new quadrant diodes motivations & requirements status & plans: see nikhef talk
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
1 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
New Quadrant DiodesNew Quadrant Diodes
Motivations & Requirements
Status & Plans: see Nikhef talk
2 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
The Frascati QD front end moduleThe Frascati QD front end module
3 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
New front end electronics - motivationsNew front end electronics - motivations
No more spare parts+ we want to install additional QD’s (Q52, Q1p2; 10 in total)
ImprovementsHigher max. light power x 10
Presently 3 mW @ 1064 nm
Lower electronics noise 3Limited by preamplifier
=> Less noise in at all powersLower offsets
DC offset drifts caused problems
Better geometrical configuration
See Virgo CHRQ 008/2006
2 types of modules: High/Low powerReason: low noise + high power too difficult to realize in one module
2005 measurements
Preamp noise Shot noise
Photocurrent (A)
Nois
e (
A/r
tHz)
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VSR1 alignment noise budgetVSR1 alignment noise budget
QD front end noise
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Main requirementsMain requirements
Property Virgo+ requiremt.
Component spec
Notes
Electr. noise LP Electr. noise HP
≤ 2 pA/rtHz≤ 6 pA/rtHz
5 pA/rtHzunknown
total output noise, referred to the photocurrent of an individual QD element
Photo current LP Photo current HP
≥ 1.5 mA≥ 15 mA
1.5 mA15 mA ? TBD
the quadrant diode must support at least this total photo current
Quant.effic. LPQuant.effic. HP
≥ 0.2 A/W≥ 0.2 A/W
0.4 A/W0.2 A/W
responsitivity of the quadrant diode at 1064 nm
Compatibility Compatible with old modules (see CRQ)
HP = high power modules (<= 30 mW)LP = low noise modules
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Additional requirements (I)Additional requirements (I)
Property Virgo+ requirem.
Component spec.
Notes
QD configuration
“+” config.
OK See following slide
QD size ≥ 10 mm diameter
11 mm
ΔPoffs ≤ 200 nW/degree
Offset drifts with temperature, in terms of equivalent incident power
Crosstalk between channels:
< 5% for optical excitation (6 MHz power mod.laser)
RF gain matching
< 1% 2% for optical excitation
RF phase matching
< 10° for optical excitation
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Comparison ‘X’ and ‘+’ configurationComparison ‘X’ and ‘+’ configuration
Relative sensitivity of X configurationVirgo QD’s are used in X configurationSame signal-to-noise-ratio as + config.
CouplingsHorizontal/vertical error signal couplingsX config: couplings for h+v miscentering
Misalignment sensitivityStrong horizontal or vertical misalignment:X config may give no error signal
ConclusionFor new QD front ends
“+” configuration desirable
vs.
8 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
Additional requirements (II)Additional requirements (II)
Property Requirem. spec. Notes
2 Omega suppression
≥ 30 dB Second harmonic of modulation frequency
Locally selectable RF atten.
0…40 dB
Integrated DC gain switch
Gain 1, 10
Saturation monitor
Saturation monitor
DC output low pass filters
LP filter (suppress >> 10 kHz)
Use same output filters as in Nikhef demod. Boards. Keep output filtering option open.
DC path whitening filters
Double Zero 2Hz ± 2.5% Q=0.5±5% / Double Pole20Hz ±2.5%Q=0.5±5%
See following slide
Diode windows AR coated
RF outputs 50 Ohm, trough transformer
9 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
DC signal whiteningDC 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)
End
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Geometrical specificationsGeometrical specifications
Geometry such that the front end holder can be re-used
Front end support structure
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Connector specificationsConnector specifications
connectors like on image
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Anti-aliasing filters Anti-aliasing filters
Presently 2 output filters in front end DC pathsimple poles 33 Hz & 85 Hz => Dephasing!Digital AA filters in readout chain possible? (To be verified)
delay 6 msec
DC filter + delay 6 msec
AC filter + delay 6 msec(filter in demod. board)
Frequency (Hz)
Dephasi
ng
(degre
es)
14 2nd Virgo+ review, Cascina 17/10/2007H. Heit mann
CRQ referee additions 08/2006CRQ referee additions 08/2006
Additional RequirementsCross-talk < 5%
optical exitationRF gain/phase matching: < 1%/10°
optical exitation Electronic isolation (ground not connected to bench) Geometrical/connection specifications
Additional FunctionalitiesRF saturation monitors for pre-amps (yel/red LEDs in front end)DC signal whitening (double zero at 2Hz, double pole at 20Hz)
Less important featuresLEDs 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)
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Diode materialDiode material
Important pointsMax. allowed laser powerQuantum efficiency @ 1064 nmDiameter >= 10 mm
InGaAsQuantum efficiency 0.7 A/W (up to 90%)Low bias voltage
=> high optical power possibleHigh capacity
but maybe OK with our low frequency?Large sized difficult
custom fabrication possible (Ø 10 mm)
SiQuantum 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
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Noise sourcesNoise sources
ADC noise2 uV/rtHz
Preamplifier noise5 pA/rtHz (1 quadrant element)typ. 50 nV/rtHz at front end output Demodulation board gain 200
10 uV/rtHz at ADC level AC80 nV/rtHz at ADC level DC
ConclusionDC signal below ADC noise level without pre-filtering