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Neel IRAM KIDs Array

Neel IRAM KIDs Array. Cryostat Filters Cold electronics Measurement methods and assumptions for Sensitivity calculation Antenna-coupled 42 pixels KIDs (first option) 32 pixels LEKIDs (second option) 196 pixels LEKIDs (TBT) Best LEKIDs pixel tested in Cardiff (for 2010 …). 1K.

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Neel IRAM KIDs Array

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  1. Neel IRAM KIDs Array • Cryostat • Filters • Cold electronics • Measurement methods and assumptions for Sensitivity calculation • Antenna-coupled 42 pixels KIDs (first option) • 32 pixels LEKIDs (second option) • 196 pixels LEKIDs (TBT) • Best LEKIDs pixel tested in Cardiff (for 2010 …)

  2. 1K 300K 0.1K 160K 80K 4K The Cryostat Optics Designed for f/1.6 on the detectors (from f/10 at M8). De-magnifying factor: 6 300K: ZITEX G110 HDPE (t=10mm) window Thermal Filter (metal-mesh) 150K: -- 80K: 2 thermal filters (metal-mesh) 1 low-pass filter 270GHz 5K: 1 low-pass filter 240GHz L1 – HDPE lens (t=11mm) 1K: 1 low-pass filter 210GHz 100mK: Reflecting Baffle L2 – HDPE lens (t=12mm) Low-pass filter 170GHz High-pass filter 130GHz (optional) bandpass 130-160GHz 4th Sepember 2009: added new 4K baffle (ECOSORB inside) + ZITEX G110 at 80K

  3. The Filters • 4 thermal (including ZITEX) • 4 low-pass • 1 high-pass • HDPE window and lenses are • not AR-coated. • We have 4.5% loss at • each surface, plus 10+11+12mm • Bulk absorption. We estimate • THDPE=0.7 Band: 130-170GHz Filters transmission: 0.5 HDPE transmission: 0.7 So our best estimation of the in-band transmission is Total Transmission  0.35

  4. Cold Electronics • We can now easily (cabled for both down to 4K, just has to un-screw the amplifier) • change between: • IRAM cryogenic amplifier 1÷2 GHz. Tnoise = 5K. Power dissipated: 50 mW • LNF cryogenic amplifier 3÷9 GHz. Tnoise = 5K. Power dissipated: 4 mW • Still waiting for the Caltech 1÷12GHz amplifier. • Both are mounted at 4K. The IN of the amplifier is connected to the array with: • 15cm superconducting NbTi 1.6mm semi-rigid COAX (thermalised at 1K) • 16cm Copper 2.2mm semi-rigid COAX (at 100mK)

  5. 1K 300K 0.1K 160K 80K 4K Measurements « protocol » Everything on XY stage 580 mm 750 mm CHOPPER 77K / 300K 30x30cm ECOSORB 77K ECOSORB 77K 12 mm dia. hole in the 2nd ECOSORB 2nd ECOSORB is to fake M8 in some way (not perfect)

  6. Estimation of the power 1/2 • Assuming h<<kT (OK): • So, between 300K and 77K (perfect emissivity): Pe = 0.2 mW/m2 (max=170GHz, min=130GHz) • Power emitted over the 2π, both polarisations, with a cos() distribution. • For a chopped Φ=12mm surface (S = 1.1·10-4 m2)  Pchopped = 22nW • The Lambertian « beam » is propagating forward toward the 4K lenses, d=80mm and distance • D=750mm from the chopper. The 4K lens collects the part going mostly on the focal plane. • So the useful fraction of solid angle is: • frac = (πd2/4) / (2πD2) = (1/8)·(d/D)2 = 1.4·10-3 • Total transmission (from the chopped source to the array): • Filter + lenses TFL = 0.35 (0.45 possible) • Cold pupil cutoff (cutting the external ring) TCP = 0.8 • Measurement system (from chopper to cryostat): TCH = 0.5 (n.a. on the sky) • - TOTAL TRANSMISSION T = 0.14 (0.36 possible)

  7. Estimation of the power 2/2 So we have: P  frac· TTOT· Pchopped  4 pW Total power, in the two polarisations, hitting the focal plane and spreading (PSF - gaussian 2-D distribution) on a number of pixels to be determined experimentally (aberrations + diffraction). ZEMAX full 3-D simulation (better calculating the pupil cut and taking properly into account the Lambertian and extended nature of the emitter). PZEMAX = 5.9pW (Basically estimating frac in 3-D ray-tracing) Now, the mean beam FWHM is fitted to be 31mm. It means, roughly, a factor (12/31)2 = 0.15 Working out the integral of the gaussian in 2-D we find a factor of 0.098 instead. So, the power hitting the pixel in this model is 5.9 · 0.1 = 0.59 pW (2 polarisations) In case of the measurement of the SRON array, since we have used an additional filter 2mm, we estimate 0.4 pW instead of 0.6 pW.

  8. The antennas 42 (6x7) pixels array – XY scan PIXELS identifications: 37/42 working pixels. Mean inter-pixel distance: 10mm (means f/1.6 on focal plane, dpixels=1.6mm) Mean beam FWHM: 30mm

  9. The antennas 42 (6x7) pixels array: XY scan PIXELS identifications: 37/42 working pixels. Mean inter-pixel distance: 10mm (means f/1.6 on detectors plane, dpixels=1.6mm) Mean beam FWHM: 29 mm

  10. The antennas array: FPGA sensitivity Sensitivity measured with FPGA electronics, LNA at 4K mounted, Grenoble Up/Down converter. It seems it’s still limited by the background.. May be some excess phase noise ? NEP are for the 2 polarisations !! Should divide by 2 to be fair .. NEP1Hz 2·10-15 W/Hz0.5 NEP10Hz 7·10-16 W/Hz0.5

  11. The antennas array: Bonn sensitivity From Andrey.

  12. Antennas MKIDs next steps • Improve f-distribution (possible before Oct) • Change to optimum f-distribution on chip • Use e-beam mask (current is optical) • Improve coupling • Current lens array E=2.7 instead of 5 (loss 3dB) • Change extension length (possible before Oct) • Change lens material (Spring) • Possible to Niquist reduce oversampling (max gain 6dB) • Improve F-noise • Integrate capacitor at coupler (demonstrated at JPL) improves phase noise by 10dB • Multi frequency pixels (+ kid parametric optimization) • Optimise for operation under sky loading

  13. LEKIDs: 32 pixels focal plane scan 24 working pixels within the 48 MHz band of the FPGA electronics. FWHM = 31+/-4 mm It’s OK !

  14. LEKIDs: 32 pixels unchopped Image of two hot spots on the focal plane; no chopper

  15. LEKIDs: 32 (4x8) pixels array (NEP)

  16. LEKIDs: 32 pixels focal plane scan PIXELS identifications: 28 working pixels, but only 24 within the FPGA bandwidth Mean inter-pixel distance: 12mm (means f/1.6 on detectors plane, dpixels = 2 mm) Mean beam FWHM: 31 mm

  17. LEKIDs: 196 (14x14) pixels array CAREFUL: still to be tested with the Bonn electronics (need to change to 16k bins) and in the same background conditions. Scheduled when we repair the cryostat. • S/N ~ 1000 (down to 0.5Hz) • S/N ~ 200 (at 0.1Hz) but … • (dia. pupil 2cm) • Assuming 0.5pW power • NEP ~ 5·10-16W/Hz0.5 Ongoing to improve: • 16-32 pixels arrays (FPGA electronics) • Fabrication on Sapphire • Change of resonator impedance (phase noise • and power handling) • Cryogenic amplifier (amplitude readout) • Better control of backshort distance • Superconducting box + filter (Cardiff) • Post-processing: KIDs circle calibration • Test with Bonn electronics to read-out the • whole array. CHOPPER NO CHOPPER

  18. LEKIDs: Best Pixels Tested • Border conditions: • - 40nm film (UHV at SRON). • - Less C fingers • (helps reducing the phase noise) • - Tested in low background • environment (Cardiff). • (0.1pW per pixel) • To further reduce the NEP: • - Change the impedance of • the resonator • - 2 polarisations design • fabricate on sapphire • - further optimise the electrical • power on the KIDs • - use an additional AR coating • - optimise the film thickness • …..

  19. Bonn Electronics Available in Grenoble since end of July. Bandwidth: 400 MHz Max. readout rate: 10 Hz FFT points: 8,192 / 16,384 Bins spacing: 48.8 / 24.4 kHz Interfaced with Acquisition program  OK

  20. Néel FPGA Electronics Bandwidth: 48 MHz Max. readout rate*: 100 Hz Max. number of channels 27 * Can be used also for fast (MHz) read-out. Interfaced with Acquisition program  OK

  21. Electronics developments USA Open Source: DAC and ADC boards OK up to 500MSPS. Developing the CASPER Core. We’ll have two full copies, with the possibility of using them in parallel. Same concept as FPGA readout. Minimal goal: 128 channels each board (256 hopefully) Delivery: end 2009 ? LPSC, Grenoble: Making a « copy » of our FPGA, but with 200MHz bandwidth and able to read at least 64 channels. Prototype delivery: November ? Bonn: planning 32k bins and 800MHz bandwidth.

  22. Conclusions • Demonstrated NEP is not exceptionally low • BUT: • Imaging capabilities OK for both antennas and LEKIDs • Expected better performances on the telescope • (background limiting both Qi and qp) • Need to understand real problems at the 30-m • Developments are ongoing to reduce the NEP. • For both LEKIDs and antennas.

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