Adriana Wawrzyniak

Dielectric and electro-optic behaviour of two chiral compounds and their antiferroelectric mixtures

Dielectric and electro-optic properties of two chiral compounds (MHPOBC analogues) and their three antiferroelectric mixtures have been studied. Mixtures of both compounds show SmA*, SmC*α, SmC* and an induced antiferroelectric phase, which is not present for pure substances. All materials were studied using differential scanning calorimetry, frequency domain dielectric spectroscopy and the reversal currents method. Spontaneous polarisation of the mixtures is between 200 and 280 nC/cm2; in the antiferroelectric phase it depends linearly on temperature. Ferroelectric and antiferroelectric phase of mixtures display a mono-domain texture grown in a strong electric field upon slow cooling from the SmA* phase. In the SmC* a domain mode was observed under the bias field, while the antiferroelectric phase shows two characteristic dielectric relaxation processes that are weakly bias field dependent. The low frequency relaxation is not a single Debye-type process, and it also shows up without a bias field. The dielectric data will be discussed based on the Parry-Jones–Elston theory.

The MAX IV Facility

The MAX IV facility is a planned successor of the existing MAX facility. The planned facility is described below. It consists of two new synchrotron storage rings operated at different electron energies to cover a broad spectral region and one linac injector. The linac injector is also meant to be operated as a FEL electron source. The two rings have similar low emittance lattices and are placed on top of each other to save space. A third UV light source, MAX III, is planned to be transferred to the new facility.

Dielectric Spectroscopy of Bent-Core Thioesters' B Phases

Banana-shaped homologoues 1,3-phenylene bis{4-[(4-alkoxybenzoyl) sulfanyl]benzoate}, in short nOSOR, where n denotes the number of carbon atoms in the end chains, have been studied using dielectric and electrooptic methods. 9OSOR shows a ferroelectric B1 phase, whereas 12OSOR, 14OSOR exhibit antiferroelectric B2 phase. Dielectric spectra have been measured for two alignments of B2 phase. In the low frequency range a broad collective relaxation process is observed under bias field. This process is connected with fluctuations of ferroelectric domains. The high frequency relaxation originates from molecular reorientation around the long axis.

Mechanical aspects of installation of integrated magnets at Solaris synchrotron storage ring

Solaris synchrotron storage ring which has been assembled at the beginning of the 2015, consist of twelve integrated magnets blocks performing the part of double bend achromat. Both magnets as well as the whole ring as concept is a replica of Max IV 1.5 GeV ring and utilize pioneering integrated magnets approach. Solaris ring assembly forewent that of its Swedish twin. It is a successful proof of principle experiment showing the feasibility of the chosen approach. On the other hand it was an exercise which brought the knowledge on mechanical behavior of the magnets blocks and matching components, which is of unique importance for further integrated magnets implementations. Hereby we present selected issues related to the ring assembly: block stiffness verification and straightness rectification, vacuum chamber installation, alignment and mechanical stability of the assembled system.

Frederiks Transition in the Nematic and Smectic A Phases of Polar Thioesters

Dielectric and electro-optic properties of two homologues of 4-chlorophenyl 4′-n- alkoxythiobenzoates, showing nematic and smectic A phases with positive dielectric anisotropy, were studied. Planar alignment of the nematic was obtained upon slowly cooling from the isotropic phase using ITO planar cell. Upon further slowly cooling to the smectic phase one can obtain its planar texture. Reversible Frederiks transition was observed for nematic phase in AC field. It is possible to measure the splay elastic constant which changes discontinuously at the nematic-smectic A transition. However, in the smectic phase Frederiks transition was irreversible and the threshold voltage was much higher.

Effective Cycling and Ramping

The National Synchrotron Radiation Centre Solaris, Krakow, Poland has been successfully built in collaboration with several institutes and organizations. The MAX IV Laboratory, Lund, Sweden and ElettraSincrotrone, Trieste, Italy, are the most important synchrotron partners. Solaris has built, as an adaptation of MAX IV, 1.5 GeV storage ring and linear accelerator based on the same components, therefore the device server for the magnet circuit has been developed by MAX IV. Ramping was included in expert consultancy services contract won by Elettra-Sincrotrone. Solving problem with the power supplies stability and thanks to snapshots usage as steps for the ramping it was possible to ramp the beam without losing current linearly.

Status of the Solaris Control System - Collaborations and Technology

The Solaris is a synchrotron light source starting just now in Krakow, Poland. It is built with strong collaboration with other European accelerator facilities. The MAX-IV project in Lund, Sweden and Tango Community are the most important partners in the project in respect to the control system. Solaris has built a twin copy of MAX-IV 1.5GeV ring and linear accelerator based on the same components as the ones of MAX-IV. Thus, both facilities share know-how and apply similar technologies for the control system, among them the Tango CS is used for software layer. Status of the control system in Krakow as well as collaborations and technological choices impact on its success are presented in this paper. THE ACCELERATOR AND BEAMLINES The Solaris machine is 1.5GeV storage ring the same as one of the MAX-IV supplied with a linear accelerator providing electron beam up to 600MeV. Since the linac is not providing full energy beam there is need of energy ramping in the storage ring. This is a difference to MAXIV setup. The Solaris project includes also two beamlines. One is using bending magnet radiation with XAS and PEEM end-stations and the other is basing on undulator source with an UARPES end-station [1]. The accelerators and beamlines are installed except few components of PEEM beamline and two Landau cavities in the storage ring. There is on-going commissioning of the accelerator [2]. The latest result is accumulation of 20mA current in the storage ring which then has been ramped to full energy of 1.5GeV. Currently certain optimization has been done that let us by the day of writing this paper (17.10.2015) accumulate the current of 48mA. The work is in progress to do energy ramping of this much od current. For now limitation are instabilities due to the ion trapping process. There is planned upgrade shutdown starting end of November 2015 till beginning of January 2016. During this period the landau cavities will be installed as well as missing components of the PEEM beamline. Network infrastructure will be supplemented with a new core switch to enable 10GBps connections through the whole network. It is also planned to do upgrade of the Tango control system to the newest version of Tango 9.1. After the shutdown commissioning of the beamlines will proceed. It is expected that the Solaris will be ready for the first external users in second half of 2016.

Determination of the Landau's Coefficients for a Liquid Crystal Showing a De Vries Phase

A ferroelectric liquid crystal showing a de Vries phase is studied by the mean of dielectric and electro-optical measurements. Due to a strong electro-clinic effect close to the smectic A*-smectic C* phase transition, a non linear electrical response is observed. The non linear dielectric characterization of this compound and the confrontation with a theoretical model allow us to extract the Landaus parameters of this material. The results are discussed on the basis of other data obtained by different measurement techniques. As an example, we confirm the second order smectic A*-smectic C* phase transition.