A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The source is based on inverse Compton scattering of a high brightness electron bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency standingwave linac and rf photoinjector powered by a single ultrastable rf transmitter at X-band rf frequency. The high efficiency permits operation at repetition rates up to 1 kHz, which is further boosted to 100 kHz by operating with trains of 100 bunches of 100 pC charge, each separated by 5 ns. The entire accelerator is approximately 1 meter long and produces hard x rays tunable over a wide range of photon energies. The colliding laser is a Yb∶YAG solid-state amplifier producing 1030 nm, 100 mJ pulses at the same 1 kHz repetition rate as the accelerator. The laser pulse is frequency-doubled and stored for many passes in a ringdown cavity to match the linac pulse structure. At a photon energy of 12.4 keV, the predicted x-ray flux is 5 × 10 11 photons=second in a 5% bandwidth and the brilliance is 2 × 10 12 photons=ðsec mm 2 mrad 2 0.1%Þ in pulses with rms pulse length of 490 fs. The nominal electron beam parameters are 18 MeV kinetic energy, 10 microamp average current, 0.5 microsecond macropulse length, resulting in average electron beam power of 180 W. Optimization of the x-ray output is presented along with design of the accelerator, laser, and x-ray optic components that are specific to the particular characteristics of the Compton scattered x-ray pulses.
Power supply for Internet of Things (IoT) devices is one of the bottlenecks in IoT development. To provide perpetual power supply to IoT devices, resonant beam charging (RBC) is a promising safe, long-range and high-power wireless power transfer solution. How long distance can RBC reach and how much power can RBC transfer? In this paper, we analyze the RBC's consistent and steady operational conditions, which determine the maximum power transmission distance. Moreover, we study the power transmission efficiency within the operational distance, which determines the deliverable power through the RBC energy transmission channel. Based on this energy transmission channel modeling, we numerically evaluate its impacts on the RBC system performance in terms of the transmission distance, the transmission efficiency, and the output electrical power. The analysis leads to the guidelines for the RBC system design and implementation, which can deliver multi-Watt power over multi-meter distance wirelessly for IoT devices.
A cryogenic composite-thin-disk amplifier with amplified spontaneous emission (ASE) rejection is implemented that overcomes traditional laser system problems in high-energy pulsed laser drivers of high average power. A small signal gain of 8 dB was compared to a 1.5 dB gain for an uncapped thin-disk without ASE mitigation under identical pumping conditions. A strict image relayed 12-pass architecture using an off-axis vacuum telescope and polarization switching extracted 100 mJ at 250 Hz in high beam quality stretched 700 ps pulses of 0. Advances in high average power with high beam quality have also come from operating Yb 3 -doped materials at liquid nitrogen temperature extending by nearly 100 fold the useful output of rod-type amplifiers and demonstrating high-gain and low spatial distortion with excellent performance in the amplification of short pulses [5][6][7].Here we combine the intrinsic advantages of the thin-disk geometry with the thermo-mechanical and thermo-optical leverage afforded by liquid nitrogen cooling Yb 3 :YAG crystals to enable high energy pulses at high average power and diffraction limited performance simultaneously. To achieve high pulse energy, which requires high gain, we are using a variant of the thin-disk: the composite-thin-disk (CTD) pioneered at LLNL [8,9] that mitigates ASE, extending gain-storage performance and aperture scaling. The cryogenic CTD prototypes in these experiments had a 4.5 mm aperture comprising a 1 mm thick 10%Yb:YAG disk optically bonded to a 4 mm thick undoped YAG-crystal "cap" with shaped edges fashioned to eject fluorescence. In this Letter, we report on gain-storage measurements with this CTD prototype compared with an uncapped disk under identical conditions. We also report on the extraction of 100 mJ chirped pulses at 250 Hz from a single CTD using a compact 12-pass strictly relayed optical architecture. Our interest is scaling optical parametric chirped pulse amplifiers (OPCPAs) for applications requiring energetic pulses and high repetition rates such as high-flux highharmonic generation [10]. Further scaling will use the 100 mJ class chirped pulse amplifier reported in this Letter as the first stage to larger Joule class systems. At the heart of our laser driver is a diode pumped cryogenic CTD amplifier assembly depicted in Fig. 1. On the cooled face, the laser-grade high-reflector exists in thermal contact through soldering, with a liquid nitrogen cooled, heat spreader. The opposite face of the disk shaped gain-volume is bonded to the index-matched "cap" of undoped YAG. The function of the cap is to dilute fluorescence, diminishing the deleterious influence of the ASE. The parabolic sidewalls have a smooth specular polish and efficiently eject fluorescence avoiding recirculation. The addition of a fully transparent cap does not affect the predominantly one-dimensional thermal distribution in the gain volume, which in our finiteelement thermal models was nearly identical in the CTD and uncapped disk. The undoped thermally insulated cap does not devel...
We reported on a compact and efficient in-band pumped Nd:YVO 4 partially pumped slab (Innoslab) picosecond amplifier. A new method for mode-matching was demonstrated to simplify the amplifier design. Integrating the benefits of the in-band pumping technique and the excellent thermal management of the Innoslab amplifier design, a 105 W, 8.4 ps laser output was achieved with near-diffraction limited beam quality of M 2 x 1.12 and M 2 y 1.09 in the orthogonal directions. © 2012 Optical Society of America OCIS codes: 140.3280, 140.3530, 140.4050. High average power (>100 W), high repetition rates (>100 KHz), and high beam quality (M 2 < 1.5) ultrafast laser (<10 ps) has significant applications in various scientific research fields, including efficient frequency conversion, optical parametric amplification, and X-ray radiation generation [1][2][3]. Given the commercial development of laser diodes and non-requirement of chirped-pulse amplification, current picosecond lasers are compact, low cost, and reliable. Compared with Ti:sapphire lasers, picosecond lasers are well adapted to the industrial environment and have a more flexible repetition rate and price. They also have gained a growing importance in industrial micromachining [4]. Presently, picosecond lasers with high average power and high repetition rates, combined with near-diffraction limited beam quality, are highly needed.Among picosecond laser crystals, neodymium-doped vanadate (Nd:YVO 4 ) has been the most extensively studied and widely used over the past two decades. With capacity for being pumped efficiently by laser diodes with a short crystal, Nd:YVO 4 has become one of the most popular crystals in all-solid-state lasers. This crystal has a large emission cross-section and polarized emission attributed to its natural birefringence. A number of studies demonstrated the capacity of this crystal based on the regenerative amplifier scheme [5,6]. However, pulse repetition rates have been limited to less than ∼100 KHz and powerful seeding is required to suppress the energy instability at high pulse repetition rates attributed to period doubling bifurcation [7]. High repetition rate (from a few to several hundred megahertz) pulses can be obtained by adopting the master-oscillator power amplifier (MOPA) geometry with high efficiency. A sub-100-W phase-conjugate Nd:YVO 4 bounce amplifier has been reported by Omatsu et al. [8], which produced an 80 W, 100 MHz, 9.2 ps laser output based on two 20 mm long slab crystals pumped at 808 nm. With an Rh-ion-doped BaTiO 3 crystal as a phase-conjugate mirror, the beampropagation factor M 2 was maintained <1.8. Utilizing the same absorption coefficients on both crystallographic axis pumped at 888 nm, McDonagh et al. [9] demonstrated a 111 W, 110 MHz, 33 ps output by a Nd:YVO 4 amplifier containing a 30 mm long bulk crystal based on a 56 W oscillator. The challenge here is to design a compact laser system combining high output power and short pulse duration while maintaining good beam quality.The major drawback of Nd:Y...
An efficient high-power diode-pumped femtosecond Yb:KGW laser is repored. Through optimization of energy density by semiconductor saturable absorber mirror, output power achieved 2.4 W with pulse duration of 350 fs and repetition rate of 53 MHz at a pump power of 12.5 W, corresponding to an optical-to-optical efficiency of 19.2%. We believe that it is the highest optical-to-optical efficiency for single-diode-pumped bulk Yb:KGW femtosecond lasers to date.
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