6 μm thick AlInP 55Fe X-ray photovoltaic and 63Ni betavoltaic cells

Two 400 μm diameter Al0.52In0.48P p+-i-n+ mesa photodiodes (6 μm i layer) were fabricated from a wafer grown by metalorganic vapour phase epitaxy (MOVPE) and then studied at temperatures from 140 °C to -20 °C for the development of temperature tolerant 55Fe X-ray photovoltaic and 63Ni betavoltaic microbatteries. The Al0.52In0.48P epitaxial layers are the thickest so far reported for this emerging application. At each temperature, the performances of the Al0.52In0.48P detectors were analysed in dark conditions, as well as under the illumination of a 182 MBq 55Fe radioisotope X-ray source and a 185 MBq 63Ni radioisotope source. An open circuit voltage as high as 1.13 V was found for both the Al0.52In0.48P X-ray photovoltaic cells at -20 °C; whilst an open circuit voltage of 0.47 V was found for the best 63Ni betavoltaic cell, at the same temperature. Maximum output powers of 1.44 pW and 1.36 pW were obtained from the two X-ray photovoltaic cells at -20 °C; combining the output powers of these two Al0.52In0.48P X-ray photovoltaic cells, a total maximum output power as high as 2.8 pW could be obtained at 20 °C. Maximum output powers of 0.18 pW and 0.13 pW were instead extracted from the two betavoltaic cells at -20 °C, these could lead to a total maximum output power as high as 0.3 pW at 20 °C. Conversion efficiencies of 2.2% and 0.06% were found, respectively, for the best Al0.52In0.48P X-ray photovoltaic and betavoltaic cells at -20 °C. With respect to previously reported Al0.52In0.48P X-ray photovoltaic cells with thinner i layers, the 6 μm Al0.52In0.48P X-ray photovoltaic cells had higher short circuit current, open circuit voltage, maximum output power, and conversion efficiency. The 6 μm Al0.52In0.48P betavoltaic cells instead presented similar performances to previously analysed Al0.52In0.48P betavoltaic cells

InGaP electron spectrometer for high temperature environments

In this work, a 200 μm diameter InGaP (GaInP) p+-i-n+ mesa photodiode was studied across the temperature range 100 °C to 20 °C for the development of a temperature-tolerant electron spectrometer. The depletion layer thickness of the InGaP device was 5 μm. The performance of the InGaP detector was analysed under dark conditions and then under the illumination of a 183 MBq 63Ni radioisotope beta particle source. The InGaP photodiode was connected to a custom-made low-noise charge-sensitive preamplifier to realise a particle counting electron spectrometer. Beta spectra were collected at temperatures up to 100 °C with the InGaP device reverse biased at 5 V. The spectrum accumulated at 20 °C was compared with the spectrum predicted using Monte Carlo simulations; good agreement was found between the predicted and experimental spectra. The work is of importance for the development of electron spectrometers that can be used for planetary and space science missions to environments of high temperature or extreme radiation (e.g. Mercury, Jupiter’s moon Europa, near-Sun comets), as well as terrestrial applications

Al0.2Ga0.8As X-ray photodiodes for X-ray spectroscopy

Three custom-made Al0.2Ga0.8As p-i-n mesa X-ray photodiodes (200 µm diameter, 3 µm i layer) were electrically characterised and investigated for their response to illumination with soft X-rays from an 55Fe radioisotope X-ray source (Mn Kα = 5.9 keV; Mn Kβ = 6.49 keV). The AlGaAs photodiodes were shown to be suitable for photon counting X-ray spectroscopy at room temperature. When coupled to a custom-made low-noise charge-sensitive preamplifier, a mean energy resolution (as quantified by the full width at half maximum of the 5.9 keV photopeak) of 1.24 keV was measured at room temperature. Parameters such as the depletion width (1.92 µm at 10 V), charge trapping noise (61.7 e− rms ENC at 5 V, negligible at 10 V) and the electronic noise components (known dielectric noise (63.4 e− rms), series white noise (27.7 e− rms), parallel white noise (9.5 e− rms) and 1/f series noise (2.2 e− rms) at 10 V reverse bias) affecting the achieved energy resolution were computed. The estimated charge trapping noise and mean energy resolution were compared to similar materials (e.g. Al0.8Ga0.2As) previously reported, and discussed. These results are the first demonstration of photon counting X-ray spectroscopy with Al0.2Ga0.8As reported to date

Measurement of the electron–hole pair creation energy in Al0.52In0.48P using X-ray radiation

The average energy consumed in the generation of an electron–hole pair (ε AlInP ) in Al 0.52 In 0.48 P was experimentally measured across the temperature range −20 °C to 100 ∘ C, using a custom AlInP X-ray-photodiode, an 55 Fe radioisotope X-ray source, and custom low-noise charge-sensitive preamplifier electronics. ε AlInP was found to linearly decrease with increasing temperature according to the equation ε AlInP = (-0.0033 eV/K ± 0.0003 eV/K)T + (6.31 eV ± 0.10 eV). At room temperature (20 °C), ε AlInP = 5.34 eV ± 0.07 eV

AlGaAs two by two pixel detector for electron spectroscopy in space environments

A prototype monolithic 2 × 2 square pixel Al0.2Ga0.8As p+ -i-n+mesa photodiode array (each photodiode of area 200 µm by 200 µm, with a 3 µm i layer) has been investigated for its utility as a detector for direct detection electron (β-particle) spectroscopy. Each photodiode was electrically characterised and its response to illumination from a 63Ni radioisotope β particle source was investigated at 20 °C. The percentage of electron energy absorbed in the active layer (i layer), Eabs, of the photodiode and the spectrum expected to be detected, were calculated via Monte Carlo simulations. Comparisons between the simulated and detected 63Ni β particle spectra are presented and demonstrate uniformity in response across the two by two pixel array. The percentage of electron energy absorbed in the active layer of the detector was at a maximum of 0.53 ± 0.04 for electrons with an energy of 38 keV; the percentage of electron energy absorbed in the active layer of the detector reduced to 0.29 ± 0.02 at 66 keV

Determination of the physical environment within the Chlamydia trachomatis inclusion using ion-selective ratiometric probes

Chlamydia trachomatis is an obligate intracellular bacterium with a biphasic life cycle that takes place entirely within a membrane-bound vacuole termed an inclusion. The chlamydial inclusion is non-fusogenic with endosomal or lysosomal compartments but intersects a pathway involved in transport of sphingomyelin from the Golgi apparatus to the plasma membrane. The physical conditions within the mature chlamydial inclusion are unknown. We used ratiometric imaging with membrane-permeant, ion-selective fluorescent dyes for microanalyis of the physical environment within the inclusion. Determination of H + , Na + , K + and Ca 2 + concentrations using CFDA (carboxy fluorescein diacetate) or BCECF-AM (2 ′ ,7 ′ -bis (2-carboxyethyl)-5,6-carboxyfluorescein acetoxymethyl ester, SBFI-AM, PBFI-AM and fura-PE3-acetomethoxyester (Fura-PE3-AM), respectively, indicated that all ions assayed within the lumenal space of the inclusion approximated the concentrations within the cytoplasm. Stimulation of purinergic receptors by addition of extracellular ATP triggered a dynamic Ca 2 + response that occurred simultaneously within the cytoplasm and interior of the inclusion. The chlamydial inclusion thus appears to be freely permeable to cytoplasmic ions. These results have implications for nutrient acquisition by chlamydiae and may contribute to the non-fusogenicity of the inclusion with endocytic compartments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72253/1/j.1462-5822.2002.00191.x.pd

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters