Superconducting Transition-Edge Sensors and Superconducting Tunnel Junctions for Optical/UV Time-Energy Resolved Single-Photon Counters NHST Meeting STScI - Baltimore 10 April 2003 TES & STJ Detector Summary Page 1
TES versus STJ Comparison TES E FWHM = 2.355 4 k B T e 2 C n 2 α STJ & L K E FWHM 2.355 E ε 0 ( F + G) n = 5 electron - phonon coupling T e T c E sat T c C α ε 0 1.7 1.7( 1.76kT c )= 3kT c F 0.2 is the Fano factor G 1-2 (tunneling noise) E FWHM = 2.355 6.4 k B T c E sat E FWHM 2.355 3.6kT c E E FWHM 15 mev E sat 1 ev 1/2 T c 70 mk 1/2 E FWHM 45 mev E 1 ev 1/2 T c 1 K 1/2 TES & STJ Detector Summary Page 2
STJ & TES Advantages Single photon counting Time-stamping (better than 0.1 µs is possible) Low resolution spectroscopy (R ~ 100 (λ/100 nm) 1/2 Broadband from near IR to far UV on up to x-rays Same technologies scale through large dynamic range High efficiency Greater than 50% in optical and UV With coatings nearing 100% is possible TES & STJ Detector Summary Page 3
Optical Photon Detectors Demonstration of W TES sensitivity active W sensor Al voltage rails Appl. Phys. Lett. 73, 735 (1998) B. Cabrera, R. Romani, A. J. Miller E. Figueroa-Feliciano, S. W. Nam TES & STJ Detector Summary Page 4
Monochromator Calibrations rail hits 2nd order IR thermal background TES & STJ Detector Summary Page 5
Background Subtracted Energy vs Phase Photon energy histogram Phase timing histogram TES & STJ Detector Summary Page 6
Calibration Data and PSF 8 Rate [khz/ev] 6 4 2.026 ev substrate hits rail hits substrate hits rail hits 2 Rate [khz/ev] 0 0 1 2 3 4 5 Photon Energy [ev] 8 6 4 2 1.000 ev thermal photons W TES Al/Si mask blocks substrate and rail hits 0 0 1 2 3 4 5 Photon Energy [ev] new design W TES TES & STJ Detector Summary Page 7
Optical 4 X 8 Imaging Array W TES imaging array with 20 µm x 20 µm pixels TES & STJ Detector Summary Page 8
Reflection mask keeps photons off of wiring and reflects those that would hit rails back into TES sensors Reflection mask TES & STJ Detector Summary Page 9
NIST Multiplexing Scheme for 32 X 32 array Talk by S. W. Nam SQUID amps at top of columns read row that is read C 1 read C 2 read C M 1 2 3 4 addressed 1 feedback 2 bias V 3 SQUID array 4 TES bias V V address R 1 V address R 2 address R N TES & STJ Detector Summary Page 10
TES versus STJ Comparison TES STJ E rms = 15 mev(t c /70 mk) 1/2 at 1 ev in principle Pixel size restricted by C Operate below 0.1 K (ADR) Control of T c Count rates ~ 10 khz SQUID readout R~20 at 3 ev in field 2 X 2 fiber coupled in field Multiplexing demonstrated TES & STJ Detector Summary Page 11 E rms = 45 mev(t/1 K) 1/2 at 1 ev in principle for Al Pixel size more flexible Operate below 0.3 K ( 3 He) Control of junction barrier Count rates ~ 10 khz FET readout R~5 at 3 ev in field 6 X 6 image array in field RF SET multiplexing ideas (new L K multiplexing idea) Most important: How to get to larger arrays!!
Expected Resolution 1000 500 200 Resolution 100 50 20 10 0.1 0.2 0.5 1 2 5 10 Photon Wavelenght [µm] TES & STJ Detector Summary Page 12
Best Applications Point source spectrophotometers Pulsars, neutron stars and black holes Redshifts of faintest galaxies Obtain direct redshift to 28 M v Excellent choice for combined x-ray, optical UV Many Constellation X sources are compact or faint Note: cryogenics for satellites will be solved by x-ray, EUV solar and CMB missions TES & STJ Detector Summary Page 13
Simulated Galaxy Observations from Space Z = 0.25 Z = 2 Z = 1 Simulated background subtracted spectra from one 0.1 pixel of a TES array on a 1 m aperture space passively cooled telescope, with 0.05 ev resolution and 10 hr exposure. Continuum breaks and a number of lines are well detected; broad (e.g., active galactic nucleus) lines are resolved in the blue. TES & STJ Detector Summary Page 14
Other Applications Order sorting spectrophotometer Higher efficiency and lower read noise than MCP with dispersive optics Not solar blind Requires filters (e. g. Woods filter) loosing efficiency May have lower backgrounds than MCP TES & STJ Detector Summary Page 15
Order Sorting Scheme 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 3 3.5 4 4.5 5 5.5 6 6.5 10 9 8 7 6 5 3 3.5 4 4.5 5 5.5 6 6.5 10 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 TES & STJ Detector Summary Page 16
STJ & TES Arrays Demonstrated 8^2 STJ imaging array by ESA 2^2 TES array by Stanford/NIST Under construction 10^2 STG imaging array by ESA 8 X 4 TES imaging array by Stanford In five to ten years 32^2 either TES multiplexing or one FET per STJ pixel 256 pixels programmable in a 1024^2 array 256^2 requires new ideas and electronics advances RF SET for STJ & kinetic inductance allow frequency domain multiplexing TES & STJ Detector Summary Page 17
For example: 1024^2 pixels of which 256 can be selected for a particular field and then another field can be programmed in. Programmable Large Array TES & STJ Detector Summary Page 18
Conclusions *TES Technology Ready for Initial Astronomical Application * Killer App Still Compact Object Spectrophotometry *An almost Perfect Detector (But still optics for Polarization) *Next: More Pixels and a ride to Space. TES & STJ Detector Summary Page 19
Simulate pulses including noise 1, 2, 3, 4 and 5 ev 0, 0.2, 0.4 ev, etc. Array of pulses for 1, 2, 3, 4, and 5 ev photons which include all Johnson and phonon noise terms Template array of 256 energies where noise terms set to zero TES & STJ Detector Summary Page 20
Compare with Theory The deviation of nonlinear results from square root energy dependence due to loss of high frequency information from time binning Dotted red lines are theory FWHM for 1 ev and 5 ev saturation and envelope following square root of energy dependence TES & STJ Detector Summary Page 21