New Development of Silicon Drift Detectors for the SIDDHARTA-2 experiment upgrade Carlo Fiorini, Riccardo Quaglia Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy. INFN, Sezione di Milano, Milano, Italy.

Outline The Silicon Drift Detectors (SDDs) in SIDDHARTA-1 New development of SDDs for SIDDHARTA-2 upgrade Present and future work

SIDDHARTA SIlicon Drift Detector for Hadronic Atom Research by Timing Applications LNF- INFN, Frascati, Italy SMI- ÖAW, Vienna, Austria IFIN – HH, Bucharest, Romania Politecnico, Milano, Italy MPE, Garching, Germany PNSensors, Munich, Germany RIKEN, Japan Univ. Tokyo, Japan Victoria Univ., Canada

The Silicon Drift Detector (SDD) Ionizing particle Rectifying electrodes Anodes The electrons are collected by the small anode, characterised by a low output capacitance, independent from the active area The drift time can be used to retrieve the position of interaction Anode Integration of the input FET on the detector to: - reduce of the parasitic capacitances of the connections between detector and electronics - improvement of the capacitive matching between detector gate capacitances (Cdet  Cgate) Features: optimized geometry for X-ray Spectroscopy low-noise, high-resolution

3 SDD (1cm 2 each) with on-chip JFET and feedback cap detector +readout module SDD board readout board with ASIC

Silicon Drift Detector - SDD 1Chip : 1 cm 2

1 cm 2 x 144 SDDs

What have we learned about the SDDs of SIDDHARTA-1? SDDs are a valuable X-ray spectroscopy detector for exotic atoms measurements but: latch-up of JFET integrated in the SDD during beam injection very fine tuning of bias of individual SDD was required dead-area of the detection module may be further minimized low-energy detection (<3keV) limited because of technical issues (electronics, thresholds, pick-up noise, …). …but no intrinsic SDD limitations (>200eV) ….. (our friends in Frascati may have learned much more than us….)

9 new target design new target design new SDD arrangement new SDD arrangement vacuum chamber vacuum chamber more cooling power more cooling power improved trigger scheme improved trigger scheme shielding and anti-coincidence (veto) shielding and anti-coincidence (veto) New SDDs – Milano – 200 cm 2 New SDDs – Milano – 200 cm 2 The SIDDHARTA-2 setup upgrade

New development of SDDs by Politecnico & FBK Started in 2011 within a project supported by ESA Considered very suitable for the upgrade of the Siddharta-2 apparatus, with preliminary evaluation on prototypes in 2012/2013 Key features of the proposed technological approach: 1) process of SDD detectors WITHOUT JFET integrated on the SDD itself (as used on current SIDDHARTA apparatus). advantages: - simplicity - much lower production costs (much less techn. steps) - faster production times (3-4 months vs. one year) - much lower dependence of settings/performances on bias voltages than with the present detectors - less sensitivity to latch-up during beam injection 2)SDD readout based on a new charge preamplifier “Cube” (recently developed at Politecnico di Milano): - allows high performances in X-ray spectroscopy still using ‘conventional’ SDD technology (W/O integrated JFET)

8 x 8 mm 2 single SDD Array: 9 SDDs (8 x 8 mm 2 each) 12 x 12 mm single SDD FBK production: 4’’ wafer 6’’ wafer upgrade just finished Present layouts of SDDs developed in the Polimi-FBK collaboration 26mm

JFET integrated on the SDD external CUBE preamplifier (MOSFET input transistor) lowest total anode capacitance limited JFET performances (gm, 1/f) sophisticated SDD+JFET technology larger total anode capacitance better FET performances standard SDD technology Now in Siddharta Proposed for Siddharta-2 SDD CUBE radiation entrance window cooler Front-end readout strategy

<1mm 3 CUBE: A full CMOS preamplifier can replace the single JFET+Cf+reset SDDCUBE Leakage and photons 30 ns 55 Fe signal (SDD) reset

SDD characteristics: Area = 10mm 2 T= -40°C 1.0  s shaping time (optimum) Best performances of new SDD technology and CUBE preamplifier 250ns shaping time best resolution ever obtained with a SDD (even with integrated JFET) at this short shaping time 126.4eV FWHM (ENC= 5.0 e- rms) 55 Fe spectrum eV FWHM (ENC= 3.7 e- rms)

Stability of the X-ray spectroscopy spectrum with SDD bias

Set-up for testing SDDs: Vacuum Chamber Vacuum Chamber Cryostat cooling down to 50 K Special 55 Fe source for vacuum application mounted here Connector to output SDD: 8x8 mm 2 Connector for bias and output

Stability tests (in Milano, other tests on-going in Frascati) square SDD: 64 mm 2 meas. time: 72 hours T= 100 K Rate: 1.1 kcps Vacuum chamber set-up. 72 hours FWHM= 126.8eV

Monolithic array of 3x3 SDDs: an ideal detector for Siddharta-2 upgrade 55 Fe spectra T=-20°C 26mm Ceramic carrier connector 9 holes for bondings CUBE preamplifier Detector module 1mm dead space on each side: 85% active area

Upgrade of Siddharta-2 spectrometer based on: -new SDDs development - CUBE and ASICs readout -low dead-area detection module design Few numbers: -200cm 2 of SDDs arrays -36 SDDs monolithic arrays -324 readout channels (drawings courtesy of SMI-ÖAW team)

ASIC to readout the SDD arrays  27 channels  Shaper filter Semi- Gaussian 7th order complex poles.  Peaking Time 2, 3, 4 or 6µs  3 Gain: 10k, 20k, 30k e-;  SPI 160 bits;  Multiplexer 27 to 1  MUX clock 10 MHz  Digital transfer standard LVDS From/To preamplifiers (Input signals, Reset) ASIC DAQ

Present and future work Experimentation of single SDD (8x8mm 2 ) almost completed (resolution, stability, linearity….) Experimentation of 3x3 SDDs array on the way: mounting and bonding optimization, yield test at low temperatures (100K) qualification as for the single SDD (Milano, Frascati) Design of a readout ASIC for the new SDD arrays Revision/design of the DAQ system Revision of components (detector layout, hybrids, module, …) for the SIDDHARTA-2 upgrade and production (depending on financing and support to man-power)

The new SDD development collaboration Politecnico di Milano and INFN, Milano, Italy C. Fiorini, R. Quaglia, P. Busca, R. Peloso, M. Occhipinti, L. Bombelli, A.Geraci Fondazione Bruno Kessler - FBK, Trento, Italy P. Bellutti, M. Boscardin, F. Ficorella, G. Giacomini, A. Picciotto, C. Piemonte, N. Zorzi LNF - INFN, Frascati, Italy M. Bazzi, M. Iliescu, F. Sirghi, C. Curceanu, ….