UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
It is possible to obtain spectral and angular information of inverse Compton sources using only an x-ray imaging device and various foils with K-edges in the many keV energy range. Beam parameters are chosen such that on-axis photons are above the K-edge for a given material, where absorption is strong and there is relatively zero transmission. Photons observed off-axis are red-shifted and fall below the K-edge, therefore being transmitted and creating a “donut” pattern, or "lobes" in the ideal case for a circularly or linearly polarized laser, respectively. We present simulation and experimental results of the double differential spectrum (DDS) for angle and energy of Compton photons generated at the BNL ATF.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
The novel and revolutionary concept of VLA proof of principle is described in this paper. The simulation with the current BNL-ATF parameter shows that electron beam can get net energy from intense laser beam. The initial 20 MeV electron beam with energy spread of 0.001 can get hundreds of keV energy gain with energy spread of 0.010 by interacting with a laser a0=1. BNL-ATF's spectrometer can tell 0.0001 accuracy of energy spread and distinguish 0.001 accuracy energy spread. The proposal has been approved by BNL-ATF and the experiment for this proof of principle is going to be scheduled.
BNL, Upton, Long Island, New York
UCLA, Los Angeles, California
Trains of subpicosecond electron bunches are essential to reach high transformer ratio and high efficiency in compact, beam-driven, plasma-based accelerators. These trains with a correlated energy chirp can also be used in pump-probe experiments driven by FELs. We demonstrate experimentally for the first time that such trains with controllable bunch-to-bunch spacing, bunch length, and charge can be produced using a mask technique. With this simple mask technique, the stability of the bunch train in energy and time is guaranteed by the beam feedback system.
UCLA, Los Angeles, California
USC, Los Angeles, California
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
One of the challenges for plasma wakefield accelerators (PWFAs) is to accelerate a trailing bunch with a narrow energy spread. The real challenge is to produce a bunch train with a least one drive bunch and one trailing bunch. We have demonstrated experimentally at the BNL-ATF a mask technique that can produce trains of bunches with variable spacing in the sub-picosecond range*. This 60 MeV train with one to five drive bunches and a trailing bunch propagates in a 1 to 2 cm long plasma capillary discharge with a variable plasma density. When the plasma density is tuned such that the plasma wavelength is equal to the drive bunches spacing the plasma wakefield is resonantly excited. The distance between the last drive bunch and the trailing bunch is one and a half time that between the drive bunches, putting the trailing bunch in the accelerating phase of the wakefield. The resonance is characterized by a maximum energy loss by all the drive bunches and maximum energy gain by the trailing bunch. Experimental results will be presented.
*P. Muggli et al., Phys. Rev. Lett. {10}1, 054801, 2008
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Funding: Work supported by US Department of Energy.
At the BNL-ATF we have recently demonstrated the generation of trains of electron with sub-picosecond spacing*. These trains of equidistant bunches can be used to resonantly excite large amplitude wakefields in plasmas. The resonance is reached when the plasma wavelength is equal to the drive bunch train spacing. However, in order accelerate an electron bunch with a narrow energy spread, a trailing witness bunch must be generated. The witness bunch must be separated from the last drive bunch by one and a half time the distance between drive bunches. We show that such a drive/witness bunch train can be generated. The mask can also be designed to produce witness bunches trailing the drive bunch train by 2.5,3. 5, times the drive bunch spacing in order to probe the coherence of the plasma wake in subsequent wave bucket. Resonantly driving plasma wakes with trains of bunches could lead to multiplication of the trailing bunch energy by up to the number of bunches in the drive train with high efficiency in a single stage. Experimental results will be presented.
* P. Muggli et al., Phys. Rev. Lett. {10}1, 054801, 2008