1. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 HOMS/SOM Design Status 30 Oct 2007 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. SM1 HM1HM2 SM2 SM3/4

2. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 1.4 m Preliminary design/test of HOMS & SOMS integrated mirror systems is nearly complete High risk areas receiving special attention are the subject of this talk Risk levels: Well established solutions & practices Moderate effort to demonstrate Significant effort to demonstrate

3. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 The HOMS design incorporates additional features to achieve - higher pointing resolution - tighter figure control HOMS & SOMS share the same basic design Rotation spindle & drive cam Mirror mount assembly Vacuum Chamber Translation slide 6-axis strut assembly Support Pedestal Z X Y (vert.) Tunable Z force 3 fixed Y forces & constraints 2 fixed X forces & constraints Y constraint flexure Z constraint B 4 C chin guard

4. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Mirror figure error must limit the beam divergence change to < 10% Figure requirements and allocation to contributing factors are expressed in nm, peak/valley < requirement > requirement << requirement 50 mm 30 mm 250 mm 175 x 10 mm 2 50 mm 30 mm 450 mm 430 x 15 mm 2 SOMSHOMS Tangential axis Sagittal axis

5. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Figure error budgets were established by finite element analysis of the mirror and mount Conclusions from finite element calculations of assembled mirror & mount: - Coating stress + fabrication errors dominate the figure error - Net curvature is primarily sphere - Spherical errors can be corrected by bending the mirror HOMS Contribution Coating Mounting Thermal Gravity Total (convex) Changes since HOMS PDR: - Mirror holes relocated to better balance gravity load - Refined modeling boundary conditions

6. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 HOMS tangential figure will be adjusted during operation by bending the mirror An axial force & constraint are applied near the back of the mirror 200 nm concave pre-figure will unbent during assembly on an interferometer - bending will be applied before securing vertical hold down springs - the model shows aspheric curvature near free corners 4.4 lb 3.7 lb Mirror bonded to mounting pads Unbonded (vertical springs loose)

7. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Motorized micrometer Shaft & bellows Manual Pre-load Adjustment Anvil Adjustment spring Concave pre-figure removed by applying force to the anvil while observing with an interferometer Mirror assembly is installed into the vacuum chamber & adjustment spring is attached Figure is remotely adjusted by pull/push on the adjustment spring - spring travel range provides high resolution, high thermal stability The HOMS mirror assembly accommodates real-time figure control

8. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Measured deflection is in reasonable agreement with the finite-element model Aspheric residual from bending is within our measurement noise floor Bender performance is being validated on the HOM prototype: a silica mirror on Invar mount Vibration scale Calculated: 2.7 lb FOV 5nm 0 15mm 0270mm 450 mm Measured area: 270 x 15 mm 2 Turbulence scale +/- 1.5 nm uncertainty Measured on 12” interferometer

9. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 HOMS mirror pointing stability requirements are very challenging FEH Z X (hor.) Y (vert.) NEH SM1 HM1 SM2 SM3/4 HM2 Plan view (not to scale) Rotation increments must in step the beam within 10% of its diameter at the experiment stations - long term stability should be even less  30 m  300 m

10. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Rotation spindle - flexure type Stepper motor - 1000 step/rev Pusher - 2 axis flexure The HOMS rotation resolution requirement has been demonstrated Two capacitance sensors with 0.5 nm resolution measure angle change - they are fast enough (5 kHz) to demonstrate natural frequencies are  o >>100 Hz Harmonic drive - 2500:1 for HOMS Cam assembly - 0.7 mm offset Data for a 1 mm offset cam, 2500:1 harmonic drive, in 10 nr increments

11. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 1st tier: Eliminate thermal jitter with periods < 1 hr - any air tight enclosure will suffice - long period temperature oscillations penetrate easily - rotation jitter closely follows temperature - a long period oscillation remains, but is it rotation or sensor drift? A tiered approach is taken to evaluate pointing stability Outside air Inside air Insulation No Insulation All carbon steel components

12. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Sensor drift makes it difficult to trust long term measured trends Sensor calibration block 60 mV drift Sensors are placed in a static gage block to measure temperature correction Uncorrelated drift is also observed, corrupting long term data. Presently investigating how to improve this Zero Drift in nrad

13. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Additional measures being investigated to control rotation drift: 2 nd tier: add a thermally compensating material to the rotation linkage - requires accurate long term rotation measurements 3 rd tier: use water tempered to limit excursions inside the enclosure < +/- 0.1 C - compact air cooled chillers are readily available 4 th tier: adjust rotation real time by measuring x-ray beam drift Another alternative: make everything out of Invar instead of stainless steel – not presently being pursued

14. Tom McCarville mccarville1@llnl.gov Oct 30, 2007 Summary of key opto-mechanical design issues – figure and pointing corrections are both metrology limited The contributing factors to figure error are becoming well understood - mounting, thermal, and gravity induced errors are small: coating & fabrication errors dominate - errors < 10-20 nm are not easily measured for off-line correction - real time correction during operation is advisable for HOMS Long term pointing stability is under investigation - insulation eliminates rotation fluctuations with < 1 hr period - passive compensation requires nm resolution sensors with long term stability: not yet identified - tempered water will limit enclosure variations < +/- 0.1 C - real time pointing corrections are always an option (last resort)