Main Injector at Fermilab

Silicon Vertex Tracker Integrated system of barrels and disks ~ 800k total channels

Silicon Tracker Layout 1/7 of the detector (large-z disks not shown) 387k ch in 4-layer double sided Si barrel (stereo) 405k ch in interspersed disks (double sided stereo) and large-z disks

Silicon Tracker 7 barrels 50 cm 12 Disks “F”8 Disks“H” 3 1/2 of detector Silicon Tracking System

Central Fiber Tracker Layout u 8 nested cylinders –radius = 20  51 cm u Each layer –1 axial doublet –1 stereo (u or v) xu - xv - xu - xv - …. Constant angle   u Layers –1, m long –2, m long  Total channel count  u Clear fiber brings signal to VLPCs m

Why a Fiber Tracker? A SciFi Tracker provides the following features: u Fast response u Good granularity u Track triggering at Level 1 u High efficiency  Accurate r  position measurement u Compact design u Seamless coverage

A Little History  Snowmass Binnie, Kirkby, Ruchti propose inner tracker for SSC based on 25  m scintillating glass fibers. II + CCD readout u CERN, Wood (and the rest of UA2) run with SFD, 60,000 1mm plastic fibers with II + CCD readout u FNAL, Reucroft and Ruchti co-chair workshop on SciFi detector development for the SSC u CERN, ?? - Taylor (and the rest of L3) run with PSF detector to calibrate the TEC. 3,600 plastic fibers coupled to MCP phototubes u Snowmass A scintillating fiber outer tracker is proposed for the DØ upgrade at the Tevatron u Notre Dame Tests of Kuraray fiber doped with PTP+3HF and read out by a VLPC demonstrate sufficient light yield for fiber tracking u FNAL, A 3,000 channel cosmic ray test of scintillating fibers read out by VLPCs measures high light yield, good position resolution and long-term stability of the VLPC system

A Little History  Snowmass Binnie, Kirkby, Ruchti propose inner tracker for SSC based on 25  m scintillating glass fibers. II + CCD readout u CERN, UA2 runs with SFD. 60,000 1mm plastic fibers with II + CCD readout u CERN, L3 runs with PSF detector to calibrate the TEC. 3,600 plastic fibers coupled to MCP phototubes u Snowmass A scintillating fiber outer tracker is proposed for the DØ upgrade at the Tevatron u Notre Dame Tests of Kuraray fiber doped with PTP+3HF and read out by a VLPC demonstrate sufficient light yield for fiber tracking u FNAL, A 3,000 channel cosmic ray test of scintillating fibers read out by VLPCs measures high light yield, good position resolution and long-term stability of the VLPC system

Single Element of Scintillating Fiber Tracker

Key Features of the CFT u Scintillation dyes - 1% PTP PPM of 3HF  Fiber construction  m PS core, multiclad u Photodetectors - Visible Light Photon Counter u Fiber ribbon manufacture - grooved jig plate u Fiber ribbon placement - located with CMM u Fiber-to-fiber connectors - curved, grooved, diamond finished u Support cylinders - double-walled carbon fiber

Visible Light Photon Counters u Key features of the VLPC –Solid state detectors of photons, manufactured at Boeing (originated at Rockwell International) –Operate at the temperature of a few degrees Kelvin –Capable of detecting single photons –High quantum efficiency for photon detection ~80% –High gain ~ electrons per converted photon –Low gain dispersion –Can operate in a high background radiation environment –Used for CFT, CPS and FPS

VLPC Operation u Based on the phenomenon of Impurity Band Conduction, occurring when a semiconductor is heavily doped with shallow donors or acceptors –Electrical transport occurs by charges hopping from impurity site to impurity site u In the VLPC for DØ silicon heavily doped with arsenic atoms –Impurity band 0.05 eV below the conduction band –Normal 1.12 eV valence band used to absorb photons –The 0.05 eV gap used to create an electron-D + avalanche multiplication »Small gap means low field needed

D + flow E field Undoped Silicon Doped Silicon Layer + - Intrinsic Region Gain Region Drift Region Photon eh Spacer and Substrate VLPC Operation Cross Section Electric Field Distribution

VLPC Development History u 1987 published paper on SSPM Solid State Photo- Multipliers –sensitive into infra-red region u 1989 HISTE Proposal Submitted High-Resolution Scintillating Fiber Tracker Experiment –Main goal: to suppress sensitivity in infrared region u HISTE I, HISTE II, HISTE III u 1993 HISTE IV –Visible QE ~60%, Cosmic Ray Test at Fermilab u 1994 HISTE V High QE High Gain u HISTE VI large scale production based on HISTE V

HISTE-VI VLPC chip u 1 mm pixels u 2x4 array (HISTE-VI)

VLPC Cassette and Readout u 1024 VLPC pixels in one cassette u Electronic readout: –custom SVXII chips 3’

VLPC Production at Boeing u needed including 10% spares u tested u accepted –Yield: 87%

VLPC Performance Summary

Fiber Placement Inherent fiber doublet resolution is on the order of 100 microns Ô want to know fiber locations to < 50 microns However, for the Level 1 trigger must place fibers with a skew < 40 microns end-to-end Ô implications for ribbon fabrication, ribbon mounting and cylinder construction

CFT Track Trigger Trigger response for Z  ee with 4 min.bias (1) Fiber light signals  electronic signals (2) Feed all axial fibers into logic gates/cells in Programmable Logical Devices (3) Fiber hit pattern recognition to look for tracks consistent with momentum P T > 1.5 GeV/c (4) Send out the track information to outside L1 CFT

Fiber Ribbon Fabrication u Doublet ribbons of 2  128 fibers u Flexible grooved Delrin plate locates fibers u Aluminum curved back plate sets the radius u Same mold used for ribbon mounting

Fiber Ribbon Fabrication u Doublet ribbons of 2  128 fibers u Flexible grooved Delrin plate locates fibers u Aluminum curved back plate sets the radius u Same mold used for ribbon mounting

Fiber Ribbon Quality Control

Ribbon Quality Control

Ribbon Production

The problem with Torlon u During assembly of cylinder 3, interference between ribbon connectors observed u Torlon connectors had grown! –Humidity effect –Studies inconclusive, so … u Torlon has now been rejected –Barrels 7,8 will use aluminum connectors –Other barrels, either Al or Techtron

CFT Support Cylinders u Fabricated “in house” at Fermilab u Double wall design - carbon fiber walls with Rohacell core u Built up on precision steel mandrels

CFT Support Cylinders

Status - Ribbon Mounting u Ribbon Mounting machine/tooling complete u Test Ribbons have been mounted –Look good –Still need alignment correction (CMM) at 150  m level - spec 25  m

CFT Ribbon Mounting

Ribbon Mounting Cylinder 3B completed - 30 ribbons total 36  rms

Fiber Mapping and Routing Long clear waveguide bundles map 256 fibers from SciFi ribbon to 2  128 connectors at VLPC end  Bundles vary from 7-12 meters  Must be light-tight, flexible, narrow, flame retardant and “custom-shaped” at curved end  Mapping of axial fibers critical to trigger á Out of 300 bundles, nearly 100 are unique

Waveguide Fiber Routing

CFT Calibration Uses flat optical panel + LED to illuminate fibers from above. One panel for each of 300 ribbons. LED Flat Panel

Flat Optical Calibration Panels u 300 panels total in system u Panels are inexpensive, uniform, made to order Panel Uniformity

Calibration Mounting Scheme SciFi Ribbons Flat Panels LEDs u Each ribbon lit by up to 3 panels –Redundancy –Large dynamic range u Each LED output is variable u Panels at both ends detector

Status and Summary u DØ upgrade progressing - ready for physics in early 2001 u Central Fiber Tracker in production –fabrication complete in April 2000 –cabling completed in summer 2000 –Silicon tracker inserted in fall 2000 –commission with cosmic rays from summer 2000 until start of Run II

CFT Status - Waveguides –Fiber sorted »Best (attn.L from Kuraray) - longest runs [8-11.5m] –Connectorization »At ND + Fermilab +IU –QC with x-ray source at Lab3 u Expect to complete production in August

CFT Status - Tracker Mechanical Complete Global precision  33  m (Measured vs Desired)

Fiber Ribbon Quality Control

Ribbon Quality Control

CFT Moved to DAB

CFT Status - Waveguides –Fiber sorted »Best (attn.L from Kuraray) - longest runs [8-11.5m] –Connectorization »At ND + Fermilab +IU –QC with x-ray source at Lab3 u Expect to complete production in August

Fiber Tracker Layout u Axial doublet layers on each of 8 cylinders u Alternate u or v stereo layers on successive cylinders u ~ 78k total channels