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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Performance tests of boron-coated straw detectors with thermal and cold neutron beams

Prototypes of in-house developed boron-coated straw (BCS) detectors have been tested in the thermal and cold neutron energy ranges. Their neutron detection performance has been benchmarked against the industry standard (detector tubes filled with 3 He gas). The tests show that the BCS detectors perform near their theoretical limit regarding the detection efficiency, which is adequate for scientific instruments in the cold neutron energy range. Finally, the BCS detectors perform on par with 3 He tubes in terms of signal to noise and timing resolution, and superior regarding longitudinal spatial resolution.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Diamond detector for high rate monitors of fast neutrons beams

A fast neutron detection system suitable for high rate measurements is presented. The detector is based on a commercial high purity single crystal diamond (SDD) coupled to a fast digital data acquisition system. The detector was tested at the ISIS pulsed spallation neutron source. The SDD event signal was digitized at 1 GHz to reconstruct the deposited energy (pulse amplitude) and neutron arrival time; the event time of flight (ToF) was obtained relative to the recorded proton beam signal t{sub 0}. Fast acquisition is needed since the peak count rate is very high ({approx}800 kHz) due to the pulsed structure of the neutron beam. Measurements at ISIS indicate that three characteristics regions exist in the biparametric spectrum: i) background gamma events of low pulse amplitudes; ii) low pulse amplitude neutron events in the energy range E{sub dep}= 1.5-7 MeV ascribed to neutron elastic scattering on {sup 12}C; iii) large pulse amplitude neutron events with E{sub n} < 7 MeV ascribed to {sup 12}C(n,{alpha}){sup 9}Be and 12C(n,n')3{alpha}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

LOCALIZING COMPACT BINARY INSPIRALS ON THE SKY USING GROUND-BASED GRAVITATIONAL WAVE INTERFEROMETERS

The inspirals and mergers of compact binaries are among the most promising events for ground-based gravitational-wave (GW) observatories. The detection of electromagnetic (EM) signals from these sources would provide complementary information to the GW signal. It is therefore important to determine the ability of GW detectors to localize compact binaries on the sky, so that they can be matched to their EM counterparts. We use Markov Chain Monte Carlo techniques to study sky localization using networks of ground-based interferometers. Using a coherent-network analysis, we find that the Laser Interferometer Gravitational Wave Observatory (LIGO)-Virgo network can localize 50% of their detected neutron star binaries to better than 50 deg{sup 2} with a 95% confidence interval. The addition of the Large Scale Cryogenic Gravitational Wave Telescope (LCGT) and LIGO-Australia improves this to 12 deg{sup 2}. Using a more conservative coincident detection threshold, we find that 50% of detected neutron star binaries are localized to 13 deg{sup 2} using the LIGO-Virgo network, and to 3 deg{sup 2} using the LIGO-Virgo-LCGT-LIGO-Australia network. Our findings suggest that the coordination of GW observatories and EM facilities offers great promise.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

A Ce-Doped LiI Scintillator Film-Based High Rate, High Spatial Resolution Neutron Anger Camera for Neutron Scattering Facilities

The 2-D position sensitive neutron detectors featuring a significantly improved count rate capacity and a sub-mm spatial resolution are in high demand by neutron scattering facilities, especially the next generation high-flux spallation neutron sources (SNSs). They are anticipated to play a crucial role in fully utilizing the unprecedentedly high neutron brightness offered by these sources. In this work, a high rate and high spatial resolution neutron Anger camera has been successfully developed based on a Ce-doped microcolumnar LiI scintillator film and the PETsys TOFPET2 ASIC readout electronics. The performance evaluation was conducted in a standard laboratory environment as well as the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) with regard to light yield, γ-ray sensitivity, neutron detection efficiency, count rate capability, spatial resolution, and position linearity. The LiI:Ce scintillator was found to have a higher light yield and a lower γ-ray sensitivity than GS20 (i.e., 11729 versus 6000 photons/n and 1.67 × 10 −5 versus on the order of 10 −4 ). The neutron detection efficiency was measured to be 63% at 4.2 Å. This camera demonstrated an exceptional count rate capability, up to at least 481 kHz without rate loss. The spatial resolution was as good as 0.47 mm. Here, the position linearity was also enhanced.

High rate↗
DOE OSTI2011

Performance of BF{sub 3} Filled Position Sensitive Neutron Detector

{sup 3}He filled position sensitive detectors (PSD)s developed in-house are successfully used for neutron scattering studies at Dhruva. However recent global scarcity of {sup 3}He has made it essential to find an alternative. It is very difficult to meet performance capabilities of {sup 3}He for neutron detection in any of the alternate materials. Among various alternatives, BF{sub 3} gas can be one. We have recently put an effort to evaluate performance of BF{sub 3} based PSD. For that a PSD filled with BF{sub 3} gas at 0.8 bar pressure is fabricated and characterized. Performances of the same with Pu-Be source and at Hi-Q Diffractometer, Dhruva are reported in this paper. Diffraction spectra from standard samples Fe and Si at wavelength 0.783 A were recorded. It is found that while position resolution of the BF{sub 3} filled PSD is comparable but the efficiency is 20 times less than that of a {sup 3}He(12 bar) filled PSD.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A new Recoil Proton Telescope for energy and fluence measurement of fast neutron fields

The spectrometer ATHENA (Accurate Telescope for High Energy Neutron metrology Applications), is being developed at the IRSN / LMDN (Institut de Radioprotection et de Surete nucleaire / Laboratoire de Metrologie et de dosimetrie des neutrons) and aims at characterizing energy and fluence of fast neutron fields. The detector is a Recoil Proton Telescope and measures neutron fields in the range of 5 to 20 MeV. This telescope is intended to become a primary standard for both energy and fluence measurements. The neutron detection is achieved by a polyethylene radiator for n-p conversion, three 50{sub m} thick silicon sensors that use CMOS technology for the proton tracking and a 3 mm thick silicon diode to measure the residual proton energy. This first prototype used CMOS sensors called MIMOSTAR, initially developed for heavy ion physics. The use of CMOS sensors and silicon diode increases the intrinsic efficiency of the detector by a factor of ten compared with conventional designs. The first prototype has already been done and was a successful study giving the results it offered in terms of energy and fluence measurements. For mono energetic beams going from 5 to 19 MeV, the telescope offered an energy resolution between 5 and 11% and fluence difference going from 5 to 7% compared to other home standards. A second and final prototype of the detector is being designed. It will hold upgraded CMOS sensors called FastPixN. These CMOS sensors are supposed to run 400 times faster than the older version and therefore give the telescope the ability to support neutron flux in the order of 107 to 108cm{sup 2}:s{sup 1}. The first prototypes results showed that a 50 m pixel size is enough for a precise scattering angle reconstruction. Simulations using MCNPX and GEANT4 are already in place for further improvements. A DeltaE diode will replace the third CMOS sensor and will be installed right before the silicon diode for a better recoil proton selection. The final prototype with its new geometry will increase the telescopes efficiency by a factor of 1.5. It will also cover some of the most important points in metrology; repeatability, reproducibility and sustainability. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Performance of Large Neutron Detectors Containing Lithium-Gadolinium-Borate Scintillator

This paper describes the development and testing of a neutron counter, spectrometer, and dosimeter that is compact, efficient, and accurate. A self-contained neutron detection instrument has wide applications in health physics, scientific research, and programs to detect, monitor, and control strategic nuclear materials (SNM). The 1.3 liter detector head for this instrument is a composite detector with an organic scintillator containing uniformly distributed {sup 6}Li{sub 6}{sup nat}Gd{sup 10}B{sub 3}O{sub 9}:Ce (LGB:Ce) microcrystals. The plastic scintillator acts to slow impinging neutrons and emits light proportional to the energy lost by the neutrons as they moderate in the detector body. Moderating neutrons that have slowed sufficiently capture in one of the Lithium-6, Boron-10, or Gadolinium-157 atoms in the LGB:Ce scintillator, which then releases the capture energy in a characteristic cerium emission pulse. The measured captured pulses indicate the presence of neutrons. When a scintillating fluor is present in the plastic, the light pulse resulting from the neutron moderating in the plastic is paired with the LGB:Ce capture pulse to identify the energy of the neutron. About 2% of the impinging neutrons lose all of their energy in a single collision with the detector. There is a linear relationship between the pulse areas of this group of neutrons and energy. The other 98% of neutrons have a wide range of collision histories within the detector body. When these neutrons are 'binned' into energy groups, each group contains a distribution of pulse areas. This data was used to assist in the unfolding of the neutron spectra. The unfolded spectra were then validated with known spectra, at both neutron emitting isotopes and fission/accelerator facilities. Having validated spectra, the dose equivalent and dose rate are determined by applying standard, regulatory damage coefficients to the measured neutron counts for each energy bin of the spectra. Testing at the Los Alamos Neutron Science Center (LANSCE), Edwards Accelerator Laboratory (EAL) at Ohio University and the Radiation Center at University of Massachusetts-Lowell has demonstrated that the instrument can measure neutrons and their spectra over the range between 0.8 MeV and 150 MeV with an uncertainty of only ± 8%. An independent test of the LGB:Ce neutron spectrometer was conducted by a US Defense Threat Reduction Agency (DTRA) team at the Idaho National Laboratory (INL). The results of this evaluation showed that the neutron spectrometer accurately identified bare radioactive isotopes by their spectra. Further, masking and shielding materials alter those spectra in predictable ways that permit an extrapolation from the observed spectra back to the identity of the isotopic spectrum. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Hexagonal Boron Nitride: Physical Properties, Hydride Vapor‐Phase Epitaxy Growth of Large‐Diameter Quasi‐Bulk Wafers and Applications

Hexagonal boron nitride ( h ‐BN), with its ultrawide bandgap and 2D structure, holds an immense promise for advanced semiconductor applications. Scaling bulk crystals to large‐diameter wafers, crucial for complex device fabrication, remains a challenge with high temperature, high pressure, and metal flux solution methods. To address this, recent efforts have focused on hydride vapor‐phase epitaxy (HVPE) for producing large diameter thick h ‐BN quasi‐bulk wafers, reaching hundreds of micrometers. These HVPE‐grown quasi‐bulk crystals exhibit excellent c ‐axis long‐range order. Notably, the in‐plane mobility‐lifetime products for both electrons and holes surpass 10 −4 cm 2 V −1 , which are two orders of magnitude greater than the out‐of‐plane (vertical) values, highlighting the potential for high‐performance devices leveraging superior lateral transport. Lateral detectors fabricated from 100 μm thick B‐10 enriched h‐ BN wafers have achieved a record 60% thermal neutron detection efficiency. Based on its physical properties, h‐ BN appears to be an outstanding material of choice for light‐triggered electronic power switches capable of supporting high ‐ voltage and high ‐ power operations. These recent advancements in large‐diameter h ‐BN quasi‐bulk crystal growth, enabled by HVPE, pave the way for applications spanning deep UV photonics, high‐power electronics, high‐efficiency neutron detection, and quantum information technologies, establishing h ‐BN as both a versatile active semiconductor and an ideal substrate.

Jiang, Hongxing [Department of Electrical and Comp↗
DOE OSTI2011

MA-NRBC: First successful attempt for neutron gamma discrimination in plastic scintillators

In this paper, a new electronic hardware and algorithms enabling discrimination between neutron and gamma in plastic scintillators together with the first associated experimental results, are presented. This electronic platform is mainly based onto a quad 200 MHz ADCs. Using phase rotating, it is possible to sample the signal up to 800 MHz equivalent, with 8 bits precision. This sampling frequency allows a real time signal processing. Despite all previous work, we have shown during this study that it is possible to discriminate neutron from gamma in plastic scintillators even for low energy neutrons (less than 10 MeV). Two patents have been accepted and registered; the first deals with the intrinsic signal processing and the second with thermal stabilization methods of photomultiplier tubes. The system could be used up to 100 000 events per second (both gamma and neutron). This system is currently dedicated to homeland security devices; this is due to its response time (in the order of 1 up to 3 seconds). The next step is to implement the thermal stabilization algorithm in the FPGA and micro-controller to obtain a global system free from any trouble caused by the environment thermal variations. This aspect of the research is crucial for measurements in the field. The time response should also be improved to make it a reliable alternative to Helium-3 shortage for neutron detection at borders checkpoint. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

InstrumentationPod (IPOD) User Guide

This document describes the Instrumentation Pod (IPOD) and its operation and use. The IPOD is a low-power detector system comprising a 3He tube with preamp for neutron detection, a microcontroller-based data acquisition system, a GPS receiver for locationdetermination and time-synchronization, and power filtering and protection. The IPOD is intended to be bolted to the top of Dual-Use Casks stored at Baikal-1 in Kazakhstan in order to maintain continuity of knowledge of the materials stored within the cask. The data acquisition system receives pulses from the neutron-detection preamp, combines this information with other sensor data, and stores the result on two SD cards that are part of the data acquisition system. Firmware in the data acquisition system controls collection and storing of the data and enables configuration of the acquisition parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste

Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemens AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs, {sup 241}Am) were performed. A homemade algorithm was developed to determine a value which is related to the neutron absorption of the sample with the analysis of the raw detector data. The detector was placed 42 cm away from the neutron source. Distance between detector and the samples was 0.5 cm. At the sample position the fast neutron flux was estimated to 9x10{sup 3} n cm{sup -2} s{sup -1} for a neutron emission of 10{sup 8} n s{sup -1}. The acquisition time was 15 minutes. First neutron radiographs were successfully recorded despite the low detector efficiency and low neutron emission. Analysis of the data shows a correlation between the measured signal and determined neutron absorption. Thus discrimination between different materials of same thicknesses may be achieved. The measurements and results will be presented and discussed in details.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm{sup −1}, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Helium-3 Production via Lithium-6 Activation in an Accelerator-Driven Reactor

In this paper, the possibility of using an accelerator-driven subcritical reactor to produce helium-3 is explored. Current supply of helium-3 in the United States is running low. Helium-3 has many applications in neutron detection, high-energy physics, and national security, and has a growing demand in the scientific community for its properties. The main source of helium-3 in the United States is from dismantling nuclear arms, where tritium is allowed to decay into helium-3. There are no current, significant future plans for increasing helium-3 production. However, the projected demand of this isotope is expected to increase dramatically, with greater research into aneutronic fusion, and allotments of helium for the Spallation Neutron Source, and ITER expected in years to come. Tritium, with a half-life of 12.3 years, will take time to decay to helium-3, which means production needs to start now to counter the future deficit. This helium-3 production system sets out to be an economical, and safe solution for this future deficit. A zirconium-lithium mixture is utilized as a target for breeding helium-3. Specifically, the target rods will consist of lithium aluminate pellets with diameters ranging from 100 to 500 microns, dispersed within a zirconium matrix. Lithium targets in pellet form were chosen over a solid rod, or annulus, in order to reduce self-shielding effects within the lithium, and to further facilitate tritium loading and containment within the zirconium. Additionally, a stainless steel 316 cladding surrounds the target rods, to further reduce outgassing of helium. The core is made up of 6480 fuel pins, enriched to 4.75% wt% U-235/U, and 3660 lithium pins in mixed assemblies arranged in hexagonal lattices, with the lithium enriched to 75% lithium-6, and a total lithium loading of approximately 70 kg. An accelerator is used as a neutron source, firing 800 MeV protons at a liquid lead target loop. Neutronics analysis and burnup calculation were performed with the aid of MCNP6. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS2022

An Isolated Mass-gap Black Hole or Neutron Star Detected with Astrometric Microlensing

We present the analysis of five black hole candidates identified from gravitational microlensing surveys. Hubble Space Telescope astrometric data and densely sampled light curves from ground-based microlensing surveys are fit with a single-source, single-lens microlensing model in order to measure the mass and luminosity of each lens and determine if it is a black hole. One of the five targets (OGLE-2011-BLG-0462/MOA-2011-BLG-191 or OB110462 for short) shows a significant >1 mas coherent astrometric shift, little to no lens flux, and has an inferred lens mass of 1.6–4.4 M ⨀ . This makes OB110462 the first definitive discovery of a compact object through astrometric microlensing and it is most likely either a neutron star or a low-mass black hole. This compact-object lens is relatively nearby (0.70–1.92 kpc) and has a slow transverse motion of <30 kms -1 . OB110462 shows significant tension between models well fit to photometry versus astrometry, making it currently difficult to distinguish between a neutron star and a black hole. Additional observations and modeling with more complex system geometries, such as binary sources, are needed to resolve the puzzling nature of this object. For the remaining four candidates, the lens masses are <2M ⨀ , and they are unlikely to be black holes; two of the four are likely white dwarfs or neutron stars. We compare the full sample of five candidates to theoretical expectations on the number of black holes in the Milky Way (∼10 8 ) and find reasonable agreement given the small sample size.

Astrophysical black holes↗
DOE OSTI2012

Status Report on the Passive Neutron Enrichment Meter (PNEM) for UF 6 Cylinder Assay

The Passive Neutron Enrichment Meter (PNEM) is a nondestructive assay (NDA) system being developed at Los Alamos National Laboratory (LANL). It was designed to determine 235 U mass and enrichment of uranium hexafluoride (UF 6 ) in product, feed, and tails cylinders (i.e., 30B and 48Y cylinders). These cylinders are found in the nuclear fuel cycle at uranium conversion, enrichment, and fuel fabrication facilities. The PNEM is a 3 He-based neutron detection system that consists of two briefcase-sized detector pods. A photograph of the system during characterization at LANL is shown in Fig. 1.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Portable Neutron Sensors for Emergency Response Operations

This article presents the experimental work performed in the area of neutron detector development at the Remote Sensing Laboratory–Andrews Operations (RSL-AO) sponsored by the U.S. Department of Energy, National Nuclear Security Administration (NNSA) in the last four years. During the 1950s neutron detectors were developed mostly to characterize nuclear reactors where the neutron flux is high. Due to the indirect nature of neutron detection via interaction with other particles, neutron counting and neutron energy measurements have never been as precise as gamma-ray counting measurements and gamma-ray spectroscopy. This indirect nature is intrinsic to all neutron measurement endeavors (except perhaps for neutron spin-related experiments, viz. neutron spin-echo measurements where one obtains μeV energy resolution). In emergency response situations generally the count rates are low, and neutrons may be scattered around in inhomogeneous intervening materials. It is also true that neutron sensors are most efficient for the lowest energy neutrons, so it is not as easy to detect and count energetic neutrons. Most of the emergency response neutron detectors are offshoots of nuclear device diagnostics tools and special nuclear materials characterization equipment, because that is what is available commercially. These instruments mostly are laboratory equipment, and not field-deployable gear suited for mobile teams. Our goal is to design and prototype field-deployable, ruggedized, lightweight, efficient neutron detectors.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

Absolute photoneutron cross sections of Sm isotopes

Photoneutron cross sections for seven samarium isotopes, {sup 144}Sm, {sup 147}Sm, {sup 148}Sm, {sup 149}Sm, {sup 150}Sm, {sup 152}Sm and {sup 154}Sm, have been investigated near neutron emission threshold using quasimonochromatic laser-Compton scattering γ-rays produced at the synchrotron radiation facility NewSUBARU. The results are important for nuclear astrophysics calculations and also for probing γ-ray strength functions in the vicinity of neutron threshold. Here we describe the neutron detection system and we discuss the related data analysis and the necessary method improvements for adapting the current experimental method to the working parameters of the future Gamma Beam System of Extreme Light Infrastructure - Nuclear Physics facility.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Fusion Power measurement at ITER

Nuclear fusion research aims to provide energy for the future in a sustainable way and the ITER project scope is to demonstrate the feasibility of nuclear fusion energy. ITER is a nuclear experimental reactor based on a large scale fusion plasma (tokamak type) device generating Deuterium - Tritium (DT) fusion reactions with emission of 14 MeV neutrons producing up to 700 MW fusion power. The measurement of fusion power, i.e. total neutron emissivity, will play an important role for achieving ITER goals, in particular the fusion gain factor Q related to the reactor performance. Particular attention is given also to the development of the neutron calibration strategy whose main scope is to achieve the required accuracy of 10% for the measurement of fusion power. Neutron Flux Monitors located in diagnostic ports and inside the vacuum vessel will measure ITER total neutron emissivity, expected to range from 1014 n/s in Deuterium - Deuterium (DD) plasmas up to almost 10{sup 21} n/s in DT plasmas. The neutron detection systems as well all other ITER diagnostics have to withstand high nuclear radiation and electromagnetic fields as well ultrahigh vacuum and thermal loads. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗