How robust is the high energy beam

Howrobustisthehighenergy
beam-plasmainterac6on?
NormanRostokerMemorialSymposium
FairmontHotel,NewportBeach,Aug.24,2015
ToshiTajima,UCIrvine(alsoatTAE)
IndedicaFontothelateProfessorNormanRostoker
Acknowledgements:G.Mourou,F.Mako,A.Necas,R.Magee,E.Trask,T.Roche,B.Deng,X.Yan,M.Binderbauer,S.Ichimaru,thelateJ.M.
Dawson,X.M.Zhang,Y.M.Shin,D.Farinella,T.Saeki,N.Naumova,K.Nakajima,S.Bulanov,A.Suzuki,T.Ebisuzaki,J.Koga,X.Q.Yan,M.L.
Zhang,U.Wienands,U.Uggerhoj,A.Chao,N.V.Zamfir,V.Shiltsev,M.Hogan,P.Taborek,K.Abazajian,G.Yodh,S.Barwick,Z.Lin,W.Heidbrink,
70thBirthday
L.Chen,S.Nickes,T.O’Neil,R.Kulsrud,M.Yamada,D.Hammer,M.Spiro,R.Heuer,A.Caldwell,K.Abazajian,N.Canac,B.Richter,A.Penzias
Confluenceofacceleratorandplasma:
plasma-drivenacceleratorand
accelerator-drivenplasma
•  CollecFveaccelerator(Norman’slab,1970’s)
•  HistoryofplasmaacceleraFon
•  Tsunamiwavevs.wakewave(theissueofhighphase
velocity)----Tajima-Dawsonfield
•  Beam-drivenTAEFRC(FieldReversedConfiguraFon):beamplasmainstabilityhelpstoincreasefusionreacFvity
•  Recentphenomenologyofthebeam-drivenTAEFRC:
recurrentmini-bursts
•  EmergingConjectureofHighPhase-Velocity
Plasma-drivenaccelerators
70thBirthday
Collec6veaccelerators
Professor N. Rostoker
(1960’s Cornell; ~ 70’s UCI)
Acceleration by plasma wake waves
Collective acceleration suggested:
Veksler (1956, CERN)
(ion energy)~ (M/m)(electron energy)
V.Veksler
Many experimental attempts
of plasma acceleration (~’70s,
Rostoker’s lab UCI included)
led to no such amplification
(ion energy)~ (2α+1)x(electron) Mako-Tajima (UCI) analysis (1978;1984)
sudden acceleration, ions untrapped,
electrons return, while some run away
→ #1 gradual acceleration necessary
→ Tajima-Dawson (1979, UCLA) wakefield
#2 electron acceleration possible
with trapping (with TajimaDawson field), more tolerant for
sudden process
J.Dawson
Target Normal Sheath Acceleration (LLNL)
laser-driven ion acceleration (2000)
Adiabatic (Gradual) Acceleration
From lesson of the Mako-Tajima problem
Accelerating structure
↓
Inefficient if
suddenly
accelerated
↓
protons ↑
Accelerating structure
↓
(cf.human trapping width:
vtr,human ~ 1m/s << cs )
Efficient
when
gradually
accelerated
Lesson: gradual acceleration → Relevant for ions
LaserWakefield(LWFA):
Wakephasevelocity>>watermovementspeedTsunamiphasevelocitybecomes~0,
itcauseswavebreakanddamage
vs
Strongbeam(oflaser/parFcles)drivesplasmawavestosaturaFonamplitude:E = mωvph /e Wave breaks at v＜c
No wave breaks and wake peaks at v≈c
←
relativity
regularizes
(relativistic coherence)
Relativistic coherence enhances beyond the Tajima-Dawson field E = mωpc /e (~ GeV/cm)
Enablingtechnology:laserrevoluFon
G.Mourouinvented“ChirpedPulseAmplificaFon”in1985
LaserintensityexponenFatedsincethen,
tomatchtherequiredlaserintensityforTajima-Dawson’sLWFA
Demonstra6onandRealiza6onof
laserwakefieldaccelerators
threepapersonlaserplasmaaccelerator
(2006,Nature)
9
Typicallaserandplasmaaccelerator(Michigan)
Accelerator-drivenplasma
70thBirthday
Beam-drivenplasma(FRC)
TAE’sC-2Umachine+beams
6beamsystems
15keV
10+MW
20degreeangle
Operatewith:
•  Hydrogen–H
•  Deuterium–D
•  MixtureofH/D
FRCplasma+coils
Beams(only4
visible)
PriortoFlt.
Quiescentplasma
DestrucFveFltmode
starts
Beam
stabilizes
Quiescentplasma
recovery
H.Y.Guoetal.,NatureComm.,2014
Plasmaconfinementimprovesdrama6cally
inbeam-drivenFRC(TAE)
ParFcleconfinementFme
ElectronenergyconfinementFme
2.0
400
1.5
TAE
1.0
0.5
0
⌧Ee (ms)
500
Measured ⌧N (ms)
2.5
300
200
100
0.1 0.2 0.3 0.4 0.5
FRC scaling ⌧N (ms) ⇠ rs2 n1/2
0
TAE
0.05
0.10
0.15
0.20
Te (keV)
Guo,Tajima,Trask,etal.
3000
TAE2015PoPPaper
2000
Nexthighestpaper
July-2015
0
June-2015
1000
May-2015
NumberofFmespaperaccessed
HugeaccessnumbersincepublicaFoninMay2015
tothepaperonthebeam-drivenFRC:
4000
ThisTAEFRCreports:Thebeam-drivenFRCcapable
(1)stabilizedangerousFltinstability
(2)increaseconfinementFmedramaFcally
M.Binderbaueret.al.,PoP22.5(2015):056110
0
without NB
TAEC-2observes100foldsneutronyieldoverD-D
with NB
thermonuclearyieldduetothebeam-plasma
0
3
2
200 1
0
0
2
t (ms)
1
t (ms)
5
4
3
2
3
neutron rate (s-1)
Ti (eV)
109
400
density (10 cm )
4
measured (w/o NB)
thermonuclear (w/o NB)
measured (w/ NB)
thermonuclear (w/ NB)
600
-3
5
109
without NB
with NB
800
13
0
0
0
1000
neutron rate (s-1)
0
measurement (w/o NB)
calculation (w/o NB)
measurement (w/ NB)
calculation (w/ NB)
108
Courtesy: R. Magee
0
108
3
2
1
0
0
107
0
107 1
0
2
t (ms)
3
1
2
1
2
3
t (ms)
1
t (ms)
0 •  Shotw/ohydrogenNB(black)hasneutronyieldconsistentwiththermonuclear
calculaFon.
0
1
2
3
•  Shotw/hydrogenNB(red)hasneutronyieldabovethermonuclear.
t (ms)
3
D-Dfusionenhancedby100Fmesormore
byinjectedH-beaminTAEFRC:
q  TAE hydrogen beam-driven FRC deuteron plasma: fusion reactivity
enhanced by 100 -1000 over thermonuclear expected value, when
beam is sufficiently strong!
C-2UExp.
experiment
theory(ωpe/ωce=1)
theory(ωpe/ωce=5)
(Courtesy:A.NecasandR.Magee)
q  Beam-driven plasma instability (theory) can enhance fusion!
PlasmawithperpendicularbeaminjecFon:vb>>vth(PICset-up)
o 
o 
o 
o 
o 
o 
o 
1D3V code: 1 spatial and 3 velocity dimensions. !
Lorentz & Maxwell equations.!
Fully electromagnetic, can be run in electrostatic mode.!
Beam is initiated as a ring in velocity space w/o thermal spread!
Ring-beam diffuses in velocity and couples to the plasma giving rise to instability!
Particle interaction only via electromagnetic fields!
Periodic boundary conditions!
Fieldenergy
DistribuFonfuncFon
Velocityspace
ωci*t
Phasespace(x-vx)
Time=0
vz
vx-vzspace
vy
vx
Beam-drivenplasmainFRCisrobustintheregimevb>>vth
MagnitudeofEx
T=0
T=0
PICCode
Beam
velocity
T=70
Lineardispersion
Lowerhybridfrequency
Modecoupling
Amplitude
Fieldenergy
t*ωci
LowerhybridwaveinteracFonwith
4thBernsteinharmonics
ωLH/ωcii=3.57
Beam-drivenplasmainstabilityinFRCenhances
fusionreacFvityby100ormore
q  TAE FRC observes 100-1000 fusion reactivity enhancement with beam
over that without beam!
q  Our theory/simulation shows the beam-driven instability enhances
fusion reactivity!
q  Hydrogen beam induces deuteron talk formation!
!
experiment
theory(ωpe/ωce=1)
theory(ωpe/ωce=5)
Courtesy:A.NecasandR.Magee
C-2UExp.
Anomalousneutronburstssynchronous
withthestep-likeruptureofbeam-drivenFRC(C-2U)
Smalldecrease
inr
C-2U data
15keVbeam
parFcleacceleraFon
C-2Usignalof22.5keV
C-2U data
ßBurstneutronyield
Largechange
inneutronsignal
ß-Baselineanomalous
neutronyield
Courtesy: R. Magee
Needsbeam-driven
instabilitytocatalyze
enhancedneutron
bursts
NewphenomenologyinstronglybeamdrivenFRC(C-2U)
Neutronburstscoincidewithstaircasephenomena
Hydrogenbeammode
staircase
Courtesy: R. Magee
2%Dinthebeam
Purehydrogenbeamdestabilizesthebeaminstability(inagreementwithanalysis)
Magne6cburstssynchronizewiththestair-steps
Courtesy:T.Roche
Magnetosonicinstability(ofveryfastbuildup)
synchronouswiththestair-steps
Fingerforma6oninbeamcausesburstsofplasmarupture
vx[m/s]
vx[m/s]
ViolaFonoflocal
pressureequilibrium
Fieldlinerupture
LossofbeamparFcles
x[m]
NeutralparFcleanalyzer
Ø 
Ø 
Ø 
Ø 
BeamionsareacceleratedduetocollecFveeffects
Couldresultinraptureofbeamcomponent–longestfingers
Riseseveralcyclotronperiods
Rapture–radiallyextendedasbeamparFcles
Volts
vz[m/s]
Time[ms]
2.07e6m/s
Aneutronicfuelplasmap-B11:
beam-drivenplasmainstability(p:beam,B11:plasma)
Modes
vA
k
De
(Courtesy:S.NicksandA.Necas)
Coupling
Re(!)/⌦cB
vb
Beam-drivenplasmagrowthrate(Theory/PIC):p-B11
k
De
(Courtesy:S.NicksandA.Necas)
/⌦cB
Bluedot:mostunstable
modeinPIC
PICsimulaFonofbeam-driveninstabilityinp-B11:
MagnetosonicbranchresonaFngwithionBernsteinmodes
vA
(Courtesy:S.NicksandA.Necas)
Broadspectrumoffrequencies
/⌦cB
vb
The“Highphase-velocityconjecture”:vφ>>vth
me !v
Satura6on: E =
e
me ! p c
E=
e
mD n!cp vb
=
E=
e
Tajima-Dawson[T-D]
Field
vs.
LongitudinalelectricfieldEx
n ⇤ 105 V/m
with n = 3 4
RelaFvisFccoherence*
me !p ca0
E=
e
*T.Tajima,PJAS,(2010)
PICsimulaFonEfieldmagnitudeisequivalent
toT-Dfield
Conclusions
•  Plasmasustainsbeam-drivenwakefieldswithrobustfieldsto
accelerateparFcles---highphasevelocity=thekey
•  Plasmaremainssereneandrobustwhilethisimmense
wakefieldgeneraFon
•  Acceleratedbeamdrivenplasma(FRC)stabilizesgross
instabiliFesandimprovesconfinement
•  Beam-drivenFRCcanenhancesfusionreacFvity
•  FRCobservesmini-burstsinbeam-drivenFRCthatmaybe
relatedtheabovebeam-plasmainstability,withtheplasma
sFllremainsrobust
•  Whenthephasevelocityishigh,suchawavebecomes
robust,whilesFllkeepingthebulkplasmarobustlyintact
Extraslides
Analogousphenomenoninastrophysics:
accreFondiskepisodicdisrupFon
cf:FRCmini-burstepisodesinTAEFRC
70thBirthday
)
2
s
6
Blazar:AO0235+164
M~108MSun
4
2
0
0
80
Week
40
120
160
Flux(x10 6 )
[photons cm 2 s
1
]
40
Blazar:3C454.3
M~109MSun
30
20
10
0
0
100
Week
200
300
AbazajianandCanac
7
8
Flux(x10
[photons cm
1
]
Blazarshowsan6-correla6on
betweenγburstfluxandspectralindex
A.MizutaandT.Ebisuzaki
RelaFvisFcMHDsimulaFon:episodicrecurrenceof
burstsinaccreFondisk
byA.Mizuta