Showing papers on "Calorimeter published in 2007"

Energy resolution of the barrel of the CMS Electromagnetic Calorimeter

Abstract: The energy resolution of the barrel part of the CMS Electromagnetic Calorimeter has been studied using electrons of 20 to 250 GeV in a test beam. The incident electron's energy was reconstructed by summing the energy measured in arrays of 3 × 3 or 5 × 5 channels. There was no significant amount of correlated noise observed within these arrays. For electrons incident at the centre of the studied 3 × 3 arrays of crystals, the mean stochastic term was measured to be 2.8% and the mean constant term to be 0.3%. The amount of the incident electrons' energy which is contained within the array depends on its position of incidence. The variation of the containment with position is corrected for using the distribution of the measured energy within the array. For uniform illumination of a crystal with 120 GeV electrons a resolution of 0.5% was achieved. The energy resolution meets the design goal for the detector.

Response uniformity of the ATLAS liquid argon electromagnetic calorimeter

Abstract: The construction of the ATLAS electromagnetic liquid argon calorimeter modules is completed and all the modules are assembled and inserted in the cryostats. During the production period four barrel and three endcap modules were exposed to test beams in order to assess their performance, ascertain the production quality and reproducibility, and to scrutinize the complete energy reconstruction chain from the readout and calibration electronics to the signal and energy reconstruction. It was also possible to check the full Monte Carlo simulation of the calorimeter. The analysis of the uniformity, resolution and extraction of constant term is presented. Typical non-uniformities of 5 ‰ and typical global constant terms of 6 ‰ are measured for the barrel and endcap modules.

Differential AC-chip calorimeter for glass transition measurements in ultra thin polymeric films

Abstract: A differential AC-chip calorimeter capable to measure the glass transition in nanometer thin films is described. Due to the differential setup pJ/K sensitivity is achieved. Heat capacity can be measured for sample masses below one nanogram even above room temperature as needed for the study of the glass transition in nanometer thin polymeric films. The calorimeter allows for the frequency dependent measurement of complex heat capacity in the frequency range from 1 Hz to 1 kHz. The glass transition in thin films of polystyrene (PS) (100–4 nm) and polymethylmethacrylate (PMMA) (400–10 nm) was determined at well defined experimental time scales. No thickness dependency of the glass transition temperature was observed within the error limits (±3 K) - neither at constant frequency nor for the traces in the activation diagrams (1 Hz–1 kHz).

Determination of the specific heat capacity of a graphite sample using absolute and differential methods

Abstract: An experimental assembly has been constructed to measure the specific heat capacity of macroscopic graphite samples at room temperature. The same batch of graphite constitutes the core of a graphite calorimeter, which is currently being realized to measure the absorbed dose due to ionizing radiation. Two different experimental procedures have been applied. In the first method the specific heat capacity of graphite was measured directly, where its value is corrected for the influence of impurities. The second method, to our knowledge not previously applied to macroscopic samples, is based on a series of differential measurements where no correction for added impurities is needed. By its nature, the second method reduces systematic effects. The specific heat capacity of a particular graphite sample is determined to be 706.9 J K−1 kg−1 with a combined relative standard uncertainty of 9 parts in 104 at 295.15 K. The specific heat capacity of cyanoacrylate has also been determined.

Enthalpy and Solubility Data of H2S in Water at Conditions of Interest for Geological Sequestration

Abstract: The dissolution of hydrogen sulfide in water was studied by measuring the heat of mixing ΔHmix at conditions of interest for geologic storage of acid gases in deep aquifers. The measurements were performed with a new mixing unit equipped with a Hastelloy tubing, developed specifically for an isothermal differential heat flux calorimeter of Setaram. The heats of mixing were determined at target temperatures of 323, 353, and 393 K and pressures up to 31 MPa in the regions where the solution is unsaturated or saturated by H2S, that is, gaseous, liquid, or supercritical states. The concentration dependence of ΔHmix allowed the simultaneous determination of the limiting enthalpy of solution ΔHsol and the gas solubility limit. The agreement between our solubility results and the data from the direct phase equilibrium measurements reported in literature was good. Although no calorimetric data exist for verifying the correctness of ΔHsol values, their internal consistency was tested by conversion to the low press...

Fire Safety Assessment of Halogen-free Flame Retardant Polypropylene Based on Cone Calorimeter

Abstract: This study addresses the fire performance of polypropylene compounded with different flame retardants in the cone calorimeter tests and UL-94 burning tests. The parameters measured include heat release rate, time to ignition, smoke, and CO/CO2 yields, on the basis of which fire hazard analysis is carried out. By injection-molding different burn-rated polypropylene composites into television back-enclosures and testing them in a full-scale cone calorimeter, we find that the one formulation of V-0 rating in the vertical burning test shows excellent flame retardance.

Heavy ion physics at the LHC with the ATLAS detector

Abstract: The ATLAS detector at CERN will provide a high-resolution longitudinally segmented calorimeter and precision tracking for the upcoming study of heavy ion collisions at the LHC ( GeV). The calorimeter covers |η| < 5 with both electromagnetic and hadronic sections, while the inner detector spectrometer covers |η| < 2.5. ATLAS will study a full range of observables necessary to characterize the hot and dense matter formed at the LHC. Global measurements (particle multiplicities, collective flow) will provide access into its thermodynamic and hydrodynamic properties. Measuring complete jets out to 100's of GeV will allow detailed studies of energy loss and its effect on jets. Quarkonia will provide a handle on deconfinement mechanisms. ATLAS will also study the structure of the nucleon and nucleus using forward physics probes and ultraperipheral collisions, both enabled by segmented zero degree calorimeters.

An absorbed dose to water standard for HDR 192Ir brachytherapy sources based on water calorimetry: numerical and experimental proof-of-principle.

Abstract: Water calorimetry is an established technique for absorbed dose to water measurements in external beams. In this paper, the feasibility of direct absorbed dose measurements for high dose rate (HDR) iridium-192 (192Ir) sources using water calorimetry is established. Feasibility is determined primarily by a balance between the need to obtain sufficient signal to perform a reproducible measurement, the effect of heat loss on the measured signal, and the positioning uncertainty affecting the source-detector distance. The heat conduction pattern generated in water by the Nucletron microSelectron-HDR 192Ir brachytherapy source was simulated using COMSOL MULTIPHYSICS software. Source heating due to radiation self-absorption was calculated using EGSnrcMP. A heat-loss correction k(c) was calculated as the ratio of the temperature rise under ideal conditions to temperature rise under realistic conditions. The calorimeter setup used a parallel-plate calorimeter vessel of 79 mm diameter and 1.12 mm thick front and rear glass windows located 24 mm apart. Absorbed dose was measured with two sources with nominal air kerma strengths of 38 000 and 21 000 U, at source-detector separations ranging from 24.7 to 27.6 mm and irradiation times of 36.0 to 80.0 s. The preliminary measured dose rate per unit air kerma strength of (0.502 +/- 0.007) microGy/(s U) compares well with the TG-43 derived 0.505 microGy/(s U). This work shows that combined dose uncertainties of significantly less than 5% can be achieved with only modest modifications of current water calorimetry techniques and instruments. This work forms the basis of a potential future absolute dose to water standard for HDR 192Ir brachytherapy.

The zero degree calorimeters for the ALICE experiment

Abstract: The Zero Degree Calorimeters (ZDC) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC, providing a direct measure of the centrality of the collisions. ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the shower particles in silica optical fibers embedded in a dense absorber. The main characteristics of the ZP and ZN detectors are described in this article. The calorimeters were tested at the CERN SPS using pion and electron beams with momenta ranging from 50 to 200 GeV / c . Test beam results such as the calorimeter response, the energy resolution, the signal uniformity and the localizing capability are presented.

Comparison between high-energy proton and charged pion induced damage in Lead Tungstate calorimeter crystals

Abstract: A Lead Tungstate crystal produced for the electromagnetic calorimeter of the CMS experiment at the LHC was cut into three equal-length sections. The central one was irradiated with 290 MeV/c positive pions up to a fluence of (5.67 +- 0.46)x10^13 /cm^2, while the other two were exposed to a 24 GeV/c proton fluence of (1.17 +- 0.11) x 10^13/ cm^2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed over two years. The comparison of the radiation-induced changes in light transmission for these crystals shows that damage is proportional to the star densities produced by the irradiation.

The DREAM Project—Results and plans

Abstract: High-precision jet spectroscopy will be increasingly important in future high-energy accelerator experiments, particularly at a Linear e + e - Collider DREAM, a novel type of calorimeter, appears to be well suited for this task The key aspect of this detector is the simultaneous measurement of the scintillation light and the Cherenkov light generated in the shower development process By comparing these two signals (which are provided by different types of optical fibers), the electromagnetic shower fraction can be measured event by event, both for single hadrons and for jets, and the effects of fluctuations in this fraction can be eliminated As a result, the DREAM calorimeter has impressive performance characteristics The application of the DREAM principles in homogeneous calorimeters, which has the potential of providing ultimate calorimeter performance, is also discussed

Molar heat capacities, thermodynamic properties, and thermal stability of trans -4 -(Aminomethyl )cyclohexanecarboxylic acid

Abstract: The low-temperature heat capacities of trans-4-(aminomethyl)cyclohexanecarboxylic acid were measured with an adiabatic calorimeter over the temperature range from (82 to 378) K. The heat capacity curve was smooth and continuous, which indicated that the compound was stable over the whole temperature range. Thermal decompositions of the compound were studied by thermogravimetry (TG) and the possible mechanism of the thermal decomposition was deduced. The energy of combustion of the compound was determined, and the standard enthalpy of combustion, ΔcHϑ, and standard enthalpy of formation, ΔfHϑ, were calculated.

The response of CMS combined calorimeters to single hadrons, electrons and muons

Abstract: We report on the response of the combined CMS electromagnetic (EB) and hadronic barrel (HB) calorimeters to hadrons, electrons and muons in a wide momentum range from 1 to 350 GeV/c. To our knowledge, this is the widest range of momenta in which any calorimeter system is studied. These tests, carried out at the H2 beam-line at CERN, provide a wealth of information, especially at low energies. We analyze in detail the dierences in total calorimeter response to charged pions, kaons, protons and antiprotons and discuss the underlying phenomena. These data will play a crucial role in the thorough understanding of jets in CMS.

A tera-pixel calorimeter for the ILC

Abstract: To extract the physics required at the International Linear Collider, the detectors will need a jet energy resolution of 30%/radicE (GeV). The most promising approach to reach that goal is the use of particle flow algorithms. Particle flow algorithms measure jet energies by combining both tracking and calorimeter information. This requires the use of highly granular calorimeter systems. For the electromagnetic calorimeter (ECAL) the choice is to use silicon-tungsten sampling calorimeters with a highly granular readout. We propose to use Monolithic Active Pixel Sensors (MAPS) as both sensor and readout for such a calorimeter. This novel design would have an extremely fine granularity of 50 x 50 mum2 with binary readout. With a total area of 2000 m2 of silicon this leads to a "Tera-Pixel" ECAL. An overview of the MAPS detector concept will be given along with the potential advantages of this design. For the optimization of the design detailed sensor simulations have been used. A first prototype sensor using MAPS has been produced and we show first results obtained with this sensor. We also address system level issues like the required DAQ bandwidth and the power consumption.

Electron signals in the Forward Calorimeter prototype for ATLAS

Abstract: A pre-production prototype of the Forward Calorimeter (FCal) for the ATLAS detector presently under construction at the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland, was exposed to electrons in the momentum range from 20 to 200 GeV/c in a test beam experiment at CERN in 1998. The measured performance, including a signal linearity within about ±1% and a high energy limit in the relative energy resolution of about 4%, meets the expectations for this kind of calorimeter, and exceeds the physics requirements for successful application in ATLAS.

Combination of Transient Plane Source and Slug Calorimeter Measurements to Estimate the Thermal Properties of Fire Resistive Materials

Abstract: The thermal properties of fire resistive materials (FRMs) as a function of temperature critically influence their ability to protect a (steel) structure during a fire exposure. Measurement of these properties is complicated by the microstructural heterogeneity of typical FRMs, the need to measure properties over a wide temperature range from room temperature to 1000°C and higher, and the reactions, phase changes, and volumetric changes that the materials may undergo during exposure to elevated temperatures. This paper presents an integrated approach for determining thermal properties via a combination of two experimental techniques, namely the transient plane source and the slug calorimeter methods. The former is utilized to provide an estimate of the volumetric heat capacity and a room temperature thermal conductivity value for the FRM under study, while the latter is employed to estimate the variation in effective thermal conductivity with temperature, including the influences of reactions and mass transport during multiple heating/cooling cycles. The combination of the two techniques is demonstrated for four different inorganic-based FRMs. Their extension to organic (intumescent) systems is also discussed.

Monitoring and Evaluation of Cement Hydration by Semi-Adiabatic Field Calorimetry

Abstract: This paper describes the use of a recently developed, inexpensive portable semi-adiabatic calorimeter for monitoring cement hydration in concrete and mortar. The calorimeter measures the temperature as a function of time at the bottom of eight individual 3x6 cylinders with concrete or mortar. The measured temperature profile is used to evaluate the overall hydration performance of cementitious mixtures, with special emphasis on the timing and the size of the main hydration exotherms that strongly affect setting and early strength development of cementitious mixtures. Furthermore, a method has been developed for a more precise calculation of “thermal set”, with good correlation to manual set times according to ASTM C403. The field calorimeter is useful to screen the effect of type and dosage of admixtures and supplementary cementitious materials on “thermal” setting times in concrete and mortar.

Calorimetry at the International Linear Collider

Abstract: The physics potential of the International Linear Collider depends critically on the jet energy resolution of its detector. Detector concepts are being developed which optimize the jet energy resolution, with the aim of achieving σ jet = 30 % / E jet . Under the assumption that Particle Flow Algorithms (PFAs), which combine tracking and calorimeter information to reconstruct the energy of hadronic jets, can provide this unprecedented jet energy resolution, calorimeters with very fine granularity are being developed. After a brief introduction outlining the principles of PFAs, the current status of various calorimeter prototype construction projects and their plans for the next few years will be reviewed.

Modulated differential scanning calorimeter solvent loss calibration apparatus and method

Abstract: A modulated differential scanning calorimeter that accounts for heat flow due to evaporative solvent loss. The calorimeter modulates the temperature applied to a sample and a reference to determine the amount of heat flow that is due to evaporation. By calculating the amount of heat flow due to evaporation, the user can determine how much of the heat flow of any given well is due to the process of interest as opposed to evaporation.

Measurements of the Molar Heat Capacities and Excess Molar Heat Capacities for Acetonitrile + Diethylamine or sec-Butylamine Mixtures at Various Temperatures and Atmospheric Pressure

Abstract: As a continuation of our studies of the excess functions of binary systems containing acetonitrile (1−x)–amines (x) mixtures, the molar heat capacity, Cp, and excess molar heat capacity, Cp E, of acetonitrile + diethylamine or sec-butylamine mixtures have been determined as a function of composition at 288.15, 293.15, 298.15 and 303.15 K at atmospheric pressure using a modified 1455 PARR solution calorimeter. The excess heat capacity data are positive for both systems over the whole composition range. The experimental data on the excess molar heat capacity are discussed in terms of the influence of the magnitude of the experimental excess molar enthalpy, H E, over the curve shaped for the experimental Cp E data, molecular interactions in the mixtures, isomeric effect of the amines and modeling of Cp E data.

Measurements of Specific Heat Capacity of Gaseous R-143a Using a Flow Calorimeter

Abstract: The isobaric specific heat capacity (c p ) was measured for R-143a (1,1,1-trifluoroethane) in the gas phase. Ten measurements for R-143a were obtained at temperatures from 311 to 343 K and at pressures from 1.6 to 2.4 MPa. Some of them are close to the saturation curve. The expanded uncertainty (k = 2) of the temperature measurements is estimated to be less 25 mK, and that of the pressure measurements is less 8 kPa. The expanded uncertainty for c p is estimated to range from 9 to 32 J·kg−1·K−1. Also, the experimental data were evaluated with available equations of state.

Temperature response of a rail-cask-size pipe calorimeter in large-scale pool fires

Abstract: The Container Analysis Fire Environment (CAFE) computer code is being developed at Sandia National Laboratories (SNL) to predict the response of massive spent nuclear fuel transport casks to a range of severe fire environments. It is designed for use in transportation risk and design studies. CAFE employs physics-based reaction chemistry and radiation heat transfer models that are appropriate for fuel-rich and highly sooty pool fires. These models allow CAFE to produce accurate fire heat transfer results even when relatively coarse (and fast running) computational grids are employed. Parameters for these models must be determined from large-scale fire test data. Three fire tests were performed at the SNL outdoor fire test facility to benchmark CAFE. In these tests, the interior surface of a 2.4 m diameter, 4.6 m long, and 2.5 cm thick pipe calorimeter was instrumented with 70 Type-K thermocouples. It was suspended above a 7.2 m diameter water pool with enough JP8 jet fuel on top to burn for up to 40 minutes. Heat flux gages, directional flow probes, thermocouples, and anemometers were used to characterize the environment in the vicinity of the calorimeter during and after the fire. Transient wind conditions and calorimeter temperatures were recorded during and after the fires. The average wind speed was roughly 0.8 m/s during the first test, 1.1 m/s during the second, and 2.6 m/s during the third. CAFE simulations were performed using the measured wind conditions as boundary conditions and a range of model parameters. The resulting calculated calorimeter temperatures are compared to the experimental measurements.