A new tile calorimeter with Silicon Photomultipliers for the KLOE-2 experiment Ivano Sarra University of Tor Vergata Laboratori Nazionali di Frascati Young Researcher Program @ Frascati Spring School 2008 LNF- Frascati ( 13-5-2008)

Summary of the existing QCAL Outline The proposal of a new quadrupole calorimeter QCALT A new kind of device: the SIPM Test on SiPM (Hamamatsu MPPC) Test on different fiber types Tests on Tiles Conclusions

Summary of the existing QCAL Summary of the existing QCAL At KLOE the measurement of direct CP violation is possible through the double ratio: R = G(KL p+p) G(KS p0p0) / G(KS p+p) G(KLp0p0) For the neutral decay of KL ―› 2π0 ―› 4γ To recover photons lost on the quadrupole region the area is covered by a Tile Calorimeter QCAL

Proposal of new QCAL Proposal of new QCAL For the high precision measurement of KL20 decay rate - Adapt a new calorimeter over new interaction region - Improve granularity, time resolution & efficiency. Barrel with 12 modules - Each module has a thickness of 5-6 cm and 1 m length. It is made by 8 layers of 2 mm W /3 mm Scint. Z R Along Z, each slab is divided in 20 tiles of 5x5 cm2 Tile dimension increases along R. Z

New tile design New tiles design MPPC = SIPM by Hamamatsu 1 mm^2 area The R&D for Tesla/ILC made possible a very promising tile detector: - Square tiles with fibers in circular grooves. - Tile readout is possible with SiPM SIPM =SILICON PHOTOMULTIPLIER Array of Single Geiger Mode APD. It is a discrete detector for photon counting depending on the PIXEL size MPPC = SIPM by Hamamatsu 1 mm^2 area 100 pixels --> 100 um 400 pixels --> 50 um

Test on SiPM

First study on SiPM First study on SiPM To study SiPM characteristics we use: Black box Pulsed led to fire SiPM Polaroid filter to change light intensity We can measure: Gain vs Vbias Gain vs Temperature Dark noise rate

SIPM signal with BLUE Led Pulser From Scope: Vbias 69.25Volt, T:24°C Rise Time ~3ns, Fall Time ~150ns From Adc: 0pe 1pe 2pe 3pe 4pe From ADC spectra, we get single photoelectron charge (Vbias 69.25, T:24°C): Q = 0.36pC Gain = 2.3E+06 Δcount=17.4 Q’=17.4*0.25pC=4.35pC Q=4.35/11.8(ampl.)=0.36pC G=Q/e

Gain vs T ΔG = -0.12 ΔT Our result Vbias=69.30V Hamamatsu ΔG=-0.12 ΔT

Dark Count vs Vbias Dark-Count(kHz) Our result Hamamatsu

Test on fibers

Test of single Scintillating Fibers We have studied the characteristics of 3 different types of fibers: Kuraray SCSF 81 (Blue ) Saint Gobain BCF92 single cladding (Green) Saint Gobain BCF92 multi cladding (Green) The test is performed using SiPM and a beta source of Sr90. The trigger is provided by a NE110 finger (1cm x 5cm) readout by 1” PM. SiPM + electronics fiber Sr90 NE110 PM Trigger

Selected Scintillating Fibers After the test we have selected: Saint-Gobain Multi Cladding fibers: 1) Best light yield 2) Fast emission time (3-4 ns/p.e.) 3) High attenuation length (3.5 m) Q( ADC COUNTS)

Test on tiles

Test of tiles 3 possible solutions under study: 1) SIPM directly on tile 2) SIPM + amplifier + HV on tile 3) SIPM connected to fibers in a far-away position from tile At the moment we have tested only the third solution: Tiles: 3mm and 5 mm thickness Without reflector at fiber end Simple mylar around tile SiPM placed outside tile in optical contact (w grease) with fiber.

Test of Tiles Data taking with cosmic rays. Trigger using 2 scintillator counters read at both ends. Tested 2 tiles with different thickness and different SIPM. To investigate the use of SIPM@400 pixels (vs SIPM@100 pixels) which has: a gain reduction of 1/3 (7.5 10+5 instead 2.4E10+6) a reduced temperature dependence DG = -0.03DT (instead -0.12) SiPM + electronics NE110 Trigger Tile Fiber Scintillator

Test of Tiles (MIP distribution) ADC distributions for two different thicknesses The MIP values are compatible taking into account different thicknesses and QE of the two SIPMs. N3mm = N5mm x 3/5 x 0.40/0.45 N3mm ~ 14 3mm thick 400 Pixels SIPM <MIP> = 14 pe 5mm thick 100 Pixels SIPM <MIP> = 26 pe

Tile test (time resolution for MIP) 110 ps/counts 5 mm thick 3 mm thick TDC ( Counts) After correcting the pulse height dependence on the timing, a Time Resolution of 750 (1000) ps is obtained for a MIP on the 5 (3) mm thick tiles. No correction applied to the trigger jitter.

Conclusions and plans SiPM: our tests confirm Hamamatsu characteristics for 100 pixels MPPC: - Gain vs HV - Gain vs temperature - Dark noise Reduced temperature variation of gain and dark noise expected for a 400 pixels MPPC (50 m pixel). Fibers: adopted solution is the Saint Gobain multi cladding. Tile: Good results on light response and timing. Light yield and time resolution sufficient for our purposes. Solution with MPPC+amp directly on tile under development.

Spares

Set Up - HV stability 10 mV - Blue LED diode on SiPM Temperature measured on SiPM CAMAC DAQ ADC sensitivity 0.25 pC/cnt

Mppc: Multi Pixel Foton Counter Mppc: Multi Pixel Foton Counter -100C N.370, characteristics at 25°C and λ=655 nm: Vop. 69,28V, Gain 2.41E+6

The KLOE experiment The KLOE design was driven by the measurement of direct CP violation through the double ratio: R = G(KL p+p) G(KS p0p0) / G(KS p+p) G(KLp0p0) Collision at sqrt(s)=Mphi = 1.02GeV (e-e+)―› Φ ―› (kS kL) (k- k+) Electromagnetic Calorimeter Measure charged particles lead/scint. fibers 4880 PM Drift Chamber Measure charged particles (4 m thick  3.4 m lenght)  90% He; 10% iC4H10 52140 wires Superconducting coil B=6kGauss

Dark Count shape vs Vbias Vbias 68.90V Vbias 68.97V 0.5pe 470kHz 1.5pe 34kHz 0.5pe 530kHz 1.5pe 40kHz T = 24 °C V=R*I=R*Q/τ, Where: τ = 35ns R = 50Ω Dark rate follows specifications. It becomes negligible when triggering at 1.5 pe. Vbias 69.03V Vbias 69.09V 0.5pe 610kHz 1.5pe 58kHz 0.5pe 680kHz 1.5pe 85kHz

Tile test Time resolution measured using different number of photoelectrons on tile. Result compatible with 5mm tile. No trigger jitter corrected. Stochastic term roughly consistent with:

Fibers test Saint Gobain multi cladding Pedestal Cut @ 0.5 pe

Fibers test Saint Gobain single cladding Pedestal Cut @ 0.5 pe

Fibers test Kuraray Y11 Pedestal Cut @ 0.5 pe Cut @ 1.5 pe 0pe 1pe 2pe

Tile test Entries ADC distribution obtained using a 3mm tile optically coupled with a 400 pixels SiPM. 0pe 1pe ADC counts

Tile test Using 3mm tile with 400 pixels MPPC. Slewing correction. Fit function: TDC Vs ADC The use of a fixed threshold TDC brings about a dependence of the threshold crossing time on the collected charge, the well-known time-slewing effect. Charge of imput signal [ADC counts]

Apd operanti in Geiger Mode Diodo a Vbias > Vbd t < t0 ... i=0, non ci sono portatori t = t0, inizia la valanga t0 < t < t1, la valanga si diffonde t > t1, la valanga si auto-sostiene ed è limitata ad Imax dalle resistenze in serie t t0 i imax t1 Vbias Vbd Meccanismo di Quencing

Apd operanti in Geiger Mode Gli Apd operanti in geiger mode possono essere modellati tramite il seguente circuito elettronico: Switch Open: quando la valanga non è innescata Cd si carica a Vbias e non scorre corrente Switch Close: quando la valanga si innesca Cd si scarica fino a Vbd con τ=Rs*Cd e la corrente va ad I=(Vbias-Vbd)/RQ τQ=RQ*Cd=35ns

Gain vs Vbias.2 From Hamamatsu: Our measurement:

Gain vs Vbias ADC spectra as a function of the applied HV. Gate: 350ns T=24°C Vbias 68.60V Vbias 68.66V Vbias 68.70V Vbias 68.75V Vbias 68.81V Vbias 68.87V

Gain vs Vbias Increasing HV we increase dark rate Vbias 68.94V

Gain vs Vbias Our result Hamamatsu ΔG=2.24 ΔV ΔG=2.19ΔV ΔG=2.12ΔV