# Presentation: 939986

## Reduce neutron production 
Lessen technical complexity 
Permit utilization of current technologies
Rapid prototype testing and improvement
Provide some fusion-reactor customers with what they want

- Reduce neutron production
- Lessen technical complexity
- Permit utilization of current technologies
- Rapid prototype testing and improvement
- Provide *some* fusion-reactor customers with what they want

- or Towards small clean fusion reactors in our lifetime

- S.A. Cohen, B. Berlinger, A. Brooks, C. Brunkhorst, A. Glasser, N. Ferraro, A. Landsman, D. Lundberg, A. Roach

- U.S. DOE contract DE-AC02-76-CHO-3073

## Parity: Symmetry under mirror reflection

- Odd

- Even

## A long time ago in a faraway galaxy .....

- 1957: Christofilos: invents ASTRON
- 1959: Kolb *et al.* produce -pinch FRC
- 1962: Blevin and Thonemann invent RMFe current drive
- 1980s: Jones, Hugrass, Grimm *et al.* rotamak (RMFe) experiments & theory
- 1992-2007: Hoffman *et al.,* 10 MW, Te < 50 eV
- 2000-06: RMFo. Improved heating and confinement predicted. Tests begin.

- Cohen and Milroy (PoP 2000)

## Prediction: RMFo heats electrons and drives current

- Glasser and Cohen (PoP 2001)

*B**o* = 20 G,  rs = 10 cm,  ***RMF*= 0.5 ***ci*

-                         Hamiltonian code simulations

## Predicted ion heating: r = 10 cm,  = 5, Ba = 20 kG

- Predicted ion heating: r = 10 cm,  = 5, Ba = 20 kG

- Cohen and Glasser (PRL 2000)

- Ion  heating ( = R/ci)
- 	Threshold
- 	Saturation
- Heating to temperatures relevant for *aneutronic* fuels
- 	0.1 < |R/ci| < 2
- 	BR/Ba < 0.01
- Gradient in heating efficiency may allow tuning for isotopes

- BR = 128 G

- Cohen, Landsman, Glasser (PoP 2007) tbs

## Theory: RMFo is a fusion physicist’s panacea

- Collisionless electrons (* = L/Coulomb ~ 10-3) in high-_x0010_ H+ plasmas formed by low power RMFo at ci << RMF << ce
- Te > 200 eV at ne ~ 1012 cm-3, DL ~ 5 Vs,  r ~ 3 cm, B_x0010_RMF/pBo< 0.1
- Plasma duration > 1 ms (~ 1000 Alfven) @ 5000 pulses/hour
- Divertors provide density & collisionality control
- Internal flux conservers in an RMF device
- Penetration of RMFo to major axis at low nH0,H2

- Experimental results at PPPL

- Small ( r = 3 cm) low-power (P = 10 kW) device,
- relying on commercial-off-the-shelf equipment (COTS)

- Unique recent achievements

- Theory: RMFo is a fusion physicist’s panacea

## Princeton FRC (PFRC) device: odd-parity RMFo

- Internal flux conservers
-                        1-10

- Diamagnetic
- loops

- Mirror coils

- Spectro-
-     scopy

- Divertor 2

- Divertor 1

- Plasma

- X-ray and visible
- spectrometers

- B0 = 40-400 G
- BM < 5000 G
- PRF < 11 kW
- pH2 = 0.4-100 mT
- >5 ms duration
- 0.5% duty factor
- fRMF: 8-20 MHz

- Pressure
- gauge

-     170 GHz
- interferometer

- Gas feed

- 26-port
-   Pyrex
-    chamber

- RMFo
-   antenna

## With special thanks to Ron Davidson

- For the Opportunity and Support

- _Common features_
-          Linear
-                                                            Superconducting magnets
- (Odd-parity) ICRF antenna

- RF antenna

## Results: fixed RMFo frequency

- PH2 = 1.25 mT
- B0 = 60 G
- BM = 2900 G
- QRMF = 60,  fv = 13.992 MHz
- fs = fv + fp,      fp~ 70 kHz
- maxPRF absorbed ~ 3 kW

- fv = 13.992 MHz

- {

- fp increases with PH2 and B0

- 0 = rDL2 Bo
-      = 24 Vs

- Divertor -> density decay

## Determining RMF penetration depth

- Realization
-  Insert metal pipes on FC axis, measure  f
-  Determine RMFo penetration distance from shift in fs (with plasma) from fvacuum

- Concept
- Resonant frequency, (LC)-1/2, of the RMF system, fs, (antennae, tank circuit + PLASMA) will change if plasma changes system L or C.
- L decreases if plasma acts as a (lossy) conductor, excluding RMFo field from part of the volume.
- f/f∝ L/L ∝ V/V ∝ re2 l,  re is the effective radius inside which RMF does not penetrate.

- With plasma, effects on f of
-     Initial field                   Fill pressure

- Copper flux conserving rings

## FM can produce improvement in RMFo coupling, increases in ne and Dl, and measure of RMF penetration depth
Improvements only if FM in density-decay-phase of discharge
Density flat-top extended at higher fill pressure
f measures RMFo penetration
RMF penetration to major axis at fs= fv

- Improvements only if FM in density-decay-phase of discharge
- Density flat-top extended at higher fill pressure
- f measures RMFo penetration
- RMF penetration to major axis at fs= fv

- Results: modulated RMFo frequency

- fv = 13.992 MHz

## Absolute X-ray brightness, IB, higher than if due to e-+ H+ collisions. Correlation of IB with neutral density.
Te not readily measured late in discharge, at low neutral pressure: May be missing the highest average energy. May be (not) seeing spectra we predicted!*

- Te not readily measured late in discharge, at low neutral pressure: May be missing the highest average energy. May be (not) seeing spectra we predicted!*

- Te from X-ray spectroscopy: Si PiN diode

- Time- and space
- integrated <Te>

- (* Suggestion D. Fong 2/2007)

## Electron trajectory (confinement and heating) studies

- RMFo causes more rapid electron losses from mirror than from FRC.
- Higher B0 gives better confinement at higher BRMF.
- Experimental results *favor* FRC over mirror BUT need e,E improved x 100
- Experiment shows large radial losses

- _PFRC parameters_
- R = 14 MHz
- BM=2900 G
- B0 = 60 G mirror
-         90 G FRC
-         120 G FRC
- rs = 3 cm
-  = 5
- LM= 40.5 cm
- R/ce = 0.045-0.09

- Also
-  DL decreases with z

## “Today and tomorrow”

- January 06: Thicker & fewer Ta-covered FCs, to reduce sputtering & improve RF coupling & diagnostics. Freestanding DLs.
-  to 7 Vs
- Pulse durationto 100 ms, BUT
- No plasma or neutral “pump out”
- RMFo penetration only to r = 2.5 cm
- January 08: HiT-superconducting FCs rFC = 6 cm and PRMF = 20 kW: to reduce radial losses, reduce sputtering, improve confinement, study _x0010_eE at Te > 1 keV, & begin ion heating.
- Higher Field Amplification Factor
- higher **B**
- Larger r

- HiT SC ribbon

- New FC

## Expected plasma parameters for PFRC

- 		             _2006__	_         _2008*__	_      	_2010**_
- Ba (G) 			110 	 	1000 		10000
- rs (cm)			    3		      5		      10
- Peak ne (1013 cm−3 ) 	   0.14 		      1 		      15
- Peak Te (keV) 		    0.3 		       2.5 		      10
- Peak Ti (keV)		    0.001		       0.01		       5
- ωR (107 rad/s) 		    6.2 		       3.8 		       0.6
- BR (G) 			  10 		      50 		    100
- Absorbed power (kW) 	    7 		      60		    200
- τe,E (ms)			   0.01 		       0.13                        4
- Si , Se 			   1, 3 		     3, 14 		 3, 130
- Alfven times/ms 		920 		 1960 		  3400
- G (≥ 1tilt stability) 	    6 		       1.4                         0.03
- Πcoul(≥ 1 RMF penetration)   14 		   110 		      50
- R/ci (0.1-2 ion heating)   150 	 	       8 		        0.07

- *  New FCs and vessel.
- ** New magnets, FCs, and vessel.

## A path to an FRC/RMFo reactor

- A path to an FRC/RMFo reactor

- p + B11 ⇒ 3He4 + 8.7 MeV

- D + He3 ⇒ He4 (3.6 MeV) + p(14.7 MeV)

- D + D    ⇒    T (1.01 MeV) + p(3.02 MeV)
-              ⇒ He3 (0.82 MeV) + n(2.45 MeV)

- Chose D-He3: ameliorate the T creation and ash build-up problems.
- 	Reduce D concentration
- 	Let most fusion products be promptly lost (low B & small R)
- 		J. Dawson: FRCs, p-B11 burning
- 		L. Zakharov: tokamaks, liquid Iithium walls
- 	 	D. Barnes: FRCs, DT burning, heat engine 		Don’t “waste”  on confining *certain* fusion products
- 	Positive electrostatic potential may improve thermal ion
- 		confinement and stability

## Reactor: point design

- Pfusion = 5 MW
- PD-Dneutrons = 50 kW
- ne = 4 x 1014 cm-3
- Te= 60 keV;    nD = nHe3
- THe3 = 200 keV
- TD   =   90 keV
- PRMFo = 2 MW
- PBrems = 0.42 MW
- Ba = 50 kG
- BR = 500 G
- rs = 20 cm
-  = 15
- tshielding = 20 cm
-  = 110 (RMF penetration)
-  = 0.02

**Prompt losses**

## Research plan to an RMFo-heated D-He3 FRC reactor

- Heat electrons (for , current drive,
-                                      and steady state)    2/06
- Maintain field closure (for energy
-                                   confinement)	     8/07
- Heat ions (for fusion)			   10/08
- Effects of fast ion losses			     6/09
- Stabilize plasma (for steady state)             10/09
- Fuel optimization (fusion power & cleanliness)   2/11
- Reactor design (technology testing)	    2/13

-    If RMFo works, reactor development and implementation should progress rapidly.
-    Fuel source will be an important question.

## Potential wells and orbit shapes

- Three main classes of orbits
- Cyclotron - drift clockwise (unstable), P < 0.25
- Betatron - move counter clockwise (stable), P > 0.25
- Figure 8 - mostly drift clockwise (mostly unstable), P < 0.25

- Landsman, Cohen, Glasser, PoP 2004

## Determining Ip, rs, <>, and Te

- Measure DL with calibrated diamagnetic loops
- Field Amplification Factor = pB0/B0 = rfc2/(rfc2-rs2)
- Simulations at measured DL for various Ip & rs. numerical & experimental
- Consistency between FAF and simulations yields rs and Ip
- rs  = 1.9 - 3 cm
- Barnes relation: <> = 1-(rs2/rfc2)/2  ~ 0.75-0.9 (assumes Br = nT = 0 for z > zs)
- Then measure ne ➛Te: 100-200 eV

- nT (arb)

- rs (cm)