Long Shaping-time Silicon Readout Bruce Schumm UC Santa Cruz Arlington Linear Collider Workshop January

Participants Dave Dorfan, Christian Flacco, Alex Grillo, Hartmut Sadrozinski, Bruce Schumm, Abe Seiden, Ned Spencer, Lan Zhang Also, a new post-doc (Gavin Nesom) will probably join the effort in February Potential external associates: SLAC, LPNHE Paris, CERN RD50

Motivation Use of long shaping-time read- out (low noise) plus exploitation of duty cycle permits development of very long, thin ladders Additionally, limited readout and servicing may lead to very limited material budget in forward region (down to 100 mrad)

Scope and Funding Work funded via a two-year, $90,000 grant from the DOE Advanced Detector R&D Program (Will need to enter regular LC funding game afterwards) 9 months graduate student support Chip fabrication Long-ladder development (existing sensors) Electronics servicing to ladder

Detailed Scope Given the duration and magnitude of the support, our `deliverables’ will be Characterization of analog characteristics of 0.25 micron structures Development of pulse development and electronic simulation for shaping-time and readout- scheme optimization Demonstration of noise level commensurate with readout of 2m ladder Demonstration of x100 suppression of IR heating loss Min-i readout of 2m ladder

Pulse Development Simulation Questions to be answered: Sensor geometry and analog resolution required to achieve <7 um resolution Effect of large magnetic fields Effects of oblique angles of incidence Optimal detector bias

Pulse Dev Sim Cont’d Effects considered so far: Landau fluctuations (SS_SIMSIDE, Jerry Lynch, LBNL) Electron diffusion Lorentz angle Space-charge repulsion

Long Shaping-time Bail-out Much of pulse simulation effort goes into `weighting- field’ calculation (pulse-development Green’s Fnc) However, integral of total charge is e if electron hits strip 0 if electron misses strip In  --> infinity limit, this is all you need to worry about!

Electron Diffusion Electron diffusion distribution given by with diffusion constant given by Effect of B field?

Space-charge Effects Model deposition as uniform line of charge of radius  and linear charge density. After separation of electrons, holes, distribution expands conformally:

Other Simulation Aspects For now, assume mobilizing field that of plane-biased diode (obscures details of field near strips) Variable inputs: Detector geometry (pitch, thickness) Magnetic field Track parameters Detector bias

Potential Associations Aurore Savoy-Navarro (LPNHE Paris) Have discussed development of full-scale ladder, readout for testbeam run RD-50 (CERN, Mara Bruzzi) Standing request for expert consultation (Lorentz angle, diffusion and mobility vs. B, etc.) Possible exploration of `Czochralski’ sensors (large area, but leakage current needs work for now)

Next Six Months Immediately: begin SPICE-level optimization of shaping time (assuming 1-2 meter ladder) Have already begun qualifying GLAST 8-channel `cutoff’ structures for use in 2m ladder March: begin mechanical design and construction of two-meter ladder Submission of prototype ASIC in June

Longer Term NOTE: Project funded from DOE ADR program through 2003; afterwards, will need to switch to nominal sources! Summer 2003: measure noise and power consumption characteristics Fall 2003 (likely): begin design of 2 nd prototype chip based on accumulated experience Winter 2004: begin development of realistic prototype ladder, prepare for testbeam run Summer 2004: testbeam studies; begin to develop scheme for back-end architecture