Sharp 10/28/09 NDCX-II Tweaks W M Sharp, A Friedman, D P Grote - LLNL L L Reginato, W L Waldron, J-L Vay - LBNL 12 January 2011

Sharp 10/28/09 2 ASP initially used approximate sizes NDCX-II lattice period is cm, not 28 cm beam-pipe radius is cm, not 4 cm engineers have made minor adjustments to the NDCX-II baseline cathode and extractor voltages are now ramped together space has been added between final gap and plasma for solenoid and gate valve neutralized-drift section design requires beam to focus 1.57 m beyond last gap all waveforms must be realizable previous designs assumed low-voltage tailored waveform on first cell to correct energy ASP obtains good results with the first cell removed... but leaving the first cell off degrades the final pulse changing the 12-cell baseline is problematic at this point Aren’t we done already?

Sharp 8/15/10 3 the NDCX-II baseline design has had many small tweaks lattice period and radius have been corrected plasma neutralization now begins at the proper position the initial beam profile in ASP is now obtained using the redesigned injector waveform an realizable approximation to the first-cell waveform has been developed 3 kV has been added to the cathode voltage a voltage ramp obtained from low-voltage test circuitry is applied at the first cell So what’s been done? gap 1 voltage fitted voltage voltage offset

Sharp 10/28/09 4 new baseline appears nearly as good as the original one current reaching target is 43.3 nC vs 37.3 nC for baseline duration is 0.65 ns vs 0.52 ns for baseline energy is 1.22 MeV vs 1.2 MeV for baseline How well have we done so far? baselinetweaked

Sharp 10/28/09 5 a usable low-current design is needed to prolong source lifetime lithium sources to date require a 1280 o C temperature to produce 1 mA/cm 2 the source lifetime is less than 50 hours at that temperature designs using a 0.5 mA/cm 2 source have been developed for alignment and testing phases What about low-current cases? unaltered baseline fieldsrescaled fields