external user perspective burning plasmas s j rose ... · 500Å naf/fe. sampled bathed in radiation...
TRANSCRIPT
Overview
Potential for experimental measurement of microphysics processes in a burning plasma
• Kinetic processes
• Survival of bound electronic structure - spectroscopy
Applications of the output from a burning plasma
• Photoionised plasmas
Potential for experimental measurement of microphysics processes in a burning plasma
Kinetic processes
Many aspects of the microphysics of burning plasmas have not been tested experimentally
α
n
radiationInelastic collisions
Inelastic collisions
Inelastic collisionsem+nuclear
nuclear reactions
bremmsstrahlung/scattering
thermalnon-thermal
free electrons
DT ions
Inelastic collisions
Inelastic collisions
Many aspects of the microphysics of burning plasmas have not been tested experimentally
α
n
radiationInelastic collisions
Inelastic collisions
Inelastic collisionsem+nuclear
nuclear reactions
bremmsstrahlung/scattering
thermalnon-thermal
free electrons
DT ions
Inelastic collisions
Inelastic collisions
For Te < 32keV
Many aspects of the microphysics of burning plasmas have not been tested experimentally
α
n
radiationInelastic collisions
Inelastic collisions
Inelastic collisionsem+nuclear
nuclear reactions
bremmsstrahlung/scattering
thermalnon-thermal
free electrons
DT ions
Inelastic collisions
Inelastic collisions
For Te > 32keV
Heating of 2keV, 300gcm-3 plasma (D,T and electrons) with 3.6MeV alpha particles
n α = 0.125nD
α heats electrons
α heats ions
Sherlock and Rose, HEDP (2008)
α
n
radiationInelastic collisions
Inelastic collisions
Inelastic collisionsem+nuclear
nuclear reactions
bremmsstrahlung/scattering
thermalnon-thermal
free electrons
DT ions
Inelastic collisions
Inelastic collisions
Possibility exists of driving non-thermal aspect to fusion
Brueckner and Brysk, J Plasma Phys (1973)Brueckner, Brysk and Janda J Plasma Phys (1974)
Potential for experimental measurement of microphysics processes in a burning plasma
Survival of bound electronic structure - spectroscopy
Introduction of bound electrons perturbs kinetics and allows spectroscopic diagnostic possibilities
α
n
radiationInelastic collisions
Inelastic collisions
Inelastic collisionsem+nuclear
nuclear reactions
bremmsstrahlung/scattering
thermalnon-thermal
free electrons
DT, X ions
Inelastic collisions
Inelastic collisions
bound electrons
ion collisional excitation photoexcitation / potoionisation
ion collisional excitation
Radiation intensity for DT,25keV, 500gcm-3, ρr=2.5gcm-2
1 10 100 10001021
1022
1023
1024
1025in
tens
ity (e
rg/c
m2 /s
/keV
/ste
r)
photon energy (keV)
Compton scattering not included Compton scattering included
High-Z-doped DT implosion
• High-Z dopant (Kr) needed to retain bound electrons at high Te
• High density gives a large depression of the continuum (only Kr n=1 and 2 survive).
• High temperature leads to non-LTE populations.
• Populations come into a steady-state in 100fsec.
Time-dependence of ionisation of Kr in DTTe=25keV, ρ=500gcm-3
1 10 10010-2
10-1
100
101
LTE non-LTE
n=1
n=2
n=1
shel
l pop
ulat
ion
time (fsec)
Distribution of ionisation of Kr in D0.49995T0.49995Kr0.0001Te=25keV, ρ=500gcm-3, ρr=2.5gcm-2
33 34 35 360.0
0.1
0.2
0.3
0.4
0.5
Li-like He-like H-like fullystripped
no escape factor, no radiation field escape factor, no scattering, no radiation field escape factor, scattering, no radiation field no escape factor, Comptonised bremsstrahlung field
popu
latio
n fra
ctio
n
ionisation stage
Emission from D0.49995T0.49995Kr0.0001Te=25keV, ρ=500gcm-3, ρr=2.5gcm-2
1 10 100 10001021
1022
1023
1024
1025
no line contribution line contribution total
inte
nsity
(erg
/cm
2 /s/k
eV/s
t)
photon energy (keV)
Accretion-powered objects
Photoionised plasmas (radiation-dominated plasmas) scale with the ionisation parameter ξ=4πF/ne
Tarter, Tucker and Salpeter, ApJ, 156, 943,(1969)Tarter and Salpeter, ApJ, 156, 953 (1969)
EXO 0748-676
Low mass X-ray binary
ξ=30 ergcms-1
NGC 4593
Seyfert galaxy
ξ=300 ergcms-1
Photoionised plasma experiments have only reached ξ=20ergcms-1
Foord, Heeter, van Hoof, Thoe, Bailey, Cuneo, Chung, Liedahl, Fournier, Chandler, Jonauskas, Kisielius, Mix, Ramsbottom, Springer, Keenan, Rose and Goldstein, Phys Rev Letts, (2004)
collapsed Z-pinchpinhole camera
flux and spectral measurements
absorptionspectrum
emissionspectrum
1000Å CH
500Å NaF/Fe
sampled bathed in radiation frompinch over 4πα steradians
13 14 15 16 17 18 190.0
0.2
0.4
0.6
0.8
1.0
fract
ion
Z*
experiment NIMP with radiation field CLOUDY with radiation field NIMP without radiation field
Much higher ξ values could be obtained by using radiation output from a burning capsule on NIF, allowing access to most extreme astrophysical photoionised plasma conditions.
Photoionised experiments using radiation output from NIF capsule
Much higher ξ values could be obtained by using radiation output from a burning capsule on NIF, allowing access to most extreme astrophysical photoionised plasma conditions.(see: Fujioka et al, arXiv:0909.0315v1)
Conclusions
• Operation of the NIF target depends critically on microphysics of burn (connected to the transport properties). No experiments to measure kinetics in the burning phase, although some experiments have measured rates in cooler phase.
• Kinetic modelling of ion distributions shows no effect from fast alphas. However other studies show 10-20% effect which include large-angle scattering, nuclear interactions and neutron scattering kinetically. Possibility of measuring non-thermal aspect to burn?
• High-Z spectroscopy of doped plasma may be able to diagnose conditions through usual spectroscopic techniques.
• High photon output could be used to drive photoionised plasma experiment with ξ~100 ergcms-1.