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