High-energy-resolution X-ray spectroscopy using X-ray microcalorimeters has been widely adopted for high-precision experiments on fundamental science. The technical difficulties come from its use at ...low temperatures and its high sensitivity to the external environment, though many countermeasures have been proposed through the experience of space applications. The limit of the number of pixels of the semiconductor-type X-ray microcalorimeters can be solved by using the transition-edge sensor (TES) superconducting detector. Recently, a study of the strong nuclear force via high-energy-resolution X-ray spectroscopy of kaonic atoms using TES at the J-PARC accelerator facility was successfully performed by the HEATES collaboration. Furthermore, muonic-atom spectroscopy using TES has been demonstrated at the J-PARC muon facility, and a physical experiment to test the electromagnetic force under a strong electric field is ready for commissioning. Material diagnostics at a hard X-ray synchrotron facility have been tested at SPring-8 and resulted in a successful operation for the first time. Other than X-rays, TES has been used as a mass spectrometer for neutral molecules in a cryogenic electrostatic ion ring. The entire design of the experiment is carefully considered to meet the science-specific requirement. We will summarize the latest and future applications of the microcalorimeter and present key technologies, such as digital electronics, data acquisition software, aperture, collimator, mechanical, and electrical interface. Our results will be helpful for other users to design new experiments for fundamental science.
Optimal filtering is the crucial technique for the data analysis of transition-edge-sensor (TES) calorimeters to achieve their state-of-the-art energy resolutions. Filtering out the ‘bad’ data from ...the dataset is important because it otherwise leads to the degradation of energy resolutions, while it is not a trivial task. We propose a neural network-based technique for the automatic goodness tagging of TES pulses, which is fast and automatic and does not require bad data for training.
The K¯N system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series X-rays of kaonic hydrogen ...atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As X-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ϵ1s=−283±36(stat)±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy K¯N interaction.
Time-division multiplexing (TDM) is a mature scheme for the readout of arrays of transition-edge sensors (TESs). TDM is based on superconducting-quantum-interference-device (SQUID) current ...amplifiers. Multiple spectrometers based on gamma-ray and X-ray microcalorimeters have been operated with TDM readout, each at the scale of 200 sensors per spectrometer, as have several astronomical cameras with thousands of sub-mm or microwave bolometers. Here we present the details of two different versions of our TDM system designed to read out X-ray TESs. The first has been field-deployed in two 160-sensor (8 columns
×
20 rows) spectrometers and four 240-sensor (8 columns
×
30 rows) spectrometers. It has a three-SQUID-stage architecture, switches rows every 320 ns, and has total readout noise of 0.41
μ
Φ
0
/
√
Hz. The second, which is presently under development, has a two-SQUID-stage architecture, switches rows every 160 ns, and has total readout noise of 0.19
μ
Φ
0
/
√
Hz. Both quoted noise values are non-multiplexed and referred to the first-stage SQUID. In a demonstration of this new architecture, a multiplexed 1-column
×
32-row array of NIST TESs achieved average energy resolution of
2.55
±
0.01
eV at 6 keV.
We have measured the 3d→2p transition x rays of kaonic ^{3}He and ^{4}He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We ...determined the energies to be 6224.5±0.4(stat)±0.2(syst) eV and 6463.7±0.3(stat)±0.1(syst) eV, and widths to be 2.5±1.0(stat)±0.4(syst) eV and 1.0±0.6(stat)±0.3(stat) eV, for kaonic ^{3}He and ^{4}He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.
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To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high precision x-ray spectroscopy of the 5g-4f and 5f- 4d transitions (BSQED contribution of 2.4 and ...5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the 5g_{9/2}- 4f_{7/2} transition energy to be 6297.08±0.04(stat)±0.13(syst) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.
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Exotic atom experiments place transition-edge sensor (TES) microcalorimeter arrays in a high-energy charged particle-rich environment. When a high-energy charged particle passes through the silicon ...substrate of a TES array, a large amount of energy is deposited and small pulses are generated across multiple pixels in the TES array due to thermal crosstalk. We have developed analysis techniques to assess and reduce the effects of charged particle events on exotic atom X-ray measurements. Using this technique, the high-energy and low-energy components of the X-ray peaks due to pileup are eliminated, improving the energy resolution from 6.6 to 5.7 eV at 6.9 keV.
A useful function, called group trigger, is implemented in a data acquisition system of a 240-pixel X-ray transition-edge sensor array to store simultaneous waveforms from any desired set of pixels. ...It works as a diagnostic tool which can record both primary pulses and associated crosstalk events with enough freedom to optimize the data output. Under a high rate of charged particle background, such as in an accelerator, investigating signals from any combination of trigger patterns for a particular event is of high importance. We utilized this function throughout an entire experiment at J-PARC, measuring kaonic atom X-rays in 2018. This was the first time a group trigger was applied to exotic-atom spectroscopy. In this experiment, the primary trigger was distributed to the four physical nearest neighbor pixels for practical purposes. The function clarified the effect of thermal and electrical cross talk from X-rays and charged particles, resulting in a better understanding of the behavior of the TES array in such a high-background environment.
We integrated a TES X-ray spectrometer with a charged kaon beam line at J-PARC to perform X-ray spectroscopy of kaonic helium atoms. Limited beam intensity and a broad beam spot size made it crucial ...to increase the detector acceptance angle as much as possible, requiring significant development. To this end, our TES system shared the same vacuum with a cryogenic system of the liquid helium experimental target. We also specially developed a target cell for liquid helium and a thinned aperture array on top of the TES detector. Additionally, thermal and magnetic shields and infrared filters were optimized in terms of a larger acceptance angle and energy resolution of the detector. The scientific campaign was performed in June, 2018, where the whole system was stably operated for almost one month.
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