Diamond Neutral Par0cles Spectrometer at JET and proposal for ITER

Transcription

1 Diamond Neutral Par0cles Spectrometer at JET and proposal for ITER V. Krasilnikov, V. Amosov, Yu Kaschuck, N. Marcenko, A. Krasilnikov. (TRINITI, Russia) I. Coffey, S. Popovichev, M. Beldishevski (EFDA JET,UKAEA, UK)

2 Aims Charge exchange atom spectroscopy with high temporal resolu5on applies to study effec0veness of addi0onal hea0ng, interac0on of plasma instabili0es with fast ion component. Demanded spectroscopy temporal resolu5on ~ 1 ms. Demanded energy resolu5on < ~ 10 kev Demanded peak count rates ~ cps Sept 2011, Aus0n 12th IAEA Technical Mee0ng on Energe0c Par0cles in Magne0c Confinement Systems NDD, TFTR (1997) 2

3 Diamond Detector (DD) Diamond has unique proper5es that enable it to be effec0vely used as a sensi0ve element in the high energy par0cle detectors. 5,5 ev energy band gap >10 15 Ohm*m electrical resistance 10 7 V/cm breakdown voltage 2x10 7 cm/s saturated driy velocity ns charge collec0on 0me The diamond detector is a semiconductor detector with a thin (10 nm) front contact. The contacts are made of gold. The DD is sensi0ve to atoms, neutrons and gamma rays. Atoms. Reaching the detector, atoms instantly become ionized, and slow down on electrons, genera0ng electron hole pairs. The pair crea0on energy is 13.2 ev. The energy resolu0on of the spectrometer, measured with 5.5 MeV alpha par0cles 241 Am source is 50 kev. 5.5 MeV alpha par0cles mean free path length in diamond is 13μm. Fusion neutrons with energy 14.1 MeV reaching the diamond, enter into the following reac0ons with 12 C: elas0c (the cross sec0on of 800 mb, the threshold of 0 MeV) and inelas0c (200 mb, 4.8 MeV) sca`ering, a series of reac0ons with the forma0on of a neutron and three alpha par0cles 12 C (n, n') 3 4 He (217 ±52 mb, the minimum threshold of 8.29 MeV) and reac0on without the secondary neutron 12 C (n, α 0 ) 9 Be (72 mb, 6.19 MeV, reac0on energy 5.7 MeV). Neutrons with energy 2.5 MeV undergo only elas0c sca`ering. Gamma rays can create Compton electrons in a diamond. For this reason DD is sensi0ve to gamma rays but fortunately the sensi0vity is rather low. 12th IAEA Technical Mee0ng on 7 10 Sept 2011, Aus0n 3 Energe0c Par0cles in Magne0c Confinement Systems

4 Spectroscopy electronics DD Preamplifier Broadband Amplifier Fast ADC Digital signal processing Spectrum The very new spectroscopy amplifiers and pulse analyzers are capable of processing par0cle fluxes of up to 107 cps. They require extremely low noise condi5ons. Specially designed electronics Preamplifier Supply unit allows to digi0ze and process signal with count rates up to 106 cps at rela5vely high noise levels Sept 2011, Aus0n 12th IAEA Technical Mee0ng on Energe0c Par0cles in Magne0c Confinement Systems 4

5 Geometry and arrangement 5

6 JET shot Sept 2011, Aus0n 12th IAEA Technical Mee0ng on Energe0c Par0cles in Magne0c Confinement Systems 6

7 C27 JET experiments S He4 majority, H minority NBI gas He4 Ip 1.7 MA, TF 2.6 T. ICRH resonance (33, 37 MHz) H, 1 st harmonic 7

8 C27 JET experiments H H majority, He 3 minority 1-3% NBI gas D Ip 1.8 MA, TF 3.3 T. ICRH resonance (33, 42, 51 MHz) H, 1 st harmonic (and D 2 nd harm.) He3 - Inner Wall Resonance NIB4 PINI kev NIB8 PINIs 6, 7 88 kev 8

9 Proposal for ITER 9

10 Proposal for ITER Two diamond detectors (DDs) are to be installed in the vacuum pipe of the NPA system, in front of the High Energy Neutral Par0cle Analyzer (HENPA), combined with the front mirror of the H alpha diagnos0c. 10

11 Induc5ve mode Steady state Induc5ve mode Steady state Diamond size: Proposal for ITER D plasma Ø3 x mm Ø8 x mm Neutrons coun0ng rate 1.0e+4 7.1e+4 Gamma coun0ng rate 1.7e+3 1.2e+4 D coun0ng rate (0.1 2MeV) 7.0e+4 5.0e+5 T coun0ng rate (0.1 2MeV) 2.3e+1 1.6e+2 D coun0ng rate (0.1 2MeV) 5.0e+5 3.0e+6 T coun0ng rate (0.1 2MeV) 2.0e+2 1.6e+3 D T plasma (ra5o 1:1) Neutrons coun0ng rate 1e+6 7.1e+7 Gamma coun0ng rate 7e+5 5e+7 D coun0ng rate (0.1 2MeV) 3.5e+4 2.4e+5 T coun0ng rate (0.1 2MeV) 1.0e+4 7.5e+4 D coun0ng rate (0.1 2MeV) 2.3e+5 1.6e+6 T coun0ng rate (0.1 2MeV) 1.5e+5 1.0e+6 Total diamond detector DT neutron pulse height spectrum. Reac0ons: 1 Elas0c and non elas0c sca`ering, 2 12 C (n, n') 3 4 He 3-12 C (n, α 0 ) 9 Be 11

12 Conclusions Digital charge-exchange atoms spectrometer based on Natural diamond detector has been developed, calibrated and applied for studies of high energy ion behavior at JET tokamak. Original digital signal processing techniques implemented in the spectrometer. Particle fluxes and spectra detected in different additional plasma heating scenarios RF heating of the hydrogen minority in helium-4 plasma with tail formation in the energy range up to 500 kev was observed RF heating of the beam injected deuterons in hydrogen (majority) helium-3 (minority) plasma with tail formation in the energy range up to 250 kev was observed The Diamond Neutral Particle Spectrometer is proposed for ITER tokamak as a supplementary part of the NPA system. 12