1. MICE Collaboration MTG IIT – Feb 2002 The Fiber Tracker Option for MICE Spectrometers The D0 Central Fiber Tracker – Experience and Implications for MICE A. Bross Fermilab

2. MICE Collaboration MTG IIT – Feb 2002 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 u 600 fibers/layer X 2 layers/doublet X 2/3 measurements (x&y or u-v-t) X 2 (stations) X 2 (up/downstream) yields s 9600 channels (x-y) s 14,400 channels (u-v-t)  Expect  m point-set resolution extrapolated from D0 results (90 mm) with 835  m fiber  This would require 10-14 D0-type VLPC cassettes u Basically all D0 spares  However, IF BACKGROUNDS ARE LOW – 4:1 multiplexing possible with 1 mm D0 pixel  Tremendous Premium in lowering backgrounds

3. MICE Collaboration MTG IIT – Feb 2002 D0 Central Fiber Tracker  8 layers u Outer 6 s 2.52 m u Inner 2 s 1.66 m  r -.2 to.51 m  Axial readout to south  VLPC Readout u 77,000 channels  Waveguide system u 8-11.5 m u “Pipes” light from detector to VLPCs

4. MICE Collaboration MTG IIT – Feb 2002 Central Fiber Tracker Channel Mirror Scintillating Fiber Optical connector Waveguide VLPC cassette Electronics Cryostat

5. MICE Collaboration MTG IIT – Feb 2002 Scintillating Fiber Ribbons  Interlocking doublet  835  m 3HF scintillating fiber u Fluorescence 525 nm (peak) to 610 nm  Grooved substrate - machined Delrin  Pitch between 915 and 990  m  Substrate put into curved backbone u Fibers glued together with polyurethane adhesive  Ribbons is then QC’ed using scanning X-ray source  Technique is very fast  All MICE planes require  4 MM effort + Tooling

6. MICE Collaboration MTG IIT – Feb 2002 CFT Tracker Mechanical Global precision » 33  m (Measured vs Desired)

7. MICE Collaboration MTG IIT – Feb 2002 Fiber Tracker Status

8. MICE Collaboration MTG IIT – Feb 2002  Waveguide bundles consist of 256 fibers in light-tight nylon sheath u Curved connector (256 ch.) at detector u 2 128 ch. Connector at cassette end Waveguide Bundle Fabrication and Routing

9. MICE Collaboration MTG IIT – Feb 2002 CFT Waveguide Routing  Routing, strain relief, etc for CFT (+CPS)

10. MICE Collaboration MTG IIT – Feb 2002 Fiber Tracker Status  South (Axial) side complete

11. MICE Collaboration MTG IIT – Feb 2002 CFT - Readout System  VLPC (Visible Light Photon Counter) u Cryogenic APD operating @ 9K  Characterization/test/s ort Cassette Assignment u As shown

12. MICE Collaboration MTG IIT – Feb 2002 VLPCs  VLPC  HISTE VI  High QE  80%  Low noise <5X10 4 Hz (@  1.0 pe) u High Rate capability s >40 MHz u High production yield   70% (vs. 27% projected)

13. MICE Collaboration MTG IIT – Feb 2002 1024 Channel VLPC Cassettes  Engineering Design u 8 – 128 channel modules u Cassette carries two 512 ch readout boards s Front-end amp/discriminator s Analog – SVX IIe 3’3’

14. MICE Collaboration MTG IIT – Feb 2002 CFT - Readout III  Cassette Performance u Noise low u Good uniformity

15. MICE Collaboration MTG IIT – Feb 2002 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. MICE Collaboration MTG IIT – Feb 2002 CFT: System Performance Read-out Platform: Waveguides and VLPCs Pulse Height ~14.5 pe Abid Patwa Como-Italy 2001

17. MICE Collaboration MTG IIT – Feb 2002 Lab 3 CRT (Singlet) Light Yield Lab 3 CRT Light Yield Summary Covers Waveguide lengths 7.7-11.4m

18. MICE Collaboration MTG IIT – Feb 2002 First Events of Run II  Tracking in the CFT is working although we still have a long way to go to fully optimize u Alignment u VLPC operating point optimization u Threshold setting u Etc….

19. MICE Collaboration MTG IIT – Feb 2002 MICE Fiber Tracker  Could envision a single VLPC cryostat reading out both up and downstream spectrometers u If multiplexing was an option s D0 test cryostat can hold required number of channels  Waveguide length about 5 m u Yield with VLPCs   [exp(-5/8)]/[exp(-11.4/8)]X7  pe  However u This assumes multiplexing s 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 Collaboration MTG IIT – Feb 2002 MICE Fiber Tracker  Conventional FT using MAPMT  With same length of readout fiber u If waveguides are used   430 nm = 1300 dB/km (1/e = 3.4m)   525  nm = 450 dB/km (1/e = 9.6m) –D0 measured 8.1m @ f p = 525 nm u QE = 20% u Yield = s 16 X 20/80 X exp(-5/3.4)/exp(-5/8)   2 pe  Effective tracking can likely be done @ 2 pe, but would be more difficult u Depends on backgrounds u Minimum acceptable waveguide length Attenuation vs. wavelength of Kuraray clear fiber 3 HF Conventional Blue

21. MICE Collaboration MTG IIT – Feb 2002 Conclusions  A Fiber tracker is an attractive option for MICE u Material presented to beam acceptable s As small as 0.15% RL per doublet (smaller if can multiplex – channel count)  Excellent resolution (<50  m)  High light yield  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