SLAC Advanced Instrumentation Seminar

Superconducting detector arrays: from Kent Irwin cosmology to nuclear non-proliferation NIST

ACT SZ sim

JCMT ACT The Quantum Sensors Project at NIST

James Beall Nathan Miller Sherry Cho Galen O’Neil Randy Doriese Carl Reintsema William Duncan Dan Schmidt Lisa Ferreira Joel Ullom Gene Hilton Leila Vale Kent Irwin Yizi Xu Rob Horansky Ki Won Yoon Ben Mates Barry Zink Outline

• Breakthroughs in superconducting and cryogenic technology are enabling practical large superconducting cameras and spectrometers

¾ Superconducting transition-edge sensors ¾ Micromachining ¾ SQUIDs multiplexers ¾ Cryocoolers

• Astronomical and particle physics applications have driven the development of superconducting detector arrays, but a broader variety of fields are being impacted

¾ Cosmology ¾ X-ray and submm astronomy ¾ Quantum information ¾ Electron probe materials analysis ¾ Security ¾ Nuclear materials ¾ Particle physics Applications of TES arrays Cosmology CMB, submm, x-ray Dark energy, inflation, neutrino mass… Astronomy submm, x-ray, γ-ray Planet/star/galaxy formation, WHIM, black holes…

Quantum information optical Quantum key distribution, computing Materials analysis x-ray Electron-probe materials analysis, synchrotron Security THz, γ, neutron Concealed weapons, Suicide bombers, nuclear smuggling Nuclear materials γ-ray, alpha, neutron Nuclear non-proliferation, forensics Particle physics Dark matter, neutrinos WIMPs, neutrino mass CDMS Thermal detection

X-ray Thermometer E C E τ = G C

C Temperature G Thermal Heat Conductance Capacity Time Photon → Heat Bolometers and calorimeters

Incident Radiation, P , E Thermometer, ΔT

P=G×ΔT Bolometer

E=C×ΔT Calorimeter Absorber (Heat Capacity C) Thermal Conductance, G

2 2 2 Thermodynamic power noise: NEP =4kbT G (W/√Hz) 2 2 2 Energy fluctuations: ΔErms = kbT C (J) Operate at low temperatures (T~ 0.1K to 0.3K) where C, G and thermodynamic fluctuations are small.

Response time: τ ∝ C/G (s) X-ray energy resolution

Thermodynamic energy fluctuations

Δ=EkTCrms B 2000 Ba Lα 1 BaTiO Ti Kα1,2 3 kB Boltzmann’s constant 1500 μcal EDS T Temperature of operation Si(Li) EDS 1000 Heat capacity C Counts Ba Lβ 1 Ba Lβ 500 3 • The energy resolution can be a Ti Kβ 1,3 Ba Lβ2

bit better than the thermodynamic Ba Lγ1 0 energy fluctuations. 4300 4600 4900 5200 5500 Energy (eV)

• At 6 keV, conventional semiconductor detectors have energy resolution as good as about 120 eV • TES x-ray calorimeters can have energy resolution ~ 2 eV – about 60 times better than SiLi. Superconducting Transition-Edge Thermometer

Transition-Edge Thermometer (TES) 0.06 TES thermometer membrane ) Ω 0.04

0.02 Resistance ( Resistance

0 95.8 96 96.2 Temperature (mK) Photon → Heat → Resistance Proximity bilayers

• A bilayer of a thin superconducting Copper Molybdenum film and a thin normal metal acts as a single superconductor with a Substrate tunable Tc - the “proximity effect”

• One example system is Mo-Cu Robust and temperature stable 0.06 Molybdenum Tc ~ .92 K )

Copper normal Ω 0.04

0.02

•Sharp Resistance ( • Reproducible <~ 5 mK 0 95.8 • Tunable 96 96.2 • Robust Temperature (mK) Other systems: Ti / Al, Mo / Au, W, Ti, etc. TES arrays 2001 – FIBRE 1 FIBRE 8-pixel bolometer array

2006 – SCUBA-2 subarrays

Three 1,280-pixel TES bolometer subarrays for SCUBA-2; with UK ATC; SMC Temperature self-biasing

Temperature self-biasing enables for large TES array applications

I

AsAs the the film film cools, cools, R0 → , , andand P Pjoule increases.increases. joule V

Stable equilibrium 2 V P = V 2 JOULE R TES = PSINK R Thermometer

Thermal P sink conductance Heat Sink If you cool the heat sink to well below the transition temperature of a voltage- biased TES, the TES will self-heat into its transition (electrothermal feedback). Micromachining

Silicon “Bricks” Spiderwebs NIST /SMC / ATC JPL / Caltech / UCB

Mushroom absorbers NIST / GSFC Popup bolometers GSFC SQUID readout

SQUID power: ~ nW per ‘on’ NIST channel – operate at base temperature

SQUID response

Input flux Multiplexing basis sets

Time division (TDM): different pixels at different times

~MHz TDM SQUID

SQUID Output SQUID switches

Frequency division (FDM): different pixels at different frequencies 100-SQUID series array for ~MHz frequency- domain readout with Berkeley/LBNL

SQUID Output SQUID Δ Temperature time Dissipationless rf SQUID multiplexer ~4-8 GHz Same idea, different orthogonal basis set Analog time-division multiplexing

• 2 x 2 array is shown as example of N-row by M- Each column array colored block is •TDM operation: 1 pixel – each TES coupled to its own SQ1 – TESs stay on all the time – rows of SQ1s turned on and off sequentially – SQUIDs are nonlinear amplifiers, so use digital FB Analog time-division multiplexing

Each colored block is 1 pixel Analog time-division multiplexing

Each colored block is 1 pixel

20 mm UBC Room-temperature electronics • Electronics – MCE from UBC – 8 columns per mux card, fully supported system, 10 person years of FPGA firmware development – NIST/UBC MUX used for One crate controls 1,280 pixels SCUBA-2, ACT, SPIDER, BICEP-2, SPUD, ClOVER, ZEUS…

Canadian SCUBA-2 Consortium 4K - 100 mK cryogenics

2-stage adiabatic demagnetization refrigerator (ADR)

• Cryocooler: no liquid cryogens • Push button operation from room temperature to 50 mK • Each magnet cycle gets you to ~ 45 mK and ~ 7 days < 100 mK • NIST-designed cryostat and insert; now commercially available Absorbers for the electromagnetic spectrum + beyond

submm/mm-wave: resonant cavity absorbers

Near IR & optical: TES with antireflection coating Soft x-ray: thick Bi (Nam / NIST / Stanford) “mushroom” absorber

submm/mm-wave: antennas 1 mm (Berkeley)

Gamma-ray: thick metal foil

Dark matter: thick Si or Ge crystals Submm astronomy: SCUBA-1

SCUBA-1 Survey of the galactic center

Artist concept

Detection of a gas giant around Fomalhaut Submm astronomy: SCUBA-2

James Clerk Maxwell Telescope • A collaboration of the UK, Canada, Raytheon, and NIST • SCUBA-2 will consist of 10,240 TES bolometer pixels (half at 450 μm, half at 850 μm) on the James Clerk Maxwell Telescope real soon. Submm astronomy: SCUBA-2 Deep- 1.135 1,280-pixel TES bolometer etched mm trench (10 Indium μm) Detector bump Wafer bonds (80 Quarter per pixel) SQUID MUX -wave Wafer Si Brick Nitride membrane TES (0.5 μm) 1,280-pixel SQUID Multiplexer

bump- bonded subarray (TES+MUX) THz/submm astronomy: SCUBA-2 Cosmology by the coordinated study of cosmic structure

CMB Cosmological Parameters

Optical Cosmic ν Mass structure

Dark energy X-Ray Eqn. of state X-rays and & WHIM cosmology

Allen et al., 2004 Most of the normal, baryonic matter Ia in clusters lies in the hot X-ray SN emitting gas (106 -108 K)

Probe of total mass of galaxy cluster – constrains cosmological CM parameters B X-ray Microcalorimeter Clusters Spectrometer (XMS) for Contellation-X, Con-X GSFC, NIST, etc. Chandra

Constellation-X Hot electron gas CMB: SZ Signature imposes a unique spectral signature Z-independent cluster surveys

145 GHz decrement

220 GHz null

270 GHz increment

NO SZ Contribution in Central Band

Devlin, ACT collaboration 1.4°x 1.4° The Atacama Cosmology Telescope - SZ

3,000 TES pixels (256 shown) Collaboration: Cardiff Columbia CUNY Haverford NASA/GSFC NIST PennPrinceton Rutgers Univ. de Catolica UMASS Univ of Toronto South Pole Telescope and APEX-SZ APEX-SZ, 320 pixels

SPT, 960 pixels

Berkeley, Chicago, etc.

(NIST SQUIDs) Future: TES CMB polarimeters for cosmology

• Signature of primordial gravitational waves

• CMB polarimetry microlensing: “cosmic shear” – Probe of expansion history of universe with different systematics

WMAP EE mode (HEMTs)

Polarization-sensitive TES provide excellent sensivity – need good systematic control Balloons: SPIDER, EBEX Ground-based: BICEP-2, SPUD, ClOVER, SPT, ACT, … CMB polarimetry and primordial gravity waves

recombination reionization

The universe is opaque to photons before 380,000 years: but not to gravitational waves and neutrinos • Detection of the cosmic gravity wave (CGB) background would probe the inflationary era (10-35 s?) e

p Surface of Last Scattering • Direct probe of inflation vs. cyclic / ekpyrotic models n He

380,000 yr atoms form 400 million yrs Stars form Density-Wave vs. Gravity-Wave Anisotropies Density-wave anisotropy

Two different types of anisotropies: 1. Decompose the temperature and gravitational wave distribution at the surface of last scattering into a superposition of plane waves 2. The two types of waves will produce quadropole temperature anisotropies with different spin Gravitational-wave anisotropy 3. Integrate the light from all directions scattering off towards the observer 4. The characteristic anisotropies of gravitational waves result in polarization with a curl-like symmetry (BB)

Credit: Wayne Hu, Chicago CMB polarization so far (no gravity waves)

DASI: EE polarization of the CMB; small angular scale

WMAP: EE polarization of the CMB; large angular scale TES polarimeter arrays

GSFC: metal platelet feedhorns Berkeley: planar antennas

NIST: silicon micromachined JPL/Caltech: beam-synthesized antennas corrugated feeds

Feedhorn array cutaway

Polarimeter Backshort Gamma-ray: nuclear non-proliferation About 96 % (>600 tons) of the all the Pu under International safeguards is in spent fuel. Is it all where it is supposed to be? Is any of it missing?

Current IAEA Methods γ spectroscopy Gross neutron Calorimetry Computer models Operator’s reactor history Limited destructive analysis Containment and surveillance

Spent fuel in North Korean cooling pond Nuclear materials assay

• Nuclear materials (various isotopes of U, Pu, etc.) emit characteristic γ rays and X rays around 100 keV.

• Industry-standard 100 keV spectrometer is HPGe: – best ΔE ~ 500 eV (can’t resolve some important lines) – active collecting area ~ a few cm2 – max count rate ~ 50 kHz • Arrays of TES microcalorimeters promise much better energy resolution, comparable collecting area and count rate.

Efforts at LANL / NIST and LLNL TES Pu spectrum measured at LANL

1 mm

Sn absorber Mo/Cu TES TES Pu spectrum measured at LANL

Key measurements:

• Pu isotopes 239Pu : 240Pu γ ray (239Pu = weapon) TES Pu spectrum measured at LANL

Key measurements:

• Pu isotopes 239Pu : 240Pu γ ray (239Pu = weapon)

• spent reactor fuel (different spectrum):

Pu Ka1 : U Ka1 x-ray fluorescence ratio (learn total Pu content without knowing reactor history) TES Pu spectrum measured at LANL

Key measurements:

• Pu isotopes 239Pu : 240Pu γ ray (239Pu = weapon)

• spent reactor fuel (different spectrum):

Pu Ka1 : U Ka1 x-ray fluorescence ratio (learn total Pu content without knowing reactor history) Need TES arrays: HPGe: t = 15 minutes ucal: t = 7 hours Batch fabrication of TES γ-ray arrays std. Mo/Cu TES process; stamp-print glue glue on absorbers add lithographed epoxy posts onto epoxy posts to complete array 1 3 5

grey = TES cyan = epoxy post

2 4

6.25 mm

dark blue = glue yellow = Sn absorbers spin-coat another micro-machined “egg crate” Si wafer w/ glue containing Sn absorbers NIST/LANL 1st generation γ-ray arrays MUXed spectrum of 153Gd γ-ray source 13 coadded pixels 1351 eVcoadded FWHM at 103 pixels keV 600

6.25 mm 500

400

300 51 eV 200 counts / 5 eV bin

100

0 gamma-ray arrays 103.0 103.2 103.4 energy (keV) Best pixel

70

60

50

40 27 eV

30 counts / 4 eV bin 20

10

0 103.10 103.20 103.30 energy (keV) 14-pixel γ-ray array system delivered to LANL 2nd-generation γ-ray arrays

Four 66-pixel array chips

Pixel from underneath

1.5 mm

NIST/LANL absorber removed HEU Detection

Discrimination of 235U from 226Ra “The Kitty Litter Problem”

simulation High resolution α spectroscopy Alpha spectroscopy is a powerful tool for low level actinide measurements (μg – pg)

Approximately 3,000 samples analyzed per year at LANL for the IAEA and others

Poor resolution of conventional alpha spectroscopy (10-30 keV) is a problem: Can’t split 239Pu/240Pu → drives use of slow and expensive mass spec Elemental overlaps → slow and expensive wet chemistry to separate

2500 Typical Pu Alpha Spectrum 239Pu Alpha Particles 240Pu Alpha Particles data 2000 239Pu 1500 240Pu Counts 1000

500

0 4800 4900 5000 5100 5200 5300 5400 typical alpha samples Energy (keV) typical alpha spectrum High resolution α spectroscopy

Pu sources and mounting hardware Completed sensors

4 mm

absorber removed

0.4 mm electroplated mixtures of Pu isotopes thermometer and below 2 nCi (Boulder limit) posts for absorber Alpha spectroscopy of 209Po/210Po

300 300

210 209 250 Po spectrum 250 Po spectrum satellite line - 2.46 keV resolution never before unknown high E shoulderobserved 200 200

in-source straggling 150 (expected) 150

100 100 counts / 250 eV bin / 250 counts counts / 250 eV bin

50 50

0 0 5290 5295 5300 5305 5310 5315 4870 4875 4880 4885 4890 4895 energy (keV) energy (keV)

world-record resolution: 2.46 keV at 5.3 MeV First splitting of 239Pu/240Pu α lines Applications of TES arrays Cosmology CMB, submm, x-ray Dark energy, inflation, neutrino mass… Astronomy submm, x-ray, γ-ray Planet/star/galaxy formation, WHIM, black holes…

Quantum information optical Quantum key distribution, computing Materials analysis x-ray Electron-probe materials analysis, synchrotron Security THz, γ, neutron Concealed weapons, Suicide bombers, nuclear smuggling Nuclear materials γ-ray, alpha, neutron Nuclear non-proliferation, forensics Particle physics Dark matter, neutrinos WIMPs, neutrino mass CDMS Microwave SQUID multiplexer

pixel feedline rf-SQUIDs (flux variable inductors) HEMT • unshunted + non-hysteretic • dissipationless resonator • CPW resonators similar to MKIDs, P. Day et al, Nature (2003) pixel variety #1 • Junctions tune microwave resonances coupling T

resonator detector filter SQUID Measured resonance at 3 flux values

Chip with one feedline; 32 dissipationless SQUIDs Results

Initial prototypes work well Transmitted phase as a function of flux • 32 resonators on feedline • Q = 4,000-20,000 at 5 GHz • Resonator accuracy compatible with > 1,000 SQUIDs per HEMT • Parasitic power loss (in dielectric) ~ 5 pW 100 kHz • Stable operation calibration tone

• Noise dominated by dielectric: Φ =Φ0.17μ Hz n 0 0.17 Hz Φ=n μ Φ0 at 100 kHz • Input low-pass filters block microwaves from detector • Now working coupling to TESs Flux-ramp modulation

Microwave MUX SQUIDs operate open loop (no feedback, Data: recovery of exponential input signal with flux-ramp modulation but flux modulated)

)

• One common “flux ramp” wire 0 phase Φ 0.5 for all SQUIDs time • 10 kHz sawtooth current on flux ramp wire with 10 Φ0 amplitude → SQUID response modulated at 100 kHz, above dielectric noise

• Detector signal recovered from 0 phase of modulation

Input adRecovrFlux( Should be possible to operate 0 10 Time (ms) >1,000 SQUIDs with two coax cables (input & output), one Red: input flux HEMT, and one flux-ramp wire Green: reference baseline White: signal measured from phase Applications of TES arrays Cosmology CMB, submm, x-ray Dark energy, inflation, neutrino mass… Astronomy submm, x-ray, γ-ray Planet/star/galaxy formation, WHIM, black holes…

Quantum information optical Quantum key distribution, computing Materials analysis x-ray Electron-probe materials analysis, synchrotron Security THz, γ, neutron Concealed weapons, Suicide bombers, nuclear smuggling Nuclear materials γ-ray, alpha, neutron Nuclear non-proliferation, forensics Particle physics Dark matter, neutrinos WIMPs, neutrino mass CDMS Electron-probe materials analysis

128-pixel x-ray array X-ray TES on an SEM

2000

Si K α1,2 WSi 2 on SiO2

1500 Microcalorimeter

ED S sp e c t r o meter 1000

WMα1,2

WMβ 500 Si K β

WMζ 1,2 WMγ 0 1400 1600 18002000 2200 En e r g y (e V) Thin-Film Analysis

The high energy resolution of the microcalorimeter also provides a high peak-to-background ratio, allowing better thin film & trace element analysis

1600 TaSiN thin films NIST μcal EDS on Si (SUNY-Albany) 3 keV beam energy 74 nm 1200 ~500 s-1 input rate 32 nm 400 s live time 12 nm ~0.6 nA beam current 800 7.5 nm 3.5 nm

Counts Ta Mα Si Kα 1,2 400 Ta Mβ Si Kα 3,4 0 1700 1725 1750 1775 Energy

Ref. Geer et. al. Nanoscale Particle Analysis

• Contaminant particles in semiconductor processing lower yield • Low beam energies to localize x-ray production in ~60 nm particle • High energy resolution to resolve overlapping x-ray lines

Low beam energy; x-rays from particle

High beam energy; x-rays from substrate Resolving peak overlaps

The need for low-energy analysis of small particles means that many peaks are overlapping when measured with SiLi

2000 Ba Lα 600 N Kα 1 TiN Ti Kα BaTiO μcal EDS 1,2 3 1500 SiLi EDS μcal EDS 400 Si(Li) EDS

1000

Counts Counts Ba Lβ1 200 Ba Lβ (Ti LA Ti Lα 500 3 1,2 Ti Kβ Ti Lη) 1,3 Ba Lβ2 Ti Lβ1 Ti Lβ3,4 Ba Lγ1 0 0 360 400 440 480 520 4300 4600 4900 5200 5500 Energy (eV) Energy (eV) Trace-Element Analysis

The high energy resolution of the microcalorimeter also provides a high peak-to-background ratio, allowing better thin film & trace element analysis

2500 850 900 950 1000 Si-K

NIST μcal EDS Cu Lα1,2 2000 100 3 keV, 1.3 nA 500 s-1 input rate 1000 s live time W-M 1500 Cu Lβ

1 0.70.7 wt.wt. %% CuCu 50 measuredmeasured inin WSiWSi2 1000 W-M thinthin filmfilm 0 500 Cu-L

cal Counts (0.16 eV/channel) O-K W-M μ 0 500 1000 1500 2000 Energy (eV)

Collaboration with Vartuli and Stevie (Lucent) Chemical shift analysis

120 300 100 Heat pulse 80 200 Al Ka1,2

60 Counts 40 Counts 100

20 Al oxide particle 0 0 1460 1480 1500 1520 Energy (eV)

• Chemical bonding state causes small (< 1 eV) shifts in x-ray line position • Industrially important problem: Al particles on oxide substrates.

Particle samples provided by Al particle Alain Diebold (SEMATECH) Chemical shift map

0.6

0.4 eV Δ 0.2

0

Al oxide Al