ASLAF: DETECTOR OF THE DIRECT SOLAR LYMAN- ALPHA RADIATION. FUTURE ALTERNATIVES V.Guineva(1), G.Witt(2), J.Gumbel(3), M.Khaplanov(3), R.Werner(1), J.Hedin(3), S.Neichev(4), B.Kirov(5), L.Bankov(1), P.Gramatikov(4), V.Tashev(1), K.Hauglund(6), G.Hansen(6), J.Ilstad(6), H.Wold(6) 1)Solar-Terrestrial Influences Institute (STIL), Bulgarian Academy of Sciences (BAS)Stara Zagora Department, P.O.Box 73, 6000 Stara Zagora, Bulgaria; 2)Department of Earth Sciences, The Hebrew University (HUJI), Jerusalem, Israel; 3)Atmospheric Physics Group at the Department of Meteorology (MISU), Stockholm University, S Stockholm, Sweden; 4)Space Research Institute, Bulgarian Academy of Sciences (BAS), 6 Moskovska Str., 1000 Sofia, Bulgaria; 5)Solar-Terrestrial Influences Institute (STIL), Bulgarian Academy of Sciences (BAS), Acad. Georgi Bonchev Str., Block 3, 1113 Sofia, Bulgaria; 6)Andøya Rocket Range, Andenes, Norway Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Basic scientific goal: Investigation of the processes in the mesosphere and the mesopause region by rocket measurements of the Lyman-alpha emission data. Research purposes of ASLAF Use of ASLAF instrument: for rocket measurements of the direct Lyman-alpha radiation penetrating in the atmosphere. Importance of a modern L  detector for rocket board measurements:  Acquiring the L  altitude profile and retrieval of the real O 2 concentration and temperature profiles;  Possibility to study the processes in the mesosphere and low thermosphere by analysis based on the obtained profiles. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

TM Sun radiation Ion chamber Pre-amplifier + 2-stage amplifier Power supply U, T control Data channels ASLAF Principal scheme of the L  detector - ASLAF 2 data channels, x1 (15 nA) and x10 (1.5 nA); channels to monitor the power at the chamber (60V  1V) and the temperature. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF - Ionization chamber The ionization chamber is produced by the Artech corporation. Material: copper Weight: 50 g Max diameter: 30 mm Length: 36 mm Tubule: 32 mm MgF 2 window: diameter = 8 mm; sensitive to 105 – 135 nm radiation. Quantum efficiency: 40% - 60% for 25 V – 150 V Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF - Ionization chamber Work values chosen: P = 20 mb (86% of L  are absorbed by estimation); U = 60 V; Imax = 15 nA (estimated current at the border of the atmosphere, direct Sun, Q=60%). Current through the ionization chamber, registered at different conditions – power supply and NO pressure. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Principal scheme of the electronic amplifier Sections: A1 - pre-amplifier and current-voltage converter; A2 – scaling and correcting amplifier; A3 – amplifies the signal 10 times; A4 – monitors the ionization chamber power supply; A5 – monitors the temperature. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF - Final design of the Lyman-alpha detector The maximal dimensions of the device are 105x60x90 mm, its weight is 498 g. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF response of the H lamp emission Linear signal depending on the emission intensity is obtained from both channels; The signal ratio can be considered 10.6 from 30 mV to 4.2 V in the channel 1.5 nA range. ASLAF – some characteristics Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF – some characteristics ASLAF response to the produced electric current linearity constant signal ratio Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF – some characteristics Signal test measurements from both channels Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF – some characteristics Noise measurements, internal power on The noise in the Channel 15 nA is practically zero, and the one in Channel 1.5 nA is very low, with average value of 2.6 mV, what is near the sensitivity threshold. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

ASLAF – some characteristics Angular dependence of the measured signal Fitting curve: Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Data processing and analysis modeling the absorption process; obtaining the Lyman-alpha emission profile; computing the O 2 density, pressure and T profiles; comparing the obtained profiles with all other available measurements; analysis of the results. Consecutive steps: Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Data processing and analysis Retrieval of the density, pressure and temperature profiles The photoabsorption cross-section σ is defined from where I 0 and I are the incident and transmitted intensities, n is the gas density, l is the path length and λ is the wavelength. For a mixture of gases we have – σ T, n T – total cross-section and number density; – n i, σ i, δ i – number density, cross-section and mixing ratio for the i th component. Assuming, that O 2 is the basic absorber, we can write: where f is a correction to include the absorption from other gases. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Data processing and analysis For a thin atmospheric layer with thickness dh and angle of the incident L  radiation θ the absorbed increment is: The total intensity is defined as Taking into account the pressure change across the layer, the expression for the pressure scale length H and its connection with the temperature the equations for n O2, p, and T can be derived. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Data processing and analysis Basic equations to compute the density, pressure and temperature profiles: Where the effective cross-section σ E, the level constant K and the ratio R are expressed by Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Atmospheric model and quantities, to be used in the calculations: Plane-parallel atmosphere; Upper limit at 100 km; parallel homogeneous layers; Line-by-line calculations; Measured intensity in and outside of the atmosphere and shape of the Lyman-alpha line; The rocket coordinates and the corresponding position of the Sun towards it; The photoabsorption cross-section; The solar zenith angle θ. Data processing and analysis Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

Results and conclusions.  A modern Lyman-alpha detector (ASLAF) was designed and manufactured;  ASLAF passed successfully all tests performed before a rocket start;  The detector is an ionization chamber with work characteristics p=20 mb, U=60 V;  There are two measuring channels with ranges 1.5 nA and 15 nA, characterized with linearity, constant data ratio between them and low noise signal;  The channels monitoring the power supply to the ionization chamber and the temperature work well;  The power supply to the ionization chamber remain stable, 60V, with deviations from this value less then 1V;  The device is of very good quality and can be used in rocket experiments for measuring the L α flux. Lyman-alpha detector Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

1)Preparation for taking part in future rocket experiments with ASLAF (detector of the direct solar Lyman-alpha radiation); 2)Development of a new device to register the scattered solar Lyman-alpha radiation in the atmosphere; 3)Developing Lyman-alpha detector for satellite measurements; 4)Use of other, more sensitive detectors of Lyman-alpha radiation; 5)Improvement of the signal amplification and the power supply. Future alternatives: Results and conclusions. Workshop “Solar influences on the ionosphere and magnetosphere”, Sozopol, Bulgaria, 7-13 June 2009

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