About OMEGA EP
OMEGA EP (extended performance) is an addition to OMEGA and extends the performance and capabilities of the OMEGA Laser System. It will provide pulses having multikilojoule energies, picosecond pulse widths, petawatt powers, and ultrahigh intensities exceeding 1020 W/cm2. These beams are delivered to targets within the OMEGA target chamber as well as an independent chamber within the OMEGA EP target area. The co-location of petawatt capability with the OMEGA compression facility provides a unique platform to experimentally verify laboratory ignition-relevant design models. The short-pulse and long-pulse systems operating jointly are able to interrogate high-temperature and high-density regimes well beyond those currently available. The new laser is adjacent to the OMEGA laser and supports a wide variety of target irradiation conditions when coupled to OMEGA or operated in stand alone mode.
OMEGA EP Mission
Radiography, fast-ignition, and other extreme-field experiments are the missions for OMEGA EP. This system will provide ultrahigh intensities for advanced x-ray and proton-beam radiography of compressed targets. Radiography is an important technique used at inertial confinement fusion (ICF) facilities for capturing a snapshot of driven targets. An intense laser pulse illuminates a block of material located near the target and generates a short burst of x rays or protons that produce a radiograph of the target. OMEGA EP's very high intensities, incident on selected materials, will produce x-ray sources substantially brighter and/or with higher photon energies than the radiation emitted by the target driven by the OMEGA laser. In addition, x-ray photon energies that are much higher than the typical 15-keV x rays emitted by a target imploded with a longer (nanosecond) optical pulse can be produced. This permits backlighting of targets having a higher density or atomic number. The short duration of the x-ray burst also improves the temporal resolution of backlit targets. High-energy protons can be produced in addition to x rays, offering the opportunity to probe the compressed target's ionization state and electromagnetic field.
OMEGA EP will explore the fast-ignition concept for ICF. In fast ignition, a high-intensity short pulse (~10 ps) strikes an imploded target when it reaches peak compression and generates a short burst of energetic electrons. These electrons deposit their energy in the cold, compressed fuel, promptly heating it to initiate a thermonuclear burn wave. By separating the heating from the compression of the target, much lower overall laser energy is needed to achieve ignition. Although fast ignition will ultimately require much higher energies than are currently achievable, OMEGA's uniform compression, coupled with high-energy picosecond pulses from OMEGA EP, will provide a unique capability to study the physics of this concept.
OMEGA EP will also allow scientific exploration into the realm of extreme-field science, including ultrahigh-energy and ultrahigh-intensity experiments.
OMEGA EP Performance
The OMEGA EP Laser System will consist of four beamlines, two with picosecond pulse capability. Two of the OMEGA EP beamlines will have the capability to operate in a pulse-width range of 1 to 100 ps at 1053 nm. For widths of 10 ps or greater, the on-target energy will be up to 2.6 kJ. For pulse widths between 1 and 10 ps, the on-target energy scales as a function of the pulse width due to the damage threshold of the optical coatings at the output of the system. At the 1-ps pulse width, the system will produce 1 PW (i.e., 1 kJ in 1 ps) of optical power on target. The focal spot of the short-pulse beams is 80% of the energy in a 10-μm-radius spot, producing on-target intensities of greater than 2 x 1020 W/cm2.
In addition to the short-pulse capability in two of the beamlines, all four OMEGA EP beamlines will have a long-pulse capability with pulses ranging from 1.0 to 10 ns. This long-pulse (nanosecond) capability will be used to produce preformed plasmas for interaction experiments with the short-pulse beams and for nanosecond, high-energy planar-target experiments in the OMEGA EP target chamber. The OMEGA EP nanosecond pulses are generated and delivered in essentially the same manner as those on OMEGA, including frequency conversion to 351 nm. The long-pulse, on-target UV energies are limited by the UV-optical-coating damage threshold and can reach 2.5 kJ per beam for 1-ns pulses and 6.5 kJ per beam for 10-ns pulses.