FPCCD Vertex detector 22 Dec Y. Sugimoto KEK

Vertex detector for ILC Performance goal ： Impact parameter resolution;  IP = 5  10/(p  sin 3/2  )  m ( << c  of D,  ) This m.s. term is very challenging Very thin wafer, beam pipe, support Innermost layer as close to IP as possible  High b.g. rate  High pixel occupancy Track density (/cm 2 /BX)

Vertex detector options If signals of one train (2820 bunches) are accumulated, too many hits by beam b.g.  for 25  m pixels, the pixel occupancy >10% for B=3T and R=20mm Solutions; Fast readout : Example; Column Parallel 20 frames/train No time to wait for diffusion in epi-layer after particle incident  Fully depleted CCD  No diffusion  Poor resolution Still smaller pixel size is necessary to recover the resolution Possible effect by RF noise by beam Analog registers in each pixel (~20/pixel), and readout between trains CMOS: Flexible Active Pixel Sensor (FAPS) CCD: In-situ Storage Image Sensor (ISIS) Fine and complicated structure  Large area OK? Make pixel density x20  Fine Pixel CCD (FPCCD)

Vertex detector options Si Pixel Readout between trains Readout during train Fine pixel (x20 more pixels) Standard pixel (x20 time slice in 1 train) Standard pixel (x20 time slice in 1 train) FPCCD ISIS FAPS MAPS CPCCD DEPFET SOI

GLD Vertex detector FPCCD vertex detector as the baseline design of GLD Accumulate hit signals for one train (2840 BX) and read out between trains (200ms)  Completely free from EMI Fine pixel of ~5  m (x20 more pixels than “standard” pixels) to keep low pixel occupancy  Spatial resolution of ~1.5  m even with digital readout Fully depleted epitaxial layer to minimize the number of hit pixels due to charge spread by diffusion Two layers in proximity make a doublet (super layer) to minimize the wrong-tracking probability due to multiple scattering Three doublets (6 CCD layers) make the detector Tracking capability with single layer using hit cluster shape can help background rejection Multi-port readout with moderate (~20MHz) speed (Very fast readout (>50MHz) not necessary) Simpler structure than FAPS or ISIS  Large area No heat source in the image area

Standard CCD Fine Pixel CCD High Pt Signal Low Pt b.g. Z  B.G. rejection by hit cluster shape (tracking capability with single layer!)

Challenge of FPCCD Fully depleted Lorentz angle tan  =r H  B, r H : Hall coefficient~1,  : mobility (m 2 /Vs), B: Magnetic field (T) Stronger E-field in dep. layer (>10 4 V/cm = 1V/  m) gives saturation of carrier velocity and smaller   Epi layer of ~15  m would be OK Radiation tolerance Small pixel （ ~5  m) Fast readout speed （ ~20Mpix/s ） Multi-port readout H-Register in image area Low noise: <50 e (total)  < 30 e (CCD) Low power consumption Metal layer Low drive pulse voltage Output circuit Large area:10x65mm 2 （ in ） /20x100mm 2 （ out ） Thinning （ <50  m) Full well capacity >10 4 e is OK Readout ASIC Necessary for proto-type ladder

Lorentz angle tan  =r H  B~  B (  :m 2 /Vs, B:T),  =v/E  ~0.1 m 2 /Vs  ~0.07 m 2 /Vs  ~0.14 m 2 /Vs

R&D for FPCCD Study of fully depleted CCD Charge spread Lorentz angle Radiation damage Development of FPCCD 3 rounds expected Prototype ladder in 5 years Collaboration with Hamamatsu Minimization of material budget Wafer thinning FEA study of support structure Development of readout ASIC Supported by Gakujyutu Sousei

R&D Roadmap DCRDODLOI Construction Study of fully Depleted CCD Design of small Prototype of FPCCD FPCCD fabrication Sample test 2nd round3rd round (prototype ladder) Development of readout ASIC for prototype CCD Wafer thinning and the support structure Other 2nd priority R&Ds ILC Project (Detector) DOD: Detector Outline Document DCR: Detector Concept Report LOI: Letter of Intent (?) FPCCD VTX

Short term plan Study of fully depleted CCD New CCDs will be delivered mid December Epi-layer: 30  m / 15  m Pixel size: 24  m Study of charge spread and Lorentz angle Using green YAG LASER B-field up to 1T Radiation tolerance Electron / neutron damage Dark current / charge transfer inefficiency Study of support structure FEA study of Si-RVC-Si sandwich structure (RVC: Reticulated Vitreous Carbon)

Study of charge spread Apparatus CCD for reference (Front-illumination) CCD for test (Back-illumination)

Charge spread Front illumination Standard Back illumination Deep2

Field simulation N A =1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 x10 13 /cm 3

Summary We have started R&D of FPCCD for GLD vertex detector Study of fully depleted CCD is on going in FY2006, and will be continued to FY2007 The 1 st test sample of FPCCD is expected to be made by Hamamatsu in FY2007 We wish to construct and test prototype ladders of FPCCD by the end of Gakujyutu-Sousei project, but the budget (for r.o. ASIC and support structure) is not enough to complete that goal