low collisionality plasmas are synchronous, implying that the heating method is the common cause of both the electron heating and the density drop. Perpendicularly injected electron cyclotron resonance heating is demonstrated to be more efficient than the obliquely injected one, reducing the minimum electric field required at breakdown by a factor of 3. Theoretical activity further develops the model to interpret high-frequency fishbones on FTU and other experiments as well as to characterize beta-induced Alfvén eigenmodes induced by magnetic islands in ohmic discharges. The theoretical framework of the general fishbone-like dispersion relation is used for implementing an extended version of the HMGC hybrid MHD gyrokinetic code. The upgraded version of HMGC will be able to handle fully compressible non-linear gyrokinetic equations and 3D MHD.

Since the 2012 IAEA-FEC Conference, FTU operations have been largely devoted to runaway electrons generation and control, to the exploitation of the 140GHz electron cyclotron (EC) system and to liquid metal limiter elements. Experiments on runaway electrons have shown that the measured threshold electric field for their generation is larger than predicted by collisional theory and can be justified considering synchrotron radiation losses. A new runaway electrons control algorithm was developed and tested in presence of a runaway current plateau, allowing to minimize the interactions with plasma facing components and safely shut down the discharges. The experimental sessions with 140GHz EC system have been mainly devoted to experiments on real-time control of magnetohydrodynamic (MHD) instabilities using the new EC launcher with fast steering capability. Experiments with central EC injection have shown the onset of 3/2 and 2/1 tearing modes, while EC assisted breakdown experiments have been focused on ITER start-up issues, exploring the polarization conversion at reflection from inner wall and the capability to assure plasma start-up even in presence of a large stray magnetic field. A new actively cooled lithium limiter has been installed and tested. The lithium limiter was inserted in the scrape-off layer, without any damage to the limiter surface. First elongated FTU plasmas with EC additional heating were obtained with the new cooled limiter. Density peaking and controlled MHD activity driven by neon injection were investigated at different plasma parameters. A full real-time algorithm for disruption prediction, based on MHD activity signals from Mirnov coils, was developed exploiting a large database of disruptions. Reciprocating Langmuir probes were used to measure the heat flux e-folding length in the scrape-off layer, with the plasma kept to lay on thea internal limiter to resemble the ITER start-up phase. New diagnostics were successfully installed and tested, as a diamond probe to detect Cherenkov radiation produced by fast electrons and a gamma camera for runaway electrons studies. Laser induced breakdown spectroscopy measurements were performed under vacuum and with toroidal magnetic field, so demonstrating their capability to provide useful information on the surface elemental composition and fuel retention in present and future tokamaks, such as ITER. © 2015 EURATOM.

IEEE 802.11e provides basic mechanisms for traffic differentiation in WLANs previously unavailable with the IEEE 802.11 standard. The enhanced distributed channel access (EDCA) is probably the most promising subset of such mechanisms, and it is already implemented in a huge number of Network Cards. In this paper we present an algorithm for the provisioning of QoS in EDCA WLANs. The algorithm is based on monitoring and reactive configuration of EDCA mechanisms in scenarios where voice over IP (VoIP) and best effort (BE) applications concurrently access the wireless channel. Results obtained in a real test-bed prove the effectiveness of the algorithm both in protecting VoIP communications and in providing minimal quality levels and fairness to BE applications.

The enhanced distributed channel access (EDCA) is a component of the new IEEE 802.11e standard [2], which introduces Quality of Service (QoS) support in Wireless LANs (WLANs). This paper proposes a model for the VoIP capacity of an EDCA WLAN. The proposed solution decouples the problem of estimating stations performance and that of evaluating channel congestion. Moreover, it models the dynamics of the sending queues. This translates in a model working under generic load conditions (i.e. VoIP traffic at different bit rates) that captures the impact of all the parameters introduced by EDCA. To validate the model, we derived a simple Admission Control algorithm for VoIP and generic real-time symmetric applications. Experimental analysis and simulations have been used to validate the model and to establish its limitations.

The Control And Provisioning of Wireless Access Points (CAPWAP) protocol is under development within the IETF to enable an Access Controller (AC) to manage a collection of Wireless Termination Points (WTPs). CAPWAP aims at simplifying the deployment and control of large scale, possibly heterogeneous, wireless networks. We present the first open source implementation of the CAPWAP protocol along with early experimental results aiming at the assessment of its reliability and performances. The paper ends describing applications of the CAPWAP protocol to QoS scenarios and discussing benefits and technical issues.

IEEE 802.11e provides a basic mechanism for traffic differentiation in WLANs. We present a method based on monitoring the traffic on the AP that it is efficient and allows the enforcement of QoS policies (admission control, traffic prioritization, bandwidth allocation etc.) in a IEEE 802.11e access network. The approach is simple to implement, flexible and does not rely on restrictive hypothesis about the traffic. We validate the proposal through experiments on VoIP traffic conducted in a real test bed.

Newborns with hypoplastic left heart syndrome and intact atrial septum present an emergent and unique challenge to a children's heart center. This case report describes new transcatheter techniques (use of radiofrequency energy to perforate the atrial septum followed by cutting balloon and static balloon septoplasty) and novel use of a transesophageal ICE probe.

Since the 2010 IAEA-FEC Conference, FTU has exploited improvements in cleaning procedures and in the density control system to complete a systematic exploration of access to high-density conditions in a wide range of plasma currents and magnetic fields. The line-averaged densities at the disruptive limit increased more than linearly with the toroidal field, while no dependence on plasma current was found; in fact, the maximum density of 4.3 × 10 20 m-3 was reached at B = 8 T even at the minimum current of 0.5 MA, corresponding to twice the Greenwald limit. The lack of plasma current dependence was due to the increase in density peaking with the safety factor. Experiments with the 140 GHz electron cyclotron resonance heating (ECRH) system were focused on the sawtooth (ST) period control and on the commissioning of a new launcher with real-time steering capability that will act as the front-end actuator of a real-time system for ST period control and tearing mode stabilization. Various ECRH and electron cyclotron current-drive modulation schemes were used; with the fastest one, the ST period synchronized with an 8 ms modulation period. The observed period variations were simulated using the JETTO code with a critical shear model for the crash trigger. The new launcher was of the plug-in type, allowing quick insertion and connection to the transmission line. Both beam characteristics and steering speed were in line with design expectation. Experimental results on the connection between improved coupling of lower hybrid waves in high-density plasmas and reduced wave spectral broadening were interpreted by fully kinetic, non-linear model calculations. A dual-frequency, time-of-flight diagnostic for the measurement of density profiles was developed and successfully tested. Fishbone-like instabilities driven by energetic electrons were simulated by the hybrid MHD-gyrokinetic XHMGC code. © 2013 IAEA, Vienna.