Transcript Document 7723309

ITPA Pedestal Group Meeting
October 5-7, Princeton
ITER IO urgent tasks:
2. Conditions for ELM pacing using pellets
● Status of the pellet launchers at JET, AUG, D3D
● Discussion of the work plan
● Joint experiments?
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the launchers:
JET
Designed for
Fuelling: size range 22 – 38 × 1020 D, up to 15 Hz
Pacing: size range 0.7 – 1.2 × 1020 D, up to 60 Hz
JET
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
2
Status of the launchers:
JET
JET
System does not meet requirements,
no hand over to JET operator
“Deep modernisation” of launcher system by PELIN
Next attempt to demonstrate requests are fulfilled
and HFPI can work as expect:
spring 2011 (was planned for 2008)
Experienced and well trained team on site
Available performance falls short for planned
experiments, especially the “pacing” part
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
3
Status of the launchers:
AUG Blower gun
Blower gun in new "optimized" configuration (ø = L = 1 mm, expansion tank)
AUG
Expansion tank
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the launchers:
AUG Blower gun
AUG
Blower gun developed for 2 mm pellets,
up to 143 Hz (good performance up to 100 Hz)
installed at AUG
- Lost experienced system engineer
Blower gun moved to other sector (moveable ECRH mirrors)
and modified for 1 mm pellets
- Lost experienced system engineer
Injector seems to work reasonably, pellet transfer through
guiding tubes seems to cause massive losses
Investigation started (Diploma study)
No experienced team for pellet technology at present
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the launchers:
AUG centrifuge launcher
Centrifuge launcher repaired and operational
AUG
(but to achieve full performance commissioning required)
Launch of 1.4;1.65;1.9 mm pellets up to 60-80 Hz from VHFS
No experienced team for operation
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the launchers:
DIII-D
• Pellet Dropper Removed from V+3 Port
– 1mm 10/ms D2 pellets do not penetrate SOL
• 2 barrels of D3DPI now connected to LFS and V+3
– ~20 Hz 1.8mm pellets now available for LFS ELM triggering
V+3
– V+3 port has fast camera view
– ½ run day may be allocated for pellet ELM interactions
• D3DPI to be modified for smaller pellets and
higher rep rate
– 2010 time frame
ITER like
ITPA Pedestal Group Meeting
– New LFS ITER like pellet
pacing injection line
proposed
October 5 – 7, PPPL
D3DPI
P. T. Lang et al.
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Status of the work plan
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the work plan
Not achieved
HFPI system not capable of delivering required pellet
sequences
Earliest possibility spring 2011
provided HFPI reaches design criteria
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the work plan
Experiments done at JET
Analysis ongoing
Make essentially use of pellet scatter,
need to rely on pellet impact on plasma
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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Status of the work plan
(a) no dedicated efforts
(b) done with large pellets (report last meeting, EPS contributions
Wenninger, Kocsis; further analysis ongoing
(c) “parasitic” with recent experiments
(d) “parasitic” with recent experiments
(e) 3D non-linear MHD simulation of ELMs (G. Huysmans)
“JOREK Synthetic diagnostics” + Benchmarking to experiments
-> R. Wenninger
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
11
Status of the work plan
LFS and VHFS pellet launch at JET:
indication for lower trigger threshold with VHFS launch,
but needs closer investigation
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
12
Status of the work plan
(a) Investigation ongoing, main issue is to monitor pellet quality
(and parameters on the separatrix)
So far no fuelling impact by “pacing size” pellets
(b) Technical not feasible (in “pacing regime”)
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
13
Status of the work plan
Former C-pellet launcher (0.3 – 0.9 mm) in AUG store
No (priority) man power to re-install
K. Gal: study which “reasonable” material could mimic
Be-pellets (Boron, Boron carbide?)
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
14
Status of the work plan
Correct input parameters?
“JOREK”? (after benchmarking)
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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“Joint experiments”
PEP 24:
Minimum pellet size for ELM pacing
Topical Group: ITPA Pedestal TG
Contact Person: P.T. Lang (ASDEX Upgrade), B. Alper (JET), L. Baylor (DIII-D)
Devices: ASDEX Upgrade, DIII-D, JET
1.2 Goal
Primary goal is further substantiation of pellet ELM pacing by demonstrating:
1) Enhancing the spontaneous ELM frequency by a factor of more than 10…
2) …with a corresponding reduction in ELM size (global energy loss and peak
local heat fluxes). Is the statistical ELM size scatter affected?
3) Integration into ITER relevant (baseline and AT) scenarios keeping good
confinement/performance.
Not feasible with the current HFPI system,
this system was designed and built for this mission since
JET was regarded the only suitable machine
(pellet/plasma content ratio, intrinsic ELM frequency)
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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“Joint experiments”
PEP 24:
Minimum pellet size for ELM pacing
A further goal is to find out what are the require parameters to trigger ELMs, e.g.
- pellet penetration depth/trigger location
- influence of injection angle
- compatibility with fuelling
- compatibility with other ELM mitigation techniques
(JET shows no reduced trigger potential in ripple and EFCC discharges when
using large pellets – recent report, Lang – EPS2009)
With the actual status of the “pacing” injection systems
a mapping of the parameter space is not possible
Next steps:
JET: Analysis of recent results with “natural” parameter scatter
AUG: Characterise/optimise blower gun
The production and transfer of mm-size pellets may not be possible
with sufficient reliability to establish enduring pacing,
this is a problem for current machines, not necessarily for ITER
ITPA Pedestal Group Meeting
October 5 – 7, PPPL
P. T. Lang et al.
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