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Layered EPICS User Gap Control Interface for NSLS Mini-gap Undulators

Layered EPICS User Gap Control Interface for NSLS Mini-gap Undulators. William Nolan and John Skinner, Biology Department Susila Ramamoorthy and Lonny Berman, NSLS Department Brookhaven National Laboratory, Upton NY 11973 www.px.nsls.bnl.gov EPICS Collaboration Meeting June 12 -16, 2006.

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Layered EPICS User Gap Control Interface for NSLS Mini-gap Undulators

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  1. Layered EPICS User Gap Control Interface for NSLS Mini-gap Undulators William Nolan and John Skinner, Biology Department Susila Ramamoorthy and Lonny Berman, NSLS Department Brookhaven National Laboratory, Upton NY 11973 www.px.nsls.bnl.gov EPICS Collaboration Meeting June 12 -16, 2006

  2. Undulators provide brilliant beams for PX at the NSLS The PXRR method:  Screen on BM facility  Collect on ID facility The brilliant undulator beams are essential for efficient macromolecular structure determination using small crystals with large unit cells.

  3. The Undulator Control Challenge Synchrotron operator requisitions undulator control for ring fills about every 12 hours using machine control programs diffractometer front end monochromator mirror User application programs control diffractometer and detector every few s User selects wavelength by setting monochromator and gap about every 15 minutes using EPICS services

  4. Layered MGU Controls VME / RTEMS PXRR EPICS Beamline-IOC Executes wavelength change requests from CBASS Determines MGU harmonic and gap target PXRR EPICS MGU-IOC Downloads gap target whenever possible Continuously receives MGU status and gap setting Linux NSLS MGU Micro Carries out gap requests from MGU-IOC as well as overriding NSLS gap commands MGU

  5. MGU Control: Application and User Layer CBASS Application Program PXRR EPICS Beamline-IOC Executes energy change requests from CBASS Moves monochromator motors Determines gap target from harmonic emission table Suppresses gap change when scanning small ΔE Mono motor records New E Virtual gap motor record New gap target triggers interface layer MGU Harmonic Emission Single Process Variable Request: E or λ

  6. MGU Control: Interface Layer done gap target Virtual gap motor record PXRR EPICS MGU-IOC Transmits gap target requests to MGU device controller Periodic scans MGU status and actual gap setting May serve as precision gap controller using encoder readbacks Serves as standalone user gap control interface Custom device driver and interface communicates serially via RS232, 485, TCP/IP has FIFO buffer, handshaking, and polling functionality Incoming information: Control room user enable flag Gap drive status Current gap drive setting Stored gap set point for user ops Average of 4 gap encoder readings Optical gap readings at MGU ends MGU device driver error status Actuator post heater status Outgoing commands: Gap target request Request for status info MGU Status Info for User

  7. MGU Control: Device Layer NSLS MGU Micro Setup Serial interface on beam line server Serial interface on MGU device controller NSLS MGU Micro Carries out gap requests from MGU-IOC and NSLS Arbitrates user and NSLS control room access Monitors and controls all device functions Standalone MGU controller

  8. Gap Measurement on the X25 MGU Stepper Motor Drive (4x) Linear Resistive Encoder (4x) Limit Switches Optical Micrometer (2x; 2µm) Post Heaters (8x)

  9. Need For Gap Stability at Submicron level 7th Harmmonic 100eV FWHM 3.25eV/um

  10. Summary: Layers are safe and robust control method PXRR EPICS Beamline-IOC Executes user wavelength change requests Determines MGU harmonic and gap target PXRR EPICS MGU-IOC Downloads gap target whenever possible Acquires MGU status and gap setting NSLS MGU Micro Carries out gap requests from MGU-IOC as well as overriding NSLS gap commands MGU A safe and robust method to perform frequent MGU control in an open user environment Ready for remote user operation Simple way to extract essential control functions from full device control set Efficient method to bridge EPICS – custom device control interface Expandable to precision gap control based on true gap readings -cryo ops

  11. Acknowledgements: Lonny Berman Susila Ramamoorthy John Skinner

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