t0 status1w.h.trzaska hip jyväskylä status of t0 project alice comprehensive review iv march 23,...

T0 status 1W.H.Trzaska HIP Jyväskylä

Status of T0 project

ALICE Comprehensive Review IV

March 23, 2004


The main physics objectives

• Precise start signal for TOF– (does not have to be on-line)

• Trigger functions (on-line): – Rough vertex position

– Rough multiplicity (V0 backup)

– vertex-independent interaction time

• “wake-up” signal to TRD


Design considerations • detectors on both sides of the interaction point• compact design (minimal space on RB 26 side)• time resolution of about 50 ps;• position resolution (along the beam direction) 1 cm;• laser calibration system• total dead time of less than 25 ns (40 MHz BC);• operation in the magnetic field of up to 0.5 Tesla;• radiation hardness up to 500 krad;• reasonable multiplicity resolution for charged particles;• high reliability & maintenance-free operation.


Detector choice Cherenkov radiator + PMT

• 2 x 12 PMT units• Choice of PMT models and manufacturers:

– Hamamatsu R5506 (Japan)• Considerably more expensive (–)• No direct link to the production plant (–)• No possibility to “hand-pick” the tubes (–) • Well-established company (+)

– Electron FEU-187 (Russia)• Same performance (+)• Full compatibility with R5506 (if needed) (+)• Slightly larger diameter (+)

Our choice


Radiator choice & length

• Possible materials (good timing, UV transparent)– Acrylic (Lucite)

• Prone to radiation damage (above 100 krad)

– Quartz• Heavier (0.25 X0 / 0.1 X0 for 3 cm quartz / Lucite)

• Calculated radiator length 3 cm– Cherenkov light emission band is 200 - 550 nm

– Nph = 2(1/2 - 1/1) sin2 (per cm length)

– n = 1.458 cos = 1/n = 0.686 sin2 = 0.53– average quantum efficiency of the photo cathode =15%

Our choice

Our choice


Radiator’s diameter – not yet fixed• 3.0 cm – matches the outside diameter of PMT

– Higher efficiency in p-p collisions (+)– Slightly more material (–)– Little worse time resolution (edge effects) (–)

• 2.5 cm – matches the size of the photo cathode– Improved time resolution (to be measured) (+)– Less material (1/1.44) (+)– Reduced efficiency for p-p (–)

• 3.0 cm – T0-R 67% : T0-L 60% : R&L 48%• 2.5 cm – T0-R 47% : T0-L 42% : R&L 23%

• Will be determined experimentally June 2004


Latency questions• Latency of time signal from T0-Right to the rack

– IP PMT 70 cm @ 30 cm/ns = 2 ns

– Delay inside PMT = ~15 ns

– Delay on 25 m of cable (5ns/m) = 125 ns

– Fast Signal Processing (stage I) = ~45 ns

– T0 Vertex (FSP stage II) = ~43 ns

sub TOTAL (trigger) = 230 nsT0 Rack TRD (20m?) + 100 ns

Not acceptable! = 330 ns

• To provide TRD wake-up call T0 shoeboxes will be inside the magnet! fixed


Cable layout & length

Too far out!

Accessibility of the shoeboxes!

T0-Right

shoebox


G=-5

G=-5

From Cerenkovdetector

To t0 crates

G=1

<Doc> <RevCode>

<Title>

A

1 1Friday, March 12, 2004

Title

Size Document Number Rev

Date: Sheet of

To t0 crates

To TRDWake-upUnit

G=1

G=-5

Quiescent Current +6 V --- 80 mA Max Current +6 V --- 250 mA

-6 V --- 80 mA -6 V --- 250 mA

Amplifier-Transmitter Based on Op-Amp OPA695 - 1400 MHz bandwidth, 4300 V/us slew rate.

Inside the shoebox:


Left Shoe-box Right Shoe-box

Left t0 detection system - 12 Cerenkov detectors Right t0 detection system - 12 Cerenkov detectors

TRD Wake-up Unit

12 Amplifier-Transmitters

PowerConsumption: Quiescent: +6V, 1A

-6V, 1A

Max: +6V, 3A

-6V, 3A

12 Amplifier-Transmitters + TRD WU

24 cables

24 cables

12 cables


T0 + TRD Combined shoebox

preliminary


T0 data flow challenge

• 24 PMTs (2 Ampl. + 2 Time) + N = 100 parameters@ 40 MHz (BC rate in pp):

25 ns dead time required! • Dead time for all triggering functions is 25 ns

no loss of trigger pulses (guarantied!) • To provide also the readout system with 25 ns dead time

is not trivial (corresponds to several Gb/sec of dataflow)– It is possible with the existing hardware by using 16-fold

demultiplexer (16 more hardware)

– Is it really needed?


T0 data readout options• T0 will use TOF readout

– TOF is the main and by so far the only detector that needs non-trigger data from T0

– amplitude from T0 PMTs will be converted to time log(Amplitude) Time

• There are 2 possible options:– With 16 demultiplexer (dead time 25 ns)

ready for data readout within 25 ns of the previous data 16 hardware; guarantied digitisation of all data

– Without demultiplexer (dead time 400 ns) Small percentage of the trigger events will lack the

digitised amplitudes and times of PMT pulses


Strobe options (without demultiplexer)

• No strobe– If any of the T0 PMTs fires within BC it will be send

to the readout and block it for the duration of about 250 ns

– Some “important” trigger events may not be digitised

• T0 vertex strobe– Readout only if T0 vertex generated– All “important” trigger events digitised– All “unimportant” trigger events are not digitised

Digital Variable Attenuator DA-100-3S-830-9/125-M-35

Laser Calibration System

Picosecond Injection Laser PIL040G, 408 nm

Splitter

FOBS-12-333-SSS-400-50/50

RS232

12 fibers to Cerenkov detectors 12 fibers to Cerenkov detectors

MM patchcord

SM patchcords SM patchcords

T0 rack

Start

66/34

4 spare

50/50

25%75% of laser power100% of laser power


Key electronics modules of T0• Mean Timer – produces on-line timing signal

indicating accurate interaction time T0 = ½ (TLEFT + TRIGHT)

• T0 Vertex – gives an on-line ON/OFF signal indicating location of the vertex within the given limits. Selectable range 70 cm; accuracy 1 cm; dead time < 25 ns

• Fast Front-End electronics – amplifier + CFD stage to produce high quality time and amplitude signals for on- and off-line processing. Must be capable to handle very large dynamic range (about 1:500)


T0 Mean Timer performance

Generated mean time signal remained perfectly constant within our measurement accuracy: 0 10 ps

T0 Mean Timer

-500

-300

-100

100

300

500

0 5 10 15

Relative Distance from Vertex [cm]

Tim

e S

hif

t [p

s]

PMT1

PMT2

Mean Timer

Expected


T0 Vertex ModuleResolutionfwhm = 3 cm = 1.3 cm

Range 88cm7mm(23ps)/step

256 steps

Eff. = 98%

Profile doesn’t depend on

the threshold value

T0 vertex module

0

50

100

-10 0 10

Vertex position [cm]

Ver

tex

sig

nal

eff

icie

ncy

[%

]

High Threshold

Low Threshold


We could not test in the full dynamic range!

T0 time resolution (with PS particles)

• TOF FWHM=124 ps

= 37 psMeasuredTOF

spectrum


T0 MilestonesDate MilestoneMay 2004 Laser calibration I

June 2004 TDR text completed

June 2004 Test run at CERN

July 2004 Integration test

August 2004 T0 Technical Project I

September 2004 Final cabling inside L3

September 2004 TDR in print

October 2004 Quartz radiators production

November 2004 Purchase of PMTs

December 2004 Laser calibration II

September 2005 T0-R & T0-L assembled

October 2005 Pre-shipment tests

November 2005 T0 shipped to CERN

December 2005 Final tests

March 2006 T0 installation

t0 status1w.h.trzaska hip jyväskylä status of t0 project alice comprehensive review iv march 23,...

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