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--- cupid_pub:the_cupid_experiment [2021/05/22 14:02]
benato [The Experiment]
+++ cupid_pub:the_cupid_experiment [2021/06/04 08:31] (current)
benato [The Experiment]
@@ Line 44: / Line 44: @@
 |{{ cupid_pub:double_beta.png?330 }} |{{ cupid_pub:screenshot_20210522_144702.jpeg?330 }}|
-|Decay scheme of 2νββ (top) and 0νββ decay (bottom). The two processes share the same parent and daughter nucleus, but differ for the number of emitted partiles, and consequently their energy.|The measurable sum electron spectrum is a continuum for 2νββ decay, and an excess at Q<sub>ββ</sub> for 0νββ decay.|
+|Decay scheme of 2νββ (top) and 0νββ decay (bottom). The two processes share the same parent and daughter nucleus, but differ for the number of emitted particles, and consequently their energy.|The measurable sum electron spectrum is a continuum for 2νββ decay, and an excess at Q<sub>ββ</sub> for 0νββ decay.|
@@ Line 57: / Line 57: @@
 It is located at the [[https://www.lngs.infn.it|Laboratori Nazionali del Gran Sasso (LNGS)]]  of INFN, in the Abruzzo region in central Italy.
 CUORE is composed of 988 TeO<sub>2</sub> crystals operated as cryogenic calorimeters at a temperature of 10-15 mK. The crystals act simultaneously as detectors and source of 0νββ decay: in fact, they contain the ββ decay isotope <sup>130</sup>Te, that contributes to ~27% of the crystal mass.
-The CUORE detectors are operated in the largest dilution refrigerator ever build((J. Ouellet, [[https://arxiv.org/abs/1410.1560|arXiv:1410.1560]])), capable of cooling down ~1.5 tons of material to base temperature.
+The CUORE detectors are operated in the largest dilution refrigerator ever build((J. Ouellet, [[https://arxiv.org/abs/1410.1560|arXiv:1410.1560]])), capable of cooling down ~1.5 tons of material to base temperature about a month, and operating it stably for years.
 |{{cupid_pub:campo-imperatore.jpg?450}}|{{cupid_pub:cuore_clean_room.jpg?350}}|
 |The Gran Sasso National Park, below which the underground lab of LNGS is located.|The CUORE detectors right after their installation in the cryostat.|
+CUPID will profit of the established CUORE cryogenic infrastructure, and deploy ~1500  Li<sub>2 </sub>MoO<sub>4</sub> crystals in place of the TeO<sub>2</sub> ones.
+Thus, CUPID will not only change the crystal, but also the candidate isotope. The reason for this choice is twofold:
+on the one hand, Li<sub>2 </sub>MoO<sub>4</sub> is a scintillating material with a particle-dependent light yield,
+on the other hand the candidate isotope <sup>100</sup>Mo has a Q-value of 3034 keV
+(compared to 2527 keV of <sup>130</sup>Te), which lies above most of the γ background from environmental radioactivity. Special attention is paid to the minimization of the radioactive contamination levels of all employed materials. Using the information from the predecessor experiments CUORE, [[https://cupid-0.lngs.infn.it/|CUPID-0]], and [[https://cupid-mo.mit.edu|CUPID-Mo]], the projected background at Q<sub>ββ</sub> is expected to be at the level of 10<sup>-4</sup> counts/keV/kg/yr.
+CUPID-Mo  has  robustly  demonstrated  that Li<sub>2</sub>MoO<sub>4</sub> scintillating bolometers
+meet the requirement for CUPID. CUPID-Mo was an array of 20 elements that took data until 2020 in the Modane underground laboratory in France, as a follow-up  of  the LUMINEU  project.
+It  has shown  the  maturity  reached  by  the proposed CUPID  technology  and  the  high  standard  of the Li<sub>2</sub>MoO<sub>4</sub> detectors  in  terms  of  energy resolution, α/β rejection capabilities, internal radiopurity, and overall reproducibility of the results.
-The future of the CUORE experiment is the  CUPID project, whose  goal is  to measure the  0υ2β decay in the <sup>100</sup>Mo isotope instead of <sup>130</sup>Te used in CUORE using 1500   Li<sub>2 </sub>MoO<sub>4</sub> crystals  . The main reason for the change in the target material is due to the scintillating properties of the  Li<sub>2 </sub>MoO<sub>4</sub> which are necessary for the particle identification.
-The CUPID crystal will be placed inside  the CUORE cryostat arranged as in the sketch shown below.
 |{{cupid_pub:cuore_cryostat_3.jpg?nolink&545}}|{{cupid_pub:cupidrendering.jpg?nolink&300}}|
@@ Line 72: / Line 76: @@
-==== The Detector ====
+===== The Detector =====
-The CUPID crystals are operated as cryogenic calorimeters, each equipped with a cryogenic light detector. A particle interaction in the crystal produces a phonon  and light signal (see figure below), the latter one is used to discriminate  α background from the electrons events.
-{{ :cupid_pub:cupid_detector.png?450 |}}
+In CUPID, the Li<sub>2</sub>MoO<sub>4</sub> crystals are operated as cryogenic calorimeters, and coupled to a light detector. The light detectors are germanium wafers, and are also instrumented as calorimeters.
+A particle interaction in the crystal produces phonons and scintillation light.
+The heat from recombining phonons is read by a Neutron Transmutation Doped (NTD) germanium thermistor
+glued to the crystal. The light escapes the crystal, inducing a phonon signal in the light detector, which is also read by an NTD.
+|{{ cupid_pub:cupid_detector.png?350 }}|{{cupid_pub:screenshot_20210522_221509.jpeg?450}}|
+|Schematic of a cryogenic calorimeter, with the heat channel (blue) and a light detector (gray).|Installation of crystals for a CUPID test run. A light detector is visible in the bottom right.|

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