MBD Mickey Chiu MBD Group BNL MC M Lenz R Pisani RIKEN Yuji Goto ColumbiaNevis CY Chi B Sippach Lehigh U Rosi Reed PHENIX BBC in sPHENIX Higher Magnetic Fields ID: 792819
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Slide1
WBS 1.7:
sPHENIX Minimum Bias Detector (MBD)
Mickey Chiu
Slide2MBD Group
BNL: MC, M. Lenz, R. PisaniRIKEN: Yuji GotoColumbia/Nevis: C.Y. Chi, B. Sippach
Lehigh U:
Rosi
Reed
Slide3PHENIX BBC in sPHENIX
Higher Magnetic FieldsGain drop with higher B-fieldMaintain good MB eff even when placed out further in zUpdate of ElectronicsMaintain Single PMT time resolution dt ~ 50 ps
in offline, and 120
ps
in the trigger
.
Provide clean min-bias triggering w/ vertex selection (+/- 10 cm)
Provide Centrality determination
Provide Start-timeProvide Reaction Plane
Challenges in
sPHENIX
Slide4Placement in sPHENIX
Considering z = 144, 200, 250, and 300 cm, ie
, from original PHENIX location to near flux return
z
(cm)
η
min
η
max
B
Z
(T)
Rel. Gain
AuAu
MB
Eff
(%)
pp
MB
Eff
(%)
144
3.0
3.9
1.110.0190392003.334.230.750.1589362503.564.450.500.588343003.744.630.320.98732
Slide5B-field Study
5
Study of PMT Gain vs (Field
S
trength, Angle, PMT HV)
w/ Paul
Gianotti
,
Camillia FayyaziField Strength: Up to 0.735 T but in old documentation it says safer to stop at 0.4 TEventually stopped at 0.5 TField orientation at proposed locations of BBC range from 2-5 degreesRan at 0 and 5 degreesPiLas Laser
Magnet region
DRS4
Readout
Hall
Proble
Slide6B-field Study Results
BBC in PHENIX runs at 30 (inner) or 40 (outer) pC/MIPNeed MIP peak to calibrate gain
Need to confirm expected max particles in a tube (was ~30 in PHENIX) to get required dynamic range
Single particle peak
PHENIX@144 cm
sPHENIX@300 cm
Eff -3%
AuAu
, -7% pp
sPHENIX@250 cm
Eff -2%
AuAu
, -5% pp
PHENIX
AuAu
200 GeV
Slide77
Readout Design
sPHENIX
GTM
sPHENIX
DAQ
sPHENIX
BBC LL1
sPHENIXGL1
L1 Trig,
Modebits
, CLK
Use
sPHENIX
EMCAL digitizers, and build a transition board to convert single-ended PMT signal to 100 ohm differential that stretches PMT signal to be recorded by 60 MHz ADC
Two possibilities to satisfy the trigger and timing requirements. Both options require splitting the signal. One is a shaped pulse for energy measurement. The other
is a square ~1V discriminator signal (for timing at trigger level and
precisiong
timing in offline).
o
r is a ramp and hold on a comparator (TAC) that is input to the digitizer
sPHENIX
Digitizers (2 or 4 ADC boards)
Disc/
Shaper
BoardBBCPMTsIn WBS 1.5 + 1.6 ScopeIn WBS 1.7 ScopeL1 FEM Board
Slide8PMT Resolution Study
8
Used 20
ps
piLAS
laser studies going well
Got 43
ps time resolution for 33 p.e. at lower than nominal gainLaser
BBC
Slide9Testing sPHENIX Digitizer Timing
NEW ADC
Input a signal from Agilent generator, that is passively split, and look at time difference between the two “identical” signals from the NEW ADCs to determine the timing resolution of the NEW ADCs.
Signal generated is shown on the right, and is intended to get close to matching what will be generated by the new disc/shaper board.
We need to know the final shape to use!
Shape tested was only ~2 samples during rise to check if this would be good enough
Slide10sPHENIX
Digitizers Timing Res (Fall 2017)12/19/17
10
We created signal shape templates and did a full chi-2 minimization (MINUIT) fit to get the start time for each of the two pulses from the split cable
This can only be done in offline, and is the best possible resolution one could ever get
For the resolution at L1, the resolution depends on the algorithm and still needs to be studied
We put the two split (identical) signals into the same board and also into different ADC boards so that we could see if there was a contribution from the clock propagation
Getting sub 1
ps from same ADC board, and ~13 ps (= 18.6/√2) from different boards. Clock propagation jitter at 13 ps level?Some anomalous systematic timing difference (at Δt = 0.01 ns) in some events that needs to be studied
Same Board
Different ADC Boards
Anomalous times?
Slide11TDC ADC
Contributions to Timing ResolutionNB: Contribution to trigger resolution depends on algorithm to extract time
sPHENIX
Digitizer
DAQ
Discriminator
Shaper
D/S Board
L1 FEM
Board
LL1
Board
+
+
=
43
ps
?
13
ps
Slide12Simple
dCFDUsing simple digital Constant Fraction Disc algorithm (Leading Edge with linear interpolation and threshold set at 50% of pulse height), we can get ~75 ps
resolution using a DRS4 Evaluation Board
Easily implemented in FPGA for L1 trigger
More complicated algorithms (FIR with sliding windows)
contemplated
This is with DRS4. Will need to reconfirm with final electronics chain
Slide13clip
delay
Test pulse
gate
disc
Test pulse
Charge
injector
threshold
gated
TVC pulse
shaper
shaper
splitter
3 poles
20ns (each)
shaper
disc
gated
pulse
shaper
splitter
shaper
Test pulse
Charge
injectorthresholdCalorimeter 64 channel 60 MHZ ADCgatediscTVC pulse3 poles 20ns (each)shaperPMTPMTOne threshold DAC per channelOne TP Charge injector DAC per board Even/odd channel enable for TP8 PMT channel per board128 channel, 16 boards totalBeam clock2mm HM cable2mm HM cableNew Beam Beam electronics Block DiagramL1 Trigger primitive
L1 Trigger Event
The TVC
shaped
pulse will have multiple samples from 60 MHZ ADC
CY
Chi, W.
Sippach
Slide14Conclusions
Studies to confirm use of BBC in sPHENIX going wellLoss of only 3% in AuAu MB Eff, ~15% in p+pZeroing in on z = 250 cm (closer-in option) as the preferred placement of BBC.
MB
Eff better (particularly for
p+p
) and gain drop can be counteracted by HV increase of just 100 V.
Moving toward full electronics chain
Nevis to produce prototype disc/shaper board next year
Slide15Backup Slides
Slide16Pseudorapidity Coverage
Multiplicity doesn’t drop too quickly with pseudorapidityBut how well can PMTs survive in B-fields?
z
(cm)
η
min
η
maxBZ (T)144
3.0
3.9
1.11
200
3.33
4.23
0.75
250
3.56
4.45
0.50
300
3.74
4.63
0.32
PHOBOS
PHOBOS
Slide17MBD Eff for 200 GeV
Au+Au and p+pThe Au+Au MB efficiency doesn’t drop much when moving the BBC back (according to pure Hijing
)
A little worse in
p+p
(as a percentage), goes from 39% to 32%
p+p
efficiency matters mostly for effect on cleaning up central arm triggers, but for high pt it’s not needed or wantedNot too relevant for relative luminosityThe purely MB triggered events are mostly uninteresting events anyway
Au+Aup+p
Slide18MB Efficiency Loss in
Au+AuRan 10K Hijing events (100K PYTHIA6 events), and selected coincidence events, >1 tubes on each side (>0 tubes on each side
)
All efficiency loss is in just the peripheral collisions, as expected, where there are only a few participants
You wouldn’t a large MB efficiency loss since the extreme peripheral is just a few % of the collisions
All
Hijing
BBC@144 cmBBC@200 cmBBC@250 cmBBC@300 cm
Slide19Properties of BBC Mesh Dynode PMTs
BBC used Hamamatsu R6178, similar to R5505. (R6178 discontinued and I couldn’t find the datasheets)In PHENIX, we ran BBC in ~0.2-0.3 T field, where gain drops 20% from 0-field runningThere’s possibly some room to compensate for lost gain in higher field in sPHENIX by increasing HVOne could possibly run at low gain in high B-field, but then compensate with CMOS amplifier (x100). Only concern would be if timing resolution can still be as good.
Slide20Field in sPHENIX
At flux return (z=300 cm), gain drops only by 10% from PHENIX (70%)At z=250, gain drops to ~50%Can compensate by increasing HV by ~100-200 VAt z=200, gain drops to 15%.HV increase probably not tenable (if we want to maintain safe running conditions)Could use CMOS amplifier. “Easy” to get gain of 8 without sacrificing signal quality
.
Fields angles are small, from 1-4 degrees (right figure)
@ r=10 cm
B
Z
B
R