LBT Progress Report, Feb Marco Xompero 1/14 P45 Test Results and beyond… Marco Xompero Daniela Zanotti Armando Riccardi

LBT Progress Report, Feb Marco Xompero 2/14 Overview Flattening P45 thin shell with bias magnets. Position noise characterization with new electronics. Thin shell step response. Chopping? Chopping! Test tower optical bench.

LBT Progress Report, Feb Marco Xompero 3/14 Flattening P45 Actuator locations finite element analysis: LBT672 shell deformation due to local torque 39 nm PtV / N mm => max: 2.3nm PtV

LBT Progress Report, Feb Marco Xompero 4/14 Position Noise (1) Typical RMS value reduced ~1.3 [nm] INCREASE WORK DISTANCE!

LBT Progress Report, Feb Marco Xompero 5/14 Position noise (2) Work gap: 68m What do we expect? Noise increase prop. d 2 … Different gain on different rings –Proportional: Inner/Mid 0.1N/m Outer 0.1N/m –Derivative:Inner 45 Ns/m Mid 43 Ns/m Outer 90 Ns/m Double derivative guard pole at 15kHz Typical RMS ~3.5 [nm] High derivative means air damping substitution

LBT Progress Report, Feb Marco Xompero 6/14 Step Response (1) New settling time: ~0.57[ms] to ~0.67[ms] Old settling time: 0.7[ms] Other Modes Cross Talk

LBT Progress Report, Feb Marco Xompero 7/14 Step Response (2) Mid stiffness mode High stiffness mode

LBT Progress Report, Feb Marco Xompero 8/14 Chopping 128 m gap Proportional: In, Mid, Ext 0.04 N/m Derivative: In, Mid 10 Ns/m, Ext 20 Ns/m Edge PtV tilt ~140m i.e. ~14 arcsec on the sky Chopping frequency ~5Hz

LBT Progress Report, Feb Marco Xompero 9/14 Chopping (2) Settling Time ~10ms

LBT Progress Report, Feb Marco Xompero 10/14 Chopping (2) K Band d.l. size: ~53[mas] Rms ~3.2 [mas]

LBT Progress Report, Feb Marco Xompero 11/14 Optical test tower (1) GOALS: Avoid air convection Minimum hexapod movement to correct defocus term in the optical path SOLUTION: Local thermal stability in all tower length within 0.1 ◦ C (ex: INVAR support add only 30 nm defocus term)

LBT Progress Report, Feb Marco Xompero 12/14 N S Optical test tower (2) H Glycole Out In Temperature Sensors (PT1000)

LBT Progress Report, Feb Marco Xompero 13/14 Summary Bias magnets increase the safety and induce acceptable mirror figuring errors. P45 new control devices and sensors are ok! We can work easily from 68m to 130 m. New electronics improved settling time. Chopping require optimization but we are not so far! The temperature control of optical test tower has been tested to be in spec.

LBT Progress Report, Feb Marco Xompero 14/14 The End? The End!