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 E2014 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
Large-Sized
Telescope (LST)

Medium-Sized
Telescope (MST)

4@North + 4@SouthD = 23 m
FOV = 4.5°E = 20 GeV – 1 TeV~24@N + ~15@S
D = 12 m
FOV = 8°E = 100 GeV – 10 TeV

North

Schwarzschild-Couder
Telescope (SCT)

Small-Sized
Telescope (SST)~24@S
D = 9.6 m
FOV = 8°E = 100 GeV – 10 TeV

GCT~35@S
ASTRI~35@SDavis-Cotton ~20@S
D ~4 m
FOV ~9°E = 1 TeV – 300 TeV

South

1 km

LSTMSTSCTSST

3 km
Array Layout Examples© G. Pérez, IAC, SMM

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 t
PSF of the light distribution in the focal plane of OSs.

Schwarzschild-Couder (SC) Optical System
5Secondary

443

Cross − sectional plane X [m]Cross − sectional plane X [m]3Primary

2
10

Camera−1−2−3−4−5Vassiliev et al. (2007)

521

9.7 m

00.78 m5.6 m

−1−2−3−4−1012345678
Cross −sectional plane Z [m]91011−5−1012345678
Cross −sectional plane Z [m]91011First proposed for IACTs in 2007Primary + secondary mirrors

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 (rigdegrees.

Widefield-of-viewof ~8°
Both theprimaryand secondary
mirrors can be segment
to reduce
theangularcost of the
optical system.
High
resolutionof ~4’A possible arrang
ment of mirror facets, as ‘‘petals’’, is shown in Fig. 7. Th
Small
plate
scale ofof~0.6’/mm
schemehas theadvantage
requiring a minimal numbof Will
diﬀerent
surfaceinshapes.
A study
be usedSCT andSSTof the tolerancealignment and positioning of mirrors is beyond the scoof Small
this paper.
Nevertheless,our experience
with the simul
angularresolution
and widetions
suggests
thatrequirements
are stricter than thoFOV
bringusthe
highersensitivity
applied to the H.E.S.S. and VERITAS optical systems. Th
3

The SCT Optical System and Photodetectors Mirrors’ quality andmisalignment are not included
Ray-tracing Simulation
with ROBASTθ = 1.5°

3 mm × 3 mm

Analog Sum of4 pixels

θ = 2.5°

θ = 3.5°

θ = 4.0°

Pixel = 6 mm

θ = 3.0°

S12642-0404PA-50

θ = 2.0°

The typical PSF size of SCT is~6 mm (~4’)
Compact and modular camera frontend electronics with small-pixel
photodetectors needed
Silicon photomultipliers (SiPMs orMPPCs) or MAPMTs match the pixelsize
4

TARGET (TeV Array Readout with GSa/s sampling and Event Trigger)
TARGET ASIC (designed by G. Varner @ U. Hawaii)- 16 channels readout- 1 GSa/s sampling
HV Module- 16-us long buﬀer- Trigger circuit

Fiber or LVDS I/FFPGATARGET ASIC × 4

MAPMT → MPPCSCT Camera- 177 modules- 11,328 channels

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 MPPCs
5

SST-GCT (Gamma Compact Telescope) and CHEC
θ = 0.0°

θ = 1.0°

θ = 2.0°

Pixel = 6 mm
θ = 3.0°

θ = 4.0°

ROBAST Simulation
by Cameron Rulten(Obs. Paris)

CHEC-M- 32 modules- 2,048 channels

One of three SST designs, basedon 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

Development of TARGET ASICs

詳細は河島講演 21pSG-5

TARGET 1 (see Bechtol et al. 2012)
The 1st generation of TARGET produced in 2008
Limited bandwidth of ~150 MHz at 3 dB
High cross talk of ~4%
Saturation for high amplitude inputs(TARGET 2, 4, and) TARGET 5
Produced 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
circuit
Narrow dynamic range and non-linearity of the transfer function

TARGET 7
Produced in 2013 for SiPMs (CHEC-S and SCT)
Much better linearity
The threshold issue still remains (even worse)
New TARGET design will be submitted in 2014
7

TARGET-5 Transfer Function
ADC

Channel 07
4000
3500

An Example TARGET 5 Transfer Function

3000
2500
2000
1500
1000

Noise (mV)

500
0
1.5
1
0.5
001 mV
0.5

0.5 V

11.5

22.5
2.1 VVped (V)The non-linearity of TARGET 5 transfer functions made our calibration processmore diﬃcult, while the noise level was low enoughDynamic range of ~1.6 (V) was smaller than our requirement (> 10 bits)
8

TARGET 7 Transfer Function
by J. Vandenbrouckeat Wisconsin

yr
inar
e
V

miler
Py

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)
9

S-Curve Shape Changes in Sampling Phase (TARGET 5)
χ2 / ndf
588.7 / 5
p078.62 ± 0.005219
p11.224 ± 0.005034

1.41.2

2

trigger effiencytrigger effiency

Phase
Delay
0 ns = 0 nsby Taka Kawashima & Luigi Tibaldo
χ / ndf
3.546e+04 / 20
Phase
Delay
26 ns = 26 ns
p0
1.2
10.8

0.8

σ = 1.2 mV

0.4

0.2

0.2

6065

TARGET Block diagram

70

75

80

85

90

95
100
pulse height(mV)

σ ~ 4 mV

0.6

0.4

055

p1

1.4

10.6

66.18 ± 0.01472
3.654 ± 0.01002

055

60

65

70

75

80

85

90

95
100
pulse height(mV)Sampling arrays of a 64-ns
periodThreshold and trigger noisechange as the trigger timing
shifts in the sampling arrays
10

The First Mass Production of Modules for CHEC-M

Produced by SLAC withTARGET 5 ASICs
Tested at SLAC in
March and April 2014
Delivered to Universityof Leicester and tested
again in July
HV moduleTrigger functionality
Transfer functions
Sampling stability
Sinusoidal input
11

CHEC-M with a Prototype of Backplane Board
DAQ Boards
Support Frames
in a Huge Dark Box

ProtoBackplane~40 cmLED Flasher
for Calibration
12

CHEC-M with a Prototype of Backplane Board13

16 × 16 MPPC with Thin-Film Coating
16 × 3.2 mm = 51.2 mm3 mm0.2-mm Gap
50-µm Cells withThin-Film Coating
S12642-1616 series (Thin film coating)

3.0 mm × 3.0 mm(with 0.2-mm Gaps)

䕔 Spectral response

Analog Sum of 4 Chs
Higher transparency for < 350nm region

8

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

Plans in 2014
TARGET
Finish evaluation and tuning of TARGET 7
Submit a new TARGET design that has separated trigger andsampling ASICs
Produce TARGET 7 camera modules for proto-SCT and CHEC-SCHEC
Software development of DAQ and slow control
Long term test of CHEC-M in a dark box
Assemble CHEC-S

MPPC
Evaluation of the thin-film coating MPPCs
15