CTA 報告 215：

小口径望遠鏡の開発状況
奥村曉 A、B、C
重谷優斗 A、河原崎琉 A、田島宏康 A、B、C、バンソンヒョン A、
古田和浩 A、他 CTA 共同研究者
A 名古屋大学 宇宙地球環境研究所（ISEE）
B 名古屋大学 素粒子宇宙起源研究所（KMI）
C 名古屋大学 南半球宇宙観測研究センター

oxon@mac.com

Cherenkov Telescope Array (CTA)
cherenkov
telescopearray

Gabriel Pérez Diaz (IAC)/Marc-André Besel (CTAO)/ESO/ N. Risinger (skysurvey.org)

Next-generation ground-based gamma-ray observatory with ×10 better sensitivity
Covering 20 GeV–300 TeV with 3 telescope designs
High angular resolution of 0.02–0.05° above 10 TeV2

Cherenkov Telescope Array (CTA)
Very-high-energy
gamma rays

Electromagnetic Cascade

Atmospheric Cherenkov Photons∝ Gamma-ray Energy(300–600 nm, 5–20 ns)

R ~ 150 m
K. Bernlöhr
3

Cherenkov Telescope Array (CTA)

Large-Sized Telescope (LST)- Dia. : 23 m
- Energy : 20–150 GeV- N Tel : 4 @ North, 4 @ South

Medium-Sized Telescope (MST)- Dia. : 12 m
- Energy : 150 GeV–5 TeV- N Tel : 15 @ North, 25 @ South

Small-Sized Telescope (SST)- Dia. : 4 m- Energy : 5–300 TeV- N Tel : 0 @ North, 70 @ South4CTA Northern & Southern Sites (Initial Configuration)
CTA South: Paranal, Chile
CTA North: La Palma, Spain

Image Credit: G. Pérez, IAC, SMM

LSTMSTSST2 km

Wide energy coverage of 20 GeV–300 TeV with three telescope sizes
Spread over ~5 km2 area to catch Cherenkov photons anywhere in the circle
Construction phase to start with 4 LSTs + 9 MSTs (north) and 14 MSTs + 37 SSTs (south)5

High-energy Frontier by CTA SSTs (Initial Configuration)

SST Core Energy Band

5–300 TeV50 h
LST100 hMST200 h
400 h

Covering up to 100–300 TeV is a key for PeVatron searchLong observations of selected candidates (e.g., Gal. Center)
Observations under bright moon conditions will double the duty cycle6Small-Sized Telescopes (SSTs)
Credit: G. Pérez, IAC, SMM

2m

Old SST rendering

4m

In 2019, SST “harmonization” process concluded
to select this design as the nal SST design
Schwarzschild–Couder optical system‣

4 m aspherical primary mirrors (segmented)‣2 m monolithic secondary mirror (monolithic)‣~0.15° PSF diameter over ~9° FOV

Compact focal-plane camera‣

2048 SiPM pixels to form 300 mm focal plane‣

32 × 64-ch camera modules with dedicated ASICs‣Large contributions from Nagoya Universityfi7

Status of the SST Optical System
1st Prototype on Mt. Etna, Sicily, Italy

2nd Prototype at Teide Obs., Tenerife, Spain
Credit: ASTRI, INAF

Giro+ 2017

6 mm
SiPM Pixel

2 km

The optical performance of the Schwarzschild–Couder system validated“ASTRI mini-array" (9 SST-like systems) to be built at Teide Observatory
Optics and array control will be tested and validated before SST construction in ~20268History of the SST Camera
1st Prototype with MAPMTs (First Light 2015)

2nd Prototype with SiPMs (First Light 2019)

The current SST camera concept started around 2012
Two prototypes succeeded in rst lights in 2015 and 2019
SiPMs to be used in the nal SST camera designfifi

932 × 64-ch SiPMs

Light-tightdoors

UV transparent
64-ch SiPM
at window(Hamamatsu S14521)

300 mmReadout
modulesSlowcontrolboard
570 mmPower
supplyHeat exchanger

Backplane

The same concept: 32 × 64-ch SiPMs to form the spherical focal plane, read andtriggered by dedicated ASICs (TARGET series), and controlled by backplane
After the experience of two prototypes, the design is being nalized now10fifl(Almost) Final Design

Camera Module
64-ch SiPM
Hamamatsu S14521-1720
6 × 6 mm2, 50 µm APD
Typ. breakdown = 38 V

To backplane
ASICs- Sampling- Digitization- First level trigger
Bias board
Preampli er board

Started with the rst TARGET ASIC (16-ch sampling and trigger), and 64-ch MAPMTs in 2009
Latest module uses 4 × sampling ASIC (CTC) and 4 × trigger ASIC (CT5TEA)
UV-sensitive and uncoated low-optical-crosstalk 64-ch SiPMs
fifi

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Quarter Camera @ MPIK, Heidelberg

Quarter camera will have only 8 camera modules (512 of 2048 pixels)
Mechanical, thermal, and electrical tests started this summer in parallel to stand-alone module tests
Tests and debugging to nish this year, then a full camera ( rst camera) will be built in 2024
Mounting test on a telescope to be done at the Tide Observatory in October
fifi

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Tentative Schedule
2023

2024

2025

2026

2027

2028

Finalize Camera DesignQuarter Camera Tests
1st to 5th Cameras to be built and tested
Procurement of mass production parts
Mass production of 6th to 42nd cameras

Test observations with initial cameras
CTA Southern site preparation

Quarter camera in 2023–2024, 1st camera in 2024–2025, …
Once the 1st camera is ready, we will start test observations in 2025
Must produce and test a new camera a month from 2025
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CTA Small-sized Telescopes (SSTs) is a key instrument for
PeVatron search in 5–300 TeV
Complementary with array-type surface detectors‣

Better angular and energy resolutions‣

Competing exposure time by pointing and moon-lightobservations

The nal SST camera and telescope designs are almost
nishedQuarter camera and modules are under tests
First camera and mass production are expected in the next
few years
14fifi

Summary