Transcript Front Tracker Progress

SBS Spectrometer / GEP5 Conf.
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Tracking Requirements
Requirements
High Rate: 0.55+0.17 MHz/cm2
(Front Tracker)
High Resolution: <100 mm
(Front Tracker)
Large Area: 100 x 200 cm2
(Polarimeter Tracker)
Tracking Technology
Drift
NO
MPGD
Silicon
MHz/mm2 MHz/mm2
Achievable
50 mm
30 mm
YES
Doable
Very
Expensive
… and modular: reuse in different geometrical configuration
MPGD = Micro Pattern Gas Detector (GEM, Micromegas …)
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GEM for SBS
Proposed Layout for SBS:
• Several chamber modules of
40x50 cm2 each
• Standard 3 GEM foils
• 2D Readout plane, 0.4 mm pitch
• Last GEM HV layer segmented
and read-out (0.5 mm pitch)
Gain ~ 20^3 = 8000
• Approx. 70000 channels
2D Readout perpendicular (x,y) and/or +/- 30 degree (u,v) ?
Second is certainly more demanding for the extraction of
the strips
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SBS Front Tracker Project
few months delay
BA: Gas system + Electronics (FE chips)
CA: Mechanics + Test + MC + Slow Control
GE: Electronics
ISS/ROME: Prototyping, Test, Digitization + Reconstruction,
Evaluate Si, Coordination
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Prototyping
• 3 10x10 cm2 chambers (one under test)
• Working on 40x50 cm2 module, with minimum
dead area in the frame (minimum frame
thickness); main practical issues:
– Each GEM foil has two HVs (one on each GEM side).
Each GEM side must be segmented in order to
suppress discharge spreading; each segment is
connected to the HV power supply by a protection
resistor
– Gas in/out-lets in tiny frames (2-3 mm thickness)
– Thousands readout strip extraction
– Front-End electronics position and anchor
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GEM HV sectors and resistors
GEM requires 10x10 cm2
sectors for HV distribution
Use surface mounted HV
resistors
Distribute HV from two sides
Gluing GEM foil on the frame
may be a problem practical
test in preparation!
Red and Green are the 2 HV levels serving one GEM foils
Resistors will be placed on the two sides
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Electronics Front-End at 90°
Electronics will be placed at 90° respect to the readout plane on 2 side of
the frame. Some holes (bottom-left) will permit the passage (and
protection) of the flat on the readout side. The width of the frame shall
be as small as possible (working on 5 mm).
• Connector type is a constraint
in possible 90° configurations
• +/-30° strips extraction an
unsolved problem!
Flex close to 90° bending, protected by the frame
2x2 chamber configuration
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Clean Room Tools and Facilities
HV single foil testing station
Visual inspection back-light board
Facilities available in clean room:
• Visual Inspection
• HV test
• Foil Cleaning
• Stretching, gluing and heating
Assembling the GEM chambers parts require a careful quality controlled
procedure:
inspecting  cleaning  testing(0)  stretching  gluing  heating  testing(1)
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Real Prototype 0
• First 10x10 prototype
under cosmic test
• Using 70/30 Ar/CO2
gas mixture
• 7 Independent HV
levels up to about
4200 V
Using temporary “Genova” electronics
(PESA + ALTRO) from ALICE
Bought about 620 APV25 analog chips for
the final electronics (about 80000 channels)
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HV Slow Control
Use 7 HV independent
levels to study the
chamber performance
HV management
is not trivial!
Keep noise at
adequate level:
use low pass
filters on HV lines
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“fake” prototype
Testing solutions and
alternatives on
a fake 40x50 cm2 GEM
chamber with
asymmetric frame (5
mm one 2 L sides, 5 cm
on the opposite L sides).
• Gain experience on kapton gluing
• Test mechanics
• Optimize position of the resistors, gas pipes, readout fanout
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Mechanical Analysis in progress
• Assumptions:
– 50 kV/cm felectrostatic field
– GEM foil made of Kapton:
•
•
•
•
Young module: 5.38*109 N/m2
Poisson module 0.32
Shear module 0.35*109 N/m2
Density1.4 g/cm3
– Fram in STESALITE
• Young module 244*109 N/m2
• Poisson module 0.29
• Shear module (evaluated by the softwarE)
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FEM of single GEM foil
• STESALITE frame of 40x50 cm2, 5 mm
width, 2 mm thick
Deformation well below tolerance (5% of 2 mm)
Limiting frame widths seems to be the HV paths, resistors and readout
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Planned activities for the next few months
• Finalize the cosmic tests to characterize the prototyped
telescope
•
Finalize the design of the 40x50 GEM foil and readout,
then order them
• Development of the electronics (Genova), based on
COMPASS
• First July we have to apply for the 2010 INFN funding.
It is fundamental to have a “reasonable” view of the
future of the SBS project
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