Cavity optimization for compact accelerator-based free-electron maser
In previous works [1] we have successfully commissioned pre-bunched beam pumped free electron maser based on Stimulated Coherent Diffraction Radiation (SCDR) generated in an open resonator. An ultra-fast Schottky Barrier Diode (SBD) detector has enabled us to investigate the properties of the radiation in the range from 3 to 5 mm of wavelengths among broad frequencies stored in the cavity as well as the intrinsic properties of the cavity itself. We observed a turn-by-turn SCDR generated by a multibunch electron beam and directly measured the opened cavity quality factor of 11.4. In this report we represent the work directly related to optimization of both the maser system to achieve higher quality factor of the cavity essential to gain soft X-ray production via Thomson scattering in the next stage of the experiment and measurement system for better characterization of the maser light. One way of optimization is to minimize losses of energy due to transmission through resonator mirrors. For this purpose we have designed and constructed a test setup to investigate reflection and transmission properties of different mirror materials. Theoretical calculations have been performed using optical constants and theoretical models of electrical permittivity to compare with experimental results. In this report we summarize the experimental activity, represent new experimental results and represent steps undertaken to achieve the new resonator mirror design. For better understanding of the resonator performance a test of the SBD detector linearity is also demonstrated.
Robert J
We investigate the dependence of the low-temperature photoluminescence linewidths from InP-latticematched InGaAs/InAlAs quantum wells on the low-angle misorientation from the (100) surface of the host InP substrate. Quantum wells were grown on InP substrates misorientated by 0, 0.2, 0.4 and 0.6°; 0.4° was found to consistently result in the narrowest peaks, with the optimal spectral purity of ~4.25 meV found from a 15nm quantum well. The width of the emission from the 15nm quantum well was used to optimize the growth parameters. Thick layers of Si-doped InGaAs were then grown and found to have bulk, low temperature (77K), electron mobilities up to μ ~ 3.5 x 10 4 cm 2 /Vs with an electron concentration of ~1 x 10 16 .
The importance of normative beliefs to the self-prophecy effect.
Asking people to predict whether they will undertake a target behavior increases their probability of performing that behavior. Now referred to as the self-prophecy effect, this phenomenon has been demonstrated across several contexts. Although theoretical explanations for the effect have been offered, empirical evidence for proposed accounts is sparse. The current research tests the theoretically relevant precondition for the effect that normative beliefs--evaluations of what is socially desirable or appropriate--underlie manifestation of the self-prophecy effect. Results of 2 experiments for different behaviors indicate that the act of making a prediction is most effective when normative beliefs are strong. Implications of these findings are discussed in relation to theoretical explanations for the effect and successful use of self-prophecy to promote socially desirable behaviors.