The ZEUS Micro Vertex Detector Roberto Carlin INFN – University of Padova for the ZEUS MVD Group...
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Transcript of The ZEUS Micro Vertex Detector Roberto Carlin INFN – University of Padova for the ZEUS MVD Group...
The The ZEUSZEUS Micro Vertex Detector Micro Vertex Detector
Roberto CarlinINFN – University of
Padovafor the ZEUS MVD Group
Vertex 2002 WorkshopKailua-Kona, Hawaii4-8 November 2002
ZEUS MVD Group: Bonn Univ., DESY-Hamburg, DESY-Zeuthen, Hamburg Univ., KEK-Japan, NIKHEF, Oxford Univ., Padova, Torino, Bologna, Firenze Univ. and INFN, UCL.
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Outlook:
• The structure of Zeus MVD
• Status of MVD, dead channels and some reason for that
• Cosmic rays runs and alignment
• Backgrounds, noise in the detector
• First measurements with e-p events
• Irradiation of MVD and how to cope with it
This is what we were expecting last year, but things went differently:• Hera startup difficult with very high
radiation backgrounds• A short lumi run is starting in November, we
will need a 3 months shutdown (spring ?) to get things really under control
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
• Readout with analogue chip (HELIX3.0, Heidelberg+Nikhef) built with AMS 0.8 CMOS technology
• Only preamp, analog pipeline and drivers on chip
• LVDS Clock and Control drivers 6m far on special patch boxes
• ADCs 30m far on the MVD racks !• Special care on cabling, signal
handling, grounding, shielding…
120 m
Si detectors and FE readoutSi detectors and FE readout• n-doped silicon wafers (300 m
thickness) with p+ implantations (12 or 14 m wide), HAMAMATSU PH. K.K.
• 512 readout AC coupled channels in the barrel, 480 in the wheels
• Using the capacitive charge sharing, the analogue readout of one strip every 6 allows a good resolution (<20 m) despite the readout pitch of 120 m
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
•Five modules are mounted on a carbon fiber support structure to form a ladder.
•The Si planes, Hybrids and Cabling are located on the 3 planes of the ladder
•30 ladders, in 3 planes, are positioned around the elliptical beam pipe in the MVD barrel detector
Modules in the BARRELModules in the BARREL
•Two single side sensors are glued and bonded to gold strips plated on Upilex flex foils, and finally to a FE hybrid
•Two planes are glued together to form a module with x-y readout
64 mm
125 mm
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
•The forward wheels have detector differently shaped (trapezoidal with two different sizes to accommodate the beam pipe)
•Two layers of single side Si detectors, same pitch and construction as in the barrel, strips cross at an angle of 26°
•Same electronics and connectivity as in the barrel
And in the forward WHEELSAnd in the forward WHEELS
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
The forward section:The forward section:• 4 wheels 4 wheels • each one composed by each one composed by
2 layers of 14 Si 2 layers of 14 Si detectorsdetectors
• Total of 112 hybrids, Total of 112 hybrids, >50k channels >50k channels
The barrel section:The barrel section:• 30 ladders 30 ladders • each one composed of 5 each one composed of 5
modules of 4 Si modules of 4 Si detectorsdetectors
• Total of 300 hybrids, Total of 300 hybrids, >150k channels >150k channels
The read section:The read section:• Cooling pipes and Cooling pipes and
manifolds manifolds • Distribution of FE, slow Distribution of FE, slow
control and alignment control and alignment cablescables
Overall structure and inventoryOverall structure and inventory
One half of the entire MVDAll cables in a Faraday All cables in a Faraday
cagecage
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Old Dead Old Dead ModulesModules ““Fixed” Fixed” Modules Modules (optimizing (optimizing HELIX HELIX programprogrammming):ing): Modules noisy Modules noisy sometimes or sometimes or partially (to be partially (to be investigated)investigated) New “Noisy” New “Noisy” ModulesModules
Status of the MVD: limited number Status of the MVD: limited number of bad channels in the barrelof bad channels in the barrel
Noise in ADC counts for each strip in the barrel(one histogram per ladder)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Characteristic noise structure:• In the wheels the strips have
different lengths • Different input C to the FE
chips, different noise
No problematic module in the wheels. Why?
• Factor 3 less channels
• In the barrel there may be one problem in the cabling
details
And much less in the wheelsAnd much less in the wheels
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Ladder cablingLadder cabling
Si planes
Hybrids
Cables
Very tight cabling
Use one side of the ladder for cabling
Use special, very thin custom cables
Minimize use of components and connectors
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Connect the hybrids via flex circuits on miniature ZIF connectors
Connectors to daisy chain the hybrids
Connectors to provide LV, HV, control signals and extract analog output
Termination resistors and filter capacitors
500 m pitch flex connection, pre-bent
Special custom multifunction (“combo”) cable
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Flex layer with stiffening to match the ZIF connector
G10 circuit layers glue
Vias between circuits and to soldering pads
Many more problems than expected:
• Very hard to cut the flex PCB with enough precision (50 m) to fit the 4 ZIFs in the 2 hybrids. Relative positions were important!
• Not easy to get the circuit of the proper thickness for the ZIF insertion (300 m)
• The conductors in the vias do not adhere to the glue, it makes a bridge between the layers (point of fragility)
• The glue is hygroscopic !• When soldering close to vias, the T increase
may create vapor that break the conductor in the via (and in extreme cases delaminate the connector)
Solutions: • Slow drying of PCBs in oven, and then store in vacuum bags
• Controlled soldering operation
• Extensive test of PCBs and of cabling at the company
• Test with (relatively) high currents at the lab
Nevertheless, some of the dead module show bad connectivity at the PCB
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
On the wheels there is more space for
cabling
• Standard PCB to connect cables and put components
• Bridge between PCB and hybrids with flex jumpers, ZIFs on both sides
• Installation at the end turned out to be “easy”
• No connectivity problem so far on the wheels
• NB extra ZIFs would not have fit in the barrel
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
MVD is working fine, test MVD is working fine, test tracking with cosmicstracking with cosmics
• Use the two semi-tracks as they were independent, to measure the resolution in impact parameter
• 117 um resolution, without alignment (p<1Gev tracks)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
• Alignment code is being developed and was tested on a sample of cosmics
• The results show that the module positions in each ladder are well known
•Very precise construction, markers aligned under microscope (10um)
•Very rigid ladder structure
• First iteration will need only ladder alignment (factor 5 reduction in free parameters)
• Need lot of good tracks (400K), corresponds to 2pb-1, feasible in the coming winter run despite of the bad background conditions
• A laser alignment system is present and will monitor overall rigidity
First alignments with cosmicsFirst alignments with cosmics
Alignment of each module
Module are fixed in the ladder, ladders only are aligned
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
High detector occupancy with bad
background data
Question:• Is it all background, or is there a
contribution from noise?• Do we have any pick-up, coherent
noise?
Occupancy from e-p (DIS) events
Data taken is dominated by Data taken is dominated by backgroundbackground
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Clustering (performed by the ADC)•A threshold is applied to each strip
• Independent for each strip, usually set to 3 noise•A cluster is a set of consecutive strips above threshold (a single hole is allowed)
•The two “side strips” are part of the cluster•A further cluster sum threshold can be applied
•The cluster size on pedestal events is consistent with a stochastic distribution of noise in the strips
Detailed studies of noiseDetailed studies of noise
•The noise hit distribution is consistent with a stochastic 3 noise in the strips
• A noise cluster is composed by 3 strips (one above threshold)
• The number of noise hits should be 0.15% per channel per event if the threshold is set to 3 noise
• Thresholds are a little lower than 3 (truncation to integer ADC counts)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Good events are clearly seen in the Good events are clearly seen in the MVDMVD
Cluster sums show clear Landau distribution• On average a little smaller than
in the system test with cosmics•S/N 14 instead of 16
• Likely reason: sampling a little off-time (signal rise time<40ns)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
dE/dx looks OK
Using the cluster charge, corrected for path length in Si, we get a nice dE/dx distribution from good e-p events
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
We got some irradiation, but we We got some irradiation, but we monitor it properlymonitor it properly
• 16 Si PIN diodes (8 modules) with DC (current) readout to generate alarms and beam dumps (and tune beams)
• Integrating currents:• No threshold for any
background (Synchrotron light)• Need treatment of leakage
current• Use an “leaky bucket” logic (a la
Babar) to dump beams• Plan to use empty bunches to measure
the leakage currents (1.2 s available)
• 8 radfets to have a continuous monitor of the integrated dose
• Readout every 15 minutes• Very valuable to assess the overall
quality of HERA operations
• TLDs exchanged monthly to cross-check the results from radfets
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
• Results from rear RADFETS in the last months of operations
• One module is at 80 Krad. This is located close to a collimator and sees the showers from low momentum leptons hitting it
• The other (also in the forward) measure doses within 20 Krad
• Doses in MVD between 20 and 80 Krad, in the most affected areas (inner layer, inside HERA ring)
Total dose received ?Total dose received ?
• MVD irradiation mostly with chips OFF
• Beam losses at injection or ramp-up (mostly e beam)
• Bad e-beam injection• Sensitivity reduced a factor 2
or more• Only marginally from normal
operations (but currents were limited so far)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Radiation Tolerance of Radiation Tolerance of MVDMVD • The most sensitive component is
the HELIX chip• AMS 0.8 CMOS technology• Designed to be radiation
tolerant• Tested by Heidelberg (for Hera-
B) and by Nikhef (for ZEUS)• Fast decrease of S/N ratio for
the first 100 Krad• Change of shaping time and
other parameters• Helix has programmable
parameters (internal DACs) to recover the working points
• 5 Krad/yr expected from beam operations (up to 100 Krad inside on bending plane, low p leptons)
• ZEUS has set a maximum radiation budget of 300Krad in the lifetime of the detector
S/N ratio measured with chips connected to a single Si detector (input C= ½ w.r.t the actual barrel readout)
Noise increase measured at Heidelberg with 0 input C
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Stability of the HELIX working pointStability of the HELIX working point
• Study of signal shape using HELIX internal test pulse (time scans)
• No evidence of gain variations with time
• No evidence of peak time changes
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Stability of the HELIX working pointStability of the HELIX working point
• Only sign of irradiation in the chips
• Limited increase in the noise for the inner layer of the BARREL (1.5%)
Day of the year
Nois
e (
AD
C c
ounts
)
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
How to recover the working pointHow to recover the working point
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
• Change of gain with Ipre, for diffrerent irradiations
• Signal decreases• Can be recovered, at least
partially, with a higher Ipre current
• There is space in the cooling and LV power supplies for extra power to the chips
• Change of peak time• Signal becomes faster with
irradiation• Increase of Ipre make it
even faster• Need to recover with shaping
time
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
• Changes with Vfs• Peak time can be
recovered• At the same time
also the S/N recovers
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
SummarySummary
• MVD commissioning limited by backgrounds in HERA
• Number of non-working channels small after one year from the
beam startup
• The noise distributions are under control
• Data from cosmics and first events look promising, tuning
needed
• Alignment underway, need much more data. The detector is well
measured and rigid
• 20-80 Krad collected, but so far no clear evidence of damage
• “Luminosity run foreseen November ...”
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R.Carlin: Status of the ZEUS Micro Vertex DetectorR.Carlin: Status of the ZEUS Micro Vertex DetectorVertex 2002 – Kona, HawaiiVertex 2002 – Kona, Hawaii
Detailed studies of noisenoise (2)
•Side strips must be sampling a noise distribution on a random noise hit
• Again, no coherent noise or cross-talk
Thresold cut
•On BG (or physics events) they must carry some induced charge information
• OK, included in the cluster