ASLAF: DETECTOR OF THE DIRECT SOLAR LYMAN-ALPHA RADIATION. FUTURE ALTERNATIVES

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 10691 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 O2 concentration and temperature profiles; Possibility to study the processes in the mesosphere and low thermosphere by analysis based on the obtained profiles.


TM

Sun radiation

Ion chamberPre-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 (60V1V) and the temperature.


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

MgF2 window:• diameter = 8 mm;• sensitive to 105 – 135 nm radiation.

Quantum efficiency: 40% - 60% for 25 V – 150 V


0

2

4

6

8

10

12

0 10 20 30 40

Pressure, mb

Cur

rent

, nA

9.6 V19.2 V28.8 V38.4 V48.0 V57.6 V67.2 V76.8 V86.4 V96.0 V

V

0

2

4

6

8

10

12

0 20 40 60 80 100

Power supply, V

Cur

rent

, nA

1 mb 3 mb 6 mb 8 mb10 mb12 mb15 mb18 mb22 mb26 mb30 mb35 mb

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.


Principal scheme of the electronic amplifier

Power supply

Filterър

Ionization chamber

+60 V

IN A1 A2

K1

K2

K3

A3

A4 A5 TD

TMOut1

TMOut2

TMT

TMV

+28 V -28 V

+6 V

-6 V

+6 V

Filter

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.


ASLAF - Final design of the Lyman-alpha detector

The maximal dimensions of the device are 105x60x90 mm, its weight is 498 g.


ASLAF response of the H lamp emission

-1

0

1

2

3

4

5

6

7

0 5 10 15 20

Distance to the H lamp, cm

Sig

nal,

V

Channel 15 nAChannel 1.5 nA

y = 10.005e-1.0792x

R2 = 0.9917

y = 34.616e-0.9043x

R2 = 0.9951

0.00001

0.0001

0.001

0.01

0.1

1

10

0 2 4 6 8 10 12 14


Sig

nal,

V

Channel 1.5 nAChannel 15 nA

y = 41.652e-0.9343x

R2 = 0.997

y = 4.1073e-0.9553x

R2 = 0.9979

0.0001

0.001

0.01

0.1

1

10

0 5 10 15


Sig

nal,

V Channel 1.5 nAChannel 15 nA

• 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



y = 0.3346x + 0.0105

R2 = 1

0

1

2

3

4

5

6

0 5 10 15 20

Current, nA

Mea

sure

d vo

ltag

e, V

Channel 15 nA

y = 0.3377x + 0.0057

R2 = 0.9987

y = 3.608x + 0.0579

R2 = 0.9952

00.5

11.5

22.5

33.5

44.5

5

0 0.5 1 1.5 2

Current, nA

Mea

sure

d vo

ltag

e, V

Channel 1.5 nA

Channel 15 nA

ASLAF response to the produced electric current

• linearity

• constant signal ratio



Signal test measurements from both channels

0

1

2

3

4

5

0 5000 10000 15000 20000 25000 30000 35000

Measurement number

Cur

rent

, nA



0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0 1000 2000 3000 4000 5000 6000 7000

Measurement number

Noi

se, V

Channel 15 nA

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 1000 2000 3000 4000 5000 6000 7000

Measurement numberN

oise

, V

Channel 1.5 nA

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.


-80

-60

-40

-20

0

20

40

60

80

100

-100 -75 -50 -25 0 25 50 75 100

Angle, deg

Rel

ativ

e er

ror,

%Channel 15 nAChannel 1.5 nA

0

0.2

0.4

0.6

0.8

1

1.2

-100 -50 0 50 100

Emission angle, deg

Nor

mal

ized

sig

nal

Channel 15 nAChannel 1.5 nAFitting curve


Angular dependence of the measured signal

c

eey

bxabxa 22 )()(

Fitting curve:


Data processing and analysis

• modeling the absorption process;

• obtaining the Lyman-alpha emission profile;

• computing the O2 density, pressure and T profiles;

• comparing the obtained profiles with all other available measurements;

• analysis of the results.

Consecutive steps:



Retrieval of the density, pressure and temperature profiles

The photoabsorption cross-section σ is defined fromlneII )(

0 )()( where I0 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

i

iiTT nn )()( i

iiT )()(

– σT, nT – total cross-section and number density;– ni, σi, δi – number density, cross-section and mixing ratio for the ith component.Assuming, that O2 is the basic absorber, we can write:

)(22fOOT

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


dIIT )(

i

ii dhmngdpdh

dp

pH

11 mgkTH

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

dhfOnIdI sec)()()()( 2

the equations for nO2, p, and T can be derived.



dh

hdR

hRhOn

E

)(

)(

1

)(

cos)( 2

1

)(cos

R E RR

dRKp

)(33

)( 22 OKn

p

OKn

p

k

mgT

Basic equations to compute the density, pressure and temperature profiles:

fdI

dIE

)(

)()(

)( 2On

mngK i

ii

TT IhIR )(

Where the effective cross-section σE, the level constant K and the ratio R are expressed by


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.



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 Lα flux.

Lyman-alpha detector


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.


Thanks for

your

attentio

n!

ASLAF: DETECTOR OF THE DIRECT SOLAR LYMAN-ALPHA RADIATION. FUTURE ALTERNATIVES

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