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SBS Spectrometer / GEP5 Conf.

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Tracking Requirements

RequirementsTracking Technology

Drift MPGD Silicon

High Rate: 0.55+0.17 MHz/cm2

(Front Tracker)NO MHz/mm2 MHz/mm2

High Resolution: <100 m (Front Tracker)

Achievable 50 m 30 m

Large Area: 100 x 200 cm2

(Polarimeter Tracker)YES Doable Very

Expensive

MPGD = Micro Pattern Gas Detector (GEM, Micromegas …)

… and modular: reuse in different geometrical configuration

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GEM for SBS

Gain ~ 20^3 = 8000

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)

• 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

BA: Gas system + Electronics (FE chips)CA: Mechanics + Test + MC + Slow ControlGE: ElectronicsISS/ROME: Prototyping, Test, Digitization + Reconstruction,

Evaluate Si, Coordination

few months delay

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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 resistorsGEM 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 foilsResistors 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).

Flex close to 90° bending, protected by the frame 2x2 chamber configuration

• Connector type is a constraint in possible 90° configurations

• +/-30° strips extraction an unsolved problem!

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Clean Room Tools and FacilitiesHV single foil testing station Visual inspection back-light board

Assembling the GEM chambers parts require a careful quality controlled procedure:

inspecting cleaning testing(0) stretching gluing heating testing(1)

Facilities available in clean room:• Visual Inspection• HV test • Foil Cleaning• Stretching, gluing and heating

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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 ALICEBought about 620 APV25 analog chips for the final electronics (about 80000 channels)

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HV Slow ControlUse 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” prototypeTesting solutions and alternatives ona 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 thickDeformation 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