Dispersion Engineering and Disorder in Photonic Crystals for Accelerator Applications

The possibility of achieving higher accelerating gradients at higher frequencies with the reduction of the effect of HOMs, compared to conventional accelerating structures, is increasing interest in the possible use of Photonic Crystals (PC) for accelerator applications. In this paper we analyze how the properties of the lattice of a PC resonator can be engineered to give a specific band structure, and how by tailoring the properties of the lattice specific EM modes can either be confined or moved into the propagation band of the PC. We further go on to discuss the role of disorder in achieving mode confinement and how this can be used to optimize both the Q and the accelerating gradient of a PC based accelerating structure. We also examine the use of high disorder to give rise to Anderson Localization, which gives rise to exponential localization of an EM mode. Discussing the difference between the extended Bloch wave, which extends over the entire PC, and the Anderson localized mode

Design of Photonic Crystal Klystrons

2D Pho­ton­ic crys­tals (PC) with de­fects can act as stand­ing-wave res­onators, which offer ben­e­fit of high mode se­lec­tiv­i­ty for build­ing novel RF sources. We in­tro­duce our work on de­sign­ing two-cav­i­ty sin­gle-beam and mul­ti-beam klystrons using tri­an­gu­lar lat­tice metal­lic PCs. We pre­sent the cold test re­sults of the stub-cou­pled sin­gle-beam struc­ture, which show that at res­o­nance a very low re­flec­tion can be ob­tained, and the waves are well con­fined. We also pre­sent bead-pull mea­sure­ment re­sults of field strengths in the de­fect, using mod­i­fied per­tur­ba­tion equa­tion for small unit di­elec­tric cylin­der, which are in very good agree­ment to nu­mer­i­cal re­sults. A 6-beam klystron cav­i­ty is de­signed as a 6-cou­pled-de­fect struc­ture with a cen­tral stub, which only cou­ples to the in-phase mode at the low­est fre­quen­cy. Fi­nal­ly, we pre­sent a fea­si­bil­i­ty dis­cus­sion of using this mul­ti-de­fect PC struc­ture to con­struct an in­te­grat­ed klystron-ac­cel­er­a­tor cav­i­ty, along with nu­mer­i­cal re­sults show­ing a peak ac­cel­er­a­tion field of 22MV/m can be achieved

Giant thermoemf in multiterminal superconductor/normal metal mesoscopic structures

We considered a mesoscopic superconductor/normal metal (S/N) structure in which the N reservoirs are maintained at different temperatures. It is shown that in the absence of current between the N reservoirs a voltage difference $V_{T}$ arises between the superconducting and normal conductors. The voltage $V_{T}$ oscillates with increasing phase difference $\phi$ between the superconductors, and its magnitude does not depend on the small parameter $(T/\epsilon_{F}).$Comment: Resubmited, some changes to Text and Figure

A Holistic Approach to Accelerator Reliability Modeling

Reliability has been identified as a key factor limiting the development of certain particle accelerator applications, for example Accelerator-Driven Systems (ADS) for energy production and waste-transmutation. Previous studies of particle accelerator reliability have been undertaken using conventional techniques, such as Reliability Block Diagrams (RBD), Fault Tree Analysis (FTA), etc. Although limited data surrounding components and their failure modes limits the applicability of conventional techniques for analysing the reliability of particle accelerators. In addition industrial applications of particle accelerators, i.e. energy production, require a real time response to failure. In this paper we exam- ine a holistic approach to accelerator reliability modelling using Electric Network Frequency (ENF) criterion to look for emergent behaviour of the particle accelerator, from com- plex datasets, such as beam current/charge, created by the diagnostics systems during the machines operation. To look for predictive characteristics just prior to a machine trip

Rapid removal of ammonium from domestic wastewater using polymer hydrogels

To date, technologies to recover ammonium from domestic wastewater from the mainstream have not found widespread application. This is largely due to the low ammonium concentrations in these wastewater streams. This paper reports on the use of polymer hydrogels for rapid sorption of ammonium from domestic wastewater coupled with efficient regeneration by mild acid washing. The sorption capacity of the hydrogel was 8.8-32.2 mg NH4-N/g, which corresponds to removal efficiencies ranging from 68% to 80% NH4-N, increasing proportionally with the initial ammonium concentration. It was, however, unaffected by changes in pH, as the sorption capacity remained constant from pH 5.0-8.0. Importantly, effective regeneration of the hydrogels under mildly acidic conditions (i.e. pH 4.0) was demonstrated with minimal loss in sorption performance following multiple sorption/desorption cycles. Overall, this study highlights the potential of low-cost polymer hydrogels for achieving mainstream ammonium recovery from domestic wastewater