APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

A rapid community based health evaluation of pregnant women in low socioeconomic settlements of Karachi

A rapid nutritional and health evaluation of a random sample of 163 pregnant women was conducted in low socioeconomic settlements of Karachi, with the objective of determining the morbidity and nutritional status of pregnant women. These data are expected to be used in an ongoing community-based antenatal care programme. Twenty-nine percent of women reported fever, 14 percent diarrhoea and 33 percent respiratory infections in the previous week. Mean weight was 54.8 (+/- 10.6) kg, mean height was 151.6 (+/- 6.0) cm and mean midarm circumference was 25.6 (+/- 3.2) cm. The mean uterine height at gestational ages 8 months and over was 32.1 (+/- 10.2) cm which is below the 10th percentile. These results suggest a chronic, mildly malnourished population with a high rate of infections. Specifically, we suggest that maternal height and uterine height be used to assess women at high risk for low birthweight

APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates

For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170 deg. C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2x10^4. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230/s. With these settings the studied APDs are able to detect single photons at 628 nm wavelength with a photo detection efficiency of (67+-7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio

Technical design and commissioning of the KATRIN large-volume air coil system

The KATRIN experiment is a next-generation direct neutrino mass experiment with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron neutrino. It measures the tritium $\beta$-decay spectrum close to its endpoint with a spectrometer based on the MAC-E filter technique. The $\beta$-decay electrons are guided by a magnetic field that operates in the mT range in the central spectrometer volume; it is fine-tuned by a large-volume air coil system surrounding the spectrometer vessel. The purpose of the system is to provide optimal transmission properties for signal electrons and to achieve efficient magnetic shielding against background. In this paper we describe the technical design of the air coil system, including its mechanical and electrical properties. We outline the importance of its versatile operation modes in background investigation and suppression techniques. We compare magnetic field measurements in the inner spectrometer volume during system commissioning with corresponding simulations, which allows to verify the system's functionality in fine-tuning the magnetic field configuration. This is of major importance for a successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure

The Quality of Medical Care in Low-Income Countries: From Providers to Markets

Jishnu Das provides a perspective on a research article by Paul Garner and colleagues that reports a systematic review of 80 studies comparing the quality of private versus public ambulatory health care in low and middle income countries