1. The first results on cryogenic semiconductor detectors for advancing the LHC beam loss monitors Presented by Vladimir Eremin on behalf of Ioffe PTI (St.Petersburg) RIMST (Zelenograd) BE-BI-BL, Cryo lab., and RD39 (CERN) teams V. Eremin, Bari, 29.05 – 1.06.12

2. The new BLM arrangement V. Eremin, Bari, 29.05 – 1.06.12

3. TCT cryogenic module V. Eremin, Bari, 29.05 – 1.06.12

4. Arrangement with 5 cryogenic modules V. Eremin, Bari, 29.05 – 1.06.12

5. Inside the cryostate V. Eremin, Bari, 29.05 – 1.06.12

6. Cryostat V. Eremin, Bari, 29.05 – 1.06.12

7. The beam test area V. Eremin, Bari, 29.05 – 1.06.12

8. Charge collection V. Eremin, Bari, 29.05 – 1.06.12

9. Electron collection V. Eremin, Bari, 29.05 – 1.06.12

10. Hole drift velocity V. Eremin, Bari, 29.05 – 1.06.12

11. Collected charge in Silicon and Diamond detectors V. Eremin, Bari, 29.05 – 1.06.12

12. Sc diamond detector polarization V. Eremin, Bari, 29.05 – 1.06.12

13. Polarization time in diamond The polarization criteria E(x) x t = 0 N eff = 0 t=t pol N eff = N cr Detector at: Vb = 1000V W = 500um Ncr = 1e12 cm-3 n cr = Ncr x W = 1e11cm-2 Polarization time (estimation) R = 1e6 MIP cm-2 c-1 1MIP – 1e4 pairs CCE = 0.9 n tr = 1e4x(1-CCE)xR = 1e9 cm-2 c-1 t pol = n cr / n tr = 100 c More details on polarization: B.Dezillie, et al. NIM A 452, 2000,p.440 Polarization by trapping: MGA (2.7eV) σ tr =1e-15cm2, Ntr=1e15 cm-3) RT Trapping time = 1e-7c Detrapping time = 1e35 c Collection time = 1e-8 s V. Eremin, Bari, 29.05 – 1.06.12

14. P+N+ Neff(t) + _ Electric field evolution in detectors under bulk polarization Critical time t cr E(x) x t = 0 t pol = C*V / {I*(1-CCE)} At J bulk = 1e-9 A/cm2 t pol = < 1000c !!!! Critical for deep level rich semiconductors V. Eremin, Bari, 29.05 – 1.06.12

15. E(x) x Me Neff(t) + _ Electric field evolution in detectors under charge accumulation at the contacts Critical time t cr t pol = C*V / {I*(1-CCE)} At J bulk = 1e-9 A/cm2 t pol = < 1000c !!!! Critical for the wide band semiconductor detectors with M-S-M structure t = 0 V. Eremin, Bari, 29.05 – 1.06.12

16. P+N+ Neff(t) + Double side injection structures as a possible solution E(n+) = E(p+) = 0 E(x) x t = 0 Critical condition: Injection at cryogenic temperatures. The best candidate – silicon P-I-N structure with higly doped contacts. V. Eremin, Bari, 29.05 – 1.06.12

17. Comparison of Surface-barrier and P-I-N detectors Me Surface Bulk S/B detector or M-S-M Me P + (boron) Bulk N + (phosphorus) Me P-I-N V. Eremin, Bari, 29.05 – 1.06.12

18. Electric field and potential at the detector entrance window Degenerate Silicon Si=Me V. Eremin, Bari, 29.05 – 1.06.12

19. Conclusions Polarization could be a major drawback for Diamond and Silicon detectors operated at high counting rate at very low temperatures. The possible solution for Silicon detectors is a P-I-N structures with thin and abrupt highly doped contacts. For Diamond detectors the solution is not evident. The modules with optimized P-I-N structures must be studied with MIP’s laser simulator and in test beams of 2012. Thank you for your attention V. Eremin, Bari, 29.05 – 1.06.12