powerful rf ion sources for fusion - agenda (indico)€¦ · powerful rf ion sources for fusion...
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Ursel Fantz for the IPP-NNBI Team
IPAB2016, Legnaro (Padova) March 14-15, 2016
Towards 40 A Negative Hydrogen Ion Beams for Up to 1 hour
Powerful RF Ion Sources for Fusion
Max-Planck-Institut für Plasmaphysik
The half size ITER source at the ELISE test facilty
Ursel Fantz, p. 2 IPAB2016: March 14-15, 2016
Neutral Beam Injection (NBI) for ITER
~ 25 m
Beam line
RF ion source and
MAMuG accelerator
neutralizerRIDcalorimeter
gate valve
bellows
~ 25 m
Beam line
RF ion source and
MAMuG accelerator
neutralizerRIDcalorimeter
gate valve
bellows
Diagnostic beam (100% IN)
3 MW 3 s every 20 s, 100 keV Hydrogen
Heating beams (50% EU, 50% JA)
33 MW injected power from 2 injectors 3600 s, 1 MeV Deuterium
15 m beam line based on
negative hydrogen ions
An international project that aims to demonstrate that fusion is an energy source for the future!
Bellows Gate valve
Calorimeter Residual ion dump Neutralizer
RF ion source Accelerator
Ion generation Acceleration Neutralisation Transport
Ursel Fantz, p. 3 IPAB2016: March 14-15, 2016
Ion sources in present NBI systems: Example ASDEX Upgrade
40 cm
Beamline 1 Arc sources: H 85 A, 55 kV, 7.2 MW D 75 A, 65 kV, 10 MW
Beamline 2 RF sources: H 62 A, 72 kV, 5.6 MW D 62 A, 93 kV, 10 MW
Sources for positive ions (> 60% H+) at low pressure ( ~1 Pa) and high power (~100 kW)
Ursel Fantz, p. 4 IPAB2016: March 14-15, 2016
Ion sources – Two concepts
High-current
tungsten filaments
RF
coils
Faraday shield
Inductively driven source
RF power supply ( 100 kW)
RF frequency 1 MHz
Long lifetime
Arc sources RF sources
AUG sources
Hot cathodes (2000 – 3000 K)
DC voltage ( 100 V)
Arc current (1000 A)
Regular maintenance
Ursel Fantz, p. 5 IPAB2016: March 14-15, 2016
Positive or negative hydrogen ions?
Question answered by requirements on beam energy needed for heating and current drive
ITER: 1 MeV (D) for substantial CD
Negative ions
Fragile objects
(binding energy: 0.75 eV)
Co-extracted electrons
Accelerated electrons damage electrodes ! Deflection of electrons by a magnetic field in the 2nd grid, the extraction grid, keeps heat load below tolerable amount.
Low current densities
j(H¯) 0.1 j(Hx+)
ITER: 40 A D¯
for 16.5 MW power
ITER: electrons / ions < 1
Large sources
Ursel Fantz, p. 6 IPAB2016: March 14-15, 2016
How to create negative hydrogen ions?
Volume process
Dissociative attachment
Vibrational excitation
e- + H2 → H2(B,C) + e- → H2(v) + e- + hn
e- + H2(v) → Hˉ + H
hot electrons
cold electrons
High electron density and high pressure
Plasma Generation
„hot“ electrons
Expansion
ChamberMagnetic FilterDriver
2He fast
*
2He fast eH *
2
eHH
eVTe 5 eVTe 1
H
H
e
„cold“
electrons
Plasma Generation
„hot“ electrons
Expansion
ChamberMagnetic FilterDriver
2He fast
*
2He fast eH *
2
eHH
eVTe 5 eVTe 1
H
H
e
„cold“
electrons
Concept of a tandem source
Problems:
High co-extracted electron current
Pressure and thus
Stripping losses in accelerator
Low ion current at low pressure
Hˉ + H2 H + H2 + e
ITER: p 0.3 Pa 30% losses
Ursel Fantz, p. 7 IPAB2016: March 14-15, 2016
How to create sufficient negative hydrogen ions at 0.3 Pa?
Volume process dissociative attachment
e- + H2(v) → Hˉ + H jH- 4 mA/cm2 je/jH- > 30
Surface process
Cs layer low work function
H, Hx+ + surface e- Hˉ Cs evaporation
much higher jH- much lower je/jH-
Destruction: volume processes
Survival length of Hˉ few cm
Electron stripping
Mutual neutralisation
Hˉ + e- H + 2e-
Hˉ + H+ H + H
Hˉ + H H2 + e-
or H + H + e-
Associative detachment
(non-associative)
0
50
100
150
200
250
20 40 60 80 1001201401601800.1
1
10
100Ca
l. c
urr
ent
den
sity [
A/m
2]
0.37 Pa
0.5 Pa
0.85 Pa
1.4 Pa
0.4 Pa
no Cs
H
RF power [kW]
0.4 Pa
1.4 Pa
Ele
ctr
on t
o io
n r
atio
no Cs
0.37 Pa
0.5 Pa
0.85 Pa
RF source (2005)
Ursel Fantz, p. 8 IPAB2016: March 14-15, 2016
The RF ion source concept for negative hydrogen ions
- -
N
S
- -
- -
(magnets turned by 90º)
e
e
Source on high potential Current density measurements
Electrical: je, jion
Calorimeter: jion, beam profile
Co-extracted electrons
Plasma grid: ~ -20 kV pos. bias: ~ 15 V
bias plate
Grounded grid
Extraction grid : ~ -15 kV
Hˉ
Cs oven
water cooled Faraday screen
Al2O3 ceramic
gas feed
Filter field
N
S
Driver Expansion Extraction
H2
e
Hx+
H
Hˉ
RF coil
10 mT
In 2007 chosen as ITER NBI reference source.
Ursel Fantz, p. 9 IPAB2016: March 14-15, 2016
The RF ion source for ITER NBI
Prototype source
Driver
0.52 m
2 m
1 m
8 RF drivers with 4 RF generators of 180 kW power each
1.9
m
RF Driver
Extraction area 0.2 m2
1280 apertures in 16 groups
Iex = 57 A (Dˉ), Iex = 66 A (Hˉ)
jD > 28 mA/cm2, jH- > 32 mA/cm2
je/jD- < 1 (co-extracted electrons)
Stable for 1 hour
Uniform (d<10%)
p ≤ 0.3 Pa
Requirements
Ursel Fantz, p. 10 IPAB2016: March 14-15, 2016
Achievements at test facilities: Status 2011
BAvarian Test MAchine for Negative Ions
BATMAN
Physical parameters
jH- > 30 mA/cm2
jD- > 20 mA/cm2
je/jD- < 1
0.3 Pa
(4 s)
1/8 area of ITER source, 1 driver, body 3259 cm2
* stopped operation in 2011 MANITU*
Multi Ampere Negative Ion Test Unit
Long pulse extraction
3600 s
Dˉ operation
(Hˉ)
at reduced parameters
1/2 area ITER source, 4 drivers body 7680 cm2
RADI* Former RADIal Injector of W7-AS
Size scaling
Scalability
Plasma uniformity
80 cm
okay
Tasks achieved BUT NOT SIMULTANEOUSLY IN ONE LARGE SOURCE
Task of ELISE within the F4E roadmap towards ITER NBI
Ursel Fantz, p. 11 IPAB2016: March 14-15, 2016
The intermediate step: ELISE
8 driver, 800 kW 1.9 x 0.9 m2
Extrapolation to large ITER source within the F4E roadmap towards ITER NBI
Intermediate step: ELISE
Extraction from a Large Ion Source Experiment
1 driver, 100 kW 0.52 x 0.26 m2
IPP prototype source
Heating & Diagnostic beam European NBTF (Italy)
4 driver, 360 kW 1.0 x 0.9 m2
4 x
2 x
ITER reference source since 2007
Neutral Beam Test Facilities
Ursel Fantz, p. 12 IPAB2016: March 14-15, 2016
The ELISE test facility
Parameter and targets
Isotope H-, D-
RF power = 2 x 180 kW in 4 drivers
Aex = 1000 cm2, uniformity > 90%
Iion,acc = 20 A, Ie/Iion < 1 at 0.3 Pa
Utot = 60 kV, Uex < 12 kV
Plasma: 3600 s Beam : 10 s every 120 - 150 s (HV)
1 m
ELISE test facility with a ½-size ITER source
Provide input for design, commissioning and operation
of ITER NBI systems and European test facilities
Demonstrate ITER parameters in large sources
Extracted currents (ions and electrons)
Beam homogeneity
Develop most efficient
source operation scenarios
Gate Valve Ø 1.25m
Main insulator
Ion source
Extraction system
Tank
Cryopumps
Diagnostic calorimeter
Beam
Ursel Fantz, p. 13 IPAB2016: March 14-15, 2016
The ELISE test facility
ELISE test facility with a ½-size ITER source
Provide input for design, commissioning and operation
of ITER NBI systems and European test facilities
Demonstrate ITER parameters in large sources
Extracted currents (ions and electrons)
Beam homogeneity
Develop most efficient
source operation scenarios
Parameter and targets
Isotope H-, D-
RF power = 2 x 180 kW in 4 drivers
Aex = 1000 cm2, uniformity > 90%
Iion,acc = 20 A, Ie/Iion < 1 at 0.3 Pa
Utot = 60 kV, Uex < 12 kV
Plasma: 3600 s Beam : 10 s every 120 - 150 s (HV)
Source opening after 2 years of experimental phase
Ursel Fantz, p. 14 IPAB2016: March 14-15, 2016
0
50
100
150
200
250
300
350
10 20 30 40 50 60 70 800 900.1
1
10
j ion
,ex [A
/m2]
ITER req.
ITER req.
electrons
ions
Ele
ctr
on / ion r
atio
RF power per driver [kW]
ELISE 3.8 mT BATMAN
Deuterium, 0.3 Pa
0
50
100
150
200
250
300
350
10 20 30 40 50 60 70 800 900.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
ions
j ion
,ex [A
/m2]
ITER req.
electrons
ITER
req.
BATMANELISE 2.2 mT
Ele
ctr
on / ion r
atio
Hydrogen, 0.3 Pa
RF power per driver [kW]
ELISE test facility – Short pulse operation
Size scaling: ELISE source performance compared to prototype source at BATMAN
20 s plasma, 10 s beam
Similar dependencies Lower Cs consumption than expected
Less magnetic filter field needed 80 kW/driver should be sufficient
Ursel Fantz, p. 15 IPAB2016: March 14-15, 2016
ELISE test facility – Towards long pulses
0 100 200 3000
50
100
150
200
jion
jionjion
je
jeje
Extr
acte
d c
urr
ent density [
A/m
2]
Time [s]
40 kW
30 kW
40 kW
30 kW
0.0
0.7
1.4
2.1
2.8 Hydrogen at 0.35 Pa
40 kW/driver
30 kW/driver
Cs e
mis
sio
n [a.u
.]
0 50 100 150 2000
20
40
60
80
100
120
jionjion
je
je
Extr
acte
d c
urr
ent density [
A/m
2]
Time [s]
0.0
0.2
0.4
0.6 Deuterium at 0.30 Pa
20 kW/driver
Cs e
mis
sio
n [a.u
.]
Stable ion currents (within 5%) but high dynamics of co-extracted electrons
Co-extracted electrons limit source performance, in particular in deuterium !
je/jion < 1 je/jion > 1
Cs release by back-streaming ions
Ursel Fantz, p. 16 IPAB2016: March 14-15, 2016
ELISE test facility – Towards long pulses
Record-setting one hour pulse at 0.3 Pa in hydrogen
Best 3600 s pulse up to now
ion = 9.3 A, je/jion < 0.4
(20 kW/driver)
1500 1600 1700 1800 1900 2000 21000
2
4
6
8
10
Time [s]
Ie,bottom
Ie,top
Curr
ent [A
]Iion
0 600 1200 1800 2400 3000 36000
20
40
60
80
100
je/jion
je
Extr
. curr
ent density [A
/m2]
Time [s]
jion
0.0
0.4
0.8
1.2
1.6
2.0
Ele
ctro
n / io
n ra
tio
H¯ beam on the calorimeter
Ursel Fantz, p. 17 IPAB2016: March 14-15, 2016
ELISE test facility – Beam diagnostics
Grid system
Advanced beam diagnostics
To determine beam divergence and beam homogeneity
Diagnostic calorimeter with thermocouples,
water calorimetry and IR data analysis
Beam Emission Spectroscopy (BES with 20 LoS)
Tungsten wire calorimeter
Grounded grid
Ursel Fantz, p. 18 IPAB2016: March 14-15, 2016
ELISE test facility – Beam diagnostics
5 10 15 20 25
0
2
4
6
8
Div
erg
en
ce / (
°)
Normalized Perveance / (%)
LOS #18
Beam Emission Spectroscopy
Advanced beam diagnostics
To determine beam divergence and beam homogeneity
Diagnostic calorimeter with thermocouples,
water calorimetry and IR data analysis
Beam Emission Spectroscopy (BES with 20 LoS)
Tungsten wire calorimeter
In perveance optimum: divergence between 1° and 2° and homogeneity better than 90 %
Grid system
Ursel Fantz, p. 19 IPAB2016: March 14-15, 2016
Towards 20 A Negative Hydrogen Ion Beams for Up to 1 hour
Achievements of the ELISE Test Facility
Experience in operation of large RF beam sources
2½ years of successful operation
Inspection and maintenance
Similar dependencies as in prototype source
Less Cs consumption as expected
Lower magnetic filter field needed
80 kW/ driver should be sufficient
Beam homogeneity better than 90%
SPIDER, 2017+ ELISE, 2012+ MITICA, 2021+
NBTF in Padua, Italy
Important step within the European roadmap for ITER NBI
ITER NBI
Iion,ex Pulse Power/driver
25.5 A 20 s 52 kW
18.3 A 400 s 45 kW
9.3 A 1 h 20 kW
Hydrogen, 0.3 Pa, e/ion < 1
Co-extracted electrons limit source performance, in particular in deuterium !