Optimization and active stabilization of a far-infrared laser for NSTX-U high poloidal wavenumber scattering diagnostics

Xu, Xinhang; Dannenberg, Jon; Domier, Calvin; Zhu, Yilun; Li, Xiaoliang; Luhmann, Jr., Neville; Ren, Yang

doi:10.1063/5.0291363

Optimization and active stabilization of a far-infrared laser for NSTX-U high poloidal wavenumber scattering diagnostics

Journal Article · Mon Dec 29 00:00:00 EST 2025 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/5.0291363· OSTI ID:3013060

^[1]; ^[1]; ^[1]; ^[1]; ^[1]; ^[1]; ^[2]

Univ. of California, Davis, CA (United States)
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

The far-infrared (FIR) laser output beam power and profile are important parameters in the laser-aided diagnostics, directly influencing the spatial resolution and signal-to-noise ratio of measurements. Here, this work focuses on developing a systematic control method to enhance FIR laser beam quality through optimized mirror alignment and real-time feedback-based precision cavity length tuning. A 150 W CO₂ laser, aligned with the waveguide axis using a HeNe reference laser, serves as the pump source. The sensitivity of FIR beam intensity to pump gas pressure and thermal expansion is investigated, revealing that even a 1 µm cavity expansion can significantly degrade output power stability to about two-thirds of its original value. To address this, a feedback control module has been designed and implemented for active cavity length adjustment, stabilizing the output power at ∼30 mW. In addition, maintaining a high formic acid gas pressure ($>$190 mTorr) within the cavity ensures reliable operation. The optimized FIR laser will be deployed on the National Spherical Torus eXperiment-U high poloidal wavenumber scattering system for studying electron-scale turbulence in tokamak plasmas.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: FG02-99ER54518; SC0021353

OSTI ID:: 3013060

Journal Information:: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 12 Vol. 96; ISSN 1089-7623; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

References (31)

Optically pumped far infrared lasers Jacobsson, Stellan Infrared Physics, Vol. 29, Issue 5 https://doi.org/10.1016/0020-0891(89)90035-3	journal	July 1989
Quasi-optical electron cyclotron emission imaging diagnostic advancements on the J-TEXT tokamak Xie, X. L.; Zhou, J.; Zhu, Y. Fusion Engineering and Design, Vol. 155 https://doi.org/10.1016/j.fusengdes.2020.111636	journal	June 2020
Design and characterization of a single-channel microwave interferometer for the Helicon Physics Prototype eXperiment Li, X. L.; Liu, Y.; Xu, G. S. Fusion Engineering and Design, Vol. 172 https://doi.org/10.1016/j.fusengdes.2021.112914	journal	November 2021
High level of integration of front-end imaging optics system for electron cyclotron emission imaging diagnostics on the DIII-D tokamak Li, X. L.; Zhu, Y. L.; Yu, G. Y. Fusion Engineering and Design, Vol. 172 https://doi.org/10.1016/j.fusengdes.2021.112915	journal	November 2021
Quasi-optical beam tracing module development for millimeter-wave high-wavenumber collective scattering on the NSTX-U and EAST tokamaks Liu, Xianzi; Ren, Yang; Zhu, Yilun Fusion Engineering and Design, Vol. 212 https://doi.org/10.1016/j.fusengdes.2025.114826	journal	March 2025
Modelling of the electron cyclotron emission burst from a laboratory tokamak plasma with loss-cone maser instability Yu, Guanying; Kramer, Gerrit; Zhu, Yilun Journal of Plasma Physics, Vol. 90, Issue 6 https://doi.org/10.1017/s0022377824001430	journal	November 2024
Microwave scattering system design for ρe scale turbulence measurements on NSTX Smith, D. R.; Mazzucato, E.; Munsat, T. Review of Scientific Instruments, Vol. 75, Issue 10 https://doi.org/10.1063/1.1788851	journal	October 2004
New plasma measurements with a multichannel millimeter-wave fluctuation diagnostic system in the DIII-D tokamak (invited) Hillesheim, J. C.; Peebles, W. A.; Rhodes, T. L. Review of Scientific Instruments, Vol. 81, Issue 10 https://doi.org/10.1063/1.3466900	journal	October 2010
A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak Xiong, C. Y.; Chen, J.; Li, Q. Review of Scientific Instruments, Vol. 85, Issue 12 https://doi.org/10.1063/1.4902564	journal	December 2014
The high- k poloidal scattering system for NSTX-U Barchfeld, R.; Domier, C. W.; Ren, Y. Review of Scientific Instruments, Vol. 89, Issue 10 https://doi.org/10.1063/1.5035410	journal	October 2018
Millimeter-wave system-on-chip advancement for fusion plasma diagnostics Yu, J. -H.; Chang, Y. -T.; Lin, K. -Y. Review of Scientific Instruments, Vol. 89, Issue 10 https://doi.org/10.1063/1.5035559	journal	October 2018
Electron temperature gradient driven turbulence Jenko, F.; Dorland, W.; Kotschenreuther, M. Physics of Plasmas, Vol. 7, Issue 5 https://doi.org/10.1063/1.874014	journal	May 2000
W-band system-on-chip electron cyclotron emission imaging system on DIII-D Zhu, Y.; Yu, J. -H.; Yu, G. Review of Scientific Instruments, Vol. 91, Issue 9 https://doi.org/10.1063/5.0018082	journal	September 2020
System-on-chip upgrade of millimeter-wave imaging diagnostics for fusion plasma Zhu, Y.; Yu, J. -H.; Yu, G. Review of Scientific Instruments, Vol. 92, Issue 5 https://doi.org/10.1063/5.0040449	journal	May 2021
System-on-chip approach microwave imaging reflectometer on DIII-D tokamak Zhu, Y.; Chen, Y.; Yu, J. -H. Review of Scientific Instruments, Vol. 93, Issue 11 https://doi.org/10.1063/5.0099170	journal	November 2022
Development of ultra-short pulse reflectometry on the Experimental Advanced Superconducting Tokamak (EAST) Li, Xiaoliang; Chen, Ran; Xu, Guosheng Review of Scientific Instruments, Vol. 95, Issue 7 https://doi.org/10.1063/5.0215730	journal	July 2024
Millimeter-wave high-wavenumber scattering diagnostic developments on EAST and NSTX-U Sun, Pengjun; Liu, Xianzi; Ren, Yang Review of Scientific Instruments, Vol. 95, Issue 8 https://doi.org/10.1063/5.0219393	journal	August 2024
Frontier system-on-chip (SoC) technology for microwave diagnostics (invited) Chen, Ying; Chen, Pin-Jung; Hu, Robert Review of Scientific Instruments, Vol. 95, Issue 9 https://doi.org/10.1063/5.0219545	journal	September 2024
Exploration of spherical torus physics in the NSTX device Ono, M.; Kaye, S. M.; Peng, Y. -K. M. Nuclear Fusion, Vol. 40, Issue 3Y https://doi.org/10.1088/0029-5515/40/3y/316	journal	March 2000
Confinement and local transport in the National Spherical Torus Experiment (NSTX) Kaye, S. M.; Levinton, F. M.; Stutman, D. Nuclear Fusion, Vol. 47, Issue 7 https://doi.org/10.1088/0029-5515/47/7/001	journal	June 2007
Prospects for pilot plants based on the tokamak, spherical tokamak and stellarator Menard, J. E.; Bromberg, L.; Brown, T. Nuclear Fusion, Vol. 51, Issue 10 https://doi.org/10.1088/0029-5515/51/10/103014	journal	August 2011
Collisionality and safety factor scalings of H-mode energy transport in the MAST spherical tokamak Valovič, M.; Akers, R.; de Bock, M. Nuclear Fusion, Vol. 51, Issue 7 https://doi.org/10.1088/0029-5515/51/7/073045	journal	June 2011
Noise suppression for MHD characterization with electron cyclotron emission imaging 1D technique Yu, G.; Kramer, G. J.; Zhu, Y. Plasma Physics and Controlled Fusion, Vol. 63, Issue 5 https://doi.org/10.1088/1361-6587/abe9f2	journal	March 2021
ECEI characterization of pedestal fluctuations in quiescent H-mode plasmas in DIII-D Yu, Guanying; Nazikian, Raffi; Zhu, Yilun Plasma Physics and Controlled Fusion, Vol. 64, Issue 9 https://doi.org/10.1088/1361-6587/ac7ee7	journal	August 2022
Development and preliminary results of 270 GHz microwave forward scattering diagnostic system on the experimental advanced superconducting tokamak (EAST) Sun, Pengjun; Li, Xiaoliang; Ren, Yang Plasma Physics and Controlled Fusion, Vol. 67, Issue 8 https://doi.org/10.1088/1361-6587/adfa41	journal	August 2025
Recent progress in understanding electron thermal transport in NSTX Ren, Y.; Belova, E.; Gorelenkov, N. Nuclear Fusion, Vol. 57, Issue 7 https://doi.org/10.1088/1741-4326/aa4fba	journal	March 2017
On the role of ion temperature gradient turbulence in driving ion thermal transport in neutral beam injection-heated L-mode plasmas in a superconducting tokamak Sun, P. J.; Ren, Y.; Wang, W. X. Nuclear Fusion, Vol. 65, Issue 8 https://doi.org/10.1088/1741-4326/ade8fc	journal	July 2025
A poloidal high-k scattering system for NSTX-U Domier, C. W.; Dannenberg, J.; Zhu, Y. Journal of Instrumentation, Vol. 17, Issue 01 https://doi.org/10.1088/1748-0221/17/01/C01018	journal	January 2022
Ultrashort Pulse Reflectometry (USPR) diagnostic for EAST Domier, C. W.; Zhu, Y.; Pereira, R. J. Journal of Instrumentation, Vol. 17, Issue 02 https://doi.org/10.1088/1748-0221/17/02/c02010	journal	February 2022
GaN-based W-band receiver chip development for fusion plasma diagnostics Li, Xiaoliang; Chen, Pin-Jung; Chen, Ying Journal of Instrumentation, Vol. 19, Issue 06 https://doi.org/10.1088/1748-0221/19/06/P06046	journal	June 2024
Electron Temperature Gradient Turbulence Dorland, W.; Jenko, F.; Kotschenreuther, M. Physical Review Letters, Vol. 85, Issue 26 https://doi.org/10.1103/physrevlett.85.5579	journal	December 2000

Similar Records

New stabilization system for optically pumped CW far infrared lasers

Journal Article · Sun May 01 00:00:00 EDT 1983 · Int. J. Infrared Millimeter Waves; (United States) · OSTI ID:6418421

Analysis and design of optically pumped far infrared oscillators and amplifiers. Final report, 15 April 1974--15 April 1978

Technical Report · Fri Apr 14 23:00:00 EST 1978 · OSTI ID:6484104

Development of a far-infrared ring laser for plasma diagnostic applications

Journal Article · Thu Oct 01 00:00:00 EDT 1992 · Review of Scientific Instruments; (United States) · OSTI ID:7015991

Optimization and active stabilization of a far-infrared laser for NSTX-U high poloidal wavenumber scattering diagnostics

Citation Formats

References (31)

Similar Records

Related Subjects