1. Similarities and differences in SOL physics
between W7-AS and LHD (selection)

2. SOL topology W7-AS (ID) LHD (HD)
• Open divertors: weak neutral compression, low pumping efficiency
• Flexible in operational configuration
- W7-AS: edge position control, variation of island size and pitch angle,
but islands sensitive to perturbations
- LHD (HD): edge position control, insensitive to perturbations, strike-line sweeping,
but significant neutral-wall interaction
• Small internal pitch angle Q = dr/dl  - large Lc
- prominent role of  transport

3. Impact of stochasticity on transport
LHD
Zoomed Lc contour + Poincaré plot
m/n
10/2
10/3
radial
10/4
10/5
10/6
10/7
10/8
HFS
(O-points)
poloidal
• W7-AS and LHD: Large regular Lc patterns contradict
stochastic diffusion of field lines *
Thomson
EMC3-EIRENE
Transport governed by low-order islands
(W7-AS: 5/n, LHD: 10/n)
Temperature profiles can be explained by ordered
// and  transport w/o need of stochasticity
• EMC3-EIRENE reproduces findings in both
W7-AS and LHD

4. No high recycling regime
W7-AS
LHD
EMC3-EIRENE
Langmuir probes
nedpeak/1019m-3
Mloss/pup
nes/1019m-3 1 2 3 4 5 6 7
0.4
0.6
0.8
1-2nedTed/(nesTes) -
• No evidence for high recycling: ned, Isat nes, ne up to rollover (D = const  correct slope)
(correct predictions by 3D code)
• Absence of high recycling due to momentum loss already at low densities from friction
between counter-flows on adjacent island fans
 high nes needed to achieve detachment
• Rollover of ned and recy :
nes  Ted  and Prad  inward shift of ionization zone when Ted < Eion
larger recycling zone momentum loss   recy , ned 

5. Detachment W7-AS LHD • Stable partial detachment found only
with large islands and field-line pitch
• Sharp transition to detachment:
Prad /Pabs  to 90% , Isat 
• Radiation belt found outside LCFS
• EMC3-EIRENE:
- reproduces the above findings
- predicts stable radiation belt outside
LCFS
• Detachment triggered by short massive gas puff
and self-sustained for 2 sec (Serpens mode)
• Sharp transition to detachment: Prad  Isat 
• After transition hot plasma shrinks and
radiation zone moves to inside LCFS
• EMC3-EIRENE:
- carbon Prad /Pabs up to 90%
- solutions found with radiation belt outside LCFS
in stochastic layer (at 10/6 and 10/7 islands)

6. Impurity retention LHD W7-AS • NC-HDH transition: strong gas puff
Increasing ne
nLCFS = 2 x 1019 m-3
4 x 1019 m-3
Increasing ne
nes = 1.5 x 1019 m-3
5.0 x 1019 m-3
• NC-HDH transition: strong gas puff
high nes high Grecy
radiation shifts from core to edge
(imp/E: 50 
• Narrow Fe accumulation window at nLCFS 
3 x 1019 m-3. Fe accumulation stops for higher
densities
• EMC3-EIRENE: reproduces outward shift of impurities for both W7-AS and LHD
High nes - impurity source (Fe) : reduced due to screening of sputtering CX neutrals
- impurity transport: reversed due to friction force > thermal force, retains
impurities at outer SOL region