Finished PhD, now a postdoc at MIT

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Andrew Seltzman
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Finished PhD, now a postdoc at MIT

Post by Andrew Seltzman » Mon Nov 19, 2018 12:53 am

For those of you who don't follow me on facebook, I finished my PhD in plasma physics last year where I demonstrated the first observation of RF heating in the reversed field pinch:
My thesis:
http://plasma.physics.wisc.edu/uploaded ... 2_2017.pdf
A power point of a conference talk on EBW heating in the RFP:
http://plasma.physics.wisc.edu/uploaded ... an1218.pdf

I have been working as a postdoc at MIT in the plasma science and fusion center since the spring, designing a high field side lower hybrid current drive launcher system for tokamaks, a method that should improve non-inductive current drive efficiency, and allow current profile control nearer to the core. I'm mainly working on the RF design for the launcher system that will be installed on DIII-D in the spring of 2020. I am currently living in Cambridge, MA, but will likely mode to San Diego, CA in about a year to install the system.

Here's me inside DIII-D inspecting the tokamak.
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Andrew Seltzman
www.rtftechnologies.org

John Futter
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Re: Finished PhD, now a postdoc at MIT

Post by John Futter » Mon Nov 19, 2018 2:48 am

Well done Andrew

hope the future brings many neuts

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Re: Finished PhD, now a postdoc at MIT

Post by Harald_Consul » Mon Nov 19, 2018 7:35 pm

Congratulations to your PhD! Maybe I am trying to read your thesis, if it is not mathemtically too sophisticated for me. I am only an applied statictician.

A little joke regarding your photo: I really didn't know, that physicists are willing to do so much arduous research work only to wear such advantageous suit. (I hope find it funny, too.)

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Rich Feldman
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Re: Finished PhD, now a postdoc at MIT

Post by Rich Feldman » Mon Nov 19, 2018 8:17 pm

Congratulations, Andrew.
Not only a PhD, but you have a job! In your field!
Good luck.
-Rich
All models are wrong; some models are useful. -- George Box

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Richard Hull
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Re: Finished PhD, now a postdoc at MIT

Post by Richard Hull » Tue Nov 20, 2018 12:08 am

Really glad to hear you now have your doctorate. Your work should prove rewarding to you personally and financially.
All the very best in your endeavors.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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ReneeDegutis
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Re: Finished PhD, now a postdoc at MIT

Post by ReneeDegutis » Fri Nov 30, 2018 11:44 am

Andrew Seltzman wrote:
Mon Nov 19, 2018 12:53 am
For those of you who don't follow me on facebook, I finished my PhD in plasma physics last year where I demonstrated the first observation of RF heating in the reversed field pinch:
My thesis:
http://plasma.physics.wisc.edu/uploadedfiles/theses/thesisSeltzman132_2017.pdf
A power point of a conference talk on EBW heating in the RFP:
http://plasma.physics.wisc.edu/uploaded ... an1218.pdf

I have been working as a postdoc at MIT in the plasma science and fusion center since the spring, designing a high field side lower hybrid current drive launcher system for tokamaks, a method that should improve non-inductive current drive efficiency, and allow current profile control nearer to the core. I'm mainly working on the RF design for the launcher system that will be installed on DIII-D in the spring of 2020. I am currently living in Cambridge, MA, but will likely mode to San Diego, CA in about a year to install the system.

Dear Andrew,

Congratulations on your achievements! I'm interested in reading the thesis. Good luck with your further professional growth.

Best regards,
Renee Degutis

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Richard Hull
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Re: Finished PhD, now a postdoc at MIT

Post by Richard Hull » Fri Nov 30, 2018 4:56 pm

Please do not re-Quote any text from any previous post in any single, flowing, thread. People here are smart enough to have read the preceding postings in any single thread. We do not do it in these forums to keep the useless re-quoting of already presented text in any single thread to an absolute zero level.

This includes all single thread postings no matter how old or last commented on.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Dennis P Brown
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Re: Finished PhD, now a postdoc at MIT

Post by Dennis P Brown » Tue Dec 04, 2018 11:59 pm

Fantastic work and like others here, congratulations Mr. Seltzman, Ph.D.! I know a bit of just how hard and difficult that path must have been! Guess it's on to General Atomics(?) Best of luck no matter. I know how limited funding has become and the challenges in that field. So, all the best in your career and future!

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Re: Finished PhD, now a postdoc at MIT

Post by Bruce Meagher » Wed Dec 05, 2018 6:21 am

Congratulations Dr. Seltzman! If you come to San Diego contact me if you’re interested in joining several of us fusor members for one of our meetups.

Andrew Seltzman
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Re: Finished PhD, now a postdoc at MIT

Post by Andrew Seltzman » Tue May 19, 2020 1:55 pm

James395 wrote:
Tue May 19, 2020 11:14 am
When you feel that you are stuck with your dissertation abstract and the long hours in front of your monitor do not bring any results, it may be time to send your request to us.
<Facepalm> Admin, feel free to delete my response too...

Also my dissertation abstract is still better:

The Electron Bernstein wave (EBW) presents an alternative to conventional electron cyclotron resonance heating and current drive in overdense plasmas, where the electromagnetic waves are inaccessible. The EBW is a short wavelength electrostatic wave excited by mode conversion of externally launched electromagnetic (O- or X-) modes. In this experiment, an edge launched X mode tunnels through a narrow evanescent region before conversion to the Bernstein mode, with efficiency maximized near 100% for optimal edge density gradient scale length. No previous observations of RF heating have been observed in the reversed-field pinch (RFP).
The RFP presents a set of unique challenges to RF heating. The confining magnetic field is generated almost entirely from current within the plasma, resulting in a dynamic equilibrium with |B| maximized on the magnetic axis (no high field side exists) and a broad spectrum of current-driven instabilities. Consequent strong edge density fluctuations can diminish coupling to the EBW using OXB conversion, and the multiple internal resonant modes lead to a stochastic magnetic field over much of the plasma minor radius. A close-fitting conducting shell is required for stabilization of ideal external modes; in the case of the Madison Symmetric Torus (MST), a thick shell which also serves as a single turn toroidal field coil, provides vertical field through induced image currents, and stabilizes the slower growing resistive wall mode. Other RFP devices have a thin conducting shell with active saddle coil sets for controlling the resistive mode. The relatively weak magnetic field of the configuration leads to very overdense plasma (ωp/ωc > 5) but also, when combined with inductive current profile control to reduce tearing fluctuations, allows for generation of high beta plasmas (10-25%).
Previous studies of EBW physics in the RFP show efficient coupling, both through reciprocity in a blackbody emission measurement and through optimization of a waveguide grill launching structure, provided the edge density gradient is suitable. Ray tracing studies predict accessibility of EBW heating and current drive over the outer half of the minor radius.
This thesis presents the first observation of RF heating of a RFP plasma using the EBW. The X-mode is launched from the low field side at 5.5 GHz with up to 150kW source power in 3ms long pulses; mode conversion occurs efficiently in the antenna near field (K0Ln=~1); no dedicated limiter surrounding the antenna was used to steepen the edge density gradient. Good coupling due to the naturally steep edge density gradient in the RFP resulted in net/F power ratios of 60-70% at second harmonic. The wave propagates radially inward through a magnetic field that is either stochastic or has broken flux surfaces, before depositing its power on a substantially Doppler-shifted cyclotron resonance. The radial EBW deposition profile is measured through thick-target bremsstrahlung with insertable probes near the plasma periphery on the n=2 harmonic (ω = nωce – k||v||), also allowing a novel measurement of particle transport in the edge (r/a > 0.9) of the RFP. Emission from a fixed limiter shows evidence of EBW absorption on harmonics from n=1-7 in the normal operating range of MST (Ip = 50-500kA).
Deposition location was controllable with |B| and matched analytical models and equilibrium reconstruction. In the thick-shelled MST RFP, the radial accessibility of EBW is limited to r/a > 0.8 (~10cm) by magnetic field error induced by the porthole necessary for the antenna; accessibility in a thin-shelled device with actively controlled saddle coils is likely to be r/a> 0.5 in agreement with ray tracing studies. Confinement timescales of fast electrons were too short to depend on collisional effects; RFP transport causes the observed loss of fast electron population. Radial diffusion rates were probed with EBW heated electrons. Enhanced confinement plasmas reduced perpendicular diffusion and allowed EBW heating in plasmas with beta of 15-20%.
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Andrew Seltzman
www.rtftechnologies.org

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