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DEAR SDD --> SIDDHARTA

DEAR SDD --> SIDDHARTA Si licon D rift D etector for H adronic A tom R esearch and T iming A pplications Carlo Fiorini (Politecnico di Milano) Development of a soft X-ray detection apparatus, based on Silicon Drift Detectors (SDD), with high energy resolution

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DEAR SDD --> SIDDHARTA

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  1. DEAR SDD --> SIDDHARTA Silicon Drift Detector for Hadronic Atom Research and Timing Applications Carlo Fiorini (Politecnico di Milano) Development of a soft X-ray detection apparatus, based on Silicon Drift Detectors (SDD), with high energy resolution and high background reduction for application in exotic atoms researches

  2. Experimental requirements

  3. Exotic atom e.m. position of K line (keV)  (eV)  (eV) Required precision  (eV)  (eV) hydrogen 6.46  160  200 ~ 5 ~ 10 deuterium 7.81  500  800 ~ 25 ~ 100 Experimental requirements

  4. Working principles of the SDD

  5. The classical PIN diode detector The anode capacitance is proportional to the detector active area

  6. The Semiconductor Drift Detector The electrons are collected by the small anode, characterised by a low output capacitance. Anode Advantages:very high energy resolution at fast shaping times, due to the small anode capacitance, independent of the active area of the detector

  7. The Silicon Drift Detector with on-chip JFET • JFET integrated on the detector • capacitive ‘matching’: Cgate = Cdetector • minimization of the parasitic capacitances • reduction of the microphonic noise • simple solution for the connection detector-electronics in monolithic arrays • of several units

  8. The integrated JFET Detector produced at the MPI Halbleiterlabor, Munich, Germany

  9. Performances of the SDDs

  10. Silicon Drift Detector performances Quantum efficiency of a 300 mm thick SDD 55Fe spectrum measured with a SDD (5 mm2) at –10°C with 0.5 ms shaping time

  11. Silicon Drift Detector Droplet or SD3 T=-30°C a τsh=1µs Canode= 50 fF (vs. 100fF conventional SDD)

  12. Resolution in the line shift measurement

  13. SDD PIN Si(Li) 150 K 5.9 keV line 800 700 PIN Tsh=20us 600 500 FWHM (eV) 400 300 Si(Li) Tsh=20us 200 SDD Tsh=1us 100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 A (cm-2) Spectroscopic resolution: detector comparison - 1

  14. Spectroscopic resolution: detector comparison - 2 FWHMmeas of monoenergetic emission line 5.9 keV 1cm2detector at 150 K SDD FWHM=140eVtshap =1ms Si(Li) FWHM=180eVtshap =15ms PIN diode FWHM=750eVtshap =20ms CCD FWHM=140eVtframe=1s

  15. Measure of the line shift – ideal case * The case: kaonic hydrogen, 200 cm2 detection systemFor 6000 events (~50 pb-1 ) Estimated peak position 6.3 keV, line width about 245 eV, peak shift about 160 eVDetection system based on SDDs * No background contribution considered

  16. Background reduction

  17. IK IA hn hn t IA tdr max t Timing with the anode signal

  18. Timing resolution with SDD A=0.1cm2 Tdrift = 70ns A=0.5cm2Tdrift =350ns A= 1cm2Tdrift =700ns With: r= 2kW/cm H = 450mm

  19. Kaontrigger Concidencewindows tdr max Detectedpulses Consideredpulses Kaon trigger X-ray pulse Background pulse Triggered acquisition

  20. Background reduction with triggered acquisition r =number of detected kaons per detected X-ray = 103Br=background rate = 103 events/s Tw=sinchronization window Tw = r xt drift max = 103x 1 ms = 1ms B = Brx Tw = 103 s-1x 10-3 s = 1 S/B = 1/1

  21. Signal/Background with CCD ·Actual value of the S/B ratio measured with DEAR atDANEusing CCDsS/B  1/100 in kaonic hydrogen expected: S/B  1/500 in kaonic deuterium

  22. IK IA hn hn t IK t IA tdr max t Timing with the prompt signal from the backplane Estimated time resolution: about 300 ns

  23. Reliability of the detection set up

  24. Monolithic array of Silicon Drift Detectors Pixel area = 5 mm2 Total array area = 95 mm2

  25. Pb plate Ti foil Zr foil X-ray lines BTF e+/e - beam S1 S2 scintillators Pb shielding e+, e –g shower SDD X-ray detector (4 chips prototype) DEAR test setup (SDD) at the BTF

  26. Operations: The first stage of the project of the new detector deals with the characterization of the SDD performances. The characterization concerns the finalization of trigger efficiency and energy resolution, as a function of background environment and time window. This information will fix also the dimension of the single cell. These measurements are planned to be performed with a prototype device. The answers coming from these tests will be used for the construction of the final detector array and associated electronics with optimal characteristics.

  27. Beam conditions at BTF: Energy: varying between 50 ÷ 750 MeV Intensity: varying between 1÷ 103e+/e- s-1 (preference is for positrons) tbunch :  10 ns; bunch frequency: 1 ÷ 49 Hz Gate window 0.1 – 1 ms BTF run period required: 2-4 weeks in the period June 2003 - October 2003

  28. The detector: 1 cm2 SDD prototype Front-side: field strips, JFET Back-side: entrance window • 65 rings, 1 cm2 area • 280mm high-resistivity + 12mm epi-layer detector presently under test at Politecnico di Milano

  29. Preliminary measurements Leakage current ~ 3 nA @ room T Voltage divider threshold voltage ~ -50V for 8 rings ( 65 rings bias should be feasible with ~ - 400V)

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