Main Injector at Fermilab Silicon Vertex Tracker

Main Injector at Fermilab

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

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

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

Central Fiber Tracker Layout u u u 8 nested cylinders – radius = 20 ® 51 cm Each layer – 1 axial doublet – 1 stereo (u or v) xu - xv - …. Constant angle = 3 o Layers – 1, 2 - 1. 8 m long – 2, 8 - 2. 6 m long Total channel count » 77 K Clear fiber brings signal to VLPCs - 7 - 11 m

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

A Little History u u u u Snowmass 1984 - Binnie, Kirkby, Ruchti propose inner tracker for SSC based on 25 m scintillating glass fibers. II + CCD readout CERN, 1988 -1990 - Wood (and the rest of UA 2) run with SFD, 60, 000 1 mm plastic fibers with II + CCD readout FNAL, 1988 - Reucroft and Ruchti co-chair workshop on Sci. Fi detector development for the SSC CERN, 1989 - ? ? - Taylor (and the rest of L 3) run with PSF detector to calibrate the TEC. 3, 600 plastic fibers coupled to MCP phototubes Snowmass 1990 - A scintillating fiber outer tracker is proposed for the DØ upgrade at the Tevatron Notre Dame 1993 - Tests of Kuraray fiber doped with PTP+3 HF and read out by a VLPC demonstrate sufficient light yield for fiber tracking FNAL, 1994 -1995 - 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 u u u Snowmass 1984 - Binnie, Kirkby, Ruchti propose inner tracker for SSC based on 25 m scintillating glass fibers. II + CCD readout CERN, 1988 -1990 - UA 2 runs with SFD. 60, 000 1 mm plastic fibers with II + CCD readout CERN, 1989 - L 3 runs with PSF detector to calibrate the TEC. 3, 600 plastic fibers coupled to MCP phototubes Snowmass 1990 - A scintillating fiber outer tracker is proposed for the DØ upgrade at the Tevatron Notre Dame 1993 - Tests of Kuraray fiber doped with PTP+3 HF and read out by a VLPC demonstrate sufficient light yield for fiber tracking FNAL, 1994 -1995 - 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 + 1500 PPM of 3 HF u Fiber construction - 830 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 ~40 000 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 e. V below the conduction band – Normal 1. 12 e. V valence band used to absorb photons – The 0. 05 e. V gap used to create an electron-D+ avalanche multiplication » Small gap means low field needed

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

VLPC Development History u u u 1987 published paper on SSPM Solid State Photo. Multipliers – sensitive into infra-red region 1989 HISTE Proposal Submitted High-Resolution Scintillating Fiber Tracker Experiment – Main goal: to suppress sensitivity in infrared region 1991 -1992 HISTE I, HISTE III 1993 HISTE IV – Visible QE ~60%, Cosmic Ray Test at Fermilab 1994 HISTE V High QE High Gain HISTE VI large scale production based on HISTE V

HISTE-VI VLPC chip u 1 mm pixels u 2 x 4 array (HISTE-VI)

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

VLPC Production at Boeing u 13 300 needed including 10% spares u 17 845 tested u 15 529 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 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 PT > 1. 5 Ge. V/c (4) Send out the track information to outside L 1 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 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

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 3 B completed - 30 ribbons total 36 rms

Fiber Mapping and Routing Long clear waveguide bundles map 256 fibers from Sci. Fi 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 Sci. Fi Ribbons 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 Flat Panels

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. 5 m] – Connectorization » At ND + Fermilab +IU – QC with x-ray source at Lab 3 u Expect to complete production in August

CFT Status - Tracker Mechanical Complete Global precision » 33 mm (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. 5 m] – Connectorization » At ND + Fermilab +IU – QC with x-ray source at Lab 3 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 ~ 78 k total channels