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SPRG Seminars - Archive
November 15, 2005:
High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding
Cameron Geddes, Lawrence Berkeley National Laboratory
Current particle accelerators for applications from medical radioisotope production to radiation sources are typically limited to accelerating gradients near 50 MV/m to avoid material breakdown, resulting in bulky expensive accelerators. A compact technology for generating intense energetic electron beams, acceleration by high energy density lasers, is studied at LBNL's l'OASIS facility (10TW, 2E19W/cm2). The intense laser pulse drives a space charge wave in a plasma, producing acceleration gradients on the order of 100GeV/m. We used structured plasmas formed by controlled pre heating to guide this drive pulse, maintaining the accelerating field over much longer distances than otherwise possible. Intense electron beams of hundred picoCoulomb charge in percent energy spread at above 80 MeV and with few miliradian divergence were produced, representing qualitative improvement over un-guided experiments*, and opening the door to new applications of laser driven accelerators.
*Geddes et al, Nature, Sept 30 2004, p538-41.