eusoballoon
optics test in 2L configuration
EUSO-OT-INST-414-IRAP 0.1
DATE / VERSION:
16 May 2014 /
PROJECT REF :
EUSO-OT-INST-414-IRAP_V01
DOC TYPE :
short note
DOC NAME :
EUSO-OT-INST-414-IRAP_V01.doc
Prepared by
Camille Catalano, IRAP
V0.1
13.05.2014
Peter von Ballmoos, IRAP
Agreed by
Guillaume Prévôt, APC
Approved by
ARCHIVING :
Public 
DOCUMENT HANDLED IN CONFIGURATION :
14.05.2014
16.05.2014
Diffusion Limitée 
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Validated by CCM :
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
2/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
INDEXATION NOTE
KEY WORDS :
TITLE :
AUTHORS :
SUMMARY
DOCUMENT STATUS:
Volume :
Pages :
Luminaries pages:
Nb of annexes :
Language : EN
HOST SYSTEM :
CHANGE RECORD
Issue
Date
Draft 0
Modifications
Document creation
V1
11/06/2013
first version released
V2
16/10/2013
revised 2nd version / unreleased
V3
22/10/2013
third version / released
Reference documents
[RD1] EUSO-MS-INST-402-IRAP
EUSO-BALLOON Mission Specifications
[RD2] EUSO-AI-INST-251-LAL
Assembly, Integration and Tests Plan
[RD3] EUSO-DOC-AIT-253-LAL
Health Test definition document
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
3/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
Purpose and of the Document
This document addresses the instrument performance of the optical bench in the 2L
configuration (L1 and L3) - i.e. without the diffractive lens L2. The global optical efficiency opt
and the PSF are presented for a wavelength of 391 nm.
Definitions
instrumental parameters

opt
global optical efficiency (overall throughput of the optics bench)
[dimensionless]
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
1.
4/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
Configuration
The light source used is the 1 m collimator in the clean room of IRAP-Toulouse. The test
were performed the night of the 8-9 May 2014.
The light source used during this test is a "naked" 390nm LED placed at the focal point of the
collimator. The resulting 1m, collimated light beam was pointing to the optical system in order
to simulate a point source placed at infinity from the balloon (Fig 1 and 2). The incident angle
was chosen to be 3.5° (TBC Camille).
Figure 1 : photo of the configuration of the optical test
Figure 2 : diagram of the configuration of the optical test (no L2 !)
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
2.
5/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
Scan of the collimated beam
In order to measure the incident flux on L2, the collimated beam has been scanned with the
NIST (active area of 1cm2); also, the beam has been mapped with a photo camera.
On screen S2 (Fig 3, position see Fig 2), a grid pattern was placed on the aperture of
eusoballoon allowing the measurement of the power of the beam at roughly 160 positions.
This way, a map of the beam was obtained (Fig 4).
Figure 3: left - photo of the cardboard with the grid pattern for measuring scanning the flux in ~ 160 positions (grid
of 7x7 cm) ; right : photo of a white screen showing a flux distribution comparable to the results of the scan
Figure 4 : flux map of the collimated beam
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
6/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
A screen S1 which is placed in front of L1 allows to visualize the illumination of L1 via the
azurins in the paper (Fig 3).
Figure 5 : photo of screen on L1 allowing to visualize the illumination of L1 via azurins
Figure 6 : comparison of scanned map on the left(NIST, Fig 4) and intensity distribution of azurin-map (from Fig 5) on the left, please note that, just as in Fig 3, the spider and the Canon EOS are not subtracted on the figure
From the map obtained with the NIST, the beam characteristics were computed:
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
7/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
Sum of all measurements : 1444 nW (lower bound) – 1469 (upper bound)
Number of measurements : 132 (lower bound) – 146 (upper bound)
=> Average power in the beam : 10.5±0.5 nW/cm2
Area of effective light beam ): 7665 ±TBD cm2
=> Total flux in beam incident on L1 : 80494±4000TBC nW (~5% error)
Comment : The average background light (obtained by switching off the LED source) was
equal or lower to 0.05nW, 100 times lower than the lowest measurement on the beam.
Therefore, it has been ignored in this study. However, when measuring on positions that
were in the "shadow" of the direct collimator beam (such as behind the secondary mirror,
scattered/diffused light was measured at levels TBD - Camille please fill in the value)
3.
Flux distribution at the focal plane
Using the beam described in 2, the flux distribution was measured at the focal plane along an
axis perpendicular with the optical axis. The optical system was aligned with the collimated
beam with an incidence angle of ~3.5 degree (TBC Camille)
The NIST allows to measure the flux on a surface of a 1cm2. We approximate the encircled
flux at each position calculating the integrated flux on a ring of 1cm of thickness, and
summing this integrated flux with those from the inner rings.
Figure7: diagram explaining the way we approximate the encircled flux
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
8/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
Figure 8 : scan on the focal plane with the NIST (red curve is the encircled flux -> see right hand axis)
Figure 9 : scan of the focal plane with the NIST – logarithmic (red curve is the encircled flux -> see right hand axis)
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
9/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
With the flux in the collimated beam being 80494±4000 nW (TBC see above) and flux the
center cm2 24.55±TBC W, the efficiency of the optical system (defined as the fraction of the
flux collected in the cm2 centered on the focal spot) is
opt = 30.5±1.5 % (TBC).
Graphs 8 and 9 show the relatively narrow peak in the centered cm2 (containing 12 % of the
incident flux), and a lot of the incident light scattered on the entire focal plane, at least out to
11 cm from the optical axis (and probably further).
Background : The background was measured at several positions by switching off the
source. E.g. 0 cm and 2 cm from the center of the focal spot, the background light was equal
to 0.04 nW. This is 500 times lower than the weakest measurement at the position of 11 cm.
We therefore ignored the effect of the background light on our measurements.
70
l=391 nm
q=3.5° off axis
60
2-lens configuration (8/9.5.14)
encirceld flux [%]
50
40
30
3-lens configuration (1/2.5.14)
20
10
0
0
2
4
6
8
10
radius cm]
Figure 10 : comparison 3L and 2L optical bench - eff of 3L system probably slightly underestimated because of
misalignment of visible/UV beam in run of May 1/2 : estimated enhancement of +10% shown in thin gray curve - all
TBC !
eusoballoon
optics test in 2L configuration
Date : 16 May 2014
EUSO-PB-INST-411-IRAP
Version : V0.1
10/10
Prepared by : C. Catalano & PvB
Approved by : G. Prévôt
4.
CCD image and stitching with NIST profile
5.
Conclusion