RFP Workshop Stockholm 9-11 / 10 / Power Neutral Beam on RFX-mod: Design and Mission M Valisa, M Gobbin, L Grando, L Marrelli, S Martini, R Piovan, A Rizzolo, P. Zaccaria and the RFX team Consorzio RFX Y. Hirano, S. Kiyama, H. Sakakita AIST Tsukuba

RFP Workshop Stockholm 9-11 / 10 / OUTLINE - Mission : to study physics of energetic particles on RFX - Design status : 1. Issues to be solved to connect the AIST beam on to RFX-mod 2. Diagnostics to be implemented for the beam exploitment Outline

RFP Workshop Stockholm 9-11 / 10 / Advanced scenarios have been reached in Tokamaks by controlling the current profile. Methods include use of neutral beams and radio frequency injection As in Tokamkas, auxiliary power can be used in RFP’s to optimize plasma control and performance and widen the physics studies. MST ( Madison, Wisconsin) is testing - Lower Hybrid & Berstein waves & Neutral Beam Injection for current drive and heating (25keVx40A) TPE-RX (Japan) has developed a 1.2 MW neutral beam injector. Motivation

RFP Workshop Stockholm 9-11 / 10 / TPE-RX (*) has been dismantled (Jan 2008). Unique opportunity to loan their Neutral Beam. Beam characteristics Positive Ion source (filament type) Energy : 25 keV Ion Current : 50 A Pulse Duration : 30 ms The TPE-RX beam is available (*) AIST – Tsukuba Japan

RFP Workshop Stockholm 9-11 / 10 / Strong focussing: 4 cm of minimum waist Suitable to fit the existing RFX-mod ports( mm) The TPE-RX beam

RFP Workshop Stockholm 9-11 / 10 / The TPE RX Neutral Beam Injector Source Expansion chamber

RFP Workshop Stockholm 9-11 / 10 / The TPE RX Neutral Beam Injector

RFP Workshop Stockholm 9-11 / 10 / The power supply

RFP Workshop Stockholm 9-11 / 10 / Plasma heating Momentum injection Current drive Control of MHD dynamo and tearing activity. Fast particle confinement, beta and instabilities. ( Alfven mode excitation by fast ions. In particular, mediation of energy transfer to thermal ions) Core particle source Scientific objectives

RFP Workshop Stockholm 9-11 / 10 / On RFX only radial injection possible

RFP Workshop Stockholm 9-11 / 10 / The initial pitch of the particle is zero (but for the beam divergence): the initial velocity is mainly perpendicular to the field ( apart from the large divergence term). Particles ionized on the Low Field side are deeply trapped. Particles ionized beyond the axis are passing.  Current and momentum drive is low Detailed simulation of the experiment to be done shortly  evaluate best position for diagnostics Consequences of the radial injection R, cm Z, cm (ORBIT simulation by M. Gobbin)

RFP Workshop Stockholm 9-11 / 10 / Because of the 25 keV, shine-through issues are not severe for the RFX densities Beam attenuation (ADAS data / flat density profile) In RFX a(minor radius) = m

RFP Workshop Stockholm 9-11 / 10 / Heating 1 MW of injected power in standard discharges is marginal to be sizeable on top of the typical RFX input power > 10 MW. Slowing down time is ms, against a confinement time of approx 3 ms, so that heat release is diluted in time. Heating efficiency will be low Perhaps some effect during enhanced confinement regimes (QSH, PPCD, OPCD..) with reuced input power. 2 MA From P. Innocente et al RFP workshop 2008, Stockholm

RFP Workshop Stockholm 9-11 / 10 / Fast Ion Physics Relevance: Sufficient confinement of fast ions (MeV) is a mandatory requisite of burning plasmas. Collective modes excited by fast ions can enhance energy and momentum losses and cause wall damage Long time-scale non linear processes are expected from interaction of collective modes and fast ion dynamics as well as between drift waves and turbulent transport Fast Ion Physics

RFP Workshop Stockholm 9-11 / 10 / In MST 25 keV particles have exp. confinement times ( 30 ms)! Fiksel G. et al 2005 Phys. Rev. Lett Fast Ion Physics >Neutron emission in MST after beam short pulse MST

RFP Workshop Stockholm 9-11 / 10 / Estimated Slowing down time in RFX-mod ~ ms (Simulations in progress including main losses mechanisms, i.e. mg perturbations, ripple, CX etc.) Gobbin et al Nucl. Fusion 48 (2008) Fast Ion Physics

RFP Workshop Stockholm 9-11 / 10 / Design and construction of a new mechanical interface (expansion chamber and stand). Is a Residual Ion Dump necessary? Design of a new magnetic shield for the source and the neutralizer (higher stray fields on RFX than on TPE) Design of the power supply layout and connection to the beam Procurement and installation of ancillary equipment (cooling, gas valve PS etc) Integration in the RFX timing sequence Personnel training (Collaboration from TPE RX expected ) Development of kinetic models for simulation and interpretation (Colalboration with MST would be helpful) Development of diagnostics Installation on RFX not trivial

RFP Workshop Stockholm 9-11 / 10 / Max filed tolerated in ion source ~ 0.5mT neutralizer ~ 1mT Source neutralizer Screening mg fields Filaments are ON 30 sec before pulse Therefore must stand the field generated by the magnetizing windings (60 mT) during charging time( few sec.s) before the RFX-mod discharge Screen must not perturbe the RFX field. ongoing work

RFP Workshop Stockholm 9-11 / 10 / NBI diagnostics An NPA diagnostic presently being procured for general T i measurements on RFX-mod will also be used to study fast ions produced by the power NBI Development/ procurement of a Fast Ion Losses Diagnostic (FILD) to directly study the losses due to instabilities. Neutron diagnostic only if D operation will be permitted CERS will be expanded to the power beam. Diagnostics

RFP Workshop Stockholm 9-11 / 10 / Currently discussing about the use of the old NPA of RFX ( originally built for JET in the early 80’s) and the loan of a ACORD model (IOFFE Institute) from Greiswald (IPP COLLABORATION) in view of (possibly) the procurement of a Compact NPA ( IOFFE) NPA IOFFE INSTITUTE Old JET NPA efficiency vs neutr. pressure ( high –top – and low – bottom energies)

RFP Workshop Stockholm 9-11 / 10 / Fast Ion Losses Diagnostic FILD allows to directly study the losses due to instabilities. Scheme as in JET and ADEX-U: magnetic spectrometer disperses fast ions onto a scintillator, the strike point depending on gyroradius and pitch angle. Detector head: 3-dimensional ion collimator, stainless steel plate coated with scintillator powder and a graphite cap. Collimator geometry to be optimized by simulating typical particle trajectories of interest.

RFP Workshop Stockholm 9-11 / 10 / Alternatively: Faraday cup collector Alternatively FILD realized with Faraday foil collectors: Charged particles penetrate a stack of conducting foils, separated by insulating foils. Number of foils passed before being stopped and generating a current signal depends on their energy.

RFP Workshop Stockholm 9-11 / 10 / Timeline Delivery Autumn 2008 Installation Winter 2008 /Spring 2009 ( various steps during RFX ordinary maintainance periods) Commissioning/connection to RFX Summer/Autumn 2009 Installation of related diagnostics Autumn/Winter 2009 Operation Winter 2009 / early 2010 Timeline (Temptative