Robust Low Cost Cryocooler Goniometer for ARCS using

Robust, Low Cost Cryo-cooler Goniometer for ARCS using available, commercial grade, instrument components Preliminary Design Review Prepared by Robert Chave Applied Physics Inc. Altadena, California robert@chave. net 626 -622 -8562 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Design Approach • • • A design which permits a range of options for sample mounting, and leaves opportunity for future modification for presently unspecified needs Selection and placement of materials so as to avoid signal to noise reduction through scattering or a radioactive waste problem Maximal use of off-the-shelf, or build-to-existing print major components to reduce cost both of primary build and availability of spares Separate motion controller, independent from data computer for increased reliability, communicating with data computer through IEEE 488 Integrated system of motion controller, stepper drivers, motors, software and cables from an “all in one box” vendor of motion control technology 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Requirements / Goals Goal: Approach: Sample Temperature 10 K to 290 K Positioning accuracy 6 arc minutes absolute, both axes Vacuum 10 -7 Torr Rapid cool down Less than 3/4 hour Reliability Consistent with $1. 4 Billion source cost Ease of use Ease of Sample Insertion & no binding on alignment pins Rapid pump down No virtual leaks, easy vacuum conductance 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Design Trade Studies Basic Configuration Trade Study Cooler on center, mechanical & thermal paths combined, single large built-to-user-specification, seal-bearing unit. Cooler off-center, mechanical & thermal paths separate, standard seal -bearing unit, located on instrument centerline. Cooler on center, mechanical & thermal paths, separate, main bearing on center & in vacuum, smaller standard seal. ☼ 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Configuration Trade Study 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Design Trade Studies Thermal Rotary Joint Trade Study Slip joint Conduction through mechanical flexure joint Thermal strap of fully annealed, three thousand strand, thin-strand, copper Litz wire. ☼ Vacuum Condensable Materials Reduction Trade Study Motors in and out of vacuum Ferroseal vs O-rings Lubricants, Braygrease. TM and Dichronite. TM 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Cryo-cooler Goniometer for ARCS stepper motor NEMA 23, 2 stack APD Sumitomo Cooler, 2 stage, 80 W max Worm drive, 180: 1 ratio, no back-lash stepper motor NEMA 17, vacuum type harmonic drive, vacuum type ferrofluidic seal video camera drag link, w/ Delrin. TM rod end bearings thin section, Kaydon. TM bearing assemblies thin section isolation tube, G 10 or SS radiation shield thin wall SS axle flexible Litz wire thin section bearings sample mounting plate, aluminum 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

ARCS Goniometer & Vacuum Jacket 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Design Trade Studies Thermal Isolation Performance Trade Study SS down tube G 10 down tube Vibration Susceptibility Trades Study Fundamental Frequencies Brace approach 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Thermal Modeling Isolation Links Sources o. Heat capacity of structure during cool down o. Radiation (small compared with above) Sinks o. Cooler o. Top plate System Sensitivities: The number and preparation of thermal joints drives cool down times, and lowest sample temperature attainable more strongly than other system parameters 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Cryocooler & Thermal Isolation Structure thin section isolation tube, G 10 or SS APD Sumitomo Cooler, 2 stage, 80 W maximum radiation shield tubular SS axle flexible Litz wire thin section bearings 25 -Sep-02 PDR Rev D sample mounting plate, aluminum Cryo-Cooler Goniometer for ARCS www. chave. net

Cooler Power APD 408 S vs Cryotiger SHI-APD 408 S • two stage • 80 Watts initial • final sample temp of 10 K • $ 27, 800 IGC-Cryo. Tiger • 1 hour to 100 K • 10 Watts initial • final sample temp of 77 K • $ 8, 655 each unit 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Cooler Performance & Conductor Performance cooler power conductivity integral for copper Specific Heat of Copper image credit: Cooner Wire 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Resistance of Thermal & Structural Elements • • • the number of mechanical joints between source and sink and their state of preparation is an influential design parameter rougher surfaces are sometimes more effective than smooth ones indium gaskets desirable on conductive joints 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Isolation System – Steady State Temperatures Down Tube G 10 Bearing Spokes Sample Litz Wire Spokes Sample Bearings 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Cold End Thermal Isolation System Spoke Properties • maximum heat flow ~ 550 m. W • heat flow steady state < 50 m. W • commercial product • titanium or stainless • low cost, high stiffness, readily available 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Mechanical Properties of Spokes Fundamental freq: Factor of Safety: ~ 2 k. Hz 10. 5 Nom. Load per Spoke: 50 lbs Diameter: 25 -Sep-02 PDR Rev D 1. 5 mm Cryo-Cooler Goniometer for ARCS www. chave. net

Drive Train, 2 Axes stationary APD cooler head stepper motor NEMA 23, 2 stack, Compumotor harmonic drive, 30: 1, zero backlash Worm drive, 180: 1 ratio, zero backlash stepper motor NEMA 17, 2 stack, vacuum rated ferrofluidic seal drag link, w/ Delrin. TM rod end bearings sample mounting plate thin section, Kaydon. TM bearing assemblies 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Expected Accuracy for Drive Train Cumulative error of the various kinematic components is within the 1/10 th degree specified by the Project as a goal. Primary Axis Source Accuracy of Parker Daedal Drive 1. 2 arc minutes Ball End Roundness Tolerance 1. 2 arc minutes Total Error, absolute 5. 4 arc minutes Source 3. 4 arc minutes Error Accuracy of Harmonic Drive 1. 5 arc minutes Ball End Roundness Tolerance 1. 2 arc minutes Total Error, absolute 3. 9 arc minutes RMS Error 25 -Sep-02 PDR Rev D 3 arc minutes Ball End Roundness Tolerance RMS Error Secondary Axis Error Cryo-Cooler Goniometer for ARCS 2. 3 arc minutes www. chave. net

Harmonic Drive Model CSF-17 -30 -2 A-R w/ Vacuum Lube Drive Ratio 30: 1 Accuracy 1. 5 arc minute Max Peak Torque Load 266 in-lbs Lubricant Braygrease. TM flight rated NASA image credits: HD Systems Inc. 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Thermal & Motion Sensors & Limit Switches Sensors Hall effect for end of travel and home position sensing, in vacuum Motor temperature for in-vacuum motor End effector temperature sensing with Lake Shore silicon diodes Control System Switch Configuration Hard (switch) stops and soft (programmed) stops, with hard stops normally never encountered Peperol & Fuchs NBB 1. 5 – 8 GM 60 Hard stops are wired directly to individual axis drive electronics 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Motion Control Software Test scripts in Python Communication w/ Controller either by Ethernet, or serial cable Controller software is "Motion Planner" TM by Compumotor owell characterized, large installed user base, well supported o. Point to point motion and calibration routines o. S-curve accelerations, to limit ringing in mechanical components, from acceleration and braking 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Block Diagram, Drive Components 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Video Camera for Sample in Vacuum Monitoring COHU Camera, to special performance specification for LLNL vacuum & radiation rated production run of 1000 for LLNL reduces price COHU 2600 b/w camera 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Preventing Binding During Insertion 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Virtual Leak Attenuation & Pump Down Speed Methods Employed: Fastener holes and tapped holes drilled through to back side of part, such that these vent freely Use of center vented fasteners where back side vent ports are not practical No enclosed volumes & easy vacuum conductance from partially enclosed volumes Vapor degreasing, plus solvent cleaning to remove vacuum condensible material 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Instrument Case, Storage & Transfer • rapid instrument insertion • rapid instrument lock down • device cleanliness retained • fork lift o. k. • 3’ x 3¼’ h 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

References Papers Gimbal Mechanism For Cryogenic Alignment Of 1 Meter Diameter Optics, R. G. Chave, A. E. Nash, J. Hardy, SPIE Proceedings, 40 th Annual Meeting, 1995 Handbook on Materials for Superconducting Machinery, ARPA order No. 2569, Program Code 4 D 10, Contract No. CST-8303, Cryogenics Division, NIST, 1977 Thermal Boundary Resistance of Mechanical Contacts Between Solids at Sub-Ambient Temperatures, E. Gmelin, M. Asen-Palmer, M. Reuther and R. Villar, Review Article, Journal of Physics D: Applied Physics 32 R 19 -R 43, 1999. Texts Cryogenic Process Engineering, Timmerhaus & Flynn, Plenum Press, International Cryogenics Monograph Series, 1989 Experimental Techniques in Condensed Matter Physics at Low Temperatures, Richardson & Smith, Addison Wesley, 2 nd Edition 1998 Matter and Methods at Low Temperatures, F. Pobell, Springer Verlag 2 nd Edition 1996 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Budget - Purchased Parts 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Budget – Cost to Complete 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net

Schedule to Completion 25 -Sep-02 PDR Rev D Cryo-Cooler Goniometer for ARCS www. chave. net