Development of High Purity Germanium Detector Techniques for

Development of High Purity Germanium Detector Techniques for Applications in Fundamental Research @ Universitaet Tuebingen Test of 1 kg point contact detector and CDEX-1 Data Analysis Process Wu Yucheng CDEX collaboration 2021/9/16

Outline • System Setup • System Performance • Data Analysis • Summary Detector Shielding Electronics Energy linearity (Calibration) Energy resolution Decays of characteristic X-rays Data quality check Background & Microphonics Cut Physics Interpretation 2

System Setup: Detector 1 kg-PPCGe (Canberra 2010. 12) 1 kg (Φ 62. 2× 62. 3, 187 cm 3, 994 g) Dead Layer: < 0. 5 mm/Ge (Canberra) P-type Crystal P+ Point Contact (few mm, few p. F) HV: +3500 V Pulsed Optical Reset pre. AMP (P+ Contact) RC Feedback pre. AMP (N+ Contact, HV module) • Cryostat: OFHC, 1. 5 mm • Dewar: 30 L (LN 2 Holding time – 14 days) • • • 3

System Setup: Shielding System CJPL PE Pb PE(B) Cu Rock PE Pb PE(B) Cu 2400 m 1 m 20 cm 4

System Setup: Electronics Systematic Setup Pulser FADC Trigger 1 kg-PPCGe Pulsed optical S 1 feedback Preamplifier Resistive feedback Preamplifier Random Trigger S 2 VME BUS VME Crate PC Slow Pulse Spec AMP Discriminator Logic 6μs/12μs Timing AMP 10 ns(int. ) Spec AMP 2μs Fast Pulse HV Supply NIM Crate 5

System Performance: Energy linearity Energy Linearity Source E /ke. V RT 0 68, 71 Ge 1. 299 152 Eu 121. 78 65 Zn 8. 979 152 Eu 244. 70 68, 71 Ge 10. 367 152 Eu 344. 28 Source E /ke. V RT 0 152 Eu 121. 78 152 Eu 244. 70 152 Eu 344. 28 152 Eu 778. 90 152 Eu 867. 37 152 Eu 964. 08 152 Eu 1408. 1 Below 12 ke. V: Intrinsic Background; 0. 3 – 3 Me. V: 152 Eu sample. 6

System Performance: Energy resolution • Energy Resolution 246 e. V @ 10. 37 ke. V 8. 5 ke. V @ 964. 08 ke. V 7

System Performance: X-ray Decay Cosmogenic isotope: 68, 71 Ge: K-shell EC X-ray : 10. 37 ke. V L-shell EC X-ray : 1. 29 ke. V Lifetime” 68 Ge: 270. 8 day 71 Ge: 11. 43 day 8

Data Analysis: Data Quality Check S 1 S 2 9

Data Analysis: Physics Interpretation Center of mass frame Elastic scattering WIMP θ E Target a, b, d, f c, e, f a. Earth velocity relative to dark halo b. Quenching factor: nuclear VS electron recoil c. ER Mχ = 10 Ge. V, σ = 10 -40 cm 2 Form factor d. Energy resolution and threshold of detector e. Spin: dependent VS independent f. Mixed components J. D. Lewin and P. F. Smith, Astrop. Phys. 6 (1996) 87 10

Data Analysis: Physics Interpretation With WIMP signal • Maximum Likelihood Method Without WIMP signal • Maximum Gap Method • Binned Poisson Method Conservative! G. Savage, et al, JCAP. 04 (2009) 010 11

Data Analysis: Physics Interpretation Pre d e t dic Anti-Compton Surface/Bulk 12

Summary • 1 kg-PPCGe has been set up • System performance is good Energy Linearity; Energy resolution; Threshold; Decays • Data analysis is processing Quality check Background subtraction Physics interpretation • Optimistic physics result 13

Thanks for your attention! Questions and Comments … 14