New Developments of SDD-Based X-Ray Detectors for the Siddharta-2 Experiment

1. New Developments of SDD-Based X-Ray Detectors for the Siddharta-2 Experiment R. Quaglia1,2, L. Bombelli3, C. Fiorini1,2, G. Giacomini4, F. Ficorella4, A. Picciotto4 , C. Piemonte4 1Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy2INFN Sez. di Milano, Milan, Italy3XGLab srl, Milan, Italy4Fondazione Bruno Kessler, Trento, Italy

2. SIDDHARTA-2 SIliconDrift Detector for HadronicAtom Research by Timing Applications • LNF- INFN, Frascati, Italy • SMI- ÖAW, Vienna, Austria • IFIN – HH, Bucharest, Romania • Politecnico, Milano, Italy • Fondazione Bruno Kessler, Trento, Italy • RIKEN, Japan • Univ. Tokyo, Japan • Victoria Univ., Canada

3. K- Upgrade of the X-ray spectrometer for the SIDDHARTA-2 experiment Strong interactionstudies al low energy (non-perturbative QCD in strangeness sector) throughprecise X-ray spectroscopy measurementsof Kaonic atoms transitions X-ray Nucleus SDD array M. Bazzi et al., “Preliminary study of kaonic deuterium X-rays by the SIDDHARTA experiment at DAFNE”, Nucl. Phys. A907 (2013) 69-77. Upgrade the apparatus with200 cm2of new SDD detectors

4. SIDDHARTA-1 DETECTOR ARRAYS (produced at MPI-HLL, Munich, Germany) 1 cm2 x 144 SDDs

5. Development of SDDs by Politecnico & FBK • Started in 2011 within a project supported by ESA for LaBr3 scintillator readout with SDD arrays. • Back entrance window optimized to achieve QE > 80 % at 380 nm ( suitable also for soft X-rays). • Considered suitable for the upgrade of the Siddharta-2 apparatus, with preliminary evaluation on prototypes in 2012/2013 12 x 12 mm Array: 9 SDDs (8 x 8 mm each) 8 x 8 mm • FBK production: • 4’’ wafer • 6’’ wafer upgrade now operative Average leakage current: 2 nA/cm2

6. Front-end readout strategy radiation entrance window • CMOS Preamplifier ‘CUBE’ (recently developed at Politecnico di Milano*) • the whole preamplifier is connected close to the SDD (and not only the FET) • the high transconductanceof the input MOS compensates the larger capacitance introduced in the connection SDD-FET • the remaining part of the electronics (the ASIC of analog processing) can be placed relatively far from the detector (even 10-100cm) SDD CUBE *L. Bombelli, et al., “ “CUBE”, A Low-noise CMOS Preamplifier as Alternative to JFET Front-end for High-count Rate Spectroscopy”, Nuclear Science Symposium Conference Record, 2011, N40-5. 30 ns 55Fe signal (SDD) CUBE SDD

7. Spectroscopy with CUBE preamplifier • SDD characteristics: • Area = 10 mm2 (round) • T= -40 °C (Peltier cooling) • uncollimated source 55Fe spectrum 1.0 ms shaping time (optimum) 123.0 eV FWHM (ENC= 3.7 e- rms) 126.4 eVFWHM (ENC= 5.0 e- rms) 250 ns shaping time!

8. Single 8 x 8 mm detector (64 mm2) Test in a set-up with vacuum chamber and cryostat with a minimum temperature of 50 K. Low temperature operations are needed is Siddharta-2 to speed-up the drift time which is important for timing of the experiment. • Two biasing techniques of the back electrode: • independent bonding; • biasing with punch-through mechanism; Fiorini, C.; Longoni, A.; Lechner, P., "Single-sidebiasingofsilicondriftdetectorswithhomogeneouslight-entrancewindow," Nuclear Science IEEE Transactions on, Aug2000. holescurrentdensity The SDD is operated with the back electrode disconnected and biased by means of the punch-through technique. Thiseliminatesbondings on the backside  reduction of dead area in the detector hybrid punch- through

9. Single 8 x 8 mm detector (64 mm2) standard biasing punch-through back biasing 123.9 eV FWHM FWHM @ 6keV [eV] ENC = 4.0 e- Shaping Time [µs] y scale (FWHM) very small, 6 eV on all range (0.5 μs to 12 μs shaping time)! No penalizations with temperatures below 200 K. In figure measurements at 160 K. Similar performances below this temperature. Uncollimated source.

10. Single 12 x 12 mm detector (144 mm2) 130.4 eVFWHM 124.7 eV FWHM 0.5 μs shaping time at 60 K 4 μs shaping time at 60 K 8 mm First sampled tested recently. Successfully tested very good result at 150K, 100K and 50K. Test only with standard biasing of the back electrode. Uncollimated source. 12 mm 12 mm 8 mm

11. Monolithic array of 3x3 SDDs (6.7 cm2) 26 mm 26 mm Ceramic carrier 1mm dead space on each side: 85% active area 9 holes for bondings Bias through the punch–through mechanism (no bonding on the back side). CUBE preamplifier connector

12. Test of 9 SDDs array ASICs designed for gamma-spectroscopy with SDD • 27 channels • ShaperfilterSemi-Gaussian 7th ordercomplexpoles. • PeakingTime 2, 3, 4 or 6µs • 3 Gain: 10k, 20k, 30k equivalent e- • SPI 160 bits; • Multiplexer 27 to 1 • MUX clock 10 MHz • Digital transfer standard LVDS Quaglia, R.; et al."Readoutelectronics and DAQ system forsilicondrift detector arrays in gamma rayspectroscopyapplications," IEEE NSS/MIC/RTSD, 2012. Peloso, R. et al. "Developmentof a detector based on SiliconDriftDetectorsforgamma-rayspectroscopyforastronomyapplications," IEEE NSS/MIC/RTSD, 2012. Spectra with 1” LaBr3 scintillator (57Co, 137Cs, 60Co) and arrays with 9 SDDs

13. SDDs array readout with the ASIC 139.5 145.1 146.1 Preliminary tests with SDDs array made with Peltier cooling at temperature -30 °C note: leakage current still not negligible at this temperature: the resolution is consistentat this temperature for a 64 mm2 large device. FWHM FWHM FWHM 141.6 146.1 145.8 FWHM FWHM FWHM Results comparable with single channel measured at similar temperature FWHM FWHM FWHM 141.5 146.3 154.9 Future tests with array in vacuum chamber and lower temperature Nine spectra acquired with the ASIC, average FWHM: 145.21

14. Conclusions and future works • Experimentation of single SDD (8x8mm2 and 12x12mm2) as well as first arrays (3x3 units) show very good energy resolution performances • SDD technology together with CUBE preamplifier looks suitable for the Siddharta-2 upgrade • Design of a new readout ASIC compatible with SIDDHARTA-1 DAQ. • Definition of the basic detector for SIDDHARTA-2, size of the single element, number of SDDs per module, ecc…

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