Observation of Super-thermal Plasma & Beam Energization in a Beam Driven FRC

Summary
Instrument Characteristics
Absolute Calibration
Observation of Super-thermal Plasma & Beam Energization in a Beam Driven FRC
Introduction
R. Clary1, R. Magee1, A. Roquemore2, A. Kolmogorov3, J. Douglass1, A. Ivanov3, S. Korepanov1, S. Medley2, A. Smirnov1, M. Tiunov3, the TAE Team
1)TRI ALPHA ENERGY, INC., P.O. Box 7010 Rancho Santa Margarita, CA 92688-7010, USA 2)PRINCETON PLASMA PHYSICS LABORATORY, P.O. Box 451, Princeton, NJ 08540, USA 3)BUDKER INSTITUTE OF NUCLEAR PHYSICS, 11 Acad. Lavrentyev Ave., Novosibirsk 630090, Russia
Operating Parameters Calibration
Procedure
Future Work
• C-2U is an advanced beam driven field-reversed configuration (FRC) ex- periment [1]
• Dynamic range (E /E
B ≤ 1 kG (≤ 40 A, no cooling) Filament Grid Ion source bias swept 0 to 45 kV In-house and versatile •••
• Dynamics of fast particles (hydrogen) are critical to plasma (deuterium) performance
• ΔE/E ≲ 0.1
• Operates in current mode
• ∼1 mTorr
• Sweepable beam energy from 3 keV to 60 keV
• Adjustable beam current up to 10 μA at target
• > 95 % of beam current composed of atomic ion species • Beam divergence < 0.5
• Beam size ≤ 3 mm at target
• Absolute response calibration
• Improved energy width measurement
• Improved certainty for lowest channel calibrations
• Neutral particle analyzer [2] simultaneously measures H0 and D0 flux with high energy resolution
• ≈ 1 pA signals
• 2-stage MCP
• 39 channels/isotope (78 total)
Shield
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05
• 2 A filament current • Resulting profiles provide:
• Central channel energy
• Channel energy width
• Repeat varying magnet current • Repeat for Deuterium
• Measurements reveal:
• super-thermal deuteron population in the deuteron plasma
• fast ion (proton) distribution above the beam injection energy
• Integrated work, see Necas (CP10.068) & Magee (CP10.067)
• Small, high purity, ion beam system will be used to calibrate the absolute
response of this device.
Stripping Cell
DAQ (not visible)
Energy Width
Hydrogen Deuterium Classical Limit
0.15
Magnet Current Dependence
d
e
Power Supply & Control Rack
Hydrogen 0.12 Deuterium
Fits
0.09 0.06 0.03
0.000 5 10152025303540 Channel
Motivation • 49 cm impact radius view (outside separatrix)
Installation on C-2W
• Simultaneous H & D NBI • • 1 to 20+ keV energy range to capture multiple distribution effects • • Broad spatial distribution of fast ions
• Highly kinetic anisotropic fast ion orbits
H
12 8 4
• Improved spatial range
• Take advantage of diagnostic & heating NB as cx targets
• Neutron flux measurements suggest enhanced fusion rates •
• 100% D2 pre-filled confinement chamber Plasma shots
• 100% H2 NBI • 100% D2 FRC
NBI
rΔφ Neutrons 0 > 10 keV D
Hydrogen
D 12 8
•
Operating Principles
E, B
4
Fast ion pressure ∼ plasma pressure • Fast ion dynamics < 10 μs time scale
−2 −1 0 1 2 3 4 t (ms)
Simulated Distributions
Beam Final Beam Injection
ionizer cell
x=2qB2 1+πy
Inferred fast ion behavior highlighted in forthcoming paper See Necas (CP10.068) & Magee (CP10.067)
6 42 2
10 10
z
y
2mE Ion Bernstein 14
∼ 30) Detection & Data Acquisition
max min • He gas stripping cell
• E ≤ 40V/cm (≤ 200V) • Mass rejection > 103
• Up to 120 channels
• 1 MS/s 12 bit digitization
• Programmable gain
• Ethernet or touchscreen control • Mounted directly to instrument • ≲ 10 μs rise time
E (kev)
E (keV)
rΔφ (cm)
Arb
Arb
E (keV)
E (keV)
NBI
50 cm
50 cm
ΔE/E
E/B
Configuration
NBI
15 10 5
15 10 5
Into Gas (90% H2, 10% D2)
20
Beam-into-gas test shots
oblique view (same as NBI) • 90% H2, 10% D2 NBI
◦
D Re•sults 40
• Beam-into-gas verifies NPA calibration 30 • Energization of (Proton) fast ions above NBI energy 20 • Energization of (Deuteron) plasma 10
Shot 49398
50 40 30 20 10
H
High energy D0 and neutrons correlate well in time 0 30 25 micro-channel plates 20 Int•erpretation 15
8 6 4 2
8
6
00 5 10 15 20 25 30 Energy (keV)
Plasma Final Plasma Initial
2 4 6 8 10 12 14 Energy (keV)
y=2
π2mE 4d
• Alfvén ion cyclotron
• Simulations show fast-ion energy diffusion
• Simulations show tail in plasma ion distribution
2 101
EPOCH simulations suggest fast-ion coupling with 10 • Buchsbaum 5
10 104 103
0 0
x• 16
Deuterium
qB 84
12 • 10
Measurements on C-2U
NBI
f
[1] M. W. Binderbauer et al. Physics of Plasmas 22.5, 056110 (2015), p. 056110.
[2] S. S. Medley and A.L. Roquemore. Review of Scientific Instruments 75.10 (2004), pp. 3625–3627.
0.000 5 10152025303540 Channel
a. Ionsource
b. Ionextraction
c. Filtermagnet
d. Accelerationgap
e. Electrostaticquadrupolelens
f. Targetchamber
−1 0 1 2 3 4 5 6 t (ms)
5
b
a
c