# Presentation: 737745

## NSTX Scienceand Spherical Torus Path to Fusion Power

- Martin Peng (ORNL@PPPL)
- on behalf of
- the NSTX Team
- Groundbreaking Ceremony for the
**National Spherical Torus Experiment**
- and Dedication of the
**Lyman Spitzer Building**
**Princeton University Plasma Physics Laboratory**
- May 18, 1998

- Ceremony and Dedication, May 18, 1998

## Slide 2

- Ceremony and Dedication, May 18, 1998

## The Science of NSTX

- High plasma pressure in low magnetic field for high fusion power density at low cost
- Good energy confinement in a small-size plasma
- Nearly fully self-driven (bootstrap) plasma current
- Dispersed heat and particle fluxes
- Plasma startup without complicated induction magnet

**NSTX will be a member of a broad ST research effort**
**MAST** (U.K.): complementary magnet configuration, similar size
**Globus-M** (R.F.): innovative RF (lower-hybrid waves)
**Pegasus** (U. Wisc.): even smaller R/a (smaller hole)
**HIT-II** (U. Wash.): coaxial helicity injection startup & current drive
**CDX-U** (PPPL): RF-only startup, RF-energetic particle interactions

- Ceremony and Dedication, May 18, 1998

## A Spherical Torus Fusion Research Community is Growing

- Ceremony and Dedication, May 18, 1998

## START (Small Tight Aspect Ratio Tokamak) and Research Team

***START***

- Ceremony and Dedication, May 18, 1998

## START Reached New Record (~40%) in Average Toroidal t in Well-Confined NBI Plasma (1/98)

*** **=*
*3 times the highest ****t****obtained so far in****tokamaks *
***Central ************ ~ 80%***
*Plasma current ~0.25 MA*
*ORNL Neutral Beam system ~0.7 MW*

***(Courtesy of START Team)***

- 1 m

- Ceremony and Dedication, May 18, 1998

## Spherical Torus Maximizes the Stable Field Line Length over the Unstable Field Line

- Ceremony and Dedication, May 18, 1998

## MHD Stable, High Beta (t = 40%) Plasmas in NSTX Are Calculated

- Ceremony and Dedication, May 18, 1998

## Very High Flow Shearing Rate is Anticipated in NSTX

- EB = (RB/B) (Er/ RB)/R  (RB/B) [d(p/nZeRB)/dR + d(V/R)/dR]

- (pressure gradient)     (rotation)

- EB (NSTX Profile)

- Mach number =	0.5
- 	 		 0

**Very High Flow Shearing Rate is Anticipated in NSTX**

- Ceremony and Dedication, May 18, 1998

## Nearly Self-Driven (BS) Currents at High  Are Also Calculated, Well Aligned with Total Current

**Nearly Self-Driven (BS) Currents at High ******** Are Also Calculated, Well Aligned with Total Current**

- t = 40%
- Bootstrap current fraction = 80%
- Modest driven current at axis and near edge

- Axis

- Edge

- Ceremony and Dedication, May 18, 1998

## NSTX Plasma Exhaust Channel Has Expanded Area of Contact with Material Wall

- Ceremony and Dedication, May 18, 1998

## HIT Demonstrated the Feasibility of Coaxial Helicity Injection Startup

- Plasma current  200 kA
- Injected current  25 kA
- Injection voltage  700 V
- Edge safety factor  10
- Elect. density ~ 61013/cm3
- Electron temp.  70 eV
- Energy efficiency ~ 20%
- NSTX plans to test to ~500 kA

- Ceremony and Dedication, May 18, 1998

## Slide 13

- Ceremony and Dedication, May 18, 1998

## ST Could Enable a Small Fusion Test Device, such as a Volume Neutron Source (VNS) 

**ST Could Enable a Small ****Fusion Test Device****, such as a Volume Neutron Source (VNS) **

- Ceremony and Dedication, May 18, 1998

## ST Can Advance Fusion Science and Technology Using Small-Size Devices

- Ceremony and Dedication, May 18, 1998

## NSTX and World ST Experiments Are Beginning the ST Adventure Toward Fusion Power

- NSTX (and other devices) being built to test our understanding
- High plasma pressure in low magnetic field
- Good energy confinement
- Nearly fully self-driven
- Dispersed plasma fluxes
- Noninductive plasma startup
- Success  a low-cost development path to fusion energy
*We look forward to the formation of NSTX Research Team upon*
*DOE review and decision on NSTX collaboration proposals*

- Ceremony and Dedication, May 18, 1998