MASTER THESISDevelopment and Establishment of
Performance Evaluation System
for Light Concentrators of
the Large-Sized Telescopesin the Cherenkov Telescope Array

Fiscal 2016
(Fiscal Heisei 28)
Department of Astrophysics, Major of Science
Graduate School of Science and Engineering, Ibaraki University

15NM171ADANG VIET TAN

Abstract
Master Thesis
by DANG VIET TAN

The Cherenkov Telescope Array (CTA) project is an very-high-energy gamma-ray groundbased observatory using three sizes of Imaging Atmospheric Cherenkov Telescopes (IACT)
with different diameters. By placing about 100 IACTs in the Southern and Northernhemisphere, CTA can observe the whole sky, achieve ten times the sensitivity of current
gamma-ray telescopes and expand the observable energy band from 20 GeV to 300 TeV.
There are more than 1200 researchers in 32 countries around the world participating in
CTA now. The CTA-Japan team is mainly conducting research on Large-Sized Telescopes(LSTs).
When a high energy primary particle such as gamma ray or high-energy cosmic
ray enters the Earth’s atmosphere, it will interact with nuclei in the atmosphere andgenerate a series of reactions called air shower. The generated charged particles travel
through dielectric atmosphere and cause the Cherenkov light. The CTA then observes
this Cherenkov light and detects the high energy primary particle as gamma ray or cosmic
ray. Among the IACTs of CTA project, the LSTs play an important role in observing
gamma rays in the lowest energy range from 20 GeV to 1 TeV. Because the total numberof generated Cherenkov photons is almost directly proportional to the gamma-ray energy,
the amount of Cherenkov light at low energy levels are quite low. So various factors of
LST are being studied in order to improve the light collection performance and detect
more Cherenkov light as much as possible.
In this research, we are developing the light concentrator, an important optical partwhich collects the Cherenkov light reflected from LST main mirror to camera. The LST
camera consists of 1855 photomultiplier tubes (PMT) as light detector. Each PMT has
a spherical entrance surface, which creates a gap with the adjacent PMT and loses a
lot of photons. By mounting a light concentrator in front of each PMT, this gap can be
reduced well and more Cherenkov photons can be detected. Moreover, light concentrator
also plays an important role in eliminating terrestrial background light from outside thefield of view (FOV).
The LST light concentrator has a particular structure. It is hand-made by combining
an ESR (Enhanced Specular Reflector) as reflecting material with a hexagonal cylindricalcone. In current design, the thin ESR protrudes from the entrance of cone in order to maximize the light detection surface. However, because the ESR protruding part is warped,

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the reflective surface is distorted and the measurement results showed that the performance dropped. In addition, the warped part is structurally weak. When attaching to
the interface plate, it is pushed by other adjacent light concentrators, deforms the surface
or forms a gap. In order to correct this warpage, the reinforcements by two-side tapes,
polyethylene terephthalate (PET) films and Stainless special Used Steel (SUS) films werestudied and executed. As result, the warpage was eliminated best by SUS film reinforcement, and the performance of the light concentrator was improved.
On the other hand, light concentrators are also measured the light collection efficiency carefully one by one to evaluate clearly its performance. One light concentrator
can be evaluated by 2 measurements: on-axis measurement and rotation measurement,with three light-emitting diodes (LEDs) of 310 nm, 365 nm and 465 nm in peak wavelength, respectively. The on-axis case is a fast measurement at 0◦ , while the rotationcase is a time-consuming measurement checking angle by angle from −40◦ to 40◦ . In
current experimental system, there was a problem that about 1.6% difference in the lightcollection efficiency always occurs between the measurement results of on-axis case androtation case at 0◦ . Besides, a lot of systematic errors sometimes occur during the rotation
measurement. In order to solve these problems, the experimental system was establishedentirely, namely the rearrangement, rewriting the measuring scripts, change in replacement steps and more. As result, the 1.6% difference disappeared and the systematic errors reduced well. These factors are very important and significant to evaluate correctly
the collection efficiency of light concentrator.

Acknowledgements
I would never been able to finish this research without the guidance of my professors,
help from my friends and support from my family.
Firstly, I would like to thank Professor Tatsuo Yoshida, my research supervisor, because of the infinite helps and advices he has given me. Without his support, I would nothave been able to complete this research. Secondly, my deep gratitude goes to Associate
Professor Hideaki Katagiri and Assistant Professor Akira Okumura, who gave me a lot of
useful suggestions to my research.
My sincere thanks also goes to my seniors, Doctor Mika Kagaya, Kazuhito Yoshida,
Norihito Cho, Sakiya Ono, and my friends in my laboratory for all their support.
Special thanks goes to my Vietnamese friend, Joni Pham. She is very nice helping
me to check the grammar mistakes of this thesis carefully.
Finally, thank you to all of my friends, teachers, and family for everything you havedone for me over these past six years at Ibaraki University.

vContents
Abstractiii

Acknowledgementsv

Abbreviationsix

List of Figures

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List of Tables

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1 Introduction
1.1 Cosmic ray and the significance of gamma-ray observation . . . . . . . . . . .
1.2 Gamma ray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.2 Gamma-ray production mechanisms . . . . . . . . . . . . . . . . . . . .
1.2.2.1 π0 meson decay . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.2.2 Electron bremsstrahlung . . . . . . . . . . . . . . . . . . . . .
1.2.2.3 Inverse Compton scattering . . . . . . . . . . . . . . . . . . . .
1.3 Gamma-ray detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Gamma-ray observation by IACTs . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.1 Electromagnetic cascade . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.2 Cherenkov radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.3 The principle of gamma-ray observation by IACTs . . . . . . . . . . .

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2 Cherenkov Telescope Array (CTA) project
2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 Telescope types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 Array location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Large-Sized Telescope (LST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Development of light concentrators for LST
3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 LST focal-plane camera . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2 Photomultiplier Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.3 Light concentrator (LC) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Current status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3.2.1.1 Cone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1.2 Enhanced Specular Reflector (ESR) . . . . . . . . . . . . . . .
3.2.2 Production method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3 Mass production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4 Performance evaluation system . . . . . . . . . . . . . . . . . . . . . . .
3.2.4.1 Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4.2 Relative Anode Sensitivity . . . . . . . . . . . . . . . . . . . .
3.2.4.3 On-axis measurement . . . . . . . . . . . . . . . . . . . . . . .
3.2.4.4 Rotation measurement . . . . . . . . . . . . . . . . . . . . . . .
3.2.5 Performance comparison with MST light concentrator . . . . . . . . .
3.3 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Solution and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 Reinforcement of ESR by tape . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2 Reinforcement of ESR by PET film . . . . . . . . . . . . . . . . . . . . .
3.4.3 Reinforcement of ESR by SUS film . . . . . . . . . . . . . . . . . . . . .
3.4.4 Thermostat test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.5 Final conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Establishment of performance evaluation system
4.1 Establishment of measurement system . . . . . . . . . . . . . . . . . . . . . .
4.1.1 Rearrangement and cleaning . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Additional set-up of monitor PMT . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Establishment of measurement scripts . . . . . . . . . . . . . . . . . . . . . . .
4.4 Establishment of replacement work . . . . . . . . . . . . . . . . . . . . . . . .
4.5 Establishment of rotation measurement . . . . . . . . . . . . . . . . . . . . .
4.5.1 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.2 Solution and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5 Future plan
5.1 New design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Summary85

A RAS value and standard deviation

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B RAS value correction by monitor PMT

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C RAS tables of the second and third batch

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D On-axis measurement script

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E Rotation measurement script

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Bibliography121

Abbreviations
CTA

Cherenkov Telescope Array

LST

Large-Sized Telescope

MST

Medium-Sized Telescope

SCT

Schwarzschild-Couder Telescope

SST

Small-Sized Telescope

SST-1M

Small-Sized Telescope - 1 Mirror

SST-2M

Small-Sized Telescope - 2 Mirrors

ASTRI

Astrofisica con Specchi a Tecnologia Replicante Italiana

GCT

Gamma-ray Compact Telescope

FOV

Field Of Viewix

List of Figures
1.1 Observed energy spectrum of primary cosmic rays [1]. The spectrum isexpressed by a power law from 1011 to 1020 eV with a slight change of slopesaround 1015.5 eV (knee), 1017.8 eV (second knee), and 1019 eV (ankle). . . . . .
1.2 Electromagnetic spectrum showing the gamma-ray part from the full band[2]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Spectrum difference by radiation mechanisms [3]. . . . . . . . . . . . . . . . .
1.4 Schematic diagram of π0 meson decay. . . . . . . . . . . . . . . . . . . . . . . .
1.5 Schematic diagram of electron bremsstrahlung. . . . . . . . . . . . . . . . . .
1.6 Schematic diagram of inverse Compton scattering. . . . . . . . . . . . . . . .
1.7 Fermi Gamma-ray Space Telescope [4]. . . . . . . . . . . . . . . . . . . . . . .
1.8 Top: The H.E.S.S. (High Energy Stereoscopic System) telescope array [5].
Middle: The VERITAS (Very Energetic Radiation Imaging Telescope Array System) telescope array [6]. Bottom: The MAGIC (Major AtmosphericGamma Imaging Cherenkov) telescope array [7]. . . . . . . . . . . . . . . . . .
1.9 Schematic diagram of gamma-ray shower (left) and hadronic shower (right)[8]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10 The principle of Cherenkov radiation [9]. . . . . . . . . . . . . . . . . . . . . .
1.11 Left: the light pool observed at the ground level by a γ-ray of 300 GeV[10]. Right: simulation of the Cherenkov light as a function of the impact
distance [11]. The solid and dashed lines show showers developing along to
the earth magnetic field and 90◦ perpendicular to it, respectively. . . . . . .
1.12 Illustration of an Imaging Atmosphere Cherenkov Telescope (IACT) catching Cherenkov light [10]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13 Difference in development of air showers by CORSIKA simulation [12].
Left: Gamma-ray shower development. Right: Hadronic shower development. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14 Left: Camera pixel image when observing γ-ray shower. Right: Camera
pixel image when observing hadronic shower [9]. . . . . . . . . . . . . . . . .
1.15 Stereo observation using 4 IACTs [13]. . . . . . . . . . . . . . . . . . . . . . . .
1.16 Up: Camera pixel image of each telescope when observing 1 shower using 4
IACTs. Bottom: Principle of the stereo observation using 4 IACTs [14]. . . .
2.1 CTA structure: a mixed array of different telescopes [1]. . . . . . . . . . . . .
2.2 CTA sensitivity by Monte Carlo simulation. Both northern and southernsite perform a deep sensitivity curve comparing with current arrays [1]. . .
2.3 The MST structure [1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 The SCT structure [1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 The structure of 3 SST types [1]. Left: SST-2M GCT. Middle: SST-2M ASTRI. Right: SST-1M. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1

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Abbreviations
2.6 Two sites of CTA are shown as red point [1]. . . . . . . . . . . . . . . . . . . .
2.7 The current view of northern and southern sites [1]. Up: the northern siteat La Palma, Spain, with 2 IACTs of MAGIC in operation now. Down: thesouthern site at Paranal, Chile. . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 CTA array layouts in two sites. [1] . . . . . . . . . . . . . . . . . . . . . . . . .
2.9 The LST in CTA [1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10 The LST main parameters [1]. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1
3.2
3.3
3.4

Left: LST camera. Right: PMT module equipped in camera. . . . . . . . . . .
One PMT module [15]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cross-section of photomultiplier tube [16]. . . . . . . . . . . . . . . . . . . . . .
Cherenkov light intensity and the QE curve of the R11920-100 PMT as afunction of the wavelength [17]. . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 (a): The averaged anode (red dashed) and cathode (black solid) sensitivity of
the R11920-100 PMTs versus light source position, provided by Hamamatsu
Photonics [18]. Measurements of 90 PMTs were averaged and normalized
to the position at Y = 0 mm. The insets schematically illustrate a PMT
and the definition of the curved Y axis. The value of φ= 22 mm is the exit
aperture diameter of the current light concentrator. (b): The result of PMT
incident angle dependence analysis (photon detection efficiency versus angle of incidence), measured by S.Ono [16, 18]. The measurement result ofeach PMT was normalized relative to the vertical (i.e., 0◦ ) as a reference
and corrected by cosine. The data points show measured values for eight
PMTs. The dashed line shows the average of the eight PMTs. The solid line
shows the symmetrical average (and extrapolates to 80◦ – 90◦ ). . . . . . . .
3.6 Seven PMTs of 1 module before (left) and after (right) equipping seven light
concentrators [16]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7 (a): 3D CAD model of the base ABS cone of an LST light concentrator. (b):Same as (a), but six specular ESR films are attached to the cone. (c): A light
concentrator cluster comprised of seven copies of (b) and an interface plateat the bottom [19]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8 (a) 3D CAD model of the base ABS cone of an LST light concentrator. (b)Same as (a), but six specular ESR films are attached to the cone. (c) A light
concentrator cluster comprised of seven copies of (b) and an interface plateat the bottom [19]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.9 Left: cone structure. Right: the real one [16]. . . . . . . . . . . . . . . . . . . .
3.10 The coated ERS [16]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.11 (a) The measured reflectance of bare (solid lines) and coated (dashed) ESR
films at the angle of incidence such as 20◦ , 30◦ , 40◦ , etc. (b) Same as (a)but only limited wavelength ranges are shown. The systematic uncertaintyof these measurements is estimated to be ∼ 1%, and thus some data points
are higher than 100% [19]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.12 The ERS cutting process [16]. (a): ESR is set into laser cutter. (b): The stateof ESR after cutting. (c): ESR warped greatly after removing from glass. . .
3.13 The ESR pasting process [16]. (a): cutting ESR is connected together by
Kapton tape and put into a male mold. (b): the state after holding theweight at the top. (c) Applying glue to the backside. (d) Pressing the malemold by producer’s weight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abbreviations

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3.14 Left: the view of mass-producing place. Right: Mass produced light concentrators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.15 Left: The RAS value distribution of the second batch (126 pieces - 18 clusters). Right: The state of second batch after boxed. . . . . . . . . . . . . . . . 42
3.16 Left: The RAS value distribution of the third batch (126 pieces - 18 clusters).
Right: The state of second batch after boxed. . . . . . . . . . . . . . . . . . . . 43
3.17 Schematic diagram of set-up for light concentrator. The distance from thelight source to the PMT is 2.4 m, so that the spread of light incident on PMT
is within 1◦ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.18 The performance evaluation system in real. Left: left side of dark roomwith LED at the leftmost. Right: right side of dark room with PMT andlight concentrator at the rightmost. . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.19 The performance evaluation system looking from backside. . . . . . . . . . . 45
3.20 Left: the hexagonal frame and LC. Right: LC attached into hexagonal frame. 45
3.21 The performance evaluation system. (a): Left side is the state of LED andright side is the setting state of PMT with mask in the case of step 1 (i.e.
mask case). (b): Left side is the state of LED and right side is the setting
state of PMT with light concentrator in the case of step 2 (i.e. LC case). . . . 46
3.22 Three types of LED: 310 nm, 365 nm and 465 nm. . . . . . . . . . . . . . . . 46
3.23 Schematic diagram of setup in the case of mask measurement. . . . . . . . . 47
3.24 Top line: In each graph shows 500 signals of mask case at 365 nm. Middle
line: In each graph shows the distribution of 500 signals each time. Bottom
line: In each graph shows the distribution in numerical order of counts. . . . 48
3.25 Top line: In each graph shows 500 signals of LC case at 365 nm. Middle
line: In each graph shows the distribution of 500 signals each time. Bottom
line: In each graph shows the distribution in numerical order of counts. . . . 49
3.26 The position of PMT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.27 The RAS curve (ϕ = 0◦ case). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.28 Four rotation directions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.29 The results of 4 rotation directions. . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.30 Comparison of LST and MST light concentrator at 310 nm. . . . . . . . . . . 52
3.31 Comparison of LST and MST light concentrator at 365 nm. . . . . . . . . . . 52
3.32 Comparison of LST and MST light concentrator at 465 nm. . . . . . . . . . . 53
3.33 The warpage can be seen near the entrance aperture of light concentrator. . 53
3.34 Influence of warpage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.35 The state after pasting 6 pieces of two-sided tapes on the back of 6 surfaces.
Left: 7 mm tape case. Right: 3 mm tape case. . . . . . . . . . . . . . . . . . . . 55
3.36 (a-1): The state of warpage. (a-2): The cross section of warpage floating fromthe ideal surface (dashed line). (b-1): The state after pasting 7 mm tape. (b2): The cross section of 7 mm tape case. (c-1): The state after pasting 3
mm tape. (c-2): The cross section of 3 mm tape case. (d-1): The state after
pasting 1 mm tape. (d-2): The cross section of 1 mm tape case. . . . . . . . . 56
3.37 Rotation measuring results of LC No.264, in 4 cases of tape. . . . . . . . . . . 57
3.38 Rotation measuring results of LC No.29, in only 2 cases: no tape and 3 mm
tape. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.39 Comparison of mass-produced light concentrator (left) and 3D printer prototype (right) [16]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Abbreviations
3.40 (a): Cutting PET film into a rectangular 14 mm x 26 mm. (b): Attachingglue to the back of warpage. (c): Pasting PET film to the back of warpage.
(d): The final state after reinforcement. . . . . . . . . . . . . . . . . . . . . . .
3.41 The results before and after the PET film reinforcement in the case of light
concentrator No.29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.42 The results before and after the PET film reinforcement in the case of light
concentrator No.254. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.43 Performance evaluating results of PET film vs 3 mm tape . . . . . . . . . . .
3.44 Left: the state of PET film after pasting. Right: the state of SUS film after
pasting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.45 Left: the state of warpage after PET film reinforcement. Middle: the state of
warpage after SUS 0.1 µm film reinforcement. Right: the state of warpage
after SUS 0.05 µm film reinforcement. . . . . . . . . . . . . . . . . . . . . . . .
3.46 Performance evaluation results of PET film and 2 cases of SUS film. . . . . .
3.47 Left: The dead space is created by being pressed intentionally in the casethat two sides are reinforced by SUS films. Right: A narrow dead space iscreated by being pressed intentionally in the case that two sides are reinforced by PET films. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.48 Yellow frame: the weak spaces which is not reinforced can be deformed
easily and create the dead space. . . . . . . . . . . . . . . . . . . . . . . . . . .
3.49 Thermostat test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.50 Above: all reinforcement films. From the left side are PET film, SUS 0.05
µm of 13 × 18 mm film, SUS 0.1 µm of 13 × 18 mm film, and the rightmost
one is the final SUS 0.1 µm film with rectangular shape of 13 × 26 mm. SUS
0.05 µm of 13 × 18 mm and SUS 0.1 µm of 13 × 18 mm films were used in
the SUS-film reinforcement test. Bellow: a inclined look from the side. . . .
3.51 SUS 0.1 µm film with rectangular shape of 13 × 26 mm . . . . . . . . . . . . .
3.52 Cluster with 7 new light concentrators viewed from side. . . . . . . . . . . . .
3.53 Cluster with 7 new light concentrators viewed from above. . . . . . . . . . . .
4.1 (a): before rearrangement. (b): after rearrangement. . . . . . . . . . . . . . .
4.2 (a): The monitor PMT. (b): The set-up state of monitor PMT covered by thenoise-preventing cloth. (c): The position of both PMTs. . . . . . . . . . . . . .
4.3 The experimental system after adding monitor PMT. . . . . . . . . . . . . . .
4.4 Left: Measurement PMT signal graph (above) and monitor PMT signal
graph (below) of the mask case. Right: Measurement PMT signal graph(above) and monitor PMT signal graph (below) of the LC case. . . . . . . . .
4.5 Left: results of the first confirmation test. Right: results of the second
confirmation test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6 The results of correction test. (a): The RAS value distribution of traditional
way. (b): The corrected RAS value distribution of correcting way. . . . . . .

4

58
59
59
60
60

60
61

62
62
63

64
64
64
65
68
69
69

70
70
71

Abbreviations
4.7 Screen shot when measuring the rotation case. (a): 500 pulses of each time
is displayed immediately after measuring. The above graph shows waveform of 500 pulses detected by measuring PMT. The below graph shows
waveform of 500 pulses detected by monitor PMT. Red line shows the time
range of noise pedestal (left) and pulse (right). (b): the PMT gain value
displayed when measuring so that we can check if some large systematic
errors appear. (c): the gain value of pedestal, pulse and their residual were
calculated (analysed) immediately after each time and displayed in detailon screen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Left: location of ceiling light and the experiment system. Right: the mini
bulb is turned on for replacement work . . . . . . . . . . . . . . . . . . . . . .
4.9 LED light pen wrapped in black tape to reduce light. . . . . . . . . . . . . . .
4.10 The measured results of LED light pen confirmation test. Red: PMT gain
average value fluctuation before turning off high voltage. Black: PMT gain
average value fluctuation after turning off high voltage. Green: error barsof each value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.11 The measured results of confirmation test in the case turning off voltage.
Red: PMT gain average value fluctuation before turning off high voltage.
Black: PMT gain average value fluctuation after turning off high voltage.
Green: error bars of each value. . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.12 The measured results of confirmation test in the case turning off voltage andirradiating by the LED light pen. Red: PMT gain average value fluctuation
before turning off high voltage. Black: PMT gain average value fluctuation
after turning off high voltage. Green: error bars of each value. . . . . . . . .
4.13 Measurement results of 4 times in the case of light concentrator, after theestablishment of replacement work. . . . . . . . . . . . . . . . . . . . . . . . .
4.14 Measurement results of 4 times in the case of light concentrator, after waiting 30 minutes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.15 Rotation measurement results of 4 times in the LC case of detailed test. . .
4.16 Left: rotation measurement results of 4 times in the second test of LC case.
Right: rotation measurement results of 4 times in the third test of LC case.
4.17 Left: old electrical and signal wiring before establishment, hanging a heavy
connector in the air. Right: new electrical and signal wiring system. . . . . .
4.18 Left: new electrical and signal wiring viewed from above. Right: closer look.
4.19 The measurement results after the establishment of signal cable. . . . . . .
4.20 RAS curve comparison for 2 cases of before and after the entire establishment, as black and red line respectively. . . . . . . . . . . . . . . . . . . . . . .

5

72
73
74

74

75

76
77
78
79
80
80
81
81
82

5.1 CAD view of new design of LST light concentrator. . . . . . . . . . . . . . . .

84

6.1 All light concentrators. From the left side are LC without reinforcement,
PET reinforced LC, SUS 0.05 µm LC, SUS 0.1 µm LC, final design LC (1s)and 3D printer LC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85

A.1 Left: the signal graph of mask case. Right: the signal graph of LC case. . . .

87

List of Tables
1.1 Gamma-ray bands [2]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10

2.1 Main parameters of LST, MST and SCT [1]. . . . . . . . . . . . . . . . . . . . .
2.2 Main parameters of 3 SST types [1]. . . . . . . . . . . . . . . . . . . . . . . . .

25
27

4.1 The results of on-axis case and rotation case at θ = 0◦ . . . . . . . . . . . . . .

78

C.1 The RAS value table of second batch. The ESR of No.156 was used for test.
The LCs of No.167, 178, 187, 194, 237, and 254 were left at Ibaraki University. The rest (126 pieces - 18 clusters) was sent to Spain for attachment
test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C.2 The RAS value table of third batch. The LCs of No.349, 350, 351, 352, and353 were left at Ibaraki University. The rest (126 pieces - 18 clusters) was
sent to Spain for attachment test. . . . . . . . . . . . . . . . . . . . . . . . . .

93

7

95

Chapter 1

Introduction

1.1

Cosmic ray and the significance of gamma-ray observation

Cosmic ray is an indispensable object in the current astronomy. First discovered in 1912
by Victor Hess, cosmic ray is still one of the unresolved important issues until now. Coming from the outside of Solar system, almost 90% of cosmic rays are protons, 9% arehelium nuclei and 1% nuclei are heavier elements. Before coming to Earth, cosmic rays
pass magnetic fields in space and their directions are bent, so it is difficult to identify
where they came from. Due to many experiments over the world, energy spectrum of
cosmic rays is shown as Figure 1.1 and extends beyond 1020 eV.
However, celestial high-energy sources which generate the cosmic rays also emit
high-energy gamma rays. Unlike cosmic rays, high-energy gammas rays are electricallyneutral so they can go directly through the space’s magnetic fields without any effect.
This means that high-energy gamma rays detected on Earth come directly from celestialsource where they were emitted. By observing gamma ray sources, we can study theorigin of cosmic ray and its acceleration mechanism.

9

Introduction

10

F IGURE 1.1: Observed energy spectrum of primary cosmic rays [1]. The spectrum isexpressed by a power law from 1011 to 1020 eV with a slight change of slopes around1015.5 eV (knee), 1017.8 eV (second knee), and 1019 eV (ankle).

1.2

Gamma ray

1.2.1

Overview

Gamma rays own short wavelengths about 0.01 nm and smaller, which are shorter than
X-rays in the known electromagnetic spectrum. As shown in Figure 1.2, gamma rays also
possess a wide energy range from about 100 keV (105 eV) to more than 100 EeV (1020 eV).
Table 1.1 shows the detail gamma-ray bands in very high energy astronomy. These bands
are defined by the interaction phenomena and detecting techniques.
Band
Shorthand
Range
Typical energy
Environment

Low/Medium
EnergyLE/ME
0.1-30 MeV
keV-MeVSpace

High
EnergyHE
30 MeV-100 GeV
MeV-GeVSpace

Very HighEnergyVHE
100 GeV-100 TeV
TeVGround-based

T ABLE 1.1: Gamma-ray bands [2].

Ultra HighEnergyUHE>100 TeV
PeV-EeV
Ground-based

Introduction

11

F IGURE 1.2: Electromagnetic spectrum showing the gamma-ray part from the full band
[2].

1.2.2

Gamma-ray production mechanisms

Charged particles interact in various ways in the interstellar space and perform electromagnetic radiation. In particular, gamma rays emitted by interaction with interstellar
substances indicate directly the presence of high energy particles such as cosmic rays.
Figure 1.3 shows the spectrum of radiation mechanisms. The mechanisms of π0 meson
decay, electron bremsstrahlung and inverse Compton scattering are mentioned as below,
as the main production mechanisms by which high-energy particles emit gamma rays.

F IGURE 1.3: Spectrum difference by radiation mechanisms [3].

1.2.2.1 π0 meson decay

The cosmic ray protons collide with interstellar medium (ISM) such as molecular clouds,
and generate 3 kinds of π mesons as π0 meson, π+ meson and π− meson. Among them,the π0 meson decays and emits gamma rays. Because the lifetime of π0 is very short asIntroduction

12

8.4 × 10−17 s, it almost immediately collapses to 2 gamma rays.
p cosmic_ray + p ISM → p + p + π+ + π− + π0
π0 → γ + γ

The mass of proton m p , the mass of meson m π and the kinetic energy E p of cosmic
ray proton must satisfy the following condition [?].
µ¶mπ
E p − m p c2 ≤ 2m π c2 1 += 280 [MeV]4m p

The rest energy of the π0 meson is m π c2 = 135 MeV. After collapse, 2 generated
gamma-ray photons have energy of m π c2 /2 = 67.5 MeV in the stationary system of π0
meson and fly in opposite directions to each other.

F IGURE 1.4: Schematic diagram of π0 meson decay.

1.2.2.2

Electron bremsstrahlung

When the cosmic ray electrons approach the nucleus in the ISM, their directions arebent and accelerated by the electric field. At this time, gamma rays are emitted. Thisphenomenon is called electron bremsstrahlung radiation. The bremsstrahlung radiation
spectrum is a continuously distribution in the range of 0 ≤ hν ≤ E, where E is the energyof the electron, ν is the frequency of the electromagnetic wave radiated and h is Planck’s
constant. Assuming that the surrounding substances are completely ionized, the energychange rate of relativistic electron is expressed as follows:
µ

−

¶
dE
3
=
σT cα Z(Z + 1)N[logγ + 0.36]E
dt Brems 2π(1.1)

Introduction

13

where Z is the atomic number of the nucleus, and N is the number density, σT is theThomson scattering cross section (0.665 × 10−28 m2 ), and α is the fine-structure constant(1/137).
Equation 1.1 also represents the emissivity of the electromagnetic wave, which is
proportional to the number density N. In the central part of the galaxy where the material
density is higher than that surrounding region, an expanded gamma-ray source region
has been observed. The observed energy region is from about several tens of MeV toseveral GeV. Among them, gamma rays in the low energy side (several hundreds MeV orless) are thought to mainly originate from cosmic ray electron bremsstrahlung, while in
the higher energy side are thought to be generated by π0 meson decay.

F IGURE 1.5: Schematic diagram of electron bremsstrahlung.

1.2.2.3

Inverse Compton scattering

Inverse Compton (IC) scattering is the phenomenon that relativistic electrons scatter low
energy photons and raise the photon energy up to high energy. Like the bremsstrahlung,
it is a gamma-ray radiation mechanism originating from electrons. This process is called
inverse Compton scattering because it is regarded as an inverse process of Compton scattering (a process in which the high energy photons scatter stationary electrons and turninto low energy photons). The energy change rate of electrons due to inverse Compton
scattering is expressed as follows¶
dE
4−= σT cγ2 β2Uphdt IC 3µ(1.2)

where σT , γ, β = v/c, Uph are the Thomson scattering cross section, the Lorentz factorof electron, the ratio of electron velocity to the speed of light, and the energy density of
the radiation field, respectively.

Introduction

14

F IGURE 1.6: Schematic diagram of inverse Compton scattering.

1.3

Gamma-ray detector

In different energy regions, gamma rays are detected by various ways. Gamma rays below
30 MeV are detected by Compton telescope, whereas by using artificial satellite in thehigh energy (HE) range. Since being launched into space in 2008, the Fermi Gamma-ray
Space Telescope (see Figure 1.7) has been running until now, detecting more than 3000
high energy objects. On the other hand, the incidence frequency of gamma rays ranging
from tens of GeV to TeV is low so a wider effective area is required. Because the effective
area of satellites launched into space is limited, it is difficult to observe these gamma raysby satellites. Therefore, there is a method to observe gamma rays indirectly on the groundseparately from the observation in space by using artificial satellites. When very highenergy (VHE) gamma rays arrive at the Earth, they interact with atomic nuclei in theatmosphere and generate Cherenkov light. By observing this Cherenkov light by using
Imaging Atmospheric Cherenkov Telescope (IACT) on the ground, we can reconstruct thedirections and the energies of the gamma rays arrived. There are some IACT arrays inoperation now like MAGIC, H.E.S.S. and VERITAS as shown in Figure 1.8. The largest
IACT arrays will be the Cherenkov Telescope Array (CTA) which is under construction
and will be mentioned in more detail in the next chapter.

F IGURE 1.7: Fermi Gamma-ray Space Telescope [4].

Introduction

15

F IGURE 1.8: Top: The H.E.S.S. (High Energy Stereoscopic System) telescope array [5].
Middle: The VERITAS (Very Energetic Radiation Imaging Telescope Array System) telescope array [6]. Bottom: The MAGIC (Major Atmospheric Gamma Imaging Cherenkov)
telescope array [7].

1.4Gamma-ray observation by IACTs

This section describes how gamma ray and cosmic ray go through the Earth atmosphereand how to observe gamma rays separately from cosmic-ray background.

1.4.1

Electromagnetic cascade

High energy primary particles entering the Earth’s atmosphere will generate secondary
particles by interaction with nuclei in the atmosphere. The secondary particles further
produce particles by interaction. A series of such reactions repeatedly occurred, and thecollection of particles generated is called an air shower. In the case that the primaryparticle is gamma ray, it is called electromagnetic shower, and in the case that the primaryparticle is proton, it is called hadron shower.

Introduction

16• Gamma-ray shower (Figure 1.9, left)
In the case the primary particle is high-energy gamma ray, gamma ray interacts
with atomic nuclei in the atmosphere and cause electron-positron pair production.
The generated electron and positron further emit gamma rays by bremsstrahlung,and emitted gamma rays cause electron-positron pair production again. This loop
is repeated until the energy of the emitted gamma ray falls below the energy thatelectron-positron pair production dominates (about 83 MeV due to the Earth’s atmosphere).

F IGURE 1.9: Schematic diagram of gamma-ray shower (left) and hadronic shower (right)[8].

• Hadronic shower (Figure 1.9, right)
In the case that the primary particle is high energy cosmic ray such as proton andetc, the primary particle interacts with atomic nuclei in the atmosphere and generates π0 and π± meson. The neutral pion π0 collapses into two gamma rays, andthese gamma rays cause electromagnetic shower.

1.4.2

Cherenkov radiation

When a charged particle travels through a dielectric medium, it causes the Cherenkov
radiation in the case that speed of particle exceeds the speed of light in that medium. The
electrons and positrons in the air shower generated by gamma rays or protons exceed the
speed of light c/n in the atmosphere where c is the velocity of light, n is the refractive
index of the atmosphere, and they emit Cherenkov light. Generated Cherenkov lightpossess wavelengths from the ultraviolet to visible light region. The angle θ formed by

Introduction

17

the moving direction of Cherenkov light and particle is given by the following relational
expression

θ = arccos(v
1), β =
βncwhere v is the speed of electrons and positrons.

F IGURE 1.10: The principle of Cherenkov radiation [9].

Due to that refractive index of the atmosphere changes according to the altitude,
Cherenkov light arriving at the ground level spreads like a circle of about 150 m in radius,
regardless of the altitude of air shower occurrence. This area is called a light pool. In the
Figure 1.11, the left picture shows the light pool observed at the ground level by a gamma
ray of 300 GeV. The total number of Cherenkov photons is almost proportional to theenergy of gamma ray. At 1 TeV gamma ray, the photon density on the ground in the lightpool is about 50 photons/m2 .

1.4.3

The principle of gamma-ray observation by IACTs

The IACT is composed of a main mirror as reflector and a focal-plane camera mounting
at focal point of the mirror. By placing IACT in the light pool, we can catch and collectthe Cherenkov photons reflected from mirror as shown in Figure 1.12. The amount oflight and the image of the shower are recorded as digital signals by detectors installed at
focal-plane camera.

• Distinction between gamma ray and cosmic-ray backgroundIntroduction

18

F IGURE 1.11: Left: the light pool observed at the ground level by a γ-ray of 300 GeV[10]. Right: simulation of the Cherenkov light as a function of the impact distance [11].
The solid and dashed lines show showers developing along to the earth magnetic fieldand 90◦ perpendicular to it, respectively.

F IGURE 1.12: Illustration of an Imaging Atmosphere Cherenkov Telescope (IACT) catching Cherenkov light [10].

Compared with fewer gamma ray events, the charged cosmic rays are overwhelmingly large (about 103 − 104 times) and become almost the background from theuniverse. However, because the image observed by IACT is different due to shower
development, the gamma ray can be distinguished. There are two differences inIntroduction

19

F IGURE 1.13: Difference in development of air showers by CORSIKA simulation [12].
Left: Gamma-ray shower development. Right: Hadronic shower development.

their shower developments. First, as shown in Figure 1.13, the image of gammaray shower does not spread and it develops compactly, while the image of hadronic
shower spreads anisotropically. Second, if the gamma-ray shower axis and the optical axis of the telescope match together, the image is rounded at the center of the
field of view. If it is parallel, the image appears in an ellipse whose long axis intersects the optical axis (see Figure 1.12). This feature does not exist in the caseof hadronic shower. Figure 1.14 shows the distribution of photons reaching the
focal-plane camera. The method identifying a gamma-ray shower from cosmic rays
background based on the differences in the image of Cherenkov light like this way
is called Imaging Atmosphere Cherenkov Technique (also called IACT).

F IGURE 1.14: Left: Camera pixel image when observing γ-ray shower. Right: Camera
pixel image when observing hadronic shower [9].

Introduction

20• The determination of gamma-ray energy and its arrival direction

F IGURE 1.15: Stereo observation using 4 IACTs [13].

Because the photon number density in the light pool depends on the magnitude of
the gamma ray energy arrived and it is almost constant, irrespective of the distancefrom the pool center (see Figure 1.11, right). Thus, the energy magnitude of arrival
gamma ray can be estimated by only a part of photons detected from the light pool.
The minimum energy of gamma rays that can be observed is inversely proportional
to the light collecting area of the reflecting mirror. So for 1 TeV gamma ray, about
several hundred square meters of effective area are necessary.
Besides, one method called stereo observation allows measuring the arrival direction of gamma ray more effectively. When Cherenkov light is captured at a position
distant from the shower axis, parallax occurs between the gamma ray source andthe air shower. Therefore, the shower image captured on the ground level is slightly
deviated from the direction of the source and the long axis direction of the ellipse
crosses the source direction. By observing 1 gamma-ray event by multiple telescopes
and superimposing the images, it is possible to determine the arrival direction of thesource (see Figure 1.16).

Introduction

21

F IGURE 1.16: Up: Camera pixel image of each telescope when observing 1 shower using
4 IACTs. Bottom: Principle of the stereo observation using 4 IACTs [14].

The stereo observation can be performed with at least two telescopes. However,increasing the number of telescopes will increases the number of shower images,
so the arrival direction will be predicted with higher accuracy. Moreover, since thestereo method can estimate the altitude of air shower occurrence by using the distance between the telescopes, it is possible to improve the accuracy of determining
the energy of gamma rays.

Chapter 2

Cherenkov Telescope Array (CTA)
project

2.1

Overview

F IGURE 2.1: CTA structure: a mixed array of different telescopes [1].

Cherenkov Telescope Array (CTA) project is an international plan constructing thelargest gamma-ray observatory in human history. By arranging about hundred Cherenkov
telescopes with different sizes in the northern and southern hemispheres, CTA can observe the whole universe and achieve sensitivity ten times beyond the current telescopes(see Figure 2.2), with an observable energy range from 20 GeV to 300 TeV. Figure 2.1
shows the imaging structure of CTA project using different types of IACT. With the implementation of CTA, it is expected to reach an observation of over thousand celestial
objects, bringing a new deployment to astronomical researches, such as activity of highenergy celestial objects inside and outside our Galaxy, or evolution of galaxy’s formation,
23

Cherenkov Telescope Array (CTA) project24

and so on. Currently, more than 1300 researchers from about 32 countries around theworld are participating in this project.

F IGURE 2.2: CTA sensitivity by Monte Carlo simulation. Both northern and southernsite perform a deep sensitivity curve comparing with current arrays [1].

2.1.1

Telescope types

There are 4 classes of IACT designed for CTA. They are composed of Large-Sized Telescope (LST), Medium-Sized Telescope (MST), Schwarzschild-Couder Telescope (SCT) andSmall-Sized Telescope (SST). Each types of telescope has been developed by an international collaboration.

• Large-Sized Telescope (LST)The LST will be described in more detail in the next section.
• Medium-Sized Telescope (MST)The MST is a modified Davies-Cotton telescope using 90 hexagonal segmented mirrors as one primary mirror as shown in Figure 2.3. This primary mirror possesses
a diameter of 12 m and a focal length of 16 m (see Table 2.1). MST is an importantpart of CTA covering the core energy range from 100 GeV to 10 TeV with a large
Field Of View (FOV) of 8◦ . Two types of camera: NectarCAM and FlashCAM will be
used for MST.

Cherenkov Telescope Array (CTA) project25

F IGURE 2.3: The MST structure [1].

• Schwarzschild-Couder Telescope (SCT)As shown in Figure 2.4, the SCT is a dual mirror version of MST developed by institutes in the United States since 2006. Figure 2.4 shows the structure of SCT. The
2-mirror optical system is designed to cancel aberrations and de-magnify the image of Cherenkov light. Moreover, SCT is equipped with a compact, high-resolution
camera. The SCT cover the same energy range with MST, from 100 GeV to 10 TeV
with a wider FOV of 8.3◦ . Some main parameters of SCT are shown in Table 2.1.
Type

LST

MST

SCT

Reflector type
Focal length
Dish diameter(primary)
Mirror effective area
Camera FOV
Energy range

Parapolic
28 m
23 m

Davies-Cotton
16 m
12 m

Schwarzschild-Couder
5.6 m
9.7 m

368 m2
4.5◦
20 TeV-1 TeV>88 m2
8◦

40 m2
8.3◦
100 GeV-10 TeV

T ABLE 2.1: Main parameters of LST, MST and SCT [1].

• Small-Sized Telescope (SST)Cherenkov Telescope Array (CTA) project26

F IGURE 2.4: The SCT structure [1].

There are 3 different types of SST being considered: 1 single-mirror design (SST1M) and 2 dual-mirror designs (SST-2M ASTRI and SST-2M GCT), as shown in
Figure 2.5. A mixture of these types could be expected to be used in CTA, covering
the highest energy range from 10 TeV to 300 TeV. Table 2.2 shows more detail aboutmain parameters of these SST types.

F IGURE 2.5: The structure of 3 SST types [1]. Left: SST-2M GCT. Middle: SST-2M
ASTRI. Right: SST-1M.

Cherenkov Telescope Array (CTA) project

27

Type

SST-2M ASTRI

SST
SST-2M GCT

Reflector type
Focal length
Dish diameter(primary)
Mirror effective area
Camera FOV
Energy range

Schwarzschild-Couder
2.15 m4m

Schwarzschild-Couder
2.28 m
4m

6 m2
9.6◦

6 m2
9.2◦
1 TeV-300 TeV

SST-1M
Davies-Cotton
5.6 m
4m
6.47 m2
9.1◦

T ABLE 2.2: Main parameters of 3 SST types [1].

2.1.2

Array location

In July 2015, two sites of CTA in southern and northern hemispheres was decided for
Paranal in Chile and La Palma in Spain respectively (see Figure 2.6). Figure 2.7 shows
the current view of 2 sites. At both places there are other telescopes already in operation.

F IGURE 2.6: Two sites of CTA are shown as red point [1].

The telescope arrangement is optimized by simulation by the Monte Carlo group of
CTA. As the baseline arrays, 4 LSTs and 15 MSTs for the north site, 4 LSTs, 25 MSTs
and 70 SSTs for the south site will be arranged as shown in Figure 2.8 . Based on basic research so far, we are now advancing the manufacture, assembly and performance
evaluation of each part toward the construction of first prototype. The development andCherenkov Telescope Array (CTA) project28

F IGURE 2.7: The current view of northern and southern sites [1]. Up: the northern siteat La Palma, Spain, with 2 IACTs of MAGIC in operation now. Down: the southern site
at Paranal, Chile.

construction are progressing for the purpose of full observation in 2021, and then observation of whole sky for about 20 years.

F IGURE 2.8: CTA array layouts in two sites. [1]2.2

Large-Sized Telescope (LST)The Large-Sized Telescope is an alt-azimuth telescope possessing a parabolic reflective
surface. Figure 2.9 shows the whole structure of LST. The main mirror of LST consist of
198 hexagonal segmented mirrors. The diameter of primary mirror is up to 23 m, givinga large effective area of 400 m2 , 2 times of MAGIC telescope. Although the LST stands 45

Cherenkov Telescope Array (CTA) project29

m tall and weighs about 103 tonnes, it can be possible to re-position quickly within only
20 seconds. Figure 2.10 shows all information about LST main parameters.

F IGURE 2.9: The LST in CTA [1].

The target energy range of LST is from 20 GeV to 1 TeV, covering the current observation energy range of Fermi. The observation by LSTs will improve the studies ofgalactic transient, high red-shift active galactic nuclei and gamma ray bursts.
The first LST prototype is now under construction in La Palma, Spain and will befinished until mid-2017. Its operation will verify all the parameters comparing to thesimulation results.

• The role of CTA-Japan groupCherenkov Telescope Array (CTA) project30

F IGURE 2.10: The LST main parameters [1].

The LST is studied by an international collaboration of institutes and universities
from Brazil, France, Germany, India, Italy, Japan, Spain and Sweden. However,
CTA-Japan group has been playing an important leadership role, promoting research and development of LST. In particular, Japan group makes a significant contribution in supporting optical system and segmented mirrors, and in developing
the focal-plane camera. Concretely, the total number of LST segmented mirrors to
be constructed in the north and south sites is about 1600, but almost all of themare produced by CTA-Japan. Moreover, the Japan group also undertakes the development of Active Mirror Control (AMC), which is a mechanism controlling eachsegmented mirror individually, in order to support the optical system. Along withthe development of optical system, the development of a focal-plane camera that
detects the focused Cherenkov light and records shower image as electric signals is
also an important object of Japan group.

This thesis describes in detail the current status of LST light concentrator, an important optical part of LST camera. The main content includes 2 part: the LST lightCherenkov Telescope Array (CTA) project

31

concentrator development and the establishment of its performance evaluation system at
Ibaraki university.

Chapter 3

Development of light
concentrators for LST

3.1

Overview

3.1.1

LST focal-plane camera

The LST camera has a hexagonal shape and weighs less than 2 tons (see Figure 3.1, left).
Its focal plane is composed of 1855 Photomultiplier Tubes (PMT) divided into 265 PMT
modules (i.e. PMT cluster). One module consists of 1 readout circuit, power supplying
part, 7 PMTs, and 7 light concentrators (see Figure 3.2). The calibration test of 2000
PMTs for the first LST prototype has already done and they are being shipped to La
Palma by boat at this time. Besides, an efficient cooling system for entire camera is also
developed by CTA-Japan group.

F IGURE 3.1: Left: LST camera. Right: PMT module equipped in camera.

33

Development of light concentrator for LST

34

F IGURE 3.2: One PMT module [15].

3.1.2

Photomultiplier Tube

Photomultiplier Tube (PMT) is used in LST camera as a light detector. It is a vacuum tube
using photoelectric effect to change incident photon to electric current. Figure 3.3 shows
the PMT structure. Basically, it is composed of a light input window, a phototelectron
emissive surface (photocathode), an electron multiplier (dynode) and an anode. Whena photon comes into the window, a photoelectron will be emitted probabilistically andbe multiplied 4 × 104 times overall. This probability is called Quantum Efficiency (QE).
Detected photon number depends on the QE of PMT, meaning that if the QE is low, there
is a large loss of detected photons.

F IGURE 3.3: Cross-section of photomultiplier tube [16].

LST photomultiplier tube is a photosensitive device named R11920-100, which isDevelopment of light concentrator for LST

35developed by both CTA Japan group and Hamamatsu Photonics K.K. This PMT is optimized for detecting the wavelength range from 290 nm to 600 nm, with the best QE at 350
nm wavelength. This wavelength has the strongest intensity that can observe Cherenkov
light on the ground. Figure 3.4 shows the Cherenkov light intensity and the QE curveof the R11920-100 PMT as a function of the wavelength. Figure 3.5 shows the averaged
anode (red dashed) and cathode (black solid) sensitivity of the R11920-100 PMTs versus light source position (a), and the result of PMT incident angle dependence analysis
measured by S.Ono (b). Moreover, the light input window of this PMT series is frosted
to increase a few percent of QE. Because the camera’s diameter is very large up to 2 m,using totally 1855 PMTs so a few percent up is also important for telescope performance.

F IGURE 3.4: Cherenkov light intensity and the QE curve of the R11920-100 PMT as afunction of the wavelength [17].

3.1.3Light concentrator (LC)Light concentrator (LC) is an optical instrument which is usually put in front of the lightsensor of focal-plane camera. LST focal-plane camera is made by 1855 PMTs and 1 PMT
will be equipped by 1 light concentrator. As shown in Figure 3.6, because the PMT iscylindrical, a gap called “dead space” occurs among PMTs when aligning them side-byside. This gap will decrease the detected light coming from primary mirror to camera
focal plane. Therefore, light concentrator is put in front of the PMT to minimize deadspace, increase thoroughly the reflected light into PMT. On the other hand, there is one
more use of light concentrator that decreases the stray light from the Earth’s background.

Development of light concentrator for LST

36

F IGURE 3.5: (a): The averaged anode (red dashed) and cathode (black solid) sensitivityof the R11920-100 PMTs versus light source position, provided by Hamamatsu Photonics[18]. Measurements of 90 PMTs were averaged and normalized to the position at Y = 0
mm. The insets schematically illustrate a PMT and the definition of the curved Y axis.
The value of φ= 22 mm is the exit aperture diameter of the current light concentrator.
(b): The result of PMT incident angle dependence analysis (photon detection efficiency
versus angle of incidence), measured by S.Ono [16, 18]. The measurement result ofeach PMT was normalized relative to the vertical (i.e., 0◦ ) as a reference and correctedby cosine. The data points show measured values for eight PMTs. The dashed line
shows the average of the eight PMTs. The solid line shows the symmetrical average (andextrapolates to 80◦ – 90◦ ).

3.2

Current status

The light concentrator of LST has been being developed by K.Kuroda, S.Tanaka and S.Ono
with the help of Assistant Professor A.Okumura, Associate Professor H.Katagiri, andProfessor T.Yoshida from 2009. The last design was approved last year (2015). In thissection is described the current status of the LST light concentrator based on Sakiya
Ono’s previous research [15].

3.2.1

DesignThe first design of light concentrator was initiated by Winston, under the name "Winston
cone". However, it is not clear that this design of Winston cone is best suited for LST, so
the optimization was required. The inner curved surface of light concentrator which basedon Winston cone was optimized with quadratic Bézier curve by A.Okumura [19]. The last
design was approved last year (2015) with the shape of hexagonal cylinder as shown inDevelopment of light concentrator for LST

37

F IGURE 3.6: Seven PMTs of 1 module before (left) and after (right) equipping seven light
concentrators [16].

Figure 3.7, consistent with the honeycomb arrangement of PMTs. The final design is
a combination of ABS plastic cone and Enhanced Specular Reflector (ESR). Figure 3.8
shows the structure and the real one. The cone and ESR are specifically described asfollows.

F IGURE 3.7: (a): 3D CAD model of the base ABS cone of an LST light concentrator. (b):Same as (a), but six specular ESR films are attached to the cone. (c): A light concentrator
cluster comprised of seven copies of (b) and an interface plate at the bottom [19].

3.2.1.1

Cone

The cone has a shape like a hexagonal cylinder, is made of plastic and manufactured inlarge quantity by injection molding technology. The model for injection molding was commissioned to Proto Labs G.K. (Japan). The shape of exit aperture is fitted to the sphericalDevelopment of light concentrator for LST

38

F IGURE 3.8: (a) 3D CAD model of the base ABS cone of an LST light concentrator. (b)Same as (a), but six specular ESR films are attached to the cone. (c) A light concentrator
cluster comprised of seven copies of (b) and an interface plate at the bottom [19].

entrance surface of PMT, so that the PMT can "sink into" the concentrator without gap orlight leakage. Figure 3.9 shows the cone structure (left) and the real one (right).

3.2.1.2

Enhanced Specular Reflector (ESR)The Enhanced Specular Reflector (ESR) is originally made to reflect visible light and reacts well in the wavelength range from 400 nm to 800 nm. In order to observe Cherenkov
light, it is necessary to coat the ESR to 300 nm in the UV band. This work was commissioned to Bte GmbH German company dealing with the coating processing and opticalproducts. ESR is pasted on glass with Kapton tape and its surface was coated with 54
layers of SiO2 and Ta2 O5 alternately by vapor deposition (see Figure 3.10). The performance of bare and coated ESR is shown in Figure 3.11.
The ESR is designed to protrude from the cone at the entrance of light concentrator
as shown in Figure 3.7 (b). Since the minimum thickness of the cone is 0.5 mm, so if thecone comes to the tip, the corresponding dead space will be generated. Specifically, thedetected area decreases by 4%. This area should be thoroughly reduced, so it was decided
that ESR comes to the tip instead of cone, in order to detect the light reflected at the
cut-off angle 25.8◦ as much as possible.

Development of light concentrator for LST

39

F IGURE 3.9: Left: cone structure. Right: the real one [16].

3.2.2

Production method

The production method of light concentrator was confirmed by S.Ono [16]. It is a handmade method by 3 steps as follows.

• Cutting ESR: The ESR coated by Bte GmbH was delivered to Ibaraki university asa state attached on glass by Kapton tape (see Figure 3.10). The ESR is then cut bylaser cutter along a ESR cutting drawing. As shown in Figure 3.12 (b), this cutting
drawing is consist of 6 pieces for all 6 surfaces of light concentrator, connecting
together only by a tip of 2.2 mm. When the ESR was removed from the glass, itwarped greatly as shown in Figure 3.12 (c).
• Pasting ESR to cone: After cut, 2 edges of cutting ESR are connected together by
Kapton tape and put into a male mold (see Figure 3.13 (a)). Six surfaces of cutting
ESR are hold by a weight at the top of male mold and applied glue to the backside(see Figure 3.13 (b), (c)), and thence covered by plastic cone. The whole setting moldis turned over and pressed by producer’s weight.

Development of light concentrator for LST

40

F IGURE 3.10: The coated ERS [16].

F IGURE 3.11: (a) The measured reflectance of bare (solid lines) and coated (dashed) ESR
films at the angle of incidence such as 20◦ , 30◦ , 40◦ , etc. (b) Same as (a) but only limited
wavelength ranges are shown. The systematic uncertainty of these measurements is
estimated to be ∼ 1%, and thus some data points are higher than 100% [19].

• Checking leaked glue and cleaning:

Leaked glue among 6 ESR surfaces ischecked by eyes and wiped with a pointed cotton swab. Thus, the inner surface iswiped carefully with lens cleaning paper and lens cleaning liquid.

Development of light concentrator for LST

41

F IGURE 3.12: The ERS cutting process [16]. (a): ESR is set into laser cutter. (b): The
state of ESR after cutting. (c): ESR warped greatly after removing from glass.

F IGURE 3.13: The ESR pasting process [16]. (a): cutting ESR is connected together by
Kapton tape and put into a male mold. (b): the state after holding the weight at the top.
(c) Applying glue to the backside. (d) Pressing the male mold by producer’s weight.

3.2.3

Mass production

Mass production was started from November 2015. The manufacturing was done by
Ibaraki University students, under the direction and management of S.Ono and me. Figure 3.14 left shows the mass-producing place at Ibaraki University. About 900 pieces havebeen produced here. The completed light concentrators were contained in paper cups one
by one, wrapped to preserve from dust (see Figure 3.14, right). Besides, their conditionand performance were also checked carefully. Those in bad condition will be fixed or used
for testing.

Development of light concentrator for LST

42

F IGURE 3.14: Left: the view of mass-producing place. Right: Mass produced light concentrators.

About 400 pieces of completed light concentrators has been evaluated and divided
into 3 batches. The first batch (150 pieces) was measured by S.Ono and sent to the Institute for Cosmic Ray Research (ICRR), University of Tokyo, for mini camera test. The
second and third batches (252 pieces - 36 clusters) were measured by me, then sent toSpain for attachment test. Figure 3.15 and 3.16 show the RAS value distribution of thesecond and third batch evaluated with LED 365 nm. The average value of RAS of second
and third batch was 84.5% ± 1.66% and 85.1% ± 1.55% respectively. The checked light
concentrators are boxed (see Figure 3.15 and 3.16 right), and sent by the shipping company Akabou. The box was also wrapped in blanket in order to avoid shock. The rest oflight concentrators has been stored at Ibaraki University.

F IGURE 3.15: Left: The RAS value distribution of the second batch (126 pieces - 18
clusters). Right: The state of second batch after boxed.

Development of light concentrator for LST

43

F IGURE 3.16: Left: The RAS value distribution of the third batch (126 pieces - 18 clusters). Right: The state of second batch after boxed.

3.2.4

Performance evaluation system

3.2.4.1

Set-up

The performance of light concentrator is evaluated by an optical measurement system inthe darkroom. Figure 3.17 and 3.18 show respectively the schematic diagram and thereal status of performance evaluation system for light concentrator. The experimental
set-up is mounted on an optical table, attached on rails. The system consists mainly of arotation machine, PMT, concentrator, LED, DRS4, pulse generator, and voltage supplier.
PMT and light concentrator are placed on a rotation stage. Figure 3.19 shows the performance evaluation system looking from backside. When measuring, the light concentrator
is attached in a hexagonal frame designed by S.Ono (see Figure 3.20), and pushed by the
PMT from behind. The LED is installed 2.4 m away from the position of light concentrator and emits pulse. The spread of light incident on PMT is then within 1◦ based on the
distance of 2.4 m. As shown in Figure 3.22, three types of light-emitting diodes (LEDs)of 310 nm, 365 nm and 465 nm in peak wavelength are used (mainly 365 nm). A black
curtain was hung between LG and PMT to prevent light reflected on the ceiling and wallof the darkroom. A rectangular hole of about 17 × 26 cm is opened in the middle of thecurtain, letting light pulses pass through.

3.2.4.2

Relative Anode Sensitivity

Ordinarily, the collection efficiency (CE) is used to evaluate the performance of light concentrator. The CE of 1 concentrator means how much it can collect the light. The CE is afunction of the incident angle, calculated by the ratio of the amount of light entering theDevelopment of light concentrator for LST

44

F IGURE 3.17: Schematic diagram of set-up for light concentrator. The distance from thelight source to the PMT is 2.4 m, so that the spread of light incident on PMT is within
1◦ .

F IGURE 3.18: The performance evaluation system in real. Left: left side of dark roomwith LED at the leftmost. Right: right side of dark room with PMT and light concentrator at the rightmost.

entrance aperture of the concentrator and the amount of light leaving the exit apertureas follows

CE(θ ) =amount_of_light_exiting_the_LC(θ ).
amount_of_light_entering_the_LC(θ )(3.1)

However, these two quantities can not be measured simultaneously. Therefore, theformula 3.1 is in fact calculated by measuring at the entrance and at the exit separately.
The measurement is executed in two steps as follows.

Development of light concentrator for LST

45

F IGURE 3.19: The performance evaluation system looking from backside.

F IGURE 3.20: Left: the hexagonal frame and LC. Right: LC attached into hexagonalframe.

• Step 1 (mask case): The PMT is placed on the rotation stage so that the entrance
surface is tangent to the position of the LC entrance aperture. Figure 3.21 (a) and3.23 show respectively the real status and the schematic diagram of mask case. The
PMT is then masked with the hexagonal mask whose area is equal to the area ofexit aperture. The amount of light recorded by this measurement will be multipliedby the area ratio between the mask hole and the entrance aperture and the cosineof the incident angle θ . The result of this calculation is the amount of light thatenters into the concentrator as a function of the incident angle θ :amount_of_light_entering_the_LC(θ ) = PMT_value_at_entrance(0◦ )×S pixelS mask×cos(θ ).

(3.2)
where PMT_value_at_entrance(0) is the output value of PMT at incident angle 0◦Development of light concentrator for LST

46

F IGURE 3.21: The performance evaluation system. (a): Left side is the state of LED andright side is the setting state of PMT with mask in the case of step 1 (i.e. mask case).
(b): Left side is the state of LED and right side is the setting state of PMT with light
concentrator in the case of step 2 (i.e. LC case).

F IGURE 3.22: Three types of LED: 310 nm, 365 nm and 465 nm.

when hexagonal mask is attached, S mask is the area of hexagonal hole of mask , andS pixel is the area of LC entrance aperture, i.e. LST camera pixel. Based on previous1
is about 3.7352.
research, SSmask
pixel• Step 2 (LC case): The light concentrator is placed on the rotation stage and the
PMT is then attached to the exit aperture of the concentrator (see Figure 3.21 (b)).
After that, the rotation stage is rotated to the angle θ and the amount of light exits

Development of light concentrator for LST

47

F IGURE 3.23: Schematic diagram of setup in the case of mask measurement.

the concentrator is recorded as:

amount_of_light_exiting_the_LC(θ ) = PMT_value_at_exit(θ )(3.3)

where PMT_value_at_exit(θ ) is the output value of PMT at incident angle θ degree
when light concentrator is attached.

By substituting Equation 3.2 and 3.3 into Equation 3.1, we define the Relative AnodeSensitivity (RAS) as a new quantity for evaluating performance of light concentrator as
follows:

RAS(θ ) =3.2.4.3

S mask1
PMT_value_at_exit(θ )××× 100%.
PMT_value_at_entrance(0) S pixel cos θ(3.4)

On-axis measurement

The on-axis measurement is a procedure measuring only the RAS of each light concentrator at θ = 0◦ . The on-axis measurement is consist of 2 steps as follows. Step 1 and 2 canbe swapped for each other.

Development of light concentrator for LST

48• Step 1: First, the measuring person enters the dark room, turns on the mini bulb,
attaches the mask on PMT, turns off the mini bulb, then leaves and closes the darkroom. The measuring person runs the measurement script (see Appendix D) andthe amount of light at entrance aperture is measured.
The measurement is subdivided into 4 times, each consisting of 500 pulses. The
integral of each pulse is calculated, minus the pedestal part and filled in a graph.
Then, the average of 500 pulses and its statistical error for each time are calculated
from this graph as xm_ i ± σm_ i (i=0,1,2,3 for 4 times). The average value xm ± εm of
4 times will be the final value of mask case with
P3

xm =

i =0 xm_ i

4
sP

εm =

,

3
2
i =0 (xm_ i − xm )4,

where εm is known as standard deviation. The detailed calculations are describedin Appendix A. Figure 3.24 shows an example of mask case results.

F IGURE 3.24: Top line: In each graph shows 500 signals of mask case at 365 nm. Middle
line: In each graph shows the distribution of 500 signals each time. Bottom line: In eachgraph shows the distribution in numerical order of counts.

• Step 2: After that, the measuring person enters the dark room again, turns on
the mini bulb, replaces mask by light concentrator, turns off the mini bulb, thenleaves and closes the dark room. Finally, the measuring person runs the samemeasurement script and the amount of light at the exit aperture is measured asDevelopment of light concentrator for LST49xLC_ i ± σLC_ i (i=0,1,2,3 for 4 times). As same as mask case, the average of 4 times iscalculated as the final value of LC case as xLC_ i ± εLC withP3

i =0 xLC_ i

xLC =

4

,

sP
εLC =

3
2
i =0 (xLC_ i − xLC )4,

where εLC is known as standard deviation.
The measured values are analyzed by an analysis script based on Equation 3.4, andthe RAS value is calculated as RAS(0◦ ) ± εRAS(0◦ ) with
RAS(0◦ ) =1
xLC
×× 100 %,
xm 3.7352

εRAS(0◦ ) = RAS(0◦ ) ×

s
µ

¶
εLC 2

xLC

µ

+

¶
εm 2

xm

(3.5)

,

where εRAS(0◦ ) is known as entire standard deviation. Figure 3.25 shows an example
of LC case results.

F IGURE 3.25: Top line: In each graph shows 500 signals of LC case at 365 nm. Middle
line: In each graph shows the distribution of 500 signals each time. Bottom line: In eachgraph shows the distribution in numerical order of counts.

Development of light concentrator for LST
3.2.4.4

50

Rotation measurement

The rotation measurement is a procedure measuring the RAS curve of each light concentrator as a function of incident angle. The rotation measurement is consist of 2 steps asfollows.

• Step 1: First, the measuring person enters the dark room, turns on the mini bulb,
attaches the mask on PMT, turns off the mini bulb, then leaves and closes the darkroom. The measuring person runs the measurement script (see Appendix D) andthe amount of light at entrance aperture is measured.
• Step 2: After that, the measuring person enters the dark room again, turns on themini bulb, replaced mask by light concentrator, turns off the mini bulb, then leaves
and closes the dark room. Finally, the measuring person runs another measurement
script for the rotation (see Appendix E). Based on this script, the system is rotated tothe angle of −40◦ first, and then the amount of light at the exit aperture is measured
by the step of 1◦ (0.5◦ in the range of [−30◦ , −20◦ ] and [20◦ , 30◦ ]). Figure 3.26 shows
the position of PMT at −40◦ , 0◦ and 40◦ . The first time the system is turned from−40◦ to 40◦ , the second time from 40◦ to −40◦ inversely, the third time from −40◦ to

40◦ and the fourth time from 40◦ to −40◦ , each time consisting of 500 pulses at eachangle. The average of 4 times is calculated as the final value of light concentrator
at respective incident angle. The total time for this measurement is about 1 hour
and a half. The RAS value at each θ is calculated as RAS(θ ) ± εRAS(θ) and stored in
ROOT files, with
1
xLC
×× 100 %,xmcos(θ ) × 3.7352
s
µ
¶ µ
¶
εLC 2
εm 2
εRAS(θ) = RAS(θ ) ×
+
,
xLC
xm

RAS(θ ) =where εRAS(θ) is known as entire standard deviation at θ . Figure 3.27 shows the
RAS curve sample of 1 light concentrator.

Moreover, 4 rotation directions as shown in Figure 3.28 are measured for each LC.
The case of ϕ = 0◦ is usually measured as the main in both on-axis and rotation measurement. Figure 3.29 shows the results of 4 rotation directions.

Development of light concentrator for LST

51

F IGURE 3.26: The position of PMT.

F IGURE 3.27: The RAS curve (ϕ = 0◦ case).

F IGURE 3.28: Four rotation directions.

3.2.5

Performance comparison with MST light concentrator

Professor A.Okumura brought some samples of MST light concentrator from Europe.
Their reflectivity was measured, and the highest one was used to perform the rotation
measurement and compared with LST light concentrator performance in three cases of
310 nm, 365 nm and 465 nm. These results are shown in Figure 3.30, 3.31 and 3.32

Development of light concentrator for LST

52

F IGURE 3.29: The results of 4 rotation directions.

respectively. The rotation measuring results of LST light concentrator No.29 in the firstbatch are used in this comparison.

F IGURE 3.30: Comparison of LST and MST light concentrator at 310 nm.

F IGURE 3.31: Comparison of LST and MST light concentrator at 365 nm.

In all three cases, the RAS values of LST light concentrator are slightly good in therange of [−22◦ , 22◦ ] comparing with the one of MST. The LST cut-off angle is smaller than
MST based on the different FOV of two telescope types (4.5◦ versus 8◦ respectively).

Development of light concentrator for LST

53

F IGURE 3.32: Comparison of LST and MST light concentrator at 465 nm.

3.3

Problems

In the current design of light concentrator, the protruding part of coated ESR warped asshown in Figure 3.33. This warpage made the ESR deformed from the ideal surface andthen reduce the performance of light concentrator. The performance reduction was proved
as shown in the next section. Besides, when attached in cluster, the warpage is also weakso it is pushed together by the adjacent light concentrator and deformed again or create
dead space as shown in Figure 3.34.

F IGURE 3.33: The warpage can be seen near the entrance aperture of light concentrator.

Development of light concentrator for LST

54

F IGURE 3.34: Influence of warpage.

3.4

Solution and discussion

3.4.1

Reinforcement of ESR by tape

• Method: In order to check the effect of warpage, a two-sided tape test was executed.
The warpage are shown in Figure 3.36 (a-2) as a cross section, floating from the ideal
surface (dashed line). First, the rotation measurement is performed. After that, 6
pieces of two-sided tapes were pasted on the back of 6 surfaces as shown in Figure
3.35. By pasting the tape directly on hexagonal frame, it was able to bring ESR film
close to the ideal surface. Then, the effect of warpage was confirmed by rotation
measurement once again. By comparing the results before and after taping, we canevaluate the effect of warpage. Three cases of tape whose width is 7 mm, 3 mm, and
1 mm were tested in turn.
• Results: The light concentrators No.264 in the second batch and No.29 were used inthis tape test. Figure 3.36 (b-1), (c-1), (d-1) show the state of LC No.264 after pasting
7 mm, 3 mm, 1 mm tape respectively. Figure 3.37 shows the rotation measuring
results of all 4 cases. The LC No.29 is only tested the 3 mm case for confirmation.
• Discussion: Adverse effects due to warpage were confirmed by rotation measurement. All cases of the test of No.264 performed better RAS values than the no-tapecase in the range of [−22◦ , −10◦ ] and [10◦ , 22◦ ] (see Figure 3.37). Also in this range,Development of light concentrator for LST

55

F IGURE 3.35: The state after pasting 6 pieces of two-sided tapes on the back of 6 surfaces. Left: 7 mm tape case. Right: 3 mm tape case.

the case of 3 mm tape showed the best performance, about 3% better than the caseof no tape at around −22◦ and 22◦ . At large angles in the range of [−22◦ , −10◦ ]and [10◦ , 22◦ ], the RAS value is larger by 1.5% in the case of tape than none. In
the range of [−10◦ , 10◦ ], the RAS of no-tape case was better, but unfortunately the
number of photons reflected from primary mirror at angles in this range is small.
So the RAS of this angle range is not important. For confirmation, the case of 3 mm
tape was performed once again with the LC No.29. The same effect can be seen in
Figure 3.38.
• Conclusion: The bad effects of warpage to LC performance were proved by above
experiment results. Moreover, a light concentrator with the cone design covering
the entire ESR was prototyped by 3D printer (see Figure 3.39). Without warpage,
this new prototype also gave a better performance than current design [16]. Thismeans that the reinforcement is necessary for current design of light concentrator.

3.4.2

Reinforcement of ESR by PET film

• Method: Polyethylene terephthalate (PET) is a material easy to handle. The PET
film of 0.15 mm thick was used in this test for warpage reinforcement. Figure 3.40
shows the reinforcement method. First, the PET film sheet is cut into the same
shape of protruding part. Next, the glue is attached to the back of warpage andspread evenly with a cotton swab. The cutting PET film is then pressed firmly attaching to the back of warpage. Leaked glue is swept with cotton swab. On the otherDevelopment of light concentrator for LST

56

F IGURE 3.36: (a-1): The state of warpage. (a-2): The cross section of warpage floatingfrom the ideal surface (dashed line). (b-1): The state after pasting 7 mm tape. (b-2): Thecross section of 7 mm tape case. (c-1): The state after pasting 3 mm tape. (c-2): The crosssection of 3 mm tape case. (d-1): The state after pasting 1 mm tape. (d-2): The crosssection of 1 mm tape case.

hand, the confirmation method is the same as the case of tape. Rotation measurements are performed before and after reinforcement. The LST light concentrator
No.254 and No.29 were used in this test.
• Results: Figure 3.41 and 3.42 show the results of No.254 and No.29 respectively.

Development of light concentrator for LST

57

F IGURE 3.37: Rotation measuring results of LC No.264, in 4 cases of tape.

F IGURE 3.38: Rotation measuring results of LC No.29, in only 2 cases: no tape and 3
mm tape.

In the case of No.29, the past result is also included for reference. In Figure 3.43
shown the results including the tape result for comparison.
• Discussion: The result after reinforcement gave a better RAS curve than the caseof current design, in the range of [−22◦ , −8◦ ] and [6◦ , 22◦ ]. Specially, the RAS values
around −22◦ and 22◦ are larger by 3% comparing to the result before reinforcement.
Moreover, as shown in Figure 3.43, the result after reinforcement is also better thanthe case of 3 mm tape over 2% around −22◦ and less than 1% around 22◦ . In theDevelopment of light concentrator for LST

58

F IGURE 3.39: Comparison of mass-produced light concentrator (left) and 3D printerprototype (right) [16].

F IGURE 3.40: (a): Cutting PET film into a rectangular 14 mm x 26 mm. (b): Attachingglue to the back of warpage. (c): Pasting PET film to the back of warpage. (d): The final
state after reinforcement.

range of [−8◦ , 6◦ ], the RAS values before reinforcement was better a little about 1%
but it is not significant based on the optical system.
• Conclusion: The reinforcement by PET film was pretty good comparing to the result of reinforcement of tape. But there is still only a little warpage after reinforcement, because PET is flexible and not too hard to reinforce the warpage perfectly.

Development of light concentrator for LST

59

F IGURE 3.41: The results before and after the PET film reinforcement in the case oflight concentrator No.29.

F IGURE 3.42: The results before and after the PET film reinforcement in the case oflight concentrator No.254.

Besides, the size of PET film was fixed to rectangular shape of 14 × 26 mm, a little
smaller than ESR protruding part to make a space for the glue leaks out, in orderto reduce the possibility of smearing ESR surface.

3.4.3

Reinforcement of ESR by SUS film

Stainless special used steel (SUS) is the next material considered after PET. It is hard,thin and light so that can be a good candidate for the reinforcement. The samples of SUS
film were ordered with rectangular shape of 13 × 18 mm. This smaller shape increases thespace for leaked glue and reduces weight. Moreover, there were two kinds of thickness totest, as 0.1 µm and 0.05 µm.

• Method: The reinforcement method and performance valuation are also the sameas the case of PET film.
• Results: Figure 3.44 and Figure 3.45 show the states of film and warpage respectively after reinforcement. The appearance of SUS film looks stronger and cleaner

Development of light concentrator for LST

60

F IGURE 3.43: Performance evaluating results of PET film vs 3 mm tape .

than PET film. Figure 3.46 shows the results of 2 cases of SUS film comparing withPET film results. As shown in yellow frame, the reinforced part of warpage in bothcase of SUS films became flatter than the case of PET film. There are still a little
warpages at 2 sides of protruding part (sky blue frames).

F IGURE 3.44: Left: the state of PET film after pasting. Right: the state of SUS film after
pasting.

F IGURE 3.45: Left: the state of warpage after PET film reinforcement. Middle: the stateof warpage after SUS 0.1 µm film reinforcement. Right: the state of warpage after SUS
0.05 µm film reinforcement.

Development of light concentrator for LST

61

F IGURE 3.46: Performance evaluation results of PET film and 2 cases of SUS film.

• Discussion: Three cases possess almost the same performance in the range [−20◦ , 22◦ ].
Around the peak of −22◦ , the case of SUS 0.1 µm shows the better RAS values about
under 2%. It is difficult to clear more the evaluation of 3 cases with current experiment system. The hardest SUS film of 0.1 µm has a better performance and seems
to be the best choice for the reinforcement. Moreover, a deformation test was carriedout in order to check the dead space created by press of adjacent light concentrator
as follows.
• Deformation test: When attached in module, LST light concentrators are pressedvery strongly by PMTs from behind. Three ABS plastic hooks of each cone is not
hard enough to keep the right direction. So the light concentrator is tilted a little
and pushes the adjacent one, depending on the case. In this test is described theworse case when a light concentrator is pressed strongly from the adjacent one.
Figure 3.47 shows the gap created when pressing 2 concentrators from 2 sides byhand, in 2 cases of SUS film and PET film. The corners of ESR protruding partbunched together with adjacent corners, and the reinforced warpages are warped
again to the inside and create a gap. In the case of SUS film, a wider gap can beseen comparing with the case of PET film. Its reason is because there are still wide
spaces in 2 sides of the warpage that is not reinforced (see yellow frames in Figure
3.48. These parts is weak and easy to be deformed when pushed from the side.

Development of light concentrator for LST

62

Besides, although PET film is softer than SUS film, it shows a good performancewith narrower gap. This is due to the larger surface area of PET film.

F IGURE 3.47: Left: The dead space is created by being pressed intentionally in the casethat two sides are reinforced by SUS films. Right: A narrow dead space is created bybeing pressed intentionally in the case that two sides are reinforced by PET films.

F IGURE 3.48: Yellow frame: the weak spaces which is not reinforced can be deformed
easily and create the dead space.

• Conclusion: The reinforcement by SUS film of 0.1 µm was only a little better than
the result of reinforcement by PET film. But the SUS film is quite hard enoughto against the warpage better than PET film. Thence it is a best choice for ESR
reinforcement. Besides, based on the deformation test, the size of SUS film wasfixed to 13 × 26 mm close to the size of PET film in order to reinforce the warpage
better and reduce the potential to cause gap.

Development of light concentrator for LST

3.4.4

63

Thermostat test

A thermostat test was carried out in order to check the deformation of reinforced warpage.
Two SUS film reinforced light concentrators and two PET film reinforced light concentrators were put into thermostat as the state shown in Figure 3.49 at the temperature of
69.5◦ C for one night (about 8 hours). After the test, there was no deformation and no glue
melting in appearance. The performance before and after the test were also checked.

F IGURE 3.49: Thermostat test.

3.4.5

Final conclusion

By the above research, the LST light concentrator is determined to the design reinforced
by SUS 0.1 µm film with rectangular shape of 13 × 26 mm as the final design (see Figure 3.50 and Figure 3.51). Seven new light concentrators were manufactured for performance evaluation. Figure 3.52 and 3.53 show the state when attaching into interface
plate, viewed from the side and from above respectively. Performance of these LCs will be
evaluated this year (2017).

Development of light concentrator for LST

F IGURE 3.50: Above: all reinforcement films. From the left side are PET film, SUS 0.05
µm of 13 × 18 mm film, SUS 0.1 µm of 13 × 18 mm film, and the rightmost one is the final
SUS 0.1 µm film with rectangular shape of 13 × 26 mm. SUS 0.05 µm of 13 × 18 mm and
SUS 0.1 µm of 13 × 18 mm films were used in the SUS-film reinforcement test. Bellow: ainclined look from the side.

F IGURE 3.51: SUS 0.1 µm film with rectangular shape of 13 × 26 mm

F IGURE 3.52: Cluster with 7 new light concentrators viewed from side.

64

Development of light concentrator for LST

F IGURE 3.53: Cluster with 7 new light concentrators viewed from above.

65

Chapter 4

Establishment of performance
evaluation system

In parallel with the development of light concentrator, the establishment of performance
evaluation system was also reviewed, repaired and renewed.

4.1

Establishment of measurement system

4.1.1

Rearrangement and cleaning

The laboratory was cleaned up after a long time of use. Unnecessary shelves and items
were put out (see Figure 4.1), the high voltage appliance was rearranged below the optical
table. The chair position for measuring person was also moved to close the entrance. As
mentioned in sub-subsection 3.2.4.1, a black curtain was hung between LED and PMT
system, only opened to approximately 17 × 26 cm hole in the middle for light pulses topass through. The purpose of this curtain is to prevent light reflections from the sidewalls and ceilings. Some places on the side walls that look possible to reflect light werecovered by black cloth too. Small torn holes on the entrance cloth were pasted with black
tape in order to prevent leaked light into the dark room. The noise-preventing cloth, analuminum foil wrapped by black electrical insulating cloth, was renewed instead of theold one.

67

Establishment of performance evaluation system

68

F IGURE 4.1: (a): before rearrangement. (b): after rearrangement.

4.2

Additional set-up of monitor PMT

One more PMT has been added just below the position of measuring PMT as a monitor,
in order to correct the RAS value. Figure 4.2 and 4.3 show this monitor PMT and theinstallation state of it. Figure 4.4 shows the signals detected both PMTs in two cases ofmask (left) and LC (right).
The performance of monitor PMT was evaluated and compared with measuring PMT.
The content of performance test is detection of 500 signals × 800 times. One time takes
about 15 seconds, thence the total time is about 3 hours 20 minutes. Figure 4.5 left shows
the results of performance test. The monitor PMT values decreased gradually with timeEstablishment of performance evaluation system

69

F IGURE 4.2: (a): The monitor PMT. (b): The set-up state of monitor PMT covered by thenoise-preventing cloth. (c): The position of both PMTs.

F IGURE 4.3: The experimental system after adding monitor PMT.

while the measuring PMT values were stable. After about 600 times, the monitor PMT
values became equal and continued to fall lower. In order to check when the monitor PMT
become stable, the LED was turned off and turned on again, after 15 minutes the second
performance test was executed (in order to ensure the same initial condition). Figure 4.5
right shows the results of confirmation test. The test content was also 500 signals × 800
times but stopped by a systematic breakdown after 700 times. The monitor PMT valuesEstablishment of performance evaluation system

70

F IGURE 4.4: Left: Measurement PMT signal graph (above) and monitor PMT signal
graph (below) of the mask case. Right: Measurement PMT signal graph (above) andmonitor PMT signal graph (below) of the LC case.

still continued to fall lower than measurement PMT values. Because of this difference inperformance, the correction of PMT by PMT seems to be difficult.

F IGURE 4.5: Left: results of the first confirmation test. Right: results of the second
confirmation test.

In fact, the correction test was executed to make sure. The on-axis measurement
are executed 10 consecutive times in order to get the RAS value distribution for 1 lightEstablishment of performance evaluation system

71

concentrator. The signals were detected by both monitor and measuring PMTs. The RAS
value was calculated in 2 ways: the traditional one as Equation 3.5, and the new one
using correction by monitor PMT gain values as follows:
RASmonitor (0◦ ) =xLC × ym1
×× 100%,
xm × yLC 3.7352(4.1)

where ym is the monitor PMT gain value of mask case, yLC is the monitor PMT gain valueof LC case. The detailed explanation of correction analysis is mentioned in Appendix B.
Figure 4.6 shows the correction results by monitor PMT. The RAS value distribution of
traditional case has a sharp shape with the mean value of 86.8% ± 0.196%, while thecorrection case shows a flat distribution with the mean value of 86.9% ± 0.307%. Basedon these unexpected results, the correction of PMT by PMT is considered impossible.

F IGURE 4.6: The results of correction test. (a): The RAS value distribution of traditional
way. (b): The corrected RAS value distribution of correcting way.

4.3

Establishment of measurement scripts

The waveforms of 500 signals are drawed in the same graph, saved as 1 ROOT file. So
there are 4 ROOT files for one case of mask or light concentrator. The waveforms canbe seen only after finishing the measurement and this is quite inconvenient. Besides,
the range of waveform and noise pedestal is defined in the sub-script connected frommeasurement script. So it is difficult to check whether the waveform overlaps the selected
time range or not. If not, the RAS value will be calculated incorrectly. On the other hand,Establishment of performance evaluation system72

the measurement script and analysis script are separate. The measured results were
saved in the form of ROOT file. The analysis takes a lot of time due to the convert fromraw data to ROOT file in the rotation case. Since the ROOT files can not be seen directly
when opening, it is also difficult to handle a lot of data at the same time.

F IGURE 4.7: Screen shot when measuring the rotation case. (a): 500 pulses of eachtime is displayed immediately after measuring. The above graph shows waveform of
500 pulses detected by measuring PMT. The below graph shows waveform of 500 pulses
detected by monitor PMT. Red line shows the time range of noise pedestal (left) andpulse (right). (b): the PMT gain value displayed when measuring so that we can check
if some large systematic errors appear. (c): the gain value of pedestal, pulse and theirresidual were calculated (analysed) immediately after each time and displayed in detailon screen.

The measurement script and analysis script have been re-written in only 1 file forboth case of mask and light concentrator. All result data (namely the PMT gain values ofmask case, LC case, and the RAS value) for one performance evaluation experiment will
be saved only in a text file as numerical data, in order to save time and to handle moreeasily. When measuring 4 times, the result of each time will be analysed immediately
and displayed on the screen as both graphs and numerical data (see Figure 4.7 (a), (c)).
The selected time ranges of noise pedestal and pulse are also displayed by red lines, asEstablishment of performance evaluation system

73

shown in Figure 4.7 (a). This is very convenient for detecting whether the waveform
overlap the selected range or not. Moreover, the ranges are changed automatically due
to the input wavelength. After mask case and light concentrator case are both measured,
RAS value is automatically calculated, displayed and written in the same result text file.
In the rotation measurement, the PMT gain value of each time is also displayed one by
one in the same graph, showing a curve such as a function of incident angle, in order tocheck current situation compared to the whole measurement results (see Figure 4.7 (b)).
Moreover, the measurement will be stopped and the announcement will be displayed if
measuring person makes a mistake of measuring the same case twice.

4.4

Establishment of replacement work

The replacement work is carried out between 2 measurements of mask and light concentrator, takes time about 1-2 minutes. The mini orange bulb is turned on during the
replacement work (see Figure 4.8 right). Because the high voltage is not turned off, it isdangerous for measuring person when replacing by naked hand in a weak-light situation.
Moreover, the light from mini bulb seems also strong for sensitive PMT and may affectthe measured results after replacing.

F IGURE 4.8: Left: location of ceiling light and the experiment system. Right: the mini
bulb is turned on for replacement work

In order to avoid this problem, a new solution has been thought out and tested. As
shown in Figure 4.9, a red LED light pen wrapped by black tape was used when replacingEstablishment of performance evaluation system

74

light concentrator (or mask). The light from this LED pen was reduced by black tape inorder to limit the impact on PMT.

F IGURE 4.9: LED light pen wrapped in black tape to reduce light.

The confirmation test was carried out in 2 steps as follows. First, the PMT had got
data of 500 signals × 40 times (about 12 minutes) in the state of mask case. With the highvoltage turned on and mini bulb turned off, the entrance window of PMT was irradiatedonly by red light from LED pen in 1 minute supposing in the worst case, and then themeasurement was carried out again as 500 signals × 80 times without any further action.
Figure 4.10 shows the PMT gain values before and after irradiation. Although the gain
decreased by about over 2% immediately after irradiation, it recovered with time, but
finally was still smaller about 1% than before irradiation.

F IGURE 4.10: The measured results of LED light pen confirmation test. Red: PMT gain
average value fluctuation before turning off high voltage. Black: PMT gain average value
fluctuation after turning off high voltage. Green: error bars of each value.

Light from the light pen has already been reduced to minimum that be able to see
with the naked eye. So the next solution is turning off the high voltage during the replacement time. The confirmation test was carried out in 2 steps as follows. First, theEstablishment of performance evaluation system

75

PMT had got data for about 12 minutes in the state of mask case. Then the high voltage was turned off. After waiting 1 minute (as the replacement time), it was turned on
again, and the PMT had got data for about 24 minutes without any further action. Figure 4.11 shows the PMT gain values before and after turning off the high voltage. The
red and black lines show PMT gain average value fluctuation before and after turning offhigh voltage, respectively. The green line shows error bars of each value. Although thegain decreased by about over 1% immediately after high-voltage turning off, but after 2
minutes it recovered to the same fluctuation before.

F IGURE 4.11: The measured results of confirmation test in the case turning off voltage.
Red: PMT gain average value fluctuation before turning off high voltage. Black: PMT
gain average value fluctuation after turning off high voltage. Green: error bars of eachvalue.

The same PMT gain values can be got after turning on the high voltage and waiting
2 minutes. The next confirmation test is about irradiating PMT by LED pen with the highvoltage turned off. The confirmation test was carried out in 2 steps as follows. First, thePMT had got data for about 12 minutes in the state of mask case. Then the high voltage
was turned off. The PMT entrance window was then irradiated only by LED pen in 1
minute supposing in the worst case. After that, the high voltage was turned on again,
and the PMT had got data for about 24 minutes without any further action. Figure 4.12
shows the PMT gain values before and after the test. Similar to previous measurement
result, the gain decreases by about over 1% immediately, but after 2 minutes it recovers
to the same fluctuation before.
Based on above measurement results, the replacement work was changed as follows
to keep PMT operation stable.

Establishment of performance evaluation system

76

F IGURE 4.12: The measured results of confirmation test in the case turning off voltage
and irradiating by the LED light pen. Red: PMT gain average value fluctuation before
turning off high voltage. Black: PMT gain average value fluctuation after turning offhigh voltage. Green: error bars of each value.

• Step 1: First, the measuring person turns off the high voltage, enters the darkroom, attaches the mask (or light concentrator) on PMT, leaves, and closes the darkroom. The measuring person then turns on the high voltage, waits 3 minutes (incase), then runs the measurement script.
• Step 2: After that, the measuring person turns off the high voltage, enters the darkroom again, replaces mask by light concentrator (or reversely), leaves and closes thedark room, turns on the high voltage and waits 3 minutes. Finally, the measuringperson runs the measurement script.

4.5

Establishment of rotation measurement

4.5.1

Problems

Figure 4.13 show 4 times of all PMT gain values as a function of incident angle. As shownin this Figure, the first time values from −40◦ to 40◦ (red line) was lower about 1% thananother times. Except the first time, all 3 times values were quite stable and overlapped
together. This means that the PMT gain increase in the first time and become stable after
that. After the establishment of replacement work described in the previous section, therotation measurement was executed again to verify but the problem is still not resolved,
as shown in Figure 4.13.

Establishment of performance evaluation system

77

F IGURE 4.13: Measurement results of 4 times in the case of light concentrator, after theestablishment of replacement work.

One round (1 time) from −40◦ to 40◦ takes about 25 minutes. So a 30 minutes waiting
test was carried out in order to eliminate the increase of PMT gain in the first time.
After attaching light concentrator and waiting 30 minutes, the rotation measurement
was executed. The measurement results were shown in Figure 4.14. There are somejaggy places in the curve as systematic errors, but entirely the first time values is stillquite low. As result, the increase of PMT gain appears when rotation measurement itself
starts, regardless of waiting time.
One more detailed measurement was tested in a different day. The measurement
was executed in following steps.

• Measure the mask case, get PMT gain average value xm (1)• Turn off the high voltage, replace mask with light concentrator, turn on high voltage
and wait for 2 minutes.
• After that, measure light concentrator case at θ = 0◦ , get PMT gain average valuexLC (2)• Do rotation measurement. In PMT gain values, values at θ = 0◦ were selected forcomparison as xLC_0 (3-0), xLC_1 (3-1), xLC_2 (3-2) and xLC_3 (3-3) for 4 times. The
average values of 4 times are not selected.

Establishment of performance evaluation system

78

F IGURE 4.14: Measurement results of 4 times in the case of light concentrator, after
waiting 30 minutes.

• Measure light concentrator case at θ = 0◦ once again, get PMT gain average valuexLC (4)• Turn off the high voltage, replace light concentrator with mask, turn on high voltage
and wait for 2 minutes.
• Measure the mask case, get PMT gain average value xm (5)These above results at θ = 0◦ are shown in Table 4.1. Based on the rotation measurement results as shown in Figure 4.15, the PMT values was still low as usual during thefirst time to over the half of second time.
Number
(1)
(2)
(3-0)
(3-1)
(3-2)
(3-3)
(4)
(5)

Name
xm
xLC
xLC_0
xLC_1
xLC_2
xLC_3
xLC
xm

PMT gain value (mV)
12048.937825.1
38355.1
38643.3
39092.938952.2
38943.5
12059.6

T ABLE 4.1: The results of on-axis case and rotation case at θ = 0◦ .

Establishment of performance evaluation system

79

F IGURE 4.15: Rotation measurement results of 4 times in the LC case of detailed test.

PMT value of mask case does not change before and after the rotation measurement(xm = 12048.9 (1) versus xm = 12059.6 (5)). This means that the LED light is stable during
the measurement. On the other hand, PMT value of LC case before rotation measurement
is smaller than after rotation measurement (xLC = 37825.1 (2) versus xLC = 38943.5 (4)).
Thus, there seemed to be something effected on PMT when rotating so that the PMTvalues increased during the rotation.
After above test, mask was replaced by light concentrator one more time, and rotation measurement was executed again (second test of LC case). Figure 4.16 left shows theresults of this test. The PMT values of the first time is a little low and becomes stable
quickly from around 5◦ .
Then the rotation measurement was carried out once again without replacement(third test of LC case). The results are shown in Figure 4.16 right. We can see thatthe stable state was maintained from the previous measurement due to doing nothing.
There are some incorrect values in the second time (green line) from 15◦ to 22◦ . Thesesystematic errors sometimes occur when measuring and should be remeasured.

Establishment of performance evaluation system

80

F IGURE 4.16: Left: rotation measurement results of 4 times in the second test of LC
case. Right: rotation measurement results of 4 times in the third test of LC case.

4.5.2

Solution and discussion

Next the signal cable was checked as a suspicious factor. In current system, the current
signal cable is short and connected with a heavy connector which hangs in the air asshown in the Figure 4.17 left. This heavy connector was guessed as the reason of thesignal increase in rotation measurement. It was replaced with a new longer signal cablein order to see whether there is any effect. Figure 4.17 right shows the tidier view after
changing than before. On the other hand, the static friction occurred when the cable
touched the table, and the measured signal was affected when the static friction converted
to dynamic friction. In order to prevent it, the signal cable and the electrical wires weredivided separately as shown in Figure 4.18. This system allows wires and cable movefreely up and down in the rotation experiment without touching the optical table.

F IGURE 4.17: Left: old electrical and signal wiring before establishment, hanging aheavy connector in the air. Right: new electrical and signal wiring system.

Establishment of performance evaluation system

81

F IGURE 4.18: Left: new electrical and signal wiring viewed from above. Right: closer
look.

The rotation measurement was executed once again and its results are showed in
Figure 4.19. The PMT gain increasing phenomenon does not happen. There was notendency of large changing in the PMT gain. Moreover, the RAS value at 0◦ was also
consistent with the on-axis measurement result. Figure 4.20 shows the comparison of 2
cases before and after the entire establishment. On the left side the difference became
larger, up to over 3% around θ = −22◦ , while about over 2% around θ = 22◦ on the rightside, due to the increase of PMT gain. The standard deviation became within 0.2% fromthe previous value of 0.4% ∼ 0.6%. Besides, the result of on-axis measurement did notchanged before and after the establishment of signal cable. The heavy connector seems
to effect much in the rotation measurement than on-axis measurement, then caused theincrease of PMT gain. By replacing with the new cable, there is no more force actingon PMT so the PMT gain values become more stable and accurate. This factor is very
important to evaluate the performance of light concentrator.

F IGURE 4.19: The measurement results after the establishment of signal cable.

Establishment of performance evaluation system

F IGURE 4.20: RAS curve comparison for 2 cases of before and after the entire establishment, as black and red line respectively.

82

Chapter 5

Future plan

As mentioned in Chapter 2, approximately 900 light concentrators were produced at
Ibaraki University from December 2015. Besides, about 150 pieces (first batch) were
measured for performance, and sent to the Institute for Cosmic Ray Research (ICRR) formini camera test. Furthermore, 36 modules (252 LC pieces of second and third batches)
were measured and sent to Spain for installation test.
However, the mass production is currently stopped because it is being discussed in
the CTA Japan group whether to reinforce the remaining light guide and to use it for the
first LST. Although the method of reinforcing ESR has been confirmed in this research,
there are two disadvantages that it takes time by handmade production one by one, andindividual difference is large. In order to solve these problems, there was a debate tochange the cone material to plastic and coat Aluminum on the inner surface by vapor
deposition. This work could be entrusted to a factory. It will be slightly higher in cost,
but quicker in time and no worry about individual differences. Besides, there was alsoa discussion about whether it is better to design the cut-off angle wider to detect more
photons. Because light concentrators for all 4 LSTs will be made at once, all parameters
should be reviewed entirely. The light concentrator production has to be in time for the
first light in November 2017, so it seems to be a difficult situation at this time.

83

Future plans

5.1

84

New design

The new design of LST light concentrator is being studied at Konan University. A direct
coating on current plastic cone was tested by Sanko K.K., but the reflectivity was only
40%, maybe due to the roughness of plastic surface. In the case of using current plastic
cone, the surface must be polished to increase the reflectivity. Furthermore, the new
design is being considered as a combination of Chrome plating and multi-layer coating
to improve the ultraviolet reflectivity. Figure 5.1 shows the CAD view of new cone. It
is divided to 3 parts, assembled on a jig and glued together. The method adhering thecone to the Aluminum plate by glue is also being considered too, with 1 mm Teflon sheet
between cone and PMT in order to prevent the discharge. Besides, the cut-off angle should
be larger than 27◦ as described above.

F IGURE 5.1: CAD view of new design of LST light concentrator.

All of the PMT modules will be calibrated in Tenerife, then sent to Barcelona on
April 2017. The new LST light concentrators are expected to be ready on July 2017.
Besides, the photon collection efficiency of the current design is very good, so a further
modification should be tried. If the new design cannot be in time for the deadline oflight concentrator delivery according to the construction schedule of first LST, the current
design should be used. In addition, the current design has been finally confirmed andevaluated performance as a finished product, and we are proceeding to publish paper.
At least the mass-produced light concentrators were used for mini camera test at ICRR
and installation test in La Palma well. Whether the current design will be used in CTA
depends on the current research and development of the new one.

Chapter 6

Summary

In this study, we confirmed the warpage problem in current design of CTA LST light
concentrator and studied the reinforcement with two-side tapes, PET films, and SUS
films. Based on rotation measurement results at 365 nm as shown in chapter 3, theLST light concentrator is determined to the design reinforced by SUS 0.1 µm film withrectangular shape of 13 × 26 mm as the final design. Seven new light concentrators were
manufactured and being measured to evaluate the performance at 310 nm, 365 nm, and465 nm.

F IGURE 6.1: All light concentrators. From the left side are LC without reinforcement,
PET reinforced LC, SUS 0.05 µm LC, SUS 0.1 µm LC, final design LC (1s) and 3D printerLC.

On the other hand, the performance evaluation system has been established overall. The inside of dark room was rearranged and cleaned. The measurement and analysis
scripts are checked, fixed and re-written in order to confirm clearly the result during measurement, reduce mistakes and handle the result data more flexibly. One monitor PMT
was added and checked but the correction could not be executed, due to the difference intime dependence of the gain of 2 PMTs. The replacement work from mask to LC between

85

Summary86

measurements of mask case and LC case (or inversely) was reviewed and the high voltage is decided to be turned off during the replacement work. The signal cable connecting
PMT to DRS4 was changed by a new long one. Without the impact of heavy connector
on PMT, the signals could be transmitted stable with less systematic errors. Based onthese establishments, the rotation measurement result at 0◦ were matched with on-axis
measurement result. The increase of PMT gain values which caused the systematic errorof 1.6% difference at θ = 0◦ was solved.
Besides, about 900 light guides had been completed in February 2016 as mass production. 150 pieces of finished products were sent to ICRR for mini camera test. 252
pieces (36 clusters) of finished light concentrators have been evaluated with LED 365 nm
and sent to ICRR in 2 batches, and then sent to Spain for attachment test. The averagevalue of RAS of first and second batch was 84.5% ± 1.66% and 85.1% ± 1.55% respectively (see Figure 3.15 and 3.16 left). However, the mass production has been stopped
from March 2016 until now because of the internal discussion in Japan group about current design of LST light concentrator. Now, the new design of it and interface plate arebeing studied at Konan University. The prototype of new design will be completed soonand compared performance with the current one in order to have a best choice for LST
light concentrator.

Appendix A

RAS value and standard deviation

This Appendix describes in detail how to calculate the RAS value in details. Figure A.1
shows the signal graphs of both mask case and LC case.

F IGURE A.1: Left: the signal graph of mask case. Right: the signal graph of LC case.

• Pedestal, signal and residual:

The measurement is subdivided into 4 times(Ntrial = 4), each consisting of 500 pulses (N = 500). In each time of mask case (orLC case), the integral of each signal and its noise pedestal is calculated as s m_ i ± σs_ iand p m_ i ± σp_ i (i=0,1,2,3 for 4 times) respectively, withsP

PN

s m_ i =s
k=1 m_ kNPNp m_ i =k=1, σs_ i =

p m_k

N

N
(s
− s m_ i )2
k=1 m_ k

N×N
sP, σp_ i =

87

,

N
(p
− p m_ i )2
k=1 m_ k

N×N.

RAS value and standard deviation

88

where k = 0,1,2,...,N, σs_ i and σp_ i are the statistical errors calculated by ROOT
command of "GetMeanError()". Then, the average of 500 pulses and its statisticalerror for each trial are calculated as xm_ i ± σm_ i with

xm_k = s m_k − p m_k ,
PN
q
xm_k
xm_ i = k=1, σm_ i = σs_ i 2 + σp_ i 2 ,Nwhere σm_ i is the statistical error of average value xm_ i , calculated by formula of error propagation. These calculation is written in the measurement script as follows.
# total sum of pedestal
P_1 = h1.Integral(p_start,p_end)
pes1.Fill(P_1)# total sum of signal
S_1 = h1.Integral(t_start, t_end)
sig1.Fill(S_1)# total sum of residual
s_p_1 = S_1 - P_1
charge1.Fill(s_p_1)(bowdlerise),→,→# calculate LG (or Mask) value:
mean_pes_1 = pes1.GetMean()
err_pes_1 = pes1.GetMeanError()
mean_sig_1 = sig1.GetMean()
err_sig_1 = sig1.GetMeanError()
mean_1= charge1.GetMean()
err_all1= math.sqrt(pow(err_sig_1,2)+pow(err_pes_1,2))
print "%.1f deg: mean_pes= %.1f+/-%.1f mean_sig= %.1f+/-%.1f
mean2= %.1f +/- %.1f" % (current_angle,mean_pes_1, err_pes_1, mean_sig_1,
err_sig_1, mean_1, err_all1)

In mask case, the average value xm ± εm of 4 times• Average value of 4 times:(Ntrial = 4) will be the final value of mask case with
sP

P3

xm =

i =0 xm_ i

4, εm =

3
2
i =0 (xm_ i − xm )4,

RAS value and standard deviation89

where εm is known as standard deviation. In LC case, the same calculation is also
executed to find the average value xLC ± εLC with
sP

P3

xLC =

i =0 xLC_ i

4, εLC =

3
2
i =0 (xLC_ i − xLC )4,

where εLC is known as standard deviation. These calculation is written in the measurement script as follows.

,→

mean_all_1 = sum_all_1/Ntrial
sum_pow_1 = 0
if Ntrial == 1:
RMS_1 = err_all_1
else:
for i in range(Ntrial):
sum_pow_1 += pow ( (li_me_1[i]-mean_all_1) ,2)
RMS_1 = math.sqrt(sum_pow_1/Ntrial)
txtfile.write("%s %.1f %f %f\n" % ( keyword, current_angle ,mean_all_1, RMS_1) )print ’Mean_all = %.1f +/-%.1f’ % ( mean_all_1, RMS_1)• RAS value: The RAS value at each θ is calculated as RAS(θ ) ± εRAS(θ) withxLC
1
×× 100 %,
xm cos θ × 3.7352
s
µ
¶ µ
¶
εLC 2
εm 2
εRAS(θ) = RAS(θ ) ×
+
,
xLC
xm

RAS(θ ) =where εRAS(θ) is known as entire standard deviation at θ , calculated by the error
propagation formula. The RAS value calculation is written in the measurement
script as follows.
ras = lg[i] /(m * math.cos(angle[i]/180*math.pi) *3.7352) *100
ras_err = ras * math.sqrt( pow( m_err/m ,2) + pow( lg_err[i]/lg[i] ,2) )print ’%.1f RAS= %.1f +/- %.1f’ % (angle[i], ras, ras_err)
f.write("RAS %.1f %f %f\n" % ( angle[i], ras, ras_err))Appendix B

RAS value correction by monitor
PMTThis Appendix describes in detail how to compensate the RAS value by monitor PMT
gain values. The analysis of monitor PMT gain values are also executed as the same as
measurement PMT gain values (see Appendix A. After measuring the mask case, we get
2 average values of measurement PMT and monitor PMT as xm ± εm and ym ± η m withsP

P3

i =0 xm_ i

xm =, εm =

4i =0 ym_ i

4

4

,

sP

P3

ym =

3
2
i =0 (xm_ i − xm )32
i =0 (ym_ i − ym ), ηm =

4.

After measuring the LC case, we get 2 average values of measurement PMT andmonitor PMT as xLC ± εLC and yLC ± η LC with
sP

P3

xLC =

i =0 xLC_ i

4

yLC =

4

4
sP

P3

i =0 yLC_ i32i =0 (xLC_ i − xLC ), εLC =
, η LC =91

32
i =0 (yLC_ i − yLC )

4

,

.

RAS value correction by monitor PMT

92

The compensated RAS value at each θ is calculated as RASmo (θ ) ± εmo with
xLC
y
1
× m ×
× 100 %,
xm
yLC cos θ × 3.7352
sµ
¶ µ
¶ µ
¶
¶ µ
εLC 2
η LC 2
ηm 2
εm 2
+
+
,
εmo = RASmo (θ ) ×
+
xLC
xm
yLC
ym

RASmo (θ ) =where εmo is known as entire standard deviation, calculated by the error propagation
formula. The RAS value calculation is written in the measurement script as follows.

ras_mo = lg[i] * m_mo / (m * lg_mo[i] *math.cos(angle[i]/180*math.pi) * 3.7352),→*100
ras_mo_err = ras_mo * math.sqrt( pow( m_err/m ,2) + pow( m_mo_err/m_mo ,2) +pow(,→
lg_err[i]/lg[i] ,2) + pow( lg_mo_err[i]/lg_mo[i] ,2))#print ’LG = %.1f +/- %.1f ; Mask = %.1f +/- %.1f’ % (lg,lg_err, m, m_err)
print ’RAS-Mo = %.1f +/- %.1f’ % ( ras_mo, ras_mo_err)
f.write("RAS-Mo %.1f %f %f\n" % ( angle[i] , ras_mo, ras_mo_err))

Appendix C

RAS tables of the second and third
batch

This Appendix lists all the RAS value measured by me, divided into 2 table of second andthird batch.
T ABLE C.1: The RAS value table of second batch. The ESR of No.156 was used for test.
The LCs of No.167, 178, 187, 194, 237, and 254 were left at Ibaraki University. The rest
(126 pieces - 18 clusters) was sent to Spain for attachment test.

LC No.

RAS value

LC No.

RAS value

LC No.

RAS value

147

84.4

192

82.5

237

84.5

148

83.6

193

85.4

238

85.8

149

82.5

194

80.7

239

86.0

150

85.1

195

82.4

240

88.2

151

82.8

196

83.7

241

85.9

152

85.4

197

84.6

242

85.7

153

84.0

198

82.4

243

84.9

154

86.9

199

82.2

244

85.4

155

81.7

200

81.3

245

85.1

156

None

201

84.2

246

85.0

157

85.7

202

83.1

247

87.5

158

86.0

203

84.3

248

89.1

159

85.5

204

82.4

249

84.0

160

85.6

205

84.1

250

84.9

93

RAS tables of the second and third batch

94

161

85.6

206

83.5

251

86.4

162

82.7

207

84.8

252

85.3

163

85.5

208

82.8

253

84.5

164

83.7

209

84.1

254

81.5

165

86.0

210

82.7

255

85.1

166

84.9

211

83.4

256

87.5

167

81.0

212

84.1

257

83.0

168

81.8

213

84.6

258

84.6

169

82.7

214

84.2

259

84.4

170

82.7

215

81.0

260

84.8

171

83.7

216

85.2

261

87.5

172

81.1

217

84.7

262

84.9

173

85.7

218

84.1

263

83.3

174

84.2

219

83.5

264

83.0

175

84.9

220

84.1

265

83.4

176

82.5

221

82.9

266

81.9

177

86.6

222

83.6

267

82.3

178

84.4

223

85.8

268

82.8

179

83.2

224

84.0

269

81.5

180

83.6

225

84.0

270

83.5

181

85.9

226

84.1

271

85.3

182

85.0

227

83.8

272

85.6

183

88.0

228

83.6

273

83.9

184

89.1

229

86.8

274

83.4

185

86.3

230

85.2

275

83.0

186

88.0

231

83.6

276

85.4

187

88.8

232

85.9

277

85.5

188

88.9

233

85.0

278

85.1

189

85.5

234

85.5

279

84.1

190

83.5

235

86.5

Average

84.5

191

85.7

236

85.3

RAS tables of the second and third batch

95

T ABLE C.2: The RAS value table of third batch. The LCs of No.349, 350, 351, 352, and353 were left at Ibaraki University. The rest (126 pieces - 18 clusters) was sent to Spainfor attachment test.

LC No.

RAS value

LC No.

RAS value

LC No.

RAS value

280

82.7

324

84.9

368

85.7

281

86.4

325

84.6

369

85.0

282

88.5

326

84.6

370

83.6

283

87.2

327

85.4

371

85.0

284

87.0

328

84.9

372

85.0

285

83.9

329

86.5

373

83.9

286

85.4

330

84.1

374

85.1

287

83.8

331

84.4

375

84.7

288

83.1

332

85.9

376

85.6

289

86.1

333

86.7

377

86.6

290

84.6

334

85.7

378

84.2

291

86.6

335

82.7

379

86.4

292

84.9

336

81.3

380

84.9

293

83.1

337

84.9

381

86.0

294

82.8

338

86.0

382

85.0

295

84.3

339

83.1

383

86.2

296

85.1

340

84.3

384

85.7

297

85.2

341

86.0

385

85.3

298

85.7

342

86.7

386

86.9

299

84.3

343

85.0

387

85.7

300

86.1

344

84.6

388

87.2

301

85.8

345

85.4

389

87.6

302

85.8

346

85.8

390

84.3

303

85.3

347

85.0

391

87.0

304

85.1

348

84.2

392

84.3

305

84.1

349

86.6

393

85.2

306

86.2

350

59.9

394

88.1

307

85.1

351

67.5

395

86.3

308

82.9

352

68.9

396

86.8

309

84.5

353

73.0

397

86.2

RAS tables of the second and third batch

96

310

85.0

354

82.7

398

84.8

311

84.1

355

83.1

399

85.6

312

84.0

356

85.4

400

86.6

313

83.6

357

82.4

401

86.4

314

87.2

358

85.8

402

86.6

315

83.0

359

85.2

403

87.2

316

83.3

360

87.4

404

85.9

317

85.4

361

86.8

405

87.5

318

86.2

362

83.3

406

85.2

319

83.0

363

79.2

407

88.6

320

84.8

364

82.9

408

84.9

321

81.6

365

85.3

409

88.0

322

84.2

366

84.9

410

86.8

323

84.6

367

86.4

Average

85.3

Appendix D

On-axis measurement script

The re-written on-axis measurement script is recorded as follows. This script is used for
LC case of on-axis measurement, and mask case of both on-axis and rotation measurement.

12#!/bin/sh#!/usr/bin/env python

3
4
5
6
7
8
9
10
11

import ROOT
import gpd3303s
import sigma_koki
import sys
import os
import time
import subprocess
import math

12
13
14
15
16
17
18

19

20

argv = sys.argv
argc = len(argv)
values = {}if argc != 8:
print ’Usage:’#print ’rotation_byTan.py DRS4_Events_Number Rotation_Angle1 STEP1,→
Rotation_Angle2 STEP2 Rotaion_Angle3 STEP3 Trial_Number’print ’rotation_byTan_withMo.py DRS4_Events_Number Trial_Number Number LG(or,→Mask)’
sys.exit()

21
22
23
24
25
26

DRS_EXE="/home/cta/tanaka/work/11100301_simple_drs4_daq2/drs-4.0.0/drs_simple_ch1-2"
THD=0.5
DEG = 400 # 400 is equal to 1 degree######################
NEVE=int(argv[1])#97On-axis measurement script

27
28
29
30
31
32
33
34
35

36

37
38
39
40

Ntrial=int(argv[2]) #length=int(argv[3]) # wave length: 365, 465 or 310
month=argv[4]#day=argv[5]number=argv[7]keyword=argv[6]if keyword == "M":keyword ="Mask"
DIR="/home/cta/work/LightGuide/17\%s\%s_\%d_\%s/with\%s" \% (month, day, length,,→
number, keyword)
fin_dir = "/home/cta/work/LightGuide/17\%s\%s_\%d_\%s/" \% (month, day, length,,→
number) # for text file
vfile = open("\%s/voltage.txt" \% DIR, "w")######################
gpd = gpd3303s.GPD3303S()
gpd.open("/dev/ttyUSB0")

41
42
43
44
45
46

gsc02 = sigma_koki.GSC02()
gsc02.open(’/dev/ttyUSB1’, 2)status = gsc02.getStatus()print "Initial Status", statuscurrent_pos = int(status.split(",")[0])

47
48
49
50
51

print "current_pos =", current_pos
if current_pos!=0:
gsc02.move(-current_pos, 0) # reset position
time.sleep(5) # 5

52
53
54
55
56
57

58

for i in range(1): # 10#time.sleep(1)status = gsc02.getStatus()print "Current Status", status
if status == ’\%d,\%d,K,K,R’ \% (current_pos , current_pos): # oldver,→
is 40000
break

59
60

current_angle = float(status.split(",")[0])/400

61
62
63
64
65

trial = 0
sum_all_1, sum_all_2 = 0.0, 0.0
li_me_1 = []# li_me = list means,
li_me_2 = []

66
67

dt

= (1./2.)

# ns

68
69
70
71
72
73
74
75

if length == 310:
ns
= 0
# chousei you
tstart = 240.
# Signal starttend= tstart + ns+100. # Signal end
pend= tstart - 10
# Pedestal startpstart = pend
- ns-100. # Pedestal end
p_start = int(pstart/dt); # pedestal start cell98On-axis measurement script

76
77
78

p_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

79
80
81
82
83
84
85
86
87

tstart_mo = tstart- 0.
# Signal start - monitor
tend_mo= tend - 0.
# Signal end - monitor
pend_mo= pend - 0.
# Pedestal start - monitor
pstart_mo = pstart- 0.
# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

88
89
90
91
92
93
94
95
96
97

elif length == 365:
pstart = 80.
# Pedestal startpend= pstart + 120.
# Pedestal end
tstart = 210.
# Signal starttend= tstart + 120.
# Signal end
p_start = int(pstart/dt); # pedestal start cellp_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

98
99
100
101
102
103
104
105
106
107

sa = 0.
tstart_mo = tstart- sa# Signal start - monitor
tend_mo= tend - sa
# Signal end - monitor
pend_mo= pend - sa
# Pedestal start - monitor
pstart_mo = pstart- sa# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

108
109
110
111
112
113
114
115
116
117
118

elif length == 465:
ns
= 35
tstart = 210.
# Signal starttend= tstart + ns+20. # Signal end
pend= tstart - 10
# Pedestal startpstart = pend
- ns-20. # Pedestal end
p_start = int(pstart/dt); # pedestal start cellp_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

119
120
121
122
123
124
125
126
127

tstart_mo = tstart- 5.
# Signal start - monitor
tend_mo= tend - 5.
# Signal end - monitor
pend_mo= pend - 5.
# Pedestal start - monitor
pstart_mo = pstart- 5.
# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

99On-axis measurement script

128
129

else :
print ’Need to change the pesdetal and signal range with wavelength.’

130
131
132
133
134
135
136
137
138
139
140
141
142
143

#li_err = [] # li_me = list means, li_err = list errors
txtfile = open("\%strial_all.txt" \% ( fin_dir),"a") #f = open("\%strial_all.txt" \% ( fin_dir),"r+b")i = 0lines = f.readlines()
for i,line in enumerate(lines):#type_, average= line.split("")
type_ = line.split("-")[0]
if type_ == keyword:print "\%s has already done" \% keyword
f.close()sys.exit()
f.close()

144
145
146
147
148
149
150
151
152
153

# pedestal & signal range’s graphh_range = ROOT.TH1D("test","test",560,-30.,530)
h_range.SetAxisRange(-50,350,"Y")ma,z = int(0), int(0)for ma in range (100):for z in range (int(pstart),int(pend+1)):
h_range.Fill(z)for z in range (int(tstart),int(tend+1)):
h_range.Fill(z)

154
155
156
157
158
159
160
161
162
163

# pedestal & signal range’s graph - monitor
h_range_mo = ROOT.TH1D("test2","test2",560,-30.,530)
h_range_mo.SetAxisRange(-50,350,"Y")ma,z = int(0), int(0)for ma in range (100):for z in range (int(pstart_mo),int(pend_mo+1)):
h_range_mo.Fill(z)for z in range (int(tstart_mo),int(tend_mo+1)):
h_range_mo.Fill(z)

164
165
166
167

c1 = ROOT.TCanvas(number, number, 0,0,400,800)
c1.Divide(1,2)#c1.cd(1)

168
169
170
171
172
173

174
175
176
177
178

i=0
for trial in range(Ntrial):#for j in range(SumNS): ##print "Trial : \%d, current angle : \%.1f deg, St : \%s" \%,→(trial,current_angle, gsc02.getStatus())#time.sleep(0.5)
c1.cd(1)fname= "\%s/trial\%04d_\%.1fdeg.dat" \% (DIR, trial, current_angle)
fout_name = "\%s/trial\%04d_\%.1fdeg.root" \% (DIR, trial, current_angle)
os.system("\%s \%f \%d \%s true 2." \% (DRS_EXE, THD, NEVE, fname))100On-axis measurement script

179

,→
180
181

101

vfile.write("\%d \%s \%f \%s\n" \% (time.time(), fname,gpd.getVoltageOutput(1), gsc02.getStatus()))
vfile.flush()#print "j : \%d " \% j182

# save to ROOT file
f = open(fname)lines = f.readlines()
nlines = len(lines)
t1 = -1e10
for i, line in enumerate(lines):t, v1, v2 = line.split(" ")t = float(t)if i == 0:
tstart = t
if t1 > t:tend = t1
f.close()
break
else:
t1 = t

183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208

,→
,→
209

,→
,→
210
211

,→
,→
212

,→
,→
213
214
215
216
217
218

nsamples = inevents = nlines/nsamples
f = open(fname)lines = f.readlines()
fout = ROOT.TFile(fout_name, "create")
for i, line in enumerate(lines):
if i\%nsamples == 0:
if NEVE <1000:
hist1 = ROOT.TH1D("hist1_\%03d" \% (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
hist2 = ROOT.TH1D("hist2_\%03d" \% (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
else:
hist1 = ROOT.TH1D("hist1_\%04d" \% (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
hist2 = ROOT.TH1D("hist2_\%04d" \% (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
t, v1,v2 = line.split(" ")t = float(t)v1 = float(v1)v2 = float(v2)hist1.Fill(t, v1)
hist2.Fill(t, v2)

219
220
221

if i\%nsamples == nsamples - 1:
hist1.Write()On-axis measurement script

222

102

hist2.Write()

223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245

# calculate signal of LC or Mask
sig1,sig2 = ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)
charge1, charge2 = ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)
pes1,pes2= ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)#c1.cd(trial+1)#c1.Update()
for i in range(NEVE):
if NEVE <1000:
h1 = fout.Get("hist1_\%03d" \% i)else:
h1 = fout.Get("hist1_\%04d" \% i)
if not h1:
break# draw all signals to 1 graphif (i ==0):
h1.SetAxisRange(-50,350,"Y")h1.Draw()
else:
h1.Draw("SAME")# total sum of pedestal
P_1 = h1.Integral(p_start,p_end)
pes1.Fill(P_1)

246
247
248
249

# total sum of signal
S_1 = h1.Integral(t_start, t_end)
sig1.Fill(S_1)

250
251
252
253
254
255

s_p_1 = S_1 - P_1
charge1.Fill(s_p_1)
h_range.SetLineColor(2)h_range.Draw("SAME")
c1.Update()

256
257
258
259
260
261
262
263

# calculate signal of Monitor
c1.cd(2)for i in range(NEVE):
if NEVE <1000:
h2 = fout.Get("hist2_\%03d" \% i)else:
h2 = fout.Get("hist2_\%04d" \% i)

264
265
266
267
268
269
270
271
272
273

if not h2:
break# draw all Monitor’s signals to 1 graphif (i ==0):h2.SetAxisRange(-50,350,"Y")h2.Draw()
else:
h2.Draw("SAME")# total sum of pedestal

On-axis measurement script

103

P_2 = h2.Integral(p_start_mo,p_end_mo)
pes2.Fill(P_2)

274
275
276

# total sum of signal
S_2 = h2.Integral(t_start_mo, t_end_mo)
sig2.Fill(S_2)

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s_p_2 = S_2 - P_2
charge2.Fill(s_p_2)
h_range_mo.SetLineColor(2)h_range_mo.Draw("SAME")
c1.Update()

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,→
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# calculate LG (or Mask) value:
mean_pes_1 = pes1.GetMean()
err_pes_1 = pes1.GetMeanError()
mean_sig_1 = sig1.GetMean()
err_sig_1 = sig1.GetMeanError()
mean_1= charge1.GetMean()err_1= charge1.GetMeanError()err_all_1 = math.sqrt(pow(err_sig_1,2)+pow(err_pes_1,2)) # total error
mean_1 = mean_sig_1 - mean_pes_1
print "\%.1f deg: mean_pes= \%.1f+/-\%.1f mean_sig= \%.1f+/-\%.1f
mean2= \%.1f +/- \%.1f" \% (current_angle,mean_pes_1, err_pes_1, mean_sig_1,
err_sig_1, mean_1, err_all_1)#print "\%.1f deg:mean= \%.1f +/- \%.1f" \% (current_angle, mean, err)

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,→

li_me_1.append(mean_1)
sum_all_1 += li_me_1[trial]
if Ntrial >1:
txtfile.write("\%s_\%d \%.1f \%f \%f\n" \% ( keyword, trial, current_angle, mean_1, err_all_1))

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,→
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# calculate Monitor’s value:
mean_pes_2 = pes2.GetMean()
err_pes_2 = pes2.GetMeanError()
mean_sig_2 = sig2.GetMean()
err_sig_2 = sig2.GetMeanError()
mean_2= charge2.GetMean()err_2= charge2.GetMeanError()err_all_2 = math.sqrt(pow(err_sig_2,2)+pow(err_pes_2,2)) # total error
mean_2 = mean_sig_2 - mean_pes_2
print "\%.1f-Mo deg: mean_pes= \%.1f+/-\%.1f mean_sig= \%.1f+/-\%.1f
mean2= \%.1f +/- \%.1f" \% (current_angle,mean_pes_2, err_pes_2, mean_sig_2,
err_sig_2, mean_2, err_all_2)#print "\%.1f deg:mean= \%.1f +/- \%.1f" \% (current_angle, mean, err)

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,→

li_me_2.append(mean_2)
sum_all_2 += li_me_2[trial]
if Ntrial >1:
txtfile.write("\%s-Mo_\%d \%.1f \%f \%f\n" \% ( keyword,trial,current_angle , mean_2, err_all_2))

On-axis measurement script320

fout.Close()f.close()# finish saving to ROOT file

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if trial == Ntrial-1:
print ’The Measurement has just finished.’

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mean_all_1 = sum_all_1/Ntrial
sum_pow_1 = 0
if Ntrial == 1:
RMS_1 = err_all_1
else:
for i in range(Ntrial):
sum_pow_1 += pow ( (li_me_1[i]-mean_all_1) ,2)
RMS_1 = math.sqrt(sum_pow_1/Ntrial)
txtfile.write("\%s \%.1f \%f \%f\n" \% ( keyword, current_angle ,mean_all_1, RMS_1) )print ’Mean_all = \%.1f +/-\%.1f’ \% ( mean_all_1, RMS_1)

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,→
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mean_all_2 = sum_all_2/Ntrial
sum_pow_2 = 0
if Ntrial == 1:
RMS_2 = err_all_2
else:
for i in range(Ntrial):
sum_pow_2 += pow ( (li_me_2[i]-mean_all_2) ,2)
RMS_2 = math.sqrt(sum_pow_2/Ntrial)
txtfile.write("\%s-Mo \%.1f \%f \%f\n" \% ( keyword, current_angle ,mean_all_2, RMS_2) )print ’Mean_Monitor = \%.1f +/-\%.1f\n’ \% ( mean_all_2, RMS_2)

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#sys.exit()
txtfile.close()

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# calculate RAS
f = open("\%strial_all.txt" \% ( fin_dir),"r+w") #i = 0lines = f.readlines()
count = 0
for i,line in enumerate(lines):
type_ = line.split(" ")[0]
if type_ =="LG":current_angle = float(line.split(" ")[1])lg = float(line.split(" ")[2])# LG
lg_err = float(line.split(" ")[3]) # LG’s error
count += 1
elif type_ =="LG-Mo":
lg_mo = float(line.split(" ")[2])# LG’s monitor
lg_mo_err = float(line.split(" ")[3])# LG’s monitor error
count += 1
elif type_ =="Mask":

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On-axis measurement script

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m = float(line.split(" ")[2])# maskm_err = float(line.split(" ")[3])# mask’s error
count += 1
elif type_ =="Mask-Mo":
m_mo = float(line.split(" ")[2])# mask’s monitor
m_mo_err = float(line.split(" ")[3])# mask’s monitor error
count += 1

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if count == 2 :print ’No LG or M’
elif count == 4:
ras = lg/(m*math.cos(current_angle/180*math.pi)*3.7352) *100
ras_err = ras * math.sqrt( pow( m_err/m ,2) + pow( lg_err/lg ,2) )print ’LG
= \%.1f +/- \%.1f ; LG-Mo= \%.1f +/- \%.1f’ \% (lg,lg_err, lg_mo,,→
lg_mo_err)
print ’Mask = \%.1f +/- \%.1f ; Mask-Mo = \%.1f +/- \%.1f’ \% ( m,m_err, m_mo,,→
m_mo_err)
print ’RAS
= \%.1f +/- \%.1f’ \% ( ras, ras_err)
f.write("RAS \%.1f \%f \%f\n" \% ( current_angle, ras, ras_err))

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ras_mo = lg * m_mo / (m *math.cos(current_angle/180*math.pi)* lg_mo * 3.7352) *100
ras_mo_err = ras_mo * math.sqrt( pow( m_err/m ,2) + pow( m_mo_err/m_mo ,2) +pow(,→
lg_err/lg ,2) + pow( lg_mo_err/lg_mo ,2))#print ’LG = \%.1f +/- \%.1f ; Mask = \%.1f +/- \%.1f’ \% (lg,lg_err, m, m_err)
print ’RAS-Mo = \%.1f +/- \%.1f’ \% ( ras_mo, ras_mo_err)
f.write("RAS-Mo \%.1f \%f \%f\n" \% ( current_angle , ras_mo, ras_mo_err))
else:
print "count = \%d :Sthing’s wrong!" \% (count)f.close()time.sleep(3)

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sys.exit()

Appendix E

Rotation measurement script
The re-written rotation measurement script is recorded as follows. This script is onlyused for LC case of rotation measurement.
12#!/bin/sh#!/usr/bin/env python

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import ROOT
import gpd3303s
import sigma_koki
import sys
import os
import time
import subprocess
import math

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argv = sys.argv
argc = len(argv)# date ; python rotation_byTan_withMo.py 500 20 1 30 0.5 40 1 4 1011 365 3s-rot-3 ;,→python hvoff.py 0

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if argc != 12:
print ’Usage:’print ’rotation_editbyTanaka.py DRS4_Events_Number Rotation_Angle1 STEP1,→
Rotation_Angle2 STEP2 Rotaion_Angle3 STEP3 Trial_Number’sys.exit()
day = argv[9]number =argv[11]length = int (argv[10])

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DIR="/home/cta/work/LightGuide/17%s_%d_%s/withLG" % (day,length, number)
fin_dir = "/home/cta/work/LightGuide/17%s_%d_%s/" % ( day, length, number) # for text,→
file
vfile = open("%s/voltage.txt" % DIR, "w")107

Rotation measurement script

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#time.sleep(60*90)

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DRS_EXE="/home/cta/tanaka/work/11100301_simple_drs4_daq2/drs-4.0.0/drs_simple_ch1-2"
THD=0.5
EX=0.1#NEVE=500 # ~10 sec
DEG = 400 # 400 is equal to 1 degree######################
NEVE=int(argv[1]) #Rotdeg1=int(argv[2]) # Rotation Angle (deg)STEP1=float(argv[3]) #Rotdeg2=int(argv[4])STEP2=float(argv[5])Rotdeg3=int(argv[6])STEP3=float(argv[7])Ntrial=int(argv[8])

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######################
gpd = gpd3303s.GPD3303S()
gpd.open("/dev/ttyUSB0")

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gsc02 = sigma_koki.GSC02()
gsc02.open(’/dev/ttyUSB2’, 2)status = gsc02.getStatus()
current_angle = -Rotdeg3
NSTEP1 = int(Rotdeg1/STEP1)+1 #NSTEP2 = int((Rotdeg2-Rotdeg1)/STEP2)-1
NSTEP3 = int((Rotdeg3-Rotdeg2)/STEP3)+1
SumNS = int((NSTEP1+NSTEP2+NSTEP3)*2-1)
print "NSTEP1 = %d , NSTEP2 = %d , NSTEP3 = %d , SumNS = %d" % ( NSTEP1 , NSTEP2 ,,→NSTEP3 , SumNS)
angle = []

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sa=200
print "Initial Status", statuscurrent_pos = int(status.split(",")[0])
if current_pos != 0:
gsc02.move(-current_pos, 0) # reset position
time.sleep(7) # 15

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gsc02.move(-Rotdeg3*DEG, 0) # go to -Rotdeg3 degree
for i in range(8): # 10
time.sleep(1)status = gsc02.getStatus()print "Current Status", status
if status == ’%d,%d,K,K,R’ % (-Rotdeg3*DEG , -Rotdeg3*DEG): # oldver is
,→
40000
break

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# edited by Tan
sum_all_1, sum_all_2 = [], []Rotation measurement script

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mean_all_1, mean_all_2 = [], []err_all_1, err_all_2 = [], []RMS_1, RMS_2 = [], []

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li_me_1 = []# li_me = list means,
li_me_2 = []

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dt

= (1./2.)

# ns

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# wavelength’s
if length == 310:
ns
= 0
# chousei you
tstart = 240.
# Signal starttend= tstart + ns+100. # Signal end
pend= tstart - 10
# Pedestal startpstart = pend
- ns-100. # Pedestal end
p_start = int(pstart/dt); # pedestal start cellp_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

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tstart_mo = tstart- 0.
# Signal start - monitor
tend_mo= tend - 0.
# Signal end - monitor
pend_mo= pend - 0.
# Pedestal start - monitor
pstart_mo = pstart- 0.
# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

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elif length == 365:
pstart = 80.
# Pedestal startpend= pstart + 120.
# Pedestal end
tstart = 210.
# Signal starttend= tstart + 120.
# Signal end
p_start = int(pstart/dt); # pedestal start cellp_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

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tstart_mo = tstart# Signal start - monitor
tend_mo= tend# Signal end - monitor
pend_mo= pend# Pedestal start - monitor
pstart_mo = pstart# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

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elif length == 465:
ns
= 35
tstart = 210.

# Signal startRotation measurement script

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tend
= tstart + ns+20. # Signal end
pend= tstart - 10
# Pedestal startpstart = pend
- ns-20. # Pedestal end
p_start = int(pstart/dt); # pedestal start cellp_end
= int(pend/dt);# pedestal end cellt_start = int(tstart/dt); # signal start cellt_end
= int(tend/dt);# signal end cell

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tstart_mo = tstart- 5.
# Signal start - monitor
tend_mo= tend - 5.
# Signal end - monitor
pend_mo= pend - 5.
# Pedestal start - monitor
pstart_mo = pstart- 5.
# Pedestal end - monitor
p_start_mo = int((pstart_mo)/dt); # pedestal start cell - monitor
p_end_mo= int((pend_mo)/dt);# pedestal end cell - monitor
t_start_mo = int((tstart_mo)/dt); # signal start cell - monitor
t_end_mo= int((tend_mo)/dt);# signal end cell - monitor

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else :
print ’Need to change the pesdetal and signal range with wavelength.’print length

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#li_err = [] # li_me = list means, li_err = list errors
txtfile = open("%strial_all.txt" % ( fin_dir),"a") #f = open("%strial_all.txt" % ( fin_dir),"r+b")i = 0lines = f.readlines()
for i,line in enumerate(lines):#type_, average= line.split("")
type_ = line.split("-")[0]typ= line.split(" ")[0]
if type_ == "LG":print "Measurement has already done"
sys.exit()
if typ == "Mask-Mo":
mmo = float(line.split(" ")[2])
print "Mask-Mo:", mmo

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f.close()

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# lg gain graphh_lg0 = ROOT.TGraphErrors()
h_lg0.SetName("ras")h_lg1 = ROOT.TGraphErrors()
h_lg2 = ROOT.TGraphErrors()
h_lg3 = ROOT.TGraphErrors()

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# pedestal & signal range’s graphh_range = ROOT.TH1D("test","test",560,-30.,530)
h_range.SetAxisRange(-50,350,"Y")ma,z = int(0), int(0)for ma in range (100):

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Rotation measurement script

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for z in range (int(pstart),int(pend+1)):
h_range.Fill(z)for z in range (int(tstart),int(tend+1)):
h_range.Fill(z)

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# pedestal & signal range’s graph - monitor
h_range_mo = ROOT.TH1D("test2","test2",560,-30.,530)
h_range_mo.SetAxisRange(-50,350,"Y")ma,z = int(0), int(0)for ma in range (100):for z in range (int(pstart_mo),int(pend_mo+1)):
h_range_mo.Fill(z)for z in range (int(tstart_mo),int(tend_mo+1)):
h_range_mo.Fill(z)

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c1 = ROOT.TCanvas(number, number, 0,0,400,800)
c1.Divide(1,2)
c2 = ROOT.TCanvas("lg", "lg", 0,0,800,600)#c1.cd(1)

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#ROOT.TH1D *h[4]#h[Ntrial] = ROOT.TH1D("hist_%01d" % (Ntrial),"hist_%01d" % (Ntrial),560,-30.,530)

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i=0
# end
brk=0
trial = 0
a = 1 # ratio 1 (for +side) or -1 (for -side)

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for trial in range(Ntrial):
j=0
while (j <SumNS):#for j in range(SumNS): # (+)side . example: from -40 -> 40
time.sleep(2.5)
c1.cd(1)print "\nTrial : %d, j= %d, current angle: %.1f deg, St : %s" %,→(trial,j,current_angle, gsc02.getStatus())
time.sleep(0.5)
fname="%s/trial%04d_%.1fdeg.dat" % (DIR, trial, current_angle)
fout_name = "%s/trial%04d_%.1fdeg.root" % (DIR, trial, current_angle)
os.system("%s %f %d %s true 2." % (DRS_EXE, THD, NEVE, fname))
vfile.write("%d %s %f %s\n" % (time.time(), fname, gpd.getVoltageOutput(1),,→gsc02.getStatus()))
vfile.flush()

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# save to ROOT file
f = open(fname)lines = f.readlines()
nlines = len(lines)
t1 = -1e10
for i, line in enumerate(lines):111Rotation measurement script

112

t, v1, v2 = line.split(" ")t = float(t)if i == 0:
tstart = t
if t1 > t:tend = t1
f.close()
break
else:
t1 = t

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,→
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,→
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,→
,→
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,→
,→

nsamples = inevents = nlines/nsamples
f = open(fname)lines = f.readlines()
fout = ROOT.TFile(fout_name, "create")
for i, line in enumerate(lines):
if i%nsamples == 0:
if NEVE <1000:
hist1 = ROOT.TH1D("hist1_%03d" % (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
hist2 = ROOT.TH1D("hist2_%03d" % (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
else:
hist1 = ROOT.TH1D("hist1_%04d" % (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)
hist2 = ROOT.TH1D("hist2_%04d" % (i/nsamples), ";Time (ns);Voltage(mV)", nsamples, tstart - (tend - tstart)/(nsamples - 1)/2., tend + (tend tstart)/(nsamples - 1)/2.)

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t, v1,v2 = line.split(" ")t = float(t)v1 = float(v1)v2 = float(v2)hist1.Fill(t, v1)
hist2.Fill(t, v2)

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if i%nsamples == nsamples - 1:
hist1.Write()hist2.Write()

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# calculate
sig1,sig2 = ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)
charge1, charge2 = ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)
pes1,pes2= ROOT.TH1D("", "", 100, 0, 0),ROOT.TH1D("", "", 100, 0, 0)#c1.cd(trial+1)
for i in range(NEVE):
if NEVE <1000:
h1 = fout.Get("hist1_%03d" % i)

Rotation measurement script

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else:
h1 = fout.Get("hist1_%04d" % i)
if not h1:
break# draw all signals to 1 graphif (i ==0):
h1.SetAxisRange(-50,350,"Y")h1.Draw()
else:
h1.Draw("SAME")# total sum of pedestal from 80 to 180
P_1 = h1.Integral(p_start,p_end)
pes1.Fill(P_1)

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# total sum of signal from 200 to 300
S_1 = h1.Integral(t_start, t_end)
sig1.Fill(S_1)

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s_p_1 = S_1 - P_1
charge1.Fill(s_p_1)
h_range.SetLineColor(2)h_range.Draw("SAME")
c1.Update()

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# calculate signal of Monitor
c1.cd(2)for i in range(NEVE):
if NEVE <1000:
h2 = fout.Get("hist2_%03d" % i)else:
h2 = fout.Get("hist2_%04d" % i)
if not h2:
break# draw all Monitor’s signals to 1 graphif (i ==0):h2.SetAxisRange(-50,350,"Y")h2.Draw()
else:
h2.Draw("SAME")# total sum of pedestal from 80 to 180
P_2 = h2.Integral(p_start_mo,p_end_mo)
pes2.Fill(P_2)

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# total sum of signal from 200 to 300
S_2 = h2.Integral(t_start_mo, t_end_mo)
sig2.Fill(S_2)

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s_p_2 = S_2 - P_2
charge2.Fill(s_p_2)
h_range_mo.SetLineColor(2)h_range_mo.Draw("SAME")
c1.Update()

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Rotation measurement script

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328

# calculate LG (or Mask) value:
mean_pes_1 = pes1.GetMean()
err_pes_1 = pes1.GetMeanError()
mean_sig_1 = sig1.GetMean()
err_sig_1 = sig1.GetMeanError()
mean_1= charge1.GetMean()err_1= charge1.GetMeanError()err_all1 = math.sqrt(pow(err_sig_1,2)+pow(err_pes_1,2)) # total error

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,→
,→
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,→

mean_1 = mean_sig_1 - mean_pes_1
print "%.1f
deg: mean_pes= %.1f+/-%.1f mean_sig= %.1f+/-%.1f
mean2=%.1f +/- %.1f" % (current_angle,mean_pes_1, err_pes_1, mean_sig_1, err_sig_1,
mean_1, err_all1)#print "%.1f deg:mean= %.1f +/- %.1f" % (current_angle, mean, err)
if (current_angle== -22.5) and (trial ==0) :ras_now= mean_1
if (abs(current_angle)<= 22) and (abs(ras_now - mean_1) >sa ) :os.remove(fname)os.remove(fout_name)brk =brk+1
if brk == 1:
sa = sa*2
if brk == 2:
sa = sa*2
if brk == 3:
sa = sa*2
if brk == 4:
sa = sa*2
continue
brk=0
sa=200err_all_1.append(err_all1)
ras_now= mean_1
li_me_1.append(mean_1)
if trial == 0 and Ntrial == 4:
sum_all_1.append(mean_1)
elif trial == 0 and Ntrial == 5:
sum_all_1.append(0)elif trial ==2 or trial ==4:
sum_all_1[j]= sum_all_1[j]+ mean_1
elif trial == 1 or trial ==3:
sum_all_1[SumNS-1-j]= sum_all_1[SumNS-1-j]+ mean_1
if Ntrial!= 1:
txtfile.write("LG_%d %.1f %f %f\n" % ( trial, current_angle , mean_1,
err_all1))

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#draw LG gain
if trial==0:
h_lg0.SetPoint(j , current_angle , mean_1)
h_lg0.SetPointError(j,EX, err_all1)
h_lg0.SetLineColor(trial+1)

Rotation measurement script115

c2.cd()
if j == 0:
h_lg0.Draw("AP")else :
h_lg0.Draw("SAME")
elif trial==1:
h_lg1.SetPoint(j , current_angle , mean_1)
h_lg1.SetPointError(j,EX, err_all1)
h_lg1.SetLineColor(trial+1)
c2.cd()
h_lg1.Draw("SAME")
elif trial==2:
h_lg2.SetPoint(j , current_angle , mean_1)
h_lg2.SetPointError(j,EX, err_all1)
h_lg2.SetLineColor(trial+1)
c2.cd()
h_lg2.Draw("SAME")
elif trial==3:
h_lg3.SetPoint(j , current_angle , mean_1)
h_lg3.SetPointError(j,EX, err_all1)
h_lg3.SetLineColor(trial+1)
c2.cd()
h_lg3.Draw("SAME")
else:
print "debug_draw"
c2.Update()

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,→
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# calculate Monitor’s value:
mean_pes_2 = pes2.GetMean()
err_pes_2 = pes2.GetMeanError()
mean_sig_2 = sig2.GetMean()
err_sig_2 = sig2.GetMeanError()
mean_2= charge2.GetMean()err_2= charge2.GetMeanError()err_all2 = math.sqrt(pow(err_sig_2,2)+pow(err_pes_2,2)) # total error
err_all_2.append(err_all2)
mean_2 = mean_sig_2 - mean_pes_2
print "%.1f-Mo deg: mean_pes= %.1f+/-%.1f mean_sig= %.1f+/-%.1f
mean2=%.1f +/- %.1f" % (current_angle,mean_pes_2, err_pes_2, mean_sig_2, err_sig_2,
mean_2, err_all2)#print "%.1f deg:mean= %.1f +/- %.1f" % (current_angle, mean, err)

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li_me_2.append(mean_2)
if trial == 0:
sum_all_2.append(mean_2)
elif trial ==2:
sum_all_2[j]= sum_all_2[j]+ mean_2
elif trial == 1 or trial ==3:
sum_all_2[SumNS-1-j]= sum_all_2[SumNS-1-j]+ mean_2

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if Ntrial != 1:

Rotation measurement script

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,→
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txtfile.write("LG-Mo_%d %.1f %f %f\n" % (trial, current_angle , mean_2,
err_all_2[j]))angle.append(current_angle)
fout.Close()f.close()# finish saving to ROOT file

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if j == SumNS-1:
print ’break the loop.’a *=-1break
if a == 1:
if -Rotdeg3 <= current_angle < 0 :if -Rotdeg3 <= current_angle < -Rotdeg2 :gsc02.move(STEP3*DEG, 0) # increase by STEP3 deg
current_angle += STEP3#time.sleep(0.5)
elif -Rotdeg2 <= current_angle < -Rotdeg1 :gsc02.move(STEP2*DEG, 0) # increase by STEP2 deg
current_angle += STEP2#time.sleep(0.5)
elif -Rotdeg1 <= current_angle < 0 :gsc02.move(STEP1*DEG, 0) # increase by STEP1 deg
current_angle += STEP1#time.sleep(0.5)
else :
print "debug1"
sys.exit()
time.sleep(0.5)

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elif 0 <= current_angle <= Rotdeg3 :if 0 <= current_angle < Rotdeg1 :gsc02.move(STEP1*DEG, 0) # increase by STEP1 deg
current_angle += STEP1#time.sleep(0.5)
elif Rotdeg1 <= current_angle < Rotdeg2 :gsc02.move(STEP2*DEG, 0) # increase by STEP2 deg
current_angle += STEP2#time.sleep(0.5)
elif Rotdeg2 <= current_angle <= Rotdeg3 :gsc02.move(STEP3*DEG, 0) # increase by STEP3 deg
current_angle += STEP3#time.sleep(0.5)
else :
print "debug2"
sys.exit()
time.sleep(0.5)
else :
print "debug3"
sys.exit()

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Rotation measurement script

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if a == -1:
if 0 < current_angle <= Rotdeg3 :#if -Rotdeg3 <= current_angle < 0 :if Rotdeg2 < current_angle <= Rotdeg3 :gsc02.move(-STEP3*DEG, 0) # decrease by STEP3 deg
current_angle -= STEP3#time.sleep(0.5)
elif Rotdeg1 < current_angle <= Rotdeg2 :gsc02.move(-STEP2*DEG, 0) # decrease by STEP2 deg
current_angle -= STEP2#time.sleep(0.5)
elif 0 < current_angle <= Rotdeg1 :gsc02.move(-STEP1*DEG, 0) # decrease by STEP1 deg
current_angle -= STEP1#time.sleep(0.5)
else :
print "debug4"
sys.exit()
time.sleep(0.5)

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elif -Rotdeg3 <= current_angle <= 0 :if -Rotdeg1 < current_angle <= 0 :gsc02.move(-STEP1*DEG, 0) # decrease by STEP1 deg
current_angle -= STEP1#time.sleep(0.5)
elif -Rotdeg2 < current_angle <= -Rotdeg1 :gsc02.move(-STEP2*DEG, 0) # decrease by STEP2 deg
current_angle -= STEP2#time.sleep(0.5)
elif -Rotdeg3 <= current_angle <= -Rotdeg2 :gsc02.move(-STEP3*DEG, 0) # decrease by STEP3 deg
current_angle -= STEP3#time.sleep(0.5)
else :
print "debug5"
sys.exit()
time.sleep(0.5)
else :
print "debug6"
sys.exit()
j=j+1

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if trial == Ntrial-1:
print ’The Measurement has just finished.’
k=0
for k in range(SumNS):
if Ntrial == 4:
mean_all_1.append(sum_all_1[k]/Ntrial)
if Ntrial == 5: # error for 1 run
mean_all_1.append(sum_all_1[k]/4)
sum_pow_1 = 0

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Rotation measurement script

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if Ntrial == 1: # error for 1 run
RMS1 = err_all_1[k]elif Ntrial == 5:for i in range(1,Ntrial):
if i== 2 or i ==4:z = k + SumNS*i
if i == 1:z = SumNS*2 -1 - k
if i == 3:z = SumNS*4 -1 - k#print li_me_1[z], mean_all_1[k]sum_pow_1 += pow ( (li_me_1[z]-mean_all_1[k]) ,2)
RMS1 =math.sqrt(sum_pow_1/4)

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,→

else: # error for 4 runs
for i in range(Ntrial):
if i ==0 or i== 2:z = k + SumNS*i
if i == 1:z = SumNS*2 -1 - k
if i == 3:z = SumNS*4 -1 - k#print li_me_1[z], mean_all_1[k]sum_pow_1 += pow ( (li_me_1[z]-mean_all_1[k]) ,2)
RMS1 =math.sqrt(sum_pow_1/Ntrial)
RMS_1.append(RMS1)
txtfile.write("LG %.1f %f %f\n" % ( angle[k] , mean_all_1[k], RMS_1[k]) )print ’%.1f deg: Mean_all = %.1f +/-%.1f’ % (angle[k], mean_all_1[k],RMS_1[k])557mean_all_2.append(sum_all_2[k]/Ntrial)
sum_pow_2 = 0
if Ntrial == 1:
RMS2 = err_all_2[k]else:for i in range(Ntrial):
if i ==0 or i== 2:z = k + SumNS*i
if i == 1:z = SumNS*2 -1 - k
if i == 3:z = SumNS*4 -1 - k#print li_me_2[z], mean_all_2[k]sum_pow_2 += pow ( (li_me_2[z]-mean_all_2[k]) ,2)
RMS2 = math.sqrt(sum_pow_2/Ntrial)
RMS_2.append(RMS2)
txtfile.write("LG-Mo %.1f %f %f\n" % ( angle[k] , mean_all_2[k], RMS_2[k])

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,→

)

,→

print ’%.1f deg: Mean_Monitor = %.1f +/-%.1f\n’ % (angle[k],mean_all_2[k], RMS_2[k])

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#sys.exit()

Rotation measurement script

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txtfile.close()current_pos = int(status.split(",")[0])#print current_pos, current_angle
if current_angle != 0:
gsc02.move(-current_angle*400, 0) # reset position

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# calculate RAS
f = open("%strial_all.txt" % ( fin_dir),"r+w") #i = 0lines = f.readlines()
count = 0lg, lg_err,angle = [], [],[]
lg_mo, lg_mo_err = [], []for i,line in enumerate(lines):
type_ = line.split(" ")[0]deg= line.split(" ")[1]
if type_ =="Mask":
m = float(line.split(" ")[2])# maskm_err = float(line.split(" ")[3])# mask’s error
count += 1
elif type_ =="Mask-Mo":
m_mo = float(line.split(" ")[2])# mask’s monitor
m_mo_err = float(line.split(" ")[3])# mask’s monitor error
count += 1
elif type_ =="LG":#print line
angle.append( float(line.split(" ")[1]))lg.append(
float(line.split(" ")[2]))lg_err.append(float(line.split(" ")[3]))# deg, LG , LG’s error
count += 1
elif type_ =="LG-Mo":#print line
lg_mo.append(
float(line.split(" ")[2]))lg_mo_err.append(float(line.split(" ")[3]))# deg, LG’s monitor , LG’s,→
monitor error
count += 1
elif type_ == "RAS" or type_ == "RAS-Mo":del lines[i-1]#print lg_mo#print lg_mo_err
if count == 2 :print ’No LG’elif count == (2 + SumNS*2):
for i in range (SumNS):
ras = lg[i] /(m * math.cos(angle[i]/180*math.pi) *3.7352) *100
ras_err = ras * math.sqrt( pow( m_err/m ,2) + pow( lg_err[i]/lg[i] ,2) )#print ’%.1f :’ % (angle[i])#print ’LG= %.1f +/- %.1f ; LG-Mo= %.1f +/- %.1f’ % (lg[i],lg_err[i],,→lg_mo[i], lg_mo_err[i])119Rotation measurement script

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#print ’
Mask = %.1f +/- %.1f ; Mask-Mo = %.1f +/- %.1f’ % ( m,m_err, m_mo,
m_mo_err)
print ’%.1f RAS= %.1f +/- %.1f’ % (angle[i], ras, ras_err)
f.write("RAS %.1f %f %f\n" % ( angle[i], ras, ras_err))

,→
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ras_mo = lg[i] * m_mo / (m * lg_mo[i] *math.cos(angle[i]/180*math.pi) * 3.7352)*100
ras_mo_err = ras_mo * math.sqrt( pow( m_err/m ,2) + pow( m_mo_err/m_mo ,2) +pow(,→
lg_err[i]/lg[i] ,2) + pow( lg_mo_err[i]/lg_mo[i] ,2))#print ’LG = %.1f +/- %.1f ; Mask = %.1f +/- %.1f’ % (lg,lg_err, m, m_err)
print ’RAS-Mo = %.1f +/- %.1f’ % ( ras_mo, ras_mo_err)
f.write("RAS-Mo %.1f %f %f\n" % ( angle[i] , ras_mo, ras_mo_err))#elif count == 0:
else:
print "count = %d :Sthing’s wrong!" % (count)f.close()#txtfile.close()
,→

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# reset position
current_pos = int(status.split(",")[0])
if current_pos != 0:
gsc02.move(-current_pos, 0) # reset position
sys.exit()

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