SIDDHARTA: the future of exotic atoms research at DAFNE Silicon Drift Detector for Hadronic Atom Research by Timing Applications   DAFNE-2004: Physics at meson factories Mihai Iliescu INFN-LNF 10-06-2004  

The goal of KH and KD measurements a few eV determination of both shift and width of the 1s level induced by the strong interaction in the Kp and KD atomic systems The main feature to deal with, in order to obtain the desired accuracy, is the S/B ratio. This requires to pass from 1:70 (KH today) to at least 1:1 (KH) and 1:5 (KD-first time)

Experimental requirements for the measurements a triggerable, large area, high resolution, high efficiency in the energy region of interest (1-20 KeV) X-ray detector

Triggerable SDDs A large area Silicon Drift Detector (SDD), equipped with trigger electronics, presently under development (SIDDHARTA project), satisfies the experimental requirements

Working principles of the SDD

The classical PIN (Positive-Intrinsic-Negative) diode detector Entrance window n + p - V c ANODE The anode capacitance is proportional to the detector active area

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

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

The integrated JFET Detector produced at Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany

Performances of the SDDs

Silicon Drift Detector QE and resolution 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

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

Spectroscopic resolution: detector comparison - 2 FWHMmeas of monoenergetic emission line 5.9 keV 1cm2 detector at 150 K SDD FWHM=140eV tshap =1ms Si(Li) FWHM=180eV tshap =15ms PIN diode FWHM=750eV tshap =20ms CCD FWHM=140eV tframe= ~ s

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

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

Triggered acquisition Kaon trigger Concidence windows Detected pulses Considered pulses X-ray pulse Background pulse Tdr max

Background reduction with triggered acquisition Machine Background NK = number of detected kaons per detected Ka X-ray = 103 Br = background rate = 103 events/s over 200 cm2, full spectrum (1-20 KeV) -->50 Hz/1KeV Tw = gate window Tw = NK x Tdrift max = 103 x 1 ms = 1ms B = Br x Tw = 50 s-1 x 10-3 s = 5 x 10-2 S/B=20/1 negligible Hadronic background (Kp-pS interaction, synchronous) preliminary simulation (typical SDD thickness 300 mm) S/B = 5/1 (KH), 1/4 (KD)

SDD test setup electronics layout P.S. Temp. control SDD canister 7 Shapers, peak stretchers & discriminators HV control Amplified SDD output signal Stretcher reset DAQ Analog output Shapers control motherboard Discrim. output Trigger (NIM logic) NIM 2 TTL Trigger signal Scintillators

Detector biasing parameters Test of the 30 mm2 SDD Detector biasing parameters Current Voltage electrode 400mA +12 V Drain - gnd IS,OS 20.9mA - 178 V R#N <0.1mA - 91 V Back 0.5mA - 18 V IGR 20.8mA - 10 V R#1

T = - 40°C, tsh=0.75ms

SIDDHARTA setup version 1 beam pipe and kaon trigger vacuum chamber feed-throughs for SDD electronics port for SDD cooling target cooling line SDD pre-amplifier electronics SDD detector chip target cell lead table

SIDDHARTA setup version 2 SDDs array Beam pipe e- e+ Kaon trigger Cryogenic target cell

Kaons stopped inside target Kaon stopping distribution inside hydrogen target for a toroidal setup Signal: ~ 30 times more than in DEAR Kaons stopped inside target ~ 30% (all generated) MonteCarlo simulation

integrated luminosity SIDDHARTA Kaonic hydrogen simulated spectrum MonteCarlo simulation Precision on shift ~1 eV integrated luminosity 60 pb-1 S/B = 5/1

Precision on shift < 10 eV integrated luminosity SIDDHARTA Kaonic deuterium simulated spectrum Precision on shift < 10 eV S/B = 1/4 MonteCarlo simulation integrated luminosity 100 pb-1

SIDDHARTA collaboration LNF, Frascati (Italy) MPE, Garching (Germany) PNSensor, Munich (Germany) Politecnico, Milan (Italy) IMEP, Vienna (Austria) IFIN-HH, Bucharest (Romania)

Assembly on DAFNE and data taking Conclusions Results obtained with DEAR and evaluations done for SIDDHARTA show that DAFNE represents an ideal machine for hadronic atoms research Continuing tests on detectors to obtain best performance prototype, compatible with a large area setup. Finalizing the design of the new experimental setup: front-end electronics, mechanics, cryogenics, vacuum 2006 Assembly on DAFNE and data taking