# Evidence for metastable excimer states as the source of electron train backgrounds in liquid xenon emission detectors [CL]

Single electron backgrounds with millisecond timescales are known to follow ionizing events in liquid/gas xenon emission detectors. These backgrounds can limit the low-energy threshold of dark matter searches, and prevent discovery-class searches for MeV scale hidden sector dark matter. A systematic study reveals a fast (tau_1) and slow (tau_2) component to the background. The fast component is compatible with electrons which were trapped at the liquid surface, and can be reduced by increasing the electric field. However, the slow component increases linearly with electric field. This is consistent with electron impact excitation of higher-energy molecular excited states.

P. Sorensen and K. Kamdin
Tue, 21 Nov 17
9/79

Comments: N/A

# Adaptive inversion algorithm for 1.5 um visibility lidar incorporating in situ Angstrom wavelength exponent [CL]

As one of the most popular applications of lidar systems, the atmospheric visibility is defined to be inversely proportional to the atmospheric extinction coefficient at 0.55 um. Since the laser at 1.5 um shows the highest maximum permissible exposure in the wavelength ranging from 0.3 um to 10 um, the eye-safe 1.5 um lidar can be deployed in urban areas. In such a case, the measured extinction coefficient at 1.5 um should be converted to that at 0.55 um for visibility retrieval. Although several models have been established since 1962, the accurate wavelength conversion remains a challenge. An adaptive inversion algorithm for 1.5 um visibility lidar is proposed and demonstrated by using the in situ Angstrom wavelength exponent, which is derived from either a sun photometer or an aerosol spectrometer. The impact of the particle size distribution of atmospheric aerosols and the Rayleigh backscattering of atmospheric molecules are taken into account. In comparison, the Angstrom wavelength exponent derived from the sun photometer is 7.7% higher than that derived from the aerosol spectrometer. Then, using 1.5 um visibility lidar, the visibility with a temporal resolution of 5 min is detected over 48 hours in Hefei (31.83 N, 117.25 E). The average visibility error between the new method and a visibility sensor (Vaisala, PWD52) is 5.2% with the R-square value of 0.96, while the relative error between another reference visibility lidar at 532 nm and the visibility sensor is 6.7% with the R-square value of 0.91. All results agree with each other well, demonstrating the accuracy and stability of the algorithm.

X. Shang, H. Xia, X. Dou, et. al.
Tue, 21 Nov 17
61/79

Comments: 9 pages, 7 figures

# Cathode signal in a TPC directional detector: implementation and validation measuring the drift velocity [IMA]

Low-pressure gaseous TPCs are well suited detectors to correlate the directions of nuclear recoils to the galactic Dark Matter (DM) halo. Indeed, in addition to providing a measure of the energy deposition due to the elastic scattering of a DM particle on a nucleus in the target gas, they allow for the reconstruction of the track of the recoiling nucleus. In order to exclude the background events originating from radioactive decays on the surfaces of the detector materials within the drift volume, efforts are ongoing to precisely localize the track nuclear recoil in the drift volume along the axis perpendicular to the cathode plane. We report here the implementation of the measure of the signal induced on the cathode by the motion of the primary electrons toward the anode in a MIMAC chamber. As a validation, we performed an independent measurement of the drift velocity of the electrons in the considered gas mixture, correlating in time the cathode signal with the measure of the arrival times of the electrons on the anode.

C. Couturier, Q. Riffard, N. Sauzet, et. al.
Tue, 21 Nov 17
64/79

Comments: 8 pages, 3 figures. Submitted for publication to JINST

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# Development of a 32-channel ASIC for an X-ray APD Detector onboard the ISS [IMA]

We report on the design and performance of a mixed-signal application specific integrated circuit (ASIC) dedicated to avalanche photodiodes (APDs) in order to detect hard X-ray emissions in a wide energy band onboard the International Space Station. To realize wide-band detection from 20 keV to 1 MeV, we use Ce:GAGG scintillators, each coupled to an APD, with low-noise front-end electronics capable of achieving a minimum energy detection threshold of 20 keV. The developed ASIC has the ability to read out 32-channel APD signals using 0.35 $\mu$m CMOS technology, and an analog amplifier at the input stage is designed to suppress the capacitive noise primarily arising from the large detector capacitance of the APDs. The ASIC achieves a performance of 2099 e$^{-}$ + 1.5 e$^{-}$/pF at root mean square (RMS) with a wide 300 fC dynamic range. Coupling a reverse-type APD with a Ce:GAGG scintillator, we obtain an energy resolution of 6.7% (FWHM) at 662 keV and a minimum detectable energy of 20 keV at room temperature (20 $^{\circ}$C). Furthermore, we examine the radiation tolerance for space applications by using a 90 MeV proton beam, confirming that the ASIC is free of single-event effects and can operate properly without serious degradation in analog and digital processing.

M. Arimoto, S. Harita, S. Sugita, et. al.
Mon, 20 Nov 17
29/56

Comments: Accepted for publication in NIMA

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# The integration and testing of the Mini-EUSO multi-level trigger system [IMA]

The Mini-EUSO telescope is designed by the JEM-EUSO Collaboration to observe the UV emission of the Earth from the vantage point of the International Space Station (ISS) in low Earth orbit. The main goal of the mission is to map the Earth in the UV, thus increasing the technological readiness level of future EUSO experiments and to lay the groundwork for the detection of Extreme Energy Cosmic Rays (EECRs) from space. Due to its high time resolution of 2.5 us, Mini-EUSO is capable of detecting a wide range of UV phenomena in the Earth’s atmosphere. In order to maximise the scientific return of the mission, it is necessary to implement a multi-level trigger logic for data selection over different timescales. This logic is key to the success of the mission and thus must be thoroughly tested and carefully integrated into the data processing system prior to the launch. This article introduces the motivation behind the trigger design and details the integration and testing of the logic.

A. Belov, M. Bertaina, F. Capel, et. al.
Wed, 8 Nov 17
53/84

Comments: 24 pages, 11 figures. Accepted for publication in ASR

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# The integration and testing of the Mini-EUSO multi-level trigger system [IMA]

The Mini-EUSO telescope is designed by the JEM-EUSO Collaboration to observe the UV emission of the Earth from the vantage point of the International Space Station (ISS) in low Earth orbit. The main goal of the mission is to map the Earth in the UV, thus increasing the technological readiness level of future EUSO experiments and to lay the groundwork for the detection of Extreme Energy Cosmic Rays (EECRs) from space. Due to its high time resolution of 2.5 us, Mini-EUSO is capable of detecting a wide range of UV phenomena in the Earth’s atmosphere. In order to maximise the scientific return of the mission, it is necessary to implement a multi-level trigger logic for data selection over different timescales. This logic is key to the success of the mission and thus must be thoroughly tested and carefully integrated into the data processing system prior to the launch. This article introduces the motivation behind the trigger design and details the integration and testing of the logic.

A. Belov, M. Bertaina, F. Capel, et. al.
Wed, 8 Nov 17
53/84

Comments: 24 pages, 11 figures. Accepted for publication in ASR

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# Current status and projected sensitivity of COSINE-100 [CL]

COSINE-100, a direct detection WIMP dark matter search, is using 106 kg of NaI(Tl) crystals to definitively test the DAMA collaboration’s claim of WIMP discovery. In the context of most standard models of WIMP dark matter, the DAMA result is in conflict with other direct detection experiments. To resolve this tension, COSINE-100 seeks to independently test the DAMA observation using a detector of the same target material as DAMA, thus definitively confirming or refuting their claim of WIMP discovery. Here, we present the current status and projected sensitivity of COSINE-100, along with the projected sensitivity of COSINE-200, a possible next phase of the experiment.

W. Thompson and 100. Collaboration-COSINE
Tue, 7 Nov 17
43/118

Comments: 5 pages, 3 figures. To be included as part of the Proceedings of the XV International Conference on Topics in Astroparticle and Underground Physics (TAUP2017) in the Journal of Physics: Conference Series (JPCS)