Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
cupid_pub:the_cupid_experiment [2021/05/19 21:40] – [The 0νββ decay signature] dilorenzo1cupid_pub:the_cupid_experiment [2021/06/04 08:31] (current) – [The Experiment] benato
Line 43: Line 43:
 to the Q-value. to the Q-value.
  
-{{ :cupid_pub:double_beta.png?330 |}} +|{{ cupid_pub:double_beta.png?330 }} |{{ cupid_pub:screenshot_20210522_144702.jpeg?330 }}| 
-{{cupid_pub:spectrum.png?440}} +|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 54: Line 52:
  
 =====The Experiment===== =====The Experiment=====
-The first experiments trying to measure  0υ2β  are dated back to the end of the  '40s. During the last decades  many experiments have been proposed to measure the neutrinoless double beta decay. 
- 
-Among the operating  neutrinoless double beta experiment, CUORE is one of the most promising experiment able to measure the 0υ2β for the first time.  
-CUORE is located at the Laboratori Nazionali del Gran Sasso (LNGS) in the  Abruzzo region, beneath Monte Aquila, surrounded by at least 1400 meters (~3800 m.w.e.) of rock in all the direction. 
- 
- 
-{{ :cupid_pub:campo-imperatore.jpg?400 |}} 
- 
- 
-The CUORE detector is composed by 988 crystals operated at cryogenic temperature and equipped with sensitive thermometers (bolometers) made by TeO<sub>2</sub> searching for the 0υ2β  in<sup>130</sup>Te.  
- 
-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:image2.jpeg?200|}} 
-{{ :cupid_pub:cryostat2.jpg?200 |}} 
- 
- 
- 
- 
-==== 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 |}} 
- 
- 
- 
- 
- 
- 
  
 +The first experimental attempts to detect 0νββ decay are date back to the 1940s. Over the decades, many different technologies have been developed to search for this process on a variety of candidate isotopes.
 +Presently, [[https://cuore.lngs.infn.it/|CUORE]]((CUORE is again an acronym, standing for Cryogenic Underground Observatory for Rare Events.)) is one of the most sensitive experiments in the field.
 +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 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.
  
  
 +|{{cupid_pub:cuore_cryostat_3.jpg?nolink&545}}|{{cupid_pub:cupidrendering.jpg?nolink&300}}|
 +|The CUORE/CUPID cryostat during its construction, with the distillation unit visible in the middle.|CUPID geometry in Geant4 Monte Carlo simulation.|
  
  
 +===== The Detector =====
  
 +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.|