PISCO Atmospheric Dispersion Compensator Will High Harvard University December 2006

An ADC for PISCO ADC placeholder in blue below ADC placeholder in blue below After shutter (green below) After shutter (green below) Before collimator Before collimator Mounted on PISCO’s optical bench Mounted on PISCO’s optical bench

An ADC for PISCO ADC placeholder g r i z D1 D2 D3

An ADC for PISCO ADC placeholder g r i z D1 D2 D3

Our ADC from the Ground Up

2 Prisms 18 mm apart 18 mm apart 130 mm diam 130 mm diam 18 mm thick 18 mm thick

Stainless Steel Housings Gear teeth + 360˚ groove for timing belt Gear teeth + 360˚ groove for timing belt Another 180˚ groove for zero- pointing with microswitches Another 180˚ groove for zero- pointing with microswitches Lip: precision machined chamfer with semi-circular cross section Lip: precision machined chamfer with semi-circular cross section

Stepper-Driven Non-slip Timing Belts McMaster: McMaster: Non-slip, double sided timing belts (teeth + groove) Non-slip, double sided timing belts (teeth + groove) 2 specialty pulleys 2 specialty pulleys Oriental Motor steppers Oriental Motor steppers Custom axles and stepper mounting flanges Custom axles and stepper mounting flanges

Stepper-Driven Non-slip Timing Belts Teeth + 360˚ groove (timing belt) 180˚ groove (zero-pointing)

2 Microswitches to Mark Zero-point

2 Microswitches to Mark Zeropoint Teeth + 360˚ groove (timing belt) 180˚ groove (zero-pointing)

3 V-groove Track Rollers per Prism

Aluminum Case

Purely Rectangular Profile Beam toward you Beam away from you

Zero-pointing McMaster-Carr Long Roller Lever Snap- Acting Switches McMaster-Carr Long Roller Lever Snap- Acting Switches 2 x $ x $ " x 1.94" x 0.69“ 0.95" x 1.94" x 0.69“ Max ratings: Max ratings: –15 Amps –250 Volts AC/DC (Screw terminals) –186 Watts 3 terminals (SPDT) 3 terminals (SPDT) “Rising edge” means zero, “falling edge” can mean anti-zero if machined precisely “Rising edge” means zero, “falling edge” can mean anti-zero if machined precisely

Rollers McMaster-Carr Adjustable- Height Perma-Lube V-Groove- Guided Track Rollers McMaster-Carr Adjustable- Height Perma-Lube V-Groove- Guided Track Rollers 6 x $ x $ /32" adjustable height play 1/32" adjustable height play Ball bearings Ball bearings Permanently lubricated and sealed = maintenance free Permanently lubricated and sealed = maintenance free 90˚ groove 90˚ groove Smallest available: Smallest available: –About 1 2/3” long –1 ½” roller diameter

Timing Belts McMaster-Carr Double- Sided Flexi-Timing Belts and Pulleys McMaster-Carr Double- Sided Flexi-Timing Belts and Pulleys 2 x $29.66 (belts) + 2 x $23.56 (pulleys) 2 x $29.66 (belts) + 2 x $23.56 (pulleys) Single stranded (one groove) Single stranded (one groove) 0.20" wide 0.20" wide 24” outer circumfrence belts 24” outer circumfrence belts 1 ½” diam pulleys 1 ½” diam pulleys Anodized aluminum pulleys Anodized aluminum pulleys

Steppers Oriental Motor 5-Phase Microsteppers (CRK513PAP) Oriental Motor 5-Phase Microsteppers (CRK513PAP) 2 x $367, in stock 2 x $367, in stock 0.72˚ Basic Step 0.72˚ Basic Step 24 Volts, ~1/4 Amp 24 Volts, ~1/4 Amp < 80˚ C operating temperature... BUT: < 80˚ C operating temperature... BUT: –We don’t need high speeds nor long run times –Can turn off current if we install friction devices on prism housing –“High torque motor current is reduced to suppress heat generation. Eg, to avoid temperature rise in precision machinery.” I think this means a lower current gives the same torque as the standard model We make the flanges We make the flanges Want to use the same focus stepper drivers Want to use the same focus stepper drivers 5 pins per stepper 5 pins per stepper Stock Driver

Wiring Goal: single cable Goal: single cable Wires Wires 3 x 2 microswitches + 5 x 2 steppers = 16 wires Run wires along inside case surfaces to single D connector Run wires along inside case surfaces to single D connector ADC cable runs to on- board PISCO driver rack (water cooled) ADC cable runs to on- board PISCO driver rack (water cooled) Drivers controlled downstairs Drivers controlled downstairs Single D Connector

Summary About 18 lbs About 18 lbs 4 ½” deep x 11” wide x 10” tall 4 ½” deep x 11” wide x 10” tall Goals Goals –Single cable from ADC to driver rack –Use focus stepper driver instead of stock –Minimize stepper heat dissipation by switching off current and using simple friction devices Heat dissipation by ADC negligible Heat dissipation by ADC negligible –Assumed by drivers –Driver rack water cooled To do To do –Mounting holes –Internal wire guides –Microswitch mounts –Alignment (tolerances)