Microwave SQUID multiplexing (umux) detector modules

Heather McCarrick (Princeton), Hannes Hubmayr (NIST), Adam Anderson (Fermilab), Ari Cukierman

(Stanford)

Design Overview recent example: BICEP/Keck umux with ~500 detectors

umux modules under development for 1800 detectors

Fermilab

● umux detector modules that are 1. compatible with arrays of 1800 detectors and 2. able to be tiled are currently under development.

● The module designs share fundamental parts (e.g. mux chips) but the components needing development differ.

● Module/packaging design is a focus of multiple groups involved with umux.

umux components

Cukierman et al. 2019

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SLACPrinceton & NIST

Key Components

1. Readout module

• umux channels: multiplexer chips• TES bias circuitry: ‘interface’ wafer(s)

or chips• Connection from module to cryostat

wiring• Connection from readout to TESs

2. Detector stack

• Detector array

• Optical coupling components

3. Primary optical coupling

• Horns or lenslets

umux components can be separated into an independent readout module for characterization before integration with the detector array into a detector module.

colla

psed

view

Example umux detector modules

detector array

backshortreadout

Interfaces within Module

umux modules

under development

umux to TES

umux to cryostat wiring

optical coupling

superconducting flex

Rogers and PCB board

Rogers and PCB board

wirebonds wirebonds superconducting flex/PCB

horns or lenslets

horns or lenslets

horns or lenslets

● The majority of interfaces within the modules are made with wirebonds. One design requires superconducting flex.

● Interfaces to the cryostat wiring are made with Rogers (RF) & PCB (DC) boards or superconducting flex (RF & DC).

● Compatible with horns and lenslets.

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horns or lenslets (current work on lenslets)

wirebonds + PCB

Rogers and PCB board

Interfaces from Module

100 mK - 300 K wiring chainFor an 1800 detector module, umux requires ● 1 or 2 pairs of coaxial cables for the RF signal● 1 DC cable (~37 pin) for the flux ramp signal, TES

biases, & cold amplifiers.

Connectors to/from module● RF: standard RF connector (SMA, SMP, etc.) ● DC: standard DC connector (MDM or zif)

300 K to 4 K wiring for the Simons Observatory SATs and LAT as shown in Sathyanarayana Rao et al. 2019

Example umux RF wiring diagram from Cukierman et al. 2019.

Connection to 100 mK stage● Standard mechanical mounting (e.g. an

interlocking flange)● Modules are designed such that the readout

components extend only in the z-axis, away from the sky

● The above two points allow for close packed modules

Challenges for scaling to S4

• Detector module designs all require some development, whether it be the RF packaging or the DC wiring

interconnects.

• Integrated module performance with 1800 detectors has not yet been demonstrated.

• Demonstration with 1800 channels in a detector module is the current focus of multiple umux groups.

• This includes recent R&D of umux detector modules has led to new designs, currently under testing, that

are expected to improve the RF grounding and environment as well as the interconnect robustness.

• Early module designs decreased the internal quality factor of the resonators; current module designs are

expected to show improvements.

Backup

Design 1: universal umux module-copper (UMM-Cu)

UMM-copper1. Mux chips: 28 multiplexer chips that cover an octave of

bandwidth with 1800+ readout channels.2. Routing wafer connects the multiplexer chips in series and

contains TES bolometer bias circuitry. Copper tray: ground and hosts multiplexer chips

3. Rogers board with surface mount SMPs: allow for z-axis entry 4. PCB board: allows for z-axis entry 5. Wirebonds to detector array: around perimeter (not pictured)6. One mechanical module

Microwave multiplexing modules require1. Multiplexer chips

2. Interface wafer(s) or chips

3. RF connection4. DC connection5. Connection from readout to detector array6. Number of mechanical packages

Highlights/status● Builds on the experience with the

UMM-Si● Designed for SO detector arrays● Expect improved RF & DC

connectors as well as a better RF environment and grounding

● Can inherent screening and assembly procedures developed for UMM-Si

● First prototype under testingRF connection

DC connection

routing wafer

150 mm

28 mux chips

copper tray

lid

Wirebonds to TESs around perimeter

Design 2: universal umux module-silicon (UMM-Si)

UMM-silicon1. Multiplexer (mux) chips: 28 multiplexer chips that cover an

octave of bandwidth with 1800+ readout channels.2. RF wafer: connects the multiplexer chips in series.

DC wafer: contains TES bolometer bias circuitry. 3. Superconducting flexible cable: allow for z-axis entry 4. Superconducting flexible cable: allow for z-axis entry 5. Wirebonds to detector array: around perimeter (not pictured)6. One mechanical module

Microwave multiplexing modules require1. Multiplexer chips

2. Interface wafer(s) or chips

3. RF connection4. DC connection5. Connection from readout to detector array6. Number of mechanical packages

Highlights/status● Design has been built and has

evolved for better resonator performance.

● Designed for SO detector arrays● Cryogenically robust● Readout components are easily

integrable with a detector array using wirebonds

● Screening and assembly procedures developed for all components

wirebonds to TESs around perimeter

base for readout testing

Design 3: umux stacking modules

umux stacking modules1. Mux chips: 28 multiplexer chips that cover an octave of

bandwidth with 1800+ readout channels.2. Interface chips: TES bias circuitry

Coax: connects mux chips in series3. Rogers board with panel mount micro SMAs4. PCB board5. Superconducting flex/PCB and wirebonds6. 14 modules connected in series

Microwave multiplexing modules require1. Multiplexer chips

2. Interface wafer(s) or chips

3. RF connection4. DC connection5. Connection from readout to detector array6. Number of mechanical packages

Highlights/status● Builds on the BKuMUX module

design● Designed for SO and BA detector

arrays● Uses vetted parts, mostly from the

BKuMUX demo● Individual packages can be tested ● Design under development

DC connection

RF connection

flex/PCB between readout and TESs

2 mux chip

interface chips

14 modules assembled in a double helix

Design 4: Fermilab detector testing module

UMM-copper1. Multiplexer (mux) chips: Test design has 10 mux chips, will be

extended after initial test.2. DC: superconducting PCB, investigating lithography by SeeQC

RF: coax3. Rogers board with panel mount micro SMAs4. PCB5. Superconducting PCB/wirebonds6. One mechanical module

Microwave multiplexing modules require1. Multiplexer chips

2. Interface wafer(s) or chips

3. RF connection4. DC connection5. Connection from readout to detector array6. Number of mechanical packages

Highlights/status● Design motivated by testing of

lenslet-coupled 100mK low-R detectors from Argonne

● Initial design for partial wafer readout complete

● Parts in fabrication now● Can be extended to read out a full

wafer● Considering SeeQC for

higher-density wiring layers