Transcript Slide 1
P45 Test Results and beyond… Marco Xompero Daniela Zanotti Armando Riccardi LBT Progress Report, Feb 21-24 2005 Marco Xompero 1/14 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 21-24 2005 Marco Xompero 2/14 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 21-24 2005 Marco Xompero 3/14 Position Noise (1) Typical RMS value reduced ~1.3 [nm] INCREASE WORK DISTANCE! LBT Progress Report, Feb 21-24 2005 Marco Xompero 4/14 n d2 Position noise (2) • Work gap: 68mm • What do we expect? Noise Typical increaseRMS prop.~3.5 d2…[nm] • Different gain on different rings – Proportional: Inner/Mid 0.1N/mm Outer 0.1N/mm – Derivative: Inner 45 Ns/m Mid 43 Ns/m Outer 90 Ns/m • Double derivative guard pole at 15kHz High derivative means air damping substitution LBT Progress Report, Feb 21-24 2005 Marco Xompero 5/14 Step Response (1) Other Modes Cross Talk Old settling time: 0.7[ms] New settling time: ~0.57[ms] to ~0.67[ms] LBT Progress Report, Feb 21-24 2005 Marco Xompero 6/14 Step Response (2) Mid stiffness mode LBT Progress Report, Feb 21-24 2005 High stiffness mode Marco Xompero 7/14 Chopping • 128 mm gap • Proportional: In, Mid, Ext 0.04 N/mm • Derivative: In, Mid 10 Ns/m, Ext 20 Ns/m • Edge PtV tilt ~140mm i.e. ~14 arcsec on the sky • Chopping frequency ~5Hz LBT Progress Report, Feb 21-24 2005 Marco Xompero 8/14 Chopping (2) Settling Time ~10ms LBT Progress Report, Feb 21-24 2005 Marco Xompero 9/14 Chopping (2) Rms ~3.2 [mas] K Band d.l. size: ~53[mas] LBT Progress Report, Feb 21-24 2005 Marco Xompero 10/14 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 21-24 2005 Marco Xompero 11/14 Optical test tower (2) Temperature Sensors (PT1000) Out N S H20 + Glycole In LBT Progress Report, Feb 21-24 2005 Marco Xompero 12/14 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 68mm to 130 mm. • 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 21-24 2005 Marco Xompero 13/14 The End? The End! LBT Progress Report, Feb 21-24 2005 Marco Xompero 14/14