Hadron therapy motivates research dealing with the production of particle beams with ∼100 MeV=nucleon energy and relative energy fluctuation on the order of 1%. Laser-driven accelerators produce ion beams with only tens of MeV=nucleon energy and an extremely broad spectra. Here, a novel method is proposed for postacceleration and monochromatization of particles, leaving the laser-driven accelerator, by using intense THz pulses. It is based on further developing the idea of using the evanescent field of electromagnetic waves between a pair of dielectric crystals. Simple model calculations show that the energy of a proton bunch can be increased from 40 to 56 MeV in five stages and its initially broad energy distribution can be significantly narrowed down.

The cortisol levels in the peripheral blood were measured radioimmunologically at 08.00, 12.00, 16.00, 20.00, 24.00 and 04.00 h in human neonates and infants with ages of 1, 2 and 3 days, 1, 2 and 4 weeks, 2, 3 and 6 months and 1 and 3 years. During the first 2 days of extrauterine life the neonates had high plasma cortisol levels without a circadian rhythm. During the first 2 months there were decreased cortisol levels in the infants, but the diurnal rhythms were still absent, and free-running fluctuations were observed. The typical circadian rhythms of the plasma cortisol levels were present in infants aged 3 months; these rhythms were identical with the diurnal changes of 1- and 3-year-old infants. In the groups of patients studied the data suggest that the circadian rhythm of the adrenocortical function may develop to the adult-type pattern already during early infancy.

A robust method for producing half-cycle-few-cycle pulses in mid-infrared to extreme ultraviolet spectral ranges is proposed. It is based on coherent undulator radiation of relativistic ultrathin electron layers, which are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers in a single-period modulator undulator having an undulator parameter of only K = 0.25 and which is significantly shorter than the resonant period length. By using these electron layers the production of carrier-envelope-phase stable pulses with up to a few nJ energy and down to 30 nm wavelength and 70 as duration is predicted.PACS numbers: 41.60. Cr, 41.50.+h, 41.75.Ht Waveform-controlled few-cycle laser pulses enabled the generation of isolated attosecond pulses and their application to the study of electron dynamics in atoms, molecules, and solids [1]. Intense waveform-controlled extreme ultraviolet (EUV)/X-ray attosecond pulses could enable precision time-resolved studies of core-electron processes by using e.g. pump-probe techniques [2]. Examples are time-resolved imaging of isomerisation dynamics, nonlinear inner-shell interactions, or multiphoton processes of core electrons. EUV pump-EUV probe experiments can be carried out at free-electron lasers (FELs) [3,4]; however, the temporal resolution is limited to the fs regime and the stochastic pulse shape is disadvantageous.The shortest electromagnetic pulses reported to date, down to a duration of only 67 as, were generated by high-order harmonic generation (HHG) in gas targets [5,6]. Isolated single-cycle 130-as pulses were generated by HHG using driving pulses with a modulated polarization state [7]. One drawback of gas HHG is the relatively low EUV pulse energy due to the ionization depletion of the medium. The use of long focal length for the IR driving field, or using strong THz fields for HHG enhancement [8] were proposed to increase the EUV pulse energy. The generation of half-cycle 50-as EUV pulses with up to 0.1 mJ energy is predicted by coherent Thomson backscattering from a laser-driven relativistic ultrathin electron layer by irradiating a double-foil target with intense few-cycle laser pulses at oblique incidence [9,10]. Various schemes, such as the longitudinal space charge amplifier [11,12], or two-color enhanced self-amplified spontaneous emission (SASE) [13,14] were proposed for attosecond pulse generation at FELs. However, the realization of these technically challenging schemes has yet to be demonstrated and precise waveform control is difficult.In this Letter we propose a robust method for producing waveform-controlled pulses down to half-cycle durations in the mid-infrared (MIR) to the EUV spectral ranges. The method is based on coherent undulator radiation emitted by relativistic ultrathin electron layers, which are produced by microbunching of a picosecond electron bunch obtained from microwave electron inject...

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Multicycle THz pulse generation by optical rectification in GaP semiconductor nonlinear material is investigated by numerical simulations. It is shown that GaP can be an efficient and versatile source with up to about 8% conversion efficiency and a tuning range from 0.1 THz to about 7 THz. Contact-grating technology for pulse-front tilt can ensure an excellent focusability and scaling the THz pulse energy beyond 1 mJ. Shapeable infrared pump pulses with a constant intensity-modulation period can be delivered for example by a flexible and efficient dual-chirped optical parametric amplifier. Potential applications include linear and nonlinear THz spectroscopy and THz-driven acceleration of electrons.