Radiation Monitor: Concepts, Simulation for an Advanced Read Out R.Cardarelli end A.Di Ciaccio INFN-Roma Tor Vergata Super-B Collaboration meeting 31/05/2012 Isola d’Elba La Biodola

Outline Location of the beam monitor in the Super-B detector Geant4 simulation to define the parameters of the monitor detector and F.E. electronic Test of a mono c. v.s. poli c. diamond detector with SiGe amplifier Conclusions and future plane

Radiation Monitor near SVT . Diamond detectors Primary goal: protect the SVT from high beam losses Next features: time of flight measurements to distinguish collisions events from background

Geant4 beam monitor simulation

Tentative detector shape R1 = 18.2 mm R = 18 mm L = 7 mm S = 1 mm R = 12 mm S = 1 mm

Geant4 results: rate per mm**2 for radiative Babbha Expected rate on Beam-monitor rings 1, 2 Bins da 1mm2 Highest rate about 0.25 MHz / mm2 (on Backward) Possible explanation : SuperB beam asymmetry Forw Back

Geant4 results : Edep Rate vs Edep Possible threshold at 150 KeV Violet band Particelle al minimo di ionizzazione

Geant4: time of flight 70 ps

Geant4 summary results L = 1 x 1036 cm-2 s-1 Rate (MHz) Edep/sec (GeV/s) nHits/Event Edep/Hit (GeV) Rate/mm2 (MHz/mm2) % Hits (>150KeV) Z (mm) Tube Ext (Back) 19.9 1780 0.09 9.0x10-5 0.035 22% -80 Tube Ext 2 (Back) 46.4 2080 0.20 4.5x10-5 0.082 10% -126 Tube Ext (Forw) 12.8 1115 0.06 8.7x10-5 0.023 21% 80 Tube Ext 2 (Forw) 30.0 1305 0.13 4.3x10-5 0.053 126

Diamond Detector (area 16mm**2) Rate/mm2 (MHz/mm2) Tube Ext (Back) 0.035 Tube Ext 2 (Back) 0.082 Tube Ext (Forw) 0.023 Tube Ext 2 (Forw) 0.053 CVD Parameters: traccolta: 20ns (on 1mm thickness) tintegr: 30ns Ethr > 150KeV max expected rate in selected regions for beam monitor 82 KHz /mm2 With a detector area of 16mm2 this corresponds to 1312 KHz Only 10% above 150KeV (only 130 KHz counted by the detector). 130 KHz corresponds to 0.3% electronics dead-time

Ionization currents on CVD diamonds Total Edep Edep/sec (GeV/s) Tube Ext (Back) 1780 Tube Ext 2 (Back) 2080 Tube Ext (Forw) 1115 Tube Ext 2 (Forw) 1305 Edep per mm2 al secondo N e-h pair / mm2 X s Area ring Current I per mm2 Energy necessary to produce a e-h pair in diamond For a sensor of 16mm2 an ionization corrente of 0.67 nA

geometry of the detector Diamond detector 4mm x 4mm 8 diamond detector for ring Beam monitor caracteristics L = 1 x 1036 cm-2 s-1 detector sized 8 X16 mm2 leakage current 8 nA Ionization current 0.67 nA hits rate 130KHz Detector Transit time 20 ns Electronic Integration time 30 ns Electric resistance 1011 Ωcm Energy threshold 150KeV Diamond detector 4mm x 4mm

Tentative electronic diagram Disipation power 8µW HV 500 Volt 100 kOhm 10m coax. Cable Ǿ = 0.7 mm Pico Amp Diamond detector amp Coincidence caunter CPU amp

BJT Si v.s. SiGe BJT Si BJT performances β=τc/τt ft=1/τt N= K*τt τc= base life time τt = base transient time τt (Si) >> τt (SiGe) diffusion Fermi energy B E C acceleration BJT SiGe Fermi energy B E C

Strategy for a new front-end(SiGe) A (mV) In signal A T(ns) F= 1 / T T(ns) 100 A (mV) Out signal 100 10 T(ns) 10 100 1000 ft F (MHz)

Amplifier, AC, (BJT SiGe, BFP740) Voltage supply 5 Volt Sensitivity 6 mV/fC noise 500 e- RMS Input impedance 50 Ohm B.W. 30 MHz Power consumption 10 mW/ch Low cost 2 – 3 eur./ch Radiation hardness 50 Mrad, 1015 n cm-2

Diamond detector under tests Mono crystal diamond thickness 0,5 mm Area 4 x 4 mm2 HV 400 Volt Dissipation power 8 μW

Current vs HV (sCVD- diamond detector)

Americium-241 + Sr-90 Am-241 Sr-90 noise

Coincidence with cosmics . 10ns Diamond detector PM

Coincidence with cosmics 2mV 5ns

Signal minimum ionization particle 20ns/div. 20ns/div.

Drift of the signal shape (s-CVD diamond)

Diamond detector under tests poly crystal diamond thickness 0,5 mm Area 4 x 4 mm2 HV 400 Volt Dissipation power 8 μW

Poly-CVD Diamond alfa-Am source ( log scale)

Idea on a new detector layout Transient time 5 ns Area 16 mm2 0.25 mm

Conclusions A Geant4 MC simulation of the SVT beam monitor was performed to determine Geometry Expected background rate Beam monitor FE electronics specification Next steps: further test of CVD diamonds (mono and poly-cristalline) with beams

Alfa Americium – 241 Alfa Americium-241 Noise

Amplifier, AC, (BJT SiGe, BFP650) Voltage supply 5 Volt Sensitivity 6 mV/fC noise 1000 e- RMS Input impedance 50 Ohm B.W. 30 MHz Power consumption 10 mW/ch Low cost 2 – 3 eur./ch Radiation hardness 50 Mrad, 1015 n cm-2

Alfa Americium – 241 Alfa Americium-241 noise

Amplificatore RC due stadi, AC, (BJT Si) Tensione di lavoro 5 Volt Sensibilita’ 6 mV/fC Rumore 4000 e RMS Impedenza di ingresso 50 Ohm B.W. 30 MHz

Simulazione Ove possibile, si sono utilizzate coppie vicine di volumi simili per ottenere un sampling più fine della rate attesa nella regione Tronco di cono inclinato per massimizzare il cammino della particella all’interno del volume

Signal minimum ionization particle 40ns/div.

Two stage ac amplifier, AC, (BJT Si BFQ67) Voltage supply 5 Volt Sensitivity 6 mV/fC noise 4000 e- RMS Input impedance 50 Ohm B.W. 30 MHz Power consumption 10 mW/ch Low cost 2 – 3 eur./ch

Noise distribution

Parametrizzazione dei rivelatori Calcolo della corrente di leakage su un sensore al diamante di 1mm x 1mm con una tensione applicata di 500V Resistenza offerta dal sensore Corrente di leakage che attraversa il sensore a fascio spento Per un sensore di 16mm2 si ottiene una corrente leakage di: 0.5x16 = 8 nA ovvero 80 x 10-10 A La corrente indotta dai fasci è 10 volte minore di quella di leakage quindi si richiede un elettronica in grado di rivelare piccole variazioni della corrente (almeno 1/10 della minima corrente da misurare)