M 321M 331 Mirror Switchyard Design Review Tom

M 321/M 331 Mirror Switchyard Design Review Tom Miller 11 -29 -2006 1 Engineering Division

Basic layout of M 321/M 331 mirror switchyard 2 Engineering Division

Alignment, resolution and stability requirements y M 321 z x M 331 Figure 4: Coordinate system of mirror switchyard Alignment / stability tolerance and mechanical steps for M 321 and M 331 Alignment tolerance Mechanical step Stability tolerance X 100 mm 38 mm 19 mm Y 1 mm N/A 0. 5 mm Z 300 mm N/A 150 mm (Yaw) Qx 1 o N/A 0. 5 o (Pitch) Qy 1 mrad 30 mrad 15 mrad (Roll) Qz 24 mrad N/A 12 mrad Dimension 3 Engineering Division

Basic Optic Design One optic versus two Single optic advantages: • No mechanisms for alignment between M 321 & M 331 • Lighter and more rigid optic and mounting for better stability • Smaller required translation due to compact design • Faster setup and commissioning due to fixed angle between M 321 & M 331 Single optic for M 321 and M 331 with diagnostic pass – through. Mounting details are omitted Single optic disadvantages: • Up-front cost of the optic. This can be offset by reduced mechanism and setup costs if optics are not routinely damaged • Manufacturing tolerances on the relationship between the two optical surfaces must be good for quick replacement of the optic. 4 Engineering Division

Maximum Required Motions Translations(x): (Single optic) RIXS Rotated: 12. 01 mm outbound ARPES Rotated: 17. 97 mm inbound Total: 29. 98 mm (nominal) Pitch (Thetay ): (Single or dual optics, RIXS & ARPES) High Res grating: +/-259 microradians High Flux grating: +/-168 microradians Roll (Thetaz ): (Single or dual optics, RIXS & ARPES) +/- 5 milliradians 5 Engineering Division RIXS rotated ARPES rotated

Mechanism Fundamentals Initial concept: Mount the optic(s) rigidly in the chamber and translate the chamber with a single slide and pitch and roll with struts to steer the beam. Advantage: • • Familiar approach Easy installation survey. The optic(s) can be accurately fiducialized in a lab and those numbers used for installation alignment. Disadvantages: • • 6 Input and output bellows are required. Large and variable off-axis forces act on the translation slide and rotation mechanisms If pumping is added to the chamber, the pump must move with the chamber or be bellows isolated. This will result in a large mass offset from the slide or more nonconstant bellows forces. Both solutions result in poorly placed variable forces. Pitch and roll motions intrinsically couple to all other motions. Parasitic motions from variable off-axis forces may make high resolution encoder readings meaningless Engineering Division

Mechanism Fundamentals New concept: Mount the chamber rigidly and move the optic(s) Advantages: • • • 7 Bellows forces are small and self-cancelling Pitch corrections are nominally independent of roll Translations are nominally independent of pitch and roll Any force required for translation is small and almost directly in line with the linear bearings in the stages. All sources of backlash in the mechanism are spring loaded in the axis of freeplay. Pitch and roll are flexure-based motions and therefore very repeatable Large pumps can be mounted beneath the tank with no effects on motion. Small off-axis forces will make encoder readings more meaningful The moving masses are small and the mechanisms optimized for stiffness. The vibrational modes of the mechanism are thus above 200 Hz. All mechanism parts are stainless steel or cast iron. This should yield good thermal stability. Engineering Division

Mechanism Fundamentals New concept: Mount the chamber rigidly and move the optic(s) Disadvantages: • • 8 Unfamiliar design Roll couples to pitch and translation. 1 milliradian of roll induces 200 microradians of pitch for ARPES, 100 microradians of pitch for RIXS and 0. 13 microns of translation. Intrinsic roll errors should be very small, and thus the roll corrections should also be small, so pitch coupling should not be a problem. Translation coupling will be insignificant. Pitch couples to translation. 250 microradians of pitch results in 9 microns of translation at the nominal reflection point. The large pitch changes required for grating selection also have an associated ~1. 5 mm translation, so this number is acceptable. Installation surveys of the optic will be relatively imprecise. The orientation of the optic to outside fiducials must be determined after the optic is mounted in the tank. The in-vacuum fiducials are close together and difficult to survey in the tank. Engineering Division

Mechanism Overview 9 Engineering Division

Translation Mechanism 10 Engineering Division

Chamber pass-through 11 Engineering Division

Roll Mechanism 12 Engineering Division

Pitch Mechanism 13 Engineering Division

Mirror details 14 Engineering Division

Center Section 15 Engineering Division

Pitch Hinge Details 16 Engineering Division

Micro-e Encoder Scale 17 Engineering Division

Center Section Mounting 18 Engineering Division

Pitch Mechanism First mode 19 Engineering Division

Spring stress at 1 m. Rad pitch 20 Engineering Division

Demagnification spring deflection with 1 m. Rad pitch 21 Engineering Division

Roll Mechanism first mode 22 Engineering Division

Cost estimate Fab and purchases: $78, 000 Assembly (200 hrs) : $20, 000 Total: 23 $100 k Engineering Division