t0 status1w.h.trzaska hip jyväskylä status of t0 project alice comprehensive review iv march 23,...
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T0 status 1W.H.Trzaska HIP Jyväskylä
Status of T0 project
ALICE Comprehensive Review IV
March 23, 2004
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T0 status 2W.H.Trzaska HIP Jyväskylä
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
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T0 status 3W.H.Trzaska HIP Jyväskylä
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.
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T0 status 4W.H.Trzaska HIP Jyväskylä
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
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T0 status 5W.H.Trzaska HIP Jyväskylä
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
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T0 status 6W.H.Trzaska HIP Jyväskylä
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
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T0 status 7W.H.Trzaska HIP Jyväskylä
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
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T0 status 8W.H.Trzaska HIP Jyväskylä
Cable layout & length
Too far out!
Accessibility of the shoeboxes!
T0-Right
shoebox
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T0 status 9W.H.Trzaska HIP Jyväskylä
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:
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T0 status 10W.H.Trzaska HIP Jyväskylä
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
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T0 status 11W.H.Trzaska HIP Jyväskylä
T0 + TRD Combined shoebox
preliminary
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T0 status 12W.H.Trzaska HIP Jyväskylä
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?
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T0 status 13W.H.Trzaska HIP Jyväskylä
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
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T0 status 14W.H.Trzaska HIP Jyväskylä
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
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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
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T0 status 16W.H.Trzaska HIP Jyväskylä
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)
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T0 status 17W.H.Trzaska HIP Jyväskylä
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
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T0 status 18W.H.Trzaska HIP Jyväskylä
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
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T0 status 19W.H.Trzaska HIP Jyväskylä
We could not test in the full dynamic range!
T0 time resolution (with PS particles)
• TOF FWHM=124 ps
= 37 psMeasuredTOF
spectrum
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T0 status 20W.H.Trzaska HIP Jyväskylä
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