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We are developing lab-based readout electronics for Transition-edge sensors (TES) using commercial-off-the-shelf (COTS) modules. These COTS modules are advantageous since they increase development speed and keep the cost low. We have developed these electronics to support both non-multiplexed and time-division multiplexing (TDM) readout systems. The system utilizes remote control via Ethernet, and the interface allows many types of measurements to be automated. With the TDM readout system, we have achieved 2.05 eV at 6 keV, 2.1 eV at 7 keV, 2.3 eV at 8 keV, and 2.8 eV at 12 keV with 2-column × 32-row multiplexing. We will be using this system in the characterization of detectors for the X-Ray Integral Field Unit (X-IFU) instrument on Athena. In this paper, we present an overview of the design and their performance. [ABSTRACT FROM AUTHOR]

Time division multiplexing (TDM) uses a digital flux-locked loop (DFLL) to linearize each first-stage SQUID amplifier. Presently, the dynamic range of our TDM systems is limited by the use of a proportional-integral controller to maintain the DFLL. In this paper, we use simulations to assess the improvements possible with a predictive control algorithm that anticipates rapid changes in transition-edge sensor current during the rising edge of an X-ray pulse. We calculate that the predictive control algorithm can improve our TDM architecture's dynamic range by 35%. This significant increase in multiplexing capabilities could be used to read out higher-energy X-rays, reduce readout noise, increase multiplexing factors, or reduce SQUID power output. [ABSTRACT FROM AUTHOR]

Multiplexers based on the modulation of superconducting quantum interference devices are now regularly used in multi-kilopixel arrays of superconducting detectors for astrophysics, cosmology, and materials analysis. Over the next decade, much larger arrays will be needed. These larger arrays require new modulation techniques and compact multiplexer elements that fit within each pixel. We present a new in-focal-plane code-division multiplexer that provides multiplexing elements with the required scalability. This code-division multiplexer uses compact lithographic modulation elements that simultaneously multiplex both signal outputs and superconducting transition-edge sensor (TES) detector bias voltages. It eliminates the shunt resistor used to voltage bias TES detectors, greatly reduces power dissipation, allows different dc bias voltages for each TES, and makes all elements sufficiently compact to fit inside the detector pixel area. These in-focal plane code-division multiplexers can be combined with multi-GHz readout based on superconducting microresonators to scale to even larger arrays. [ABSTRACT FROM AUTHOR]

A transition-edge-sensor (TES) microcalorimeter's shunt resistor ( R) and thermal conductance to the cryogenic bath ( G) are often considered to be interchangeable knobs with which to control detector speed. Indeed, for otherwise-identical TES-parameter models, there are many combinations of R and G that give the same decay time-constant ( τ). However, our previous work showed that with time- or code-division-multiplexed readout, the distribution of signal-to-noise ratio with frequency, which depends strongly on R and G, is just as important as τ. Here, we present a set of calculations to select the optimal values of R and G, given a linear TES model and count-rate and energy-resolution requirements. Lower G and lower R make multiplexing easier. Our calculations also determine the allowed combination of SQUID-readout noise ( S) and multiplexer row-period ( t) and row-count ( N). Recent improvements to S and t in the NIST time-division-multiplexing architecture have allowed a NIST eight-pixel TES array to be read out with 2.70 eV (full-width at half-maximum) average energy resolution at 6 keV. The improvements make the X-ray Microcalorimeter Spectrometer co-proposed by NASA and NIST for ESA's Athena X-ray observatory straightforwardly achievable, including engineering margin, with N=16. [ABSTRACT FROM AUTHOR]

Time-division SQUID multiplexers are used in many applications that require exquisite control of systematic error. One potential source of systematic error is the pickup of external magnetic fields in the multiplexer. We present measurements of the field sensitivity figure of merit, effective area, for both the first stage and second stage SQUID amplifiers in three NIST SQUID multiplexer designs. These designs include a new variety with improved gradiometry that significantly reduces the effective area of both the first and second stage SQUID amplifiers. [ABSTRACT FROM AUTHOR]

We demonstrate the code-division multiplexing (CDM) readout of eight transition-edge sensor microcalorimeters. The energy resolution is 3.0 eV (full width at half-maximum) or better at 5.9 keV, with a best resolution of 2.3 eV and a mean of 2.6 eV over the seven modulated detectors. The flux-summing CDM system is described and compared with similar time-division multiplexing (TDM) readout. We show that the [formula] multiplexing disadvantage associated with TDM is not present in CDM. This demonstration establishes CDM as both a simple route to higher performance in existing TDM microcalorimetric experiments and a long-term approach to reaching higher multiplexing factors. [ABSTRACT FROM AUTHOR]

Multiplexed superconducting quantum interference device (SQUID) readout systems are critical for measuring large arrays of superconducting transition-edge sensors (TES). We demonstrate a code-division SQUID multiplexing (CDM) architecture that is modulated by Walsh codes. Measurements and simulations of a prototype multiplexer show that this modulation scheme is not degraded by SQUID-noise aliasing, suppresses parasitic pickup, and has low levels of crosstalk. These properties enable this architecture to scale to large TES arrays. Furthermore, CDM modulation suppresses the 1/f knee in the noise to below 20 mHz, suggesting the use of this circuit for low-frequency-noise mitigation in more general SQUID applications. [ABSTRACT FROM AUTHOR]

We present experimental results from a four-pixel array of transition-edge-sensor, x-ray microcalorimeters read out through a single amplifier channel via a time-division superconducting quantum interference device multiplexer. We map the dependence of the x-ray energy resolution of the microcalorimeters on multiplexer timing parameters. We achieve multiplexed, four-pixel resolution of 6.94±0.05 eV full width at half maximum of the Mn Kα complex near 5.9 keV, which is a degradation of only 0.44 eV from nonmultiplexed operation. An analysis of straightforward upgrades to the multiplexer predicts that a linear array of 32 of these pixels could he multiplexed with a degradation in resolution of only 0.1 eV. These results, the first demonstration of a time-division multiplexer for x-ray detectors, establish a clear path to the instrumentation of a kilopixel microcalorimeter array. [ABSTRACT FROM AUTHOR]