The Fiber Tracker Option for MICE Spectrometers

1
The Fiber Tracker Option for MICE Spectrometers

• The D0 Central Fiber Tracker
• Experience and Implications for MICE
• A. Bross
• Fermilab

2
Fiber Tracker Option for MICE

• In its simplest implementation, a FT for MICE
  could consist of two upstream and two downstream
  x-y tracking planes (assumes no or low
  background!) u-v-t option gives more redundancy
• With 500 micron round fiber and a fiber doublet
  structure (detail later) 30 cm active width
• 600 fibers/layer X 2 layers/doublet X 2/3
  measurements (xy or u-v-t) X 2 (stations) X 2
  (up/downstream) yields
• 9600 channels (x-y)
• 14,400 channels (u-v-t)
• Expect 40 mm point-set resolution extrapolated
  from D0 results (90 mm) with 835 mm fiber
• This would require 10-14 D0-type VLPC cassettes
• Basically all D0 spares
• However, IF BACKGROUNDS ARE LOW 41
  multiplexing possible with 1 mm D0 pixel
• Tremendous Premium in lowering backgrounds

3
D0 Central Fiber Tracker

• 8 layers
• Outer 6
• 2.52 m
• Inner 2
• 1.66 m
• r - .2 to .51 m
• Axial readout to south
• VLPC Readout
• 77,000 channels
• Waveguide system
• 8-11.5 m
• Pipes light from detector to VLPCs

4
Central Fiber Tracker Channel
Optical connector
Mirror
Scintillating Fiber
Waveguide
VLPC cassette
Electronics
Cryostat
5
Scintillating Fiber Ribbons

• Interlocking doublet
• 835 mm 3HF scintillating fiber
• Fluorescence 525 nm (peak) to 610 nm
• Grooved substrate - machined Delrin
• Pitch between 915 and 990 mm
• Substrate put into curved backbone
• Fibers glued together with polyurethane adhesive
• Ribbons is then QCed using scanning X-ray source
• Technique is very fast
• All MICE planes require 4 MM effort Tooling

6
CFT Tracker Mechanical
Global precision 33 mm (Measured vs Desired)
7
Fiber Tracker Status
8
Waveguide Bundle Fabrication and Routing

• Waveguide bundles consist of 256 fibers in
  light-tight nylon sheath
• Curved connector (256 ch.) at detector
• 2 128 ch. Connector at cassette end

9
CFT Waveguide Routing

• Routing, strain relief, etc for CFT (CPS)

10
Fiber Tracker Status

• South (Axial) side complete

11
CFT - Readout System

• VLPC (Visible Light Photon Counter)
• Cryogenic APD operating _at_ 9K
• Characterization/test/sort Cassette Assignment
• As shown

12
VLPCs

• VLPC HISTE VI
• High QE 80
• Low noise lt5X104 Hz (_at_1.0 pe)
• High Rate capability
• gt40 MHz
• High production yield
• 70
• (vs. 27 projected)

13
1024 Channel VLPC Cassettes

• Engineering Design
• 8 128 channel modules
• Cassette carries two 512 ch readout boards
• Front-end amp/discriminator
• Analog SVX IIe

14
CFT - Readout III

• Cassette Performance
• Noise low
• Good uniformity

15
The VLPC Cryostats

• The VLPC cryostats at DØ accommodate up to 102
  cassettes.
• The full complement of 99 cassettes necessary to
  instrument D0 are installed on the platform.

16
CFT System Performance
14.5 pe
Pulse Height
Read-out Platform Waveguides and VLPCs
Abid Patwa Como-Italy 2001
17
Lab 3 CRT (Singlet) Light Yield
Lab 3 CRT Light Yield Summary Covers Waveguide
lengths 7.7-11.4m
18
First Events of Run II

• Tracking in the CFT is working although we still
  have a long way to go to fully optimize
• Alignment
• VLPC operating point optimization
• Threshold setting
• Etc.

19
MICE Fiber Tracker

• Could envision a single VLPC cryostat reading out
  both up and downstream spectrometers
• If multiplexing was an option
• D0 test cryostat can hold required number of
  channels
• Waveguide length about 5 m
• Yield with VLPCs
• Þ exp(-5/8)/exp(-11.4/8)X7 16pe
• However
• This assumes multiplexing
• 0.5 mm scintillating fiber coupled to 0.835 mm
  waveguide fiber
• Could use 1 mm fiber also and get small
  improvement

VLPC Cryostat
20
MICE Fiber Tracker

• Conventional FT using MAPMT
• With same length of readout fiber
• If waveguides are used
• L430 nm 1300 dB/km (1/e 3.4m)
• L525 nm 450 dB/km (1/e 9.6m)
• D0 measured 8.1m _at_ lfp 525 nm
• QE 20
• Yield
• 16 X 20/80 X exp(-5/3.4)/exp(-5/8)
• 2 pe
• Effective tracking can likely be done _at_ 2 pe, but
  would be more difficult
• Depends on backgrounds
• Minimum acceptable waveguide length

Attenuation vs. wavelength of Kuraray clear fiber
Conventional Blue
3 HF
21
Conclusions

• A Fiber tracker is an attractive option for MICE
• Material presented to beam acceptable
• As small as 0.15 RL per doublet (smaller if can
  multiplex channel count)
• Excellent resolution (lt50 mm)
• High light yield Þ efficient tracking possible
• VLPC (or other SS photodetector) has major
  advantage vz a vz light yield, but MAPMT can
  likely be made to work
• If backgrounds can be kept low, multiplexing can
  reduce channel count