Beam Loss Detection System in the Arcs of the LHC

Over the whole circumference of the LHC, Beam Loss Monitors (BLM) will be needed for a continuous surveillance of fast and slow beam losses. In this paper, the location of the BLMs set outside the magnet cryostats in the arcs is proposed. In order to know the number of protons lost on the beam screen, the sensitivity of each BLM has been computed using the program GEANT 3.21, which generates the shower inside the cryostat. The material and the magnetic fields have been described thoroughly in 3-D and the simulation results show the best locations for 6 BLMs needed around each quadrupole. The number of minimum ionizing particles received for each lost proton serves to define local thresholds to dump the beam when the losses are menacing to quench a magne

Production and characterization of activated carbon from barley straw by physical activation with carbon dioxide and steam

In recent years, the growth of environmental protection policies has generated an increase in the global demand for activated carbon, the most widely used adsorbent in many industrial sectors, and with good prospects of implementation in others such as energy storage (electrodes in supercapacitors) and agriculture (fertilizer production). This demand is driving by the search for renewable, abundant and low-cost precursor materials, as an alternative to traditional fossil sources. This study investigates the production of activated carbon from barley straw using physical activation method with two different activating agents, carbon dioxide and steam. Experimental tests under different conditions at each stage of the process, carbonization and activation, have been conducted in order to maximize the BET surface area and microporosity of the final product. During the carbonization stage, temperature and heating rate have been found to be the most relevant factors, while activation temperature and hold time played this role during activation. Optimal conditions for the activation stage were obtained at 800 °C and a hold time of 1 h in the case of activation with carbon dioxide and at 700 °C and a hold time of 1 h in the case of activation with steam. The maximum BET surface area and micropore volume achieved by carbon dioxide activation were of 789 m2/g and 0.3268 cm3/g while for steam activation were 552 m2/g and 0.2304 cm3/g, which represent respectively an increase of more than 43% and 42% for the case of activation with carbon dioxide

First Results of the Beam Gas Ionization Profile Monitor (BGIP) Tested in the SPS Ring

The BGIP is a proposal for a new, non-destructive beam profile monitor for the future Large Hadron Collider (LHC). This device provides the rms beam size value by means of the analysis of the velocity spectrum of the rest gas ions created and accelerated by the beam itself. After a thorough computer simulation study of the related physics, a first prototype of the BGIP has been conceived, built up and installed in the SPS main ring during 1999. This paper contains a short presentation of the simulation work and a description of the test set-up. The first experimental results are presented and compared with theoretical computations

Characterization of thermophysical properties of phase change materials using unconventional experimental technologies

The growing interest in developing applications for the storage of thermal energy (TES) is highly linked to the knowledge of the properties of the materials that will be used for that purpose. Likewise, the validity of representing processes through numerical simulations will depend on the accuracy of the thermal properties of the materials. The most relevant properties in the characterization of phase change materials (PCM) are the phase change enthalpy, thermal conductivity, heat capacity and density. Differential scanning calorimetry (DSC) is the most widely used technique for determining thermophysical properties. However, several unconventional methods have been proposed in the literature, mainly due to overcome the limitations of DSC, namely, the small sample required which is unsuitable for studying inhomogeneous materials. This paper presents the characterization of two commercial paraffins commonly used in TES applications, using methods such as T-history and T-melting, which were selected due to their simplicity, high reproducibility, and low cost of implementation. In order to evaluate the reliability of the methods, values calculated with the proposed alternative methods are compared with the results obtained by DSC measurements and with the manufacturer’s technical datasheet. Results obtained show that these non-conventional techniques can be used for the accurate estimation of selected thermal properties. A detailed discussion of the advantage and disadvantage of each method is given

LHC Beam Loss Monitors

At the Large Hadron Collider (LHC) a beam loss system will be installed for a continuous surveillance of particle losses. These beam particles deposit their energy in the super-conducting coils leading to temperature increase, possible magnet quenches and damages. Detailed simulations have shown that a set of six detectors outside the cryostats of the quadrupole magnets in the regular arc cells are needed to completely diagnose the expected beam losses and hence protect the magnets. To characterize the quench levels different loss rates are identified. In order to cover all possible quench scenarios the dynamic range of the beam loss monitors has to be matched to the simulated loss rates. For that purpose different detector systems (PIN-diodes and ionization chambers) are compared

Spin–glass Magnetism in RFeTi2O7 (R=Lu and Tb) Compounds

AbstractThe compounds RFeTi2O7 (R=Lu and Tb) crystallize at room temperature in centrosymmetric orthorhombic space group Pcnb. There are five non-equivalent positions of the iron ions: the two positions, Fe’ and Fe”, in the octahedron consisting of the Fe’ tetrahedron and Fe” five-vertex polyhedron and the three positions, Fe1, Fe2 and Fe3 in the mixed Fe-Ti octahedra [1]. The populations of the mixed Fe-Ti sites are different. The crystal structure features lead to atomic disorder in the distribution of the magnetic ions in this compound. From low temperature heat capacity, magnetization and frequency dependent ac susceptibility we conclude that both compounds undergo a spin glass transition at TSG=4.5 and 6K for R =Lu and Tb, respectively. Since Lu is not magnetic, in RFeTi2O7 the spin glass behavior is caused by the disordered distribution of the magnetic Fe3+ ions in the different crystallographic positions. The substitution of the magnetic and highly anisotropic Tb ion instead of Lu increases TSG because of the additional Tb-Fe exchange interaction, while the critical exponent of the frequency dependence on temperature hardly varies. The spin glass behavior in these crystalline compounds is caused by the presence of competitive interactions that lead to frustration

Production of gaseous and liquid chemicals by aqueous phase reforming of crude glycerol: Influence of operating conditions on the process

The present work studies the influence of the temperature (200-240 °C), pressure (38-50 bar), glycerol concentration (10-50 wt.%) and mass of catalyst/ glycerol mass flow rate ratio (W/mglycerol = 10-40 g catalyst min/g glycerol) during the aqueous phase reforming (APR) of a glycerol solution obtained from the production of biodiesel. The operating conditions exerted a statistically significant influence on the reforming results. Specifically, the global glycerol conversion and the carbon converted into gas and liquid products varied as follows: 4-100%, 1-80% and 16-93%, respectively. The gas phase was made up of H2 (8-55 vol.%), CO2 (34-66 vol.%), CO (0-4 vol.%) and CH4 (6-45 vol.%). The liquid phase consisted of a mixture of alcohols (monohydric: methanol and ethanol; and polyhydric: 1, 2-propanediol, 1, 2-ethanediol, 2, 3-butanediol), aldehydes (acetaldehyde), ketones (C3-ketones: acetone and 2-propanone-1-hydroxy; C4-ketones: 2-butanone-3-hydroxy and 2-butanone-1-hydroxy; and cyclic ketones), carboxylic acids (acetic and propionic acids) and esters (1, 2, 3-propanetriol-monoacetate), together with unreacted glycerol and water. The relative amount (free of water and un-reacted glycerol) of these compounds in the liquid phase was as follows: monohydric alcohols: 4-47%, polyhydric-alcohols: 14-68%, aldehydes: 0-5%, C3-ketones: 2-33%, C4-ketones: 0-10%, ciclo-ketones: 0-6%, carboxylic acids: 2-43%, and esters: 0-46%. This process turned out to be highly customisable for the valorisation of crude glycerol for the production of either gaseous or liquid products. Gas production is favoured at a low pressure (39 bar), high temperature (238 °C), high W/mglycerol ratio (38 g catalyst min/g glycerol) and employing a 15 wt.% glycerol solution. A high pressure (45 bar), medium temperature (216 °C), medium W/mglycerol ratio (22 g catalyst min/g glycerol) and the feeding of a 16 wt.% glycerol solution favours the production of liquid products

Magnetic Anisotropy of Maghemite Nanoparticles Probed by RF Transverse Susceptibility

AbstractWe present radio frequency magnetic transverse susceptibility measurements on γ-Fe2O3 nanoparticles, which yield an estimation of their effective anisotropy constant, Keff as a function of nanoparticle size. The resulting values range from 4 to 8 × 104 erg/cm3, being on the order of the magnetocrystalline anisotropy in bulk maghemite. Keff values increase as the particle diameter increases. Evidences of anisotropy field distribution given by the size distribution in the samples, and interparticle interactions that increase as the particle size increases, are also observed in the TS measurements. The effects of such interparticle interaction overcome those of thermal fluctuations, in contrast with the behavior of other iron oxide particles