112 Pixel Arrays of HighEfficiency STJ Xray Detectors

112 -Pixel Arrays of High-Efficiency STJ X-ray Detectors Stephan Friedrich Matthew Carpenter LLNL (Detector Testing) Synchrotron Science John Hall Robin Cantor Star Cryo (Fabrication) ALS, SSRL Jack Harris Bill Warburton XIA (Electronics) This work was funded by DOE grants DE-SC 0006214, DE-SC 0002256 and SC-0002256. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC 52 -07 NA 27344.

Superconducting Tunnel Junction Detectors STJ Operating Principle X-ray Photon Al 2 O 3 Si. O 2 Ta Al Al Al. Ox Ta Ta Absorber Al Al Nb ΔAl Si Substrate 200× 200 μm 2 ΔTa Signal = Current pulse Energy resolution ∆EFWHM = 2. 355√(εE(F+1+1/<n>) Small energy gap (Δ ≈ 1 me. V) ⇒(Comparably) high energy resolution (<10 e. V FWHM) Short excess charge life time (~µs) ⇒(Comparably) high count rate (>5, 000 counts/s) 06/26/2013 LTD-15, Pasadena

STJ Performance (as of LTD-14) Single-pixel spectrum of Mn. O + Fe 7(CN)18 on Al 06/26/2013 Resolution vs. Count Rate LTD-15, Pasadena

At the Synchrotron, We Need Efficiency Options: 1) Increase area/pixel 2) Thicker Ta absorber 3) Arrays: Detectors, readout Single Pixel 36 Pixels 200 x 200 µm 2 112 pixels of 200 x 200 µm 2 STJs ⇒ Matt Carpenter (Monday talk) For details on fabrication, ask Robin Cantor at the STAR Cryoelectronics booth. 06/26/2013 LTD-15, Pasadena

Scalable 32 -Pixel STJ Preamplifier Old: Single channel New: 32 channels STJ RF STJ IX en Rdyn Vout=IXRF Vbias Existing preamp works fine, but is too big, too expensive (~$1 k) and bias is manual. 06/26/2013 Preamp en IX Rdyn Controller Vout=IXRF Vbias from DAC New preamp has same noise, but is small, cheap ($25 in parts), and remote-controlled. LTD-15, Pasadena

Small, Cheap, Remote-Controlled Preamp Simultaneous bias scan of all pixels: Average current provides I(V)… 06/26/2013 … rms fluctuations measure noise. For details, ask Bill Warburton at XIA LLC LTD-15, Pasadena

X-ray Spectra at LLNL With new 32 -channel XIA preamp (and 32 -pixel digitizer / DSP board): With old single-channel preamp: 27 of 32 pixels tested have high resolution (rest is either open or shorted). 06/26/2013 LTD-15, Pasadena

More X-ray Spectra from Same 112 Pixel array With new 32 -channel XIA preamp (and 32 -pixel digitizer / DSP board): With old single-channel preamp: 26 of 32 pixels tested have high resolution (rest is either open or shorted). 06/26/2013 Ta STJs seem to trap flux more easily than Nb STJs. LTD-15, Pasadena

Sum Spectra 53 pixels of 112 -pixel STJ array, 165 nm Ta absorber With old setup, rise time discrimination can be used to veto bottom layer events. ⇒ a) Implement veto in XIA DSP, or b) Make STJs with thicker Ta absorber 06/26/2013 LTD-15, Pasadena

X-ray Absorption Spectroscopy with STJs Synchrotron Sample x Detection Monochromatic, intense X-ray beam Absorption µx(E) Three options: Monochromator vacuum valence levels core levels Electron yield: Sample surfaces Moderate bgnd. Fluorescence: Bulk samples Low background Sample Transmission: Thin samples High background Scan energy of X-ray beam, measure absorption (by transmission, e-yield or X-ray yield) Fluorescence-detected XAS provides highest sensitivity, if the detector used can separate the fluorescence of interest with high efficiency. 06/26/2013 LTD-15, Pasadena

Organic Photovoltaics (“Plastic Solar Cells”) • Cheap, light, cheap, flexible, cheap… • Not as efficient yet, ~12% max in the lab • Efficiency depends on microstructure Ca-L-edge Absorption Spectrum with Ca electrode removed. Bulk hetero-jct. active layer Ca/Ag ele ctr P 3 HT - PC ode PEDOT: P BM ITO elect SS rode Glass sub strate 06/26/2013 For details, ask Adam Moulé at UC Davis LTD-15, Pasadena

Organic Photovoltaics (o. PV) Ca XAS of organic PV material (PCBM) C XAS: Occupancy at EF changes: Doping! Energy levels: Band gap EF(Ca)=-2. 9 e. V Ca diffuses from electrode into active area! EC(o. PV)=-3. 7 e. V EF(Ag)=-4. 6 e. V EV(o. PV)=-6. 1 e. V Electrode materials can serve as dopants. S. Mauger et al. , Adv. Funct. Mater. 23, 1935 (2013) 06/26/2013 LTD-15, Pasadena

112 -Pixel Ta-STJ X-ray Detector Arrays • ~5 to ~10 e. V FWHM below ~1 ke. V, ~5000 counts/s per pixel • 112 -pixel arrays have high uniformity, 8 -9 e. V FWHM, ~75% yield (STAR Cryo) • Computer-controlled 32 -channel pre-amplifier and digitizer cards (XIA LLC) • Chemical analysis of dilute samples (e. g. organic solar cells with UC Davis) 06/26/2013 LTD-15, Pasadena