Performance of Upgraded JET Neutr Beam Injectors D

Performance of Upgraded JET Neutr Beam Injectors D et and al. DĆirić th SOFT, Porto, Portugal, 27 -09 -201 1/18 2627 -Sep-2010 JET NBI Team 26 th SOFT, Porto, Portugal,

EP 2 Neutral Beam Enhanceme q Neutral Beam Enhancement (NBE) project - launched in spring 2005 as part of JET Enhanced Performance 2 (EP 2) programme. q One of the biggest modifications of the JET machine within the EFDA framework– carried out by EURATOM/CCFE Fusion Association. q Main aims: a) increase of injected neutral beam power ; b) increase of beam pulse duration. q Original plan : completion by the end of 2009. q Present plan : start integrated commissioningearly in 2011. q The initial testof the performance of the upgraded injectors carried out during JET operation in 2009 by the members of the JET NBI team: D. Ćirić, A. D. Ash, B. Crowley, I. E. Day, S. J. Gee, L. J. Hackett, Homfray, I. Jenkins, T. T. C. Jones, D. Keeling, D. B. King, R. F. King, Kovari, R. Mc. Adams, E. Surrey, D. Young, J. Zacks D Ćirić et al. 2/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010 M. D. A.

JET NBI System 2003 -200 q Two Neutral Injector Boxes q Positive Ion Neutral Injectors NIB 4: 6 × 80 k. V/52 -58 A PINIs 1 × 130 k. V/56 A PINI NIB 8: 8 × 130 k. V/56 A PINIs q Beam Species H 22, D D 22, , T T 22, , 44 He, 33 He He q Maximum injected power (D 2): NIB 4: ~11. 5 MW NIB 8: ~12. 5 MW q 23. 8 MW Maximum beam pulse length (at high power) : 10 s 9. 96 s D Ćirić et al. 3/18 Layout of the JET plasma heating systems. 26 th SOFT, Porto, Portugal, 27 -Sep-2010

EP 2 NBE Goals and Scop (Presented at the 24 th SOFT in Warsaw in 2006) q Design goals: a) To To increase total injected deuterium neutral beam power a) increasethe total injected deuterium neutral beamfrom power from present 24 toto at at least 34 34 MW ; present 24 MW MW least MW. b) To increase the NBI pulse duration at maximum power from present 10 s to 20 s and at half power from 20 s to 40 s; c) To improve overall availability and reliability of the NBI system. q This will be achieved by: a) Conversion ofof allall present JETJET PINIs to 125 k. V/65 A triode PINIs with a) present PINIs to 125 k. V/65 A triode PINIs w modified ion source andand accelerator configuration; modified ion source accelerator configuration. b) Replacement of various inter-pulse cooled components with actively cooled equivalents (new actively cooled duct liners ); c) Replacement of four 160 k. V/60 A HVPS units with four 130 k. V/130 A units. D Ćirić et al. 4/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

EP 2 PINI Commissionin q A number of EP 2 PINIs commissioned at JET NB Test Bed (NBTB) confirmation of increased neutral beam power and higher beam transmission. q Two upgraded EP 2 PINIs installed on Octant 8 NIB in summer 2009 ► conditioned to full power : 2 weeks of operation, ~900 pulses, ~300 s of accumulated beam on time; ► fully characterised (neutralisation efficiency measurements). q The main purposeof the experiment: ► verify the increase in injected power; ► confirm power loading on beamline components. q EP 2 PINIs routinely operated during JET campaign in autumn 2009. Table 1. Designed and achieved deuterium beam parameters. D Ćirić et al. Parameter Designed value Maximum voltage (k. V) Maximum current (A) Maximum power (MW) Maximum pulse length (s) 125 65 >2. 13 20 5/18 Achieved value On-line Off-line 112 125 54 65. 7 2. 08 2. 16 9. 3 - 26 th SOFT, Porto, Portugal, 27 -Sep-2010

EP 1 EP 2 PINI Power Increase ( EP 1 PINI– developed during EP 1 Octant 8 NIB upgrade 1999 -2003 (130 k. V/56 A triodeacceleratorand supercusp ion source ). q EP 2 PINI power increase is achieved in three steps(illustrated by comparing measured EP 1 and EP 2 PINI parameters in deuterium at 120 k. V). 1. Accelerator modification: Increase extraction aperture diameter: 11 mm 11. 5 mm. Reduce acceleration gap: 16 mm 15 mm. Increase in optimal beam current 48. 1 A 56. 4 A (at 120 k. V) Increase in injected power 1. 37 MW 1. 55 MW D Ćirić et al. 6/18 Injected deuterium power per PINI (MW) q EP 1 EP 2 (1) 2. 0 1. 55 1. 37 1. 19 1. 03 1. 0 0. 5 0. 22 0. 24 0. 13 0. 12 0. 0 E/1 26 th SOFT, Porto, Portugal, 27 -Sep-2010 E/2 E/3 Neutral beam component Total

EP 1 EP 2 PINI Power Increase ( q In the past, all JET ion sources had Supercuspmagnetic configuration: ► Magnetic filter ► High monatomic ion yield LINEAR CUSPS CHEQUERBOARD CUSPS ► Non-uniform plasma q q Chequerboard configuration: rearrangement of four rows of Sm. Co magnets LINEAR CUSPS HOT WIRE CATHODES ADDITIONAL “FILTER” FIELD DUE TO LINEAR CUSP MAGNETS Chequerboard. PINIs: ► Large field free region LINEAR CUSPS ► Higher molecular ion yield ► Uniform plasma D Ćirić et al. 7/18 CHEQUERBOARD CUSPS 26 th SOFT, Porto, Portugal, 27 -Sep-2010

EP 1 EP 2 PINI Power Increase ( 2. Supercusp to chequerboard conversion a) Higher molecular ion fraction higher neutral beam power b) Uniform ion source plasma uniform beam higher transmission 90 88. 5 Ion species fraction (%) 80 Supercusp ion source Chequerboard ion source 73. 0 70 60 50 40 30 22. 0 20 8. 0 10 0 + + D D+ D Ćirić et al. 3. 5 5. 0 D 2+ Ion species 8/18 + D 3+ Injected deuterium power per PINI (MW) 100 EP 1 2. 0 1. 98 1. 85 EP 2(2 b) (2 a) (1) 1. 55 1. 37 1. 19 1. 03 0. 96 0. 72 0. 67 0. 5 0. 22 0. 24 0. 23 0. 21 0. 13 0. 12 0. 0 E/1 26 th SOFT, Porto, Portugal, 27 -Sep-2010 E/2 E/3 Neutral beam component Total

EP 1 EP 2 PINI Power Increase ( 3. Operation at higher current q Injected deuterium power per PINI (MW) q Neutral beams are usually operated at optimum perveance (min. divergence). 8% increase in current above optimum 6% increase in injected power. 2. 11 1. 98 EP 1 2. 0 EP 2(2 b) (3) 1. 5 1. 37 1. 12 1. 03 1. 0 0. 78 0. 72 0. 5 0. 22 0. 13 0. 24 0. 23 0. 0 E/1 D Ćirić et al. 9/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010 E/2 E/3 Neutral beam component Total

0. EP 1 PINI: 120 k. V/48. 1 A 1. 37 MW D(E): D(E/2): D(E/3) 75%: 16% : 9% 1. Accelerator modification 120 k. V/56. 4 A 1. 55 MW D(E): D(E/2): D(E/3) 76%: 16% : 8% 2. Ion source modification 120 k. V/56. 4 A 1. 98 MW D(E): D(E/2): D(E/3) 52%: 36% : 11% 3. Beam current increase 120 k. V/60. 9 A 2. 11 MW D(E): D(E/2): D(E/3) 53%: 37% : 10% D Ćirić et al. 10/18 Injected deuterium power per PINI (MW) EP 1 EP 2 PINI Power Increase ( 2. 0 2. 11 E/3 E/2 1. 98 0. 23 E/1 1. 5 0. 22 1. 55 1. 37 0. 12 0. 13 0. 24 0. 78 0. 72 0. 22 1. 0 0. 5 1. 03 1. 19 1. 03 1. 12 EP 2 (2) EP 2 (3) 0. 0 EP 1 EP 2 (1) Power increase steps 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Injected Power (Deuterium q EP 1 Octant 8 NIB Upgrade (1999 -2003) resulted in a disappointing outcome: design goal of ~1. 85 MW (per PINI) missed by ~0. 5 MW. q Heatingof the neutraliser gas neutralisation targetline density reduction power deficit. q Gas heating effect taken into account during EP 2 PINI design more accurate power prediction. q Design goal of >2. 13 MW per PINI achievedby increasing beam current 8% above optimal (min. divergence) value. q Total maximum power (both NIBs operated in deuterium) will be >34 MW. D Ćirić et al. 11/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010 0. 5 MW

Deuterium Power Fraction q Neutral beam power fractions estimated using: ► measured ion source species composition (NBTB data); ► known cross sections for collision processes in the neutraliser; ► measured variation of the neutralisation target with extracted power. D Ćirić et al. 12/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Injected Power (Helium q EP 2 PINIs also commissioned using helium gas during JET operation in 2009. q Increase in power comes only from increase in beam current. q Maximum beam voltage 120 k. V (limited by maximum output current of the bending magnet power supply). q Maximum power per PINI (at 120 k. V/42 A) >1. 5 MW. q Total maximum power(both NIBs operated in helium): ~25 MW D Ćirić et al. 13/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Predicted Power (Hydroge q Prediction of injected hydrogen power: ► measured extracted ion species (NBTB data); ► known cross sections for collision processes in the neutraliser; ► neutraliser target variation with beam power (similar to deuterium). q Maximum beam voltage 90 k. V (limited by the power loading limit of the fractional energy ion dumps - H 2+). q Maximum power per PINI (at 90 k. V/50 A) is ~1 MW, with a dominant (~40%) half energy component of the beam. q Maximum total power (both NIBs operated in hydrogen) is ~16 MW. D Ćirić et al. 14/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Predicted Power (Tritium q Prediction of injected tritium power: ► extracted ion species predicted by ion source modelling; ► known cross sections for collision processes in the neutraliser; ► neutraliser target variation with beam power (similar to deuterium). q Maximum beam voltage 118 k. V (limited by the maximum available current in tritium - 45 A). q Maximum power per PINI (at 118 k. V/45 A) is ~2. 2 MW, with a dominant (>60%) full energy component of the beam. q Maximum total power(both NIBs operated in tritium) is ~35 MW. D Ćirić et al. 15/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Conclusions q Successful initial EP 2 PINI performance test – increase in injected beam power and power loading on beamline components confirmed. q Confidence that the design goal (>34 MW in deuterium) will be achieved (after completion of integrated commissioning in 2011). q Considerable power increase (>50%) expected for other beam species (H 2, T 2, He). Table 2. JET NBI parameters after the completion of EP 2 NBE project Parameter Maximum beam energy (ke. V) Maximum beam current (A) Maximum power per PINI (MW) Maximum power per NIB (MW) Maximum total power (MW) Achieved max. power (MW) D Ćirić et al. 16/18 H 2 90 50 1. 0 8. 0 16. 0 10. 1 Gas species D 2 T 2 125 118 65 45 2. 16 2. 2 17. 6 17. 3 17. 6 34. 6 35. 2 23. 8 10. 9 26 th SOFT, Porto, Portugal, 27 -Sep-2010 4 He 120 42 1. 56 12. 5 25. 0 16. 2

JET NBI Operating Space (D 2 35 MW limit 24 MW limit it l se s 20 pu le 10 sp uls el en gth lim it th g n lim D Ćirić et al. 17/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

New JET NB Duct Line Preparation of the Octant 8 Duct Liner for the installation in October 2010 D Ćirić et al. 18/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010

Power Deposition Profiles 2(D ) D Ćirić et al. 19/18 26 th SOFT, Porto, Portugal, 27 -Sep-2010