Summary of the Workshop on Alpha-Particle Effects in the Engineering Test Reactor - June 15-16, 1987 - Workshop Report

Aug 28, 2026

Workshop proceedings summarize key findings on alpha-particle effects in engineering test reactor (ETR) plasmas, aimed at supporting U.S. Department of Energy program planning. Thirty experts review alpha physics for tokamak reactors, covering session topics including overview context, slowing down and instabilities, ripple trapping and losses, alpha ash transport and control, burn control, and data-base and design implications. Discussions address MHD self-consistency at ignition constraints, alpha-driven modes such as fishbones and Alfvén eigenmodes, and consequences for confinement and heating power.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

Introduction

Slowing Down and Instabilities

Overview

Alpha Ash Transport and Control

Burn Control

Alpha Physics Data Base and ETR Design Implications

# MEETING REPORT SUMMARY OF THE WORKSHOP ONALPHA-PARTICLE EFFECTS IN THEENGINEERING TEST REACTOR,GERMANTOWN,MARYLAND,JUNE 15-16,1987 ## INTRODUCTION Much has been gained in understanding the role of alphaparticles in tokamak reactors since Kolesnichenko reviewedthe subject in 1980(Ref.1).The Göteborg symposium on therole of alpha particles in magnetically confined plasmasupdated the progress in 1986(Refs.2 and 3).The objectiveof the present workshop was to further elucidate alphaphysics in tokamak reactors by bringing together 30 expertsin the field and to identify Engineering Test Reactor (ETR)alpha physics issues for program planning by the U.S.Department of Energy(DOE).The meeting was organized by G.H.Miley(University of Illinois)under the auspices of theIgnition Physics Study Group of the Compact Ignition Toka-mak (CIT)project and the U.S.International ThermonuclearExperimental Reactor(ITER)studies.L.M.Hively [OakRidge National Laboratory(ORNL)]was the meeting coor-dinator.D.J.Sigmar [Massachusetts Institute of Technol-ogy(MIT)]chaired the final panel that drew together all ofthe findings and recommendations for this summary.Thisreport contains the salient points of the workshop papers;complete papers from the workshop appear in this issue ofFusion Technology after this summary. The workshop was divided into six sessions: 1.overview 2.slowing down and instabilities 3.ripple trapping and losses 4.alpha ash transport and control 5.burn control 6.alpha physics data base and ETR design implications. Subsequent sections of this report describe each of thesesessions in turn. 0VERVIEW The first session provided an overview of the context ofprogram planning,international research,and the scope ofalpha physics issues.R.J.Dowling(DOE)described presentETR research and the prospects for international collabora-tion on ITER.L.J.Perkins [Lawrence Livermore NationalLaboratory (LLNL)]discussed the design parameters,philos-ophy,and phases of machine operation.L.M.Hively(ORNL)explained the workshop objectives and summarizedthe alpha physics issues(see Table I). D.J.Sigmar(MIT)addressed the self-consistency ofresistive tokamak plasmas at ignition,as constrained by idealmagnetohydrodynamic(MHD)stability at finite beta.For anohmically driven current,MHD stability requires that theelectron temperature profile be much flatter than parabolicfor times longer than the skin time.However,this require-ment conflicts with the ion temperature profile being morepeaked than parabolic due to the large amount of fusion-generated alpha heating in the core.The conflict is.exacer-bated when beta is close to the MHD stability limit andtherefore argues in favor of large aB²designs.Applyingcurrent drive and electron cyclotron resonance heating(ECRH)sources may mitigate the problem.This area needssubstantial development. ## SLOWING DOWN AND INSTABILITIES B.Coppi(MIT)discussed alpha fishbone oscillationsarising from an internal,ideal m=1mode centered at q= 1,which is finite Larmor radius stabilized in the absence ofdissipative terms.However,the trapped alpha precessionalresonance provides a destabilizing effective viscosity,allow-ing alphas to slow down to ～400 keV before they areresonantly lost.The scattering of these intermediate energyparticles should not degrade the alpha-particle heating powersignificantly.On the other hand,the nonresonant loss of the 3.5-MeV alphas in the fluctuating field associated with thisinstability may have more serious consequences.This theorycontrasts with the Princeton fishbone theory,which predictsdirect,resonant,fast alpha losses near 3.5 MeV. J.W.van Dam(Institute for Fusion Studies)summarizedthe global Alfvén eigenmode,the shear Alfvén gap mode,and the ballooning mode;simple estimates show that all are aHere,1 is most critical or uncertain and 3 is least critical or uncertain. Here,1=needed before conceptual design,2=needed before start of construction,and 3=needed before operation.dHere,1

FAQs

What was the objective of the workshop on alpha-particle effects in the ETR?

The workshop aimed to further elucidate alpha physics in tokamak reactors and identify ETR alpha-physics issues for U.S. Department of Energy program planning.

How do alpha particles affect plasma stability at ignition according to the report?

The report discusses tensions between resistive tokamak self-consistency at ignition and ideal MHD stability constraints, including how alpha heating conflicts with temperature-profile requirements and motivates design considerations.

What kinds of instabilities and loss mechanisms were examined?

The report covers slowing-down-related instabilities such as fishbone oscillations and examines resonant versus nonresonant alpha losses, alongside effects on various global and shear Alfvén-related modes.

Aug 28, 2026

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