1. Status and main challenges for detectors at fusion facilities Duarte Borba (presentation prepared by Andrea Murari) ERDIT (European Radiation Detection and Imaging Technologies) Meeting 11 and 12 April 2013 at CERN

2. Path to Fusion energy using Magnetic Confinement Device JET ITERDEMO Plasma Volume 80 m 3 800 m 3 ~ 1000 - 3500 m 3 Wall Surface ~150 m 2 ~700 m 2 ~ 2000 m 2 Fusion Power ~ 16 MW th ~ 500 MW th ~ 2000 - 4000 MW th Operation (1983 – Present) (in 2020s) (in 2040s)

3. Path to Fusion energy using Magnetic Confinement Device JET ITERDEMO neutron wall load (14 MeV) < 0.1 MW/m 2 4x10 16 n/m 2 /s ~ 0.5 MW/m 2 ~ 2x10 17 n/m 2 /s ~ 1-2 MW/m 2 ~ 4-8x10 17 n/m 2 /s Pulse Duration ~ 1s – 10s ~ 1000 s > 30 000s neutron fluence (14 MeV) ~ 4x10 16 n/m 2 per DT pulse ~ 2x10 20 n/m 2 per DT pulse > 10 22 n/m 2 per pulse

4. Operation with Deuterium-Tritium Current Tokamak operation uses only Deuterium. The last large scale Deuterium-Tritium (DT) operation took place on JET in 1997, with a next DT operation at JET proposed for around 2015 in preparation of the ITER DT operation foreseen for 2026. 1997 2015 2026 JET DT1JET DT2 ITER DT Radiation hardness of detectors and neutron measurements are key developments in fusion research in preparation of the next DT experiments on JET and on ITER. This presentation focus on the on going developments at JET required for DT operation, which are also relevant for ITER, focussing on  -ray, x-ray, and neutron measurements.

5. Overview Radiation Hard Hall probes for measurement of steady state magnetic fields Advanced detectors for  -ray spectroscopy Advanced detectors for neutron spectrometry Advanced electronics for neutron and  -ray counting Si on insulator detectors for neutral particle measurements GEM detectors and polycapillary optics Summary

6. Hall sensors resistance in radiation environment of neutron irradiation IBR-2 Joint Institute of Nuclear Research, Dubna, Russia WWR-M Petersburg Nuclear Physics Institute, Russia WWR-Ts Institute of Physical Chemistry, Obninsk, Russia LVR-15 Nuclear Research Institute, Řež, Czech Republic Sensor testing in ITER-relevant neutron fluxes is being performed in Nuclear reactors

7. Hall sensors resistance in radiation environment of neutron irradiation 1 – radiation-resistant sensor; 2 – conventional sensor InSb-based sensors are operable up to neutron fluences F = 5·10 18 cm -2 =5 10 22 m -2 which exceed maximum fluence in ex-vessel sensor locations at ITER F = 10 15 cm -2 → ΔS/S = 0.04% F = 10 16 cm -2 → ΔS/S = 0.08% F = 1017 cm-2 → ΔS/S = 5% F = 1018 cm-2 → ΔS/S = 10% Sensors sensitivity change vs. neutron fluence:

8. Radiation defectsNuclear doping Mutual compensation Acceptors Donors FastThermal Neutrons (97,5% of possible reactions) Radiation physical processes occurring in InSb-based Hall sensors under irradiation Semiconductor Minimal sensor parameter drift (subject to correction with dedicated electronic methods) Methods for stabilizing the semiconductor sensor parameters: Chemical doping of semiconductor materials (InSb, InAs) with the complex of doping impurities (donor, isovalent, rare-earth ones) up to optimal initial concentration of free charge carriers. Radiation modification – preliminary introduction of certain number of radiation defects.

9. Radiation-hard ex-vessel Hall Probe locations Hall sensors 6 Hall Probes with 18 Hall Sensors and 18 microsolenoids have been installed at JET High stable Hall sensor Microsolenoid coil 2mm

10. The 3 gamma-ray JET spectrometers based on Bismuth Germanate (BGO) and NaI (sodium iodide doped with thallium) Scintillator detectors, 2 of them in the Roof Lab, one in a tangential view, have limitations in: -Low Count rate, <50 kHz (total rate including a large neutron background component) -Low Energy resolution > 7% for the 662 keV gamma-rays from 137 Cs -Large neutron background sensitivity Gamma-ray spectrometry on JET Roof Lab ~4m

11. Gamma-ray spectrometry on JET Developments (goals and objectives) Improved energy resolution: better that 0.2% in the case of the HPGe (high-purity germanium) detector Improved time resolution. The key figure of merit is the count rate capability: it should exceed 0.5 MHz before pile- up and gain drifts begin to affect the detector response. Substantial neutron background reduction: a factor >100 neutron flux attenuation will be achieved for one of the detectors with the use of a LiH (lithium hydride) neutron attenuator.

12. New Detectors installed in Roof Lab Gammas & Neutrons Lanthanum Bromide scintillator LaBr3(Ce) Gammas & Neutrons High-resolution and High efficiency HPGe spectrometer

13. 3 He+ 12 C  p+ 14 N* (Q=4.8 MeV) Good description of the 1.63 MeV and 2.31 MeV peak for T 3He > 300 keV 13 HPGe Measurements in JET plasmas M. Tardocchi et al, PRL 107 (2011) 205002 Sum of 7 JET discharges: (#73760-73770) where minority 3 He ions n 3He =1-5%, are accelerated using Ion Cyclotron Resonant Heating P ICRH  5-6MW tuned at  3He in D plasma with electron density n e =2-3 10 19 m -3.

14. Demonstration of high counting rate LaBr3(Ce) Scintillator Lanthanum Bromide scintillator LaBr3(Ce) was tested at the nuclear accelerator facility in Romania for high counting rate experiments in preparation of the JET DT campaign. Measurement carried out at the Tandem Van der Graaf facility in Magurele (Romania). Spectrum of 10 MeV p beam on 27 Al target M. Tardocchi et al., IEEE Nuclear Science Symposium, Valencia, 2011 – contributed oral presentation M. Nocente et al., submitted to IEEE Trans. On Nucl. Science Rate = 2.6 MHz Implication for JET: capability to handle  -ray counting rates > 1 MHz (important for JET DT experiments) with lower energy resolution than HPGe but better radiation hardness properties

15. Construction and installation at JET of a dedicated compact neutron spectrometer”, composed of a Digital Pulse Shape Discrimination (DPSD) board, coupled to a NE213 scintillator detector provided with a LED for photomultiplier gain variation corrections Compact Neutron Spectrometer Development

16. JET Compact Neutron Spectrometer :Line of Sight Detector is located in a bunker with an horizontal line of sight which has a significant component tangential Compact Neutron Spectrometer NE213 scintillator Spilbine

17. Below is shown an example of optimization of the neutron / gamma rays separation settings in the LabView graphic environment (JET pulse No. 82723): Compact Neutron Spectrometer n 

18. New Boards for Neutron and Gamma ray Cameras The old neutron emission profile diagnostic (KN3) consists of two fan shaped arrays of collimators (10 horizontal + 9 vertical lines of sight. Each line of sight has 3 detector systems based on scintillators: 1)NE213 liquid scintillator with analog pulse shape discrimination (PSD) electronics for recording of 2.5 MeV and 14 MeV neutrons; 2) BC418 plastic scintillator for 14 MeV detection; 3) CsI(Tl) scintillator for gamma emission measurements in the energy range 0.2-6 MeV.

19. New Data Aquisition Boards for Neutron Cameras Replacement of the analog PSDs and data acquisition/processing for the Neutron yield profile monitor 19 neutron channels (based on NE213 scintillators). For each line of sight: a) Digital acquisition with 14-bit ADC with 200 MSamples/s; b) on-line processing on FPGA (data reduction, real time count rates); c) full data processing (neutron /gamma separation, PHA spectra, calibration, etc.) with dedicated software package running on the CODAC PCs d) handling of pile-up (rejection and software correction); e) possibility of correcting for the contribution from 14 MeV neutrons to the 2.5 MeV neutron emission; f) real-time outputs.

20. Project Goals Provide a modern DAQ system for gamma-rays cameras (acquiring simultaneously hard X-rays and gamma-rays); Improving pulse identification by presenting spectra covering the energy range of 150 keV (best case) to 8 MeV; Proving the ability of the system to process data in real-time and transferring the energy values in real-time through PCIe links to the host Input Channels 19 channels for both hard X-rays and  -rays RT capability1 ATM card for RTNET Pre-AmplifiersNone ATCA infra-structure1 ATCA crate 1 ATCA controller card 1 RTM PSU card Digitizer Cards3 cards (24 channels)  19 channels  5 spare channels New Data Aquisition Boards for  -rays Cameras IST-Portugal

21. 21 Fast digital acquisition Hardware Digitizer Card ATM Card Controller Card RTM Card

22. Neutral Particle Analiser Active area 7 x 10 mm –64 strips with 110  m pitch Two types: 6  m and 25  m thickness for top layer –Thin detectors 6  m is thinnest possible, –Thick detectors 25  m range of high energy protons p + stop p- bulk p + contact insulator Si substrate n+ strip Al contact Oxide coating (40 nm) 110 m 6 & 25 m <0.5 m Si on Insulator technology for the first time implemented on JET Detector structure

23. Neutral Particle Analiser Detectors UHV Flange Preamplifiers thin thick Implementation of the upgrade

24. Ions vs. background Thick detectors (25 µm) Detectors 3,4,5 neutron background Thick detectors show some sensitivity to neutron-induced background, some overlap with Channel 3 ion signal Counts per 100 ADC bins Pulse height [ADC bins]

25. Use of GEM Detectors Pick-up coils have problems in a radiation hard environment (close to the plasma, integrators etc) The next generation of plasmas will be so hot that even the boundary will emit in the Soft X-Rays Adapt Gas Electron Multiplier detectors Current~few nA Cathode Anode Plasma Boundary with reconstruction using Soft X-Ray emission 2 GEM Detectors are installed on JET looking at W and Ni Lines

26. Use of polycapillary X-ray optics The use of Polycapillary lenses enables the location of the detectors far from the plasma. Polycapillary optics are comprised of 10 4 -10 6 hollow glass channels bundled together. X-ray photons propagate in the hollow space of the capillary channels by the process of total reflection at the glass surface. Polycapillary X-ray lenses Not used at JET at present but some developments supported

27. Summary A key aspect in developing the next generation of detectors for applications on Fusion Research is the increase in the neutron yield in the next generation of Fusion experiments. The measurement of neutrons,  -rays, x-rays by radiation hardened detectors will be very important for next step Fusion devices such as ITER.