Absolute Measurements of Light Focused by a Reflector into its Focal Plane

Transcription

1 Absolute Measurements of Light Focused by a Reflector into its Focal Plane Hanna Kellermann, Markus Garczarczyk, Cornelia Schulz, Maxim Shayduk, Jürgen Hose, Razmik Mirzoyan, Masahiro Teshima

2 The MAGIC - Project

3 Major Atmospheric Gamma-ray Imaging Cherenkov - Telescopes World-largest imaging atmospheric Cherenkov telescopes (IACT) indirect observation method to detect VHE-γ rays detected light not coming directly from astronomical sources produced inside the atmosphere precise knowledge of the optical properties is important to reconstruct primary energy and to do γ-hadron separation

4 Imaging Atmospheric Cherenkov Technique Illustation by C.Fruck

5 Characterized during my diploma thesis reflector of MAGIC I reflector of MAGIC II In MAGIC II, two types of mirrors are used: all Al and glass difference between aluminum and glass mirrors

6 Measurement Setup

7 Measurement setup in detail

8 SBIG camera and optics CCD: KAF-1001E peak QE: 72% total pixels: 1.0 million array: 1024 x 1024 pixels pixel size: 24 x 24 microns SBIG camera Nikon focal length: 180mm camera aperture: F/2.8

9 Measurement technique

10 Measurement technique 13th IACTPP, H. Kellermann: Measurement of the focusing and the reflectivity of the MAGIC telescopes

11 Picture taken with the SBIG-Camera star reflected image

12 How to calculate the focused reflectivity R fok = φ indirekt φ direkt C geom. φ direkt = sum of counts in the reflection φ indirekt = sum of counts in the star C geom. = geometrical factor

13 How to calculate the focused reflectivity a little bit more detailed R fok = φ indirekt φ direkt r 2 A HSP Ω eff R Sp 1 cos Mirzoyan, et al., 2007

14 Examples for different radiation characteristics

15 How to calculate the focused reflectivity R fok = φ indirekt φ direkt r 2 A HSP Ω eff R Sp 1 cos(4. 24 ) 1.15

16 Image sections

17 Subtracting the background

18 Image sections after background subtraction φ direkt

19 Attaining the profile of the focused reflectivity 13th IACTPP, H. Kellermann: Measurement of the focusing and the reflectivity of the MAGIC telescopes

20 Example for a reflectivity profile

21 FINAL RESULTS The mirrors of MAGIC II have about the same reflectivity R Total as those of MAGIC I. But the PSF of MAGIC II is better, resulting in more light going to one pixel. The glass mirrors of MAGIC II have a higher reflectivity R Total than the alu mirrors. However, focusing is not as good and less light is collected.

22 FINAL RESULTS for more detailed information

23 Thank you for your attention!!

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25 Backup

26 Stars used for the measurements

27 Characterisatzion of the Spectralon samples Spectralon surface under the microscope Spectralon sample in the mesurement setup

28 scattering characteristics of real spectralon samples vs. ideal diffuse (Lambertian) reflector color = fits to different characterized spectralon samples black = perfect lambert reflector

29 Subtracting the background Pixel with information E CCD,k = E CCD μ 13th IACTPP, H. Kellermann: Measurement of the focusing and the reflectivity of the MAGIC telescopes

30 Subtracting the background background E CCD,k = 0 Pixel with information E CCD,k = E CCD μ

31 Angular scattering profile when laserpointer at 30 deg

32 Diffuse and specular reflection some of the reflected beams 45 diffuse reflected light surface not so diffuse, more specular reflected light some of the reflected beams surface

33 Shape of the star and the reflection

34 turnable measurement cantilever clamping tool for the Spectralon stepping motor

35 Light source light source monitoring diode laserpointer ajustibale table monitoring diode temperature sensor

36 Light detector using SI Photo diode

37 Strange behavior of the CCD chip Hintergrund probelm

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