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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. [ABSTRACT FROM AUTHOR]

A novel triggering function developed for 240-pixel Transition-Edge Sensors is demonstrated under the high rate of particle background. The function is integrated into the standard data acquisition system in the NIST TES framework. It enables any type of combination of trigger pattern when a pixel is triggered, which is called "group trigger." As a practical implementation, the primary trigger is distributed to the four physically nearest pixels. The group trigger function was utilized throughout the entire one-month J-PARC experiment for the measurement of the Kaonic-atom X-rays. This trigger allowed us to confirm that the increased background and degraded energy resolution we observed when operating the TES array in the presence of an ion beam are the result of thermal crosstalk from charged particles. We show that the maximum of the average of the signals among the neighboring four pixels is useful for event selection. We use cuts based on this parameter to improve the peak-to-background level in a measured x-ray energy spectrum by a factor of ∼ 2, while keeping 95% of measured events. This flexible group triggering technique allows us to improve the signal to noise on the very faint Kaonic Helium x-ray lines we are measuring, better understand our experiment environment, and we believe this technique may prove useful in other ground and space-based TES applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To explore novel physical phenomena related to strong π−d interaction, we measured the resistivity (ρ) and magnetoresistance of the first organic ferrimagnetic π−d system, (EDT-TTFVO)2FeBr4 under high pressures up to 8 GPa, where EDT-TTFVO denotes ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide. At ambient pressure, ρ(T) exhibits resistivity minimum near Tmin ~ 170 K followed by a gradual increase below it. With increasing pressure, Tmin abruptly decreases till 4 GPa, beyond which it slightly increases. The increase of Tmin above 4 GPa is discussed in terms of the enhancement of the π−d interaction by applying pressure. [ABSTRACT FROM AUTHOR]

To explore novel physical phenomena related to strong π-d interaction, we measured the resistivity (ρ) and magnetoresistance of the first organic ferrimagnetic π-d system, (EDT-TTFVO)2FeBr4 under high pressures up to 8 GPa, where EDT-TTFVO denotes ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide. At ambient pressure, ρ(T) exhibits resistivity minimum near Tmin ∼ 170 K followed by a gradual increase below it. With increasing pressure, Tmin abruptly decreases till 4 GPa, beyond which it slightly increases. The increase of T min above 4 GPa is discussed in terms of the enhancement of the π-d interaction by applying pressure. [ABSTRACT FROM AUTHOR]

The magnetoresistance (MR) for a new organic conductor, β″-(EDO-TTFVO)2FeCl4 which exhibits metallic temperature dependence of the resistivity down to 0.3 K, was studied. Remarkable and unusual features were found: isotropic MR below 3 T, dip anomaly below 3 K, and SdH effect above 17 T. These features are discussed in terms of an interaction between the π-electrons on the EDO-TTFVO donors and the d-spins on the magnetic FeClions. [ABSTRACT FROM AUTHOR]

The 1:1 FeBr salt of a newly synthesized donor, ethylenedioxytetrathiafulvalenothioquinone-1,3-dithiolemethide (EDO-TTFVS) was prepared by an electrochemical oxidation. A crystal structure analysis and investigations on conducting/magnetic properties cleared that this (EDO-TTFVS)·FeBr4 salt is a new antiferromagnetic semiconductor with a high Néel temperature of 15 K. [ABSTRACT FROM AUTHOR]

The 1:1 FeBr4 − salt of a newly synthesized donor, ethylenedioxytetrathiafulvalenothioquinone-1,3-dithiolemethide (EDO-TTFVS) was prepared by an electrochemical oxidation. A crystal structure analysis and investigations on conducting/magnetic properties cleared that this (EDO-TTFVS)·FeBr4 salt is a new antiferromagnetic semiconductor with a high Néel temperature of 15 K. [ABSTRACT FROM AUTHOR]