Due to complexities with oven, the injection experimentswill require preformed H2 plasma.

Laser probe experiments will gain more access and flexibility

If workable, static fill H2 will allow broad control ofplasma density and plasma length.

Motive for preformed H2 plasma

Possible Ionization Injection Schemes at FACET

Helium lithium oven boundary.Good results so far, but limited parameter control.Not well understood, but we are working on it.Evidence that when laser at high power, ionizationinjection was suppressed.

Down-ramp injection.Very challenging. FACET II scheme requires 100 um ramp.Physics challenges to preserve emittance.

Staged injector schemeIonization injection region followed by fully ionized preformed plasma.

Why you cannot use a bounded ionization injection cell

Conflicts with laser transport

Experiments with bounded cell failedafter 10 minutes at FFTB!

Diagram of Gas Cell Used For FFTB Experiments

Electron Beam ionized plasma seen in gas cell viewport

Plasma ion damage to downstream gas cell foil.

1”

Laser

axicon

H2 preformed plasma

Gas Puff Ionization Injection Concept*

*Requires flush and fill approximately every 1000 shots

Solenoid valve gas puffer

Gas jet in 4.5” cube with view port

or less

Gas 1st 2nd W/cm2

H 13.6 eV 2x1014

He 24.6 54.4 1.5x1015

Ne 21.6 41.0 1x1015

Ar 15.8 27.6 3.4x1014

Ionization impurity gas selection

consider secondary ionization by e-beam