PHOBOS TOF Construction Status

A.B. Hayes, E.B. Johnson,

Robert Pak, R.T.D. Teng,

and F.L.H. Wolfs

University of Rochester

supported by NSF

TAC Review

Brookhaven Nat’l Lab

Nov. 6, 1998

Outline

Detector Configuration:

» Baseline

» TOF Upgrade Components & Assembly Support Structure Readout Electronics Summary

PHOBOS Baseline Design

Multiplicity Array:» Octagon Barrel» Vertex Detector» Ring Counters

Nearly 4coverage

( - 5.4 < < 5.4 ) Spectrometer Arms: Detailed measurement

of ptransverse down to

~ 40 MeV/c for pions.

TOF System Upgrade

Time-of-flight wall

Magnet support structure

Silicon planes

Interaction point

Ring muliplicity counters

Required performance:

» TOF < 100 ps

» Occupancy < 15%

Particle ID with PHOBOS

Baseline design relies solely on energy loss

PID based on dE/dx:» / K : p < 650 MeV/c

» K / p : p < 1.2 GeV/c

PID based on TOF (TOF =100 ps):» / K : p < 1.2 GeV/c» K / p : p < 2.0 GeV/c

1.7 m from interaction point

Physics Impact of PHOBOS TOF

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

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Pt

(G

eV/c

)

1.51.00.50.0

y

Time-of-Flight Identification

dE/dx Identification

+, -

Scintillators and Light Guides

Scintillators:» BC-404 fast plastic from Bicron» 8 x 8 x 200 mm3

» Diamond milled surface finish Light Guides:

» BC-800 acrylic dog-leg design » Machined at INP in Krakow

Photomultiplier Tubes & Bases

Hamamatsu R5900-00-M4MOD 12 stage multi-anode 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

Quality assurance done

Hamamatsu Gain Vs. Rochester Gain

0.00E+00

2.00E+06

4.00E+06

6.00E+06

8.00E+06

1.00E+07

1.20E+07

1.40E+07

1.60E+07

0.00E+00 5.00E+06 1.00E+07 1.50E+07 2.00E+07

Rochester Gain

Ham

am

ats

u G

ain

Assembly of components

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

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

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

470 nm (blue) LED from Panasonic (P465)

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

LED

Splitter

Fiber Bundle

PIN Diode

(To PMT’s)

LED Calibration System1 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 avalanchemode to discharge a capacitorthrough LED

Basic TOF Units

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

Crosstalk in PMT will not be a problem

TOF Support Structure

Final design of TOF support structure nearly complete AutoCAD picture courtesy of our collaborators at INP

Readout Electronics

Standard modules were chosen to reduce overhead from development of specialized electronics

LeCroy 1458 HV mainframe with ARCNET card sent to BNL for work on Slow Controls

Order placed with LeCroy for HV cards, FASTBUS ADCs and TDCs, and CAMAC discriminators

Cost of PHOBOS TOF Project

Total cost (proposal):

» NSF MRI Grant $328,129.00

» Cost sharing + 245,196.00

$573,325.00

--------------------------------------------------------------------- Actual current expenditures $475,346.80 Proposed current expenditures - 474,271.30

$1,075.50

Summary

Solid progress has been made on all fronts

for the PHOBOS TOF System at Rochester.

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