# Effects of low-Z powders on high-confinement plasmas in DIII-D

Florian Effenberg, Alessandro Bortolon, Livia Casali, Igor Bykov, Filippo Scotti, Huiqian Q. Wang, Robert Lunsford, Federico Nespoli, Florian M. Laggner, Brian A. Grierson, et al.

► To cite this version:

Florian Effenberg, Alessandro Bortolon, Livia Casali, Igor Bykov, Filippo Scotti, et al. Effects of low-Z powders on high-confinement plasmas in DIII-D. 18th International Workshop on H-mode Physics and Transport Barriers, Sep 2022, Princeton, NJ, United States. , 2022. [arXiv:03825757]

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Submitted on 23 Oct 2022

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# Effects of low-Z powders on high-confinement plasmas in DIII-D

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F. Effenberg¹*, A. Bortolon¹, L. Casali², I. Bykov³,⁴, F. Scotti⁵, H.Q Wang³, R. Lunsford¹, F. Nespoli¹, F.M. Laggner¹, B.A. Grierson³, R. Maingi¹, A. Nagy¹, R. Nazikian³, M.W. Shafer⁶ & DIII-D Team

¹Princeton Plasma Physics Laboratory, ²Univ. Tennessee - Knoxville, ³General Atomics, ⁴Univ. of California - San Diego, ⁵Lawrence Livermore National Laboratory, ⁶Oak Ridge National Laboratory, *feffenbe@pppl.gov

PRINCETON
PLASMA PHYSICS
LABORATORY

## Materials are injected in powder form to control plasma-material interactions and pedestal at DIII-D and other devices

* Recent applications: ELM & pedestal control, real-time wall conditioning, impurity transport

* This work: low-Z powders injection into C and W divertor dissipate power and improve wall conditions during H-mode

* BN, Li are more efficient than B for divertor power exhaust; BN most suitable for detachment

* EMC3-EIRENE & DIS show Li & BN ablate in divertor, less retention for B

<figure><img src="image_4.png" /></figure>

## Boron is an effective radiator in colder far scrape-off layer, while lithium radiates close to separatrix

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

## New experiments in closed tungsten divertor (SAS-VW) demonstrate suppression of W source and detachment

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

**Outer strike point located on W coated tiles**

* 65 µm BN injected at ~50 mg/s

* Sustained detachment

* W source (W I) reduces

## The Dust Injection Simulator was coupled to EMC3-EIRENE to enable full-torus treatment of powder & impurity transport

<figure><img src="image_9.png" /></figure>

* **EMC3:** 3D edge transport Monte Carlo code

- Braginski plasma-fluid model for D, T, H

- Trace impurity fluid model

* **EIRENE:** kinetic neutral transport code

* **Dust Injection Simulator (DIS):**

$$R_f = \sum F_{\text{drag,nZ}} + F_{\text{drag,n0}} + F_E + F_{\text{grav}} + F_{\text{centr}}$$

F. Effenberg et al 2021 Nucl. Mat. and Energy 26 100900

Y. Feng et al, Contrib. Plasma Phys. 54 (4-6) 2014

F. Nespoli et al, PoP 28, 073704 2021

## Lithium, boron, and boron nitride powders were injected into the small angle slot (SAS) divertor in DIII-D H-mode

<figure><img src="image_10.png" /></figure>

### PPPL Impurity Powder Dropper

* Li, B, BN powders (40-150 µm)

* flow rates 3-200 mg/s, atomic rates 10²⁰-10²² atoms/s, (1-300 Torr-l/s), particle speed: 5-6 m/s

<figure><img src="image_11.png" /></figure>

A. Nagy et al, Rev. Sci. Instrum. 2018 89, 10K121

A. Bortolon et al 2020 Nucl. Fusion 60 126010

## Boron nitride powder detaches the divertor and reduces ELM fluxes to the divertor targets

<figure><img src="image_12.png" /></figure>

F. Effenberg et al 2022 Nucl. Fusion 62 106015

### Vertical view on upper divertor

<figure><img src="image_13.png" /></figure>

### BN at moderate-high rates

* 65 µm BN injected at ~50-200 mg/s

* Sustained detachment

* ELM frequency and amplitude reduce at the target

## Powders also reduce recycling and intrinsic impurities, allowing access to lower collisionality plasmas

<figure><img src="image_14.png" /></figure>

F. Effenberg et al 2022 Nucl. Fusion 62 106015

## Modeling shows more substantial dilution by boron compared to lithium, boron nitride powders similar to the experiment

<figure><img src="image_15.png" /></figure>

### Measured effective charge

<figure><img src="image_16.png" /></figure>

### Li & B densities and average Z<sub>eff</sub>

<figure><img src="image_17.png" /></figure>

**Next steps:**

* Compare effects in different configurations (USN, LSN, DN)

* Effects on profiles & pedestal

**Acknowledgements:** This work was supported by the United States Department of Energy (DoE) under Grants No. DE-AC02-09CH11466, DE-FC02-04ER54698, DE-FG02-07ER54917, DE-AC52-07NA27344, and DE-AC05-00OR22725. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.