The flight of the Micro-X sounding rocket on July 22, 2018, marked the first operation of transition-edge sensors and their superconducting quantum interference device readouts in space. The instrument combines the microcalorimeter array with an imaging mirror to take high-resolution spectra from extended X-ray sources. The first flight target was the Cassiopeia A supernova remnant. Although a rocket pointing malfunction led to no time on-target, data from the flight were used to evaluate the performance of the instrument and demonstrate the flight viability of the payload. The instrument successfully achieved a stable cryogenic environment, executed all flight operations, and observed X-rays from the on-board calibration source. The flight environment did not significantly affect the performance of the detectors compared with ground operation. The flight provided an invaluable test of the impact of external magnetic fields and the instrument configuration on detector performance. This flight provides a milestone in the flight readiness of these detector and readout technologies, both of which have been selected for future X-ray observatories.

The Micro-X High Resolution Microcalorimeter X-Ray Imaging Rocket is a sounding rocket mission that will observe Supernova Remnants and search for keV-scale sterile neutrino dark matter. Micro-X will combine the excellent energy resolution of Transition Edge Sensor microcalorimeters with the imaging capabilities of a conical imaging mirror to map extended and point X-ray sources with an unprecedented combination of energy and spatial resolution. The payload has been designed to operate in the challenging conditions of a sounding rocket flight and to achieve sensitive results, in a single five-minute exposure, for each of these science goals. Micro-X’s unique design considerations are presented here, along with the status of the instrument and projections for the upcoming flights. The first Micro-X flight in 2018 will observe the Puppis A supernova remnant, where it will attain nearly 13,000 counts in the 300 s exposure. The second Micro-X flight will observe the Galactic Center to search for keV-scale dark matter and explore the nature of the unexplained 3.5 keV line observed by X-ray satellites.

With its first flight in 2018, Micro-X became the first program to fly Transition-Edge Sensors and their SQUID readouts in space. The science goal was a high-resolution, spatially resolved X-ray spectrum of the Cassiopeia A Supernova Remnant. While a rocket pointing error led to no time on target, the data was used to demonstrate the flight performance of the instrument. The detectors observed X-rays from the on-board calibration source, but a susceptibility to external magnetic fields limited their livetime. Accounting for this, no change was observed in detector response between ground operation and flight operation. This paper provides an overview of the first flight performance and focuses on the upgrades made in preparation for reflight. The largest changes have been upgrading the SQUIDs to mitigate magnetic susceptibility, synchronizing the clocks on the digital electronics to minimize beat frequencies, and replacing the mounts between the cryostat and the rocket skin to improve mechanical integrity. As the first flight performance was consistent with performance on the ground, reaching the instrument goals in the laboratory is considered a strong predictor of future flight performance.

The Micro-X sounding rocket flew for the first time on July 22, 2018, becoming the first program to fly Transition-Edge Sensors and multiplexing SQUID readout electronics in space. While a rocket pointing failure led to no time on-target, the success of the flight systems was demonstrated. The successful flight operation of the instrument puts the program in a position to modify the payload for indirect galactic dark matter searches. The payload modifications are motivated by the science requirements of this observation. Micro-X can achieve world-leading sensitivity in the keV regime with a single flight. Dark matter sensitivity projections have been updated to include recent observations and the expected sensitivity of Micro-X to these observed fluxes. If a signal is seen (as seen in the X-ray satellites), Micro-X can differentiate an atomic line from a dark matter signature.

Micro-X is a sounding rocket-borne instrument that uses a microcalorimeter array to perform high-resolution X-ray spectroscopy. This instrument flew for the first time on July 22nd, 2018, from the White Sands Missile Range, USA. This flight marks the first successful operation of a transition-edge sensor array and its time-division multiplexing readout system in space. This launch was dedicated to the observation of the supernova remnant Cassiopeia A. A failure in the attitude control system prevented the rocket from pointing and led to no time on target. The onboard calibration source provided X-rays in flight, and it is used to compare detector performance during preflight integration, flight, and after the successful post-flight recovery. This calibration data demonstrate the capabilities of the detector in a space environment as well as its potential for future flights.

Micro-X is a sounding rocket-borne X-ray telescope that uses a transition edge sensor microcalorimeter array to provide high-energy-resolution spectroscopy. Micro-X is a versatile instrument with plans to observe the Puppis A supernova remnant during its first flight, as well as future observations of the Milky Way to search for X-ray signals from decaying dark matter. Commissioning and functionality testing are complete, and the thermal performance of the system has been validated. We are currently evaluating the detector performance in the flight cryostat with the flight multiplexing electronics. Operating in this setup has allowed us to characterize sources of detector and readout noise, as well as to implement mitigation techniques to improve performance in anticipation of the upcoming flight. We present an overview of important noise considerations in addition to an update on latest detector performance.

Micro-X is a sounding rocket borne X-ray telescope that utilizes transition edge sensors to perform imaging spectroscopy with a high level of energy resolution. Its 2.1m focal length X-ray optic has an effective area of 300 cm(2), a field of view of 11.8 arcmin, and a bandpass of 0.1-2.5 keV. The detector array has 128 pixels and an intrinsic energy resolution of 4.5 eV FWHM. The integration of the system has progressed with functional tests of the detectors and electronics complete, and performance characterization of the detectors is underway. We present an update of ongoing progress in preparation for the upcoming launch of the instrument.

Micro-X is a NASA-funded sounding rocket-borne X-ray imaging spectrometer designed to enable high precision measurements of extended astrophysical systems. To perform high energy resolution measurements and capture unprecedented spectra of supernova remnants and galaxy clusters, Micro-X must maintain tight temperature control. One of the biggest challenges in payload design is to prevent heating of the detectors due to the vibrational loads on the rocket skin during launch. Several stages of vibration damping systems are implemented to prevent energy transmission from the rocket skin to the detector stage, each stage more rigid than the last. We describe recent redesign efforts to improve this vibration isolation by tuning the resonant frequencies of the various stages to minimize heating prior to the projected launch in 2016.

Micro-X is a NASA-funded, sounding rocket-borne X-ray imaging spectrometer that will allow high precision measurements of velocity structure, ionization state and elemental composition of extended astrophysical systems. One of the biggest challenges in payload design is to maintain the temperature of the detectors during launch. There are several vibration damping stages to prevent energy transmission from the rocket skin to the detector stage, which causes heating during launch. Each stage should be more rigid than the outer stages to achieve vibrational isolation. We describe a major design effort to tune the resonance frequencies of these vibration isolation stages to reduce heating problems prior to the projected launch in the summer of 2014.

The magnetocaloric effect is the thermal response of a material to an external magnetic field. This manuscript focuses on the physics and the properties of materials which are commonly used for magnetic refrigeration at cryogenic temperatures. After a brief overview of the magnetocaloric effect and associated thermodynamics, typical requirements on refrigerants are discussed from a standpoint of cooling power density optimization. Finally, a compilation of the most important properties of several common magnetocaloric materials is presented. (C) 2014 Elsevier Ltd. All rights reserved.

Results are presented from a reanalysis of the entire five-tower data set acquired with the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory, with an exposure of 969 kg-days. The analysis window was extended to a recoil energy of 150 keV, and an improved surface-event background-rejection cut was defined to increase the sensitivity of the experiment to the inelastic dark matter (iDM) model. Three dark matter candidates were found between 25 keV and 150 keV. The probability to observe three or more background events in this energy range is 11%. Because of the occurrence of these events, the constraints on the iDM parameter space are slightly less stringent than those from our previous analysis, which used an energy window of 10-100 keV.

We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ∼10  GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9  GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.

Adiabatic Demagnetization Refrigerators (ADRs) are commonly used in cryogenic laboratories to achieve subkelvin temperatures. ADRs are also the technology of choice for several space borne instruments which make use of cryogenic microcalorimeters or bolometers [1-4]. For these applications, refrigerants with high ratios of cooling capacity to volume, or cooling capacity to mass are usually required. In this manuscript, two charts for the simple selection of the most suitable of several common refrigerants (CAA, CMN, CPA, DGG, FAA, GGG, GLF and MAS) are presented. These graphs are valid for single stage cycles. The selection of the refrigerants is uniquely dependent on the starting conditions of the refrigeration cycle (temperature and magnetic field density) and the desired final temperature. Only thermodynamic properties of the refrigerants have been taken into account, and other important factors such as availability and manufacturability have not been considered. (C) 2011 Elsevier Ltd. All rights reserved.

The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents 614 kg.d equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spin-independent WIMP-nucleon cross-section. For a WIMP mass of 90 GeV/c^2, where this analysis is most sensitive, a cross-section of 3.3 x 10^{-44} cm^2 is excluded at 90% CL. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above 700 GeV/c^2. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others.

Ti 15V–3Cr–3Sn–3Al, sometimes referred to as Ti 15-3-3-3 or “Magic Titanium”, is a candidate material for components requiring high mechanical strength and low thermal conductivity at cryogenic temperatures. The electrical resistance of Ti 15-3-3-3 was measured between 230mK and room temperature, and the thermal conductivity between 230mK and 7.7K. A superconducting transition was observed at TC=3.89±0.01K. Below the superconducting transition temperature, the thermal conductivity was fitted to a function of the form λ(TTC)=γ·Tδ, where γ=α·TC1-δ·e-β and δ=0.4±0.05. The thermal conductivity of Ti 15-3-3-3 is compared with other materials commonly used for the construction of thermally isolating support structures. Ti 15-3-3-3 is shown to exhibit one of the lowest ratios of thermal conductivity to mechanical strength and is thus particularly well suited for such applications.

The Micro‐X Imaging X‐ray Spectrometer is a sounding rocket payload slated for launch in 2011. An array of Transition Edge Sensors, which is operated at a bath temperature of 50 mK, will be used to obtain a high resolution spectrum of the Puppis‐A supernova remnant. An Adiabatic Demagnetization Refrigerator (ADR) with a 75 gram Ferric Ammonium Alum (FAA) salt pill in the bore of a 4 T superconducting magnet provides a stable heat sink for the detector array only a few seconds after burnout of the rocket motors. This requires a cold stage design with very short thermal time constants. A suspension made from Kevlar strings holds the 255 gram cold stage in place. It is capable of withstanding loads in excess of 200 g. Stable operation of the TES array in proximity to the ADR magnet is ensured by a three‐stage magnetic shielding system which consists of a superconducting can, a high‐permeability shield and a bucking coil. The development and testing of the Micro‐X payload is well underway.

We report on the analysis of the low-energy electron-recoil spectrum from the CDMS II experiment using data with an exposure of 443.2 kg-days. The analysis provides details on the observed counting rate and possible background sources in the energy range of 2–8.5 keV. We find no significant excess of a peaked contribution to the total counting rate above the background model, and compare this observation to the recent DAMA results. In the framework of a conversion of a dark matter particle into electromagnetic energy, our 90% confidence level upper limit of 0.246  events/kg/day at 3.15 keV is lower than the total rate above background observed by DAMA. In absence of any specific particle physics model to provide the scaling in cross section between NaI and Ge, we assume a Z2 scaling. With this assumption the observed rate in DAMA remains higher than the upper limit in CDMS. Under the conservative assumption that the modulation amplitude is 6% of the total rate we obtain upper limits on the modulation amplitude a factor of ~2 lower than observed by DAMA, constraining some possible interpretations of this modulation.

Micro-X is a rocket-borne X-ray telescope which will use an array of Transition Edge Sensor (TES) microcalorimeters to obtain high resolution soft X-ray spectra of extended astronomical sources. The microcalorimeter array consists of 128 pixels with a size of 590 mu m x 590 mu m each. The TESs are read out with a time-division Superconducting Quantum Interference Device (SQUID) multiplexing system. The instrument's front end assembly, which contains the microcalorimeter array and two SQUID amplification stages, is located at the focal point of a conically approximated Wolter mirror with a focal length of 2100 mm and a point spread function of 2.4 arcmin half-power diameter. The telescope's effective area amounts to similar to 300 cm(2) at 1 keV. The TES array is cooled with an Adiabatic Demagnetization Refrigerator. The first flight of Micro-X is scheduled for 2011, and will likely target a Si knot in the Puppis A supernova remnant. The time available for the observation above an altitude of 160 km will be in excess of 300 seconds. The design, manufacturing and assembly of the flight hardware has recently been completed, and system testing is underway. We describe the final design of the Micro-X instrument, and report on the overall status of the project.

SuperCDMS employs 1-inch thick germanium crystals operated below 50mK in a dilution cryostat. Each detector produces ionization and phonon signals. Ionization signals are amplified by JFETs operating at 150K within an assembly mounted on the 4K cryostat stage. These high impedance signals are carried to the FETs by superconducting "vacuum coaxes" which minimize thermal conductivity, stray capacitance, and microphonics. Transition edge sensors produce low-impedance phonon signals, amplified by SQUID arrays mounted on a 600mK stage. Detectors are mounted in a six-sided wiring configuration called a "tower", which carries signals from 40mK to 4K. A flex circuit 3 meters in length carries amplified signals for each detector from 4K to a vacuum bulkhead. We describe the methods used to support the detectors, wiring and amplifier elements at various thermal stages, minimizing electrical noise and thermal loads.