Outline - University of Houston
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Transcript Outline - University of Houston
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 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
8 nested cylinders
– radius = 20 51 cm
Each layer
– 1 axial doublet
– 1 stereo (u or v)
xu - xv - xu - xv - ….
Constant angle =3o
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 mm 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 mm 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
Single Element of Scintillating Fiber Tracker
Scintillating Fiber
Optical Connector
Mirror
Waveguide Fiber
Electrical Signal Out
Photodetector Cassette
Cryostat
Key Features of the CFT
Scintillation
dyes - 1% PTP + 1500 PPM of 3HF
Fiber construction - 830 mm 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
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
1987 published paper on SSPM Solid State PhotoMultipliers
– 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
A
C
A
B
B
A = VLPC die
B = Aluminum Nitride substrate
C = Solder preform
1
mm pixels
2x4 array (HISTE-VI)
VLPC Cassette and Readout
1024 VLPC pixels in one cassette
Electronic readout:
– custom SVXII chips
SVX Readout (AD C Counts) of Cassette A (T =8.2K , V=7V)
600
500
3’
400
300
200
100
0
40
60
80 100 120 140 160 180 200
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 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 PT > 1.5 GeV/c
(4) Send out the track information to outside L1 CFT
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
Thin Flexible
Jig Plate
Curved Back
Plate
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 )
18
16
14
12
10
8
6
4
2
0
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
mm level - spec 25 mm
CFT Ribbon Mounting
CFT Ribbon Mounting
CFT Ribbon Mounting
Ribbon Mounting
Cylinder 3B completed - 30 ribbons total
36 m 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
LEDs
Each
ribbon lit by up to 3 panels
– Redundancy
– Large dynamic range
Each
LED output is variable
Panels at both ends detector
Flat Panels
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
CFT Status - Tracker Mechanical
All axial layers, r and r (incl. correct.)
Mean
RMS
Constant
Mean
Sigma
3500
3000
2500
2000
0.3375E-05
0.1455E-02
2284.
0.2749E-04
0.1323E-02
1500
1000
500
0
-0.01 -0.008 -0.006 -0.004 -0.002
0.002 0.004 0.006 0.008 0.01
inc h
(r)measured - (r)predicted
Complete
4000
3500
3000
2500
2000
1500
1000
500
0
-0.02
0
Mean
RMS
Constant
Mean
Sigma
-0.015
-0.01
-0.005
0
0.005
(r)measured - (r)0
0.01
-0.6468E-03
0.2633E-02
2903.
-0.6892E-03
0.2527E-02
0.015
0.02
inc h
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
[8-11.5m]
– Connectorization
» At ND + Fermilab +IU
– QC with x-ray source at
Lab3
Expect
to complete
production in August
Fiber Tracker Layout
Axial doublet layers
on each of 8 cylinders
Alternate u or v stereo
layers on successive
cylinders
~ 78k total channels