1. Possible Rad. Background in 136Xe DBD
Changbo Fu; Siguang Wang

2. How well other people did in the range interested?
Outline
What kinds of rad. background do we care? (for 136Xe ovbb)
How well other people did in the range interested?
What we will do (and/or improve) (Siguang will cover it)

3. What do We Care? 400---1000 times better to go!!!
136Xe (0vbb)=2.4578MeV
0vbb of 136Xe, for 752h data, limit now >1.1E25 (EXO-200)
1 evt 0vbb in 1000kg in 1y means: T1/2=4.4E27 y (target);
times better to go!!!

4. Poisons：Co60 (in CUORE) Xe136 (0VBB=2.4578） Co60 2.506MeV(I=2.0E-6)
dE=2% away

5. Poisons (Saw in GERDA) Th228(Th232,t=1.9y) Ac228(Th232,t=6min)
Co60 (Cu, cos.t=5.3y)
Bi214(U238,t=19.9min)
Alpha(U,Th)
K42(2.424MeV,gamma)
K40 (1.461MeV gamma)
Ge68

6. Poisons (Saw in NEXT) Tl208 (Th232, t=3.1min) 2526.507keV Ir=0.1708 %

7. Poisons （Saw in EXO200） Rn222 U238 Th232 Bi214 Co60 K40 Xe135!!! Mn54
Zn65
Multi-Sites
Single-Sites

8. Poisons (Saw in EXO200)
Theirs calibration data

9. Poisons (Saw in KamLand-Zen)

10. In JPUL Counting Station
Poisons (in PandaX)
7/keV/y
40K
208Tl (2618keV)
In JPUL Counting Station
Have data, but not analyzed yet!!!
Worthy to be digged out?

11. Summary (What? Where? and How much?)
What do we care?
Rn (&daughters)
238U (&daughters)
232Th (&daughters)
228Th(t=1.9y;surface)
60Co (Cu cosmic activation)
t=5.27y
85Kr, maybe ok
135Xe (Xe136(n,2n)?)
54Mn?
65Zn? …
Where are they?
Tiny in bulky
Metal
insulator
Tiny in Gas (Rn)
Tiny on Surface
How much we are talk about?
Sub-ppt level (<1E-12)
μBq/kg
Siguang will cover the tech to catch them

12. Thanks!

14. Exo Xe136

18. SuperCDMS Carbon fiber, Dragonplate CFRP Th-232 2. 93 mBq/kg U-238 0
SuperCDMS Carbon fiber, Dragonplate CFRP Th mBq/kg U mBq/kg
Sample Description Carbon fiber, Dragonplate CFRP
Measurement Results
K (2.36) mBq/kg
Th (1.6) mBq/kg
U (0.621) mBq/kg

19. SuperCDMS Carbon fiber rods Th-232 0.707 mBq/kg U-238 2.791 mBq/kg
Sample Description Carbon fiber, 97 separator rods, diameter inches, length ~ 9.92 inches, total mass kg, total volume ~ in^3. Composed of carbon fill (we do not know anything about the purity of the carbon or the CF composition, but a rough estimate is 67% carbon by volume), epoxy (Bisphenol F Epoxy, C:H:0 is 13:12:02, ~33% Bis F Epoxy by volume), hardener (type Unknown)
Measurement Results
K (4.96) mBq/kg
Th (1.39) mBq/kg
U (0.885) mBq/kg

20. 212Bi(beta)
212Po(alpha)(in 1E-7s)
208Pb
alpha
beta
beta1
beta2