CTA 報告 85:Schwarzschild-Couder 型望遠鏡用の

焦点面カメラの開発状況

奥村 曉 A, B , 河島 孝則 A , 田島 宏康 A , 日高 直哉 A

J. Hinton B , R. White B , S. Funk C , L. Tibaldo C , J. Vandenbroucke D , G. VarnerE

他 The CTA Consortium

名大 STE 研 A , Univ. Leicester B , SLAC C , Univ. Wisconsin D , Univ. Hawaii E

2014 年 9 月 18 日日本物理学会 2014 年秋季大会 @ 佐賀大学

CTA: A Mixed Array of Different Telescopes

© G. Pérez, IAC, SMM

SouthNorth

LSTMSTSCTSST

1 km

3 km

Small-Sized Telescope (SST) GCT ~35@S ASTRI ~35@S Davis-Cotton ~20@S D ~4 m FOV ~9° E = 1 TeV – 300 TeV

Large-Sized Telescope (LST) 4@North + 4@South D = 23 m FOV = 4.5° E = 20 GeV – 1 TeV

Medium-Sized Telescope (MST) ~24@N + ~15@S D = 12 m FOV = 8° E = 100 GeV – 10 TeV

Schwarzschild-Couder Telescope (SCT) ~24@S D = 9.6 m FOV = 8° E = 100 GeV – 10 TeV

Array Layout Examples

Both the primary and secondary mirrors can be segmentedto reduce the cost of the optical system. A possible arrange-ment of mirror facets, as ‘‘petals’’, is shown in Fig. 7. Thisscheme has the advantage of requiring a minimal numberof different surface shapes. A study of the tolerance ofalignment and positioning of mirrors is beyond the scopeof this paper. Nevertheless, our experience with the simula-tions suggests that the requirements are stricter than thoseapplied to the H.E.S.S. and VERITAS optical systems. Theuse of automated alignment and calibration systems willlikely be required, e.g. [29].

0 1 2 3 4 5 6 70

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Field angle [deg]

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ectiv

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ea [m

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2×

max

{ R

MS

sagi

ttal, R

MS

tang

entia

l }

[arc

min

] Conf 1Conf 2Conf 3

Fig. 5. (Left) The effective area as a function of field angle for the three configurations of OS summarized in Table 2. (Right) The effective diameter of thePSF of the light distribution in the focal plane of OSs.

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[m]

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Cross −sectional plane Z [m]

Cro

ss−

sect

iona

l pla

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[m]

Fig. 6. Illustration of incoming rays traced through the optical system to the focal plane for tangential rays at field angles of zero (left) and five (right)degrees.

Fig. 7. One possible scheme for faceting the primary and secondarymirrors. Four different facet types are used on the primary, three on thesecondary. Each facet is limited to an area less than approximately 0.45 m2

with no linear dimension larger than 1 m.

0 1 2 3 4 5 6 7 8−0.4−0.2

00.20.4

Focal plane X [deg]

Y [d

eg]

Fig. 8. Composite of images made in the focal plane of an aplanatictelescope with configuration OS 2 by rays at field angles between zero andseven degrees.

22 V. Vassiliev et al. / Astroparticle Physics 28 (2007) 10–27

Schwarzschild-Couder (SC) Optical System

First proposed for IACTs in 2007Primary + secondary mirrors

Wide field-of-view of ~8°High angular resolution of ~4’Small plate scale of ~0.6’/mm

Will be used in SCT and SSTSmall angular resolution and wide FOV bring us higher sensitivity

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Vassiliev et al. (2007)

Primary

Secondary

Camera 9.7 m 5.6 m0.78 m

The SCT Optical System and Photodetectors

The typical PSF size of SCT is~6 mm (~4’)

Compact and modular camera front-end electronics with small-pixel photodetectors needed

Silicon photomultipliers (SiPMs or MPPCs) or MAPMTs match the pixel size

4

θ = 1.5° θ = 2.0° θ = 2.5°

θ = 3.5°θ = 3.0° θ = 4.0°

Mirrors’ quality and misalignment are not included

Pixel = 6 mm

3 mm × 3 mm

Ray-tracing Simulationwith ROBAST

S12642-0404PA-50

Analog Sum of4 pixels

TARGET (TeV Array Readout with GSa/s sampling and Event Trigger)

Application specific integrated circuit (ASIC) for CTA

Developed TARGET 1 for concept validation (Bechtol et al. 2012)

TARGET 5 (w/ gain adjustment) for MAPMTs, TARGET 7 for MPPCs5

TARGET ASIC (designed by G. Varner @ U. Hawaii)- 16 channels readout- 1 GSa/s sampling- 16-us long buffer- Trigger circuit

TARGET ASIC × 4

FPGA

Fiber or LVDS I/F

MAPMT → MPPC

SCT Camera - 177 modules - 11,328 channels

HV Module

SST-GCT (Gamma Compact Telescope) and CHEC

One of three SST designs, based on SC optical system

Compact High-Energy Camera (CHEC) will be mounted

CHEC-M: Prototype with MAPMTs

CHEC-S: Prototype with SiPMs

Shares technologies with SCT6

ROBAST Simulationby Cameron Rulten(Obs. Paris)

θ = 2.0°

θ = 4.0°θ = 3.0°

θ = 1.0°θ = 0.0°

Pixel = 6 mm

CHEC-M - 32 modules - 2,048 channels

Development of TARGET ASICs

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TARGET 1 (see Bechtol et al. 2012)The 1st generation of TARGET produced in 2008Limited bandwidth of ~150 MHz at 3 dBHigh cross talk of ~4%Saturation for high amplitude inputs

(TARGET 2, 4, and) TARGET 5Produced in 2012 for MAPMTs (CHEC-M)Achieved ~400 MHz bandwidth and low cross talk of ~1%High trigger threshold (~25 mV, ~6 p.e.) due to noise from the sampling circuitNarrow dynamic range and non-linearity of the transfer function

TARGET 7Produced in 2013 for SiPMs (CHEC-S and SCT)Much better linearityThe threshold issue still remains (even worse)

New TARGET design will be submitted in 2014

詳細は河島講演 21pSG-5

AD

C

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Channel 07TARGET-5 Transfer Function

The non-linearity of TARGET 5 transfer functions made our calibration process more difficult, while the noise level was low enough

Dynamic range of ~1.6 (V) was smaller than our requirement (> 10 bits)8

An Example TARGET 5 Transfer Function

1 mV

0.5 V 2.1 V

TARGET 7 Transfer Function

Linearity was much improved from TARGET 5

Wider dynamic range from ~0.5 to ~2.5 (V) (~0.5 to ~2.1 for TARGET 5)

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by J. Vandenbrouckeat Wisconsin

Very Preliminary

pulse height(mV)55 60 65 70 75 80 85 90 95 100

trigg

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ffien

cy

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/ ndf 2χ 588.7 / 5p0 0.005219± 78.62 p1 0.005034± 1.224

/ ndf 2χ 588.7 / 5p0 0.005219± 78.62 p1 0.005034± 1.224

Delay 0 ns

pulse height(mV)55 60 65 70 75 80 85 90 95 100

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Delay 26 ns / ndf 2χ 3.546e+04 / 20

p0 0.01472± 66.18 p1 0.01002± 3.654

/ ndf 2χ 3.546e+04 / 20p0 0.01472± 66.18 p1 0.01002± 3.654

Delay 26 ns

TARGET Block diagram

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S-Curve Shape Changes in Sampling Phase (TARGET 5)

Sampling arrays of a 64-ns period

Threshold and trigger noise change as the trigger timing shifts in the sampling arrays

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σ = 1.2 mV σ ~ 4 mV

Phase = 0 ns Phase = 26 nsby Taka Kawashima & Luigi Tibaldo

The First Mass Production of Modules for CHEC-M

Produced by SLAC with TARGET 5 ASICsTested at SLAC in March and April 2014Delivered to University of Leicester and tested again in July

HV module

Trigger functionality

Transfer functions

Sampling stability

Sinusoidal input

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CHEC-M with a Prototype of Backplane Board

Proto-Backplane

DAQ Boards

Support Framesin a Huge Dark Box

LED Flasherfor Calibration

~40 cm

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CHEC-M with a Prototype of Backplane Board

16 × 16 MPPC with Thin-Film Coating

TSV MPPCs of 16 × 16 channels (S12642-1616PA-50) will be used for CHEC-S

Thin-film coating of 20-um thickness, expecting high PDE in UV (< 350 nm)

The first batch has been delivered to the UK in Aug 201414

3.0 mm × 3.0 mm(with 0.2-mm Gaps)

16 × 3.2 mm = 51.2 mm

Analog Sum of 4 Chs

0.2-mm Gap50-µm Cells withThin-Film Coating

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S12642-1616 series (Thin film coating)䕔 Spectral response

Higher transparency for < 350nm region

3 mm

Plans in 2014

TARGETFinish evaluation and tuning of TARGET 7Submit a new TARGET design that has separated trigger and sampling ASICsProduce TARGET 7 camera modules for proto-SCT and CHEC-S

CHECSoftware development of DAQ and slow controlLong term test of CHEC-M in a dark boxAssemble CHEC-S

MPPCEvaluation of the thin-film coating MPPCs

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