R.C. Pereira

A high performance reconfigurable hardware platform for digital pulse processing

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-II Pro FPGA (Xilinx) and a DSP from the TMS320C64xx family (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.

High performance detectors for upgraded gamma ray diagnostics for JET DT campaigns

In forthcoming deuterium-tritium (DT) experiments on JET a significant population of alpha-particles will be produced. For operating alpha-particle diagnostics at high DT neutron fluxes, specific improvements have to be made. Proposed new detectors for gamma-ray measurements will be based on CeBr3 and LaBr3:Ce scintillators. They are characterized by a good energy resolution, a relatively high detection efficiency for a few MeV gamma-rays and a fast response time. An overview of scintillator parameters is presented. A description of the properties of photodetectors is given to indicate optimal setups. Results of measurements, using gamma-ray sources with energies up to a few MeV, are discussed with relation to the DT campaign requirements.

ATCA fast data acquisition and processing system for JET gamma-ray cameras upgrade diagnostic

Nuclear reaction gamma-ray diagnosis is one of the important techniques used for studying confined fast-ions. The Joint European Torus (JET) gamma-ray camera diagnostic provides information on the spatial distribution of fast ions. The system is currently being upgraded and should allow gamma-ray image measurements in high power deuterium JET pulses, and eventually in deuterium-tritium discharges. In order to fully exploit the diagnostic capabilities it is mandatory to develop a reliable, maintainable, multi-channel spectroscopy data acquisition and real-time processing (DAQP) system, which shares much of the common development for other specific implementation like Gamma-ray spectroscopy. The DAQP system is based on the Advanced Telecommunications Computing Architecture (ATCA) and contains a 6 GFLOPS x86-based control unit and three transient recorder and processing (TRP) modules, to cope with the two arrays of collimators (10 horizontal + 9 vertical lines of sight), interconnected through PCI Express (PCIe) links. Each TRP module features 8 channels of 13 bit resolution sampling at 250 MHz, 4GByte of local memory and two field programmable gate arrays able to perform complex trigger managing modes and allowing real time analyses (pulse height analyzer and pile-up discrimination), minimizing data storage and transfer issues. The DAQP system aims at overcoming the problem of storing large amount of data during long discharges. A raw/processed mode is being developed where the acquired raw data follows two parallel paths: besides being directly stored in the on-board memory, it is processed and streamed in real-time through PCIe links. This procedure is expected to greatly reduce the amount of data and possible allow continuous operation of the diagnostic. During commissioning and when data validation is required, the 4 GB raw data will be executed on the x86 control unit through a well known algorithm and the result cross checked with the processed data.

The control and data acquisition system of a laser in-vessel viewing system

This paper presents the dedicated control and data acquisition system (CADAS) of a new laser in-vessel viewing system that has been developed for inspection purposes in fusion experiments. CADAS is based on a MC68060 microprocessor and on-site developed VME instrumentation. Its main aims are to simultaneously control the laser alignment system as well as the laser beam deflection for in-vessel scanning, acquire a high-resolution image and support real-time data flow rates up to 2 Mbyte/s from the acquisition modules to the hard disk and network. The hardware (modules for control and alignment acquisition, scanning acquisition and monitoring) as well as the three levels of software are described.

Performance of the prototype LaBr3 spectrometer developed for the JET gamma-ray camera upgrade

In this work, we describe the solution developed by the gamma ray camera upgrade enhancement project to improve the spectroscopic properties of the existing JET γ-ray camera. Aim of the project is to enable gamma-ray spectroscopy in JET deuterium-tritium plasmas. A dedicated pilot spectrometer based on a LaBr3 crystal coupled to a silicon photo-multiplier has been developed. A proper pole zero cancellation network able to shorten the output signal to a length of 120 ns has been implemented allowing for spectroscopy at MHz count rates. The system has been characterized in the laboratory and shows an energy resolution of 5.5% at Eγ = 0.662 MeV, which extrapolates favorably in the energy range of interest for gamma-ray emission from fast ions in fusion plasmas.

HDL based FPGA interface library for data acquisition and multipurpose real time algorithm processing

The inherent parallelism of the logic resources, the flexibility in its configuration and the performance at high processing frequencies makes the field programmable gate array (FPGA) the most suitable device to be used both for real time algorithm processing and data transfer in instrumentation modules. Moreover, the reconfigurability of these FPGA based modules enables exploiting different applications on the same module. When using a reconfigurable module for various applications, the availability of a common interface library for easier implementation of the algorithms on the FPGA leads to more efficient development. The FPGA configuration is usually specified in a hardware description language (HDL) or other higher level descriptive language. The critical paths, as the management of internal hardware clocks, that require deep knowledge of the module behavior shall be implemented in HDL to optimize the timing constraints. The common interface library should include these critical paths, freeing the application designer from hardware complexity and able to choose any of the available high-level abstraction languages for the algorithm implementation. With this purpose a modular Verilog code was developed for the Virtex 4 FPGA of the in-house Transient Recorder and Processor (TRP) hardware module, based on the Advanced Telecommunications Computing Architecture (ATCA), with eight channels sampling at up to 400 MSamples/s. The TRP was designed to perform real time Pulse Height Analysis (PHA), Pulse Shape Discrimination (PSD) and Pile-Up Rejection (PUR) algorithms at a high count rate (few MHz). A brief description of this modular code is presented and examples of its use as interface with end user algorithms, including a PHA with PUR, are described.

The upgraded JET gamma-ray cameras based on high resolution/high count rate compact spectrometers

The JET gamma-ray cameras have been recently upgraded within the gamma-ray camera upgrade project in support of development of JET high performance deuterium plasma scenarios and in preparation of deuterium-tritium experiments. New, dedicated detectors based on a LaBr3 crystal and silicon photo-multipliers have been developed and replaced pre-existing CsI detectors in all 19 channels. The new instrument gives opportunity of making two-dimensional gamma-ray measurements with a counting rate capability exceeding 1 MCounts/s (MCps) and energy resolution better than 5% at 1.1 MeV. The upgrade is of relevance for fast ion and runaway electron physics studies in high performance deuterium discharges and also in plasmas with tritium at neutron yields in the range up to about 5 × 1017 n/s.

FPGA Remote Update for Nuclear Environments

In recent years there has been a growing interest to use reconfigurable modules, based on field-programmable gate array (FPGA) devices, in nuclear environments. One of the requirements for these types of modules, when operating in complex future nuclear power experiments, is their remote update capability. The operational needs of pulsed fusion reactors will lead to a large production of very high energy neutrons (MeV range). The current procurement policies for nuclear installations do not allow exposure of electronics to radiation, except following very strict rules. However, considering the “as low as (is) reasonably achievable” (ALARA) principle with respect to human exposure to radiation, the access to cubicles might be restricted, requiring the remote update of FPGA codes. FPGAs are volatile devices, and their programming code is usually stored in dedicated flash memories for proper configuration during module power-on. This paper presents an alternative method for FPGA remote update, capable to store new FPGA codes in inboard Serial Peripheral Interface (SPI) flash memories. The new method, based on the Xilinx Quick Boot application note and adapted to PCIe protocol, was developed with the KC705 Evaluation Kit from Xilinx and successfully tested in the in-house Advanced Mezzanine Card (AMC) prototype, installed on the ATCA-PTSW-AMC4 carrier module from the ITER Fast Plant System Controller catalogue.

Fusion alpha-particle diagnostics for DT experiments on the joint European torus

JET equipped with ITER-like wall (a beryllium wall and a tungsten divertor) can provide auxiliary heating with power up to 35MW, producing a significant population of α-particles in DT operation. The direct measurements of alphas are very difficult and α-particle studies require a significant development of dedicated diagnostics. JET now has an excellent set of confined and lost fast particle diagnostics for measuring the α-particle source and its evolution in space and time, α-particle energy distribution, and α-particle losses. This paper describes how the above mentioned JET diagnostic systems could be used for α-particle measurements, and what options exist for keeping the essential α-particle diagnostics functioning well in the presence of intense DT neutron flux. Also, α-particle diagnostics for ITER are discussed.

A high-data-transfer-rate VME system for TCP-IP remote real-time control of the ITER in-vessel vision system

This paper describes the control and data acquisition system (CADAS) for the in-vessel vision system (IVVS) for ITER, which imposes special design requirements due to its reactor characteristics. CADAS provides remote real-time control of the motors (by TCP-IP), fast data acquisition (20 bytes/pixel at 100 kpixels/s), error management and sustainable network data transfer rates (by TCP-IP). It is composed of a supervisory workstation connected by a 100 Mbit/s Ethernet channel to a remote VME crate, housing a board based on a PowerPC604R CPU running LynxOS, and two on-site developed intelligent modules. The architecture of these VME modules as well as the operation software and the application protocol are described. The test results are presented as well as an image obtained during the test procedures performed at the ENEA-Frascati Laboratory.