Review on bolometer technologies - APC

Large number of experiments using spiderweb+TESThe membrane can be taylored to match the incident power depending on the experiment (balloon, ground based, …)Bolocam 2.144 spiderweb for the Large Millimeter Telescope(50m telescope, Puebla – Mexico)6 x 55 = 330 spiderwebEBEX balloonAPEX-SZSouth Pole Telescope (SPT)It is difficult to realize monolithic bolometers of ~1000 pixel spiderwebs.Assembly of many sub-arrays to get big matrixesWell suited for feedhorns but difficult to get a big imager without horns

HERSCHEL PACS high impedance sensor photometer (200µm and 450µm)CEA-LETI Franceλ/4 cavity pixel8 x 256 pixelIndiumbumbsλ/4Si:P BImplantedAugrid8 subarrays each containing 256 bolometers.Thermistor impedance ~ 10GΩ to increase sensitivity andmatch the CMOS noiseA first electronic stage (impedance reduction) is located belowthe quarter wave cavity reflector, at 300 mK.CMOS transistors at 2K located a few cm below the pixelsperform the multiplexingCMOS-based fabrication process is well controlled.Direct imager, feedhorns or antennas are not neededGΩ impedance bolometers are vulnerable to E.M. interferenceDifficult to extend to wavelengths>1mmNew prototypes are develloped for the APEX ground telescope and the SPICA satellite mission(Candidate for the 30-210µm detector of the SPICA Fourrier Tranform Spectrometer SAFARI)

SCUBA 2 TES imager. (450µm and 850µm)Studies of stars, planets, galaxy formation in the early universeLarge-area surveys4 × 1280 pixel sub-arraysMoAu TES on Si 3N 4membrane (100mK).NEP 3·10 -17 W/√Hz and 15·10 -17 W/√Hz (@ 850 and 450µm)Time-domain multiplexing1280-pixel array chipOptimized absorption usingquarter wave Si slabSi slab

1 operational pixel is easy1000 operational pixels is a big challenge

Feed-horns - λ/4 cavities - antennasHorns:Well defined field of viewThroughput is single-modedBolometer in integrating cavity…EBEXAntennas:Power can be dissipated in a very small membranePower can be dissipated directly in the sensor (HEB)Can be polarization-selectiveWideband antenna + microstrips filtrering the band…Combining horns and antennasis possible

POLARBEARPower is absorbed hereTES sensor is here

JPL Antenna-coupled bolometer, and crossed dipole elements8x8 array, 2 polarizations simultaneously

Hot electron bolometers (HEB)TiN, NbN, NbSi…Energy is directly absorbed by the electrons of the sensor without phonon mediation.Electron-phonon decoupling is weak enough at low temperatures to replace membrane decoupling.Advantages:Simplification and reliability of fabrication process with high number of pixels.Nb x Si 1-x (CSNSM France)Coupled to antennas ordirectly absorbing incident radiation (Absorption-Temperature measure-Decoupling in the same material)G is proportional to NbSi dimensions100µm x 100µm x 0.1µmNbSi sensorPlanckdecouplingDirect absorbtion: R square→377Ω (vacuum impedance)adjusted by the thickness and composition x of Nb xSi 1-xNEP performances will be soon tested at 40mK

Pair-breaking detectors (STJ, MKID)Incident energy is not detected by its thermal effects (temperature rise).Energy breaks Cooper-pairs of a superconductor and creates quasiparticles(analogous to photoconductors with ~meV gap)Quasiparticles can be measured:• Using a tunnel junction (STJ)• Variation of kinetic inductance (MKID)• Trapped into a TESAl (and sometimes Nb) superconductors are actually used.Operates well below Tc to reduce quasiparticle generation-recombination noise.No need to precisely regulate the cryostat.

Microwave Kinetic Inductance Detectors (MKIDs or KIDs)Quasiparticle creation changes the kinetic inductance (surface reactance) of superconductor.Making the superconducting film part of a resonant circuit, capacitively coupled to a through line, results inchange of amplitude and phase of a microwave probe signal→ Very sensitive® Easy frequency-domain multiplexing in the GHz rangeMKID16-pixel arrayPixel designEach pixel has a 16-slot phased array antennaCamera with 16 tiles of 36-4color pixels under construction(Caltech Submillimeter Observatory)• 576 pixels, 2304 resonators, 8 coax + HEMT

10% bandwidth around 675 GHzfully scalable from 100 GHz(limited by the material used) to > 5 THz.MKIDMKIDs frequency-domain multiplexingcryostatUltimate limit: intrinsic quasiparticle generation-recombination noise which can be as low asNEP ~ 10 -20 W/√Hz at temperatures below 1/10 of the transition temperature of the superconductor.

CONCLUSIONBolometers are very sensitive devices with photon-noise limited performancesTechnologically very active field at present:• new sensors• new multiplexing techniques• cryogenics, electronics, antennas, optics …Very exciting physics will be done:CMB, X-rays, Dark Matter, Neutrino mass…

LABOCA Large APEX Bolometer Camera (870µm)Max Planck institut fur RadioastronomieSHARC-2 @ CSO(384 elements @ 350 m)295 square pixelsSensor: NTD GeWith hornsNo multiplexing12x32 array of doped silicon pop-upbolometers, developed by Moseley et alat GSFC, cooled with He to 0.3 K.

Superconducting detector R&D for the future(2007 ~ )Joint effort withRIKEN, TIT, TohokuPart of activities inside the KEK Detector Technology ProjectCMB as an important application, but not exclusiveCurrent target:Pure Al STJ sensors for ultra-fast/large-dynamic range mm-wave cameraJoint R&D on TES with UC Berkeley/LBNL proposedNew !