CTA 報告47:
CTA 大口径望遠鏡用分割鏡の開発:
LST Mirror System
手嶋政廣A，B，R.KrobotC，中嶋大輔A，馬場浩則D，加賀谷美佳D，片桐秀明D，峪中良介E，周小溪E，千川道幸E，野里明香E，柳田昭平D，山本常夏F，吉田龍生D，他CTA-Japan Consortium
東大宇宙線研A，Max-Planck-Inst. fuer Phys.B，Univ. of ErlangenC，茨城大理D，近畿大理E，甲南大理工F

Specifications/Requirements of LST


Diameter: 23m
Dish area: 407 m2
F/D = 1.2, F=28m
Dish profile: Parabolic
Permanent Active Mirror Control

FOV = 4.5 degrees, Pixel size = 0.1 degrees(1855ch camera)Fast rotation: <180 deg/20 sec

Dish profile: parabolic  isochronicity: <0.6
ns RMS
Camera sagging: < 1-2 pixels
Camera oscillation in wind gust: <8mm

– Active oscillation damping by LAPP IN2P3

Designed by MPI Munich and MERO

Deformation of mirror dish

Optical axis and permanent AMC (ActiveMirror Control)
Stars

SKY

LED

LED
OA-Lazer
PMT CAMERAMIR-Lazers

MIR-Lazers
LEDTarget
LED

IMAGE with HR CCD Camera





Define optical axis with the IR Laser beams
High precision inclinometer (a few arcsec)  zenith angle
HR CCD camera at the center of dish to monitor the optical axis and star field  pointing
direction in sky(Camera LED position) – (Optical axis Laser position)  camera sag(Mirror Laser positions) – (Optical axis Laser position)  misalignments of mirror directions

Mirrors and Actuators on Triangularspace frame
TriangularSpace frame

Actuators (2 axis free)
Universal Joints

Actuators (1 axis free)
LST-Mirrors:
1.5m (flat-flat)Hex shape
2m2 area
MST-Mirrors:
1.2m (flat-flat)Hex shapeMirror mounting scheme

Pads rear side of mirrors
Interface with AMC

Three pads of 150mm Φ at
1200mm diameter Circle
4 holes of 5mm Φ on each pad

Specifications for
LST Mirrors

Upgrade of Sputtering Chamber of2.8mΦ x 9 m at Sanko
92% of reflectivity

Multi (5 or 7) layer coating: Cr + Al + SiO2 + HfO2 + SiO2 (+HfO2 + SiO2)
In total it takes < 3hrs of process

Scratching tests forvapor and sputtering coats

Stylus R = 25 μm
Amp. of Osc. = 100μm
Scratch speed 10μm
Acc. of Force 50mN/60sec
Conclusion:
Sputtering coat is about
3-4 times stronger thanvapor coat
Al+MgF2 coat

Sputtering CR+Al+SiO2+HfO2+SiO2

Cold slump for LST mirrors
Hot slump for MST mirrors
Milling of Al-Honeycomb surface

Press for 48 hrs

Glass sheet 2.7mm
Glue Konishi-E
Al Honeycomb of 60mm thickA
3/8 inch Hexel

Mold R=56.0m after machining

Glue Konishi-E

Glass sheet 2.7mm(surface)
Mold ( R=56m )1510mm LST mirror Prototypes
2.7mm glass＋60mm AL.Honeycomb＋2.7mm Glass
D80 ~ 24mm at 2f

F2F：1.51m
Area：2m2
R of Curvature: 57m
PSF： <0.02°Weight： 45kg

D80 = 24mm at 2f(by Hironori Baba)

PMD system is installed at ICRR, U-Tokyo(developed by experts of Erlangen optic group)

Installed at ICRRSanko Mirror #01
measurements at Erlangen

Sanko Mirror #02
measurements at ErlangenSummary••

New prototype mirrors for LST and MST are produced by Sanko–

New process, and new honeycomb(3/8”)–

The PSF is now enough small–

The sputtering coat shows >92% reflectivity at 350nm.

–

Scratch test was done for the sputtering coat. It is 3-4 times stronger than the vapor coat of MgF2PSF is measured with LWD method by Erlangen group–Sanko M#01, D80 = 8.15mm–Sanko M#02, D80 = 10.80mm ( ~12mm by H. Baba)–PMD instrument is installed at ICRR, U-Tokyo  Next talk by Mr. Baba•

Development and production of AMCs are expected by CTA-Japan•We are planning the mass production of 220 LST mirrors in 2012 – 2016 at Sanko.