[en] The proof-of-principle HGHG experiment at 5 (micro) and recent HGHG experiment at DUVFEL have generated significant interests in the FEL community. The more relaxed requirement on electron beam current and emittance to generate coherent deep UV output with much narrower bandwidth and high pulse energy stability, as exhibited by the recent experiment, and its potential to be generalized to soft-x-ray FEL, have attracted much attention. Several labs, including BESSY, ELETRRA, LBL, MIT, and SSRF proposed the development of UVFEL based on HGHG principle or soft-x-ray FEL based on the cascaded HGHG principle. Among them SSRF has already started the construction of an FEL system based on the HGHG principle. Hence it would be a contribution to be able to carry out a first proof-of-principle experiment of cascaded HGHG at DUVFEL. In this paper, they discuss this experiment and several associated experiments that can be carried out at BNL before this experiment and may also have important impact on the development of multi-stage cascaded HGHG FELs. The analysis of recent experiment at DUVFEL shows that it is possible to realize a proof-of-principle cascaded HGHG experiment with existing system parameters and with reasonable cost, as they shall show in the following. This suggested experiment is a cascaded HGHG with two stages. In the future it is possible to generalize it to several stages by other labs. They will also show that even though the DUVFEL is a small facility, with present electron beam parameters and without significant increment of hardware, they can carry out experiments to address several important issues associated with the cascaded HGHG FEL

[en] The proof-of-principle HGHG experiment at 5 μ [1, 2] and recent HGHG experiment at DUVFEL [3] have generated significant interests in the FEL community. The more relaxed requirement on electron beam current and emittance to generate coherent deep UV output with much narrower bandwidth and high pulse energy stability, as exhibited by the recent experiment, and its potential to be generalized to soft-x-ray FEL, have attracted much attention. Several labs, including BESSY, ELETRRA, LBL, MIT, and SSRF proposed the development of UVFEL based on HGHG principle or soft-x-ray FEL based on the cascaded HGHG principle [4, 5]. Among them SSRF has already started the construction of an FEL system based on the HGHG principle [6]. Hence it would be a contribution to be able to carry out a first proof-of-principle experiment of cascaded HGHG at DUVFEL. In this paper, we discuss this experiment and several associated experiments that can be carried out at BNL before this experiment and may also have important impact on the development of multi-stage cascaded HGHG FELs

[en] We present a newly developed method to analyze some non-linear dynamics problems such as the Henon map using a matrix analysis method from linear algebra. Choosing the Henon map as an example, we analyze the spectral structure, the tune-amplitude dependence, the variation of tune and amplitude during the particle motion, etc., using the method of Jordan decomposition which is widely used in conventional linear algebra.

No abstract available

[en] A novel approach, the fermion-spin transformation implement the charge-spin separation, is developed to study the low-dimensional t - J model. In this approach, the charge and spin degrees of freedom of the physical electron are separated, and the charge degree of freedom is represented by a spinless fermion while the spin degree of freedom is represented by a hard-core boson. The on-site local constraint for single occupancy is satisfied even in the mean-field approximation and the sum rule for the physical electron is obeyed. This approach can be applied to both one and two-dimensional systems. In the one-dimensional case, the spinon as well as the physical electron behaves like Luttinger liquids. We have obtained a gapless charge and spin excitation spectrum, a good ground state energy, and a reasonable electron-momentum distribution within the mean-field approximation. The correct exponents of the correlation functions and momentum distribution are also obtained it the squeezing effect and rearrangement of the spin configurations are taken into account. In the two-dimensional case, within the mean-field approximation the magnetized flux state with gap in the spinon spectrum has the lowest energy at half-filling. The antiferromagnetic long-range order is destroyed by hole doping of the order ∼ 10/15% for t - J = 3/5 and a disordered flux state with gapless spinon spectrum becomes stable. The calculated specific heat is roughly consistent with observed results on copper oxide superconductors. The possible phase separation is also discussed at the mean-field level. (author). 56 refs, 6 figs

[en] The linearity of the characteristics of semiconductor radiation detectors based on p-i-n-Si which are designed for operation in a current regime was investigated. It was shown that the dependence of the detector current on the radiation intensity is linear up to values of intensity which create an excess carrier concentration of approximately 10¹⁴cm^-3 in the detector bulk. For practical detector sensing volumes of 0.07 and 0.01 cm³, macimum currents of 240 and 40A, respectively, were recorded on the linear region of the characteristic

[en] Potential-well distortion and the microwave instability in the NSLS-II storage ring are investigated. The longitudinal wakepotential is calculated as a sum of the contributions due to vacuum chamber components distributed around the ring. An approximation to the wakepotential for a 0.05-mm charge distribution length, much shorter than the 4.5-mm length of the unperturbed circulating bunch, is used as a pseudo-Green's function for beam dynamics simulations. Comparison of particle tracking simulations using the TRANFT code with the Haissinski solution shows good agreement below the instability threshold current. Above threshold two regimes are observed: (1) energy spread and bunch length are time-dependent (saw tooth behavior); (2) both are time-independent.

[en] The superconductivity of mixed boson-fermion systems is studied using a simple boson-fermion transformation model. The critical temperature of the superconducting transition is calculated over a wide range of the narrow boson band position relative to the Fermi level. The BCS scenario and boson condensation picture are recovered in two limiting cases of high and low positions of boson band, respectively, with modifications due to boson-fermion interaction. (author). 11 refs

[en] We propose an explanation of several experimental features related to the 'pseudogap' in high T_c cuprates in terms of a spin-charge gauge theory. In this approach, based on a formal spin-charge separation applied to the t-J model, the low energy effective action describes gapful spinons (with a theoretically derived doping dependence of the gap m_s∼J(δ|lnδ|)^1/2, where δ is the doping concentration) and holons with 'small' Fermi surface (ε_F∼tδ) interacting via a gauge field. The main effect of gauge fluctuations is to introduce a dissipation ∼T/χ, where χ is the diamagnetic susceptibility. The competition between the two energy scales, m_s and T/χ, is the root in our approach of many phenomena peculiar to transport properties of the 'pseudogap phase'. A good agreement is found between the experimental data and theoretically derived doping and temperature dependence of many physical quantities, such as in-plane and out-of-plane resistivity, in-plane magnetoresistance, far infrared electronic AC conductivity and spin lattice relaxation rate

[en] Communication networking technologies such as Fieldbus and wireless have become increasingly prevalent in non-nuclear industrial applications. Although they are currently not an integral part of the CANDU I and C architecture, it is expected that future CANDU system retrofit and new build implementations will leverage such technologies to reduce installation and maintenance costs, and to improve reliability and availability. First, an overview of the benefits and the current state-of-the-art of the main process control Fieldbus technologies (Foundation Fieldbus, PROFIBUS, HART) is provided. Current and potential nuclear-specific applications are described, with the focus on the applicability of the technology to upgrading existing NPPs. Finally, technology adoption issues are reviewed, with particular emphasis on qualification for potential use in nuclear safety-related applications. (author)