MMC-based low-temperature detector system of the AMoRE-Pilot experiment

Abstract

Metallic magnetic calorimeters (MMCs) are highly sensitive temperature sensors that operate at millikelvin temperatures. An energy deposit in a detector can be measured using an MMC through the induced temperature increase. The MMC signal, i.e., a variation in magnetization can then be measured using a superconducting quantum interference device. MMCs are used in particle physics experiments searching for rare processes as their high sensitivity and fast response provide high energy and timing resolutions and good particle discrimination. Low-temperature detectors consisting of molybdenum-based scintillating crystals read out via MMCs were designed and built to perform simultaneous measurements of heat and light signals at millikelvin temperatures. These detectors have been used in the advanced Mo-based rare process experiment (AMoRE) that searches for the neutrinoless double beta decay of 100Mo. This article provides a detailed description of the MMC-based low-temperature detector system of the AMoRE-Pilot experiment which currently uses five crystals.

Status of the AMoRE experiment to search for Neutrinoless Double Beta Decay of Mo-100

“…The CMO detector assembly is placed in the cryogen-free dilution refrigerator (CFDR) system, which uses a pulse tube refrigerator, providing sufficient cooling power for the system. Performance of the dilution refrigerator confirmed that base temperature of the system reaches below 10 mK and that it has 1.6 µW of cooling power at 10 mK in normal operating condition [13]. In order to isolate the detector system from vibrations of the cryogenic system, R&D has been on-going and possible options were considered such as active damper.…”

“…The simultaneous measurements of phonon and light signals provide clear separation between α and β /γ events. Detailed principles and designs of detector and sensors are in [4,10,11,12,13]. Recent measurements with prototype detectors during engineering operations showed an energy resolution of 8.7 keV FWHM at 2.6 MeV and clear separations between α and β /γ events [12].…”

An MMC-Based Temperature Control System for a Long-Term Data Collection

“…The dilution refrigerator system that hosted the AMoRE-Pilot experiment [9,10] has currently been used for its successive AMoRE-I phase with 18 crystal modules and 36 MMC detection channels [11]. The lowest temperature reached 9 mK at the mixing chamber plate (MCP) and detector plate (DP) for this phase.…”

First results from the AMoRE-Pilot neutrinoless double beta decay experiment

“…A persistent current in the superconducting coil generates a magnetic field in the Au:Er sensor material, and energy deposited in the crystal produces a temperature increase in the Au:Er that alters its magnetization. This results in a change in the coil current that is measured by a superconducting quantum interference device (SQUID) [31]. Because of the high sensitivity of the MMC sensors, the detector setup is able to measure precisely the temperature increase resulting from any type of radiation absorption, and particle detection with very high energy resolution is achievable [35,40].…”

“…The advanced molybdenum-based rare process experiment (AMoRE) [28,29] aims to search for 0νββ decay of 100 Mo using a simultaneous heat and scintillation detection technique with crystals operating at mK temperatures. In the present stage of the project, AMoRE-Pilot, calcium molybdate (CaMoO 4 ) crystals are used as the active target elements in a detector concept where the source material is also the detection medium [30][31][32]. The crystals are 100 Mo-enriched and 48 Ca-depleted ( 48depl Ca 100 MoO 4 ).…”