Study of ion feedback in multi-GEM structures

We study the feedback of positive ions in triple and quadruple Gas Electron Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain, applied voltages, number of GEMs and other parameters on ion feedback are investigated in detail. In particular, it was found that the ion feedback is independent of the gas mixture and the pressure. In the optimized multi-GEM structure, the ion feedback current can be suppressed down to 0.5% of the anode current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion feedback in multi-GEM structures is suggested. The results obtained are relevant to the performance of time projection chambers and gas photomultipliers.Comment: 9 pages, 11 figures. Submitted to Nucl. Instr. and Meth.

Self-reported symptoms of chronic cough and breathlessness in working-age men in the city of Izhevsk, Russia: associations with cardiovascular disease risk factors and comorbidities.

INTRODUCTION: Very little is known about the prevalence of respiratory symptoms or their associations with other health conditions in Russia. METHODS: Between 2008 and 2010, a sample of 983 men resident in Izhevsk, Russia, took part in a cross-sectional survey. Presence of respiratory symptoms was determined from self-report of chronic productive cough and breathlessness assessed using the British Medical Research Council (MRC) breathlessness scale. Self-reported physical and mental health were measured using the 12-Item Short-Form Health Survey (SF-12). Hypertension was assessed from mean blood pressure measured at the health check and/or self-reported use of antihypertensive medication. Other comorbidities were assessed from self-report. Logistic regression models were fitted assessing the association between respiratory symptoms and comorbidities. Linear regression models were fitted to investigate the association between respiratory symptoms and self-reported health scores. All models were adjusted for age, education and smoking status. RESULTS: The age-standardised prevalence of cough and breathlessness was 20.9% (prevalence with breathlessness MRC grade 3 or above 3.7%). The majority of men with respiratory symptoms (87.3%) were current smokers. Cough and breathlessness were associated with substantially worse self-reported physical and mental health (test for trend with severity of breathlessness p<0.001). Those with chronic cough and grade 3 or above breathlessness had higher odds of having hypertension (OR 3.03; 95% CI 1.36 to 6.74), diabetes (OR 10.55; 95% CI 2.69 to 41.37), angina pectoris (OR 7.54; 95% CI 3.61 to 15.73), previous myocardial infarction (OR 7.61; 95% CI 2.10 to 27.4) and previous stroke (OR 6.61; 95% CI 1.75 to 23.34) compared with those without respiratory symptoms. CONCLUSIONS: The prevalence of respiratory symptoms was high. Strong associations were found between respiratory symptoms and cardiovascular comorbidities. These are of particular importance given the extremely high level of cardiovascular disease mortality in Russia

A device to characterize optical fibres

ATLAS is a general purpose experiment approved for the LHC collider at CERN. An important component of the detector is the central hadronic calorimeter; for its construction more than 600,000 Wave Length Shifting (WLS) fibres (corresponding to a total length of 1,120 Km) have been used. We have built and put into operation a dedicated instrument for the measurement of light yield and attenuation length over groups of 20 fibres at a time. The overall accuracy achieved in the measurement of light yield (attenuation length) is 1.5% (3%). We also report the results obtained using this method in the quality control of a large sample of fibres.Comment: 17 pages 20 figeres submitted to NIM journa

Measurement of the KLK_L nuclear interaction length in the NaI(Tl) calorimeter

In the study of the reaction $e^+e^-\to K_{S}K_{L}$ at the VEPP-2M $e^+e^-$ collider with the SND detector the nuclear interaction length of $K_{L}$ meson in NaI(Tl) has been measured. Its value is found to be 30--50 cm in the $K_{L}$ momentum range 0.11--0.48 GeV/$c$. The results are compared with the values used in the simulation programs GEANT4 and UNIMOD.Comment: accepted in JINS

Study of the e+e−→ηγe^+e^-\to\eta\gamma process with SND detector at the VEPP-2M e+e−e^+e^- collider

In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-\to\eta\gamma$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $\rho(770)$, $\omega(783)$, $\phi(1020)$, $\rho^{\prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities \BR(\phi\to\eta\gamma), \BR(\omega\to\eta\gamma) and \BR(\rho\to\eta\gamma) were measured with the accuracies better than or comparable to the world averages.Comment: 13 pages, 6 figures, 5 table

Update of the e^+e^-\to\pi^+\pi^- cross section measured by SND detector in the energy region 400<\sqrt{s}<1000 MeV

The corrected cross section of the e^+e^-\to\pi^+\pi^- process measured in the SND experiment at the VEPP-2M e^+e^- collider is presented. The update is necessary due to a flaw in the e^+e^-\to\pi^+\pi^- and e^+e^-\to\mu^+\mu^- Monte Carlo events generators used previously in data analysis.Comment: 10 pages,7 figure