High-power solid-state laser programs at China Academy of Engineering Physics have made great progresses in recent years. A three-stage Ti:sapphire laser system, SILEX-I, was completed early in 2004 which could deliver 26-fs pulses at 5TW, 30TW, and 300TW to the corresponding target chambers for diverse applications. SILEX-I has been working very stably since its completion for experiments, demonstrating that it is the most powerful femtosecond Ti:sapphire laser for exploring strong-field phenomena in the world. The SG-III Nd:glass laser facility has been under conceptual design to meet the requirements from laser fusion applications. The SG-III facility is planned to have sixty-four beamlines divided into eight bundles with an output energy more than 100kJ at 0.35μm for 3- to 5-ns pulses. The eight-beamline TIL (Technical Integration Line), the prototype of the SG-III laser facility, has been installed in the new laboratory in Mianyang. The commissioning experiments have been conducted and one of the eight beams has produced 1-ns pulses of 3.0kJ and 1.2kJ at 1.053μm and 0.35μm, respectively. All the eight beamlines will be activated by the end of 2005 and completed in 2006 for operation. Meanwhile, the eight-beam SG-II laser in Shanghai Institute of Optics and Fine Mechanics has been operated for the experiments since 2001 and an additional beam, built in 2004, has been used for plasma backlighting experiments.
Interaction of TW-ps laser with plasma results in a skin layer mechanism for nonlinear (ponderomotive) force driven two dimensional plasma blocks (pistons) if a very high contrast ratio is provided for suppression of relativistic self-focusing. This Skin layer acceleration (SLA)  results in space charge neutral plasma blocks with ion current densities larger than 10<sup>10</sup> Amp/cm<sup>2</sup> [1-3]. Using Ions in the MeV range results in 1000 times higher proton or DT current densities  than the proton fast igniter  is using and may result in better conditions of this fast ignitor scheme. Using ballistic focusing of the generated plasma blocks and a short time thermal expansion of these blocks for increasing their thickness while keeping the high ion current densities, results in conditions favourable for this option of fast ignition of a fusion target. Some details of the interaction processes are still to be analysed but the solutions studies to date are most encouraging.
A Ti:sapphire laser system referred to as SILEX-I with the chirped pulse amplification technology has been built at CAEP which consists of three stages operating at 5TW, 30TW, and 300TW, each having a compressor and target chamber to meet different needs from diverse applications. The first and the second stages work at 10Hz, while the third at single shot. Pulse durations of 26fs have been obtained by installing an acousto-optic programmable dispersive filter (AOPDF) before the stretcher to compensate for the spectral gain narrowing in the regen. By taking a number of advanced measures for spatial beam control, such as spatial beam-shaping, relay-imaged propagation, precise alignment of compressor gratings and OAP, near-diffraction limited focal spots (FWHM) have been obtained. Focused intensities
are measured in the range of (1-5) x 10<sup>20</sup>W/cm<sup>2</sup> with an f/2.2 OAP. The laser system will be able to operate at 500TW and even higher soon. The SILEX-I has been operated for experiments since its completion early in 2004, covering electron and proton acceleration, hot electron production, transport and deposition, neutron production, x-ray radiation, femtosecond laser pulse propagation in air, warm matter, and other strong-field studies. The laser system has shown an excellent stability and reliability and has been the most powerful femtosecond Ti:sapphire laser facility to operate for experiments in recent years.
A peak power of 286-TW Ti:sapphire laser facility referred to as SILEX-I was
successfully built at China Academy of Engineering Physics, for a pulse duration of 30 fs in
a three-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. The beam
have a wavefront distortion of 0.63μm PV and 0.09μm RMS, and the focal spot with an
f/2.2 OAP is 5.7μm, to our knowledge, this is the best far field obtained for high-power
ultra-short pulse laser systems with no deformable mirror wavefront correction. The
peak focused intensity of ~1021W /cm2 were expected.
We have built a three-stage Ti:sapphire laser system at CAEP which could deliver 5-TW, 30-TW and 286-TW pulses to the corresponding target chambers for diverse applications with innovative high-power Ti:sapphire crystal amplifiers. Pulse durations of 30fs have been obtained by installing an acousto-optic programmable dispersive filter (AOPDF) before the stretcher to compensate for the spectral gain narrowing. By taking a number of advanced measures for spatial beam control, near-diffraction limited focal spots (FWHM) have been obtained which, to our knowledge, are the best far fields ever measured for the existing high-power Ti:sapphire laser systems without deformable mirror correction. Focused laser intensity is about 10<sup>21</sup>W/cm<sup>2</sup> measured with an f/1.7 OAP. The laser system has the potential to operate at 500TW and even higher and laser intensities of 10<sup>22</sup>W/cm<sup>2</sup> are expected with deformable mirror for wavefront correction and small f-number fine OAP for tighter focus added to the system in the near future.
It is being clarified why the observations of plane wave geometry <i>interaction within the skin depth</i> of a laser irradiated target are very unique exceptions from the broad stream of the usual experiments of laser plasma interaction. This permits a much more simplified description by plane wave interaction theory for laser pulses of about ps or shorter duration and powers above TW and simplifies computations in contrast to the usual cases with relativistic self-focusing. After establishing theoretically and experimentally the generation of highly directed <i>plasma blocks with ion current densities above 10<sup>10</sup> A/cm<sup>2</sup></i> moving against the laser light or into the target, applications for laser fusion, and a completely new improvement of ion sources for the next generation of accelerators are discussed.
A multihundred-terawatt Ti:sapphire laser facility was built at China Academy of Engineering Physics which could deliver femtosecond pulses at three power levels of 5TW, 30TW and hundreds TW to targets. Near-diffraction-limited focal spots were measured and it was found for the first time that alignment errors of grating groove parallelisms in compressors could be the major mechanism for producing elongated far fields. Pulse durations of 35fs were obtained with a Fastlite-produced AOPDF for spectral compensation.
A new type of MeV ion generation at laser-plasma interaction has been measured based on the observation  that ps neodymium glass laser pulses of about TW and higher power do not produce the relativistic self-focusing based very high ion energies but more than 50 times lower energies. On top the strange observation was reported [fl that the number of the emitted fast ions did not change at variation of the laser focus intensity by a factor 30. This can be explained by the effect that without an inadiating prepulse, a pui plane gcmetnc skin layer interaction mechathsm occurs . Neither relativistic self-focusing is possible nor the process of thermalization of quiver energy by quantum modified collisions. Following our conclusions about the difficulties for the fast ignitor concept of laser fi.ision , we can explain how these mechanisms can be used for studying the self-sustained fusion combustion waves  as known from the spark ignition at laser fusion. We further expect an improvement of the conditions for the experiments with the highest laser fusion gains ever reported where even no pre-compression of the ftision plasma was necessary.
The SG-III laser facility has been proposed to produce 1-ns, 60-kJ blue light pulses for IC Application at China Academy of Engineering Physics. The baseline design suggests that the SG-III be a 64-beam laser facility grouped into eight bundles with clear optical apertures of 30cm by 30cm. The facility consists of multiple subsystems, including the front end, preamplification and injection section, main amplifiers, beam transport and alignment system, switchyard, target area, integrated computer control, and beam diagnostics. The amplifier column in each bundle contains eight beamlets stacked 4 high by 2 wide. Great progress has been made in developing key laser technologies, such as integrated fiber optics, binary optics, adaptive optics, four-pass amplification, large aperture plasma electrode switches, rapid growth of KDP, brand-new laser glass, long flashlamps, precision manufacturing of large optics and metallized self-heating capacitors. Codes have been developed and numerical simulations have been conducted for the optical design of the facility. The design of the Technical Integration Line of 2 by 2 segmented array as a prototype module of SG-II has been optimized and the construction will soon get started.
In this paper, we present the preliminary design of Technical Integration Line (TIL). TIL is a full scale 4 X 2 module of Shenguang-III (SG-III). laser facility with a two-aperture output of 3.0kJ at 3 (omega) in a temporally shaped pulse of 1.0-3.0 ns. The goal of TIl is to demonstrate the laser technology of the proposed SG-III. TIL consists of front-end, pre-amplifier stage, main amplifier stage, diagnostic target systems and control system and the average fluency is designed to operate at 5.0J/cm<SUP>2</SUP> in a 1.0 ns output pulse. The optical scheme of a four-pass main amplifier and a booster amplifier have been chosen. The clear aperture of amplifier is 30 X 30cm<SUP>2</SUP>, and the numbers of Nd:glass disks in the two amplifiers are optimized in system design. Two spatial filters are inserted in the system to remove high spatial frequencies from the beam, and SF1 is the multi-pass spatial filter and SF2 is the transport spatial filter. In order to correct the output wavefront for static and dynamic wavefront aberrations of disk amplifiers, a deformable mirror system is used in the main amplifier stage of TIL.
A computer code has been developed and simulations have been conducted to design the target area optical layout according to the requirements of both the physical and the SG-III laser facility itself for both direct and indirect drive configurations, respectively. The number and location of the required 240 turning mirrors from the output lens of the transport spatial filter to the target chamber have been initially decided, and the mechanical interventions of optical paths have also been solved.
High power solid state laser technologies for application to inertial confinement fusion have been developed over the past three decades in China. The XG-1 laser facility was built in 1984 and upgraded into XG-II in 1993. The SG-1 was completed in 1985 and the upgrade into SG-II will be finished in a few months. As the next step, the SG-III laser facility has been proposed to produce 60-kJ blue light for ICF target physics experiments and is one being conceptually designed. A preliminary baseline design suggest that he SG- III be a 64-beam facility with an output beam size of 25 cm X 25cm. The main amplifier column of 4 high by 2 wide has been chosen as a module. New laser technologies, including multipass amplification, large aperture plasma electrode switches, fast growth of KDP, laser glass with fewer platinum grains, Ce-doped quartz long flash lamps, capacitors with higher energy density, Ce-doped quartz long flash lamps, capacitors with higher energy density and precision manufacturing technique of large optical components have been developed to meet the requirements of the SG-III Project. In addition, numerical simulations are being conducted to optimize the optical design of the facility. The technical integration line with a 4 X 2 segmented aperture array of the amplifiers as a prototype beamline of the SG-III has been scheduled for the next few years.
Development plan and some progress have been made for amplifier of SGIII laser facility. According to this plan, a single-segment amplifier has been designed and experimented to test key units and correct simulating code in National Laboratory of Laser Fusion of China. The preliminary design for 4 X 2 X 3 amplifier prototypes, including amplifier modules, pulsed power, assembly equipment, and optics for SGIII will be finished.
A four pass amplifier system with a small aperture beam reverser has been designed as the main amplifier stage of Technical Integration Line (TIL). TIL is the full scale two- beam prototype for Shenguang-III laser facility which will produce 1 kJ of UV radiation on the target from each beam in 1-3 nanoseconds shaped pulses. The variables were optimized for a fixed output beam aperture of 25 X 25 cm<SUP>2</SUP> and the given parameters of the optical components under the constraints of amplifier gain, fluency damage/filamentation and so on. As a result, the baseline design for TIL was set to a 9-5 configuration.
The ICF Programs in China have made significant progress in solid state laser technology development and advanced laser facility designing with multilabs' efforts in the past years. The eight-beam SG-II laser facility is expected to complete for a 4.8-kJ output at 1.05 micrometers and to operate for target experiments in a few months. A national project, SG-II laser facility, has been proposed to produce 60-kJ blue light for target physics experiments and is being conceptually designed. New laser technologies, including multipass amplification, large aperture plasma electrode switches, fast growth of KDP, laser glass with fewer platinum grains, long flash lamps and precision manufacturing of large optical components are being developed to meet the requirements of the SG-III Project. In addition, numerical simulations are being conducted for the optical design of the new facility. The Technical Integration Line of 4 by 2 segmented array as a prototype module of SG-II with a chamber for laser beams measurements will be first built in the next few years.
Technical Integration Line (TIL) is the full scale two-beam prototype for Shenguang-III laser facility. A four pass amplifier system with small aperture beam reverser has been designed as the main amplification stage for TIL, which will produce 1 kJ of UV radiation on the target from each beam in 1-3 nanoseconds shaped pulses. Two schemes were considered in the preliminary design, one of them employed only small aperture Pockels cell in the reverser, and the other used another larger plasma electrode Pockels cell in the main beam line. Simulated by a fast-running lumped-element computer code, the configuration of baseline scheme for TIL was settled. The basic requirements for optical elements were raised during simulation processing.