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Intense Diagnostic Neutral Beam For Burning Plasmas Challenges for ITER and Opportunities for KSTAR Jaeyoung Park Glen Wurden and MFE team Los Alamos National.

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Presentation on theme: "Intense Diagnostic Neutral Beam For Burning Plasmas Challenges for ITER and Opportunities for KSTAR Jaeyoung Park Glen Wurden and MFE team Los Alamos National."— Presentation transcript:

1 Intense Diagnostic Neutral Beam For Burning Plasmas Challenges for ITER and Opportunities for KSTAR Jaeyoung Park Glen Wurden and MFE team Los Alamos National Laboratory US-Korea workshop, Sad Diego, May 19, 2004 Presented at the US ITER Forum, Univ.. of Maryland, May 8, 2003

2 Why IDNB? Upcoming burning plasma experiments (ITER or FIRE) Intense diagnostic neutral beam (IDNB): Critical baseline diagnostics for burning plasma experiments. - CHarge Exchange Recombination Spectroscopy (CHERS): ion temperature profile, impurity and helium ash measurements and fast alpha distribution. - Motional Stark Effect (MSE): current profile (q-profile). Current technology on diagnostic neutral beam: unlikely to work on burning plasmas due to beam penetration, increased background noise -> low S/N. Intense (~ 100 A/cm 2 ) pulsed beam: better S/N. LANL has hardware, history and expertise (since 90s) and personnel for pulsed IDNB source R&D.

3 Existing IDNB Hardware at LANL

4 Conventional DNB in burning plasmas? How well will it work? Burning plasmas: higher electron density and larger plasma dimension --> beam penetration problem Visible background bremsstrahlung: main source of noise and increase with radius and n e 2 (while CHERS signal increase with n e ) Increasing beam intensity: very costly in CW beam. Proposed ITER heating beam: H - based at 500 keV vs. ~125 keV for optimal beam energy for CHERS (need for DNB)

5 Bremsstrahlung vs. CER signal levels for CW beam - Low S/N ratio especially in the core region * Full-sized ITER Calculations by Dan Thomas, 1997 Varenna Workshop From ITER data base: T e ~ keV flat N e ~ 1x10 14 cm -3 Beam energy = 125 keV/AMU Beam current of 40 A (CW) Beam area of 20 cm x 20 cm

6 Pulsed Ion Diode Neutral Beam (IDNB) Since energy is fixed, consider increasing current. Magnetically Insulated Diode (MID) technologies can be used to create intense, pulsed beams at the requisite energy. S/N improved by : –synchronous gating on detection system. –comparable CER and VB signals require smaller dynamic range from detection system. Assumptions:CW beam –beam diameter =.2m x.2m –initial beam intensity = 1.0 x 10 3 A/m 2 Assumptions: pulsed beam –beam diameter =.2m x.2m –initial beam intensity = 1.0 x 10 6 A/m 2 –pulse length= 1  s –gate time = 2  s –pulses per second= 30 (300) Dan Thomas (GA) ran a comparison of CW and Pulsed DNB systems for the original ITER (Varenna 1997 Workshop)

7 Pulsed IDNB yields much larger signals* and could work in the core region * Full-sized ITER Calculations by Dan Thomas, 1997 Varenna Workshop

8 Technical approach Intense ion beam source: Magnetically Insulated Diode (MID) -beam extraction over Child-Langmuir (CL) limit (~ 100 times) Plasma anode: clean beam with long lifetime Repetitive pulse operation: short pulses (1-2  s) with high rep-rate (~ 30 Hz) - improve S/N ratio with low cost. Optimal beam 125 keV/amu for CHERS. Independent from neutral heating beam. Potential show stoppers Beam divergence: 1˚ or less divergence required. Not yet proven with MID with plasma anode at high beam extraction. Lifetime issue: 10,000 shots or more. May not be compatible with high beam extraction (~ 100 times CL limit), high power (~ 4 GW peak power), low beam divergence, etc. Repetition rate: gas handling and cooling requirement. LANL IDNB Proposal

9 Magnetically insulated diode (MID) basic Transverse magnetic fields in A-K gap - provide insulation and charge neutralization Critical magnetic field (B*): required B-field for electron sheath = A-K gap - B* ~ 1.3 kG for 1.5 cm 250 kV. If B >>B* or B < 100A/ cm 2 for D 0 ion. - enhancement factor of ~ 100 was obtained (by Ueda et al. in 1993) for H 0 ion beam. Beam extraction will be done in the cathode opening B Anode Plasma Cathode Ions Electrons Electron sheath

10 IDNB ITER- relevant parameters Critical issue 

11 In relation to ITER Beam divergence, gas handling and repetition rate, lifetime and reliability - all critical issues for IDNB performance KSTAR is a logical choice for IDNB demonstration and deployment Successful operation of IDNB ensures the critical diagnostic capability for ITER Specific to KSTAR High S/N ratio and excellent spatial resolution Diagnostic flexibility (independent of NBI) Low power consumption ( Hz) and small footprint Opportunities for KSTAR

12 IDNB R&D (2-3 years) - LANL lead FY 06 funding requested MID operation and performance optimization - High beam extraction (~ 100 x CL limit) - Low beam divergence (5-10 mrad) - Lifetime (~ 100,000 shots) - Optimize the repetition rate ( Hz) Design tool for MID system - 2D fluid + PIC simulation Deployment and Demonstration (2-3 years) - KSTAR lead Prototype construction and installation - Beam neutralization (gas handling and pumping requirement) specific to KSTAR DNB capability to KSTAR IDNB performance demonstration for ITER Project scope and expected schedule

13 Proposal Title: Intense Diagnostic Neutral Beam For Burning Plasmas Pulsed Ion Source - Magnetically Insulated Diode Proposal Objective: FESAC panel on “A Burning Plasma Program Strategy to Advance Fusion Energy”: 2nd highest priority “ to develop enabling technology that supports the burning plasma research and positions the US to more effectively pursue burning plasma research” The highest priority for US contributions to the ITER project: “baseline diagnostics, plasma control, remote research tools, etc.” Intense diagnostic neutral bea (IDNB): Critical baseline diagnostics for CHERS and MSE - ion temperature profile, impurity and helium ash measurements, fast alpha distribution., and q profile. Intense (~ 50 A/cm 2 ), pulsed beam: better S/N and cost efficient. LANL has hardware, history & expertise (since 90s) and personnel for pulsed IDNB source R&D. Expected Cost and Schedule: Task 1: 24 month effort headed up by LANL - P24 (outside collaboration on modeling) ~$1.2 M/yr Task 2: 24 month effort headed up by LANL - P24 (collaboration with major fusion facility) ~ $1.2M/yr Total: $4.8M over 48 months Deliverables: Task 1&2: Technical reports on bulleted items and a numerical design tool for IDNB MID. Task 2: Prototype intense diagnostic neutral beam for deployment. Contact Information: Proposed Technical Approach: Intense ion beam source: magnetically insulated diode (MID) with anode plasma for clean, intense (~ 50 A/cm 2 ) neutral beam Repetitive pulse operation: short pulses (1-2  s) with high rep- rate (~ 30 Hz) to improve S/N ratio with low cost. Optimal beam energy of 125 keV/amu for CHERS and MSE. Low beam divergence: 1˚ divergence with modified electrodes and additional electric quadrupole beam shaping. Task 1: Characterization and optimization of MID Operation MID facility (CHAMP) at LANL High beam extraction ( times Child-Langmuir limit) Modeling of MID (two-fluid and PIC simulation). Task 2: Deployment of prototype diagnostic beam Parallel beam extraction with electrode modification. Efficient neutralization and high rep-rate Deployment ready at major fusion facility in 4 years Dr. Jaeyoung Park and Dr. Glen Wurden Plasma Physics Group (P-24), MS E-526 Los Alamos National Laboratory, Los Alamos, NM Tel) , ) and


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