Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor

Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies

Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor

Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies

In-situ gamma irradiation testing of radiation hardened chips till 1 MGy

Ten samples of a custom tailored Mega-Gray hardened resolver/LVDT-to-digital converter, a resistive base sensor-to-digital converter and a RS485 communication application specific integrated circuit (ASIC) were combined in 1 irradiation campaign for Fusion for Energy (Barcelona, Spain). Radiation resistance of these ASICs, developed by Magics Instruments (Geel, Belgium) for Fusion for Energy, was assessed for a total ionizing dose (TID) above 1 MGy using the Co-60 gamma underwater irradiation test facility at SCK CEN (Mol, Belgium). The 3 different ASICs were irradiated at an average dose rate of 484 Gy/h and their performance was continuously measured (in-situ) during 97 irradiation days. A fully autonomous and modular test setup was developed to perform these measurements and ensure continuous operation by implementing a recovery and warning system in case of failure to restrict measurement data loss to minimum. An in-situ post-irradiation assessment was performed afterwards to observe recovery from the irradiation in a socalled annealing phase. Annealing was done for seven days at room temperature followed by another 7 days of high temperature annealing at 100 °C to accelerate the recovery effect. During the full test campaign all data was saved in a database, post-processed with Python into readable plots to deduct possible performance shifts due to the irradiation and afterwards during recovery. During the complete testing campaign of these ASICs the ESCC22900 (Total Dose Steady-State Irradiation Test Method) standard was followed

R&D on ITER in-vessel magnetic sensors

This paper summarizes the progress of R&D activities related to the design of in-vessel magnetic sensors for measurement of the equilibrium field in ITER and the associated mechanical support and connection system. The background to the design activities, developed in the last few years in the framework of several collaborations, is provided in the introduction. The paper focuses on the experimental results obtained from a set of sensor prototypes, recently manufactured and tested, and on numerical simulations performed in order to verify the compliance of the sensors with ITER requirements. The paper finally illustrates the status of the engineering analyses performed to progress the design of the support and connection system, conceived to be replaceable by remote handling. In conclusion, specific issues which require further developments to achieve the final design are outlined

Study of the Stability of 4H-SiC Detectors by Thermal Neutron Irradiation

International audienceTwo types of 4H-SiC semiconductor detectors (D1 and D2) are realized based on ion implantation of 10B inside the aluminum metallic contact. The first detector shows a high leakage current after 10B implantation and low signal to noise ratio. However, improvements concerning the implantation parameters led to lower leakage current and thus to higher signal to noise ratio. Moreover such detectors show their stability under different thermal neutron fluxes showing the reproducible features of the pulse height spectra and same electrical behaviour before and after irradiation

A MGy, Low-Offset Programmable Instrumentation Amplifier IC for Nuclear Applications

This paper shows a customized MGy radiation tolerant instrumentation amplifier. The 65 nm CMOS-based ASIC amplifier has an offset smaller than 1 µV and a noise level below 50 nV/√Hz from DC. It consumes less than 5 mW and has a common-mode-rejection-ratio larger the 100 dB. In addition, it allows a programmable gain setting from 8,16,32,64,128 to 256. The performance of this instrumentation amplifier was monitored during an on-line radiation experiment up to a total ionizing dose larger than 1 MGy, enabling the read-out of the most common nuclear temperature and position sensors.status: publishe

A 1 MGy TID Radiation-Tolerant 56 µW CMOS Temperature Sensor with ±1.7°C Accuracy

The total-ionizing-dose (TID) radiation tolerance of CMOS temperature sensors is generally limited by the radiation-introduced leakage current in diodes. A dynamic base leakage compensation technique is employed to improve the radiation hardness of the CMOS temperature sensor. The fabricated temperature sensor achieves an accuracy of ±1.7°C from -40°C to 125°C, while the power and area consumption are only 56 μW and 0.07 mm2, respectively. The temperature sensor is assessed with a gamma irradiation experiment with a dose rate of 1 kGy/h, and radiation induced temperature readout drifts are smaller than 0.2% after 1 MGy.status: publishe

MGy Radiation Assessment of a Space-Graded Amplifier and ADC

This paper shows a high total dose radiation assessment on a set of space qualified components. Two space graded COTS (Commercial off-the-shelf) components were selected and monitored under 60Co gamma radiation, namely an instrumentation amplifier and a 14 bit analogue-to-digital-converter (ADC). The specifications of these COTS components were monitored on-line with a customized test bed, up-to a total ionizing dose larger than 1 MGy and are presented in this paper.status: publishe