Electronics: Demod + 4Q FE Jo van den Brand, Second V+ review http://www.few.vu.nl/organisatie/dienst/technisch/electronica/projects/20062001/ Info on demodulator: Info on front-end system: http://www.nikhef.nl/pub/departments/et/virgo/ 11/10/2018

Demodulator boards Design Q2, Q3 2006 Prototype Q1 2007 2+2 Boards Q2 2007 Improvements 2007 Amplifier (noise) PCB length 8.35 MHz (band filter) 11/10/2018 Han Voet, VU Amsterdam

Test results Conversion gains Cross talk Apply 6.260000 MHz on Ref, 6.260100 MHz on RF Low 2.75, mid low 25, mid high 230, high 2000 Cross talk Apply 6.26 MHZ (8.35 MHz) to both reference inputs. Apply RF signal one channel (vertical/horizontal). Board 4, 5: H/V I & Q out < 0.3% of V/H I & Q phase 90 degree phase shift Measured with a 50 Hz beat frequency output signal on the I & Q outputs Phase deviation smaller than 1.5 degr Equivalent input noise 1 nV/rtHz (to be confirmed) RF input: white noise 20 Hz – 20 MHz, 80 mV RMS 11/10/2018 Discussion: replace all demod boards

4Q FE – Modeling Henk Groenstege TINA-TI Multisim 11/10/2018

Modeling Model agrees with data DC 2x lower RF 100 nV/rtHz 1/f noise amplifier resistor noise diode cap. Model agrees with data DC 2x lower RF 100 nV/rtHz (was 130 nV/rtHz) Gives 2.5 pA/rtHz Optimize both DC and RF 11/10/2018

Front-end amplifiers Non-linear design determined by Diode Capacitance Leakage current Feedback resistor (white noise) Feedback capacitance Desired bandwidth Desired gain factor 1/f noise Amplifier Voltage noise Current noise Input capacitances Gain-bandwidth product Under consideration OPA 846 OPA 657 AD 8675 (6V) ADA 4899-1 AD 829 Avoid switching in front-end (stray capacitance) 11/10/2018

Photo diodes Si PIN YAG 444-4AH Si Centronic QD50-3T InGaAs Q3000 11 mm diameter 0.45 A/W Rev. bias 180 V (power!) 10 pF Si Centronic QD50-3T IR enhanced 0.22 A/W Rev. bias 15 V (GEO) InGaAs Q3000 3 mm diameter 0.90 A/W Rev. bias 10 V < 225 pF 24 ns rise time In discussion with various suppliers: OSIOptoelectronics Centronic Hamamatsu 11/10/2018

InGaAs Simulation InGaAs Unacceptable performance at 6 Mz Bandwidth limited < 400 kHz InGaAs 3mm diameter type? Ordered: will be tested 11/10/2018

4Q FE: outside Dimensions of box roughly the same (48 * 100 * 170 mm) Mounting tube (30 mm) on front Same connectors and supply and steering voltages Bias control & monitoring New LF outputs Same detector (YAG 444-4), but rotated to + orientation Simple overload indication (LEDs) Spares: orientation x New: orientation + 11/10/2018

4Q FE: inside Total redesign (old → new): First stage 2 kV/A → 10 kV/A DC output amp. 5*, roll off at 100 Hz to 1*, passive pole at 35 Hz (if load > 50 kΩ) → cable driver 1*, pole at 100 kHz. Extra LF outputs, 1 Hz to 100 kHz. HF outputs amp. 20*, second order high pass 30 kHz, assumed BW 25 MHz → amp. 4*, 800 kHz … 25 MHz. Bias monitor Output with a scale -1/40, -200 V bias gives +5V. 11/10/2018

Status / issues Front-end electronics Prototypes have been constructed No switching in transimpedance stage Two FE versions Low power: ≤ 3 mW High power: ≤ 30 mW Switching possible after first stage DC filter 3.3 kHz LP Prototypes have been constructed Detector board, with first stage pre-amp Driver board contains the cable drivers differential amplifiers for the hor. and vert. outputs bias generation, etc Further studies ongoing Improve performance Decide on configuration Decisions needed on switching DC and RF Anticipate meeting in January 2008 11/10/2018

Planning Discuss switching, etc. Replacement of demodulator boards 11/10/2018

Summary Demodulator boards Front-end electronics Planning First systems delivered Discuss production of additional boards Front-end electronics Simulation models in place Amplifiers Diodes Test performance Planning Delivery prototype in March 2008 Delivery all boards in July 2008 11/10/2018

Results 1/f Affected by C Noise R2 Noise R1 11/10/2018

Noise sources Resistors R1 and R2 (10 k) Low pass filters Diode noise Noise = 4R kT BW = 4(10.000)(1.38 10-23 J/K)(295 K)(1 Hz) = 1.6  10-16 V2 Low pass filters fR1 = 1/2R1C2 = 1/2 (10.000 )(1.5  10-12 F)=10.6 MHz fR2 = 1/2R2C1 = 1/2 (10.000 )(10  10-9 F)=1.6 kHz Diode noise Dark current 1nA (use 180 G on –180V) Diode capacity 10 pF Amplifier noise Use pspice amplifier model Includes 1/f noise, etc. 11/10/2018