A. Crisol, F. Bisti, C. Colldelram, M.L. Llonch, B. Molas, R. Monge, J. Nicolás, L. Nikitina, M. Quispe, L. Ribó, M. Tallarida
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
LOREA beamline (BL20) at ALBA Synchrotron is a new soft X-Ray beamline dedicated to investigate electronic structure of solids by means ARPES technique. Optical design has been developed in-house so as most of beamline core opto-mechanics like Monochromator. The design made for LOREA is based on a Hettrick-Underwood grating type that operates without entrance slit. Experience cumulated over years allowed to face the challenge of designing and building UHV Monochromator. The large energy range of LOREA (10-100 eV) requires a device with 3 mirrors and 4 gratings with variable line spacing to reduce aberrations. Monochromator most important part, gratings system, has been carefully designed to be isolated from external disturbances as cooling water, and at the same time having high performances. Deep analytical calculations and FEA simulations have been carried out, as well as testing prototypes. The most innovative part of Monochromator is gratings cooling with no vacuum guards or double piping that are well-known source of troubles. Heat load is removed by copper straps in contact with a temperature controller device connected to fixed water lines. In addition, motion mechanics and services (cabling, cooling) are independent systems. Designs involved give high stability (resonance modes over 60Hz) and angular resolution below 0.1 µrad over 11° range. On mirrors side, it has been used gonio mechanics from MIRAS* plus an eutectic InGa interface between cooling and optics to decouple them. Grating and mirror holders are fully removable from main mechanics to be able to assembled at lab measuring to achieve the best fit. Instrument has been already assembled and motions characterization or stability measurements are giving expected results matching with specifications. * L. Ribó et al., "MECHANICAL DESIGN OF MIRAS, INFRARED MICROSPECTROSCOPY BEAM LINE AT ALBA SYNCHROTRON", presented at MEDSI’16, Barcelona, Spain, September 2016, doi:10.18429/JACoW-MEDSI2016-FRAA03
Right click on video for Picture-in-Picture mode or Full screen display.
Investigation of Thermal Instabilities in the ALBA Cooling System, Based on Numerical Simulations and Experimental Measurements
153
F. Hernández
ESEIAAT, Terrassa, Spain
E. Ayas, J.J. Casas, C. Colldelram, Ll. Fuentes, J. Iglesias, M. Quispe
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
This paper presents an investigation into the thermal instability problems that currently affect the ALBA Cooling System. During these periods of instabilities, which occur for a few hours every week of operation, there are deviations up to +1.5 °C, concerning the nominal temperature of 23 ± 0.2 °C in the four rings of ALBA: Service Area, Booster, Storage and Experimental Hall. This problem has a direct impact on the quality of the beam of the Accelerator. Previous studies have preliminarily concluded that the causes of this problem are due to (1) thermohydraulic anomalies in the operation of the external cogeneration plant, which supplies cold water to ALBA, and (2) cavitation problems in the pumping system (the water mass flow has been reduced to 67% of its nominal value to temporarily mitigate the cavitation). In order to confirm these hypotheses and propose solutions to the problem, an investigation has been developed making use of one-dimensional thermohydraulic simulations, performing Computational Fluid Dynamic (CFD) studies, statistical evaluations of data taken from our control system, and systematic flow measurements in critical areas, with ultrasonic flowmeters. As a result of this research, a set of solutions and recommendations are finally proposed to solve this problem.
Assessment of the Corrosion of Copper Components in the Water Cooling System of ALBA Synchrotron Light Source; Presentation of a Proposal to Mitigate the Corrosion Rate of Copper
171
M. Quispe, E. Ayas, J.J. Casas, C. Colldelram, Ll. Fuentes, J.C. Giraldo, J. Iglesias, M. Pont
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
J. Buxadera, M. Punset
Technical University of Catalonia, The Biomaterials, Biomechanics and Tissue Engineering, Barcelona, Spain
This paper presents the most recent results on the corrosion of copper components in ALBA water cooling system. The studies have been carried out using a variety of techniques: Scanning Electron Microscopy (SEM), Energy-Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD). Representative samples of the Accelerator Facility were examined: Storage Ring Absorbers, Front End Masks, Radio Frequency Cavity Pipes, Experimental Line Mask, Radio Frequency Plant Pipes at Service Area and Booster Quadrupole. The studies show the presence of intergranular, pitting and generalized corrosion. The presence of copper oxide is confirmed, as well as other elements such as Aluminum, Carbon, Sulfur, Silver, Calcium, Silicon, Titanium and Iron in some regions of the samples. Likewise, other elements from circulating water such as Potassium and Chlorine have also been detected. The depth of pitting corrosion is less than 119.4 um for the samples studied, after 10 years of operation. To minimize the corrosion problem, an upgrade of the ALBA cooling system is under study. The objective is to reduce the current corrosion rate by a conservative factor of 5. This change is possible by modifying the characteristics of the cooling water, reducing the dissolved oxygen content to values below 10 ppb and increasing the pH above 7.5. Technical aspects of this upgrade are discussed in this paper.
CFD Predictions of Water Flow Through Impellers of the ALBA Centrifugal Pumps and Their Aspiration Zone. An Investigation of Fluid Dynamics Effects on Cavitation Problems
299
A. González Romero
ESEIAAT, Terrassa, Spain
J.J. Casas, C. Colldelram, M. Quispe
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
Currently, the ALBA refrigeration system pumps present cavitation when operating at their nominal regime. To alleviate this phenomenon temporarily until a definitive solution was found, the water flow was reduced to 67% of its nominal value. As this flow exchanges heat with the cooling water produced in an external cogeneration plant, modifying the working point of the pumps resulted in a reduction of the Accelerator cooling capacity. However, even at such low flow conditions, the flow has an anomalous oscillatory behaviour in the distributor of the aspiration zone, implying that the cause may be in a bad dimensioning of the manifold. This paper presents a study of Computational Fluid Dynamics (CFD) applied to the aspiration zones of the pumps, to investigate the effects of fluid dynamics on cavitation problems and understand what may be happening in the system. The need for such research arises from the urge to recover the accelerator cooling capacity and the constant pursuit for the improvement of the system. The geometries for this study include the general manifold in the aspiration zone and a simplified model of the pump impeller. The simulations have been carried out with the ANSYS-FLUENT software. Studies performed include considering the total water flow in nominal and under current operating conditions. In addition, the cases in which the flow is distributed through the manifold tubes in uniform and non-uniform ways have been treated separately. Pressure and velocity fields are analysed for various turbulence models. Finally, conclusions and recommendations to the problem are presented.
