Design of a static spectropolarim imeter Bogdan Vasilescu - PowerPoint PPT Presentation

Design of a static spectropolarim imeter Bogdan Vasilescu Supervisor: Prof. Jérôme Loicq

The objective • To improve the technique for the massive stars observation ➢ Massive stars: o Masse > 10 𝑁 ⨀ o Luminosity: 10 5 − 10 6 𝑀 ⨀ (UV max.) o Masse loss rate (strong stellar winds): 10 −7 − 10 −4 𝑁 ⨀ 𝑧𝑠 −1 o 10% strong, inclined magnetic field ( ∼ ℎ𝐻 − 𝑙𝐻 ) eso.org R136a1 ∼ 256 𝑁 ⨀

The measurement Retarding plate Polarizer (modulator) (analyzer) 𝜄 Φ 𝐽 𝑗𝑜 𝐽 𝑝𝑣𝑢 𝑅 𝑗𝑜 𝑅 𝑝𝑣𝑢 𝑇 𝑗𝑜 = 𝑇 𝑝𝑣𝑢 = = 𝑁𝑇 𝑗𝑜 𝑉 𝑗𝑜 𝑉 𝑝𝑣𝑢 𝑊 𝑊 𝑗𝑜 𝑝𝑣𝑢 𝑁: the Mueller matrix of the system 𝐽 𝑝𝑣𝑢 = 𝑁 00 (𝐽 𝑗𝑜 + ℎ 1 (𝑦; 𝑢) ∙ 𝑅 𝑗𝑜 + ℎ 2 (𝑦; 𝑢) ∙ 𝑉 𝑗𝑜 + ℎ 3 (𝑦; 𝑢) ∙ 𝑊 𝑗𝑜 ) 𝑦 : spatial modulation (beam splitting) : LARGE VOLUME 𝑢: temporal modulation (rotation; piezo-elastic modulation) : FAILURE, HIGH VOLTAGE

The new principle Polarizer 𝑁𝑕𝐺 2 modulator Spectrometer 𝜄 Fast axis 2𝜊 𝜊 Incoming y ray x z O 𝑇 = [1, 0.4, 0.3, 0.5] 𝑈

Preli liminary ry study • Outgoing signal: 1 𝐽 𝑝𝑣𝑢 = 2 ( 𝐽 + 𝑅 ∙ 𝑛 𝑧, λ + 𝑉 ∙ 𝑜 𝑧, λ + 𝑊 ∙ 𝑞 𝑧, λ ) 𝐽 𝑝𝑣𝑢 = 𝑁 00 (𝐽 𝑗𝑜 + ℎ 1 (𝑦; 𝑢) ∙ 𝑅 𝑗𝑜 + ℎ 2 (𝑦; 𝑢) ∙ 𝑉 𝑗𝑜 + ℎ 3 (𝑦; 𝑢) ∙ 𝑊 𝑗𝑜 ) m 𝑧, λ = cos 2𝜄 cos(∆𝜒 2 ) n 𝑧, λ = sin 2𝜄 cos(∆𝜒 1 ) + cos 2𝜄 sin(∆𝜒 1 ) sin(∆𝜒 2 ) p 𝑧, λ = cos 2𝜄 cos ∆𝜒 1 − sin 2𝜄 sin (∆𝜒 1 )

𝑇 = [1, 0.4, 0.3, 0.5] 𝑈

Objectives Functioning in: I. Ideal conditions II. The presence of noise

Preli liminary ry results ❑ Behaviour in ideal conditions: unicity of the solution Polarizer 𝑁𝑕𝐺 2 modulator 𝜄 Fast axis 2𝜊 𝑇 1 𝜊 𝑇 y 𝑇 2 x z O

Preli liminary ry results ❑ Behaviour in simulated real conditions: SNR dependent ➢ Optimization of the analyzer (minimization of the 𝜓 2 distribution)

Preli liminary ry results ❑ Efficiency of the modulation (after Toro Iniesta, 2003)

Preli liminary ry results ❑ Behaviour in simulated real conditions: SNR dependent ➢ Relative error & standard deviation ( 𝜄 = 109 ° , 𝑇 = [1, 0.4, 0.3, 0.5] 𝑈 )

Preli liminary ry results ❑ Behaviour in simulated real conditions: oblique rays ( 𝜄 = 90 ° , 𝑇 = [1, 0.4, 0.3, 0.5] 𝑈 )

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