Process Identification through Test on Cryogenic System

UNICOS (UNified Industrial Control System) is the CERN object-based control standard for the cryogenics of the LHC and its experiments. It includes a variety of embedded functions, dedicated to the specific cryogenic processes. To enlarge the capabilities of the standard it is proposed to integrate the parametrical identification step in the control system of large scale cryogenic plants. Different methods of parametrical identification have been tested and the results were combined to obtain a better model. The main objective of the work is to find a compromise between an easy-to-use solution and a good level of process identification model. The study focuses on identification protocol for large delayed system, the measurement consistency and correlation between different inputs and outputs. Furthermore the paper describes in details, the results and the tests carried out on parametrical identification investigations with large scale systems

Nonresonant Raman spectrum of C60 nanopeapod: C60 polymerization effects

We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one.We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one

Size And Chirality Effects On Raman Spectrum Of Double-Wall Carbon Nanotube Bundle

We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size.We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size

Modelling and simulation of vibrationnal properties of carbon nanotubes and derivatives

The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods.The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods

Raman-active modes in defective peapod

International audienceThe vibrational properties of defective single-walled carbon nanotube filled with C60 fullerene is the subject of the current study. For this aim we use the spectral moments method in the framework of the bond-polarization theory to calculate the nonresonant Raman spectra of hexa-vacancy defective C60 peapods. Essentially, the vibrational properties are closely coupled with the atomic structure of the system. The evolution of the Raman spectrum as a function of the spatial arrangement of defects in carbon nanotubes is discussed. This work provides benchmark theoretical results to understand the experimental data of defective C60 peapod

Raman-Active modes in Homogeneous and Inhomogeneous Bundle of Single-Walled Carbon Nanotubes

In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied.In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied

Nonresonant Raman Spectrum Of Boron Doped Single Walled Carbon Nanotubes

In the present work, We use a force constant model to study the vibrationnel modes of boron doped single walled carbon nanotubes. This model is used to calculate the nonresonant Raman spectra of these nanomaterials in the framework of bond-polarisation theory by using either direct diagonalisation of the dynamical matrix or the spectral moments method. The effect of substitution of carbon by boron atoms shows that the higher Raman frequency region is dominated by a broad bond whereas the lower one is characterized by a shift of radial bonds.In the present work, We use a force constant model to study the vibrationnel modes of boron doped single walled carbon nanotubes. This model is used to calculate the nonresonant Raman spectra of these nanomaterials in the framework of bond-polarisation theory by using either direct diagonalisation of the dynamical matrix or the spectral moments method. The effect of substitution of carbon by boron atoms shows that the higher Raman frequency region is dominated by a broad bond whereas the lower one is characterized by a shift of radial bonds

Finite size effects on Raman spectrum of single-walled boron nitride nanotube

Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs.Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs

Raman active modes in single-walled boron nitride nanotube bundles

We use the spectral moments method in the framework of the bond-polarization theory to calculate polarized nonresonant Raman spectra of chiral and achiral bundles of single walled boron nitride nanotubes (BWBNNTs) as a function of their diameter and chirality. The Spectra are computed for infinite size of BWBNNTs. We used a Lennard-Jones potential to describe the van der waals intertube interactions between tubes in a bundle. We show that the Raman active modes in the low wave number region are very sensitive to the nanotube diameter. We found that for infinite nanotube bundles, additional Radial Breathing Like mode appears in the low wave number region. These results are useful to interpret the experimental Raman spectra of BWBNNTs