1 / 16

New Quadrant Diodes Motivations & Requirements Status & Plans: see Nikhef talk

New Quadrant Diodes Motivations & Requirements Status & Plans: see Nikhef talk. The Frascati QD front end module. New front end electronics - motivations. No more spare parts + we want to install additional QD’s (Q52, Q1p2; 10 in total) Improvements Higher max. light power x 10

nell
Download Presentation

New Quadrant Diodes Motivations & Requirements Status & Plans: see Nikhef talk

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. New Quadrant DiodesMotivations & RequirementsStatus & Plans: see Nikhef talk

  2. The Frascati QD front end module

  3. New front end electronics - motivations • No more spare parts • + we want to install additional QD’s (Q52, Q1p2; 10 in total) • Improvements • Higher max. light power x 10 • Presently 3 mW @ 1064 nm • Lower electronics noise  3 • Limited by preamplifier • => Less noise in at all powers • Lower offsets • DC offset drifts caused problems • Better geometrical configuration • See Virgo CHRQ 008/2006 • 2 types of modules: High/Low power • Reason: low noise + high power too difficult to realize in one module Shot noise Preamp noise Noise (A/rtHz) 2005 measurements Photocurrent (A)

  4. VSR1 alignment noise budget QD front end noise

  5. Main requirements HP = high power modules (<= 30 mW) LP = low noise modules

  6. Additional requirements (I)

  7. Comparison ‘X’ and ‘+’ configuration • Relative sensitivity of X configuration • Virgo QD’s are used in X configuration • Same signal-to-noise-ratio as + config. • Couplings • Horizontal/vertical error signal couplings • X config: couplings for h+v miscentering • Misalignment sensitivity • Strong horizontal or vertical misalignment: • X config may give no error signal • Conclusion • For new QD front ends • “+” configuration desirable vs.

  8. Additional requirements (II)

  9. DC signal whitening • Whitening filter • double zero @2 Hz, double pole @ 20 Hz? • (-> similar to standard photodiode prefiltering) • Whitening filter should be switcheable (jumper,...) DC signal spectrum (VSR1)

  10. End

  11. Geometrical specifications • Geometry such that the front end holder can be re-used Front end support structure

  12. Connector specifications • connectors like on image

  13. Anti-aliasing filters • Presently 2 output filters in front end DC path • simple poles 33 Hz & 85 Hz => Dephasing! • Digital AA filters in readout chain possible? (To be verified) delay 6 msec Dephasing (degrees) AC filter + delay 6 msec (filter in demod. board) DC filter + delay 6 msec Frequency (Hz)

  14. CRQ referee additions 08/2006 • Additional Requirements • Cross-talk < 5% • optical exitation • RF gain/phase matching: < 1%/10° • optical exitation • Electronic isolation (ground not connected to bench) • Geometrical/connection specifications • Additional Functionalities • RF saturation monitors for pre-amps (yel/red LEDs in front end) • DC signal whitening (double zero at 2Hz, double pole at 20Hz) • Less important features • LEDs indicating DC signals (for initial quad alignment, done by hand) • Separate connector and test-box (with BNC connectors) to inject/monitor RF signals (for on-site unit testing)

  15. Diode material • Important points • Max. allowed laser power • Quantum efficiency @ 1064 nm • Diameter >= 10 mm • InGaAs • Quantum efficiency 0.7 A/W (up to 90%) • Low bias voltage • => high optical power possible • High capacity • but maybe OK with our low frequency? • Large sized difficult • custom fabrication possible (Ø 10 mm) • Si • Quantum efficiency at best 45% • EG&G YAG 444-4 (180 V) 0.45 A/W • large crosstalk? (GEO: 6 dB) • Centronic QD 100-3T (15 V bias) 0.22 A/W • IR enhanced (used at GEO) • Centronic QD 100-4X (120 V) 0.43 A/W • YAG enhanced

  16. Noise sources • ADC noise • 2 uV/rtHz • Preamplifier noise • 5 pA/rtHz (1 quadrant element) • typ. 50 nV/rtHz at front end output • Demodulation board gain 200 • 10 uV/rtHz at ADC level AC • 80 nV/rtHz at ADC level DC • Conclusion • DC signal below ADC noise level without pre-filtering

More Related