High speed photon-counting imager using a position sensitive diode

A new use for a 2-dimensional position sensitive diode (PSD) is described. A duolateral PSD was used with a microchannel plate image intensifier as a proof-of-concept photon counting (event driven) imager for astronomical imaging and photometry. This produced an imager capable of counting 25–30 kcps over the astronomical bands B, V & R, with an overall efficiency of ∼19%.     

Review of Acquisition and Signal Processing Methods for Electromagnetic Noise Reduction and Retrieval of Surface Nuclear Magnetic Resonance Parameters

Surveys in Geophysics - Surface nuclear magnetic resonance (sNMR) is an electromagnetic hydrogeophysical method directly sensitive to liquid phase water in the upper $$\approx $$ 100 m of the...     

Mid-Holocene lateral collapse of Antuco volcano (Chile): debris avalanche deposit features,emplacement dynamics,and impacts

Antuco (37.4°S, 71.4°W; Chile) is a dominantly basaltic stratovolcano whose original?~?3300 m altitude main cone experienced a catastrophic sector collapse at?~?7.1 cal ka BP, producing a volcanic debris avalanche deposit (VDAD) with hummocky surface and?~?6.4 km³ of volume. We carried out geological studies of its debris avalanche deposit, which was distributed to the W and displays a longitudinal facies transformation from edifice’s megablocks and block to mixed facies in distal areas (up to 25 km from the scar). Our observations support the behavior of the avalanche beginning as a translational slide, and then as plug flow when confined within the Laja River valley. Clay abundance and high content of hydrothermally altered material may suggest active participation of water; flow velocities are estimated to?~100 m s^?1. We primarily identify the steep-sided flanks of the cone, and hydrothermal alteration promoted the edifice instability, while basement seismogenic structures may have ultimately triggered the landslide. Subsequent landslide-led events include the transformation of the volcanic activity with explosive eruptions producing a sequence of dilute pyroclastic density currents (PDCs) ending?~3.4 ky BP, and extensive lava effusion rapidly reconstructing the collapsed edifice. Moreover, the Antuco VDAD also blocked the natural output of the Laja Lake, increasing its level by?~200 m and then triggering cataclysmic outburst floods by dam rupture, preserved as high-energy alluvial beds with ages between 2.8 and 1.7 ky BP. The Antuco constitutes an excellent example of a critical chain of events initiated by a stratovolcano lateral collapse and warns for detailed hazard investigations to better comprehend its related impacts.

     

Quantification of the gas mass emitted during single explosions on Stromboli with the SO2 imaging camera

We performed measurements using an SO₂ imaging camera of the SO₂ gas mass emitted during five discrete explosive events on Stromboli volcano on 3 October 2006. The SO₂ gas mass released during discrete explosions was 15–40 kg per explosion, producing 3–8% of the total daily SO₂ gas emission, demonstrating that in terms of gas flux Strombolian explosions are a second-order phenomenon compared with quiescent degassing. Using the typical gas composition measured with OP-FTIR allows us to determine the total gas mass released during an explosion as 360–960 kg with a volume of 1500–4100 m³ at 1 bar. At the probable source pressure of gas slug formation of 75 MPa this gas amount would occupy a volume equivalent to a sphere with a radius of 0.8–1 m, comparable with estimates of Stromboli's conduit geometry.