PHOBOS TOF Construction Status A B Hayes E

PHOBOS TOF Construction Status A. B. Hayes, E. B. Johnson, Robert Pak, R. T. D. Teng, and F. L. H. Wolfs l University of Rochester supported by NSF l TAC Review Brookhaven Nat’l Lab Nov. 6, 1998 Outline l l l Detector Configuration: » Baseline » TOF Upgrade Components & Assembly Support Structure Readout Electronics Summary

PHOBOS Baseline Design l Multiplicity Array: » Octagon Barrel » Vertex Detector » Ring Counters Nearly 4 coverage ( - 5. 4 < < 5. 4 ) l Spectrometer Arms: Detailed measurement of ptransverse down to ~ 40 Me. V/c for pions.

TOF System Upgrade l Required performance: » TOF < 100 ps » Occupancy < 15%

Particle ID with PHOBOS l l Baseline design relies solely on energy loss PID based on d. E/dx: » / K : p < 650 Me. V/c » K/p: l p < 1. 2 Ge. V/c PID based on TOF ( TOF = 100 ps): » / K : p < 1. 2 Ge. V/c » K / p : p < 2. 0 Ge. V/c 1. 7 m from interaction point

Physics Impact of PHOBOS TOF l l Spectral behavior of ptransverse distributions Extend pt region for and K interferometry Precise measurement of K/ ratios as a function of pt Study pt dependence of meson production

Scintillators and Light Guides l Scintillators: » BC-404 fast plastic from Bicron » 8 x 200 mm 3 » Diamond milled surface finish l Light Guides: » BC-800 acrylic dog-leg design » Machined at INP in Krakow

Photomultiplier Tubes & Bases l Hamamatsu R 5900 -00 M 4 MOD 12 stage multianode PMTs » Minimum gain per any one channel of 2 x 106 at +800 V » Maximum variation in gain (uniformity) is less than 50% per any one tube l Quality assurance done

Assembly of components l l Gluing of light guides to scintillators is completed Wrapping in reflective Al foil and first layer of protective tape is finished for all 240 detectors

Mounting Fixture l l l Must precisely align light guides with the face of the PMT Serve as gluing fixture for PMTs to light guides Machining at INP in Krakow is completed

Magnetic Shields l l l TOF detectors must operate unaffected by magnetic fringe fields of at least 100 G Prototype metal shield has been designed and tested in house Order completed through Perfection Mica

LED Calibration System l l 470 nm (blue) LED from Panasonic (P 465) Duplex fiber optic cables from Thomas & Betts carry pulses to each PMT Pulse width ~ 10 ns out of PMT (at +8 V) and bright enough to drive multiple PMT’s Light split between fibers and PIN diode reference Splitter PIN Diode LED Fiber Bundle (To PMT’s)

LED Calibration System 1 mm dia plastic fiber located in “dead-area” at center of PMT Upper-right light guide removed to show fiber NIM to TTL converter Pulser uses transistor in avalanche mode to discharge a capacitor through LED

Basic TOF Units l l Gluing of PMTs to light guides & fiber optics has begun Final assembly and testing of basic TOF units progressing well at Rochester (we’re under spec)

Benchtest: Crosstalk l Crosstalk in PMT will not be a problem

TOF Support Structure l l Final design of TOF support structure nearly complete Auto. CAD picture courtesy of our collaborators at INP

Readout Electronics l l l Standard modules were chosen to reduce overhead from development of specialized electronics Le. Croy 1458 HV mainframe with ARCNET card sent to BNL for work on Slow Controls Order placed with Le. Croy for HV cards, FASTBUS ADCs and TDCs, and CAMAC discriminators

Cost of PHOBOS TOF Project l Total cost (proposal): » NSF MRI Grant » Cost sharing $328, 129. 00 + 245, 196. 00 $573, 325. 00 ----------------------------------l Actual current expenditures $475, 346. 80 l Proposed current expenditures - 474, 271. 30 $1, 075. 50

Summary l Solid progress has been made on all fronts for the PHOBOS TOF System at Rochester. l The PHOBOS TOF System will be ready on Day 1 of Commissioning Run at RHIC. Stay tuned: http: //teacher. nsrl. rochester. edu/ Research/PHOBOS/Phobos. html l