Fully plasma-based electron injector for a linear collider or XFEL

We demonstrate through high-fidelity particle-in-cell (PIC) simulations a simple approach for efficiently generating <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mn>20</a:mn><a:mo>+</a:mo></a:math> GeV electron beams with the necessary charge, energy spread, and emittance for use as an injector in a future linear collider or a next generation XFEL. A high quality injected bunch is generated by self-focusing an unmatched electron driver in a nonlinear plasma wakefield. Over pump depletion distances, the drive beam dynamics and self-loading effects lead to high energy, low-energy spread output beams. For plasma densities of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msup><b:mn>10</b:mn><b:mn>18</b:mn></b:msup><b:mspace width="0.28em"/><b:mi mathvariant="normal">c</b:mi><b:msup><b:mi mathvariant="normal">m</b:mi><b:mrow><b:mo>−</b:mo><b:mn>3</b:mn></b:mrow></b:msup></b:mrow></b:math>, PIC simulation results indicate that self-injected beams with <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:mn>0.52</f:mn><f:mspace width="0.28em"/><f:mi mathvariant="normal">n</f:mi><f:mi mathvariant="normal">C</f:mi></f:mrow></f:math> charge can be accelerated to 20 GeV with projected core energy spreads of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mrow><j:mo>≲</j:mo><j:mn>1</j:mn><j:mo>%</j:mo></j:mrow></j:math>, normalized slice emittances of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mn>110</k:mn><k:mspace width="0.28em"/><k:mi mathvariant="normal">n</k:mi><k:mi mathvariant="normal">m</k:mi></k:mrow></k:math>, peak normalized brightness of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:mrow><o:mo>≳</o:mo><o:msup><o:mn>10</o:mn><o:mn>19</o:mn></o:msup><o:mspace width="0.28em"/><o:mi mathvariant="normal">A</o:mi><o:mo>/</o:mo><o:msup><o:mi mathvariant="normal">m</o:mi><o:mn>2</o:mn></o:msup><o:mo>/</o:mo><o:msup><o:mi>rad</o:mi><o:mn>2</o:mn></o:msup></o:mrow></o:math>, and transfer efficiencies of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"><s:mrow><s:mo>≳</s:mo><s:mn>44</s:mn><s:mo>%</s:mo></s:mrow></s:math>.