The ZEUS Micro-Vertex Detector

1
The ZEUS Micro-Vertex Detector
Alessandro Polini DESY
2
Outline
200
180
160
140
14C (bias 51V)
120
Current(nA)
17C(bias 48V)
100
20C(bias51V)
80
23C(bias78V)
60
23C(bias65V)
40
30C(bias65V)
20
0
0
20
40
60
80
100
Voltage(V)

• Physics Motivation
• Detector Design
• Standalone Test Measurements
• Read-Out, DAQ and Control Infrastructure
• First Experience after Installation in ZEUS
• Summary and Outlook

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A Microvertex for ZEUS at HERA

• ZEUS
• upgrade of tracking system
• MVD
• Straw Tube Tracker
• Global Tracking Trigger
• Tagging of long-lived particles (heavy flavour)
• Reconstruction of secondary vertices

• HERA
• e p collider
• 2001 luminosity upgrade
• L 1.5 7.5?1031cm-2s-1
• higher sensitivity for very interesting, low
  cross sections
• major changes in interaction region
• last bending magnet inside experiment
• higher backgrounds, risks of radiation damage

4
Detector Layout
Forward Section 410 mm
Barrel Section 622 mm
e
p
The forward section consists of 4 wheels
with 28 wedged sensors/layer providing
r-? information.
The Barrel section provides 3 layers of support
frames (ladders) which hold 5 full modules, 600
square sensors in total, providing r-? and r-z
space points.
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Barrel MVD Module and Ladder Structure
Two single sensors are glued and electrically
connected by gold plated Upilex foils
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Forward MVD Layout

• Forward wheels
• 112 Si planes with wedge shape (480 readout
  strips)
• r-? measurement
• 1 wheel made of 14x2 detectors
• 4 wheels placed _at_ z 311, 441, 571 and 721 mm
  from IP.

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Silicon Microstrip Detectors

• n-doped silicon wafers (300 mm thickness) with p
  implantations (12 or 14 mm wide), HAMAMATSU PH.
  K.K.
• 512 (480 for forward sensors) readout channels.
• Using the capacitive charge sharing, the
  analogue readout of one strip every 6 allows a
  good resolution (lt20 mm) despite the readout
  pitch of 120 mm.
• Highest coupling to the front end electronics if
  

Cc gtgt Cint gt Cb
The charge sharing is a non linear function of
the interstrip coordinate x
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Front-end and Read-out

• Front-end Chip HELIX 3.0
• 128 channel analog pipelined programmable readout
  system specifically developed for the HERA
  environment.
• ENCe ? 400 40CpF (no radiation damage
  included).
• Data read-out and multiplexed over the analog
  out.
• Internal Test Pulse and Failsafe Token Ring (8
  chips) capability.
• Read-out
• 10 bit resolution ADC Modules with
• Common Mode, Pedestal and Noise Subtraction
• Strip Clustering
• ? 2 separate data buffers cluster data (for
  trigger purposes) and raw/strip data for
  accepted events.
• Global Tracking Trigger
• Together with the Central Tracking Detector new
  Global Tracking Trigger System.

1 full module raw data
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Hit Reconstruction from previous Test Beam
Results
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The MVD System Test

• Following the assembly up to the final MVD,
  extensive tests and monitoring of the detector
  have been performed.
• A Standalone Test Environment with a dedicated
  Cosmic Trigger has been set up.

Aim
Large cosmic sample acquired 2.5 Million
triggered events.

• Final checks of modules, cabling, cooling
• Laser alignment measurements
• Setup a complete read-out scheme
• Study detector response with real data
• Monitoring of various system components
• Cooling, Temperature, Humidity, LV,
• HV, Noise, Pedestals ,Dark Current.

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MVD Cosmic System Test

• Landau distributions from different ladders

• C0L1 (?0º)

• C1L1 (?50º)

S/N ? 13

• The expected difference in the peak position is
  clearly seen!

C1L1

• Noise and Stability

• Pedestal stable at the level of 1-2 ADC-counts
• Entries above 20 ADC-counts in noise-distribution
  36 /25 (barrel/forward)
• Channels with unstable noise-performance 119
  (total for barrel and forward)

C0L1
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MVD Cosmic System Test Results
? 80 ?m
Without any alignment correction
First Track fit using all modules but one
resolution ? 80 ?m Dominated by systematics,
confident to reach final resolution of ? 20 ?m
Geometrical efficiency
Cyl. 0
Cyl. 1
Cyl. 2
Faulty Modules (4 of 206)
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Detector I/V Observed Properties
During the system test increasing leakage
currents have been observed in some modules.
Further studies have shown that at decreasing
temperature the relative humidity rises and the
breakdown voltage decreases
A careful checking and control of the humidity
is required for the ZEUS MVD!
22.5 31h.
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MVD Commissioning in ZEUS

• ZEUS Requirements
• DAQ System and Global Tracking Trigger
• Radiation Monitor
• First (Cosmic) ZEUS data

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The ZEUS Detector
107 Hz
CTD Front End
CAL Front End
Other Components
CAL FLT
CTD FLT
p
5?s pipeline
5?s pipeline
Global First Level Trigger
0.7 ?s
920 GeV
GFLT Accept/Reject
500Hz
e
Other Components
CTD SLT
CAL SLT
Event Buffers
10 ms
Event Buffers
27.5 GeV
Global Second Level Trigger
GSLT Accept/Reject
40Hz
CAL
CTD
Event Builder
Third Level Trigger
bunch crossing time 96 ns
cpu
cpu
cpu
cpu
cpu
cpu
ZEUS 3-Level Trigger System (Rate ?500Hz?40?5 Hz)
5Hz
Offline Tape
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The MVD Data Acquisition System and GTT
Central Tracking Detector Read-out
Analog Data
MVD HELIX Front-End Patch-Boxes
MVD VME Readout
Global First Level Trigger,Busy, Error
AnalogLinks
AnalogLinks
AnalogLinks
NIM Latency
NIM Latency
NIM Latency
NIM Latency
Clock Control
Clock Control
Clock Control
Lynx OS CPU
Lynx OS CPU
Lynx OS CPU
CTD 2TP modules
Lynx OS CPU
ADCM modules
ADCM modules
ADCM modules
Lynx OS CPU
VME (CC Slave) Crate 1 (MVD bottom)
VME (CC Slave) Crate 2 (MVD forward)
VME (CC Master) Crate 0 (MVD top)
VME TP connection Data from CTD
VME HELIX Driver Crate
NIM Latency
Lynx OS CPU
GSLT 2TP modules
Global Tracking Trigger
Processors (GFLT rate 800 Hz)
Global Second Level Trigger Decision
TP connection to Global Second Level Trigger
Run Control and Online Monitoring Environment
Fast Ethernet/ Gigabit Network
NIM Latency
Lynx OS CPU
Slow control Latency Clock modules
VME CPU Boot Server and Control
Network Connection to the ZEUS Event Builder
(100 Hz)
Main MVDDAQ server, Local Control, Event-Builder
Interface
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The Global Tracking Trigger

• Concept
• Combined second level trigger using information
  from CTD, MVD (and the new Forward Tracker)
• Higher quality event reconstruction and rate
  reduction
• Z vertex resolution 9 cm (CTD only) ? 400 ?m
  (MVDCTDGTT)
• Decision required within existing SLT (lt15 ms)

Dijet sample
Input rate 400Hz
Full online latency measurements and data
file playback capability. First average
latencies obtained using MonteCarlo events
through complete DAQ system and trigger algorithm
are encouraging.
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The ZEUS Radiation Monitor System

• 16 PIN diodes in 8 modules ( 1cm2, zfwd110,
  zrear-100 cm)
• continuous radiation measurement, beam dump
• 8 RADFET (zfwd200, zrear-160 cm)
• real-time integrating dosimeter
• wide dynamic range 1 mGy to 3kGy
• Thermo-luminescence dosimeters (TLD)
• two types (neutron, photon sensitive)
• measure precisely integrated dose (monthly
  exchanged)

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Radiation Monitoring
During machine setup
PIN diode current
Increase of plateau current

• 50 Gy absorbed so far (diode measurements,
  confirmed by
  Radfets TLDs)
• Final diode readout with beam dump capability
  being
  finalized (automatic beam dump at
  integrated dose of
  10..50 mGy per accident).
• Expected background irradiation in 5 years of
  operation (experiment lifetime) 50
  Gy/year 5 µGy/s
• MVD and readout electronics tested up to 3 kGy,
  operation still possible, but
  reduction of S/N
• Max. tolerable dose 100-300 Gy/year 10-30 µGy/s

MVD Leakage Current increased 1?A
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ZEUS Cosmic Data with CTD and MVD
Before HERA commissioning started (July 2001),
there was a short time window for a cosmic data
run with the full ZEUS detector.
A Cosmic Event based on a CTD and Calorimeter
Trigger.
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Summary and Outlook

• System Test
• Complete MVD-system has been tested continuously
  for a longer period.
• Stable operation of Slow Control, Cooling, LV
  and HV Systems.
• Dark currents are fairly stable in time at depl.
  voltage (? dry air flow is important!)
• Pedestal and noise performance is good. Faulty
  modules lt2.
• Cosmic results show expected performance (Landau
  distributions, etc.).
• Installation and Commissioning in ZEUS
• MVD installation was successful (detector
  integration, cable routing).
• Functioning of the DAQ System, the GTT
  environment as well as the Control infrastructure
  established.
• Radiation monitoring (active and passive system)
  available and working during HERA startup.
• Encouraging results looking at the next high
  luminosity period.