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The neutron detection system for characterization of emissivity in ITER Tokamak during DD and DT experiments poses serious challenges to the performance of the diagnostic control and data acquisition system (CDAcq). The ongoing design of the ITER radial neutron camera (RNC) diagnostic is composed by 26 lines of sight (LOS) for complete plasma inspection. The CDAcq system aims at meeting the ITER requirements of delivering the measurement of the real-time neutron emissivity profile with time resolution and control cycle time of 10 ms at peak event rate of 2 MEvents/s per LOS. This measurement demands the generation of the neutron spectra for each LOS with neutron/gamma discrimination and pile-up rejection. The neutron spectra can be totally processed in the host CPU or it can use the processed data coming from the system field-programmable gate array (FPGA). The number of neutron counts extracted from the spectra is then used to calculate the neutron emissivity profile using an inversion algorithm. Moreover, it is required that the event-based raw data acquired are made available to the ITER data network without local data storage for postprocessing. The data production for the 2 MEvents/s rate can go up to a maximum data throughput of 0.5 GB/s per channel, fostering the evaluation of real-time data compression techniques in RNC. To meet the demands of the project, a CDAcq prototype has been used to design and test a high-performance distributed software architecture taking advantage of multicore CPU technology capable of coping with the requirements. This submission depicts the design of the real-time architecture, the spectra algorithms (pulse height analysis, neutron/gamma discrimination, and pile-up correction), and the inversion algorithm to calculate the emissivity profile. Preliminary tests to evaluate the systems performance with the synthetic data are presented. [ABSTRACT FROM AUTHOR]

To achieve the aim of the international thermonuclear experimental reactor (ITER) radial neutron camera diagnostic, the data acquisition prototype must be compliant with a sustained 2-MHz peak event per each channel. The data are acquired and processed using an IPFN FPGA Mezzanine Card (FMC-AD2-1600) with two digitizer channels of 12-bit resolution and a sampling rate up to 1.6 GSamples/s mounted in an peripheral component interconnect express (PCIe) evaluation board from Xilinx (KC705) installed in the host PC. The acquired data in the event-based data path are streamed to the host through the PCIe $\times 8$ direct memory access with a maximum data throughput per channel $\approx 0.5$ GB/s of raw data (event base), $\approx 1$ GB/s per digitizer, and up to 1.6 GB/s in continuous mode. The prototype architecture comprises a host PC with two KC705 modules and four channels, producing up to 2 GB/s in event mode and up to 3.2 GB/s in continuous mode. To reduce the produced data throughput from host to ITER archiving system, the real-time data compression was evaluated using the LZ4 lossless compression algorithm, which provides compression speed up to 400 MB/s per core. This paper presents the architecture, implementation, and test of the parallel real-time data compression system running in multiple isolated cores. The average space saving and the performance results for long-term acquisitions up to 30 min, using different data block sizes and different number of CPUs, are also presented. [ABSTRACT FROM AUTHOR]

This paper describes the high-priority testing activities supporting the ITER radial neutron camera (RNC) design, performed by a consortium of European institutes within a framework contract placed by fusion for energy, the ITER European Domestic Agency. The main role of the RNC is to measure the uncollided 14- and 2.5-MeV neutrons from deuterium–tritium and deuterium–deuterium fusion reactions through an array of flux monitors/spectrometers located in collimated lines of sight viewing the plasma through the ITER equatorial port plug #1. The line-integrated neutron fluxes will be used to evaluate, through reconstruction techniques, the radial profile of the neutrons emitted per unit time and volume (neutron emissivity) and, therefore, the neutron yield and the alpha particles’ birth profile. The activity of high-priority testing is dedicated to the preparation and the design of experimental test environment, the conduction of appropriate tests and reporting of test results for the high-priority prototypes, clarifying or verifying the expected key function and system behavior, and enhancing learning on specific issues (potential showstoppers). [ABSTRACT FROM AUTHOR]

Modern Tokamaks have evolved from the initial axisymmetric circular plasma shape to an elongated axisymmetric plasma shape that improves the energy confinement, which is one of the key factors to improve fusion reactor performance. However, the elongated plasma cross section introduces a vertical instability that requires a real-time feedback control loop to stabilize the plasma vertical position and velocity. At the Tokamak à Configuration Variable (TCV) in-vessel poloidal field coils driven by fast switching power supplies are used to stabilize highly elongated plasmas. TCV plasma experiments have used a PID algorithm based controller to correct the plasma vertical position. In late 2013 experiments a new optimal real-time controller was tested improving the stability of the plasma. This contribution describes the new optimal real-time controller developed. The choice of the model that describes the plasma response to the actuators is discussed. The high order model that is initially implemented needs the application of a mathematical order reduction and the validation of the new reduced model. The lower order model is used to derive the time optimal control law. A new method for the construction of the switching curves of a bang-bang controller is presented that is based on the state-space trajectories that optimize the time to target of the system. The final control algorithm and its implementation are described and preliminary experimental results are discussed. [ABSTRACT FROM AUTHOR]

Early tokamaks with circular cross-section plasmas were vertically stable in nature and no problems were reported on the control of the vertical position. However, the concept of vertically elongated plasma cross-section, with benefits to the energy confinement time, led to vertical instabilities. To overcome this problem, complex closed feedback loop control systems with a vertical position measurement, signal processing, control algorithm, power supplies and active actuating coils are used. [ABSTRACT FROM PUBLISHER]

The availability of small inexpensive sensor elements enables the employment of large wired or wireless sensor networks for feeding control systems. Unfortunately, the need to transmit a large number of sensor measurements over a network negatively affects the timing parameters of the control loop. This paper presents a solution to this problem by representing sensor measurements with an approximate representation-an interpolation of sensor measurements as a function of space coordinates. A priority-based medium access control (MAC) protocol is used to select the sensor messages with high information content. Thus, the information from a large number of sensor measurements is conveyed within a few messages. This approach greatly reduces the time for obtaining a snapshot of the environment state and therefore supports the real-time requirements of feedback control loops. [ABSTRACT FROM PUBLISHER]

A new Advanced Plasma Control System for the TCV Tokamak has been implemented based on an in-house developed high performance DSPs-based VME system, specially designed for real-time plasma control and event detection on fusion experiments. This paper describes the software architecture of the digital system as well as the integration of the physicists control algorithms in the DSPs software. The integration conditions on the TCV control system and the first results of the real-time control operation are also presented. Finally, a critical analysis of the system performance and the experimental operation of TCV APCS is discussed. [ABSTRACT FROM AUTHOR]

Eight independent multi-rate signal interpolators, with real-time change of rate capability, were implemented on a field programmable gate array. The interpolator main building blocks are a cascaded integrator-comb (CIC) filter and the respective compensation filter. The latter performs a fixed rate change of 4 and was implemented as a 129 taps finite impulse response (FIR) filter. The FIR filter coefficients were attained from the MATLAB® simulation, based on the inverse sinc(x) function. The CIC was designed to have six stages (N), a differential delay (M) of 1, and a variable rate change factor (R) ranging from 10 up to 10000. Each interpolator over-samples the multiple data rate digital signals stored at the Joint European Torus (JET) pulse database to a fixed sampling rate of 40 MSPS. These signals are subsequently converted to the analog domain by 16 bit digital-to-analog converters to be used as stimulus for testing real-time control tools and systems at JET. [ABSTRACT FROM AUTHOR]

This paper presents a new reconfigurable hardware platform which uses both digital signal processors (DSP) and field programmable gate arrays (FPGA) to attain high resolution and real-time processing in nuclear spectrometry experiments. The module was designed in order to provide a high digital pulse processing (DPP) yield with the capacity of being reconfigurable according to the experimental conditions and the desired data output. This allows unprecedented real time processing capabilities implemented in the FPGA such as pulse pileup correction through adaptive filtering and effective signal-to-noise ratio (SNR) control and optimization. The module uses a Virtex-Il Pro FPGA (Xilinx) and a DSP from the TMS320C64xx famity (Texas Instruments) and is implemented on a PCI board to be used in a host workstation. Special emphasis is given to the scalability of the module along with the potential capacity of being used as a portable stand-alone instrument. This reconfigurable hardware platform allows us to simultaneously benefit from the advantages of the hardware based digital spectrometers, namely, their high throughput, and of the flexibility of the software based configurations. Besides, this same platform can be used as a general purpose high-speed data acquisition and processing unit. [ABSTRACT FROM AUTHOR]