Neutral Beam Diagnostics on FTU

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Neutral Beam Diagnostics on FTU

• De Angelis R.1, Charette E. 2 ,, Sarkissian A. 2,
  Stansfield B. 2, Zanza V. 1

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Outline

• Objectives
• Implementation Method
• Measurements Principle and Validation
• Diagnostics Principle and Hardware
• Beam on Test Stand
• Future Activities

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Objectives

• Study Current Profile Effects on MHD Stability of
  Tokamak Plasma gt Current Profile measurements
• Study Electric Field Effects on Confinement gt
  Impurity Rotation Velocity measurement
• Study Impurity Transport and Control gt Impurity
  Profile measurements

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Implementation

• Use Beam Emission Spectroscopy (Visible part of
  the spectrum) as Main Diagnostic Tool
• Use Fast Neutral Beam To Artificially Increase
  Neutral Particle Content in Plasma CORE
• Use Measurement of the Polarization angle of the
  emitted spectrum from Excited Fast Neutrals to
  measure the Poloidal magnetic Field Profile
  Motional Stark Effect (MSE)
• Use Modulated Beam to Increase Measurement
  Sensitivity

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Schematics of MSE

• Stark Components
• For observation ?E
• ? (?m0) ?? E
• ? (?m?1) ?E

????polariz(r) ? ES vNBI x Btot ? q(r)
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Beam Spectrum
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Detection Geometry Schematic In FTU
BT 6-8 T Ip 1 MA ne 10 20 m-3 Te 5
keV Ti 2 keV
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Method of Measurement
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Beam Parameters
E ? 40 keV Iioni ? 2.4 A Ieqneutri ? 1 A ? ?
0.4º/ beamlet, 20 mrad overall ?r?? 3cm Gas H2
, He Beam Fraction (50 H) gt Design
modification for improvement Beam Modulation 0
2kHz (Modulating Arc Current)

• DuoPIGatron Source
• Filament LaB6 (120 A) or W ?(? 1.5mm)
• Arc Current (lt60A) ne ? 5 1017 m 3 Te ?
  12 eV
• Extraction System 3 grigs (0,-45
  kV,-40 kV)
• Neutralizer PH2 5
  mTorr
• Main Power supply - 40kV, 2.5 A
• Auxiliary power supplies i, e ? 5kV, 1 A

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Validation of Operation Parameters
Fraction of Neutral Atom Beam density at Plasma
Centre nbeam /n0beam e-?nesTdl ?0.2 ,
sT40keV (ltsion,CX Vr1gtlts ion,e Vr2gt
ltsion,iVr3gt)/V nbeam I (1A)/e Vbeam (r
0R g)2. ? ? 3.51014 at/m 3 ltsvgtexc ltsvgtexc,e
ltsvgtexc,p ? 710-15 m3/s Beam excitation rate
d nexc /dt ne nbeam ltsvgtexc,e ni nbeam
ltsvgtexc,p 2 ni nbeam (ltsvgtexc,e ltsvgtexc,p)
? 21020 ((0.2)3.51014 ) 710-14 ? 1020
at/m3 /s Detected Photon flux d nexc
/dtVolumedetection solid angle ?
(1/4p)1020 at/m3 /s (2.10-4)10-2 ? 1013 Ph /s
B 2.51017 ph.m-2.str -1.s -1
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Beam Emission Spectroscopy
H0 Az --gt H A(Z-1)

• Ion Temperature
• He II ?4686 Å ?n4-3
• CVI ?5291 Å ?n8-7
• OVIII ?6068 Å ?n10-9
• Poloidal Rotation
• He II ?4686 Å ?n4-3

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Validations for Spectroscopic Measurements

• B ?cx (1/4?) ? lts vgtj? ò N Z N j dl

BminOMA 3 1015 ph./s/m 2 /ster (S/N 4)
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Beam Set Up on Beam Stand
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Gas Management System
Gas Flux ?H2 2 Torr. L/ s PPort 105 Torr SH2
? 20,000 l/s Pumping System Ti Sublimation
16,000 l/s Cryo Pum 22,500l/s
Getters 20,000l/s
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Cooling System
Cooling Tank 1000 l Cooling Capacity
5kW Deionized water Water Pumps 70 l/m For
source and extraction Grids 120 l/m For power
supplies
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Modified Electric Configuration
Electromagnetic Electron Trap Vs Electrostatic
Electron Trap
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Beam Diagnostics on Test Stand

• Visible spectroscopy Beam Composition
• Infrared Camera Beam Profile
• Thermocouple Array Beam Power and Profile

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Beam Diagnostics on Beam Stand (single Beamlet)
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Upcoming Development Plan

• Increase Beam Power to its Maximum
• 19 hole Extraction System
• Identify and Optimize Proton Fraction in the Beam
• Optimize Beam Divergence
• Comparisons between Two alternative Electrical
  Configurations
• Develop Cathode-less Source

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Future Plans

• Upgrade Beam Energy
• Upgrade Beam Current

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Thank You For Your Attention