LLNL, Livermore, California, USA
Nuclear photonics is an emerging field of research that will require high precision gamma-ray (MeV) sources. In particular, nuclear resonance fluorescence applications necessitate a low (< 1%) relative gamma-ray spectral width. Within this context, Compton scattering, where laser photons are scattered off relativistic electron beams to produce tunable, collimated gamma rays, will produce the desired gamma-ray output. This paper will present the spectral narrowband optimization of such a light source currently being built at LLNL. In this case, PARMELA and elegant simulations of the full 250 MeV, high-gradient X-band linac provide the properties of the high brightness electron bunch. The electron beam simulations are then implemented into our newly developed weakly nonlinear Compton scattering code to produce theoretical gamma-ray spectra. The influence that the electron beam, laser beam and interaction geometry parameters have on the produced gamma-ray spectra will be shown with our simulations.
LLNL, Livermore, California, USA
An X-band test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray (MEGa-Ray) technology at LLNL. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. Of critical import to the functioning of the LLNL X-band system with multiple electron bunches is the performance of the photoinjector. In depth modeling of the Mark 1 LLNL/SLAC X-band rf photoinjector performance will be presented addressing important challenges that must be addressed in order to fabricate a multi-bunch Mark 2 photoinjector. Emittance performance is evaluated under different nominal electron bunch parameters using electrostatic codes such as PARMELA. Wake potential is analyzed using electromagnetic time domain simulations using the ACE3P code T3P. Beam-loading effects and low level rf compensation schemes are explored as well, using a semi-analytic formalism and computer algorithm. Plans for multi-bunch experiments and implementation of photoinjector advances for the Mark 2 design will also be discussed.
LLNL, Livermore, California, USA
CELIA, Talence, France
Numerous electron beam applications would benefit from increased average current without sacrificing beam brightness. Work is underway at LLNL to investigate the performance of X-band photoinjectors that would generate electron bunches at a rate matching the RF drive frequency, i.e. one bunch per RF cycle. A critical part of this effort involves development of photo-cathode drive laser technology. Here we present a new laser architecture that can generate pulse trains at repetition rates up to several GHz. This compact, fiber-based system is driven directly by the accelerator RF and so is inherently synchronized with the accelerating fields, and scales readily over a wide range of drive frequencies (L-band through X-band). The system will be required to produce 0.5 μJ, ~200 fs rise time, spatially and temporally shaped UV pulses designed to optimize the electron beam brightness. Presented is the current status of this system, producing pulses shorter than 2 ps from a cw source.
LLNL, Livermore, California, USA
This presentation will report on the technology choices and progress manufacturing and testing the injector and accelerator of the 250 MeV ultra-compact Compton Scattering X-ray Source under development at LLNL for homeland security applications.
