No abstract

We demonstrate a novel method to monitor the total angular distribution of the spectrum of hard x-ray emission from a plasma generated with femtosecond laser pulses with an intensity of 5 x 10(18) W/cm2 on a solid target. Measured and calculated angular distributions of x rays show a pronounced anisotropy for MeV photon energies. We complemented the spectral information by demonstrating a (gamma,n) nuclear reaction with a tabletop laser system.

The specular reflectivity of plasma mirrors formed by subpicosecond pulses from a titanium:sapphire laser has been measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity. Laser pulses with energies up to 250 mJ and pulse durations of 90 and 500 fs were focused onto a fused silica substrate. For angles of incidence between 6° and 45° the specular reflectivity increases to values of about 80% for intensities above a certain threshold intensity. The threshold intensity varies with the pulse length but is nearly independent of the angle of incidence. For very high intensities the specular reflectivity drops again to values of only a few percent.

No abstract

No abstract

No abstract

A comprehensive characterization of experimental parameters in a study of proton acceleration by short-pulse laser-solid interactions at intensities up to 10 19 W cm Ϫ2 is reported. Laser pulse and prepulse conditions were measured, with a contrast ratio of the order of 10 Ϫ6 obtained. The focused laser intensity was experimentally calibrated using a time-of-flight spectrometer to resolve the stages of ionization of a target gas. By comparing the measured ion yields with predictions of an atomic tunneling ionization model a factor of 1.5 uncertainty in the focused intensity was determined. Drive mechanisms for mounting solid targets with thickness in the range of 0.2 to 125 m have been developed for use with high-repetition rate lasers. A retro-focus imaging system has also been implemented to position the target relative to the laser focus. The techniques have been applied to study proton acceleration as a function of various laser and target parameters. Measurements of the energy distribution of protons as a function of laser intensity are presented for both mylar and Al targets. A maximum proton energy of 1.5 MeV was observed. A compilation of recent results from a number of laser systems on the conversion efficiency of laser energy to protons is discussed. By comparison, an efficiency of about 0.7% for the present study is encouraging for future tabletop-laser-based ion acceleration.

In the paper we report about the progress made at XTREME technologies in the development of EUV sources based on gas discharge produced plasma (GDPP) technologies and laser produced plasma (LPP) technologies.First prototype xenon GDPP sources of the type XTS 13-35 based on the Z-pinch principle with 35 W power in 2π sr have been integrated into micro-exposure tools from Exitech, UK. Specifications of the EUV sources and experience of integration as well as data about component and optics lifetime are presented.In the source development program for Beta exposure tools and high volume manufacturing exposure tools both tin and xenon have been investigated as fuel for the EUV sources. Development progress in porous metal cooling technology as well as pulsed power circuit design has led to GDPP sources with xenon fuel continuous operating with an output power of 200 W in 2π sr at 4500 Hz repetition rate. With tin fuel an output power of 400 W in 2π sr was obtained leaving all other conditions unaltered with respect to the xenon based source. The performance of the xenon fueled sources is sufficiently good to fulfill all requirements up to the beta tool level.For both the xenon and the tin GDPP sources detailed data about source performance are reported, including component lifetime and optics lifetime. The status of the integration of the sources with grazing incidence collector optics is discussed. Theoretical estimations of collection efficiencies are compared with experimental data to determine the loss mechanisms in the beam path. Specifically contamination issues related to tin as target material as well as debris mitigation in tin sources is addressed.As driver lasers for the LPP source research diode-pumped Nd:YAG lasers have been used to generate EUV emitting plasma. As target material xenon has been employed. Conversion efficiencies have been measured and currently the maximum conversion efficiency amounts to 1 %. The laser driver power of 1.2 kW is currently achieved with a masteroscillator power-amplifier industrial Nd:YAG laser configuration. With this laser, xenon based EUV sources have achieved 10 W EUV power at 13.5 nm emitted into 2π sr solid angle.For the xenon LPP sources detailed data about the achieved source performance including component lifetime and optics lifetime are reported. The status of the integration of the sources with normal incidence collector optics is shown.The potentials and limits of Z-pinch GDPP and LPP EUV source technologies to achieve high volume manufacturing specifications are discussed in this paper.