Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals

Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystals recovery from such damage.Comment: 9 pages, 6 figures, LaTeX2

LED Monitoring System for the BTeV Lead Tungstate Crystal Calorimeter Prototype

We report on the performance of a monitoring system for a prototype calorimeter for the BTeV experiment that uses Lead Tungstate crystals coupled with photomultiplier tubes. The tests were carried out at the 70 GeV accelerator complex at Protvino, Russia.Comment: 12 pages, 8 figures, LaTeX2e, revised versio

Comparison of Radiation Damage in Lead Tungstate Crystals under Pion and Gamma Irradiation

Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, Protvino. The crystals were irradiated by a 40-GeV pion beam. After full recovery, the same crystals were irradiated using a $^{137}Cs$ $\gamma$-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystals light output.Comment: 10 pages, 8 figures, Latex 2e, 28.04.04 - minor grammatical change

Design and performance of LED calibration system prototype for the lead tungstate crystal calorimeter

A highly stable monitoring system based on blue and red light emitting diodes coupled to a distribution network comprised of optical fibers has been developed for an electromagnetic calorimeter that uses lead tungstate crystals readout with photomultiplier tubes. We report of the system prototype design and on the results of laboratory tests. Stability better than 0.1% (r.m.s.) has been achieved during one week of prototype operation.Comment: 10 pages, 6 figures, LaTeX2

Excitation of medium nuclei in the continuum region in inelastic scattering of deuterons

Experiments on elastic and inelastic scattering of deuterons by ¹²C, ⁴⁸Ti, ⁵⁸;⁶⁴Ni nuclei at laboratory energy of 37 MeV for angles ranging from 16° to 61° were carried out on the U-240 isochronous cyclotron of the Institute for Nuclear Research, National Academy of Science of Ukraine. A broad maximum comprising the giant resonance in the spectrum of scattered deuterons for scattering angles less than 21° is observed at the nucleus excitation energies ranging from 12 to 30 MeV. The observed maximum was theoretically described in diffraction approximation after summing the cross-section over all final nucleus states.Виконано експерименти з пружного та непружного розсіяння дейтронів ядрами ¹²C, ⁴⁸Ti, ⁵⁸;⁶⁴Ni при енергії 37 МеВ на кути від 16° до 61° на ізохронному циклотроні У-240 Інституту ядерних досліджень НАН України. В енергетичному спектрі розсіяних дейтронів для кутів розсіяння менше 21° спостерігається широкий максимум при енергіях збудження ядер від 12 до 30 МеВ, який включає в себе максимум гігантського резонансу. Широкий максимум було описано теоретично в дифракційному наближенні після підсумовування перерізу за всіма кінцевими ядерними станами.Выполнены эксперименты по упругому и неупругому рассеянию дейтронов ядрами ¹²C, ⁴⁸Ti, ⁵⁸;⁶⁴Ni при энергии 37 МэВ на углы от 16° до 61° на изохронном циклотроне У-240 Института ядерных исследований НАН Украины. В энергетическом спектре рассеянных дейтронов для углов рассеяния меньше 21° наблюдается широкий максимум при энергиях возбуждения ядер от 12 до 30 МэВ, включающий в себя максимум гигантского резонанса. Широкий максимум был описан теоретически в дифракционном приближении после суммирования сечения по всем конечным ядерным состояниям

Elastic deuteron-triton scattering AT 37MeV

Results of measurement of differential cross section of elastic scattering of deuterons by tritons at the laboratory energy of 37 MeV for the center-of-mass angles θc.m. ranging from 25° to 150° are presented. The experiment is carried out on the U-240 isochronous cyclotron of the Institute for Nuclear Research, National Academy of Science of Ukraine. Obtained experimental data is analyzed theoretically in the framework of microscopic nuclear diffraction model. Angular distributions of deuterons in a region of the main maximum (θc.m. ≤ 60° ) are described quite well at deuteron energies of 14.4, 37.0 and 39.9 MeV . An explanation of a broad secondary maximum emerging at low deuteron energies is proposed using the phenomenological quasiclassical approximation. The quasiclassical approximation allows to describe the angular distributions only qualitatively at large angles 60° < θc.m. < 150°, where the cross sections are quite small.Представлено результати вимiрювання диференцiальних перерiзiв пружного розсiяння дейтронiв з енергiєю Ed = 37, 0 МеВ на тритонах у дiапазонi кутiв розсiяння 25° ≤ θc.m. ≤ 150° . Експеримент вико- нано на iзохронному циклотронi У-240 IЯД НАН України. Проведено теоретичний аналiз отриманих експериментальних даних в межах мiкроскопiчної дифракцiйної ядерної моделi. Кутовi розподiли дей- тронiв в областi головного максимуму (θc.m. ≤ 60° ) задовiльно описуються при енергiях дейтронiв 14, 4; 37, 0 та 39, 9 МеВ. Завдяки використанню феноменологiчного квазiкласичного наближення вдалося пояснити природу появи широкого вторинного максимуму при низьких енергiях дейтронiв. Квазiкла- сичне наближення дозволяє лише якiсно описати кутовi розподiли на великих кутах 60° ≤ θc.m. ≤ 150°, де перерiзи досить малi.Представлены результаты измерений дифференциальных сечений упругого рассеяния дейтронов с энергией Ed = 37 МэВ на тритонах в диапазоне углов рассеяния 25° ≤ θc.m. ≤ 150° . Эксперимент выполнен на изохронном циклотроне У-240 ИЯИ НАН Украины. Проведен теоретический анализ по- лученных экспериментальных данных в рамках микроскопической дифракционной ядерной модели. Угловые распределения дейтронов в области главного максимума (θc.m. ≤ 60°) достаточно хорошо описываются при энергиях дейтронов 14, 4; 37, 0 та 39, 9 МэВ. Предложено с использованием феменологического квазиклассического приближения объяснение появления широкого вторичного максимума при низких энергиях дейтронов. Квазиклассическое приближение позволяет лишь качественно описать угловые распределения на больших углах 60° ≤ θc.m. ≤ 150°, где сечения уже весьма малы

Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented