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Development of the Dicke-switched WVR prototype for ALMA

Development of the Dicke-switched WVR prototype for ALMA. Magne Hagström, Lars Pettersson and Leif Helldner Collaboration with. Development of the Dicke-switched prototype for the ALMA WVR. Radiometer design - Double Dicke Critical components Lab tests SMA - tests

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Development of the Dicke-switched WVR prototype for ALMA

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  1. Development of the Dicke-switched WVR prototype for ALMA Magne Hagström, Lars Pettersson and Leif Helldner Collaboration with Miroslav Pantaleev

  2. Miroslav Pantaleev

  3. Development of the Dicke-switched prototype for the ALMA WVR • Radiometer design - Double Dicke • Critical components • Lab tests • SMA - tests • Single Dicke prototype Miroslav Pantaleev

  4. Optics layout - Double Dicke • Chopper wheel to select between sky - calibration • Measure all the time • Cryo cooler as cold load • Warm mixers and LNA M4 M3 C2 M5 M5 C1 Miroslav Pantaleev

  5. Calibration Hot and Cold Vane Solenoid Hot load Miroslav Pantaleev

  6. Chopper wheel function and design goals • Reliable > 10 years of continuous running • Small blade diameter – cut a small beam waist • Phase locked to external square wave Miroslav Pantaleev

  7. Chopper blade • Dynamically balanced chopper wheel • No holes to avoid turbulences Miroslav Pantaleev

  8. Chopper support • Bearings – SKF • Lifetime – more than 25 years (depending on the operational rpm) • Flexible coupling to dump vibrations Miroslav Pantaleev

  9. Chopper protective cover Miroslav Pantaleev

  10. Chopper blade positioning Miroslav Pantaleev

  11. Chopper timing Miroslav Pantaleev

  12. Measured chopper data Chopper blade jitter Miroslav Pantaleev

  13. Block diagram Double Dicke Miroslav Pantaleev

  14. Mixer Miroslav Pantaleev

  15. 3 dB, 91.6 GHz power divider • Waveguide branch type couplers – many section required to cover wide bandwidth • Double probe structure is coupled to the E-field in a waveguide By courtesy of V.Vassilev Miroslav Pantaleev

  16. DSB - Noise temperature Double Dicke Miroslav Pantaleev

  17. Sensitivity Miroslav Pantaleev

  18. Filter bands • The LO frequency is kept very close to line frequency. • Mixers are double sideband. • Four IF channels with larger bandwidth away from the centre of the line. Miroslav Pantaleev

  19. Filter and video assembly Miroslav Pantaleev

  20. Custom designed filters • Bandpass filter B (1.565GHz – 2.315GHz) • Ring resonators bandpass filter • Compact, low insertion-loss, sharp-rejection, and wide-band application Miroslav Pantaleev

  21. Calibration reference loads • Two reference temperatures with a T  150 K, one of them close to sky the temperature • Peltier element - not possible to get below – 50 ºC • Noise diode - only  4 dB ENR • Sterling cooler • Cool a microwave absorber to below 150 K. • Stabilize the temperature of the absorber to < 0.05 K • Absorber reflectivity > 30 dB at 183 GHz. • Maintenance free time  10 years. Miroslav Pantaleev

  22. Cooling power Miroslav Pantaleev

  23. Cooled load mount Miroslav Pantaleev

  24. Thermal stabilization Frame with Peltier cooler Insulation IF temperature regulation Miroslav Pantaleev

  25. Single Dicke Miroslav Pantaleev

  26. Block diagram Single Dicke Miroslav Pantaleev

  27. Optics layout - Comparison Miroslav Pantaleev

  28. Physical size comparison: Double -Single Dicke • Cost saving pre-production design work • Single Dicke Receiver • Replacement of the Hymatic Sterling cooler with a Peltier cooler • Replacement of the cold load with a cool/hot load combination Miroslav Pantaleev

  29. Cold load • Single Dicke Receiver • Replacement of the Hymatic Sterling cooler with a Peltier cooler • Replacement of the cold load with a cool/hot load combination Miroslav Pantaleev

  30. Current status Miroslav Pantaleev

  31. IF linearity Miroslav Pantaleev

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