Current status of R&D on MMC and TES and a full size crystal test setup Sang-jun Lee Seoul National University

2 Contents Neutrinoless double beta decay Low temperature detector Current status Future prospect

3 How can we detect 0  ? Wait for the two electrons signal

4

5 Choice of detector  : efficiency,  : enrichment, M : mass, t : time of measurement, B : background, FWHM : energy resolution 5

6 Low temperature detector (LTD) LTD measures temperature change at ultra-cold temperatures (<100 mK) Temperature change occurs due to energy deposition

7 Decay candidate

8 Examples of LTD Metallic Magnetic Calorimeter (MMC) Temperature change → Magnetization change Transition Edge Sensor (TES) Temperature change → Resistance change working point working point

9 Decay candidate

10 Scintillating CaMoO 4 Light detector with TES MMC

11 Energy deposited in the crystal Heat Light Background rejection 11 CdWO 4  

12 Dual channel detection - heat and light 1 cm  1 cm 241 Am

13 Heat Measurement

14 Full spectrum

15 Full spectrum alpha

16 Alpha energy spectrum FWHM = 11.2 keV 60 keV gamma added

17 Baseline resolution FWHM = 4.1 keV

18 Straggling effect of alpha source Pile-ups of 60 keV gammas Statistical fluctuations of lattice damage Temperature fluctuation etc.

19 Full spectrum 60 keV gamma

20 Gamma energy spectrum 42 keV FWHM = 1.7 keV Emission line of Mo : 18 keV

21 Heat signals due to high energy (~5 MeV) and low energy (~10 keV) measured at the same time Recently accepted in Journal of Astroparticle Physics

22 Light Measurement

23 TES Superconducting Normal conducting

24 Up to now, current status has been covered.

25 TES with lower Tc (<80mK) should be fabricated for light measurement Next challenge is to increase the size of CaMoO 4 by ~100 times.

26 Challenges 1)Development of heat sensor MMC 2)Thermal connection of MMC and CaMoO 4 3)Design of sample holder

27 1) Development of heat sensor MMC MMC used before is not recommended for an array of large crystals. Meander-type MMC recently developed by University of Heidelberg is needed.

28 2) Thermal connection of MMC and CaMoO 4 Previously, gold pattern was e-beam evaporated on the crystal to attach MMC Sputtering, not e-beam evaporation should be employed. crystal MMC

29 3) Design of sample holder Really small increase of temperature Detector should be thermally isolated from and firmly attached to the sample holder at the same time.

30 Cylinder Detector module Cylinder MeanderDummy Cylinder Meander Light detector Reflecting cavity

31 Light detector is coming soon. Large crystal setup takes time, and the solution to the challenges should be systematically approached.

32 Questions?