21 research outputs found
Scattering of thermal photons by a 46 GeV positron beam at LEP
No full textThe scattering of thermal photons present in the vacuum pipe of LEP against the high energy positron beam has been detected. Tha spectrum of the back-scattered photons is presented for a positron beam energy of 46.1 GeV. Measurements have been preformed in the interaction region 1 with the LEP-5 experiment calorimeter
PERFORMANCE OF A SCINTILLATING FIBERS SEMIPROJECTIVE ELECTROMAGNETIC CALORIMETER
No full textA highly segmented scintillating fibres/lead electromagnetic calorimeter has been tested. Each calorimeter module has semiprojective geometry and is shaped as a wedge with an angle of (0.82)degrees. The fibres are however parallel to the wedge axis and the two small lateral regions are not fibre-instrumented. This simple and cheap approach to a projective geometry allows to achieve still good energy and space resolution. Results with electrons in the range 10-100 GeV are presented
SPACE RESOLUTION OBTAINED WITH A HIGHLY SEGMENTED SCIFI EM CALORIMETER
No full textDuring the setting up of the LEP-5 experiment, we tested a longitudinal SCIFI e.m. calorimeter, having a module cross area 25 x 25 mm2 and 12.5 x 12.5 mm2 for large and small modules respectively. The results were obtained with 10 and 50 GeV electrons, and concern the impact point resolution and the transverse distribution of the e.m. shower energy inside the calorimeter
Thermal neutron radiation damage on light yield and attenuation length of scintillating fibres
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Status of the KLOE electromagnetic calorimeter: Final optimization, progress in construction and first calibration
No full textThe design and the status of construction of the KLOE electromagnetic calorimeter are described in this report. 18 out of 24 barrel modules have been fully assembled and more than 50% of the end-cap, modules are built. All experimental specifications are fulfilled as shown by the test beam results of the final size prototype. Since the quality of fibers and photomultipliers have gone through improvements, the final calorimeter performances will exceed our expectations. The main parameters of each calorimeter module (light yield, attenuation length and time resolution) are fully surveyed using cosmic rays. Extrapolating the results to electromagnetic showers, a time resolution of 55 ps/root E(GeV) and a resolution of 0.9 cm/root E(GeV) an the coordinate along the fibers are obtained. An energy resolution of 4.7%/root E(GeV) can also be quoted
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Methane oxidation over dual redox catalysts
No full textCatalytic oxidation of methane to partial oxidation products, primarily formaldehyde and C[sub 2] hydrocarbons, was found to be directed by the catalyst used. In this project, it was discovered that a moderate oxidative coupling catalyst for C[sub 2] hydrocarbons, zinc oxide, is modified by addition of small amounts of Cu and Fe dopants to yield fair yields of formaldehyde. A similar effect was observed with Cu/Sn/ZnO catalysts, and the presence of a redox Lewis acid, Fe[sup III] or Sn[sup IV], was found to be essential for the selectivity switch from C[sub 2] coupling products to formaldehyde. The principle of double doping with an oxygen activator (Cu) and the redox Lewis acid (Fe, Sn) was pursued further by synthesizing and testing the CuFe-ZSM-5 zeolite catalyst. The Cu[sup II](ion exchanged) Fe[sup III](framework)-ZSM-5 also displayed activity for formaldehyde synthesis, with space time yields exceeding 100 g/h-kg catalyst. However, the selectivity was low and earlier claims in the literature of selective oxidation of methane to methanol over CuFe-ZSM-5 were not reproduced. A new active and selective catalytic system (M=Sb,Bi,Sn)/SrO/La[sub 2]O[sub 3] has been discovered for potentially commercially attractive process for the conversion of methane to C[sub 2] hydrocarbons, (ii) a new principle has been demonstrated for selectivity switching from C[sub 2] hydrocarbon products to formaldehyde in methane oxidations over Cu,Fe-doped zinc oxide and ZSM-5, and (iii) a new approach has been initiated for using ultrafine metal dispersions for low temperature activation of methane for selective conversions. Item (iii) continues being supported by AMOCO while further developments related to items (i) and (ii) are the objective of our continued effort under the METC-AMOCO proposed joint program
The electromagnetic calorimeter of the KLOE experiment at DA Phi NE
No full textThe main aim of the KLOE experiment at DA Phi NE, the Frascati phi-factory, is to study CP violation in the K-0-(K-0) over bar system. Requirements on electromagnetic shower detection, in the 20-280 MeV/c range, are very stringent. A hermetic, lead-scintillating fiber sampling calorimeter, characterized by a fiber:lead:glue volume ratio of approximately 48:42:10, has been chosen. Energy resolution of sigma(E)/E similar to 4.7%/root E(GeV) and time resolution of sigma(T) similar to 58 ps/root E(GeV) are the most significant characteristics of this detector
