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

1.1 1.7

Central Fiber Tracker Layout 8 nested cylinders

– radius = 20 51 cm Each layer

– 1 axial doublet– 1 stereo (u or v)

xu - xv - xu - xv - ….

Constant angle

Layers– 1,2 - 1.8 m long– 2,8 - 2.6 m long

Total channel count Clear fiber brings signal to

VLPCs - 7 - 11m

Why a Fiber Tracker?

A SciFi Tracker provides the following features:

Fast response Good granularity Track triggering at Level 1 High efficiency Accurate rposition measurement Compact design Seamless coverage

A Little History 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 UA2) run with SFD, 60,000 1mm

plastic fibers with II + CCD readout FNAL, 1988 - Reucroft and Ruchti co-chair workshop on SciFi detector

development for the SSC CERN, 1989 - ?? - Taylor (and the rest of L3) 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+3HF 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 Snowmass 1984 - Binnie, Kirkby, Ruchti propose inner tracker for SSC

based on 25 m scintillating glass fibers. II + CCD readout CERN, 1988-1990 - UA2 runs with SFD. 60,000 1mm plastic fibers with

II + CCD readout CERN, 1989 - L3 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+3HF 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

Scintillating FiberOptical Connector

Waveguide Fiber

Mirror

Photodetector CassetteElectrical Signal Out

Cryostat

Single Element of Scintillating Fiber Tracker

Key Features of the CFT

Scintillation dyes - 1% PTP + 1500 PPM of 3HF Fiber construction - 830 m PS core, multiclad Photodetectors - Visible Light Photon Counter Fiber ribbon manufacture - grooved jig plate Fiber ribbon placement - located with CMM Fiber-to-fiber connectors - curved, grooved,

diamond finished Support cylinders - double-walled carbon fiber

Visible Light Photon Counters

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 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

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

•+ •-

IntrinsicRegion

GainRegion

DriftRegion

Photon

•e •h

Spacer and

Substrate

VLPC Operation

Cross Section

Electric Field Distribution

VLPC Development History 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 II, 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

1 mm pixels 2x4 array (HISTE-VI)

B

A = VLPC die

B = Aluminum Nitride substrateC = Solder preform

A

A BC

VLPC Cassette and Readout 1024 VLPC pixels in one cassette Electronic readout:

– custom SVXII chips

SVX Readout (ADC Counts) of Cassette A (T=8.2K, V=7V)

0

100

200

300

400

500

600

40 60 80 100 120 140 160 180 200

3’

VLPC Production at Boeing

13 300 needed including 10% spares

17 845 tested 15 529 accepted

– Yield: 87%

VLPC Performance Summary

Fiber Placement

Inherent fiber doublet resolution is on the order of

100 microns 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 implications for ribbon fabrication, ribbon mounting

and cylinder construction

CFT Track TriggerTrigger 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 GeV/c

(4) Send out the track information to outside L1 CFT

Fiber Ribbon Fabrication

Curved Back Plate

Thin Flexible Jig Plate

Doublet ribbons of 2 128 fibers

Flexible grooved Delrin plate locates fibers

Aluminum curved back plate sets the radius

Same mold used for ribbon mounting

Fiber Ribbon Fabrication Doublet ribbons of 2

128 fibers Flexible grooved Delrin

plate locates fibers Aluminum curved back

plate sets the radius Same mold used for

ribbon mounting

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Fiber Ribbon Quality Control

Ribbon Quality Control

Ribbon Production

Weekly Ribbon Production ( 85% Overall Pass-Rate )

0

2

4

6

8

10

12

14

16

18

20-May 9-Jun 29-Jun 19-Jul 8-Aug 28-Aug 17-Sep

The problem with Torlon

During assembly of cylinder 3, interference between ribbon connectors observed

Torlon connectors had grown!– Humidity effect– Studies inconclusive, so …

Torlon has now been rejected– Barrels 7,8 will use aluminum connectors– Other barrels, either Al or Techtron

CFT Support Cylinders

Fabricated “in house” at Fermilab

Double wall design - carbon fiber walls with Rohacell core

Built up on precision steel mandrels

CFT Support Cylinders

CFT Support Cylinders

Status - Ribbon Mounting Ribbon Mounting

machine/tooling complete

Test Ribbons have been mounted – Look good

– Still need alignment correction (CMM) at 150 m level - spec 25 m

CFT Ribbon Mounting

CFT Ribbon Mounting

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

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

300 panels total in system Panels are inexpensive, uniform, made to order

Panel Uniformity

Calibration Mounting Scheme

SciFi Ribbons

Flat Panels

LEDs Each ribbon lit by up to 3 panels

– Redundancy

– Large dynamic range

Each LED output is variable Panels at both ends detector

Status and Summary

DØ upgrade progressing - ready for physics in early 2001

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 Expect to complete

production in August

(r)measured - (r)predicted

All axial layers, r and r (incl. correct.)

0

500

1000

1500

2000

2500

3000

3500

-0.01 -0.008 -0.006 -0.004 -0.002 0 0.002 0.004 0.006 0.008 0.01

MeanRMS

0.3375E-05 0.1455E-02

Constant 2284.Mean 0.2749E-04Sigma 0.1323E-02

inch

(r)measured - (r)0

0500

1000150020002500300035004000

-0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02

MeanRMS

-0.6468E-03 0.2633E-02

Constant 2903.Mean -0.6892E-03Sigma 0.2527E-02

inch

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 Expect to complete

production in August

Fiber Tracker LayoutFiber Tracker Layout

Axial doublet layers on each of 8 cylinders

Alternate u or v stereo layers on successive cylinders

~ 78k total channels