R&D program in JFY2002 for JLC vertex detector N.Tamura ; Niigata University Y.Sugimoto, A.Miyamoto ; KEK T. Aso ; Toyama National College of Maritime Technology K.Abe ; Tohoku Gakuin Univ. G.Iwai, K.Fujiwara, H.Takayama ; Niigata University

Contents I) Design concepts and Requirements – Accelerator Design – VTX detector design – IR design and backgrounds II) Present results and Activities – Radiation hardness – Spatial resolution – Fast readout electronics Summary

Accelerator Design 6mrad crab crossing Beam time Structure Bunch-train Structure Train = One pulse192 bunches 1.4ns N~1E+10 particles 1/150Hz=6.7ms Beam profile at IP 243nm 3.0nm dz=110um I )

VTX Design VTX – Precise Secondary vertex reconstruction Reconstruct decay vertices of B and D meson decays with excellent b/c jet separation – Improvement of momentum resolution Requirements – Unambiguous 2D reconstruction at high hit density Pixel devices Expected occupancy in a 20  m x 5cm s trip detector ～ 100% !, for hit background rate of about 1hit/mm 2 /train. – Less materials (Especially for low momentum tracks) Thin devices Operation at room temperature ~ 0 C -> Simple structure/Easy operation -> Less thermal distortion of wafers o

Room temperature operation CCDs – Features Thin/Low-density material Low power consumption But Needs cooling ? – w/o Cooling system Avoid multiple scattering by cooling system Avoid thermal distortion of sensors ( fabrication – operation temperature discrepancy) Desirable to operate in room temperature ~ 0 C ) Back-illumination CCD : HPK S7170 Thickness ~20  m CCD Flatness o

VTX detector design Baseline design – |cos | < 0.90 – Pixel size 25 um – 1.25cm x 5cm x330um – 4Layers with 10deg tilt ( r=24,36,48,60 mm) ( Ladder 16/24/32/40) (Sensor 2/3/4/5) – Intrinsic resolution 4  m (Just for a Simulation input )

IR Design and Background Model d) 3T with SC-QC1 QC1 : Super Conducting magnet L* = 4.3 m To reduce back scattering background produced by the interaction at QC1 R=8~16.5cm

Background estimation Beam-Beam Interaction – e + e - pair production – Beamstrahlung Secondary produced backgrounds R (mm) TRC(X) 3T * Preliminary R (mm) JLC-A ** JLC- Y** Model b) VTX VTX VTX VTX *Geant4 ( SR/PhotoNuclear ) Include solenoid ( uniform 3T ) +QC1 ( Ideal gradient ) Electron backgrounds ( /mm 2 /train) **Geant3 95bunches Low Lum. Similar to TRC(X) NLC - JLC Neutrons Previous Study 1E+9/cm 2 /Yr (Beamstrahlung) 1Yr operation e + e - pair ~1hit/mm 2 /train 1.5E+11/cm 2 /Yr

Present results and Activities Radiation hardness Spatial resolution Fast readout electronics II)

Radiation hardness HPK10 notch EEV TypeS5466CCD02-06 Pixel size [  m] 2422 R/O clock2-phase3-pahse Epitaxial layer[  m] 1020 Notchnone 3m3m MPP Operation Inverted by holes Si0 2 – Si Interface Small packet Notch CCD 2-Phase CCD 3-Phase CCD Low density

CCD Structure [cont’d] Result > 1.5E+11e/cm 2 JLC: 1.5E+11/cm 2 Result > 1.5E+10 n/cm 2 JLC: 1E+9/cm 2 /Yr (Preliminary) Radiation hardness V ee ( V ) Dark current (electrons/pix) Electrons from 90 SrNeutrons from 252 Cf HPK10

Radiation hardness [cont’d] MethodsVCTI improvement 3-phase to 2-phase ~2.5 times Std to notch structure ~3 or 4 times CTI properties 3Phase 2Phase Std CTI Notch VCTI ( Irradiation ) CTI ( Irradiation ) Electron Neutron HPK10 CTI~N t /N s Concentration N t : Defect N s : Signal

Radiation test -1- Our tests showed “Lifetime of CCD > 1Year ! Why additional test of radiation damage, then ? Non-Ionizing Energy Loss Radiation damage is thought to be proportional to NIEL The radiation damage at JLC estimated to be 10 times bigger than our study using 90 Sr. Radiation damage by high energy (>10MeV) electrons should be studied.

Radiation test -1- [cont’d] Non-Ionizing Energy Loss Radiation damage by high energy (>10MeV) electrons should be studied.

Radiation test (First trial 2002/12/9) Experimental setup Electron Beam 150 MeV Pt 0.1X 0 0.5X 0 Bending Magnet Choice of Settings 1)Primary Beam Energy 150MeV electrons 2)Target radiation length 0.1/0.5 X 0 3)B field High/Low Tesla mode Tohoku-Univ. Lab. of Nuclear Science

Radiation test [cont’d] Plan “Trial Run” -> Real Run in May?, Study of CsI(pure) calorimeter 2. Energy of electrons On target ; 150 MeV On CCD ; 100 MeV Irradiation: 5x10 10 /cm 2 Dosimetry; RadFET

Radiation test [cont’d] Energy distribution of the scattered electrons Incident electrons: 125 MeV/c

Radiation test [cont’d] 3. Cryogenic measuring system for CCD - almost same as the one which Stefanov-san used in Japan Cryostat Temperature Controller CCD Board inside the cryostat

Spatial resolution -Test beam- S/N > Dark current is suppressed by the successful Operation of Inverted mode. Noises in a pixel (R/O cycle ~ 3sec. ) HPK10(23e)/ HPK50(58e) / EEV(37e) HPK50 : HPK with epitaxial layer of 50  m 4-Layers CCD Tracker

Spatial resolution Temp.( C ) MethodHPK10HPK50EEV -15 CAC RLM CAC RLM RLM : RLM function AC : Analog centered Pmax P R = Pixel A Pixel B Signal of Pixel A Signal of Pixel B o

Spatial resolution [cont’d] Intrinsic Resolution Is better than 3  m. Intrinsic Resolution Is better than 3  m. Thermal diffusion of signal charge improves resolution.

Comparison with simulation - by T. Aso Energy deposit(keV) Thickness of active layer(  m) Geant4:Energy Deposit 2GeV,π ‐ HPK keV 7×7cls HPK10 2.2keV 2×2cls Energy Deposit in Silicon Estimated Active layer 11  m for HPK10 51  m for HPK50 ActiveLayer 51.1  m 11.0  m

HPK10 HPK50 Charge sharing simulation - by T. Aso ＋： d/A=50% × ： d/A=30% ＊： d/A=20% △： d/A=10% □ ： d/A=5% Depletion (d) Field Free (f) Active(A=d+f) XX Log(R)  d ~ sqrt(2Dt ) f ~ G.R.Hopkinson NIM A216(1983)432 Energy(keV) N×N Clustering HPK50 HPK10 Open ： Exp Close ： Sim Drift coff. *Drift Time

Electronics fabrication Readout operation – All pixels must be readout every train crossing interval of 6.7 ms, in the real experiment at JLC. – 10MHz readout can transfer about 250x250pix in the interval. 5cm 1.25cm 250x250pix/chip 16chips/sensor Total 424 sensors 6784 chips needed.

Fast R/O System -1- Features Fast Not expensive Low power Flexible design Optical link LVDS link 1st 2ndFinal

Fast R/O System -2- Evaluation board of ADC – CCD Signal processor chip for Digital Camera 9x9mm 2 chip size ~ $6/chip – AD9844A(Analog Devices Co.) 12bit 20MSPS ADC 20MSPS Correlated Double Sampler 6bit variable CDS Gain Amp. Low power consumption(65mW/2.7V) SHP SHD FADC

Fast R/O System -3- LVDS Inputs for clocks etc XC2V404CS144C(FPGA) AD9844A[FADC] Backside Interface to Digital board (12 bit DBUS] Linearity was confirmed. LSB resolution 0.2mV. Dynamic range 0~800mV

Summary Design and status of JLC VTX detector is presented. Goal --- CCD operation at room temperature Radiation hardness : No problem, so far. –But, further investigation is necessary. Electrons => Higher energy must be confirmed experimentally. ( Additional experiments are going. ) Neutrons => Yield of neutron is ambiguous ( beam dump ) ( Reliable simulation with precise geometry, JUPITER) Spatial resolution : < 3  m at -15 C. –More investigation of charge sharing property improve resolution? ( Laser scanner test at Niigata Univ. with 2x2  m spot.) Readout Electronics: Evaluating –Study the effect of Fast readout for irradiated samples Evaluation of thinned device –Partially thinned CCD..(Distortion measurement system: ready) o

CCM CCD (1) CCM (Charge carrier multiplier) – Multiply generated charge using Impact ionization Multiplying generated charge directly in the charge domain before conversion into a voltage High-field region between the two neighboring gates Gained energy is dissipated through Impact Ionization [II] Small variance in the II

CCM CCD(2) Difficult to reduce the noise floor of existing charge detection amplifiers particularly at high clocking freq.

CCM CCD(3) –IMPACTRON- IMPACTRON – Texas Instruments – TC253SPD – 658(H)x496(V)A pix. In Image Sensing Area – 7.4  m Square Pixels – Charge multiplication gain 1~30 – Charge conversion gain w/o CCM 10  V/e – Epitaxtial Layer depth? CCM (400pix) Charge Multiplication!!!

CCM CCD (4) –IMPACTRON- Gamma ray spectrum 55 Fe 0 o C Driver for Impactron is now being developed. ↓ Will be compared with HPK S5466