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Hot Universe Baryon Surveyor (HUBS)1 is being conceptualized in China as a high throughput and highresolution spectroscopic X-ray mission dedicated to studying cosmic “missing” baryons, which are thought to exist in the gas of very low density and temperature of roughly one million degrees in the halo of galaxies or in large-scale structures. To detect weak emission from the “missing” baryons, HUBS will employ an X-ray microcalorimeter based on transition-edge sensors (TES) array that operates at very low temperatures. The key characteristics of the detector technology are excellent energy resolution and high quantum efficiency, which makes it an ideal choice for constructing a non-dispersive X-ray imaging spectrometer. We are developing X-ray microcalorimeters for HUBS, based on superconducting Mo/Cu bilayer films. In this work, we present results on characterization of the Mo/Cu films and TES devices at temperatures below 200 mK, including their I − V characteristics, pulse signals and energy resolutions. We have also studied correlations between the superconductivity and other properties of the films (including residual resistivity ratio, stress, crystalline structure, interface properties, etc.). Preliminary results are presented in this work.

Hot Universe Baryon Surveyor (HUBS), a Chinese space mission, is proposed to find a large fraction of the so-called missing baryons, which would help us to understand more about the structure formation and evolution of the universe. Both theoretical and experimental results show that developing a highly efficient soft X-ray spectrometer over a large field of view and with a high energy resolution is the key to detect the “missing baryons”. X-ray microcalorimeters based on a transition-edge sensor (TES) array is required for HUBS, which aims to have 1 deg2 field of view (FoV) with 1’ angular resolution and 2 eV energy resolution optimized around 0.6 keV. Taking the high throughput X-ray optical focusing system on HUBS into account, the TES array is designed to have 60 x 60 pixels with an area of 1 mm2 for each pixel. The microcalorimeter consists of a TES, a weak thermal link to a heat bath, and a semi-metal or normal metal absorber to increase the X-ray absorption efficiency. When an X-ray photon with a given energy is absorbed, the temperature of the absorber increase, that can be monitored by measuring the resistance change of the TES. A bilayer of a superconductor and a normal metal is used to fabricate a TES with a critical temperature (Tc) of ~100 mK. The latter is set for the required energy resolution. For HUBS, both MoCu and TiAu TES technologies are considered in its development phase. Here we will focus on TiAu TES calorimeters designed and partially fabricated at SRON for HUBS. Recent demonstration of a resolution of 2.5 eV at 5.9 keV in an AC readout at SRON for X-IFU on board of Athena illustrates the promising of this technology. However, the challenging for the HUBS array is the large pixel size. We will report the design and fabrication of prototype HUBS calorimeters.

Superconducting Transition Edge Sensor (TES) bolometer arrays with thousands of pixels are essential for achieving the science objectives of future cold far-infrared astronomical telescopes. The readout of such large format TES arrays represents a significant challenge for these missions in terms of power consumption and thermal loading on the coldest cryogenic stages of the instruments. The Time Domain Multiplexing (TDM) technology is mature and has been implemented on many ground-based and air-borne instruments using TES arrays. Several concept studies such as Origins Space Telescope (OST [4]) or Mid-InfraRed Exo-planet CLimate Explorer (MIRECLE [5]) consider this technology and Time Domain Multiplexing as one of the possible baseline technologies for their instruments. In order to address the aforementioned challenges we propose a novel modular solution called Modular Adaptive Transition Edge Sensor Superconducting quantum interference device Electronics (MATESSE) that will serve as the necessary step towards an adaptation of the solution to a space-proven system.

The high-resolution X-ray imaging spectrometer of the Hot Universe Baryon Surveyor (HUBS) mission is based on the superconducting transition edge sensor (TES) technology. A TES serves as a thermometer for sensing the temperature change of a microcalorimeter to measure the energy of incident X-rays. In order to achieve high sensitivity, TES needs to operate at temperatures below 100 mK. A combination of a 4 K pre-cooling system and a sub-K cooling system is required to achieve such a low temperature. In this paper, it is proposed to directly obtain the 4 K temperature by a high frequency pulse tube cryocooler (HPTC) for HUBS. The advantages of this technology is compact structure and high reliability, compared with other technologies (for instance, multi-stage Stirling cryocoolers + Joule-Thompson cooler). We have constructed a multi-stage HPTC. The test cooling performance, as well as the design of the cryocooler, existing challenges and proposed solutions will be presented.

In this work, the interface composition of the superconducting Ti/PdAu bilayer is tuned by an annealing process in N2 from 100 to 500 &deg, C to control the superconducting transition temperature (Tc). This Ti-PdAu composition layer is characterized with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) to show the infiltration process. The surface topography, electrical, and cryogenic properties are also shown. The inter-infiltration of Ti and PdAu induced by the thermal treatments generates an intermixed layer at the interface of the bilayer film. Due to the enforced proximity effect by the annealing process, the Tc of Ti (55 nm)/PdAu (60 nm) bilayer thin films is tuned from an initial value of 243 to 111 mK which is a temperature that is suitable for the application as the function unit of a superconducting transition edge sensor.

The far infrared instrument SAFARI spectrometer on board the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) provides moderate resolution spectra (R~300) with simultaneous coverage over 34 to 230 μm. With the high sensitivity TES detectors, the SAFARI can reach the sensitivity down to ~7×10-20 W/m2. In order to provide accurate calibration for the TES readout circuit, a calibration source assembly (CSA) is developed to provide a stable and absolute flux radiation to the spectrometer over the whole spectral range. The CSA has a primary function during observations to take periodic reference measurement to correct for drift, subtracting backgrounds, etc from the detector. The CSA is composed of three microlamps and one integrating sphere. The microlamps are made of resistance wires by microlithography to mimic square blackbody sources. By combining an 81K microlamp and a 24K microlamp, a reasonably flat spectrum can be produced at the output of the integrating sphere. The radiation to the transition edge sensor detector pixel is around 1×10-16 W. The integrating sphere can also provide a uniform output to cover the size of SAFARI field of view including the target and sky pixels. In this paper, the CSA design and the prototype results of the microlamp and the integrating sphere are presented.

A dark photon, one of the candidates of light dark matter, will be searched around 0.1 meV range by using a gyrotron. The use of a Transition Edge Sensor is the key of this experiment and the expected result is promising. This search will pave a way to future axion search using similar instruments., Comment: accepted by the 45th International Conference on Infrared, Millimeter, and Terahertz Waves

We present numerical simulations of full transition-edge sensor (TES) arrays utilizing graphical processing units (GPUs). With the support of GPUs, it is possible to perform simulations of large pixel arrays to assist detector development. Comparisons with TES small-signal and noise theory confirm the representativity of the simulated data. In order to demonstrate the capabilities of this approach, we present its implementation in , a simulator for the X-ray Integral Field Unit, a cryogenic X-ray spectrometer on board the future Athena X-ray observatory.

We report on the design, commissioning, and initial measurements of a Transition-edge Sensor (TES) x-ray spectrometer for the Electron Beam Ion Trap (EBIT) at the National Institute of Standards and Technology (NIST). Over the past few decades, the NIST EBIT has produced numerous studies of highly charged ions in diverse fields such as atomic physics, plasma spectroscopy, and laboratory astrophysics. The newly commissioned NIST EBIT TES Spectrometer (NETS) improves the measurement capabilities of the EBIT through a combination of high x-ray collection efficiency and resolving power. NETS utilizes 192 individual TES x-ray microcalorimeters (166/192 yield) to improve upon the collection area by a factor of ~30 over the 4-pixel neutron transmutation doped germanium-based microcalorimeter spectrometer previously used at the NIST EBIT. The NETS microcalorimeters are optimized for the x-ray energies from roughly 500 eV to 8,000 eV and achieve an energy resolution of 3.7 eV to 5.0 eV over this range, a more modest (

The Atacama Submillimeter Telescope Experiment (ASTE), a 10-m aperture telescope, hosts a camera equipped with the Transition Edge Sensor (TES). We developed a fore-optics module—“APol,” to convert the 271 pixels of the TES working at 350 GHz into a sensitive imaging polarimeter without sacrificing the image quality and the 7.5 ′ field of view. Here, we describe the detailed optical design of APol and present the results of the preliminary test in a laboratory.

Resonant soft x-ray scattering (RSXS) is a leading probe of valence-band order in materials best known for detecting charge-density-wave order in copper-oxide superconductors. One of the biggest limitations on the RSXS technique is the presence of a severe fluorescence background, which, like the RSXS cross section itself, is enhanced under resonant conditions. This background prevents the study of weak signals such as diffuse scattering from glassy or fluctuating order that is spread widely over momentum space. Recent advances in superconducting transition-edge-sensor (TES) detectors have led to major improvements in energy resolution and detection efficiency in the soft x-ray range. Here, we perform a RSXS study of stripe-ordered ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ba}}_{x}{\mathrm{Cu}\mathrm{O}}_{4}$ at the $\mathrm{Cu}$ ${L}_{3/2}$ edge (932.2 eV) using a TES detector with 1.5-eV resolution, to evaluate its utility for mitigating the fluorescence-background problem. We find that, for suitable degree of detuning from the resonance, the TES rejects the fluorescence background, leading to a five to ten times improvement in the statistical quality of the data compared to an equivalent, energy-integrated measurement. We conclude that a TES presents a promising approach to reducing background in RSXS studies and may lead to discoveries in materials exhibiting valence-band order that is fluctuating or glassy.

Families of cosmic inflation models predict a primordial gravitational-wave background that imprints B-mode polarization pattern in the Cosmic Microwave Background (CMB). High sensitivity instruments with wide frequency coverage and well-controlled systematic errors are needed to constrain the faint B-mode amplitude. We have developed antenna-coupled Transition Edge Sensor (TES) arrays for high-sensitivity polarized CMB observations over a wide range of millimeter-wave bands. BICEP Array, the latest phase of the BICEP/Keck experiment series, is a multi-receiver experiment designed to search for inflationary B-mode polarization to a precision $\sigma$(r) between 0.002 and 0.004 after 3 full years of observations, depending on foreground complexity and the degree of lensing removal. We describe the electromagnetic design and measured performance of BICEP Array low-frequency 40-GHz detector, their packaging in focal plane modules, and optical characterization including efficiency and beam matching between polarization pairs. We summarize the design and simulated optical performance, including an approach to improve the optical efficiency due to mismatch losses. We report the measured beam maps for a new broad-band corrugation design to minimize beam differential ellipticity between polarization pairs caused by interactions with the module housing frame, which helps minimize polarized beam mismatch that converts CMB temperature to polarization ($T \rightarrow P$) anisotropy in CMB maps., Comment: 8 pages, 7 figures, Accepted by the Journal of Low Temperature Physics (Proceedings of the 18th International Workshop on Low Temperature Detectors)

International audience; The X-ray Integral Field Unit (X-IFU) will operate an array of more than 3000 Transition Edge Sensor pixels at 90 mK with an unprecedented energy resolution of 2.5 eV at 7 keV. In space, primary cosmic rays and secondary particles produced in the instrument structure will continuously deposit energy on the detector wafer and induce fluctuations on the pixels’ thermal bath. We have investigated through simulations of the X-IFU readout chain how these fluctuations eventually influence the energy measurement of X-ray photons. Realistic timelines of thermal bath fluc-tuations at different positions in the array are generated as a function of a thermal model and the expected distribution of the deposited energy of the charged particles. These are then used to model the TES response to these thermal perturbations and their influence on the onboard energy reconstruction process. Overall, we show that with adequate heatsinking, the main energy resolution degradation effect remains minimal and within the associated resolution allocation of 0.2 eV. We further study how a dedicated triggering algorithm could be put in place to flag the rarer large thermal events

The HOLMES project aims to directly measure the electron neutrino mass using the electron capture decay (EC) of 163Ho down to the eV scale. It will perform a precise measurement of the end-point of the 163Ho calorimetric energy spectrum to search for the deformation caused by a finite electron neutrino mass. The choice of 163Ho as source is driven by the very low Q-value of the EC reaction (around 2.8 keV), which allows for a high sensitivity while keeping the overall activities to reasonable value (O(102)Hz/detector), thus reducing the pile-up probability. A large array made of thousands of Transition Edge Sensor based micro-calorimeters will be used for a calorimetric measurement of the EC 163Ho spectrum. The calorimetric approach, with the source embedded inside the detector, eliminates systematic uncertainties arising from the use of an external beta-source, and minimizes the effect of the atomic de-excitation process uncertainties. The commissioning of the first implanted sub-array is scheduled for the end of 2017. It will provide useful data about the EC decay of 163Ho together with a first limit on neutrino mass. In this paper the current status of the main tasks will be summarized: the TES array design and engineering, the isotope preparation and embedding, and the development of a high speed multiplexed SQUID read-out system for the data acquisition.

COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) is an experiment employing cryogenic calorimeters, dedicated to direct dark matter search in underground laboratories. Its goal is to cross-check the annual modulation signal the DAMA collaboration has been detecting for about 20 years (Bernabei et al. in Nucl Part Phys Proc 303–305:74–79, 2018. 10.1016/j.nuclphysbps.2019.03.015) and which has been ruled out by other experiments in certain dark matter scenarios. COSINUS can provide a model-independent test by the use of the same target material (NaI), with the additional chance of discriminating $$\beta /\gamma$$ β / γ events from nuclear recoils on an event-by-event basis, by the application of a well-established temperature sensor technology developed within the CRESST collaboration. Each module is constituted by two detectors: the light detector, that is a silicon beaker equipped with a transition edge sensor (TES), and the phonon detector, a small cubic NaI crystal interfaced with a carrier of a harder material (e.g. $$\hbox {CdWO}_4$$ CdWO 4 ), also instrumented with a TES. This technology had so far never been applied to NaI crystals because of several well-known obstacles, and COSINUS is the first experiment which succeeded in operating NaI crystals as cryogenic calorimeters. Here, we present the COSINUS project, describe the achievements and the challenges of the COSINUS prototype development and discuss the status and the perspectives of this NaI-based cryogenic frontier.

We describe the design, fabrication, integration and characterization of a prototype superconducting filter bank with transition edge sensor readout designed to explore millimetre-wave detection at frequencies in the range 40 to 65 GHz. Results indicate highly uniform filter channel placement in frequency and high overall detection efficiency. The route to a full atmospheric sounding instrument in this frequency range is discussed., 13 pages, 12 figures

At Argonne National Laboratory, we are developing hard X-ray (2 to 20 keV) Transition Edge Sensor (TES) arrays for beamline science. The significantly improved energy resolution provided by superconducting detectors compared to semiconductor-based energy-dispersive detectors, but with better collection efficiency than wavelength-dispersive instruments, will enable greatly improved X-ray emission and absorption spectroscopic measurements. A prototype instrument with 24 microwave-frequency multiplexed pixels is now in testing at the Advanced Photon Source (APS) 1-BM beamline. Initial measurements show an energy resolution ten times better (150 eV compared to < 15 eV) than the silicon-drift detectors currently available to APS beamline users, and in particular demonstrate the ability to resolve closely-spaced emission lines in samples containing multiple transition metal elements, such as integrated circuits. Comparing fluorescence spectra of integrated circuits measured with our TESs at the beamline to those measured with silicon detectors, we find emission lines and elements largely hidden (e.g. Hf alongside Cu) from a semiconductor-based detector but well resolved by a TES. This directly shows the strengths of TES-based instruments in fluorescence mapping., 5 pages, 4 figures. Presented at the 2020 Applied Superconductivity Conference, 24 Oct - 7 Nov 2020

International audience; QUBIC (a Q and U Bolometric Interferometer for Cosmology) is a next generation cosmology experiment designed to detect the B-mode polarisation of the Cosmic Microwave Background (CMB). A B-mode detection is hard evidence of Inflation in the ΛCDM model. QUBIC aims to accomplish this by combining novel technologies to achieve the sensitivity required to detect the faint B-mode signal. QUBIC uses technologies such as a rotating half-wave plate, cryogenics, interferometric horns with self-calibration switches and transition edge sensor bolometers. A Technical Demonstrator (TD) is currently being calibrated in APC in Paris before observations in Argentina in 2021. As part of the calibration campaign, the spectral response of the TD is measured to test and validate QUBIC's spectro-imaging capability. This poster gives an overview of the methods used to measure the spectral response and a comparison of the instrument data with theoretical predictions and optical simulations.

Over the past several decades, measurements of the Cosmic Microwave Background (CMB) have been a major driving force in our understanding of cosmology. Measurements of the CMB on large angular scales places tight constraints on the parameters of the Lambda-CDM cosmological model. Measurements of the CMB at smaller angular scales constrains secondary anisotropies, such as the thermal and kinetic Sunyaev Zel'dovitch (tSZ and kSZ) effects, which constrain the structure of the universe at later times. The CMB is also polarized, and the polarization signal encodes information about both the inflationary era and late-time structure formation in our universe. In the first part of this dissertation, I introduce the CMB and discuss the measurements that have been made so far and what we can learn from them.The South Pole Telescope (SPT) is a 10 meter telescope that is dedicated to measuring the CMB down to small angular scales. So far, the SPT has housed two instruments, SPT-sz and SPT-pol. SPT-sz was sensitive to temperature and completed a 2540 square degree survey of the southern sky from 2008-2011. SPT-pol is a polarization sensitive camera that was deployed in 2012, and has been conducting a polarization survey since that time. These instruments both use photon-noise limited superconducting Transition Edge Sensors (TESes) in large numbers to obtain their high sensitivities. TES design and fabrication in large format arrays was critical to the success of these instruments. The second part of this dissertation focuses on the instrumentation of the SPT. I present the theory behind TES bolometer design with a focus on detector stability and optimal performance. Finally, I discuss the design and performance of the two instruments, with a focus on the detector development for the SPT-pol instrument.In the final part of this dissertation, I use the full 2540 square degree SPT-sz survey to measure the power spectrum from 1850 < l < 11000 at 90, 150, and 220 GHz and constrain small scale CMB anisotropies. We use a multifrequency cross-spectrum analysis to fit the data using a model that includes the lensed primary CMB, secondary CMB anisotropies (tSZ and kSZ effects), and foregrounds. The foreground power consists of a poisson component from radio sources, poisson and clustered components from dusty point sources, galactic cirrus, and tSZ-CIB correlations. These data represent the most sensitive measurement of the small angular scale CMB power spectrum to date. The data constrain the amplitude of the tSZ and kSZ signals, from which we can learn about late time structure and the epoch of reionization.

A four-by-four transition-edge sensor (TES) bolometer array based on an Al/Ti bilayer on an Si3N4 substrate for thermal connection, showing an unbiased transition temperature of 1.2 K, was fabricated and characterized. Formation of the Al/Ti bilayer with tetragonal structure was confirmed by x-ray diffraction analysis. The surface roughness of 3.11 nm calculated by atomic force microscopy was found to be negligible compared with the particle size (19.66 nm), indicating a smooth surface. The smoothness of the resistance–temperature (R–T) curve corresponds to the smoothness of the surface of the bilayer sensor, and the superconducting transition curve of the suspended bilayer TES was designed with a biased Tc of 0.45 K and ΔTc = 2 mK. Such TES bolometer arrays are suitable for astrophysical observations and are extensively used in cosmic microwave background polarization detection.

The aim of this research work was to model the behaviour of a transition edge sensor (TES) bolometer by applying curve fitting methodology on empirical data. Data obtained from the experiments were used to plot characteristic curves to find resistance–temperature (R–T) and current–voltage (I–V) relations. The measurements were taken by using a cryogenic-free 3He refrigerator with a least temperature of 320 mK. Least-squares curve fitting technique was used to devise the equations of the experimentally obtained data. Similarly, the empirical data and estimated curves were validated using the parameters of R-squared, sum of squares due to error (SSE), adjusted R-squared, and root-mean-squared error (RMSE). By comparing the plot of the empirical data and estimated behaviour curves showed high degree of similarity, and hence it was established that these equations could be used to estimate the bolometer’s operating behaviour for different ambient conditions with minimal percentage error. We also studied etched (TES device suspended on SiN) and non-etched (Si substrate based device) samples of bolometers. It was concluded that bolometers made up of etched sample of TES are appropriate for use in millimetre and submillimeter waves, especially for cosmic microwave background polarization detection.

著者人数: 11名, Accepted: 2018-06-15, 資料番号: SA1180190000

We are building a transition edge sensor (TES) X-ray spectrometer for the Linac Coherent Light Source (LCLS-II) at SLAC National Accelerator Laboratory (SLAC) to coincide with new upgrades for this free electron laser facility. This new X-ray spectrometer will have 1000 TES pixels with 0.5 eV energy resolution for soft X-rays below 1 keV. Multiplexing will be done with microwave SQUID resonators and new specialized electronic hardware developed at SLAC. This spectrometer will use a dilution refrigerator to achieve lower operating temperatures than previous TES spectrometers and will be coupled to the liquid jet endstation at LCLS-II. The spectrometer is designed to operate at much higher count rates than previous TES X-ray spectrometers to take advantage of the high repetition rate of the LCLS-II. Science applications will utilize the high photon collection efficiency and throughput, high energy resolution, as well as its ability to simultaneously measure its full calibrated energy range.

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.

Several current and proposed cosmic microwave background experiments use transition edge sensor bolometer focal planes coupled to the digital frequency-domain multiplexing (DfMux) electronics. This readout architecture sums bolometer signals in a SQUID array amplifier (SAA). In this study, we investigate the properties of two SAA designs, the SA4b, which is currently used in the DfMux system, and the SA13a. The SA13a design is gradiometric, making it less sensitive to stray magnetic field pickup. It has lower input inductance and is laid out on the chip as a re-configurable array with 6 banks of 64 series SQUIDs that can be arranged in any series and parallel configurations to optimize array noise, peak-to-peak modulation depth, and dynamic output resistance. The SA13a design reported on here is configured with 3 banks in series $$\times $$ 2 banks in parallel. The SA4b is a series array of 100 SQUIDs in series, each with an 8-turn input coil.

A scanning electron microscope transition edge sensor has been developed to analyze the minor or trace constituents contained in a bulk sample and small particles on the sample under a low accelerating voltage (typically

著者人数: 11名, Accepted: 2018-07-17, 資料番号: SA1180193000

The South Pole Telescope SPT-3G camera utilizes Ti/Au transition edge sensors (TESs). A key requirement for these sensors is reproducibility and long-term stability of the superconducting (SC) transitions. Here, we discuss the impact of electrical contacts design and materials on the shape of the SC transitions. Using scanning electron microscope, atomic force microscope, and optical differential interference contrast microscopy, we observed the presence of unexpected defects of morphological nature on the titanium surface and their evolution in time in proximity to Nb contacts. We found direct correlation between the variations of the morphology and the SC transition shape. Experiments with different diffusion barriers between TES and Nb leads were performed to clarify the origin of this problem. We have demonstrated that the reproducibility of superconducting transitions can be significantly improved by preventing diffusion processes in the TES–leads contact areas.

Microwave SQUID multiplexing is a promising technique for multiplexing large arrays of transition edge sensors. A major bottleneck in the development and distribution of microwave SQUID multiplexer chips occurs in the time-intensive design testing and quality assurance stages. To obtain useful RF measurements, these devices must be cooled to temperatures below 500 mK. The need for a more efficient system to screen microwave multiplexer chips has grown as the number of chips requested by collaborators per year reaches into the hundreds. We have therefore assembled a test bed for microwave SQUID circuits, which decreases screening time for four 32-channel chips from 24 h in an adiabatic demagnetization refrigerator to approximately 5 h in a helium dip probe containing a closed cycle $${^3}$$ He sorption refrigerator. We discuss defining characteristics of these microwave circuits and the challenges of establishing an efficient testing setup for them.

We designed and fabricated a photon-number-resolving detector based on an iridium (Ir) transition-edge sensors (TES) with small timing jitter time for coherent optical communication. The current–voltage relationship of the small Ir-TES, with an effective area of 7 μm × 7 μm, was measured, and its electrothermal feedback operation was confirmed. This device had a transition temperature of 280 mK, which is higher than that of bulk Ir, because of the wide contact area.

Heavy ion cancer therapy allows the tumors to destroy while sparing surrounding, healthy tissues. By controlling the incident energy of heavy ions, the penetration depth can be adjusted precisely to the tumor area. The ionizing chambers are usually used for the determination of absorbed dose in the heavy ion irradiation fields; however, uncertainty in measurement of these detectors is expected to remain by more than 5%, and this has a negative influence on the therapeutic effect. Now we began to develop the precision heavy ion beam detector applying the superconducting transition-edge sensor (TES). Using the Ir/Au-TES coupled to a tin absorber, we have succeeded to detect the helium ions which were injected from Heavy Ion Medical Accelerator in Chiba. Although pulses are fully saturated because the temperature change is beyond the transition region, the signal length reflects the incident energy of each injected heavy ion. These results indicate the possibility of the precision heavy ion energy detection applying the TES detector.