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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 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 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 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 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 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