Determination of the atmospheric neutrino spectra with the Fréjus detector

The combined analysis of the final event set of data on neutrino interactions inside the detector, upward going stopping muons and horizontal muons recorded in the Fréjus experiment is presented. The absolute atmospheric neutrino spectra in the energy range for electron neutrinos and for muon neutrinos are determined. Based on the parameterization of Volkova for thev ^µ a spectral index of =2.66±0.05 is obtained from the ratio of horizontal muons over upward going stopping muons and from the measurement of the energy loss of horizontal muons inside the detector. The neutrino spectra are compared with various flux calculations. They do not show any evidence for neutrino oscillations in agreement with earlier analyses of the Fréjus data.Now atUniversity of Michigan, Ann Arbor, USA     

A search for high energy neutrinos from SN 1987A,the Carb,Hercules X-1, and Cygnus X-3 with the Fréjus detector

With the Fréjus detector we studied four astrophysical point-like sources by using \(v_e (\bar v_e )\) and \(v_\mu (\bar v_\mu )\) interactions in the detector and \(v_\mu (\bar v_\mu )\) interactions in the surrounding rock. No excess of events was found. Therefore upper limits of neutrino fluxes and source luminositics are quoted. These limits confirm results from other experiments. In addition new limits are presented for spectral indices above 3.     

Temperature and Heat Flow Calibration of A DSC-instrument in the Temperature Range Between −100 and 160°C

Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry (DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures. In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160°C. We included 9 different samples for the analysis and established some general rules for the calibration process. As a result we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about ± 3% accuracy in this temperature range. With respect to temperature calibration we find that accuracies of ±0.8°C (90% confidence) may be expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

DSC by the TGA/SDTA851e Considering Mass Changes

DSC measurements in open pans are often disturbed by mass losses such as sublimation during melting or release of water during chemical reactions. By simultaneous DSC and TG measurements the DSC signal can be corrected. For this purpose, a temperature dependent calibration function has to be determined by which the SDTA signal from the TGA/SDTA851^e measuring cell can be converted into a heat flow curve (DSC). By this procedure, accurate heat of melting can be determined despite ongoing sublimation in open pans. This method is illustrated with reference of the melting of anthracene. Additionally, condensation reactions were investigated and analyzed by DSC/TG even under ambient pressure, knowing the heat of evaporation. Using phenol formaldehyde resins the influence of the presence or the release of volatile reaction products on the reaction rate and kinetic parameters were studied. In general, the method can be used to correct DSC curves for thermal effects related to mass change. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photochemistry at high temperatures – potential of ZnO as a high temperature photocatalyst

Direct conversion of solar radiation into useful, storable and transportable chemical products is the primary goal of solar chemistry. In this paper we discuss some fundamental aspects of photochemistry at elevated temperatures. We show that luminescence can serve as an indicator of the potential use of a system as a photoconverter. As an example we present experimental data on the chemical potential and on the lifetime of the excited states of ZnO. The low luminescence quantum yield together with a lifetime of about 200 ps indicate that an efficient photochemical conversion on ZnO is highly improbable. We believe this to be a general feature of chemical systems based on a semiconductor photocatalyst, in particular of photoreactions at a solid/gas interface. Received: 18 June 1996 / Accepted: 20 September 1996     

Simultaneous measurement of irradiation,temperature and reflectivity on hot irradiated surfaces

Conversion of solar energy into chemical fuels has been a field of intense research for many years. It is usually attempted as a thermochemical reaction under highly concentrated solar irradiation, e.g. in a solar furnace. Special interest has been addressed to the question of whether concentrated light drives the reaction differently than heat. One effect of irradiation might be a decrease of the reaction temperature. To observe such an influence it is important to monitor the chemical process and the surface temperature of the sample under irradiation. In this paper we propose a method to measure the temperature, the irradiation and the reflectivity/emissivity distribution on an irradiated sample surface simultaneously. We first outline the computational background of the method and discuss its accuracy. We then report on laboratory measurements as well as on experiments performed in a solar furnace.     

Results from the Fréjus experiment on nucleon decay modes with charged leptons

Lower limits on the nucleon lifetime in channels containing at least one positron or muon are given. The analysis is based on 4 years of data taking with the Fréjus detector. Various approaches to determine the background from atmospheric neutrinos are discussed and two different nuclear models are used in event simulations. The limits obtained range from 10³¹ years forpe ⁺ K ^*0 to 1.5·10³² years forpe ⁺ K ^*0 to 1.5·10³² years forpµ ⁺ .Supported by the BMFT, FRG, under contract number 55AC14P